A10 crankshaft spline

[Slippery Sam]

Richard - no, I have no history on the crank and it didn't come with a cush drive.  There is quite a bit of wear - but it's just too big a job to address - I have to give it a go as it is.  From accounts, this is not un-common and others have successfully fitted belt drive pulleys - so onward and upward.
The pulley it's self is a good fit on the shaft (shaft diameter inside and outside the groves) and is thight on the wider section.  I got it good and tight and have a lock screw on the crankshaft end nut - so it feels good.

Will monitor and report back in a while.
Raymond.

[RichardL]

Raymond,

Sorry, I didn't mean to suggest that it was unusable. I was really just trying to satisfy my curiosity regarding how it happened. I haven't seen it before, but I'm far from the most experienced here in terms of number of bikes built. However, I may be the most experienced at apologizing. 

I wonder if anyone can comment on whether, or not, belt drive pulleys provide "cush" action.

Richard L.

[bsa-bill]

Think I read somewhere a cush drive was NOT recommended with a belt drive.

However I do read things with varying degrees of accuracy.
I also read things and miss the obvious (like Raymonds mention of his belt drive)

[RichardL]

Bill and all,

I am making the assumption that the belt is not stretching to simulate the cush function. You wouldn't want the belt to stretch anyway. So, if you don't need cush for a belt, why have it for a chain? As I take it, the purpose of the cush is to keep clunks and thumps at the clutch (from hard shifts, etc.) from being reflected back to the engine. There is probably a better way to  describe this and I am sure I am missing something. If I'm correct, the belt does nothing for this. Also, it seems to me that a dry clutch is more likely to need cush than a wet [or somewhat wet] clutch.

Dunce cap at hand and ready to be schooled if I am all wrong.

Richard L.

[Slippery Sam]

I do have to hold my hand up - after re-reading the original thread start - I mentioned Bob Newby clutch and pulley - but failed to mention belt in the initial post - so my appologies.
There is no way to have a cush drive on the BN system - the pulley its self is the full width of the old spring drive.  Other sytems may well be different.
I do think the belt does provide a little cushioning - they are tough and don't stretch all over the place (and in fact you have to be careful they don't end up too tight or that causes problems, especially when hot) - but will cushion more than a chain though - but not a lot.
The motor, gearbox and rider's gear changes are going to be so silky smooth - it won't need a cush drive 
I guess there are hundreds of millions of bikes out there with no cush drive, including race bikes and direct drive with a lot more power (160bhp more power) that manage okay without a cush drive - I'm sure we'll be fine.  I'll be riding like a nun anyway 
Raymond.

[bsa-bill]

I do have to hold my hand up - after re-reading the original thread start - I mentioned Bob Newby clutch and pulley - but failed to mention belt in the initial post - so my appologies.

Thank you for that Raymond, my senility put back for a little while (perhaps)

[RichardL]

...but will cushion more than a chain...

I was aware of the configuration on the Newby clutch. I don't think I want to debate whether or not a cush mechanism was ever necessary. Maybe it isn't/wasn't. Also, no debate over smooth shifting [though shocks can come back to the engine with the clutch (not lever) engaged]. However, I don't think I agree with the quoted line above. The belt can't be designed to stretch and, to my understanding is woven (or "belted) with steel wire to assure it does not. This said, completely envious of your Newby clutch.

Richard L.

[chaterlea25]

Hi All,
Sam, Who did the roller conversion? and why did they not see the worn splines?

Worn splines are very common,  resulting from the cush drive nut not being tightened properly
I have had several crank splines repaired by SRM

The debate on cush drives could go on forever?
All modern bikes have cush drives usually in the rear wheel
Even shaft drive Beemers and guzzis have them either in the gearbox or drive shaft
My 1925 Chater Lea has one built into the clutch drum using rubber discs

Belt drives are rigid ! no give in them 
SRM did offer a conversion converting the cushdrive to pulley
Some belt drives retain the Triumph type clutch inner drum that  incorporates a cushdrive

John

[kiwipom]

hi guys, just looked up `Chater Lea` never heard of them but very impressive in their day, cheers

[RichardL]

John,

Thanks for confirming my thinking regarding the belt. I don't think I've seen the insde of a Newby clutch, so, as far a I know, the cush could be built in there.

