Continental XO-1430 Development
Part 7: 1 Jan 1936 to 30 Jun 1936
by Kimble D. McCutcheon
Published 8 Sep 2025; Revised 19 Sep 2025

15 Jan 1936 Progress Report. No single-cylinder running was done during this period. Authority for further single-cylinder testing was received in a 6 Jan 1936 MatCmd letter. Bendix Products Corporation HT Spark Plug Division spark plugs used in prior tests were forwarded to Wright Field for examination. George Paulson of BG Corporation visited the Continental factory to discuss advance spark plugs for future use. The BG Corporation was founded in New York around 1918 by Charles Brewster, an engineer, and Arthur Goldsmith, a jeweler, to develop reliable aircraft spark plugs. The company pioneered the mica insulator design, heat transfer, and electrode configuration that made BG spark plugs immediately successful. Paul S. Lane, metallurgist for American Hammered Piston Ring Company met regarding the unsatisfactory ring batch for the 12-cylinder engine, and was to advise on the material in this batch at a later date.

Contract W-535-AC-8361 – Crankshaft and Associated Parts: Van Dykes for the single-cylinder test engine were completed and forwarded to Wright Field. Crankshaft and associated parts were retained at Continental in the single-cylinder test engine.

Tilley's Engine Mount Patent

The following items were completed and released by the Air Corps Inspector:
Contract W-535-AC-6322 Item #2 – Crankshaft
Contract W-535-AC-6322 Item #3 – Crankcase
Contract W-535-AC-6834 Item #1 – Reduction Gears
Contract W-535-AC-6334 Item #2 – Rear Accessory Housing Assembly
Contract W-535-AC-6334 Item #3 – Camshaft Housing Assembly. Five rocker arms required re-making. Forgings were promised for 23 Jan 1936 and associated parts were in work and promised for 26 January. ALCOA promised the mount plate assemblies on 10 February and final machining by Continental was planned for 15 February, which would complete this Item.

Contract W-535-AC-6334 Item #4 – Connecting Rod Assemblies: In work and promised for 10 February.

Contract W-535-AC-6334 Item #5 – Cylinder Assemblies: Replacement exhaust valves were promised for 17 January. Cylinder heads, jackets and barrels were to be assembled on 17 January and completely finished on 30 January.

Contract W-535-AC-6334 Item #6 – Piston, Assembly, etc. to complete engine: Piston completion was promised for 23 January. Radio shielding awaited engine assembly. The engine, minus cylinders, connecting rods, pistons and valve gear was assembled. The complete assembly was promised for 17 February.

12-Cylinder Tests – Contract W-535-AC-8131: The crankcase blower assembly was run-in for 2 hrs, coming up to 2,500 rpm. The drives were taken apart and longitudinal grooves added at the accessory drive bushings. The crankcase blower assembly was next run up to 3,000 rpm when the accessory drive shaft seized in the bushing at the reduction gear end. The reason for this failure was not immediately obvious. Six new SAE #64 bronze accessory drive shaft bushings replaced the SAE #62 bushings in the reduction gear case and front crankcase front ends. Provision was made for increasing the oil feed by grooving these bearings and locating flanges. This assembly with thermocouples at the bushing flanges that previously failed was expected to again run on 17 January.

Engineering: Routine drawing changes continued. Crankcase nose seal and torsiometer details were completed. Crankcase nose seals would permit blow-by observations during fully-assembled engine tests. Work on the complete stress analysis report had resumed. Wright Field had released the mounting plate drawings. [RG 342 RD1670 502-108 O-1430 350101-360219. 147 – 149.]

31 Jan 1936 Progress Report. No single-cylinder running was done during this period. Authority for further single-cylinder testing was received in a 6 Jan 1936 MatCmd letter.

The following items were completed and released by the Air Corps Inspector:
Contract W-535-AC-6334 Item #5 – Cylinder Assemblies.
Contract W-535-AC-6334 Item #3 – Camshaft Housing Assembly. The remaining rocker arms, rocker shafts, screws and pads were promised for the week ending 8 February. One mounting plate furnished by ALCOA on 10 February was outside the drawing limits, necessitating the selection of another plate, which delayed this Item's completion until early March 1936. Forged fittings for attachment to the airplane structure were in work with completion promised for 10 February.

Contract W-535-AC-6334 Item #4 – Connecting Rod Assemblies: These parts were in work with completion promised for 10 February.

Contract W-535-AC-6334 Item #6 – Piston, Assembly, etc. to Complete Engine: Pistons were completed and in inspection. Radio shielding assembly was sent to Breeze Corporation for preliminary assembly; completion was promised for 10 February. The complete engine assembly, minus mounting plates, was promised for 17 February.

12-Cylinder Tests – Contract W-535-AC-8131: The crankcase with new bushings and modifications to provide additional oil supply was run-in. Temperatures at the six accessory drive shaft, front crankcase and reduction gear housing bosses did not exceed 205°F. The propeller shaft was inspected at 1,000 and 1,500 rpm. Preliminary supercharger performance figures were obtained for a 1,500 rpm propeller speed representing the rated engine speed and 1,395 rpm representing the speed that would give the supercharger impeller speed with one less tooth in the last impeller drive gear:

12-Cylinder Engine Setup: The water brake was aligned with the electric dynamometer. Connecting arms for transferring torque reaction from the electric dynamometer to the water brake had been made. The engine sub-base had been set in place relative to the dynamometer. The oil weighing system and fuel system were being worked.

Contract W-535-AC-8355, P.O. 36-2895, Items 1 and 2, Cylinder and Piston Assemblies: All parts released for manufacture.
Item 3 – Valve Gear: Revised layouts were being made to permit parts detailing.

Engineering: Routine drawing changes continued. An itemized weight list had been made, giving a 1,210 lb total. The 1 May 1935 estimated weight was 1,164 lb, which means the new estimate was 46 lb over the earlier estimate, or 90 lb over the contract weight. Most of the overweight was caused by casting wall thicknesses being over drawing requirements. These castings were accepted to facilitate sample engine completion.

[RG 342 RD1670 502-108 O-1430 350101-360219. 151 – 154.]

30 Jan 1936 During a telephone conversation with Continental's Norman N. Tilley, Prescott asked for an estimate covering two addition airplane-type O-1430-1 mount plates, including the pair for Contract W-535-AC-6834. One mount-plate pair, which was dimensionally defective, was to be used exclusively on the wooden mockup engine; MatCmd believed it should receive a price concession on this part. The third mount-plate pair for the type-test engine did not need to be delivered prior to static test, part of Contract W-535-AC-6834. [RG 342 RD1670 502-108 O-1430 350101-360219. 155. 31 Jan 1936 Memorandum Report E-57-285-27, Confirmation of Telephone Conversation with Representative of Continental Aircraft Engine Company, 30 Jan 1936, on XO-1430-2 Engine Mount Plates.]

13-14 Feb 1936. Prescott and Capt E.R. Page's visited Continental where they inspected completed O-1430-1 parts; the engine was expected to be ready for testing around 17 February. Previous motoring tests without cylinders, pistons and connecting rods had demonstrated that the supercharger capacity was approximately correct. However, it was found that while the supercharger capacity WAS adequate for more than 1,000 hp using a carburetor, it was NOT with fuel injection, which did not cool the intake air. Continental's backup plan was to modify the diffuser and/or impeller to raise its capacity.

Continental reported that the engine mount plates were slightly more costly than anticipated, mainly because of the added stiffeners at the plate rear ends, as requested by MatCmd. There were also die costs included in the first few mounts; the price would drop when these were paid. Continental was submitting a new quotation covering two additional mount plate pairs for installation on the wooden engine mockup and for torque stand tests of the completed engine.

Continental requested a copy of the Air Corps ethylene glycol specification and stated that no Engineering Order had been received covering the use of 100 octane fuel on the 50-hr development test. Continental stated that the Shell Petroleum Company was unwilling to guarantee the octane number for 100 octane fuel for a period in excess of one month. Further, it would be necessary for Continental to procure a train car load of gasoline and store it underground for the duration of the development test, and since this might last six months and fuel deterioration might be serious, MatCmd should intervene with Shell. MatCmd agreed to attend to these requests.

