Layshaft BALL Bearing Upgrade - "in situ" - Techniques And Tips Help?

baz said:
I think it was commoz that once pointed out that a chain drive is lubricated by oil
With a film of oil on each pin and roller of the chain it provides a cushion compared to a belt drive
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I can see that, but I‘d say it’s rather minor.

The argument for rubber belts is that the teeth can ‘give’. Which I’d also suggest is minor.

So it’s the poly belts that probably have the least give. In theory.

I think it’s all academic personally though. I’m running belts on 5 of my 6 old Brits. 3 rubber and 2 poly.
 
I agree with kip.
The chain dynamic catenary allows some inertial buffer.
The cog belt has none.

Goes against the romantic old tales, "belts being easier on the transmission", but the facts of industrial drives say the belt offers zero give.

JMWO
 
concours said:
I agree with kip.
The chain dynamic catenary allows some inertial buffer.
The cog belt has none.

Goes against the romantic old tales, "belts being easier on the transmission", but the facts of industrial drives say the belt offers zero give.

JMWO
Click to expand...
Well that’s a different theory to the oil damping effect.

Personally, on a short primary chain, I doubt that there is enough damping / cush / give in a chain to be meaningful.

Belts are easier on the transmission on a Norton due to the reduced rotating weight generally involved IMO.
 
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Synchronous belts have lots of advantages, real ones not just perceived however they really do need to accurately set up for alignment and tension and failure to achieve this results in early failure.
In an industrial setting our guys would use laser alignment and calculate tension with a formula.
They are good and have circa 98% transmission efficiency but it is important to be aware of their limitations.
 
The Velocette I'm in the process of buying has an oem spring shock absorbing drive arrangememt off the crank. The bike is also fit with an aftermarket belt primary drive. No cush drive in rear hub like commando.
 
Tornado said:
The Velocette I'm in the process of buying has an oem spring shock absorbing drive arrangememt off the crank. The bike is also fit with an aftermarket belt primary drive. No cush drive in rear hub like commando.
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That was the more common way, or in the clutch basket, it’s the Commando that’s something of an outlier for the Brit industry with its rear wheel cush.
 
That ramp/spring setup in the primary is used by Harley/Victory/Indian as well.

The hard plastic inserts in the Commando hub facilitate quick wheel removal only. They provide no "cush drive" benefit.
 
Chains don't actually stretch - they elongate. The pins wear as do the rollers and there's a certain amount of "slack in the stack" of pieces from day one - hence the need for occasional adjustment as they wear - and the ability to give a little under shock loads. So they are forgiving in the sense they spread/share the stresses with other components.

Ain't none of that in a belt. There is no play and no elongation, and they are very strong, to cope with shock loads in the system which are (according to Gates) typically much higher than peak motor torque - in the range of two to three times. None of which, bodes well in the long run for weaker and more flexible components in the drive train. That's why I think belts are unforgiving in primary drive applications.

Drive belts are a different story because of (among other things) the arc of motion in the rear wheel and cushioning in the wheel hub.
 
Kip said:
Chains don't actually stretch - they elongate. The pins wear as do the rollers and there's a certain amount of "slack in the stack" of pieces from day one - hence the need for occasional adjustment as they wear - and the ability to give a little under shock loads. So they are forgiving in the sense they spread/share the stresses with other components.

Ain't none of that in a belt. There is no play and no elongation, and they are very strong, to cope with shock loads in the system which are (according to Gates) typically much higher than peak motor torque - in the range of two to three times. None of which, bodes well in the long run for weaker and more flexible components in the drive train. That's why I think belts are unforgiving in primary drive applications.

Drive belts are a different story because of (among other things) the arc of motion in the rear wheel and cushioning in the wheel hub.
Click to expand...
Is a toothed belt absolutely required for a primary? A smooth V-belt might have more shock handling ability, no?
 
Tornado - this applies to drive belts, but a good read for "principles". FWIW, Gates invented the V-belt in 1911.

It is interesting that belt drive is a viable alternative to chain and shaft, but with the disastrous exception of H-D on the Sturgis in the early 80s ...no OEM uses primary belts.

www.cycleworld.com

Carbon Belt vs. Steel Chain Final Drive

Carbon belts are gaining ground on steel chains in the world of motorcycle final drives. We explain the advantages and disadvantages.
www.cycleworld.com www.cycleworld.com
 
If you rub that rubber belt on the gearbox case vigorously it might generate enough heat for the layshaft bearing to fall out.

Old people. 🤣
 
I think some of the first generation production car CVT's(Hyundai?) Used a rubber coated steel belt or chain on the tranny conical "pulleys".
 
