escapefjrtist
Searching for Dry Roads
...
Last edited by a moderator:
Broken Penske Clevis.
- Thread starter Cav47
- Start date
Help Support Yamaha FJR Motorcycle Forum:
Cav47
Adventure Seeker
I hear what you are saying G, but I simply could not get the Clovis to spin out without unbolting the top. I fiddled with it for at least 15 min two separate times. And then just figured I had to unbolt the top. The shock spring was hitting the inside of the "hole" in the bike. I couldn't pivot the shock far enough to get it past the bottom attachment point. I am not doubting you, but I apparently couldn't find the sweet spot to get that done.
I am out in the garage now cleaning all the pivot points and greasing them up. Ready to install the new part.
Well I am mostly enjoying the 75* weather and some Jim Beam, but it's all good.
I am out in the garage now cleaning all the pivot points and greasing them up. Ready to install the new part.
Well I am mostly enjoying the 75* weather and some Jim Beam, but it's all good.
Donal
Well-known member
I think I would start with the new clevis and the original bolt (but on the bench) before installing it on the bike.
Assemble the parts and just snug down the nut.
Then check to see if the head of the bolt is tight against the side of the clevis.
If it is tight, it might be worth checking with a micrometer or caliper to see if there is any deflection between loose and tight.
Assemble the parts and just snug down the nut.
Then check to see if the head of the bolt is tight against the side of the clevis.
If it is tight, it might be worth checking with a micrometer or caliper to see if there is any deflection between loose and tight.
wheatonFJR
...
wheatonFJR
...
If that was the case, it would be a general error showing it's warts in a more widespread manner.
I'm guessing that Josh and Iggy just had too much pizza before trying motocross with the FJRs.
hppants
Well-known member
My coffee is especially strong this morning, so the neurons are firing. Bear with me, please....
Looking at Josh's picture of the broken part with the hardware, it would be hard to imagine how to assemble it wrong. I'd take my dial caliper and measure the width (depth) of the inner race (which is really a spacer, IMO). Then compare that to the inside measurement of the replacement part - those two measurements should be pretty close. It's not entirely accurate, but I'd also use my caliper to measure the depth of the bolt shoulder, and compare that to the thickness of the clevis end with the big hole in it. Again, those two should be pretty close. If the bolt shoulder is slightly shorter than the depth of the big hole, that wouldn't bother me one bit. I'd also measure the diameter of the bolt shoulder and compare it to the diameter of the big hole on the new clevis. Those two measurement should be DEAD NUTS even. The shoulder of the bolt is necessary to keep the bolt (and the spacer) right in the middle of the clevis holes.
In the event the spacer measures more than 0.050" shorter than the inside measurement of the clevis, perhaps the use of a thin washer might make up the gap.
I'm not an engineer. I've done some mechanics of materials testing (University engineering lab tech in a former life), but what I know is just enough to be dangerous. Having stated that, IMO, it would be hard to imagine how the shear force from the shock moving back and forth would cause the clevis to fail the way they are failing. Again IMO, my money would be on putting to much clamping force on the clevis from the bolt, with the moment generated on the weaker side too much for the material strength. If I am wrong (won't be the first time), the only way to increase the shear strength of the clevis is to either choose a stronger material, make it much thicker (in 2 dimensions), or some combination of both.
My fifty-thousands WAG above is because I wouldn't want the moment on that 90 degree angle to load the material anywhere near the proportional limit of the material, which I fear it is currently doing. By holding that 90 degree angle as straight as possible, the moment would be greatly reduced.
Now, having stated all of this, here is my dilemma. The failure on Josh's part (and the others I've seen on this and other threads) looks like what I've seen in other test after the metal fails from fatigue. Repeated and numerous (maybe a million) cyclic loadings past the proportional limit, but below the elastic limit. If that is true, then it failed from the cyclic loading of the shock compression and rebound. Again, the fix would be a stronger (and less brittle) material, along with thicker proportions.
I suppose there is the possibility of both phenomena. A large moment placed on the 90 degree angle from squeezing by the bolt, followed by a cyclic load on that moment, causing a fatigue failure.
Wheatie - am I even in the right zipcode?
Looking at Josh's picture of the broken part with the hardware, it would be hard to imagine how to assemble it wrong. I'd take my dial caliper and measure the width (depth) of the inner race (which is really a spacer, IMO). Then compare that to the inside measurement of the replacement part - those two measurements should be pretty close. It's not entirely accurate, but I'd also use my caliper to measure the depth of the bolt shoulder, and compare that to the thickness of the clevis end with the big hole in it. Again, those two should be pretty close. If the bolt shoulder is slightly shorter than the depth of the big hole, that wouldn't bother me one bit. I'd also measure the diameter of the bolt shoulder and compare it to the diameter of the big hole on the new clevis. Those two measurement should be DEAD NUTS even. The shoulder of the bolt is necessary to keep the bolt (and the spacer) right in the middle of the clevis holes.
In the event the spacer measures more than 0.050" shorter than the inside measurement of the clevis, perhaps the use of a thin washer might make up the gap.
I'm not an engineer. I've done some mechanics of materials testing (University engineering lab tech in a former life), but what I know is just enough to be dangerous. Having stated that, IMO, it would be hard to imagine how the shear force from the shock moving back and forth would cause the clevis to fail the way they are failing. Again IMO, my money would be on putting to much clamping force on the clevis from the bolt, with the moment generated on the weaker side too much for the material strength. If I am wrong (won't be the first time), the only way to increase the shear strength of the clevis is to either choose a stronger material, make it much thicker (in 2 dimensions), or some combination of both.
