Crank movement

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worntorn said:
More Jim Comstock info from the data base.
He mentioned that every Commando engine he had gone inside showed clear signs of the bearing outer races spinning in the cases.
Years ago, in an effort to stop that from happening, he tried the Loctite bearing retainer product on some mainbearings.
When those engines came apart later the bearing locker had not held.
He was trying JB weld as a bearing retainer of last resort, but I don't recall if that worked or not.
I think not.
The only way I know to really hold them from rotating for certain, is to stake the bearings with machine screws. I did this on my 1360 motor and it is a bit of a tricky procedure.

Glen
Click to expand...
Slightly off topic but on a Japanese bike with horizontally split cases the bearings are sometimes pegged with a roll pin into a recess
A mate of mine destroyed the gearbox in his fz750 by overtightening the drive chain
He lacked the money to buy the genuine Yamaha bearings so he just bought off the shelf ones
So with a dremmel I ground an indent in the outside of the bearing and cut a piece of silver steel that went into the recess and also into indent to index and hold the bearing
It worked fine
 
Worntorn says: "More Jim Comstock info from the data base. He mentioned that every Commando engine he had gone inside showed clear signs of the bearing outer races spinning in the cases."

That is a shocking observation! What does this say about the basic engineering of the engines? The bores are undersize? The castings are too weak?
 
Stephen Hill said:
That is a shocking observation! What does this say about the basic engineering of the engines? The bores are undersize? The castings are too weak?
Click to expand...
Typical of a steel bearing in an alloy case where the coefficient of expansion difference means that a cold interference fit of 1.5 thou changes with a hot engine to a just barely interference fit. Its also why Loctite does not hold onto the bearing as its subjected to heat cycles with expansion and contraction, when the same heat cycles subjected to a steel bearing in a steel housing the Loctite survives.
 
For clarity....those who recommend the shimming of the bearing outer rather than inner.

This largely depends on the Old Britts shim package right?

And Old Britts is closing down so those who want to follow this method need another source, right?

Or is someone else selling a suitable kit?

On the shelf I have AN shims, but would try the other method if there are easily available ready cut shims.
 
kommando said:
Typical of a steel bearing in an alloy case where the coefficient of expansion difference means that a cold interference fit of 1.5 thou changes with a hot engine to a just barely interference fit. Its also why Loctite does not hold onto the bearing as its subjected to heat cycles with expansion and contraction, when the same heat cycles subjected to a steel bearing in a steel housing the Loctite survives.
Click to expand...
Thanks Kommando.

Reading your reply, means that the tragic destiny of Commandos is to have their Superblends spinning. What about the destiny of the shims sandwiched between case and a spinning bearing? What is Jim Comstock's opinion, because he never made a statement about that ???.
"More Jim Comstock info from the data base. He mentioned that every Commando engine he had gone inside showed clear signs of the bearing outer races spinning in the cases."
 
SteveA said:
For clarity....those who recommend the shimming of the bearing outer rather than inner.

This largely depends on the Old Britts shim package right?

And Old Britts is closing down so those who want to follow this method need another source, right?

Or is someone else selling a suitable kit?

On the shelf I have AN shims, but would try the other method if there are easily available ready cut shims.
Click to expand...

I've never needed to shim endfloat, but I believe some VW Beetle shims fit, and are available in various thicknesses
 
I think it was posted somewhere, Ford nine inch differential bearing shims work, it was easier for me to machine what I needed to the dimension that I thought suitable from high quality shim sheet. (Old Britts had stopped International shipping by then)

There are plenty of online cut to size shim companies also, enter the ID, OD and thickness, press the buy it button.

If bare engine cases were on the bench along with new main bearings on a bike rebuild it seems like it would be a time to consider end float.
Oddly enough I found the bearing outer contacted the crankshaft cheek in one location so it was surface ground.
 
Some mentions of staking the bearing, but from what I've gleaned this method implies a fundamental flaw in the overall design. Swaging may work, but this would not be the right application for that (nor is there enough material in the case I believe).

Does anyone know if this is a problem with Maney cases?
 
Before concluding it’s a flaw in the design, let’s not forget these bikes are all many years outside their designed life expectancy!