The first engine was to have provisions for installing the MatCmd torsiometer and Continental wanted MatCmd to conduct these tests prior to the 50-hr development test. MatCmd agreed to send an engineer to witness the test using its torsiometer.

Prescott was encouraged by the engine development thus far. He called the design excellent, single-cylinder tests had been satisfactory and indicated a possible power reserve above the normal engine rating, and the fabricated parts indicated a high class of manufacture. A long and detailed test program lay ahead; as with any new engine development, failures were expected and would be corrected. Continental was enthusiastic and was expected to continue providing the necessary funds to complete the development. [RG 342 RD1670 502-108 O-1430 350101-360219. 156 – 157. 19 Feb 1936 Memorandum Report E-57-285-29, Visit of Captain E.R. Page and Mr. F.L. Prescott to the Continental Aircraft Engine Company, Detroit, Michigan, on 13 – 14 Feb 1936, in Connection with the O-1430-1 Engine.]

15 Feb 1936 Progress Report. The single-cylinder test engine was disassembled and inspected. The bolt that held the balance rod small end pin was cracked at the head. Both of these bolts were replaced. A new crankshaft bevel gear was installed after being altered to use a 1/2" instead of 3/8" screw to hold the assembly together. Four new ball bearings were placed in the radial drives from the crankshaft. The cylinder used in the last test was assembled with new American Hammered Piston Ring Company rings. Exhaust valves with a solid big end instead of the two-piece type sealed with stellite.

XO-1430-1 Engine Construction:
Contract W-535-AC-6334 Item #3 – Camshaft Housing Assembly:. All items except mounting plate assemblies were complete and accepted by the Air Corps Inspector. He forged fittings had been forwarded to ALCOA for assembly to the mounting plates. ALCOA promised to complete these by the end of February, after which there was about one week's work at Continental to complete machining.

Contract W-535-AC-6334 Item #6 – Piston, Assembly, etc. to Complete Engine: All parts were complete and accepted by the Air Corps Inspector except radio shielding, ignition assembly and final engine assembly. Preliminary assembly of the radio shielding was completed by the Breeze Corporation at the Continental Detroit, Michigan factory and were being made up in the permanent assembly at Newark, New Jersey. Breeze promised completion on 27 February. The complete engine assembly, minus mounting plates and radio shielding, was promised for 17 February.

12-Cylinder Tests – Contract W-535-AC-8131:

Supercharger Test – A report that was summarized in the last Progress Report had been prepared and submitted.
12-Cylinder Engine Setup – This task was practically complete except for plumbing work to complete coolant connections and engine fuel system.
Contract W-535-AC-8355 P.O. 36-2895 Items 1 and 2 – Cylinder and Piston Assemblies:. All parts had been released for manufacture. Jacket forgings were promised for 1 March. A sample cylinder head had been received, checked and corrections forwarded to ALCOA; a new sample would be rechecked prior to release. Barrel forgings had been machined and were ready for assembly. The next Progress Report will include a completion date.
Item 3 – Valve Gear: The layouts were complete and detail drawings were being made; all parts were to be released for manufacture on 26 February.
P.O. 36-3709 – Test Engine Connecting Rod: This order had been received and was being released to the factory.

Engineering: Routine drawing changes continued. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 1 – 3.]

XO-1430-1 Engine Construction:
Contract W-535-AC-6334 Item #6 – Piston, Assembly, etc. to Complete Engine was completed and accepted by the Air Corps Inspector.

Status of the above items will not be reported in future Progress Reports unless it changes.

Contract W-535-AC-6334 Item #3 – Camshaft Housing Assembly: All items except mounting plate assemblies have been completed and accepted by the Air Corps Inspector. The mounting plate assemblies were received from ALCOA and sent back for re-fitting prior to completion by Continental, which was expected in early March.

12-Cylinder Tests – Contract W-535-AC-8131: The setup had been completed except for minor details. The engine was placed on the new setup and motored over using the dynamometer for 1 hr. A noise developed somewhere in the rig, the engine was removed, inspected and found free of fault; the noise probably originated from the couplings or dynamometer. The engine was assembled without the crankshaft quill so supercharger tests could continue. Some running in was required because of new supercharger drive bushings in the reduction gear housing; 3 hrs of this run-in were accomplished.
Contract W-535-AC-8355 P.O. 36-2895 Items 1 and 2 – Cylinder and Piston Assemblies: Most material had been received and was in work. Manufacturing completion and inspection were promised for 3 April.
Item 3 – Valve Gear: Detail drawings were complete and released for manufacture, completion of which was promised for 3 April.
P.O. 36-3709 – Test Engine Connecting Rod: The rod forging was received from the Wyman-Gordon Company and was being machined. Completion was expected on 3 April.

Engineering: Routine drawing changes continued.
Reference Wright Field Memorandum Report Serial NO. E-57-285-27, quotation for mounting plates, was submitted to MatCmd in Continental letter dated 15 Feb 1936. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 4 – 6.]

6 Mar 1936. Air Corps Inspector Robert P. Triggs wrote MatCmd's Engineering Section Chief, reporting XO-1430-1, A.C. #34-298 work status. A chronological summation of work completed and difficulties encountered follows:
22 Feb 1936: Engine motored over on the dynamometer at 400 rpm for 57 minutes, removed and disassembled to determine the cause of an unusual sound apparently from the crankshaft.
24 Feb 1936: All engine parts were in excellent condition, the lubrication was functioning normally. The unusual noise was caused by a worn coupling between the dynamometer and water brake.
25 – 29 Feb 1936: The engine was assembled without a quill shaft and camshaft driveshaft to obtain supercharger overspeed data at 3,300 rpm crankshaft speed, and to run-in accessory drive eccentric bushings. After mounting on the dynamometer test stand, the supercharger was driven via the dynamometer at crankshaft speeds increasing in 200 rpm increments at 15 minute intervals from 100 to 2,100 rpm when testing was interrupted by dynamometer bearing failure adjacent to the water brake coupling. The dynamometer bearing was replaced.
2 – 3 Mar 1936: Supercharger operation continued but the same dynamometer bearing overheated after the supercharger had been operated through the accessory drive for 17 minutes at 3,000 crankshaft rpm. The dynamometer bearing housing was repaired. The engine nose section was removed and inspected; the accessory driveshaft drive gear shaft, Dwg #503538, had overheated in its front eccentric bushing, Dwg #503542; a new bushing was being designed.
4 Mar 1936: The engine cylinders were removed for cylinder wall lapping to provide a suitable wearing surface for piston rings. Excessive oil pump and coolant pump idler bevel gear, Dwg #503592, wear was found. Separate reports on the piston rings and idler bevel gear were provided. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 7 – 9.]

10 Mar 1936. Triggs notified the MatCmd Engineering Section Chief that XO-1430-1 testing would be delayed 10 – 14 days while test equipment repairs and partial replacement was accomplished. A fire and explosion in the engine test house apparently originated in the sewer outlet or exhaust tunnel. The engine was not in the test house and was not harmed. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 10.]

11 Mar 1936. Triggs notified the Engineering Section Chief that the front eccentric bushing, Dwg #503542, had originally featured a spiral oil groove cut into the bearing surface that was meant to flow more oil to the drive gear. Inspection revealed that the drive gear shaft had only been bearing on about 1/3 of eccentric bushing bearing surface adjacent to the bushing hold-down flange. In order to determine if the eccentric bushing became out-or-round when heated to engine oil temperature, the bushing and a steel plug of proper size were immersed in hot oil at 250°F. The eccentric bushing did not go out-of-round, but as the parts cooled it became apparent that a heat transfer out of the bushing and into the casting in which it seated was faulty. The oil annulus on the bushing's outside was reduced in size, thus providing a more rigid bushing body and uniform wall thickness. Several holes were to be drilled from the oil annulus to the bushing bearing surface, on an angle, providing more hot oil in the hold-down flange area (Dwg. #500524). If this new bushing design still failed, a steel eccentric bushing, Dwg #500526, using a lead-bronze bearing material was planned.

