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Cush Drive

tonythecat

Well Known and Active Website User
Non-VOC Member
A friend of mine who is a VOC member but does not have internet access has asked me if anyone has any info on a cush-drive system. He thinks it was described in MPH in the 60's by a guy called Gordon Griffiths? any help would be appreciated.

Tony
 

ogrilp400

Well Known and Active Website User
VOC Member
G'day Tony,
What sort of info is he after?
Most motorcycles (and cars) have a cush drive some where in their drive train. Harley Davidson Sportsters' being the exception. Either on the crankshaft, in the clutch or in the rear wheel. Honda Gold Wings had one in the shaft drive. It is there to damp out power pulses and make for a smoother transmission of the engines power.

Phelps.
 

Hugo Myatt

Well Known and Active Website User
VOC Member
Rear wheel cush drive.

Gordon Griffiths was a clever bloke. As I recall his rear wheel cush drive did away with the sprocket side brake . The sprocket was mounted on a cast alloy outer plate with protruding vanes and in place of the brake drum was a drum with internal vanes with wedge shaped rubbers between, similar to the Royal Enfield practice. It was a very neat set up. There is an article way back in MPH. The bike was a Touring Rapide with many clever details.
 

Comet Rider

Well Known and Active Website User
VOC Member
Tony,
The newer version of this is called the "Torsion " sproket used by a lot of drag racers to take the shock off the drive train. It's available from the US in a variety of chain sizes, and they will machine the entre to suit your bolt pattern.

Neil
 

Tom Gaynor

Well Known and Active Website User
VOC Member
That's a neat idea. There must be a good few cushdrives that would do. I remember seeing one in a clutch that would fit easily, but can't remember where. Suspect it was Triumph.
Cheaper and easier however to change out the Series C ESA for the Series D, as advised by KTB. I did - it is a far more robust device - and also took the advice of Simon Linford, to use the gearbox to avoid beating the ESA to death. It isn't proof against wilful abuse. That said, mine runs very smoothly even at 30 mph in top, and the Renolds chain is 13,000 miles old, and has been adjusted once. And no, it doesn't drag on the ground...
(Another bit of advice, this time from Trevor, was to avoid mainshaft seals. There's little enough thrust area for the ESA as it is, and reducing it further isn't smart. My Series C ESA, even without seals, was slowly eating the main bearing spool, and the chain was already 1/32" out of line.)

For sale: mainshaft seal kit, bought and never used...

Tom
 
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Vincent Brake

Well Known and Active Website User
VOC Member
all

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
 

Diogenes

Well Known and Active Website User
Non-VOC Member
QUOTE
A friend of mine who is a VOC member but does not have internet access has asked me if anyone has any info on a cush-drive system. He thinks it was described in MPH in the 60's by a guy called Gordon Griffiths? any help would be appreciated.
Tony
END QUOTE

Here is a late reply.

From '40 Years On' pages 215-216, see MPH 348 Gordon Griffiths and MPH 349 A.Lloyd.

I only have experience of riding the Gordon Griffiths bike and it was very much smoother than standard.
It also stood up well to being thrashed all over the Continent, two up.for years.

From Whitakerpedia 2.2-197-16 you can see a brief article and good photo by Gordon Griffiths, MPH 197.
 

davidd

Well Known and Active Website User
VOC Member
Tony,
The newer version of this is called the "Torsion " sproket used by a lot of drag racers to take the shock off the drive train. It's available from the US in a variety of chain sizes, and they will machine the entre to suit your bolt pattern.

Neil

I do not believe that Sertco is making the "Torsion Sprocket" any longer. It is an Ebay item now. They were a machining facility that got into the oil and gas boom. Rad makes a cush drive, but they are about $600. They can be used on the big KTMs, so they are quite strong.

http://www.radmfg.com/Cush-Series-REAR-HUB-125-up-p/radh-eq-1r.htm

David
 

nkt267

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
VOC Forum Moderator
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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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