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Cush Drives #280390
10/23/09 2:05 am
10/23/09 2:05 am
Joined: Aug 2001
Posts: 1,875
California
Ron - in California R.I.P. Offline OP
In Remembrance
Ron - in California R.I.P.  Offline OP
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OK, here is a separate thread on having a cush in the system. This thread also happened here I think a few years ago.. But basically a rubber belt is NOT a substitute for a cush. Just like drive chains, they do not stretch, they wear.. if either system were to be "stretchy" (enough to be called a cush)then they would not last long, nor would the sprockets..

So, why have a cush..? A cush in the drive line reduces "snatch". Note that I said reduces... it won't eliminate it 1oo% in all cases, and of course each bike, system, and rider are some of the variables.

I often see the young hot rodders today, remove the spring clutch disk from their 4 banger hot rod cars and within a short time have broken gear bits.. Yet the hot rodders that leave the cush in, never break those parts..

I think the most clever cush is in the rear wheel... easy to check for wear, easy to replace.. and yes some designs are better than others.

The cush in the clutch like on a Trump is all hidden away.. and usually never get's maintained like it should. All of the parts in that set up wear over time.. But it works good overall, pretty cheap to replace the worn parts.

The crank style cush seems to be the best to me... just can not use a crank type cush with a crank type alternator (well none that I have seen anyway). I did come up with an idea to use the crank cush set up with a belt drive, and I gave that idea to SRM... they have done a bunch of conversions with no complaints (check the SRM WEB site for more info). That said, a crank cush makes running a crank trigger ignition with the cush on the crank a LOT more of a challenge.. Dave is thinking about tackling that one.. We chatted about that yesterdsy... let's see how he makes out..

In the last thread, someone actually came up with a couple of applications where they thought there was no cush... dunno if that was right or not.

Lots of racers run a belt with no cush... Keep in mind road racing is a LOT different than street riding. For some things, racing is hard on some parts, and on some actually easier.. put an hour meter on a racer and compare that to a street bike ridden weekly and there is most of the answer...

Then consider maintenance.. my guess is the average racer does a lot more frequent maintenance than the street rider. Especially things like tranny oil changes and inspections..

Lastly, is the strenght of the drive system.. we know some are better than others. Take the BSA B50, that is a weak tranny.. and the racers usually replace tranny parts often. Someone makes a 3 speed that is a lot stronger than the 4 speed for off road racing. One of these days, I will try to stuff a Trump 5 speed in B50 cases, but it will take a lot of welding for sure.. not a bolt in kit.. (and no kick start).. but if I get it done, watch out for B50's on the track..!

OK, the above is my opinions and experiences... do what you want.. after all it is your bike and your back side...

Cheers..!!

Ron

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Re: Cush Drives [Re: Ron - in California R.I.P.] #280451
10/23/09 2:25 pm
10/23/09 2:25 pm
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This is a topic that racers go around on.The norton twin guys that I said loose alot of beits ,I think could be linked to no cush and for sure gear box problems.The tt gear box is the only box that I have seen that will handle no cush and if you mention cush to maurice he will laugh at you.His stuff works so I can't fight with him about it and he is 80 and im 46 so he 's the man.I am in the process of fitting so f-3 wheels to my vintage tri so I can get tire money in f-3 from Bridgstone and this has a cush in the back wheel , do you think this could cause any problems having two cush 's in the system. I can't see how it would hurt anything myself other then weight.

Last edited by phantom309; 10/23/09 3:05 pm.

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Re: Cush Drives [Re: phantom309] #280465
10/23/09 3:10 pm
10/23/09 3:10 pm
Joined: Aug 2001
Posts: 1,875
California
Ron - in California R.I.P. Offline OP
In Remembrance
Ron - in California R.I.P.  Offline OP
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Hi Tim..!!

Yes, your Maurice is "Da Man.."

And two cush's won't matter... you won't feel a thing... heh..

And yes now that you mention it, the Norton guys do seem to go through belts a bit... well some do. Wonder why..? Old belt..? Lack of a drive side tranny adjuster..? Extended distance between the two pulleys..? Flexy mainshafts..?

Some of the Trump guys run an outrigger bearing.. or is that only on the triples..?

Cheers..!!

Ron

Re: Cush Drives [Re: Ron - in California R.I.P.] #280474
10/23/09 4:19 pm
10/23/09 4:19 pm
Joined: Oct 2003
Posts: 11,138
North Georgia, USA
RF Whatley Offline
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Good write up, Ron.