My fifty-thousands WAG above is because I wouldn't want the moment on that 90 degree angle to load the material anywhere near the proportional limit of the material, which I fear it is currently doing. By holding that 90 degree angle as straight as possible, the moment would be greatly reduced.
Now, having stated all of this, here is my dilemma. The failure on Josh's part (and the others I've seen on this and other threads) looks like what I've seen in other test after the metal fails from fatigue. Repeated and numerous (maybe a million) cyclic loadings past the proportional limit, but below the elastic limit. If that is true, then it failed from the cyclic loading of the shock compression and rebound. Again, the fix would be a stronger (and less brittle) material, along with thicker proportions.
I suppose there is the possibility of both phenomena. A large moment placed on the 90 degree angle from squeezing by the bolt, followed by a cyclic load on that moment, causing a fatigue failure.
Wheatie - am I even in the right zipcode?
Last edited by a moderator:
Viper Pilot
Well-known member
Never had any problems with my Ohlins shock.
wheatonFJR
...
This appears to be a combined Tension(from Bending) and shear failure. If the failures have only occurred with the wrong hardware being installed, that must be some sort of root cause. However, the forces being applied in use would seem to be much higher than any extra clamping force due to mis-installed hardware.
Like I have said before, I only know what that break looks like, not what the root cause might be...who knows?
I'm sure because of the repeated action of the shock, that this is in material fatigue territory for tension, however, that would be the case for all the shocks, and all of them would be designed for that.
Like I have said before, I only know what that break looks like, not what the root cause might be...who knows?
I'm sure because of the repeated action of the shock, that this is in material fatigue territory for tension, however, that would be the case for all the shocks, and all of them would be designed for that.
Last edited by a moderator:
08FJR4ME
-WYNPRO-
I believe this is what I was inferring to but in a much simpler explanation. As bounce said the material may be to hard and prone to cracking. A more forgiving material choice would help also. Hopefully this informatoin is being passed along the Penske.
Dave
RaYzerman19
Go Wings!
I think this is the most likely answer, although squeezing too much with the lower mount bolt may contribute somewhat. See pic of the clevis on my RaceTech, much better design. A quick look of the OEM Gen3 clevis shows it is perhaps slightly better than the Penske.
So, solution at least to the lower bolt.... the clevis opening is ~1.18 on the RaceTech and the pivot spacer is slightly shorter, not a slide fit but a wee bit of clearance (probably about .005" or so). If you measure the front pivot spacer, it is 1.2". I'd propose using one of those as it is longer, it will fit in the large clevis hole and prevent any squishing of the clevis. There should be enough threads on the bolt to engage the lock features of the nut. Either that or, just install the normal parts and only snug up the locking nut on the mounting bolt. It is not going to solve the lack of radius on the clevis ride height adjuster........
Last edited by a moderator:
IMHO, the small radius at the bottom of the threaded boss acted as a stress concentration leading to fatigue failure. I whipped up a simplistic CAD model that illustrates the higher stresses around the thread base:
majicmaker
Well-known member
Yep! What he said... ^^^^
TomInPA
Well-known member
And yet the OEM shock clevis is a simple steel part with a design that has never been known to fail. I agree with all the theories above as a possibility, but the root cause is the use of a highly machined alloy that ultimately is prone to fail in the presence of the shock loads and movement. Perhaps the heat of machining itself determines the difference between parts that fail long-term and those that don't. All of the failed shocks have well over 50K miles on them in this thread. That said, Gerauld's point of failure illustration seems closest to what I'm seeing. There is not much that would prevent Penske from building up that shoulder or not threading that bolt so close to the clevis. Compare to OEM:
Last edited by a moderator:
RossKean
Well-known member
I would suggest that there is not supposed to be ANY side force on the clevis when it is tightened! No clamping force at all. The spacer should be sized such that it prevents the sides of the clevis from being pulled in. The correct shoulder bolt, the right spacer and proper installation are needed.
0Face
Well-known member
CLOVIS =
At roughly 13,500 years old, age and brittleness of material will be prone to failure. However, really a leap forward in design for the time.
If you look close Harley still uses a similar design on their FLHTSDOUCHE King Road Hog.
RaYzerman19
Go Wings!
Although I haven't checked.... the shoulder on the bolt should be greater than the thickness of the Penske clevis..... again would prevent overclamping as any contributor to the stress problem.
TomInPA
Well-known member
I heard back from Eric Trinkley at Penske Motorcycle Dept, in reply to an email with the image attached.
Life is good, and it appears I may be spared shipping the broke part back. BTW the FSM calls for a 29 ft-lb torque on that bolt.
Last edited by a moderator:
Cav47
Adventure Seeker
Dave, They did say that they want the part back for analysis. And to keep it out of the marketplace.
Cav47
Adventure Seeker
Off Topic. We need a Pointer Dog to get you back on Point!
CLOVIS =
At roughly 13,500 years old, age and brittleness of material will be prone to failure. However, really a leap forward in design for the time.
If you look close Harley still uses a similar design on their FLHTSDOUCHE King Road Hog.
Similar threads