The oil pump and coolant pump idler bevel gear, Dwg #503592, hardness was 367 Brinell while the oil and coolant pump drive gears hardness was 497 Brinell. While all gears were within drawing specification, the idler bevel gear was near the low limit; a new idler bevel gear was on order and would have a hardness comparable to the drive gear. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 11 – 12.]

13 Mar 1936. Triggs reported XO-1430-1, A.C. #34-298 work status. A summation of work completed and difficulties encountered follows:
6 – 9 Mar 1936: The engine was assembled without a supercharger impeller to obtain further run-in with minimum load on the front eccentric bushing. The engine was motored on the dynamometer stand, starting at 400 crankshaft rpm and increasing in 200 rpm increments at 30 minute intervals to 1,000 rpm, then at 200 rpm increments at 30 minute intervals to 2,000 rpm. It was then removed from the stand for inspection. All engine parts were in good condition and the lubrication system was functioning properly. Fire and explosion in the engine test building delayed further engine testing.
10 – 12 1936: After careful examination of all engine parts, it was reassembled with new Dwg # 500524 eccentric bushings for run-in up to 2,000 rpm under its own power. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 13 – 14.]

15 Mar 1936 Progress Report. The single-cylinder test engine began an endurance run using BG 324 spherical shielded spark plugs. The engine showed severe detonation at over 10 inHgG boost; a minimum of 14 inHgG was required for 211 imep. After 3:10 hrs, two cylinder hold-down studs broke, the rings showed wear and feathering, and the gaps had increased 0.015", 0.005", 0.015" and 0.003", top to bottom. The ring wear was blamed on detonation. The cylinder was again hand-lapped, the piston fitted with new rings from the same batch, and the cylinder run-in to 3,000 rpm and 211 imep. Inspection this time showed the rings to be in excellent condition. After 1.5 hrs at 3,000 rpm and 211 imep, the engine was stopped due to a fire in the building.

At about 1100 on 9 Mar 1936, a fire started in the production test end of the test building. Despite efforts of the Continental crew and Detroit Fire Department, fire with explosions spread through the remainder of the building via a pipe trench and exhaust tunnel in the floor. After the arrival of a chemical wagon with foamite, the fire was put out about noon without severe injury or fatality. Insurance adjusters were called immediately and Continental estimators started listing damages. The floors and trenches were cleaned, and the piping, wiring and building were inspected. The test room with the Hyper single was only slightly affected, but due to damage to the exhaust tunnel it was not possible to run this engine. The test room for the Hyper 12-cylinder was damaged by an explosion in the exhaust tunnel that lifted the floor on each side of the dynamometer and by fire in the pipe trench, not to mention liberal foamite application. The wall between this room and the adjacent one was cracked. Piping to heat exchangers for oil and engine coolant was shifted, straining and cracking some joints. Instruments would all require recalibration. Continental believed that insurance adjustment would be complete by 21 March and that repair work would be done by 1 April, when tests could be resumed. The Hyper engine was not in the test room and was not damaged.

Contract W-535-AC-6834 Item 3: Complete except the mount plate assemblies, which had been received from ALCOA and were being machined by Continental. Completion and inspection was expected by 25 March.

Contract W-535-AC-8355 P.O. 36-2895
Item #1 – Three Cylinder Assemblies: All material had been received except coolant transfer elbows. Manufacture completion and inspection was promised for 3 April.
Item #2 – Three Piston Assemblies: Complete and awaiting inspection.
Item #3 – Valve Gear and Drive Assemblies: All material on order with delivery promised before 29 March. Construction would not be complete before 11 April.

P.O. 303709 – Test Engine Connecting Rod: Connecting rod bearings had been received and were being inspected. Connecting rod machining was nearly complete and was promised for 28 March. Order completion was anticipated for 3 April.

Torsiometer Assembly: New parts to adapt the Prescott torsiometer were in work. Parts for sealing the crankcase for a blow-by meter were complete. Government-furnished accessories, such as starter, generator, fuel pump, etc., had not been received; these were required to proof test the drives during engine endurance tests. When Government-furnished smooth approach orifices arrived Continental proposed to re-check the supercharger tests. Air Corps release to obtain 100 octane fuel had been received but an order would not be placed until test house repair work began.

Engineering: Routine drawing changes continued. New accessory drive shaft eccentric bearings were designed to provide more oil flow. One set was to be made of steel-backed lead bronze. Detail drawings of the revised part were forwarded to MatCmd. Assembly drawing SK 56 showing Hyper cylinder adaptation to an Air Corps test engine was completed and mailed to Wright Field. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 16 – 19.]

17 Mar 1936. Triggs wrote the Engineering Section Chief reporting no progress on XO-1430-1, A.C. #34-298, since 11 Mar 1936. The engine had been assembled, minus the nose section, which was held up until the engine test equipment was repaired so as to determine whether the engine would be assembled with the quill shaft; this assembly could be done in 30 minutes. The delay has been due to the inability of Continental and its insurance agent to arrive at a satisfactory claim settlement for the fire and explosion. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 15.]

17 Mar 1936. Chenoweth met with Air Corps Inspector Snyder, who asked whether he should give Continental results of his experience, which might help O-1430-1 development. Chenoweth cautioned that extreme care would be required to not divulge any manufacturers' trade secrets or processes. Any information obtained by MatCmd on MatCmd equipment could be divulged, but no processes used by another company unless he first received MatCmd approval. Chenoweth told Snyder that his project reports to the Air Corps were to include not only chronological reports but also special reports covering important phases such as piston ring difficulties, idler gear bushings, etc. Snyder asked about formal releases on any manufacturing changes made during run-in periods and was told this was unnecessary as formal releases would be required after the engine was accepted by the Air Corps for 50-hr development tests. Snyder stated that Wright Aeronautical Corporation was very interested in certain test equipment Continental had installed and was told that if he obtained permission to divulge this information it should be given to the Air Corps Inspector at the Wright plant for official transmittal. [USNARA RG342 P031222. 20 Mar 1936 Memorandum Report E-57-285-31, Conference on 17 Mar 1936 with the Air Corps Inspector at Continental Aircraft Engine Company on the O-1430-1 Engine.]

17 Mar 1936. Chenoweth met with Tilley, Bachle and Air Corps Inspector Snyder. There was difficulty with maintaining the O-1430-1 mounting plate squareness; after receipt from ALCOA and a few days of standing, the mounting plate tips were 0.063" out-of-square. ALCOA attributed this to bowing of the aluminum angle riveted to the mounting plate rear and suggested removing or modifying this feature, which had been insisted upon by MatCmd. Mounting plates for the static tests were promised for 22 Mar 1936.

Regarding the O-1430-1 single-cylinder test engine piston ring difficulties, Bachle stated that 1.5 hrs at 3,000 rpm and 211 imep had been achieved without any piston ring trouble. However, this testing was terminated by test house fire not connected with the O-1430 project. American Hammered piston rings were still being used and American Hammered blamed the ring wear on hot-grinding the cylinders, which left numerous humps in the cylinder wall when it cooled to normal operating temperature. This could be overcome by lapping the cylinder cold to eliminate the humps.

The 12-cylinder engine had been run for 7.5 hrs, 5 hrs of which was without the supercharger impeller. One-half hour had been run at 2,000 crankshaft rpm, with the only trouble being with the idler bushings in the front crankcase wall. These bushings were now made of bronze, but Continental was making new ones of steel lined with high-lead bronze. None of this could be tested because of the fire damage, but Continental hoped to again be testing by 1 Apr 1936.

Chenoweth told Continental that it made no difference whether the ducts between the supercharger and air measuring device were solid or flexible. When Continental objected that the carburetor pressure might be in error, Chenoweth suggested removing the carburetor and elbow for the supercharger tests.

