Swing Arm Pivot Bearings

[WJR]

Got around to taking down my swing arm for maintenance. As expected, pivot bearings were toast, well one side was OK but not great. It has always seemed like a stupid set up. So, just wondering, and, full disclosure, I used a really crappy set of calipers because my good ones are missing, has anyone ever run ball bearings in the swing arm pivot? The pin is 17mm, the outer recess is 35 mm diameter, and the inner recess is 25mm diameter. Looking up bearings, 6003 would pretty much fit the outside, and a 6803, or a few of them stacked up, would almost fit--their OD is 26mm, on the inside. Running sealed bearings would seem to solve a lot of problems there. I suppose there would need to be spacers between frame/innner race of outer bearing, between inner races of inner and outer bearing, and inner race of inner bearing and motor. Any thoughts?

[Canniboomer]

I can relate to that thinking. I picked up those same bearings like 12 years ago! But the spacers needed in 4 places would be custom sizes. And for the outer bearings, the thrust forces of the ATV could quickly destroy those, with all of that firmly planted sliding around -- the sideways pressures out there are enormous, and even more with a wider Moto axle. For experimenting with the motorcycle?, there is much less twisting since the short axle just follows the frame.

I certainly agree with the need for grease, and preventing air pockets that allow moisture invasion and condensation rusting. No matter how much you grease-rub the parts, it's not good enough. There will always be voids after the install.
A solution is to grease-zerk the swingarm on each side. Cannondale left us the perfect space between the inner seal and the cup needle bearing, to drill and tap... on the top side of the swingarm. I have a kit that adds to the Pivot Bearings Kit.
Note picture of Removed bearings from a machine.. after all parts were installed "dry" for a testing demo. The pressure of a grease gun makes such a huge difference -- the grease creeps literally everywhere from medium pump pressure, and the excess will get oozed into the boltway. You just pump each zerk until you detect the outer seal starting to bulge.

[WJR]

That makes sense. I'll give that a try and save my new collection of odd bearings for next time...

[Canniboomer]

QUOTE (WJR @ Feb 6 2018, 02:55 PM) <{POST_SNAPBACK}>

....ball bearings in the swing arm pivot? .... the inner recess is 25mm diameter.....Any thoughts?

well yes, that was a crappy set of calipers you used!...lol The inner recess is actually 26mm, ... so you already have the correctly sized bearings.
I stalled my own project on this years ago, in worry about the sideways thrust force. Our current internal cup bearings provide zero sideways support, so that entire load is taken up by the thrust assembly out there.
BUT,... in rethinking this, when stacking several more ball bearings against the outer ball bearing, that axial support should add up, and probably work. Single ball bearings have very limited axial load, and are not usually even rated for that -- but ganging them should work, and is worth a try.

I think my own bicycle bearings for this are ABEC 5, and normal clearance. But whatever you already have, let's try it?... I did figure out the other misc parts needed, and will donate those for R&D, and can send to you.

You can just give me a call or pm to set it up.

[WJR]

I was ruminating on that too. In my understanding of it, it seems the component of pure lateral force would be fairly limited, it's more of a torque, with the pivot bolt as the fulcrum and the swingarm as the lever. Force to the side of the swingarm would result in rotation about a line perpendicular to the midpoint of the pivot bolt, but at that angle, it would seem to fall mostly within the ball bearings operating angles. The thing I didn't think about was the load rating. I think the 2020 needle bearings are like 20kN, while the sum of 6 6803 and 1 6003 is probably closer to 15kN. Axial load for these smaller bearings, according to SKFs info, is about half the standard load. So, in all the sum of the load rating for axial is way less than the needle roller thrust bearing. However, those are only good for essentially pure lateral force. All of that could be totally wrong, but that's how I was thinking about it.

I think I can stuff 5 or 6 of the 6803s , plus the 6003, on each side--that's 35 to 40mm worth. I bought few bearing spacer shim packs from mcmaster carr with +- 17mm ID to finish out the stack--also got a new set of Mitutoyos Im still game to try it, I didn't go back to the stock set up yet because I need a new 10mm shaft spacer, one of my old ones is cracked..

So, it'd be:
Frame--shims--6003--6803 x 3 or 4--shim (for grease)--6803 x 1 or 2--shims--engine boss====reverse on the other side.
I'll probably end up hand fitting some washers as spacers between the frame the inner race of the 6003--2mm worth is a lot of shims, and the 5mm ring thing is too thick.

How far in from the inside of the swingarm boss does the zerk go? In case this fails and I go back to the stock set up, I want to be able to grease it. I'll space whichever bearing pair is closest to the hole.

[Canniboomer]

Cool,... I think the zerks location is best done in the Same location as for stock pivot bearings. That is 7mm to 8mm OC from the Inner surface of the swingarm each side,.. so right at 5/16" is good. AND,... as far rearward as you can, AND on the top surface of swingarm.
The end of the zerk will not protrude into the boreway, for no issue with interference. This way, it works for either bearing scenario.... roller bearings or stock.
I can send you exact-ID shims that install from the inside, and after the bearings are set. You would then follow with the seal, then the 10mm bushing. I'll send a pair of the 10mms you will need, and 2 outboard spacers -- also exact 17mm ID. So for the install of the "loaded" swingarm compared to stock?... it involves only some extra technique to float in those 2 outer spacers.

[WJR]

This is as far as I have gotten. The little bearings are a pain to get in there because they are so narrow. Also, its a little bit of a trial and error to get the 6803 and6003 inner races to be snug but not axially pressing on each other. Also, the zerk might not work because I have an 02 swing arm and the internal opening on one side is just barley at the edge of the 4th 6803 bearing--so all the grease may go into the swing arm. The swing arm pivot bolt fits nicely in the inner races though, seems to be less slop.

[Canniboomer]

Cool... yep a bummer about the early swingarm with the voids. I think using the required shims between the outer bearing and first inner may block the void.
I think I can can send out the few needed additional items early this coming week... and with a setting tool.