Checking for spline wear 1999 R1100S

[blacque jacque shellacque]

Okay, I'm following you. But if the hub spline is 22 mm and the input shaft spline is 22 mm and the input shaft has 6 mm not worn, why can't you access all of the 22 mm on the shaft and get the 6 mm?

I reread the original post, and I think I now understand where my confusion lies. I ran to the basement to measure the spline length of the shaft.

shaft splines 24mm
hub splines 22mm
hub spline engagement is 18mm with 4mm of hub hanging off the end of the shaft.
A 6mm spacer would position the hub completely on the shaft splines. The hub would now be positioned so that 2mm of the shaft would now protrude out of the hub. So the answer is yes, you should be able to use the 6mm of shaft spline.

The hub would now be very close to the shaft seal, and I wasn't able to see or measure that gap. It would not be a good thing for the hub to contact the seal. These are approximations, not perfect measurements. Smarter people than I have already done accurate measurements and know what works.

 

[nrpetersen]

Since you believe this, how much do you think the engagement could be reduced before it would be a problem? The engagement seems to be about 16 mm, would 8 mm work just as well?

Assuming the spline only has to carry 60 ft lbs torque, 20,000 psi shear stress material, with 18 spline teeth on an average working diameter of 0.9 inches, and no safety factor, if I did my sums right the spline length would only have to be about 2 mm (which seems so small it is hard even for me to believe).

BUT assuming some radial misalignment - the spline teeth are also loaded in fully reversed fatigue - and it's once per engaged engine revolution, and of a much higher force to each tooth than that caused by the torque.

AND - any radial load is concentrated at one end of the spline engagement because of the flex plate.

That's why adding length to the spline engagement at the engine end won't do anything constructive - because all the radial load is concentrated at the transmission end.

8 mm would work almost as well - look at the shaft spline pix above at post 94 where you can see from the wear pattern that only about 8 mm is carrying any tooth load. And that's virtually ALL from radial misalignment.

 

[roger 04 rt]

Thanks for those measurements, I now understand. I'm trying to work out what to do in my case: 30K miles, about 1.5 mm play which is about a degree. I don't think there's reddish rust but there is some blackish dust in the housing. I'm planning to clean and lube the splines and hoping that's it.

Questions on my mind are: should I consider a new clutch plate with extended hub, assuming shaft wear is minimal? If a new clutch plate, should replace I replace the housing, pressure plate and cover. Having had the fuel system fail on the highway, I'd rather not have the clutch splines fail--ever. Parts cost for entire clutch $907 with stock clutch disc, $1,238 with Bruno's clutch disc. Then, assuming I could install it, $305 for a new shaft. Total parts $1,212 to $1,543.

The economic approach would be to check wear every 10K miles and then do full clutch and input shaft. But the more I let it wear the more parts I'll buy.

--Angular misalignments of shaft centerlines seem remote, in general.
--Axis misalignments seem unlikely on mine considering I don't seem to have a lot of wear at 30K. But if I were to replace the shaft, should I check that too.

Maybe I'll lubricate and replace the clutch disc if the splines aren't worn and see if that tightens things up.

 

[nrpetersen]

Thanks for those measurements, I now understand. I'm trying to work out what to do in my case: 30K miles, about 1.5 mm play which is about a degree. I don't think there's reddish rust but there is some blackish dust in the housing. I'm planning to clean and lube the splines and hoping that's it.

--Angular misalignment of shaft centerlines seem remote, in general. (yes)
--Axis misalignments seem unlikely on mine considering I don't seem to have a lot of wear at 30K. But if I were to replace the shaft, should I check that too.

Maybe I'll lubricate and replace the clutch disc if the splines aren't worn and see if that tightens things up.

If you only have 1.5 mm tangential backlash at the clutch disk OD, your splines are worn very little. You might be able to get by with a hypodermic lube job as done by some others. If you plan to take it apart, just go with a standard clutch disk/hub, but be sure to arrange the clutch to be pulled in while the engine-transmission bolts are being tightened to get the "happiest" alignment.

Personally I'd try a hypodermic lube (but get it to all surfaces) after blowing as much crud out of the spline as possible. Maybe brake cleaner could be used to enhance the purging process. Assuming yours is presently only the factory lube, it is like they just barely painted anything on. Mine looked like it only had been varnished. If you have only black wear products (and no red), might that just be clutch debris?

Get pictures for comparisons!

Just checked Motobins. If you do tear it apart, replace the clutch disk w stock BMW. It's like only $120.

