Taper versus spline

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I've never had a sprocket move on my Norton crank, but I have broken a key under a Triumph clutch. The amount of purchase is different The engine sprocket turns about 3 times as fast as the clutch, so the load on the key is one third.
 
acotrel said:
I've never had a sprocket move on my Norton crank, but I have broken a key under a Triumph clutch. The amount of purchase is different The engine sprocket turns about 3 times as fast as the clutch, so the load on the key is one third.
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Ditto - all the 'lapping in' repairs on a previously spun Triumph clutch have been a big waste of time and effort for me: The only effective fix wass to replace the mainshaft and the hub centre.

Interesting point regarding provision of a weak link via the taper & key. However well-intentioned it was I've cursed Triumph for it many times!
Never heard of a triple mainshaft spinning, but lots on the twins
 
B+Bogus said:
Ditto - all the 'lapping in' repairs on a previously spun Triumph clutch have been a big waste of time and effort for me: The only effective fix wass to replace the mainshaft and the hub centre.

Interesting point regarding provision of a weak link via the taper & key. However well-intentioned it was I've cursed Triumph for it many times!
Never heard of a triple mainshaft spinning, but lots on the twins
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Not the best Idea engineering wise but some get the clutch center and shaft broached for a second keyway
Of course the taper should hold it but the second keyway works
 
Actually, some get 2 extra key ways fitted !

It doesn’t seem right really, but it does work.

Best approach IMHO is a new splined mainshaft and clutch centre from Tony Hayward.
 
I've had the keyway split on the bit of a Triumph crank which holds the alternator rotor. I don't know what might happen with two keyways opposite each other.
I think the only disadvantage of the Norton crank taper is the difficulty in getting the engine sprocket off. When I had the carrier made for the Jawa sprockets, I also had a puller made which screws into it. If the Norton engine sprocket had two threaded holes, or an external thread on the boss - it might be easier to get off. I can't remember if the triplex Commando sprocket has threaded holes for a puller.
 
acotrel said:
I can't remember if the triplex Commando sprocket has threaded holes for a puller.
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It does. Generally I've had no big issues removing the engine sprocket with a 'correct' puller.
Incidentally, Ducati bevel twins also have a taper fit engine sprocket. Now that IS a complete b******d to remove!
 
If you are using the single row primary with the Manx clutch, the Atlas engine sprocket has the correct offset as long as you use the Atlas gearbox main-shaft. I bought a TTI box which has the clutch offset to suit the Commando clutch. That is the reason I had the splined carrier made to fit on the taper, so the sprocket floats and self-aligns. It all works OK. You don't need the triplex primary for racing.
 
Mr Degans did a 90 degree key way on my Triumph clutch when I raced. Only had it done once I'd buggered up the original. Dave said he did it on his race bikes (Nige) Still have a clutch center somewhere with two splines. Hate the Triumph clutch so I am with Nige. Tony Hayward mainshaft Norton clutch belt drive. Done
Chris
 
Bernhard said:
Bottom line is a taper shaft will hold providing it is the correct type for the job and has clean mating surfaces and is held on securely by a nut, or bolt that itself has a locking washer-but not always.

Even the boat propellers on big ocean liners and freight ships employ them.

https://sciencing.com/calculate-shaft-taper-7564452.html
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I have never heard of a Triumph crank failing at the spline which holds the engine sprocket, nor have I heard of a Norton Crank failing at the taper. Perhaps neither of them ever get loose enough to cop a beating or the loads involved are not great enough ?
 
RE; "I have never heard of a Triumph crank failing at the spline which holds the engine sprocket, nor have I heard of a Norton Crank failing at the taper. Perhaps neither of them ever get loose enough to cop a beating or the loads involved are not great enough ?"


Well, they will if a sleepy mechanic forgets to tighten up the retaining nut and it comes loose!
 
I think that is how I got the split up the keyway in the parallel part of the crank, which holds the alternator rotor. The rotor came loose and rocked backwards and forwards fatiguing the end of the shaft.
 
acotrel said:
I've got three single row engine sprockets off Nortons. Only one of them gives the correct chain alignment on a Commando with a Manx clutch. How many Norton models have triplex primary chains ? If you are racing and your gearing is not right, you usually go backwards. With a Commando, you don't know how much torque your engine has, until you raise the gearing and the bike accelerates faster. They won't spin-up fast on the throttle.
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FYI the works Norton John Player bikes went to duplex primary chains. . . . .
 
I race old sidecars.Before I started building my Commando outfit,I raced A65/70s and a Triumph.Lap the clutch tapers in properly using grinding paste,and check with engineers blue.Then fit clutch centre to shaft,and loctite the nut with bearing fit-only the nut,not the taper.Never had any more issues with clutches jumping off after that.As any engineer knows,the taper does the driving,not the key,a bit like morse taper sleeves for drills.Thw key only has a load on it when the taper has parted.
 
Taper versus spline
 
The earlier Triumphs have spring type shock absorber on the end of the crank the sleeve fits the new crank. My friend's 650 Triton has both the shock absorber and the cush clutch. The alternator on the end of the Triumph crank of a road bike, can cause the keyway to split, if it loosens. The same would apply to the engine sprocket if it is straight on the spline without a shock absorber.
 
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