Bachle stated that spark plugs were still giving trouble, but that the BG-157 had proven to be the most satisfactory, usually lasting around 10 hrs. Modified BG plugs were available, as were some experimental HT plugs. Continental representatives stated that if MatCmd purchased an additional single-cylinder Steel Products Engineering Company test engine, that they would be glad to make suggestions and recommend design changes since they had the only actual experience with the engine as configured.

Bachle was impressed by the Prestone-to-water cooler that the Harrison Radiator Corporation had made of electro-deposited copper. With a 250°F coolant-in temperature and 235°F coolant-out temperature, this 10" x 18" x 8" cooler could dissipate 18,500 btu/min with a Prestone flow of 180 to 220 gpm with a 20 gpm flow of ≤ 85°F water; pressure drip through the cooler was 3 – 5 psi.

Bachle had installed a combination electric clock and rpm counter manufactured by the Standard Electric Time Company of Springfield, Massachusetts, which seemed to give very satisfactory service. [USNARA RG342 P031224. 20 Mar 1936 Memorandum Report E-57-285-30, Conference on 17 Mar 1936 at the Continental Aircraft Engine Company Regarding O-1430-1 and R-670 Engines.]

20 Mar 1936. Prescott met with Continental engineer James Kinnucan and discussed mount plate details in hopes of improving its strength and reducing its complication and cost. The leading proposed change involved shortening the mount plates by about 3.5" in order to make the reinforcement at the plate rear flat instead of an arch. They hoped this would eliminate the plate's warping and distortion.

Single-cylinder test equipment now on order would make a slight cam box change so that scavenge oil would be carried away via the vertical drive shaft housing instead of an external tube. Kinnucan requested that a check list of all Government-loaned property at Continental. It seems that several equipment items were on hand whose accountability was not clear and that Continental wanted to eliminate as much unnecessary stock as possible, particularly in accounting for failed parts then in Continental's possession.

The parties discussed upcoming testing and the mount plates' role. A dummy XO-1430-1 iron-pipe test fixture was being built to approximate the engine crankcase, cylinders and cam box strength and stiffness. This would first be used to apply torque and vertical loads to the mount plates. Kinnucan requested specifications for baked enamels for use on cylinder assemblies. [USNARA RG342 P031220. 25 Mar 1936 Memorandum Report E-57-285-32, Conference with Mr. Kinnucan of Continental Aircraft Engine Company on XO-1430-1 Engine Tests.]

31 Mar 1936 Progress Report. All items of Contracts W-535-AC-6322 and W-535-AC-6834 were complete and accepted by the Air Corps Inspector. The single-cylinder test setup was modified to exhaust outside the building through a Burgess muffler instead of the exhaust tunnel. Test runs with the same piston rings as used in the previous report were continued at 3,000 rpm and 211 imep. After 18:10 hrs of this endurance running, there was no wear or other defects. Continental wished to correct Memorandum Report E-57-285-30 dated 20 Mar 1936, which presented what appears to be an erroneous explanation of the single-cylinder piston ring difficulties as follows:

"Previous difficulty with ring wear was due to grinding cylinders cold, which resulted in a non-uniform bore when the cylinders was hot. The present practice is to grind the cylinder bore at a temperature corresponding to running conditions, which gives uniform bore under operating conditions. However, the quality of the ground surface was such that there was still undue wear of rings during the preliminary running-in periods. Hand lapping of the cylinder while cold gives a better surface finish and does not eliminate the lack of uniformity of the bore in the cold cylinder."

The results were reported to the BG Corporation by letter on 31 March. The Bendix HT 5P spark plugs were run despite unsuitable shielding to obtain performance figures on resistance to lead fouling. Of the four spark plugs tested, the best two were missing badly at 6.5 hrs. Continental expected that spark plug company representatives would confer in the near future to help solve this difficulty.

12-Cylinder Engine Test – Contract W-535-AC-8131: The engine was assembled with a new idler shaft eccentric bushing ahead of the long supercharger driveshaft but without the quill shaft to drive the crankshaft. It was set up on the dynamometer for run-in and test. During this run-in it was impossible to develop full supercharger outlet pressure; this was due to the diffuser having been reversed during assembly. The eccentric bushing was in good condition.

The engine was again run with the diffuser correctly assembled and using the smooth approach orifice borrowed from Wright Field. Supercharger performance curves checked well with data previously obtained with the sharp-edge orifice except the maximum airflow with the smooth orifice was considerably higher than that obtained with the sharp orifice. Testing was stopped to clear the room to replace concrete previously damaged by fire. Further data was required to complete the supercharger performance tests and produce a report.

Contract W-535-AC-8355 P.O. 36-2895:
Item #1 – Three Cylinder Assemblies – There had been a delay in getting a satisfactory bore grind. Continental expected the work to be completed and inspected by 11 April.
Item #2 – Three Piston Assemblies – Complete and accepted by the Air Corps Inspector.
Item #3 – Material had been received and work completed except for the cam housings. Work completion and inspection was promised for 11 April.

P.O. 36-3709 – Test Engine Connecting Rod: Work was awaiting final inspection.

Torsiometer Assembly: Completion of the parts to adapt the Prescott torsiometer was promised for 11 April. Shell Oil Company promised delivery of 10,000 gallons of 100 octane fuel on 13 April.

Engineering: Routine drawing changes continued. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 20 – 22.]

15 Apr 1936 Progress Report. The single-cylinder engine was fitted with a new exhaust valve, new 0.010" oversize American Hammered piston rings with 45° gaps. The exhaust valve showed guttering on its face and was returned to Wilcox-Rich for examination. After run-in, the new rings showed a 0.003" maximum gap increase. After 4.5 hrs at 3,000 rpm and 211 imep the gaps were unchanged. Champion M11-64 spark plugs were used for this run with no trouble. Total running time on the forked rod was 169 hrs, of which 81 hrs were at 3,000 rpm and 211 imep. Magnafluxing revealed no cracks.

The single-cylinder engine base was disassembled due to excessive noise. The balance rod clearances had increased from 0.008" to 0.015". The knuckle pin of this rod's small end had 0.002" clearance instead of the original 0.0005" The balance rod parting line was being ground to reduce the vertical clearance, and the knuckle pin was being chrome plated and reground.

The 12-cylinder engine was run-in under its own power up to 1,500 rpm with a propeller load based on 500 hp at 3,000 rpm. Engine firing was started at about 600 rpm and speed was increased by 100 rpm every 45 minutes up to 1,500 rpm. The engine was then idled at about 100 rpm. This run was completed in 6 hrs, the engine removed from the test stand, disassembled inspected and reassembled without changes. The run-in was continued to 308 hp at 2,850 rpm and then briefly to 330 hp at 3,000 rpm. An unusual rattling noise, apparently from the water brake, caused the run to be stopped at about 8 hrs.

Engine inspection revealed the propeller shaft inner end bearing had overheated over 1/3 of its length at the gear end. This bearing was grooved to enhance lubrication and new bearings ordered. All steel parts except the crankshaft were magnafluxed; two camshaft drive spur gears were cracked and were to be replaced.

The water brake was disassembled to find the source of its rattle. A new jaw coupling with a better fit on the water brake shaft splines as well as on the jaws was being made. The five water brake discs were as much as 0.018" loose on their spline. These splines are being machined, plated and ground to obtain a tight fit. Parts to adapt the Prescott torsiometer were nearly complete and were to be used in the next run after the week of 20 April.

A total of 62.03 hrs of which 47:53 hrs was motoring and 14:10 hrs was under power had been run. The motoring runs were to check supercharger operation and performance and to run-in the pistons and related parts. Piston motoring time was 6:40 hrs and the balance of the time was without crankshaft or pistons. The supercharger was run at full output for about 4 hrs.

Contract W-535-AC-8355 P.O. 36-2895: The cylinders, pistons and valve gear were complete and accepted by the Air Corps inspector; they had been packed and were to be shipped on 17 April.