 

[jammess]

Hi Roger,
When are you going to do the spline lube? Who knows, maybe things won't be as bad as you think. I did mine at about 39K miles and could not detect any wear at all even under a magnifying glass. Was easy to do as I separated the trans from the engine without disassembly of the drive train. Just positioned an hydraulic jack on wheels under the tranny and rolled everything back. Then if you get lucky put it back together and forget you have that 6th gear! I know that is hard to do especially with that LC-1 installed. Oh, one more thing..buy a clutch slave cylinder for about fifty bucks in advance because you will probably need it..grrrr

 

[nrpetersen]

......... put it back together and forget you have that 6th gear! .........

Note from above the spline stress contribution from torque (or torque impulses) seems very low in the life of things.

 

[blacque jacque shellacque]

Thanks for those measurements, I now understand. I'm trying to work out what to do in my case: 30K miles, about 1.5 mm play which is about a degree. I don't think there's reddish rust but there is some blackish dust in the housing. I'm planning to clean and lube the splines and hoping that's it.

Questions on my mind are: should I consider a new clutch plate with extended hub, assuming shaft wear is minimal? If a new clutch plate, should replace I replace the housing, pressure plate and cover. Having had the fuel system fail on the highway, I'd rather not have the clutch splines fail--ever. Parts cost for entire clutch $907 with stock clutch disc, $1,238 with Bruno's clutch disc. Then, assuming I could install it, $305 for a new shaft. Total parts $1,212 to $1,543.

The economic approach would be to check wear every 10K miles and then do full clutch and input shaft. But the more I let it wear the more parts I'll buy.

--Angular misalignments of shaft centerlines seem remote, in general.
--Axis misalignments seem unlikely on mine considering I don't seem to have a lot of wear at 30K. But if I were to replace the shaft, should I check that too.

Maybe I'll lubricate and replace the clutch disc if the splines aren't worn and see if that tightens things up.

I don't think you have anything to worry about. With 72k miles, I measured 6mm of play. Your measuring a mere 1.5 in 30k. It seems to me you got one of the good bikes! The black dust is from the clutch, that's normal. As suggested you may want to inspect and lube, but it appears you have quite a ways to go before you have to worry about having to replace parts.

 

[roger 04 rt]

Assuming the spline only has to carry 60 ft lbs torque, 20,000 psi shear stress material, with 18 spline teeth on an average working diameter of 0.9 inches, and no safety factor, if I did my sums right the spline length would only have to be about 2 mm (which seems so small it is hard even for me to believe).

BUT assuming some radial misalignment - the spline teeth are also loaded in fully reversed fatigue - and it's once per engaged engine revolution, and of a much higher force to each tooth than that caused by the torque.

AND - any radial load is concentrated at one end of the spline engagement because of the flex plate.

That's why adding length to the spline engagement at the engine end won't do anything constructive - because all the radial load is concentrated at the transmission end.

8 mm would work almost as well - look at the shaft spline pix above at post 94 where you can see from the wear pattern that only about 8 mm is carrying any tooth load. And that's virtually ALL from radial misalignment.

Good discussion. I looked carefully at that pix in post 94, and although it has worn a lot at the end, it has also worn the length of the spline. The spline width is more at the inboard end than the outboard.

I'm thinking that with some clutch pack-induced radial load, the longer engagement serves to keep things tighter longer. Like when you use the straight end versus the ball end of an Allen wrench.

 

[gsaddict]

I just measured the photo posted earlier (below) and come up with about 6 mm. Interesting that yours is less.

What is needed is 4.5mm. (actual measured clutch hub spline)
I made my proto 6mm longer so there was a safety/tolerance margin.
There is tons of room in there so one could even go longer is they wanted to - not that one would.

 

[jammess]

Note from above the spline stress contribution from torque (or torque impulses) seems very low in the life of things.

Maybe true but going back to Anton's observation pertaining to spline failure rate on bikes with the 6 speed trans. I'm just saying..and what with a large displacement flat twin engine and the associated rocking couple which maybe is an issue at low RPM under load. Also, and I think this has been discussed in the past, there is no support for the trans input shaft spline end. Another difference between the airhead and oil head motors is the massive flywheel used with airhead engines which probably dampens rocking couple? I'm not a mechanical engineer for sure but when a guy with much practical experience like Anton makes an observation I pay attention.