Kip said:
Chains don't actually stretch - they elongate. The pins wear as do the rollers and there's a certain amount of "slack in the stack" of pieces from day one - hence the need for occasional adjustment as they wear - and the ability to give a little under shock loads. So they are forgiving in the sense they spread/share the stresses with other components.

Ain't none of that in a belt. There is no play and no elongation, and they are very strong, to cope with shock loads in the system which are (according to Gates) typically much higher than peak motor torque - in the range of two to three times. None of which, bodes well in the long run for weaker and more flexible components in the drive train. That's why I think belts are unforgiving in primary drive applications.

Drive belts are a different story because of (among other things) the arc of motion in the rear wheel and cushioning in the wheel hub.
Click to expand...
As I posted already, on such a short chain, that amount of play is immaterial IMO in terms of providing any effective shock absorption.

And, I’d argue that play can increase the shock upon take up. We all know what a slack chain feels like.

IMO the relative damping properties of chain vs belt should not be a deciding factor in which to choose at all.

If you want a cush, you need to instal a cush drive in the system. Period.

IMO a cush drive is a good idea. But I’ve run bikes with and without cush drives and have never felt or observed any issue or benefit either way.

Only 2 of my belt driven bikes do not have a Cush drive. The most interesting is the T140 because I swapped out a virtually new chain for a belt kit AND in the process lost the cush drive in the clutch. And that bike was noticeably smoother to ride afterwards without the chain and without the cush drive !
 
Forget belt vs chain and cush drive for a second...the focus was/is bearings and shafts and how much flex and stress they might exhibit in use, and/or what it takes to get them to fail. Part of the reason it's an issue in the first place has to do with long mainshafts running through sleeve gears and the flailings of spinning gears in the box, a sprocket, and a clutch - all generating different forces that vary constantly and simultaneously. Stories about bearing failure and excessive bushing motion and wear should say enough about the importance of keeping this flailing and thrashing to a minimum. It seems no more than common sense to maintain properly adjusted primary chains (or belts) and drive chains to provide as much equilibrium and as little strain on the mainshaft as is feasible.

The other motorcycle I have with a very similar gearbox arrangement is a Harley FXR. I've had this machine for over 30 years and learned from experience, that if either chain (or drive belt early on) is too tight or too loose, there will be a leak from the main drive gear (sleeve gear in Nortonese) and/or issues with the needle bearings in the MDG, as a result of the mainshaft being jerked around. When both primary and final drive are adjusted for minimal strain, those issues are resolved and all is well (for 73.000 miles so far).

The point is, it was easier at first to blame the oil seals or the needle bearings than to learn the root cause of the issues. To me, one of the virtues of a "keeper" motorcycle is that once it educates you sufficiently, any issues can be resolved correctly and the bike can be better than ever.
 
Kip said:
Part of the reason it's an issue in the first place has to do with long mainshafts running through sleeve gears and the flailings of spinning gears in the box, a sprocket, and a clutch - all generating different forces that vary constantly and simultaneously. Stories about bearing failure and excessive bushing motion and wear should say enough about the importance of keeping this flailing and thrashing to a minimum. It seems no more than common sense to maintain properly adjusted primary chains (or belts) and drive chains to provide as much equilibrium and as little strain on the mainshaft as is feasible.
Click to expand...
Agreed, hence my point in post #36. Minimising the weight mounted on and acting on the mainshaft is key IMO. And you can only achieve the minimum with a belt drive, and alloy clutch basket, and surflex type alloy plates, etc. The amount of weight you can remove is immense, as will be the reduction in associated stresses (tho such calcs are way beyond my meagre intellect).
 
Well, there is a reason I initially called swapping the layshaft bearing my "winter project". But the one that's got me stymied right now isn't the one I expected!

The process had gone well enough (not counting the need for a thin wall Whitworth socket, since there's no room in there to remove the nuts without one) - right to the point of removing the layshaft.

I was curious as to whether the shaft would leave the bearing in the case or come out with the bearing attached. On MY friggin' motorcycle, the answer turned out to be "none of the above". I heated the case to a relatively uniform 220F with my heat gun and yanked, expecting to have something in my hand afterward. NOPE! NOTHING budged! I tried again - same result. A third time with longer heat time, harder yank - NOTHING!

ALL the literature (and this forum) says this method should work. I can only speculate as to why it does NOT work on my bike. Maybe the bearing has damage and is jammed in place or trapping the shaft or both? Maybe grit of some sort has worked into the crevices? Maybe I'm just a wimp? It's kinda academic at this point.