I think designers are stuck in a hard place between belts and roller chains. Roller chains like to run at slow, constant speeds. Obviously, no roller chain on a bike is meeting either of those design requirements. I get the feeling that roller chains are just barely able to withstand the job requirements on a motorcycle, where they're always running on the ragged edge. The only thing that saves them in the application is that some small amount of "cush" is built into the chain when every link's void is allowed to fill with oil.

Then there are belts, exterior coated in "rubber". The synthetic exterior giving the impression to the unknowing of some level of shock absorption ability, but in actuality having nearly zero due to the multiple steel cables inside. So the end result is that bikes running a belt actually need a larger cush unit, not smaller.

I'm with you in believing that the best and simplest cush units are in the rear wheel hub where massive amounts of shock-absorbing elastomer can be easily stored. This is where 100+ horse power Hinckley Triumphs place theirs, and they have no issues what so ever. On my particular Hinckley, which is now approaching 50,000 miles, my singular complaint concerning the cush is that the rubber mat always falls out of the hub when I'm changing the rear tire. And even this "complaint" has more to do with my inability to stoop over and pick it up than any design flaw. laughing

All this leaves me wondering what the incidence of mechanical repair would be on a classic Triumph if a Hinckley-style rear hub was fitted.

bigt


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA

"Shop Boy" at Rodi British Bikes
Re: Cush Drives [Re: RF Whatley] #280506
10/23/09 6:03 pm
10/23/09 6:03 pm
Joined: Aug 2001
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hampshire, england
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t120mike Offline
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The earlier Triumph Twins had a cush drive on the crankshaft (a cam and spring arrangement) and the later (alternator) ones had the cush in the clutch centre (lots of rubber wedges). Hughie Hancox told me that he once installed both on one bike and the result was very smooth.

One major beauty of belt drives is that the belts don't stretch over time as much as chains, which makes for far less bother with adjustment, but which also makes a cush drive even more vital. I can't understand the dichotomy, there isn't one. Cush drives make chains and belts last longer and reduce wear in the whole drive train. Yes, they can introduce some additional slack or lag between the power and overrun, but so can lots of things!

PS. What I am not saying is that belts are better than chains; they are different and each has its merits and demerits.


mike
Member #: 147
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Re: Cush Drives [Re: t120mike] #281074
10/27/09 8:25 am
10/27/09 8:25 am
Joined: Apr 2009
Posts: 28
NSW, Australia
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Nothing mentioned of the QPD clutch design for triumph using no cush, would anyone care to comment? I realize using a norton or as RF says, Hinkley, rear wheel with cush would no doubt be an advantage but the wording in the the website says what it says.
http://www.quietpowerdrive.com/QPDhtm/PrimaryBeltDrives.htm
Ron I know you can buy outrigger bearings for commandos.

Re: Cush Drives [Re: ] #281102
10/27/09 12:38 pm
10/27/09 12:38 pm
Joined: Aug 2001
Posts: 4,252
Owego, NY, USA
Mark Z Offline
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"One major beauty of belt drives is that the belts don't stretch over time as much as chains, which makes for far less bother with adjustment, but which also makes a cush drive even more vital."

No, not more vital. Chains don't actually "stretch", they incur wear on all the rollers, cumulatively increasing the overall length of the chain. This does not in any way reduce the shock to the drive train when the clutch is engaged. I don't know this for sure, but reason tells me the shock would be less with a belt, sort of like the difference between hitting something with a rubber mallet vs. a hammer.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: Cush Drives [Re: Mark Z] #281146
10/27/09 5:26 pm
10/27/09 5:26 pm
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ca, us
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DMadigan Offline
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Hyvo chains run higher speeds than roller chain. Morse's catalog shows the standard 3/8" duplex chain power capability peaks out at 3000 RPM at a whole 18.2 HP for a 28 tooth engine sprocket. At 7500 RPM it is down to 5.1 HP.
A 1" wide Hyvo chain 3/8" pitch reaches 108 HP at 7200 RPM (the end of the table). However, Hyvo chain is not as good as roller chain under shock load so a damper is needed on the crank and preferably the chainwheel also. When I get around to building the Hyvo primary for the triples I already have a crank damper designed for it.
Racers have less problems with belts because they do not lug their engines. Even on a start they use high PRM and slip the clutch rather than engaging at a low RPM and WOT.
For the ATframe Rickman-Triumph twin I made a Hyvo primary with Norton style clutch. I put the damper in the rear hub. I will see how that fares. The damper has six pots for the cushions. I used drain stopper plugs (cheap, already have holes). The sprocket runs on its own ball bearing with the sprocket studs as the pins in the cushions.


Re: Cush Drives [Re: DMadigan] #281161
10/27/09 7:17 pm
10/27/09 7:17 pm
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Greenock, Scotland
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gearhead1951 Offline
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there is an old gent that used to post her went by th' name beltdriveman ! Mr Leadbeater was cranky , opinionated and some times rude and would go off on longwinded rants about th' attitudes of some other posters ! BUT , when it came to belt drives , th' old gent was one of th' best informed and knowledgeable persons you could find to talk to about th' subject with !

He said essentially that cush was not needed on a racer , but indespenceable for a street machine !

Re: Cush Drives [Re: gearhead1951] #281167
10/27/09 8:03 pm
10/27/09 8:03 pm
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Dallas Texas
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We do not use a Cush on our roadracers . I think beltdriveman was correct about beltdrives on street bikes. Tim is also correct about norton and pre unit belts beIng run to tight. Just like chains better to be too loose than to tight Jack used to say a rear chain ain't to loose if it ain't dragging the ground

Re: Cush Drives [Re: RPM] #281205
10/27/09 10:28 pm
10/27/09 10:28 pm
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Your not going to let that bike collect dust again next year are you?


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Re: Cush Drives [Re: phantom309] #281269
10/28/09 4:40 am
10/28/09 4:40 am
Joined: Aug 2001
Posts: 1,875
California
Ron - in California R.I.P. Offline OP
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Please do not conjure up BDM.. he has a personal agenda....

Now what would be worth doing (some day) is putting a bike with a stock chain (wet primary) on a brake dyno. Then change that same bike to a rubber belt drive, then the Syncoflex belt drive and see if there is any measurable differences between them. Lots of people SAY there is a difference, but no one (to my knowledge) had done that test. I have heard some nubers tossed around, but nothing to back them up... a real test would settle all of that...

Cheers..!!

Ron

Re: Cush Drives [Re: Ron - in California R.I.P.] #281365
10/28/09 8:04 pm
10/28/09 8:04 pm
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Boston, Massachusetts
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John Healy Online content

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To throw another non-scientific anecdotal opinion into the mix... In a conversation with Dave Nourish, I got to talk to Dave a lot working my way through his crankshafts until we found a combination for the 500 that would work, he remarked to the question, "was there any advantage to going to a belt drive?" having the thought that they might be a bit kinder to the crankshaft and the crank would not be so prone to break.

Without great thought he quickly responded, "the guys using belts seem to break a lot more of my cranks." Of course this is not a scientific blind test and the guys using belts could be making a lot more power than people using chains, but I found his comments interesting, if nothing else.

Heck, if I can buy a chain for less than $100 bucks, and then run it several seasons racing, why would I spend $500 plus? I could never figure this out... I can put up with a little oil weep. Heck the clutch hooks up too well as it is now, why would I want a "better" one? To spend money, kaching, kaching, sorry not this thrifty Celt.


Re: Cush Drives [Re: John Healy] #281367
10/28/09 8:38 pm
10/28/09 8:38 pm
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Nashville, Tn.
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T. Sharp Offline
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John, my only question would be 'How many of these belt drives were Newbys with no cush drive?'
I've seen countless roadracers with busted cases, gearboxes, timing gears, etc. that insisted that they didn't need a cush drive anywhere in the system.
Some eventually incorporated one and their problems ceased!

Last edited by T. Sharp; 10/28/09 8:40 pm.
Re: Cush Drives [Re: T. Sharp] #281385
10/28/09 11:05 pm
10/28/09 11:05 pm
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Boston, Massachusetts
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John Healy Online content

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Only speculation, but the Newby belt system seems to be favored with UK racers.

Another consideration could be the initial "hook" up of some competition clutch plates. For example the old Barnett plates are what I would describe having "rude" engagement while the Alto plates almost feel like they are slipping during initial engagement. Both hold HP, albeit the Alto requiring a much heavier spring. The Alto sort-of-has a "soft" engagement similar to what you feel with an car automatic transmission (of course Alto is an o.e.m. supplier of plates for automobile transmissions).