P.O. 36-3709 – Test Engine Connecting Rod: Accepted by the Air Corps Inspector and shipped on 9 April.

Engineering: Shell Oil Company supplied 10,000 gallons of 100 octane fuel, represented by sample E-3609, which had been forwarded to Lt. F.D. Klein at Wright Field; he confirmed that the sample conformed to specification 2-92. Routine drawing changes continued. Work on the final stress analysis had resumed, and a new XO-1430-1 installation drawing representing the as-built engine had been started; the existing drawing was made prior to detail drawing completion and engine assembly. On 6 Apr 1936 Roy Hurley and Walter Lees of the Bendix Products Corporation HT Spark Plug Division met with Tilley regarding XO-1430-1 spark plugs. They viewed the assembled engine and Hurley said that the lead fouling was due to excessive spark plug shell temperatures that could be eliminated by revising the cylinder spark plug inserts. A revised design was to be submitted to MatCmd for comment. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 23 – 25.]

13 Apr 1936. A MatCmd conference involved Tilley and F. Gould of Continental, and MatCmd's Prescott and J.B. Johnson. Tilley brought with him the entire supercharger housing with diffuser in order to demonstrate to MatCmd the corrective action that had take place subsequent to the accidental drawing of mercury from the manometer into the supercharger when the engine was being started. Tilley stated that a backfire preceded the accident and probably caused the mercury to change from a 17 inHgG vacuum to a positive pressure and then on a return surge, inertia carried the mercury into the supercharger. Since no one expected the mercury to do any damage, it was not quickly removed. However, amalgamation with the magnesium in the supercharger housing and diffuser set in and was especially bad at the supercharger scroll bottom where the mercury lay in a pool while wetted by condensation and leaded fuel upon which the engine was being operated. When examined 24 hrs later it was found that the mercury had eaten pits about 0.06" deep into the scroll bottom. The damaged parts were carefully scraped and the supercharger interior was treated with crankcase paint in an effort to prevent further erosion. However, MatCmd found the erosion still in progress under the paint. Tilley thought this action was accelerated by the presence of moisture and suggested that the parts be immersed in water until the reaction ceased. It was found that the amalgam broke down in the presence of water, giving off a gas, while free mercury was left and could then be removed by washing or brushing. The parts were submerged in water and vigorously brushed until bubbling ceased, after which it appeared the amalgam had been destroyed, leaving solid metal. Tilley planned to repeat the water bath back in Detroit in order to detect any further reaction, after which it would be cleaned, painted and put back in service.

Tilley stated that after the 12-cylinder had operated at 350 hp and 3,000 rpm, the bearing in front of the propeller shaft gear had nearly failed. The pinion bushing on the shaft interior had also been damaged, but this damage was thought to have been caused by the propeller shaft bearing failure. Tilley stated that a revised oil groove system was being installed in a new bearing and that the engine should be able to resume testing without delay. Tilley stated that the completed engine would then be ready for torsiometer tests to determine whether serious vibration periods existed in the engine's operating range while on the dynamometer. MatCmd personnel planned to visit Continental and run the torsiometer tests when the engine was ready to run.

The single-cylinder equipment ordered by MatCmd was ready to ship. The cylinders had been buffed with a felt wheel and abrasive mater to a high polish. MatCmd objected to this surface treatment and suggested the cylinders be carefully hand-lapped to equalize any surface irregularities. The connecting rod ordered by MatCmd had been shipped the previous week. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 26 – 27. 16 Apr 1936 Memorandum Report E-57-285-34, Conference with Representatives of the Continental Aircraft Engine Company on the XO-1430-1 Engine.]

11 Apr 1936. Prescott confirmed a 10 Apr 1936 telegram from Air Corps Inspector Snyder and an 11 Apr 1936 telephone conversation with Tilley. Two methods were proposed to stop the mercury erosion after it had been accidentally drawn into the supercharger housing. 1. Heat the affected castings to 130°F to 150°F in a sodium sulfide solution, which would react with the mercury, removing it from the magnesium casting. 2. Heat the casting in a 670°F to 690°F electric furnace for 0.5 to 1 hr, which might boil off the mercury, halting the erosion. In the future, mercury manometers should have 0.031" restrictions at both ends to prevent mercury column surging and repeating the current difficulty. Tilley stated that the manometer vacuum when the accident happened was about 17 inHgG and the only explanation was that a backfire must have produced a surge great enough to force mercury into the supercharger on the return surge. A 40" manometer had been in use, which should have been ample. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 28. 18 Apr 1936 Memorandum Report E-57-285-33, XO-1430-1 Engine Test.]

23 Apr 1936. Prescott visited Continental to get XO-1430-1 torsional vibration records. The engine was operated on the dynamometer stand at speeds from 400 rpm to 2,000 rpm in a propeller load curve of approximately 1/3 rated power. Torsiometer records were taken in 50-rpm increments from 500 to 1,500 rpm and by 100 rpm increments to 2,000 rpm. The intent was to extend this instrumentation to 3,000 rpm and the engine's rated power. However, it became difficult to maintain adequate oil pressure. Washers were put under the relief valve spring, but pressure continued to fall. At the conclusion of the 2,000 rpm run, idle oil pressure had dropped from 50 psi at test start to 25 psi.

The reduction gear was disassembled and its bearings inspected for excessive wear that could account for the oil pressure reduction, but no cause was found. Since about 9 hrs testing had transpired since the last complete inspection, Continental disassembled the remainder of the engine. It had previously operated as a right-hand tractor, but interference of the torsiometer gears on the starter pad necessitated rotation direction reversal. Neither Tilley nor Prescott wanted to push on and risk an engine failure without explaining the oil pressure drop. It was proposed to remove one cylinder bank, connect an external oil pump to the engine lubrication system and circulate oil diluted to the same approximate viscosity as 120-second oil at operating temperature, and observe points where oil flow was excessive. However, it was decided to completely tear down the engine and reassemble, replace any parts that might have failed, and conduct this oil flow test prior to resuming torsiometer tests.

The torsiometer records indicated a 6.0 order vibration period in the crankshaft at about 625 rpm. On this basis a 2.5 order vibration would be expected at 1,500 rpm, and such a period was observed, although with the low power setting its amplitude was very small. Calibrations indicate that a 1.5 order period would be expected at about 2,500 rpm, but this was not observed due to test termination at 2,000 rpm. Continental was to advise MatCmd of any unusual conditions found during the teardown and then participate in continuation of the torsiometer tests. Prescott said that no definite conclusions should be drawn from the torsiometer tests since the power output was very low; the tests were to be repeated at a later date.

Dynamometer operation showed the 12-cylinder engine was exceptionally smooth over the observed speed range, despite the long gallery manifold being used to supply the 12 intake pipes coming off at right angles to the manifold. No difficulty with oil leaks was experienced. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 33 – 34. 25 Apr 1936 Memorandum Report E-57-285-35, Visit of Division Representative to the Continental Aircraft Engine Company.]

30 Apr 1936 Progress Report. After balance rod repairs, the single-cylinder test engine was reassembled. All gasoline drums marked 92 octane were tried and found to be inferior to the previously used gasoline so the 100 octane Shell gasoline was used when testing resumed. Champion M-11-64 spark plugs tested in a bomb had diminished characteristics since last run about 10 days prior; running continued with Bendix HT 300 A1 plugs.

In view of the higher oil-in temperatures apparently required by the 12-cylinder engine, single-cylinder engine runs at various oil-in temperatures were being made to determine possible piston ring, cylinder wall or piston deterioration. A 1-hr run at a 160°F oil-in temperature produced no obvious trouble. However, further running was stopped until the 2nd piston ring locator pin could be replaced; it had been loose during the last inspection.

The water brake had been repaired and the 12-cylinder engine reassembled with gears for driving the Prescott torsiometer. This necessitated operating the engine in the opposite direction. The propeller shaft bearing was replaced with a new one of the same type but with spreader grooves to ensure better oiling. New spare bearings without oil grooves had been received. An in-line booster oil pump was installed.

