tranny input shaft

[roger 04 rt]

Here u go

Thanks! The key thing is that the engine torque transient is damped well after the spline coupling. Once the spine is loose those every cycle engine transients tap away at the spline hub interface.

 

[cele0001]

Ha Ha Yes..............I don't have any gold bars for my retirement

Can I have a close up of Minotaur's hoof if you have it handy

 

[cele0001]

Thanks! The key thing is that the engine torque transient is damped well after the spline coupling. Once the spine is loose those every cycle engine transients tap away at the spline hub interface.

And I think this is the key. Once the process starts it is highly unlikely grease can resist the pounding

 

[gsaddict]

Can I have a close up of Minotaur's hoof if you have it handy

OK' you got me....I have an octopus in Formaldahyde.....will that do?

 

[cele0001]

Quick update. I took the starter out and took a peak at the clutch plate. All OK rivets are still tight. I ride the bike and forth to work so about 350 miles this week and past weekend with the rivets installed. I am running mostly highway 75-85 mph and it running 150-155 miles per 4 gallons (when the light comes on). Getting really into this BMW thing. Love the side cases and I am becoming big ATGATT guy

Here is a quick shot

 

[gsaddict]

. Getting really into this BMW thing.

View attachment 44076

Have you noticed the second word of my forum name?

 

[roger 04 rt]

here u go

thanks! The key thing is that the engine torque transient is damped well after the spline coupling. Once the spine is loose those every cycle engine transients tap away at the spline hub interface.

and i think this is the key. Once the process starts it is highly unlikely grease can resist the pounding

At 4500 RPM there are 75 torque pulses per second. Each pulse lasts about a third of the rotation so if the engine is putting out an average torque under acceleration of 50 lb-ft, the torque pulses during the combustion cycle average 150 lb-ft. The peak within that third of the rotation is likely twice that average. So we're talking about 75 pulses of 300 lb-ft per second of acceleration.

Once there's some wear in the hub/spline it sounds like there's potential for hammering of the spline faces.

A longer spline engagement may not be needed from the standpoint of simple sheer strength. But a longer spline engagement should resist displacement of the clutch hub from the perpendicular plane it is supposed to run in.

I've worked up a model for the relative motion of the spline teeth once there is misalignment and wear. I'll try to finish and post it tomorrow. The wear from that pattern of motion may be reduced by lubrication.

For my own clutch I'm thinking:
1) Don't let the wear progress too far
2) Keep a film of grease on the hub/shaft
3) Get a longer clutch hub and full engagement
4) Minimize misalignment--flywheel/clutch housing first, transmission housing second if needed
RB

 

[jammess]

Thanks! The key thing is that the engine torque transient is damped well after the spline coupling. Once the spine is loose those every cycle engine transients tap away at the spline hub interface.

Yup, so keep the revs up and stay away from 6th gear.

 

[GKman]

Just to add to the confusion, in assemblies that have steel rubbing on steel (without lubrication) no matter the hardness, one part must be harder than the other or galling will occur. Seems like 50 brinell hardness difference was either minimum or typical. That is how bulldozer tracks work, and work very well, without lubrication. I don't think this assembly meets the qualification as lubricated. A dab of grease in 50,000 miles hammered as detailed above is not going to be there at the microscopic point of maximum pressure.

I don't think the failure would be classified as caused by a lack of hardness. Looks like a lack of yield strength. The surface doesn't fracture and erode away. the tooth deforms plastically under the surface. It would take a detailed analysis and is likely a combination of both. I think with more area of engagement the problem would be solved without worrying about the metallurgy.

 

[gsaddict]

The hardness difference was explained to me as well. Thanks

 

[happy wanderer]

It would be interesting to get a failed shaft and matching clutch hub from Anton's pile. (He must have a pile) Then take it to the nearest university with a metallurgical engineering dept. and donate it for a failure analysis project. They have awfully nice tools and microscopes for looking at these things in great detail. Good teaching and learning project and maybe we'd get to enjoy the report.

 

[cele0001]

It would be interesting to get a failed shaft and matching clutch hub from Anton's pile. (He must have a pile) Then take it to the nearest university with a metallurgical engineering dept. and donate it for a failure analysis project. They have awfully nice tools and microscopes for looking at these things in great detail. Good teaching and learning project and maybe we'd get to enjoy the report.

Opening conversation would go something like this:

These are the parts?
Yes.
This is the clutch hub?
Yes
How come last 6 mm are not worn at all and the rest is stripped out completely?
Because the shaft doesn't go all the way through it.
Why not?
I dont know you tell me you are the expert.

 

[nrpetersen]

Opening conversation would go something like this:

These are the parts?
Yes.
This is the clutch hub?
Yes
How come last 6 mm are not worn at all and the rest is stripped out completely?
Because the shaft doesn't go all the way through it.
Why not?
I dont know you tell me you are the expert.

Better add a gear (spline) expert. There are red herrings in engineering, too.

 

[cele0001]

Better add a gear (spline) expert. There are red herrings in engineering, too.

It it my understanding that when GSAddict was making his custom shaft it was examined by gear spline experts and they also agreed that shaft should be longer to ensure full engagement on the clutch hub, so I don't know why this red herring thing keeps coming up.

 

[cele0001]

Once there's some wear in the hub/spline it sounds like there's potential for hammering of the spline faces.

A longer spline engagement may not be needed from the standpoint of simple sheer strength. But a longer spline engagement should resist displacement of the clutch hub from the perpendicular plane it is supposed to run in.
RB

And these two points are where my thinking is coming from also. I have no doubt that even half of the surface of the spline/hub engagement is enough to carry constant load, but running away from the perpendicular plane during "hits" is where wear starts.
This is where very small alignment tolerances that should normally be fine make a difference between "bad" bikes and "good" bikes. The +/- window becomes smaller than it should normally be, (by normally I mean with full spline/hub engagement.)

 

[roger 04 rt]

It it my understanding that when GSAddict was making his custom shaft it was examined by gear spline experts and they also agreed that shaft should be longer to ensure full engagement on the clutch hub, so I don't know why this red herring thing keeps coming up.

GSAddict's experts also mentioned shaft hardness.

 

[nrpetersen]

It it my understanding that when GSAddict was making his custom shaft it was examined by gear spline experts and they also agreed that shaft should be longer to ensure full engagement on the clutch hub, so I don't know why this red herring thing keeps coming up.

Because many (most?) bikes have no wear problem. And many that do seem to have repeat failures. And even BMW in their infinite wisdom breaks the warranty failure chain by replacing the transmission and housing.

 

[cele0001]

Blast from the past

In actuality they are quite different from a metallurgy and tolerance perspective. Not to mention being 6mm longer.

This is from the beginning of the thread.
He is talking about his shaft.
GSAddict did you keep the same transmission and engine when you installed your longer shaft into the box (gearbox that is)?
I know, I crack myself up but I would appreciate the confirmation that the engine and gearbox are original.

 

[gsaddict]

This is from the beginning of the thread.
He is talking about his shaft.
GSAddict did you keep the same transmission and engine when you installed your longer shaft into the box (gearbox that is)?
I know, I crack myself up but I would appreciate the confirmation that the engine and gearbox are original.

All I changed was the input shaft,clutch plate, 6 bolts and the input shaft seal on both ends.

 

[cele0001]

So if your shaft was misaligned it still is. Correct ? btw how long did it take the first shaft to get destroyed?