Crank Taper

We are in process of reverse engineering the taper on the end of the crank. We are building a electric start conversion and belt drive system for CNW.

We have used our CNC machines to get accurate (well pretty close anyway) measurements of the taper. We plan to make tapered blanks and "blue" the fit to insure correct taper angle and depth before starting production on the prototype sprokets.

All this being said, I was wondering if anyone out there had print dimensions of the taper (preferably the sprocket female taper, and not the crank male taper), both included angle and ID's at beginning and end of taper.

It would be nice to compare print dimensions (if anyone knows the specs) to what we get in our metrology analysis.

Thanks in advance

John

I recently had a primary carrier made to hold a JAWA speedway engine sprocket - the taper on the Norton crank was 5 degrees. The main problem you will have is determining the depth of the taper so your pulley doesn't sit too far towards the crankcase or out of line with the clutch.. If you have got some old dominator and ES2 engine sprockets, you might try them on the crank and find out which depth is best. There is a variety of tapers amongst them. The main thing is probably getting alignment of the engine pulley and the clutch as long as you've got clearance behind the engine pulley..
I'd take the whole bike to the machine shop and make the engine pulley to suit, using a straight edge across the clutch.

I recently made a new crank pulley from an off the shelf item. The angle ended up at 5 degrees on the compound slide, but as I did not set this with a sine bar I cannot guarantee it is exact. It would seem reasonable to assume that Norton used a whole angle. Sorry I can't give you the major dia. but the part is fitted to my bike.
Martyn.

As such conversions have been available for Norton and Triumph twins for several decades from Quiet Power Drives in the USA why are you bothering?? I understand it is a seriously long learning curve....unless of course you study how others have done it previously and 'improve' upon their hard work........... but dont let me discourage you!!

J. M. Leadbeater said:

As such conversions have been available for Norton and Triumph twins for several decades from Quiet Power Drives in the USA why are you bothering?? I understand it is a seriously long learning curve....unless of course you study how others have done it previously and 'improve' upon their hard work........... but dont let me discourage you!!

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The reason we want to start from scratch is because we have found some of the available belt drive units not fitting properly on the crank shaft. We would rather not assume that something is sized correctly just because it has been around for awhile.

Sure it is a learning curve but one we are willing to consider since we set out to make this kit as good as we can.

Matt / Colorado Norton Works

www.coloradonortonworks.com

Thanks for the feedback. We also got 5 degree taper in our inspection (actually we got 4 degrees / 59 minutes / 55 seconds )

I think belt drives are really lovely things . However I use single row primary with the older style Norton clutch. If you are racing it is essential to get the gearing correct for the circuit. So I use splined floating JAWA speedway sprockets on a special carrier. All it needs is the nut undone and the chain dropped and the sprocket slips off. In actual fact these days I only ever ride the bike at Winton Raceway, so it doesn't really matter. However fitting a belt primary is expensive and it would add that bit of difficulty in changing the gearing if I ever wanted to race elsewhere.