NEAM's Lawrance J-1 Restoration


The New England Air Museum (NEAM) is fortunate to have a rare Lawrance J-1 engine it its collection. The J-1 has been the subject of several AEHS web site features, including CAD renderings and an AEHS Convention presentation (5.4 MB PDF) by Randy Huff.

While the NEAM was restoring its J-1 in June 1997, Bruce Vander Mark, a frequent contributor, to the AEHS, took several photographs of the J-1's internals. These are presented below.


Nose Case, Accessory Housing and Components. At the lower left is the propeller shaft bearing carrier, which includes magneto drives and mounts. At the upper center is the cam ring and tappet housing. On the right is the accessory housing and its related components. At the lower center is a magneto. Crankcase and Induction Housing. Note that the J-1 crankcase internals are assembled from the front and then covered by the cam and nose cases. Below the crankcase is the induction housing, which we are viewing from the bottom. The induction housing routes the fuel/air mixture from each of three single-barrel carburetors to three cylinders, thereby providing an induction path for all nine cylinders. The carburetors are attached to the three pads, each with a circular opening and four studs, which are seen at the lower center and left of the image. Crankshaft. The one-piece crankshaft was a steel forging. Opposite the crankpin were webs to which the counterweights were bolted. An integral gear at the front drove the cam ring and magnetos. Another gear, pinned and bolted to the crankshaft rear, drove the accessories. Roller and ball bearings were used for main and thrust bearings.
Master Rod. A two-piece master rod with split plain bearings captured the crankpin and was retained by four bolts. The master rod was an "I" section while the articulated rods (upper left) were hollow tubes. Cylinders. J-1 cylinders were aluminum castings with pressed-in steel liners and cast-in spectacle-shaped bronze valve seats. Rocker arms rode on forks that were screwed into head bosses. Fin area was minimal and was not oriented to achieve optimal exhaust valve and port cooling. Fin area was increased and orientation refined as was engine power was increased in later J-series engines.