Crankshaft flywheel taper

[graeme]

What is the angle of the taper on the crankshaft for the flywheel?
I'm rebuilding an RT and there is more damage to the taper than lapping with 600 grit paste can repair.
I'm starting to get a lip or slight edge towards the thicker end of the taper from lapping the flywheel onto the shaft.

The flywheel isn't the original one that has come loose and done the damage to the shaft, but it and the original RT flywheel do not full seat on the shaft. Only 3/4 of the flywheels taper is seated on the shaft.






Make sense?

Any ideas appreciated

Graeme

[Rick]

Can't tell you what the taper is, but I can show how most machinists in the US measure tapers- I'll attach a picture.
You'll need 2 balls- usually from ball bearings- the top ball should be slightly smaller than the large end taper diameter and the small ball should be slightly larger than the taper small end diameter. Measure the distance from the top of the flywheel to the top of each ball, and knowing the diameter of each ball and the distance from the top surface, a little trigonometry will give you the taper.
Rick

measuring taper.jpg

[Eldert]

Hi Graeme

if i am not mistaken the taper is 6 degrees . when lapping a flywheel on the crankshaft taper i put the flywheel in
the lathe and enlarge the smallest part of the taper sligtly

Eldert

[wcorey]

Looks like that band in the center is what's not contacting? If it was all on one end or the other I'd be more concerned but I don't see an issue using it like that. Though I'd take that shoulder/lip down a bit to make sure it can't prevent things from fully seating, you could just put a small chamfer on the flywheel to clear it or file it off the crank.

Bill

[graeme]

See the narrow end of the flywheel, there is about 6mm that isn't contacting the shaft.
The grey colour is the area that is contacting.
I am thinking of removing the slight lip that has started to appear on the thick end of the shaft and lap more?
I've lapped flywheels before and never had a lip appear.

[wcorey]

Oh ok, I thought the lip was on the larger end on the crank and the no contact was that different looking area in the middle. Now that I'm paying more attention and looking closer, I can see the lip on the small side of the flywheel taper and the non contacting area out past it. Now I also see what Eldert means about shaving a bit off on a lathe, would certainly make sense in this case. As it appears that the entire taper on the crank is contacting, then the taper on the flywheel must be longer and you have as much contact area as can be had, further lapping would only move it in on the flywheel. If you can turn/grind/file the lip away so it can't act as a stop, I would think it should be otherwise fine as it is.

Bill

[graeme]

Bill, the lip is indeed on the large end of the crank taper. I can't feel any lip in the flywheel, the small end of the flywheel seem not to be contacting with the crankshaft taper.

The 6mm shiney section of the small end of the flywheel doesn't seem to be contacting with the crankshaft.

The original RT flywheel is the same. (I'll post pictures of it later)

Graeme

[graeme]

This is the original RT flywheel, note the nice design from the clutch.



The taper wasn't contacting at the small end.



I'm thinking the crank shaft has been repaired with weld and that is why the centre of the taper is harder and showing a different colour when it's lapped with 600 grit?????
And perhaps the taper is slightly different to the Mk3 flywheel. (the RT flywheel is loose too)

Eldert, you suggested slightly machining the small end of the taper larger, I haven't heard of this before.
I blued the shaft and flywheel taper and it seems to be tightest in the middle of the taper and also the large end lip on the shaft. It's possible also the small end, but that's hard to say for sure.
It is possibly rocking on the middle and then touching the blue on the small end.

I'm going to try and lap the shaft with a diamond lap to get it closer to an even taper then lap the flywheel on the shaft again.
Never seen this before.

graeme