The engine was run-in for 14 hrs up to 2,000 rpm and low imep. The propeller shaft bearing was inspected and found satisfactory. Torsiograph records were then taken by Prescott in 50 rpm increments from 500 to 1,500 rpm and by 100 rpm increments up to 2,000 rpm. The intended progress to 3,000 rpm was halted when oil pressure dropped. No conclusions were drawn from these torsiometer tests as the power output was very low. These tests were to be repeated when the engine could be run at higher power and speed.

The engine was removed from the test stand, disassembled and inspected. The oil pump was tested and performed normally. Pressure regulator tests indicated a tendency for the relief valve plunger to stick and that the relief valve spring should have a lower rate. Pump capacity appeared adequate. The engine oil demand was excessive because of leaks. The crankshaft plugs did not seal well; new plugs were being obtained. The reduction gear oil squirt was about 0.75 gpm at 100 psi; this was reduced to 0.10 gpm by blocking the 0.063" oil feed hole and filing a flat on the inner tube to provide the oil supply to the four oil holes in the outer tube.

Overall engine condition was good except that four intake Stellite valve faces were cracked; these were returned to Wilcox-Rich via Mr. Jardine, who advised changing the intake valves to austenitic steel and has started manufacture of 14 such valves. Continental had enough spares on hand to continue the run. The 12-cylinder engine had 47:53 hrs motoring time and 20:25 hrs running under its own power

Contract W-535-AC-8355 P.O. 36-2895 – Cylinders, Piston and Valve Gear: Shipped to Wright Field on 17 Apr 1936.

Engineering: Routine drawing changes continued. A new XO-1430-1 installation drawing had been made and prints mailed to Wright Field. Prescott torsiometer adapters for the camshaft end were detailed. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 30 – 32.]

Single Cylinder Performance	XO-1430-1 Run-In

15 May 1936 Progress Report. A 1-hr run under contract conditions was made on the single-cylinder engine with a 190°F oil-in temperature. The top ring gap increased by 0.005". During this run there was no detonation or uneven operation.

Further oil distribution tests were made on the 12-cylinder engine. The run-in was continued on a propeller load curve up to 410 hp at 2,900 rpm. Inspection thereafter revealed loose or broken piston locating pins and camshaft drive bevel gears with teeth cracked at their roots. The test was delayed while new gears were made. The engine now had 80:42 hrs total time, 29:55 of which was under its own power and 50:47 hrs dynamometer motoring.

Contract W-535-AC-8355 P.O. 36-2895 – Cylinder, Piston and Valve Gear: Two bound sets of detail blueprints were forwarded to Wright Field on 7 May 1936.

Engineering: Routine drawing changes continued. Special spark plug inserts to seal at the insert cylinder end had been detailed and released for manufacture; these would be subjected to single-cylinder testing. A special oil relief valve providing closer oil pressure regulation had been detailed and released for use on the O-1430-1. Crankshaft oil plugs had been redesigned to stiffen the bosses. New castings were promised for 20 May. New camshaft drive gears of SAE 2512 steel instead of oil-hardened SAE 6145 steel were released for manufacture. A new gear design with stronger teeth was in process. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 40 – 44.]

18 May 1936. Triggs reported XO-1430-1, A.C. #34-298 work status. When the cylinders had been removed after the last operating period, all cylinder walls were found rusted with #3L being the worst. Piston rings and pins were in normal condition except as follows:

The ring breaks all occurred within 2" of the gap.
Broken ring pins were sheared.
Spark plugs were clean.
Carbon on the piston heads was about 0.06" deep.

In order to prevent future cylinder corrosion when the engine was to be idle for several days Continental intended to prepare the cylinder walls and valves for temporary storage in accordance with Technical Order No. 2-1-1. All broken piston rings were replaced with new American Hammered rings from the same lot. All broken ring pins were removed and new ones shrunk-in instead of being pressed-in as before.

18 May 1936. During a MatCmd meeting involving Continental's Tilley and Gould and Prescott. Tilley stated that the XO-1430-1 was being reassembled with new camshaft bevel pinions at camshaft driveshaft inboard ends; the previous bevel gears had cracked and been replaced with gears of improved material. The crankpin oil plug designs had been changed to better support the lip that overhung each end to engage with the oil nipples. He stated that two crankpin journals and one main bearing journal leaked badly at the oil plugs. All plugs were to be replaced with new plugs and the crankpin and main bearing bores were to be trued. By replacing several plugs the oil flow had been reduced to less than pump capacity. Continental intended to take the engine to 3,000 rpm and 600 hp, make a tear-down examination, and continue torsiometer tests to 3,000 rpm. These tests were previously run to 2,000 rpm and were terminated by failure to maintain oil pressure.

The matter of provisions to prevent the spring-mounted engine base from overturning under high engine torque was discussed. Tilley stated he would have this matter investigated prior to running the engine at full power.

The matter of single-cylinder blow-by readings was discussed. MatCmd told Tilley of its test engine's peculiar behavior: when only a 0.375" orifice was left open, a vacuum of 1 inHgG was maintained on the crankcase by the scavenge pump, while a pressure of 2 inHgG was recorded when a 1.5" breather was opened. Under the latter condition a very high blow-by rate was indicated, which remains the same as when the engine was motored as when running under power. For this reason, the accuracy of blow-by measurements was under serious question when a pipe of appreciable size loaded the blow-by meter. Feasibility of a fabricated steel crankcase was discussed and it was agreed that the matter was worthy of investigation. Tilley stated that the spark plug situation was still the most critical problem faced in XO-1430 development. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 50 – 52. 21 May 1936 Memorandum Report E-57-285-36, Conference with Representatives of Continental Aircraft Engine Company on XO-1430-1 Engine.]

28 – 29 May 1936. Prescott visited Continental where the XO-1430-1 was operated with the Prescott torsiometer on the propeller load curve through 3,000 rpm 750 hp. Cards were taken at 50 rpm increments up to 2,900 rpm at which time an oil pressure loss at the engine's reduction gear resulted in shutdown. There was no sign of damage and the engine when motored over appeared undamaged; it was therefore decided to complete a previously-started torsiometer run on the 600 hp propeller load curve, which was terminated when at 2,000 rpm with an oil pressure failure. At that time a bearing suddenly seized and caused a sharp rpm drop. The engine was quickly shut down.

Teardown inspection revealed that a special idler gear shaft, which had been installed to facilitate driving the torsiometer, had failed at a shaft weak section. Since pressure oil was carried through a drilled hole in the shaft, the shaft's failure caused the initial oil pressure drop. Subsequent to this, the gear operated as an overhung gear with only one bearing. Under these conditions, operation at light load failed to disclose any engine mechanism defect, but as soon as the supercharger load approached full power the excessive single overhung bearing load caused the idler gear to be displaced out of its proper position and the single bearing on which it was running badly distorted, causing damage to the front crankcase diaphragm. The crankcase and reduction gear housing were both taken to the metallurgical department and etched to determine whether the damage was great enough to necessitate the fabrication of a new crankcase or gear housing, but it was discovered that neither was cracked. Engineers decided that the crankcase could be re-bored and an oversize bushing installed in order to continue the tests. At the same time, it was apparent that a stronger idler gear could be used and the failed bearing could be made longer for the special purpose of completing the torsiometer study. Torsiometer tests had previously been estimated to require two or three hours. However, it was apparent that considerable development was required before the engine design was satisfactory for procurement. For this reason, the idler shaft and bearing layout was to be improved as much as possible and a new gear installed in order to continue the tests.

