Author Topic: pondering clutches  (Read 168 times)

Offline jachenbach

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pondering clutches
« on: 20.05. 2016 01:18 »
In the last couple weeks, I've worked on 3 very different clutches. First, I installed a BSA 4-spring clutch in my A10. Nothing unusual there, and one I'm sure you are all familiar with. Next, I disassembled the Norton Commando clutch. These use a diaphragm pressure plate. Very simple assembly (with the correct special tool). It is held together by a single flat steel spring which winds into a groove in the basket. Today, I replaced the engine in the Velocette, which has a very unique setup particularly in the actuating mechanism.
  The Norton is a very strong, durable unit, and very easy to work on, but as with most of the old Brits, it is a pain in the but to change the final drive sprocket. With the diaphragm, there is no messing around with adjusting springs for a concentric (?) realease. The Velo is an incredibly narrow clutch with the final drive sprocket mounted outboard, so changing gear ratios is quick and easy. Their answer to unequal spring pressure was to use 16 smaller springs (20 on the Thruxton) reasoning that variations would be spread around and even out. Here again, there is no facility to adjust for even lift.
  Having not yet ridden the Velo, I can't comment on how well it works, but love the design. The adjustment procedure sounds like a pain, and I understand they're rather fragile, but why has noone continued to develop and improve the concept? The Norton clutch is my favorite of bikes I've owned and used hard. But the vast majority of non-shaft drive bikes to my knowledge still use basically the same old clutch that's in the BSA. Sure, they've been improved with slipper types and ramps to increase clamping pressure while maintaining light lever feel, but the basic design remains the same. I wonder why? Maybe a case of that's how it's always been done, so why change?

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Re: pondering clutches
« Reply #1 on: 20.05. 2016 09:55 »
I have the two best clutch's in my BSA's. The 51 plunger A7 has the std clutch, never a problem. The cafe has a Notrun diaphragm running dry, it's so light and bites but does squeal a bit. Never had (and don't want to) a Velo apart but the one I rode was great.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7