Driveshaft disappointment

[bobgerman]

I have decided to replace the driveshaft on my 2016 GS. The female splines on the rear yoke have had to be heated and broke loose with a lot of orange debris (rust) removed. Rust is metal and the splines show no wear. So away with the old. In anticipation of this I ordered a driveshaft from Ted Porter's Beemer Shop. It's very nice. When I removed the old driveshaft, I noticed the yokes were out of time, not lined up. I called a local BMW shop and they said if I brought the motorcycle in and they removed the shaft, they would approach BMW about warranty for this shaft. If BMW did not agree I would be responsible for all the labor. Seems chancy at best. I think I will just take my medicine and do it all myself and be done with it. I just thought I would share my discovery.

 

[mikegalbicka]

Is the yoke misalignment a problem?

Never mind. Saw the duplicate post with more info on it.

 

[88bmwjeff]

I've read on some forums that the yokes out of alignment is a problem; however, BWM designed them to be not in alignment.

A Google search indicated the following:
Phasing is the correct alignment between yokes at each end of the shaft. If the yokes are not in phase, speed fluctuations will not be cancelled out. These fluctuations cause vibration, which may damage components on the engine and the Jet pump. On most applications the yokes are commonly in phase when the yoke ears are parallel to each other.

So, BMW phased them as indicated in the picture for a reason--whatever that reason is, I have no clue.

 

[PGlaves]

I've read on some forums that the yokes out of alignment is a problem; however, BWM designed them to be not in alignment.

A Google search indicated the following:
Phasing is the correct alignment between yokes at each end of the shaft. If the yokes are not in phase, speed fluctuations will not be cancelled out. These fluctuations cause vibration, which may damage components on the engine and the Jet pump. On most applications the yokes are commonly in phase when the yoke ears are parallel to each other.

So, BMW phased them as indicated in the picture for a reason--whatever that reason is, I have no clue.

I don't think so. I think a low-bid supplier got sloppy and BMW QC didn't catch it. I have a table somewhere on this computer that if memory serves me correctly would indicate about a 9% speed variation between the input yoke and output yoke at 10 degrees of angular deflection on the U joints if they are 90 degrees out of phase. Speed change would be 20% at 15 degrees of angular deflection. The effect would be about half that at 45 degrees out of phase. This stresses the U joints and splines.

Properly phased the speed increase through the front U joint would be matched by the speed decrease through the rear U joint, causing the front yoke (splines) and the rear yoke (splines) to maintain the same speed.

There is absolutely no benefit from mis-phasing the two joints.

 

[Omega Man]

After reading this thread and the other thread, it seems like the best discovery is the driveshaft being difficult to remove. I think that moly lube Guard Dog or the Honda 60? lube to keep the spline lubricated will fix that after a little cleaning.
As it sounds like you didn’t notice any problem with the bike until you took it apart, you may have more miles left in the original driveshaft?
The Tag Cloud has a few threads in spline lube.
OM

 

[88bmwjeff]

I don't think so. I think a low-bid supplier got sloppy and BMW QC didn't catch it. I have a table somewhere on this computer that if memory serves me correctly would indicate about a 9% speed variation between the input yoke and output yoke at 10 degrees of angular deflection on the U joints if they are 90 degrees out of phase. Speed change would be 20% at 15 degrees of angular deflection. The effect would be about half that at 45 degrees out of phase. This stresses the U joints and splines.

Properly phased the speed increase through the front U joint would be matched by the speed decrease through the rear U joint, causing the front yoke (splines) and the rear yoke (splines) to maintain the same speed.

There is absolutely no benefit from mis-phasing the two joints.

The odd thing is that the parts diagrams from BMW show the phasing. This would suggest that it's a planned phasing. I'm not saying it's good or bad--that's above my knowledge and expertise. It just appears to be designed with that phasing.

Edit: Thanks Paul for that explanation.

 

[Visian]

Anton Largiader has a good reference page for this issue… but it does not cover the latest models, which are probably the same, but ymmv.

 

[bobgerman]

The odd thing is that the parts diagrams from BMW show the phasing. This would suggest that it's a planned phasing. I'm not saying it's good or bad--that's above my knowledge and expertise. It just appears to be designed with that phasing.

Edit: Thanks Paul for that explanation.

That's how mine is setup. Good eye

 

[stooie]

The phasing shown in the parts diagram is correct. A single Hooke's joint is not a constant velocity device; when at an angle the driven shaft speed will oscillate compared to the driving shaft. Using two joints (one at the front and rear of an intermediate shaft) phased 90 degrees apart will resolve this issue. Driveshafts of rear wheel drive cars are configured like this.

https://en.wikipedia.org/wiki/Universal_joint

 

[bobs_one]

Demo Video

The first couple of minutes of this YouTube video might be of interest.

https://www.youtube.com/watch?v=cXuMgPi0K68

With respect to why BMW would intentionally phase the joints I suspect it's to deal with Torsional Vibration - which results from the necessarily intermittent firing of the cylinders. The crankshaft actually decelerates and accelerates as the cylinders go through compression and firing and that acceleration and deceleration is called Torsional Vibration. Some modern cars now have timing gears which are not round to deal with this. The diameter of the timing gear becomes smaller as the firing stroke happens and is bigger on the compression stroke to compensate for Torsional Vibration. In conventional cars, it was the reason for the heavy Vibration damper on the front of the crankshaft.