Modern vintage class race tires "hook" up unlike the tires available "in the day." I have been involved racing Triumph 500's in one way or the other since 1960. When I got the first set of Modern race tires for a 500 I discovered all sorts of problems we never had with the old rubber.

As an aside, I was recently reading a study done by a firm hired by the Triumph cooperative about the same time Bob Oswald of QPD belt drives was trying to get them to use his belt drive system on the T140's. The author of the study had little to criticize and considered a belt drive as worthwhile modification. But if you read John Rosamond's book you will understand that all this came along very near the end and very little money was available to source the equipment, get the licenses, redesign the rear wheel for a cush drive and do the testing required to make the change.

Phantom, I know you feel I am anti-belt drive, but I am really only more than a tad thrifty. I think your dad would have understood... By the way how is mum?
John


Re: Cush Drives [Re: John Healy] #281396
10/29/09 1:33 am
10/29/09 1:33 am
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John, Im one of the thrifiest guys you will ever meet mainly because of Dad.I would not have gone to a belt but kept breaking chain adjusters where the I is bent in the adjuster and slides over the lug in the cases.I started to get old ones out of cases at D&D and they would last well but the repro ones would break way to much and knew it was a matter of time before a chunck got caught in the cain wheel and put me on my head.This would happen with a new chain and very little ark on the adjuster.Marino gave me my first belt drive and I gotta say I would never use a chain on my race bikes again.Both tom and myself have had unbelievable results from them and the clutches. I too am a firm believer in a cush of some kind even on a race bike.I will never knock a man that tries to make due with what he has.Mom is doing well and in Fl for the winter.


Tim Joyce
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Re: Cush Drives [Re: phantom309] #281519
10/29/09 8:07 pm
10/29/09 8:07 pm
Joined: Aug 2001
Posts: 1,862
Elko, Nevada USA
dave - NV Online content
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There's something important I've not seen mentioned in this discussion on cush drives ..
A basic need for a engine cush drive is to absorb the changes in crank rotational speed due to the acceleration/deceleration during the engines 4 cycles of operation.
The crank speed increases during the power and exhaust strokes and then slows it's rotaion during the intake and compression strokes.

FWIW..
We have a Tony Hayward 30 mm belt drive on the Goldie dirt tracker which uses the (heavy!) OEM BSA/Tri 3 spring clutch rubber cush center. The engine belt pulley allows for a straight forward ignition crank trigger installation. With a GStarRon sealed clutch bearing modification this set up (now) works OK.

Getting a bit drifty (with age?) and needing to replace the worn primary and clutch assy etc., I've installed a Newby belt drive in my sorta fast road Gold Star 'special'.
There's no cush in the Newby drive, but I intend to modify things to incorporate the OEM GS cam type cush in the engine pulley. The 'trick' will be to fit both the cush pulley and a ignition crank trigger.

Pal Ron has mentioned SRM fitting a cush to a belt drive pulley...
You may be interested in a little story about this. When we rode down and visited SRM in Wales (yeah!) some years ago their crew gave us a 'grand tour' of their impressive facility including the new dyno cell. They had their 850(?) A65 racer up on the dyno and gave us a demo run. We were chatting about this/that and they mentioned solving a strange harmonic engine vibration by fitting a engine pulley cush drive. hmmmm.
They now are doing this for their customers. Are there any US machine shops familiar with doing this work?


dave - NV
Re: Cush Drives [Re: dave - NV] #281562
10/29/09 11:16 pm
10/29/09 11:16 pm
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HolmeSlice Offline
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Norton Guy alert,

I do frag/break belts from time to time. Superior torque I suppose!! smirk

And I'm running a TT box, so not worried much about the gearbox, but know these belts would last longer with a cush.

I use a T140 4-bolt rear hub on my Seeley Norton race bike and have full compliment of 11 sprockets for it. I would love to figure out how to fashion up a cush drive without having to modify (or replace) all my sprockets. Currently I have the sprocket spaced out approx 3/8" away from the stock hub shoulder. Wondering if this 3/8" could be used for some sort of cush. What DMadigan did was beautiful, but would require more width than I have, and new sprockets.

Any ideas?

Thanks,


Last edited by HolmeSlice; 10/29/09 11:21 pm.