The torsiometer records showed a 1,000 rpm to 2,600 rpm range that was comparatively free of crankshaft resonance, but the 1.5 order vibration period became apparent at 2,600 rpm, reaching its maximum amplitude of about ± 2.5° at 2,800 rpm and decreasing to ± 1.5° at 2,900 rpm. These amplitudes would be higher if engine power output was increased from the 750 hp propeller load curve to the 1,000 hp propeller load curve. Prescott stated that the present specification called for engine operation at rated manifold pressure or full throttle from 110% normal speed down to 50% normal speed in order to provide satisfactory operation under all military aircraft engine operating conditions. The torsiometer records made it apparent that a damper would be required to reduce the vibration amplitude to a safe value, especially in the 2,600 rpm to 3,300 rpm range, where torsional vibration was extremely severe. Several approaches to this were discussed and Continental agreed to immediately study this issue since a drastic engine design change would be required to eliminate this resonant period. The study results were to be discussed with MatCmd and the most logical problem solution implemented as early as possible. In the meantime a reduced-stiffness quill shaft would be designed and built to permit engine operation to 3,000 rpm without danger of crankshaft failure. This would permit engine operation at rated power and speed until the damper could be fitted and speed restrictions removed.

XO-1430-1 operation was exceedingly smooth with the exception of the 1.5 order vibration from 2,600 rpm to 3,000 rpm that can be plainly seen and felt. Prescott believed that a damper would allow the engine to operate at all speeds. A surprising engine feature was that there was no indication of poor mixture distribution, even at idle speed, with the high-velocity tapered gallery manifold. The mixture temperature was low enough that one's hand could be held on the supercharger scroll; fuel vaporization as it passed through the supercharger was thought to account for this. However, the fuel injection provisions that had been designed into the engine would provide additional insurance of smooth operation. Prescott pointed out that the piston/cylinder clearance might be insufficient as the engine was run at higher power settings and cautioned Continental to observe these clearances closely. Prescott was not yet satisfied with the piston ring setup but was hopeful that further single-cylinder experiments would result in a workable combination; inclusion of a beveled oil scraper ring in the lower ring groove had already greatly improved piston and ring condition. [RD342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 68 – 71. 6 Jun 1939 Memorandum Report E-57-285-37, Conference at Continental Motors Corporation, Detroit, Michigan, on the XO-1430-1 Engine Development Test.]

XO-1430-1 Run-In Data

31 May 1936 Progress Report. The single-cylinder engine was fitted with a new piston without ring locating pins. The cylinder was run-in to 3,000 rpm and 211 imep after which the rings showed a 0.005" gap increase. Running time for this cylinder during this period was 9:55 hrs. The cylinder now has 190 hrs total time of which 88.5 was at rated rpm and imep or higher.

The new bevel cam drive gears were placed in the 12-cylinder engine and a 5 hr run-in made to 3,000 rpm and 607 hp. After the run inspection revealed the coolant pump idler and accessory drive bushings, Dwg #501052, to be scored. These bushings were replaced, along with several piston ring locating pins and three broken piston rings. All lower compression rings were replaced with new ones featuring a 10° on the head end to provide oil control.

After run-in on the dynamometer with a 3,000 rpm and 750 hp propeller load. During the last part of the run-in, Prescott was present and took torsiometer cards covering the 2,000 to 3,000 rpm speed range at 50 rpm intervals. One run was based on a 3,000 rpm 600 hp propeller load and the second was based on 3,000 rpm and 750 hp. While running at top speed the accessory drive idler gear shaft failed; this gear was special with a small shaft to clear the torsiometer drive. XO-1430-1 total time was 93:47 hrs, time under power was 40:35 hrs, and time motoring was 53:02 hrs.

Engineering: New camshaft drive gears, Dwgs #503549 and #503655, had been redesigned to use Nitralloy "G" steel. The torsiometer cards taken show a third harmonic at 2,800 rpm with a 2.5° amplitude, which was excessive. A new quill shaft was designed to reduce this period to 2,500 rpm, which would enable engine operation at 3,000 rpm to continue development. Work was started on designing a damper to reduce the third harmonic. All parts damaged by the runs for which replacement was necessary, including the new lower-frequency quill shaft, were released for manufacture. An itemized list showing Government liability on all replacement parts used to date had been made and was being priced. This was to be attached to the next progress report. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 45 – 49.]

6 Jun 1936. In a telephone conversation, Tilley revealed that in reboring the reduction gear housing bushing boss, cracks were discovered making the housing impossible to repair. Tilley did not know if the crankcase was cracked, but it was definitely sprung. Continental would determine whether to use the crankcase after machining was done. This situation brought up the question of having spare parts or a spare engine to avoid future testing delays. Prescott tasked Tilley to prepare a cost estimate covering spare parts. [RD342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 72 – 73. 10 Jun 1936 Memorandum Report E-57-285-38, Telephone Conversation with Mr. N.N. Tilley of Continental Aircraft Engine Company on XO-1430-1 Engine and 50-hr Test.]

11 Jun 1936. In a Wright Field conference involving Tilley, Maj Page, Prescott, Chenoweth and Snyder, Tilley reported that the recent special torsiometer drive failure had sufficiently damaged the reduction gear housing that it would require replacement. The damage consisted of cracks in the rear diaphragm and bearing boss of the supercharger drive idler gear that had failed. The reduction gear housing casting was promised for 12 June and the finished housing for 22 June. In the meantime the rest of the engine would be reassembled so that testing could resume as soon as the reduction gear housing was completed and installed.

Design work was in progress on a Lanchester type damper to be installed at the crankshaft rear. This might require moving the accessory drive housing back about 0.5" to provide space for the damper. Layouts were expected to be completed during the week of 15 June and would be submitted to MatCmd for review prior to proceeding with detail drawings or parts. A new quill shaft was being made that would reduce the 1.5 order vibration period from 2,800 rpm to 2,500 rpm, thus permitting engine operation at 3,000 rpm so that engine parts not dependent on the crankshaft vibration characteristics could be tested. Once the new vibration damper was tested, a quill shaft to drive the vibration damper would be designed.

A single-cylinder engine cylinder barrel had circumferentially about half way up the water jet portion of the cooling jacket. Tilley thought that the method of punching the cylinder barrel forgings was responsible for faulty grain flow, a matter that had been discussed with the forging company, which maintained this was unavoidable for forgings made by this process. The same process was used for air-cooled cylinder barrels, which had not exhibited this failure. Tilley stated that an attempt would be made to improve the grain flow and barrel strength.

Tilley presented a list of parts that had been replaced during testing but did not include their cost as required by the contract. The matter of parts cost, procedure for replacing parts and Continental's general attitude toward the project was discussed. MatCmd thought that unnecessary delays had retarded project progress. Stocking spare parts by Continental to save time was also discussed; MatCmd wanted the project to move forward with fewer interruptions and less delay than in the past. MatCmd feared that the engine would be obsolete before it was complete and wanted the project "expedited in every way possible and all unnecessary delays, such as waiting for raw material or finished parts, reduced to absolute minimum." MatCmd wanted to discuss the matter of spares directly with Continental management. To that end, Continental's Purchasing Agent Clarence J. (Jack) Reese agreed to a 15 Jun 1936 meeting at Wright Field. Maj Page was to include MatCmd Legal Branch to assure Continental of MatCmd's intent to produce the engine once it was developed.

Tilley was not satisfied with the existing piston ring setup and was conducting single-cylinder experiments to develop a more satisfactory solution. Wilcox-Rich planned to replace the intake valves whose Stellite faces had cracked with new ones with hollow heads that were similar to exhaust valves. [RD342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 74 – 76. 15 Jun 1936. Memorandum Report E-57-285-39, Conference with Mr. Tilley of Continental Motors Corporation on XO-1430-1 Engine and Development Test.]

15 Jun 1936 Progress Report. The single-cylinder engine was endurance-run for 3.5 hrs with unpinned piston rings and Champion M-11 spark plugs. The cylinder cracked at a reinforcing rib fillet and was disassembled for metallurgical examination. No conclusion could be drawn regarding the unpinned piston rings. Total time on the cylinder was 193 hrs, of which 88.5 hrs were at rated rpm and imep or higher.

No 12-cylinder running occurred during this period. Wright Field conferences on 11 and 15 June, and one planned for 19 or 22 June sought to establish procedures for avoiding testing delays by making available a larger replacement parts inventory. The Wright Field conferences were covered MatCmd Memorandum Reports. New parts needed to again run the engine were promised for 26 June; the thermoid coupling between the engine and water brake was also promised for 26 June.