Richard L.

Edit: So I looked at the pictures and no cush. Saw a couple of pictures of belt sprockets converted with inserts and, also, one setup here on the forum where the belt sprocket is tagged to the original chain sprocket so the ramp-and-spring action is still happening.

[Klaus]

Hi at all,

this BNR belt has no steelliners, such as from Norton belts. Cuchdrive,  Cluthabsorbers or any other dampers in wheels.
What the heck, I can tell having no problems with BNR or NEB belt drives at all my bikes. Riding thousends of miles, plug, play and forgett, I does nt care about, its still running.

There where only three times a belt was broken on the Racebikes, the primary is open, and so the belt collect small stones and give them a perforation and so the belt tear like a cut.

I have seen other belts looking like clutter with damaged pully and clutchbaskets.

Dont think about, ride it. Belt is a good decision


cheers Klaus

[muskrat]

I agree with Klaus.
 With the amount of (or lack of) tension recommended for the belts is enough to give a little chush. Mine gives no snatch on roll off, snap on throttle.
Cheers

[RichardL]

Well, maybe I should stay out of this, having zero belt-drive experience, but my curiosity continues.

Question for Klaus (or anyone) regarding steel wire reinforcing of the belt. It seems Klaus is saying no steel in the belt but I'm not completely sure that's what he means. I AM sure the belt is not supposed to stretch.

Then, there is the point of belt slack providing cush. Isn't the belt always in tension, either on the top or bottom run, and doen't this apply to chains, as well? In any case, I'm having trouble seeing yanking on the belt or chain as equivalent to cush.

Finally, there is the issue of what I think is an unusual amount of spline wear that I have guessed is due to lack of cush. Anyone disagree that this is the likely cause?

Finally, finally, the experience of two race riders with regard to the benefits of cush, or lack thereof, might be very different from us joy riders. Is it unreasonable to think that race riders have an expectation of frequent engine and clutch rebuilds on their race bikes?

Finally, finally, finally, I am not ignoring or disagreeing with Klaus' heavily experinced recommendation for belt drives, just curious about open questions.

Richard L.

[Greybeard]

...no snatch...

No snatch!? 

[Klaus]

Well, maybe I should stay out of this, having zero belt-drive experience, but my curiosity continues.

Question for Klaus (or anyone) regarding steel wire reinforcing of the belt. It seems Klaus is saying no steel in the belt but I'm not completely sure that's what he means. I AM sure the belt is not supposed to stretch.

Then, there is the point of belt slack providing cush. Isn't the belt always in tension, either on the top or bottom run, and doen't this apply to chains, as well? In any case, I'm having trouble seeing yanking on the belt or chain as equivalent to cush.

Finally, there is the issue of what I think is an unusual amount of spline wear that I have guessed is due to lack of cush. Anyone disagree that this is the likely cause?

Finally, finally, the experience of two race riders with regard to the benefits of cush, or lack thereof, might be very different from us joy riders. Is it unreasonable to think that race riders have an expectation of frequent engine and clutch rebuilds on their race bikes?

Finally, finally, finally, I am not ignoring or disagreeing with Klaus' heavily experinced recommendation for belt drives, just curious about open questions.

Richard L.

Hi Richard,

for you I read in the producktion line from the belts I drive.
They are lined with a glascord tensioncord, to avoid streching
Norton or Triumph belts, I gues they are Harvards have stainles steel wire cords inside.

I m lucky if a belt fails, that there is no wraping the wire cord around the clutch or the pully.
It s only a few minutes to fit a new one.
In my tankbag is every time a spare belt but all the years I dont use a one.

About the tension, I mm sure in other engieneering the tension is much stronger.
But in case driving on a cluth the tension had to be low.
By running the engine and chlutch get hot and so the pully and the chlutchbasket, its minimal in extension but the belt get tighten.

Finally, this spline wear can only be done by a losen chush drive.

Finally, Finally...hmmm I do a hight amount of milage every year ( about 20.000 miles) with my beesas, and I think its a big advantage to drive the belt.
For rider how only puddle around the block, with a low milage can save the money for this goody.

Finally, Finally, Finally, hope I could wash away any doubts.


cheers Klaus