Re: Cush Drives [Re: HolmeSlice] #281573
10/30/09 12:03 am
10/30/09 12:03 am
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phantom309 Offline
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Originally Posted By: HolmeSlice
Norton Guy alert,

I do frag/break belts from time to time. Superior torque I suppose!! smirk

And I'm running a TT box, so not worried much about the gearbox, but know these belts would last longer with a cush.

I use a T140 4-bolt rear hub on my Seeley Norton race bike and have full compliment of 11 sprockets for it. I would love to figure out how to fashion up a cush drive without having to modify (or replace) all my sprockets. Currently I have the sprocket spaced out approx 3/8" away from the stock hub shoulder. Wondering if this 3/8" could be used for some sort of cush. What DMadigan did was beautiful, but would require more width than I have, and new sprockets.

Any ideas?

Thanks,

sell me your wheel and sprokets and put a honda wheel on that junk yard dog.he, he, he.I think peckett makes one for the tri wheel .your friend pim


Tim Joyce
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Re: Cush Drives [Re: phantom309] #281581
10/30/09 12:51 am
10/30/09 12:51 am
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DMadigan Offline
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With the T140 hub you have at least 1/2" between the face and the spoke flange. The damper could overlap that. With the 3/8" spacer you probably have enough for a damper. The sprocket bolts would have to be moved outward. Unless your sprockets are Swiss cheesed, there should be room elsewhere for the bolts.

Re: Cush Drives [Re: DMadigan] #281589
10/30/09 1:32 am
10/30/09 1:32 am
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HolmeSlice Offline
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Thanks Dave, I'd never thought about using the area around the hub. Good thought. Unfortunately my sprockets are cheesed. See here: http://www.shelbynyc.com/nycnorton/DaytonaBound021609.jpg

I wonder if the hub could be turned down to allow more width? As it is I can't space the sprocket out much more before it'll foul the frame, and more offset is not an option as the hub is already pushed over to the right almost as far as it'll go with my current caliper hanger acting as the only spacer.


Pim, what do I do, just type "peckett" into google and see what I get? I need some deets, homey!




Re: Cush Drives [Re: HolmeSlice] #281618
10/30/09 7:29 am
10/30/09 7:29 am
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DMadigan Offline
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Looks like there is plenty of space between the holes for mounting bolts. I measured my hub (I added a spacer in the center to eliminate the dished sprocket). The hub is about 4" diameter outboard of the spokes and the through bolts are on a 3.5" circle. How much space do you have between the sprocket and swingarm at the bolt circle?
Another method is to use the holes in your sprockets for the damper cushions. Probably would need a steel tube to spread the load. You would have an outer cover plate that captured the pin drives with a similar inboard part bolted to the hub. The sprocket with tubes and cushions would slip over the pins. There are thin cross section ball bearings that can be used to take the thrust but if nothing else, the sprocket centre could run on a bushing.

Re: Cush Drives [Re: DMadigan] #281656
10/30/09 2:26 pm
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HolmeSlice Offline
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The Hood
Unfortunately each of my sprockets is marginally different than the next due to their decreasing size. The lightening holes don't line up sprocket-to-sprocket, so using them to locate cush rubbers is not an option.

My spacing is as far outboard left as it can go before the chain starts fouling the frame. And I don't have any remaining offset left to the right, so I'm sorta stuck with this 3/8" to play with.

Steve Maney makes a really nice piece for the T140 hub here:

http://stevemaney.com/products/Cush%20drive%20unit.jpg

so it certainly is possible (as we all know), but this would require all new sprockets, which are usually $1.25 per tooth from sprocket specialists.


Just trying to do something on the cheap, as I've dumped all my spare cash into my motor to get that elusive 47hp to go out and beat Timmy next year.


Last edited by HolmeSlice; 10/30/09 2:39 pm.



Re: Cush Drives [Re: HolmeSlice] #281669
10/30/09 3:36 pm
10/30/09 3:36 pm
Joined: Jan 2004
Posts: 3,568
ca, us
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DMadigan Offline
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DMadigan  Offline
BritBike Forum member
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Joined: Jan 2004
Posts: 3,568
ca, us
Looks to be essentially what I was describing. I hope the cushions are larger than the black area around the bushings. Presumably the damper bolts on the hub and the sprocket runs on the ball bearing beside the hub with the spacers? I am not familiar with the T140, did it have an offset sprocket like the T160?


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