2000 R1100S Driveline Issue

[smddanny]

I also understand that the orientation as show in your BMW motorcycletech.info is correct.. but it is completely un-intuitive to me that this should be done as shown.. sending me back to the books to look at how U joints, which are not constant angular valocity joints work.

BTW..changed out the clutch in my 09 K1200S for a Barnett racing clutch lamellar pack last night.. easy peasy.. but yet another BMW seriously flawed design not owned up to...

[Dana in Philly]

Kinda non-intuitive to me too, smddanny; it seemed to me that for balance, you'd want the outside yokes turned 90 degrees to one another -- but what do I know?

So I guess what I'd wanna do is mark the back end of the shaft to show the orientation of that front outside yoke (which won't be visible once the swingarm's on), so that I can properly orient the back end of the shaft vis a vis the rear outside yoke....

[Lowndes]

Dana,

It's not about balancing the spinning weight, it's more about what smddanny alluded to: "...U joints, which are not constant angular velocity joints...". as in constant rotational speed. The more deflection angle in the joint, the more change in speed. You've heard of "CV joints", well, these ain't them. And you would be correct about having them aligned the other way, except that this way they tend to cancel each other out.

It's always sumthin.

[nrpetersen]

A deflected Cardan joint (U-joint) adds a 2 per revolution extra motion proportional to the square of the angular deflection. Two of them can cancel each other out but only if they are deflected to identical angles.

But the geometry of the rear suspension of BMWs is such that the Cardan joint angles are not anywhere near identical. That may be the reason the manufacturer doesn't give any recommendations on joint orientation.

I recall the rear angle goes thru a much greater excursion than the front. Hence it dominates.

[smddanny]

Great guys! Lownes and nrpetersen... I thought the change in angular velocity would cancel if the two joints were 90 degrees out of phase... I recall seeing all my old vehicles built this way..

So why align????? I don't get it yet.. but I haven't ruminated on it long enough...

[sgoodwin]

'Cause if you don't it WILL vibrate badly. Go back & read some of the posts on this issue. Many have put these back together without phasing them, all to their dismay and subsequently having to do it right.

[Lowndes]

Originally Posted by smddanny

Great guys! Lownes and nrpetersen... I thought the change in angular velocity would cancel if the two joints were 90 degrees out of phase... I recall seeing all my old vehicles built this way..

So why align????? I don't get it yet.. but I haven't ruminated on it long enough...

Excellent question. Short answer (I think this is correct, nrpetersen??) is that they ARE 90 deg out because one is "facing" forward, the other aft, if that makes sense. What the diagram calls "in phase" is actually out of phase. Better terminology might be "correctly phased".

[nrpetersen]

These are actually Hooke's type joints according to Mark's Engineering Handbook (9th Edition). It states "A constant velocity ratio of 1 between two main shafts may be obtained at any angle using two Hooke's joints and an intermediate shaft which must make equal angles with the main shafts. The driving pins on the yokes attached to the intermediate shaft must be set parallel to each other."

I had to look it up. Been retired for 17 years from this sort of stuff.

Now I gotta check what I wrote earlier.......

[Lowndes]

Suggestion for those who are taking the drive shaft apart or are removing part or all of it:

"Phase" the shafts on the workbench, then mark the mating splined ends with a center punch or file notch so that the marks can both be seen from the FD end of the swingarm. The female end is recessed way up in there, so you can only see the end face. Mark the top of a spline tooth to line up with it. Paint is easier to see but will wipe right off with all the oil and grease. AMHIK.

[BikerMiker]

https://www.youtube.com/watch?v=gmV4qwLfOMY

[Dana in Philly]

That's wild. Thanks for that link. I should chat with the local schools about academic credit for this thread.

[Dana in Philly]

So first we dry-fit the drive shaft and rear drive, lining up the outside yokes in the same horizontal plane:



Next we marked the proper orientation on both pieces with black Sharpie, and tested that it didn't rub off.





And then....

[JimMoore]

Hey Dana,

I'm intrigued by the rubber debris on the front half of the driveshaft. That looks kinda like a driveshaft about to separate at the rubber joint. Not unheard of.

[Dana in Philly]

Just like in the service manual, with a few taps from a plastic mallet, the drive shaft popped on to the greased output splines of the trans.



There followed a good hour of screwing around with the rubber boot on the front end of the swing arm, as I tried to verify that the snap ring was in there, popped it out by mistake, then tried to get it back in after having greased the boot's front and back edges as prescribed by the service manual.

Like mud wrestling.

Eventually....



You can see the Sharpie mark at 12:00 on the back end of the drive shaft, snugged inside the swing arm.

Next steps: shock, and final drive.

[Dana in Philly]

Sorry about the sideways images. Seems like the forum software doesn't like portrait orientation, and turns the images 90 degrees counterclockwise to get landscape.

[Dana in Philly]

Dude, you tellin' me I need a new drive shaft, after 27,000 miles?

I think maybe "debris" is kinda strong. Maybe "manufacturing artifact" would be better.

And why is there a rubber joint in a drive shaft? Some kind of damping system?

Originally Posted by JimMoore

Hey Dana,

I'm intrigued by the rubber debris on the front half of the driveshaft. That looks kinda like a driveshaft about to separate at the rubber joint. Not unheard of.

[Dana in Philly]

The swing arm front end pivot bearing stud torques are so freakin' low, yet the locknut torque is so wildly high:



What's up with that? Maximum freedom of movement? No pinchies? Anybody have an engineering explanation?

[N41EF]

Guessing here, but the stud bolts keep it from moving around, and the locknuts keep the stud bolts from backing out. If you over torque the stud bolts you could damage the housing. The lighter torque keeps the slack out, but keeps them from coming loose.

[JimMoore]

Originally Posted by Dana in Philly

Dude, you tellin' me I need a new drive shaft, after 27,000 miles?

I think maybe "debris" is kinda strong. Maybe "manufacturing artifact" would be better.

And why is there a rubber joint in a drive shaft? Some kind of damping system?

Yeah, it's a driveline shock damper, kinda like the rubber chunks (the name escapes me) in the hub of a chain-drive bike. I had one spin on my R1100RS a few months ago, so I'm a little sensitive to it. I have a spare R1100S driveshaft in the garage. Let me know if you're interested.

ETA: Cush drive

[JimMoore]

Originally Posted by Dana in Philly

The swing arm front end pivot bearing stud torques are so freakin' low, yet the locknut torque is so wildly high:



What's up with that? Maximum freedom of movement? No pinchies? Anybody have an engineering explanation?

The 7 nm preloads the bearings. The big locknut number holds everything still after the bearings are preloaded.