Engineering: Calculations of a suitable crankshaft damper size were made, and layouts incorporating this damper had been started. An itemized list showing Government liability for all replacement parts used up to 1 Jun 1936 was attached. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 57 – 65.]

Cracked Cylinder Barrel

15 Jun 1936. A MatCmd meeting involving Continental's Reese and Tilley, and MatCmd's Col Echols, Maj Page, Chenoweth and Prescott sought to greatly speed up the XO-1430-1 50-hr development test required by Contract W-535-AC-8131. MatCmd stressed that if development took too long other newer engines would become attractive and the XO-1430-1 would not be produced. MatCmd suggested that Continental stockpile forgings and castings necessary to make new parts if a failure occurred. Continental objected that the labor required for fabrication was a larger consideration than the material, and that finished parts should be stockpiled.

Reese was under the impression that three other companies were working on engines almost identical to the XO-1430-1; MatCmd confirmed this but did not elaborate whether they were air- or liquid-cooled. MatCmd asked Reese what facilities would be available for engine manufacture if the XO-1430-1 development were successful; he replied that all necessary space was being held in reserve in Detroit, and that Continental intended to equip the plant with machinery and tools for producing the engine in sufficient quantities to constitute an adequate supply source. MatCmd reiterated that the XO-1430-1 had properties that were extremely desirable, but that delays might render it obsolete. MatCmd was having great difficulty getting further experimental funds for the 50-hr development test. Once that was done, additional funds would be available for type and service tests.

Reese was concerned that the patent clauses recently included in Air Corps contracts left contractors with no patent protection if the Air Corps chose to exercise its options. This matter was tabled for further discussion. Reese pointed out that manufacturing equipment for building aircraft engines was expensive and highly specialized, and that after a contractor equipped its plant, the equipment had very little value for any other purpose. MatCmd responded that it was common practice to require submission of a first article with a contractor's bid in response to Circular Proposals, which put the designer in a more favorable position. First article delivery time was also in the designer's favor because any other bidder would have to pass development and type tests, a two to four year process.

MatCmd asked Reese if it would be possible for the Air Corps and Continental to share the spare parts cost on a 50-50 basis. Reese needed to confer with management but thought some arrangement could be made. Reese then raised the question as to the XO-1430-1 status in case the 150-hr type test was finished by 1 Jan 1937. MatCmd stated that under these conditions the engine could be purchased in service test quantities after which the contractor would have to sell it to airframers on a competitive price, installation and service basis. Reese stated that the outlook for Continental was discouraging since it had no contract with an airframer that would be inclined to use the engine for either military or commercial aircraft. Reese related Continental's experience with competing in the training engine field and related the efforts to qualify the R-670 aircraft engine through a successful type test. To date, no airframer had selected the R-670 for an aircraft design and he worried that a similar fate might befall the XO-1430-1.

Reese toured the PPL's air- and liquid-cooled dynamometer and torque test stand equipment. He was also given information on silencing the exhaust of engines under test. MatCmd asked Continental to prepare cost estimates based on supplying one, two, three and four engines for type test; Reese said this would be done immediately and that he would be back on 19 Jun 1936 to present the figures. [RD342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 77 – 80. 22 Jun 1936 Memorandum Report E-57-285-40, Conference with Representative of Continental Aircraft Engine Company on XO-1430-1 Engine.]

20 Jun 1936. Responding to a 15 Jun 1936 MatCmd request, Tilley provided an XO-1430-1 price and delivery schedule for enough parts kits and sub-assemblies to construct complete engines:

For engines completely assembled and ready to run but not operated or tested:

Continental also provided a Parts and Sub-Assembly Price List. [RG342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 53 – 56.]

22 Jun 1936. During a Wright Field conference where Reese and Tilley met with Col Echols, Maj Page, Chenoweth and Prescott, Reese submitted figures as requested on 1, 2, 3 and 4 complete engines. These included estimated prices and deliveries of these engines for the purpose of expediting XO-1430-1 development tests. This was identical to the quote Tilley had sent on 20 June. No action was taken but MatCmd asked Continental to furnish a complete price list on parts not comprising a complete engine but all necessary replacement parts to guard against delay if the test engine failed. MatCmd emphasized that the list must not include enough parts to make a complete engine. As an example, MatCmd suggested only one camshaft, four pistons and cylinders, but enough essential parts be included so that no part failure on the test engine would result in an extended delay. MatCmd wanted this list as quickly as practicable. [RD342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 86 – 87. 1 Jul 1936 Memorandum Report E-57-285-42, Conference with Messrs. Reese and Tilley of Continental Motor Corporation on XO-1430-1 Engine.]

These were all dated from receipt of order, but Tilley stated that procurement of raw stock and castings had already been initiated in anticipation of order receipt. MatCmd requested that Tilley furnish a list of the parts that had been replaced to date during engine running in order that these items might be included in the procurement authority covering this parts list.

Tilley stated that a damper design was in progress and expected to be subjected to temporary MatCmd approval on 2 Jul 1936. MatCmd emphasized that full provision should be made in connection with all parts affected by this damper installation so that procured parts would be adaptable to the design when the damper was installed. MatCmd emphasized that provision should be made for all parts affected by damper installation should be adaptable to the design when the damper was installed. However, it was not feasible to include damper parts cost because detail drawings had not yet been made, and time did permit cost estimation. The crankshaft oil plug system should be of the improved design to eliminate the trouble that had been experienced to date with oil leakage at the crankpin and main bearing journal oil plugs. Tilley stated that the specified delivery dates could be met with the present equipment setup and that these dates could be anticipated by provision of some additional shop facilities in order to reduce the time required to produce the parts required by the current test program.

MatCmd stated that the torsiometer now at Continental for use on the XO-1430-1 should be returned not later than Friday 3 Jul 1936. Tilley stated that Kinnucan would come to Wright Field on Thursday, 2 Jul 1936 with the complete analysis and layout drawings covering the damper design and would bring with him the torsiometer. [RD342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 81 – 85. 1 Jul 1936 Memorandum Report E-57-285-43, Conference with Representative of Continental Aircraft Engine Company, 29 Jun 1936.]

30 Jun 1936 Progress Report. A new cylinder from the same batch as the 12-cylinder engine was assembled on the single-cylinder test engine. The same piston used in the previous running was reground to fit the new cylinder. Valves and other removable parts were moved to the new cylinder. The piston rings were new and were not pinned. The cylinder was run-in and then operated for 5 hrs without heated carburetor intake air under contract conditions. The carburetor air was not heated because the laboratory boiler had broken down. After the run, the cylinder parts were in good condition. Another 5 hrs run with a 215°F carburetor air intake temperature showed some ring deterioration. The Champion M-11A spark plugs that were used for this 10 hr run operated satisfactorily. Shell 100 octane gasoline procured for the 12-cylinder test was used.

The operating time on the various parts was as follows:

The 12-cylinder engine was assembled with new parts and mounted on the dynamometer with a new quill drive, motored for 1:05 hrs and run for 0.75 hrs to run-in the new accessory drive bushing. The run was stopped because of an abnormal sound and vibration; holes for draining the starter and generator drive recesses were omitted. Marks on the accessory drive shaft gear require investigation. The XO-1430-1 total time was now 95:37 hrs, of which 41:30 hrs had been under power and 54:07 hrs motoring.

Engineering: Layouts were completed for a damper between the reduction gear and quill shaft. A replacement parts list to ensure minimum testing time loss was prepared and released to manufacturing. Oil pump layouts were made to increase capacity by 37%. This should provide adequate oil at rated rpm. Further investigation was to be made of engine oil requirements with the objective of using a smaller oil pump. An itemized replacement parts list showing Government liability for all replacement parts used from 1 – 30 Jun 1936 was attached to the progress report. [RD342 RD1676 503-106 O-1430 360225-361231 Vol. 1. 110 – 119.]

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