Tuesday 19 January 2021

Engine Plates

Engine plates might not seem a very exciting topic …but they are pretty important!

The first engine plates that I ever made were for an ancient Matchless G80 500cc single that I decided to turn into a “boy-racer” back in 1967 when I was 16 years old and for which I had paid £5. To put that in perspective, it took me 10 Saturday mornings of my weekend gardening job to earn that. As I was still at school maybe I should refer to it as a “schoolboy-racer”…. I gave the bike to a buddy of mine when I left home to go to college in 1969 and, amazingly, he gave me back the engine plates 50 years later when he was clearing out a shed at his house.

These were made from a piece of aluminium that I had purloined from a scrap bin at Britten Norman aircraft at Bembridge airport on the Isle of Wight, chain-drilled using an ancient Black and Decker electric drill in my shed workshop, hammered out with a hammer and chisel and then hacksawed and filed to shape. A pretty laborious process! – but it worked. And with clip-ons, home-made rearset footrests and an open mega on the exhaust this bike really was the Dogs Bollocks for a 16 year old.

Anyway, back to today…. Engine plates had come with the SB8 project

but were not of any use for the V-Twin for a number of reasons: The drillings for the crankcase lugs are in different places; the gearbox fixing would be different and one of them was damaged anyway. And there are a myriad of other holes that I didn’t need.

New engine plates would be required and the first step in making these, and indeed many other parts, is to make a cardboard template

This was then cut out and offered up to the bike and after a bit of “cutting and shutting” I got the shape I wanted

The outline was transposed to a sheet of 6mm thick steel using white paint

and then cut out with a plasma cutter and repeated for the 2nd identical plate.

Both plates were then clamped together and the edges cleaned up on the milling machine

and with both plates still clamped together, the holes were drilled to fix the engine to the rear frame section. The location of the rear holes that fix the plates to the frame were drilled after measuring the exact distance between centres from the frame whilst the holes for the engine were located by using a pilot drill through the 7/16” diameter engine lugs.

At this stage, the pieces of aluminium strip that had been used to temporarily support the engine to the front of the frame were removed and the same process was repeated for the front engine plates

The engine is now firmly supported using high tensile steel studs (EN24T) to fix the engine plates to the frame for both the rear and front plates.

The next sub-projects would be to fix the gearbox in place and to attach the magneto.