Monthly Archives: November 2020

Planning for machining the engine cases

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Planning in case??

We’ve petty much finished all of the steel components now, so Bob has been busy mulling over how we’re going to tackle machining the engine cases. While I’ve been reviewing the hand written notes and scratching my head!

It does make sense and doesn’t seem too onerous either. I just hope the patterns don’t take too long, as they’re holding us up.

Looking at transmission and after a good catchup with an old friend I’ve decided to go fully automatic. Modern small cars with CVT transmission have compact boxes presenting many options. I like the idea of not having a clutch level and cable, it will clean up the bars nicely.

Clock on…

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Setup for measuring the runout on the drive side. Currently out by 20 Thou, but not fully pressed home yet. Once I’ve located a large press and finished squeezing them together, the operation can be repeated and the wheels trued.

In many Brit bike factories the truing up process was done by dropping one end of the flywheel assembly onto wooden blocks. The momentum of the other flywheel would tweak it round slightly. This weighs over 50kgs so we’re having a re-think on that one!

Turning the Crank

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The end of the timing side needs a shoulder putting on it due to a design change. (Clearance for the sleeve drive chain links). In order to do this the crank assembly needs to be mounted and spun, which was quite a challenge! The conrod doesn’t clear the lathe bed so it’s been suspended from the ceiling with a bungee, to allow it to move but retain some tension. It’s a full sized turning crank that gives a good idea of what’s going on inside the motor, not something you see every day!!

Setup for checking runout

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When the crank has been finally pressed together, we’ll need to check the run out. Ideally this will be zero, but is something that must be checked if longevity is going to be achieved! (And I do plan on the engine lasting!).

Minor runout could be adjusted with subtle use of a mallet, or for anything more serious machining one shaft. Or even making an eccentric sleeve. But hopefully none of these will be required.

The idea of the v blocks is to mount the whole crank assembly in the bearings on the timing side. The lot can be spun by the conrod and a clock on the other side measures any runout. Easy!