Cush Drive

nkt267

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I remember seeing one in a clutch that would fit easily, but can't remember where.
AMC.Try replacing them without any idea of how to do it. No workshop,no special tools. I was 18 at the time and I can still remember the amount of new swear words I used.
 

BigEd

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I was always led to believe that toothed drive belt do not stretch so don't have a shock absorbing quality. They have a rubber content but I thought that the strengthening fibres in the belt don't stretch so ideally belts should have a cush drive to ease the shock. I don't think that toothed timing belts have a cush drive but maybe the loadings aren't the same as in a motorcycle primary drive. Also if they "stretched" they wouldn't be good for accurate timing. Do the modern machines that run a toothed belt final drive have a cush drive in the transmission somewhere? Any transmission experts out there?
Belt drive, job done.
 
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Howard

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Hi Folks,
I machined 1,5 mm from the inner main bearing and made a new bush with a wider flange to carry the load.

Vincent

PS and by the way, I'll look into a rear left sided 2LS brake to fit, and will put such a damper on the right side

I'd leave the back brake as SLS. My Egli has 2LS front and rear, and on the odd occasion I stop in traffic going up a very steep hill it has NO leading shoes to stop it running backwards - scary.

H
 

Howard

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I was always led to believe that toothed drive belt do not stretch so don't have a shock absorbing quality. They have a rubber content but I thought that the strengthening fibres in the belt don't stretch so ideally belts should have a cush drive to ease the shock. I don't think that toothed timing belts have a cush drive but maybe the loadings aren't the same as in a motorcycle primary drive. Also if they "stretched" they wouldn't be good for accurate timing. Do the modern machines that run a toothed belt final drive have a cush drive in the transmission somewhere? Any transmission experts out there?

Never had a belt primary or secondary drive, so I never considered it wasn't a cush drive as seems to be suggested, but you're right Eddy, properly sized HTD drive belts shouldn't stretch (steel or glass fibre reinforcing cords), so shouldn't give a cush drive effect as we understand it. I think the perceived cush drive is down to the smoother drive characteristics and possibly a very small amount of flex in the teeth on the belt. I know of Harley's fitted with belt final drive and cush drive hubs, but I don't know if they're original equipment, or aftermarket.

H
 

davidd

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It is interesting that we think of chains made of steel as stretching and belts made of rubber as non-stretching. Of course, metal does stretch, but it is more likely the wear in all the rollers that is lengthening the chain. I would also note that chains seem to have a much more difficult time keeping the timing accurate, due to the wear. Belts are somewhere in the +/- one degree area where chains are in the +/- four degree area as I think Mercedes found out.

If you ask: "Is a cush-drive necessary" the real question is "necessary for what?" Racing organizations like them for the safety aspects. They tend not to hurt riders when they break and they tend not to to hurt the bike, which means less oil on the track. If you run a Vincent with a MK2 cam the power is between 4,000 and 6,000 rpm. The power pulses are not exactly smooth, but the street rider may never get above 4,000 rpm. In this range the pulses are quite pronounced.

I do not run a cush drive anywhere on the racer, but I am spinning it fast all the time, even on the starting line. If I had power related reliability issues I would consider adding the complexity of a cush drive as a worthwhile addition. I think on the street, cush drives have proven quite useful or we would not see so many modern bikes using them. My Egli always had one in the Campagnolo rear hub. It is something I would design in to a new Egli as Glen has done. I think there is a lot of "up" side and very little "down" side to running a cush drive. It seems to be a good solution for low rpm stop and go riding.

David
 

vibrac

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I was always led to believe that toothed drive belt do not stretch so don't have a shock absorbing quality. They have a rubber content but I thought that the strengthening fibres in the belt don't stretch so ideally belts should have a cush drive to ease the shock. I don't think that toothed timing belts have a cush drive but maybe the loadings aren't the same as in a motorcycle primary drive. Also if they "stretched" they wouldn't be good for accurate timing. Do the modern machines that run a toothed belt final drive have a cush drive in the transmission somewhere? Any transmission experts out there?

I understnd the 'cush' in a belt aint in the stretch its in the tooth after all whats in a norton clutch centre b great toofs and newby clutches dont have rubber centers (or coffee flavor either, I hate coffee centers :))
 

hrdsuper90

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I think it is a common misconception that a belt has any 'cush' effect, in fact a chain with oil in it's links would have more. If belts had 'give' how could valve timing work on modern car engines (most common use) ?
On my race sidecar's primary, I machined out the front pulley to take a Vincent ESA to protect the Norton box. Chris


the eo
Belt drive, job done.
 

vibrac

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I think it is a common misconception that a belt has any 'cush' effect, Chris


the eo

well somethings smoothing my racer and it started when I threw away the esa and fitted my belt.....

you dont allow a 90 degree twist on set up for nothing and it doesnt get harsher as it gets hotter
 

Chris Launders

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My norvin runs a primary belt/commando clutch and manx rear wheel so no cush at all and is much harsher than my "standard" twin, my 11.50 Brough has a norton clutch and enfield rear wheel both with cush centers and is much smoother still.
Chris.
 
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