Maney cases are much, much thicker in this area, and (I imagine) machined to tighter tolerances, and they’re not 50+ years old. So I’d hope Maney cases would be better with regards to this.
 
Sergio said:
Reading your reply, means that the tragic destiny of Commandos is to have their Superblends spinning.
Click to expand...
Less spinning but more like a slow walk, if you try to increase the interference fit then the aluminium housing just expands and you get back to 1.5 thou interference again. Best fix is to peg the bearing but most engines will operate fine as they left the factory, the issue comes when by installing a bearing cold or some other problem caused by being hamfisted the 1.5 thou is lost.
 
"Reading your reply, means that the tragic destiny of Commandos is to have their Superblends spinning."

I think that's a considerable overstatement. Many (most?) Commando engines are still running just fine on the original bearings. It's not fair to compare a commando as it left the factory with one that has been modified for more power and/or used for racing and then complain that the factory bearings/seating process is faulty. It is also not fair to make the comparison if someone elected to replace the perfectly OK OEM bearings "just because," and the new bearings later failed.

I have seen plenty of repairs or "upgrades" made to engines that failed due to improper work when leaving things alone would have been the "correct" procedure. ;)
 
Far be it from me to contradict Jim Comstock and I wish he would comment on the quotes here - are they really quotes - are they in context?

I've rebuilt several Commando engines and have never found any evidence of the bearing shell slipping. I also can't think of what would make a good, freely spinning bearing have enough torque on the outer shell to make it try to move. Of course a bad bearing is a different story and I'm sure he's worked on many (maybe most) engines that are are a mess.

I've rebuilt many more Triumph engines who also rely on an interference fit for the bearings - no issues.

With the heating required to get the bearings out of the cases, I can't imagine spinning bearing shells - seems like the interference fit would go away over time with a spinning shell.

Kommando and MexicoMike make excellent points.
 
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Time Warp said:
I think it was posted somewhere, Ford nine inch differential bearing shims work, it was easier for me to machine what I needed to the dimension that I thought suitable from high quality shim sheet. (Old Britts had stopped International shipping by then)



If bare engine cases were on the bench along with new main bearings on a bike rebuild it seems like it would be a time to consider end float.
Oddly enough I found the bearing outer contacted the crankshaft cheek in one location so it was surface ground.
Click to expand...

'There are plenty of online cut to size shim companies also, enter the ID, OD and thickness, press the buy it button.'

Really? Seems they are not as simple as that in my hemisphere!!

'If bare engine cases were on the bench along with new main bearings on a bike rebuild it seems like it would be a time to consider end float.'

Well yes, that is where I am going! They aren't bare yet, but they will be!

FYI, I was involved in a race crash and found the crank nut had impacted tarmac, presumably whilst the engine was still running, which ground through the lockwire and rotated the nut loose. So as I put the motor on a bench I idly looked to see what the end float looked like, memory says 'more than before', but this needs confirming. More formal measuring with a dial gauge prior to disassembly yet to be done! Is there any problem?, well I don't know, yet.

Simple searches didn't find either Ford or VW part numbers, does anyone have a more detailed recollection.
 
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SteveA said:
'There are plenty of online cut to size shim companies also, enter the ID, OD and thickness, press the buy it button.'

Really? Seems they are not as simple as that in my hemisphere!!

'If bare engine cases were on the bench along with new main bearings on a bike rebuild it seems like it would be a time to consider end float.'

Well yes, that is where I am going! They aren't bare yet, but they will be!

FYI, I was involved in a race crash and found the crank nut had impacted tarmac, presumably whilst the engine was still running, which ground through the lockwire and rotated the nut loose. So as I put the motor on a bench I idly looked to see what the end float looked like, memory says 'more than before', but this needs confirming. More formal measuring with a dial gauge prior to disassembly yet to be done! Is there any problem?, well I don't know, yet.

Simple searches didn't find either Ford or VW part numbers, does anyone have a more detailed recollection.
Click to expand...

