G80CS flywheels - mild steel ?

[rgregory]

Are the competition flywheels only mild steel ?

The timing side axle bore measures 25.50 mm

A NOS shaft measures 25.52mm - presumably for approx 5 thou fit in an inch bore.

It appears the flywheel hole is oversize, which would happen if it had yielded.

Even case hardened Jawa speedway engine flywheels are only rated for 3 assemblies at 0.12mm fit. Then they need oversize shafts.

Does anybody have a drawing of the flywheels in case I have to machine up some new ones from chrome-moly ?

Cheers,

Rob

[Biscuit]

5 Thou. interference fit seems rather excessive.

[T]

you could get the shaft hard chrome plated and reground, instead , it could be a cheaper option than getting parts remade . or find anuvver cranky ! - 25.052 millimeters ? wot ! no imperial ! ! ! thats 1.0047 in. it does sound tight . what are the specs in the manuals ? anybody ?

[rgregory]

quote:
you could get the shaft hard chrome plated and reground, instead , it could be a cheaper option than getting parts remade . or find anuvver cranky ! - 25.052 millimeters ? wot ! no imperial ! ! ! thats 1.0047 in. it does sound tight . what are the specs in the manuals ? anybody ?


I'm guessing standard hole 25.40mm.

Jawa 889 uses crankpin interference specs 0.11/0.13 mm.

That would put a Matchy shaft at mid-tolerance 25.52mm - exactly what I measure on a NOS axle.

What makes me worry more, is that when I dismantled the crank, the axle had worked its way inward about 0.5mm and the conrod had rubbed the end. However, there was still huge end-float on the timing side - work that one out !!

When I put the crank in the 30 ton press, the old axle popped out before I could even get a pressure reading. This is confirmed from the mere 0.02mm interference I measured.

I am now looking for an excuse to use my new BIG lathe (aha !).

Cheers,

Rob