If you actually want to understand this a bit better, you can check out
https://pdfpiw.uspto.gov/.piw?PageNum=0&docid=08303444&IDKey=8AF3895A3E99&HomeUrl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect1%3DPTO2%2526Sect2%3DHITOFF%2526u%3D%25252Fnetahtml%25252FPTO%25252Fsearch-adv.htm%2526r%3D15%2526f%3DG%2526l%3D50%2526d%3DPTXT%2526p%3D1%2526S1%3D%28litens.ASNM.%252BAND%252B%28%28%252522non-circular%252522.BSUM.%252Bor%252B%252522non-circular%252522.DETD.%252Bor%252B%252522non-circular%252522.DRWD.%29%29%29%2526OS%3Dan%2Flitens%252Band%252Bspec%2F%252522non-circular%252522%2526RS%3D%28AN%2Flitens%252BAND%252BSPEC%2F%252522non-circular%252522%29

I haven't really tried to work it out yet, but I suspect that by phasing the driveshaft U joints, you might be able to achieve the same sort of reduction as the non-round pulleys. If so, it's actually a clever thing BMW has done.

 

[DSXMachina]

I haven't really tried to work it out yet, but I suspect that by phasing the driveshaft U joints, you might be able to achieve the same sort of reduction as the non-round pulleys. If so, it's actually a clever thing BMW has done.

I disagree. What they did was essentially cover up for cheaping out and not using a constant velocity joint equipped shaft such as every front wheel drive car in the world uses. CV joints elegantly cover for major misalignment, are strong, and can last the life of the vehicle. If Motorad used CV joints there would be no need for 12K mile major services.

 

[Omega Man]

As an aside, I remember the first C/V joints I encountered. Early 70’s Ford Bronco’s had them and they were new and troublesome. It got to where they were being stolen from parked vehicles.
About the same era Dodge Ramchargers 4X4 front shafts has them and to lube them, the shaft had to be removed and a special pointed grease adapter was needed.

OM

 

[bobs_one]

I disagree. What they did was essentially cover up for cheaping out and not using a constant velocity joint equipped shaft such as every front wheel drive car in the world uses.

Well, U joints are cheaper, but they are also smaller (from the same torque handling ability) and lighter. I do note that the other motorcycle companies also seem to use them. For example, GoldWings use U joints.

 

[RadioFlyer]

The more I see shaft and final drive issues the more I doubt the contention that shaft drives are less maintenance and more reliable than a modern chain.

Sent from my SM-T813 using Tapatalk

 

[Omega Man]

The more I see shaft and final drive issues the more I doubt the contention that shaft drives are less maintenance and more reliable than a modern chain.

Sent from my SM-T813 using Tapatalk

Chains and belt drives made the industrial revolution possible.
OM

 

[akbeemer]

Chains and belt drives made the industrial revolution possible.
OM

And building driveshafts keeps industry busy.

BMW seems to be having more trouble than other brands, particularly on the GS line of bikes. I had a Super Tenere and FJR. Driveshaft failures on the forums of those bikes just isn't a thing that comes up. The least BMW could do is make their driveshafts serviceable and easily rebuildable, such as the ones being offered by the Beemer Shop. I expect a Beemer Shop driveshaft to be delivered here today. I'm going to install it on my R1250 GSA. The bike only has 2,046 miles on it but it has a sidecar installed which will put more stress on it. I'll keep the one I take off as a spare for Annie's R1200GS.

 

[Omega Man]

And building driveshafts keeps industry busy.

BMW seems to be having more trouble than other brands, particularly on the GS line of bikes. I had a Super Tenere and FJR. Driveshaft failures on the forums of those bikes just isn't a thing that comes up. The least BMW could do is make their driveshafts serviceable and easily rebuildable, such as the ones being offered by the Beemer Shop. I expect a Beemer Shop driveshaft to be delivered here today. I'm going to install it on my R1250 GSA. The bike only has 2,046 miles on it but it has a sidecar installed which will put more stress on it. I'll keep the one I take off as a spare for Annie's R1200GS.

It may not put more stress on it. Supplying what could be considered the other side of the swing-arm could actually help level out the stress on the drive line?
OM

 

[PGlaves]

Here are two issues with BMW drive shafts. First, the deflection angles on the GS driveshafts often exceed what is optimal for a universal joint. It is those angles that cause front wheel drive cars to have CV joints. It might seem counterintuitive but when heavily loaded with some rear end sag the deflection angles are limited (shaft is straighter) so the big guy or gal with all the camping and cooking gear will typically have longer GS driveshaft life.

The second issue is that the deflection angles of the two universal joints may not stay equal throughout the range of the suspension travel. I don't know enough about the intricacies of all the different models but I do know that altering the length of the rear control arm alters the angle of the rear U joint but not the front U joint. If by design BMW intended or allowed the two joints to be at different deflection angles, that might explain designing the shafts with the U joints deliberately out of phase.

 

[Omega Man]

Here are two issues with BMW drive shafts. First, the deflection angles on the GS driveshafts often exceed what is optimal for a universal joint. It is those angles that cause front wheel drive cars to have CV joints. It might seem counterintuitive but when heavily loaded with some rear end sag the deflection angles are limited (shaft is straighter) so the big guy or gal with all the camping and cooking gear will typically have longer GS driveshaft life.

The second issue is that the deflection angles of the two universal joint may not stay equal throughout the range of the suspension travel. I don't know enough about the intricacies of all the different models bud I do know that altering the length of the rear control arm alters the angle of the rear U joint but not the front U joint. If by design BMW intended or allowed the two joints to be at different deflection angles, that might explain designing the shafts with the U joints deliberately out of phase.

Sorta what I was saying. I was trying to not upset the "shaft drive" folks. My degree in "backyard engineering" tells me that if the whole shaft drive was around 20% more robust, it would cut down on a lot of the trouble. Of course the weight increase would be the down-side.
The S1000 is chain drive- for a good reason.
I hope Kevin posts a clear picture of the new style shaft after it arrives.
OM

 

[akbeemer]

Here is the Beemer Shop offering: