A backwards step?

[ribbert]

Inviting opinions on my next proposed repair / mod

I'm leaning heavily towards replacing my swing arm needle bearings with plain bearings. To my mind, needle rollers were not necessarily a step forward in this particular application, where the arm only rotates a few degrees and results in this sort of wear.




Needle rollers are designed to turn /spin and need to rotate to remain lubricated, in this instance they don't and yet they are subjected to constant movement and load.

I was active in the business when it was common to replace (upgrade?) king pin bushes with needle roller replacements, the feedback was always mixed. Certainly no one hailed it as a great leap forward.

Any constructive input welcome, except for "Yamaha engineers must have known what they were doing" 


Noel

[red]

Noel,

I am curious about what "plain bearings" might be used there.

I agree that the needle bearings do not rotate much.
My first thoughts would be to upgrade the lubricant to the best available lately,
and maybe adding a Zerk fitting, rather than making a bearing change.

[ribbert]

Noel,

I am curious about what "plain bearings" might be used there.

I agree that the needle bearings do not rotate much.
My first thoughts would be to upgrade the lubricant to the best available lately,
and maybe adding a Zerk fitting, rather than making a bearing change.

Modern bearing/bush materials is not something I have a working knowledge of but I know for example they make "plastic" bush kits to replace OEM needle rollers in fork lifts where you've got small movement, high load and constant use and they last about 20 times longer. More homework needed. Maybe someone here knows about this.

If you were to fit a Zerk, the problem remains that no matter how much grease is around the bearing, the rocking back and forth by only a few degrees is going to squeeze it out and because it's not turning, it's not re coated. This was my original plan until I gave it a bit more thought.

Noel

[Carson City Paul]

Noel,

I am curious about what "plain bearings" might be used there.

I agree that the needle bearings do not rotate much.
My first thoughts would be to upgrade the lubricant to the best available lately,
and maybe adding a Zerk fitting, rather than making a bearing change.

Modern bearing/bush materials is not something I have a working knowledge of but I know for example they make "plastic" bush kits to replace OEM needle rollers in fork lifts where you've got small movement, high load and constant use and they last about 20 times longer. More homework needed. Maybe someone here knows about this.

If you were to fit a Zerk, the problem remains that no matter how much grease is around the bearing, the rocking back and forth by only a few degrees is going to squeeze it out and because it's not turning, it's not re coated. This was my original plan until I gave it a bit more thought.

Noel

Regular ball bearings are designed to fully rotate as well.

I believe the problem you will have, as well as the designers did, was if you or they want to run Ball bearings, the outer tube would have to be much larger (room and weight) or the pin/shaft going thru would have to be much smaller.

Personally I don't see an advantage to changing something that has worked well for decades.

[Pat Conlon]

As Paul said, with the limited movement, I'm not sure you will be better off with balls.

I was thinking about load distribution. How the needle bearings distribute the load over a larger area than ball bearings....allowing the load transfer in a smaller package.

Define the role: Do you need a bushing, or do you need a bearing?
Bearings should roll, however (as you point out) this application does not roll, so I would classify the need as a bushing.

Just a point of history: On FJ's needle bearings for the swinger linkage came about in 1986. Prior to that in '84/85 FJ's had nyloc bushings which worked well (when new) but as soon as they dried out they suffered rapid abnormal wear.

An option to the bushing material is a product called Derlin. Noel...That's what I think you should try.

Had Yamaha got a license from DuPont and used Derlin in '84, I would bet that Yamaha would have not evolved to needle bearings.

Here's a quote the the article linked below: "As a bushing material, delrin boasts many important properties including high tensile strength, high impact strength, high elongation, high chemical resistance,  low moisture absorption, and more. In addition to low deflection, delrin's best feature when compared with polyurethane is self-lubrication. As delrin bushings do not bind, your suspension arms are free to move through their entire range of travel. A useful side benefit to zero-binding is that delrin bushings will last a very long time."

https://www.ridetech.com/why-you-need-delrin-the-gold-standard-of-suspension-bushings/

You could sleeve the entire length of the tube with a one piece Derlin bushing so as to use the entire pin length for load transfer, instead of a narrow band where the needle bearings resided.
If you distrust the self lubricating properties of Derlin, put some Zerks in....

Cheers. Pat

[red]

Noel,

Pat's suggestion for Delrin bushings sounds like a good alternative.  I have used Delrin on small projects, but nothing heavy-duty like swing arms/suspension stuff. 
Besides the mechanical properties, one good advantage of Delrin is that it can be machined easily to your exact specs.

I won't be replacing anything back there for a while, but Delrin bushings are certainly a consideration.  I had not seen that article on Delrin before.  Thanks, Pat.
.

[Dads_FJ]

Don't know if this helps but thought I'd throw in my .02.  My 1977 Yamaha IT175 uses bronze swingarm bushings while the same year YZ series bikes use needle bearings.  The thought on some IT forums is that since the IT bikes go through mud and rivers and muck the needle bearings would get destroyed because of all the crap that would attached itself to the grease.  This isn't the case so much with bronze/oil bushings apparently.  Of course there are other factors such as load, cost to produce or how long manufactures want something to last.

Hope this didn't 'muddy the water' so to speak...

[FJ_Hooligan]

The FZ1 uses plain roller bearings in the steering head.  I believe the steering head rotates through a larger angle than the swingarm.

I noticed a distinct notchiness in the handlebars one day.  Felt just like brinelling of the race, like the balls were going in and out of a divot.  

Assuming the worst, I ordered a tapered bearing replacement kit.  Once I got the steering head apart I didn't see any damage to the races or the balls.  The grease was pushed out of the way.  I simply cleaned the bearings and races, regreased and the notchiness went away.

The tie in is this appears to be a very similar application as the swingarm bearings.  The plain roller bearings in the steering head did not appear to be rotating any more than the steering angel.  IOW, they were just moving back and forth and not circulating (which is what it sounded like you were wanting).

[ribbert]

Thanks everyone for your input. Pat, I will follow up on the bushings you mentioned.

I seem to have confused things a bit, a "plain bearing" is a bush, not a roller bearing.

As has been mentioned, the easiest route would be to replace what's there and based on the performance of previous replacements, that would probably see me out. But that's not the point. I've never thought the needle rollers were a good choice for this application and it appeals to my mechanical side to experiment a bit and see if there's a better solution. Because I need bearings and pins, it's not a cheap job to replace them either.

Who knows, this research could make me famous, maybe one day my findings could be written into FJ forum lore.

Thanks again, if anything exciting comes to light I'll report back. If anyone has a further suggestion, get in touch.

Noel

[ZOA NOM]

Porsche spring plate polybronze bushings. Wonder if you can find something similar. These have worked very well in my race car application.

[FJ_Hooligan]

I seem to have confused things a bit, a "plain bearing" is a bush, not a roller bearing.

Oops.  Sorry about that, my bad.