Stuart No 1 - Main Bearings

The main bearings needed to be in-line and parallel to allow the crank to run smoothly. This was achieved by boring the bearings in situ on the sole-plate.

However, before this the basic shape of the 2 bearing halves was machined leaving the final honing to be done in-situ at the end.



First the 2 bearing tops were placed in the 4 jaw (one at a time) and the lower face was turned to give the final thickness of the bearing mountings.









The 2 upper bearing halves were stuck together using double-sided tape and they were set to run centrally in the 4 jaw chuck as shown below. In this setting the round profile of the bearing was turned to size and the shoulder of the bearing clamp was also faced square. Next the assembly was placed in the 3-jaw chuck clamped by the round profile just turned. The second shoulder was now turned to size and the other side of the bearing clamp faced square as before.









These parts were now put to one side and the bearing bases were machined. These parts were clamped and turned in the 4-jaw chuck to make perfect 6 sided shapes.









Next the top and bottom halves were made into pairs and stuck together using double-sided tape. The 4-jaw chuck was used to turn each pair of parts and then centre drilled and drilled undersize to 3/8" diameter.

An this setting the thickness of the bearing was set. The shoulders on the outside of each one were made to the plans but the inside shoulders were machined to suit the off-set of the engine standard.









Each pair were clamped on the vertical slide as shown on the right to drill the holes for the oil cups and the 2 clamping bolt holes.









The vertical slide was then used to mill the channel in the sides and lower face of the bearing using a milling cutter of 15mm diameter.

Equal amounts were taken from each side.









Next I returned to the sole plate and cut the bearing supports to the thickness of the channel just cut by my milling cutter. See the sole plate page for this detail.

Finally the bearing was assembled in the sole plate and the 2 holes drilled and tapped to take the 2BA stud.



To bore the bearings to the final size and to ensure they were in line, a small boring bar was used. The sole plate with the bearings screwed in place was packed to the correct height and adjusted square.

The boring bar was used to make the holes parallel and then a reamer was used to smooth the working surfaces to final size.









Once the axle was a snug fit in the bearings, the con rod and axle were put in place and bedded in by hand using Brasso. Once a tight running fit was made the con-rod was removed and the lathe used to bed in the axle to a smooth free-running fit.













Stuart 1 Index