 

[blacque jacque shellacque]

Maybe true but going back to Anton's observation pertaining to spline failure rate on bikes with the 6 speed trans. I'm just saying..and what with a large displacement flat twin engine and the associated rocking couple which maybe is an issue at low RPM under load. Also, and I think this has been discussed in the past, there is no support for the trans input shaft spline end. Another difference between the airhead and oil head motors is the massive flywheel used with airhead engines which probably dampens rocking couple? I'm not a mechanical engineer for sure but when a guy with much practical experience like Anton makes an observation I pay attention.

I believe Anton stated that he has replaced entire clutch assemblies on bike's with badly worn splines. He also stated those same bike's have not been coming back for rework. Other then a few cases where the misalignment was documented, Antons comments suggests to me that BMW shipped some bikes with cockeyed clutch parts. (cockeyed being a highly technical term) I know its hard to believe and accept that BMW would ever do such a thing. As the premium brand of all motorcycles I am sure all parts are inspected and verified to specifications prior to installation.

 

[nrpetersen]

Maybe true but going back to Anton's observation pertaining to spline failure rate on bikes with the 6 speed trans. I'm just saying..and what with a large displacement flat twin engine and the associated rocking couple which maybe is an issue at low RPM under load. Also, and I think this has been discussed in the past, there is no support for the trans input shaft spline end. Another difference between the airhead and oil head motors is the massive flywheel used with airhead engines which probably dampens rocking couple? I'm not a mechanical engineer for sure but when a guy with much practical experience like Anton makes an observation I pay attention.

My failure experience is with my lil' ol' airhead R90/6 at ~25,000 miles. My R1100RT showed no distress at ~25000 miles. I drive both of them using all gears & comparatively low RPM. After all I am 75 so I get to drive like it......

 

[jkmolt]

splines

I'm not a mechanic so truly don't know much. I do know, though, that before BMW dropped the required 40,000 mile spline service people had very little if any problem with the splines. Though it's a spendy proposition, I still have mine serviced (re-greased) every 40,000 miles. Have seen them while apart and have seen very little wear. This was so on all four Beemers I've owned, a K75, K100, K1200LT, and now an R1100RT w/sidecar.

Just my thoughts.

 

[AntonLargiader]

...Antons comments suggests to me that BMW shipped some bikes with cockeyed clutch parts.

I don't have reason to think the parts are worse than on any other model; I think the design (with the incomplete shaft engagement) is less tolerant of imperfect balance and alignment. I've repaired worn splines on every model out there, but most them don't wear with the spiral pattern on the shaft. Instead, they wear more evenly along the spline.

If you try hard enough to visualize the wear, you will probably conclude that it happens because the hub rocks excessively on the end of the spline due to lack of full support plus some eccentric loading. The diagrams I used in the June 2007 OTL article demonstrate it pretty clearly.

 

[roger 04 rt]

Just read the 2007 OTL Splines II summary. Pretty good! Joined. Will back order the full article. The summary piece makes a lot of common sense. RB

 

[AntonLargiader]

If those back issues are not available I will eventually put the articles on my website. They are in bits and pieces on my hard drives at the moment.

Crude graphics, i know!

 

[roger 04 rt]

If those back issues are not available I will eventually put the articles on my website. They are in bits and pieces on my hard drives at the moment.

Crude graphics, i know!

The graphics look quite good to me, even in the 25% article that's on the RA site.

The discussion in this thread too has been very very helpful in forming a view to the underlying issues. Many thanks to everyone for their contributions so far.

 

[Jeff488]

The discussion in this thread too has been very very helpful in forming a view to the underlying issues. Many thanks to everyone for their contributions so far.

I'll add my thanks, as well.
It turns out, once again, that I'm not as smart as I thought.

 

[Omega Man]

Great thread guys
While I don't have nor have I ever worked on one of the assemblies in question, I've see this before. I have a 12.5 ton hydraulic boom truck and to run the hydraulics there is a direct drive PTO (power take off) into a 3 section pump. It is recommended to be lubed (never seize) periodically. The splined shaft goes into the same sort of arrangement and with out lube, the failure looks the same.
From operating this unit and seeing the failure, my theory is that the wear is from the inevitable "chucking" from power/strain being applied and then released and not so much the alignment (although it has to start off on the right track/alignment).
OM

 

[happy wanderer]

The diagrams I used in the June 2007 OTL article demonstrate it pretty clearly.

Wish I could find the article. The spline photo you posted earlier is there at the bottom of the listings but I don't see anything from a January 2007 issue. May not be looking in the right place or secret handshake required for the RA site.

Thanks for your insights on this issue. At the end of the day the guy with his hands on the problem gets my attention every time. Theory is all well and good but nothing like digging in to learn what's going on.