Not a "Cush" Drive

I have come to the conclusion (opinion) that the Commando rear wheels are not really cushion drives.

I believe the context is that the Commandos needed something in there to allow the "quick release" rear wheel while leaving the sprocket, brake drum and chain in place on the Commando. The Clymer publication for service and repair calls the little plastic thingies "plastic shock absober elements" but I am convinced that although they may provide an ever so slight cushion, the little plastic insert thingies in the wheel hub are there (context) to eliminate the metal to metal fretting and clunking; nothng more.

As a contrast, the GRIMECA rear hubs of the period (hubs off of the Ducati 750/860 series) had a single axle and a large rubber spider. I would consider the GRIMECA as a cushion hub.

100% agree.

It is a sorry attempt at best. Always wondered why they bothered. Why not
use some sort of metalastic bush, like they once used in the BSA swinging arm
or to mount the handle bars on a Trident?
Well because it cost a few P more I suppose.
Maybe madass will run up a cush and drum so we can at least feel like
our poor old pre MkIII's have some driveline relief.

Onder said:

Maybe madass will run up a cush and drum so we can at least feel like
our poor old pre MkIII's have some driveline relief.

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Yes, agree but personally not convinced it is necessary.

I started this as a seperate thread as I did not want to cloud up madass's endeavors. The true cushion certainly will reduce shock loading.

I did run a GRIMECA on my Commando racer. The Featherbed racer runs the Commando split axle and the Seeleys are all solid drive.

Seems like a non issue with all three. Somehow I think the closer gear spreads on the five and six speed Seeleys must be kibder to the drive train.

I use single row primary chain with the older racing clutch on my Seeley. The centre has a spider and rubbers. I worry a bit when I cook the clutch during starts, but it all seems to stand up alright . My engne sprocket is off a Jawa speedway bike. I had a s plined hub made t o fit the Norton taper. All that is required to change the sprocket is to take off the chain, and pop the circlip. I did that to allow for the difference in length of the gearbox mainshaft , as I'm not using the commando clutch. I would not run the bike without a cush drive somewhere in the train.

acotrel said:

I would not run the bike without a cush drive somewhere in the train.

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Why? Is there a demonstrated problem with riding/racing without a cushion. There are plenty of Commando based racers out there that do not use a cushion drive.

well, I am sure no expert but I do remember Heinz telling me that when Joe Berliner brought in the first batch of Commandos to New Jersey that they were hit with two major "warranty" issues:

One was the headstock frame breaking, Heinz said they had to round all those bikes and ship them back to England

The other was the issue of gearbox breakages that Heinz told Norton was due to the lack of an absorption through the drive train, he recommended the rear hub be changed to having "rubber snubbers" as he called them

I have no way of knowing if any of this was true, just repeating my memories of my talks with Heinz Kegler

At Andover in the late '60s there was a building full of dismantled Commandos. I was told that they all had frames that were liable to break and were returned from the US. These were the ones mentioned above. All the frames had a frame tube cut with a gas axe and sent to the scrap heap. The rest of the bits were built up into new redesigned frames. There was an exercise to redesign the cush drive set up, but I don't know what happened to that.
In the same building as the returned Commandos were the bits salvaged from the old AMC factory at Woolwich. Including the last attempt by Woolwich to design and build a replacement for the Atlas. As far as I remember it was an 800cc vertical twin with double overhead camshafts, driven by a 4 foot long camchain which ran in smallish diameter tubes. The motor sounded like a cement mixer because of the camchain rattling around in the tubes. I don't know what happened to that bike, which was complete and rideable. It's probably in someones collection somewhere gathering dust and rust.
They also had the complete AMC drawing stores going back to the early 1900's.
cheers
wakeup

As far as I remember it was an 800cc vertical twin with double overhead camshafts, driven by a 4 foot long camchain which ran in smallish diameter tubes

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yes, Heinz talked about that bike and motor being strictly experimental

He said he rode it when Norton sent it over to Berliner

other than not thinking much at all, he did say it vibrated a lot and the motor felt "awkward"

This is from Steve Maney's catalog about his cush drive unit. It seems racers worry about breaking things while people riding street bikes are more concerned with wearing them out. It would be nice to ask somebody that rides a MkIII and pre-MkIII if they notice any difference in the feel, especially if they do any clutchless upshifting.

"MANEY CUSH DRIVE UNIT
Those of you who have had broken gearboxes will already know that every drive train needs some kind of shock absorbing device, and even though the belt in a belt drive system is made from rubber, it does not provide this service. Well, the good news is I have decided to manufacture in volume the Cush Drive Unit I have been using on all my racers since 1995."

BTW, a theory was floated on the BritIron list that the chain drive primary actually has more of a cushioning ability than a belt because the small oil filled spaces between pins and bushings of the chain, when added up on the free run section, gives more give and take to the chain.

Either chain or belts can transmit the peaks of shock loads to do dirty deeds. Chain drives can have shock absorbers in their tensioner rather than cushion in the shafts. Its not just big twin throbbers that can use some dampening poor ole Honda 4's did too so got scabbed on damper upgrades.

http://manuals.sohc4.net/CB750SB/750_32.pdf

the P800 prototype is on display at the National Motorcycle Museum
http://www.flickr.com/photos/39648370@N06/6667620369/

1up3down said:

The other was the issue of gearbox breakages that Heinz told Norton was due to the lack of an absorption through the drive train, he recommended the rear hub be changed to having "rubber snubbers" as he called them

I have no way of knowing if any of this was true, just repeating my memories of my talks with Heinz Kegler

Click to expand...

Well the resulting design with hard plastic thingies would have been (in my opinion) a flacid attempt at fixing a problem that may have existed. Even with the "cush" drive there was still gear box breakage. So either the alleged cush drive was under designed or was for easy removal of the wheel. My thoughts are it was designed for ease of removal of the wheel. I am just saying that if one were to attack a drive train failure problem, the cushion would have been more substantial and robust. It just does not appear to meet that standard.

The design is certainly suitable for eliminating metal to metal fretting.