There has been ZERO indication of any problems during my ownership of this Commando since 2005. I was only doing this job as a "preventative" upgrade and because I'd been led to believe it could be done "in situ".

Now, although there's no obvious evidence of it, I speculate as to whether the P.O. has been in there before my time and used red Loctite, JB Weld, or something as bad when reassembling the box? Once again, kinda academic at this point.

What I'd really appreciate is to know if anyone else has had this ugly issue and whether there is another trick or two to get the stuck parts unstuck? I HOPE tearing the gearbox out is not required. I'm not sure I'm up to that.

I've thought about trying to rig up some sort of puller, perhaps hooked on the gear and leveraged from the case, but I'm not sure how to proceed with that notion. I am sure I don't want more trouble than I already have.

HELP?!
Thanks!
 
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Layshaft bearing removal in situ . Best move is to pull the whole gearbox , which means pull the primary first to do it . Good
opportunity then to replace some known weaker wear items such as kicker pawl , 1 St. gear bush , sleeve gear bushes , all seals . Of course the layshaft bearing is top priority .
In situ , remove every gear you can , toast it up close to the bearing . Gas is good , but I use a powerful heat gun . The gas can flame out from lack of oxygen . Let the heat sink in to the aluminum , then get to pulling out the layshaft from the lower gear box , ( with extreme prejudice ) ( Apocalypse Now ) , using heavy leather gloves .
It's good that it's tight , that means you did not get it hot enough , or the gearbox is still tight to the bearing as original fit . You actually want tight , some develop a crack between the 2 D.S. bearings .
 
220F is not hot enough? What do you grab for "extreme prejudice"? The shaft is too slippery - so the gear?
 
Kip said:
220F is not hot enough? What do you grab for "extreme prejudice"? The shaft is too slippery - so the gear?
Click to expand...
Hotter . Grab the very clean layshaft end with heavy gloves . Pull towards you . Rocking it a bit sideways if stubborn . Get violent . It will pull out . Heat only , because no way to get any cold to the bearing or shaft .
 
Kip said:
Well, there is a reason I initially called swapping the layshaft bearing my "winter project". But the one that's got me stymied right now isn't the one I expected!

The process had gone well enough (not counting the need for a thin wall Whitworth socket, since there's no room in there to remove the nuts without one) - right to the point of removing the layshaft.

I was curious as to whether the shaft would leave the bearing in the case or come out with the bearing attached. On MY friggin' motorcycle, the answer turned out to be "none of the above". I heated the case to a relatively uniform 220F with my heat gun and yanked, expecting to have something in my hand afterward. NOPE! NOTHING budged! I tried again - same result. A third time with longer heat time, harder yank - NOTHING!

ALL the literature (and this forum) says this method should work. I can only speculate as to why it does NOT work on my bike. Maybe the bearing has damage and is jammed in place or trapping the shaft or both? Maybe grit of some sort has worked into the crevices? Maybe I'm just a wimp? It's kinda academic at this point.

There has been ZERO indication of any problems during my ownership of this Commando since 2005. I was only doing this job as a "preventative" upgrade and because I'd been led to believe it could be done "in situ".

Now, although there's no obvious evidence of it, I speculate as to whether the P.O. has been in there before my time and used red Loctite, JB Weld, or something as bad when reassembling the box? Once again, kinda academic at this point.

What I'd really appreciate is to know if anyone else has had this ugly issue and whether there is another trick or two to get the stuck parts unstuck? I HOPE tearing the gearbox out is not required. I'm not sure I'm up to that.

I've thought about trying to rig up some sort of puller, perhaps hooked on the gear and leveraged from the case, but I'm not sure how to proceed with that notion. I am sure I don't want more trouble than I already have.

HELP?!
Thanks!
Click to expand...
More heat. When hot enough it will simply pull out effortlessly. With the gearbox in place as well as the primary, it is very difficult to get the area around the bearing hot. Assuming no Locktite, you must take the area around the bearing to around 220 so take whatever you're measuring to 300-350. Try to keep the heat off the layshaft (yes, I know, damned hard in place). If there is bearing set Locktite, then you need around 500f and if red Locktite, more than that. If you cannot get it out at 300f, you'll have to remove the gearbox. You'll probably need to anyway to replace the sleeve gear seal (or at least remove the primary. A Map-Pro or propane torch is better as a heat gun spreads the heat much more and takes forever - but be careful - they are hot enough to melt aluminum so use a thermometer.

Assuming that you have the right tools, you're well under two hours from having the primary off, gearbox out and the bearing(s) replaced in the gearbox.
 

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