I think there may have been different sizes over the years, but some were definitely 71mm OD

You could contact

https://www.justaircooled.co.uk/crankshaft-end-float-shims-1200cc-1600cc.html

https://www.coolairvw.co.uk/product/021105281/

https://www.machine7.com/contact.php?jssCart=2cb325ec0e90ae8eeb0342181952a4c1
 
SteveA said:
'There are plenty of online cut to size shim companies also, enter the ID, OD and thickness, press the buy it button.'

Really? Seems they are not as simple as that in my hemisphere!!

'If bare engine cases were on the bench along with new main bearings on a bike rebuild it seems like it would be a time to consider end float.'

Well yes, that is where I am going! They aren't bare yet, but they will be!

FYI, I was involved in a race crash and found the crank nut had impacted tarmac, presumably whilst the engine was still running, which ground through the lockwire and rotated the nut loose. So as I put the motor on a bench I idly looked to see what the end float looked like, memory says 'more than before', but this needs confirming. More formal measuring with a dial gauge prior to disassembly yet to be done! Is there any problem?, well I don't know, yet.

Simple searches didn't find either Ford or VW part numbers, does anyone have a more detailed recollection.
Click to expand...

It was some person in the UK who said it was a waste of time making shims and to have them cut by these numerous shim cutters ?
The Ford nine inch shims were only described as that but will be the preload shims which do look similar but do not know the dimensions of them at hand.
#
The bits attached to either end of the crankshaft will have no effect on the end float.
It might be easier to check your engines end float now to see what it is.
I have some spare shims (2 x 0.008" and 1 x 0.010") if two of those will get you to the range needed I can put them in the post to you.
They are of course made in the garage but are made to just clear the fillet in the bottom of the engine case bore and to not extend into the bearing as per the one sitting on the bearing.

Crank movement
 
SteveA said:
'There are plenty of online cut to size shim companies also, enter the ID, OD and thickness, press the buy it button.'

Really? Seems they are not as simple as that in my hemisphere!!

'If bare engine cases were on the bench along with new main bearings on a bike rebuild it seems like it would be a time to consider end float.'

Well yes, that is where I am going! They aren't bare yet, but they will be!

FYI, I was involved in a race crash and found the crank nut had impacted tarmac, presumably whilst the engine was still running, which ground through the lockwire and rotated the nut loose. So as I put the motor on a bench I idly looked to see what the end float looked like, memory says 'more than before', but this needs confirming. More formal measuring with a dial gauge prior to disassembly yet to be done! Is there any problem?, well I don't know, yet.

Simple searches didn't find either Ford or VW part numbers, does anyone have a more detailed recollection.
Click to expand...
If you are considering shimming the outer races and if you measure the end float before you disassemble the crankcases and the outer races are not fully seated ( which is possible if they are rotating in the crankcases), I think you will get a false reading trying to determine the shimmage.
 
It was just a thought based on personal time restraints.
I very much doubt the bearings are creeping rotationally in the average Commando, in a race engine maybe or by someone who simply has to rev to the Made in UK spot on the tachometer a maybe also.

Any slight gap would only add some clearance when the bearing was seated but have to wonder how many folk when they heat the cases to drop the bearings in, add a weight until everything is cold ? (To stop any bearing creep/unseating axially while cooling)
Or do they just get dropped in and left to their own devices which would mean any shim under them was then floating if so and a decrease in end float by default.

s44.jpg
 
Time Warp said:
They are of course made in the garage but are made to just clear the fillet in the bottom of the engine case bore and to not extend into the bearing as per the one sitting on the bearing.
Click to expand...

A very impressive achievement. I can't imagine the thought and effort, never mind the tooling required to produce these shims. Good job!

Best.
 
I'm beginning to wish I hadn't mentioned the subject of outer bearing rotation in cases, especially if people believe I'm misquoting or " taking things out of context". As I recall, it was just an observation by Jim and not anything to get concerned about for regular roadbike use.
The thought was that this is something that occurs now and then , for example on a hot day with a hot engine at high rpm in 2nd gear just before shifting, perhaps the outer race turns a turn or two.
There is no damage left behind, just the sign of some small amount of rotation.

This is not the discussion I had in mind, but the last sentence conveys the same info. A hot case that expands sufficiently for the outer race to " float". While it is floating its not hard to imagine it might turn once or twice.




Glen

 
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