I was looking through some bearing catalogs today and they got me thinking….
Profile hubs are supplied with a standard sized 99R12 sealed bearing. this is the same bearing used in bottom bracket cups for bmx bikes.
The only problem with these bearings is that they are designed to be held in place by cups that are press fit in a bottom bracket and the inner sheilds are held in place between the crank arms and with a spacer between the insides of the bearings.
in this application the bearing does not need to resist an axial (sideways) load.
unfortunately in a uni application, only the inner shields of the bearing are kept a standard distance apart. the outer races are generally clamped somehow to the uni frame.
because of the lack of axial support, the uni frame is able to flex side to side or in and out due to the axial tolerances of the bearing. (the profiles float about a sixteenth of an inch each way, this is terrible)
flex is bad. and insufficiant axial support can cause the bearing to wear more quickly and eventually fail.
fixing this problem would involve the use of a bearing offering radial support (rotation) as well as axial. these bearings can be purchased in many sizes through a large number of bearing suppliers. only problem is they are very expensive. around eighty bucks a set.
needle bearings are also available that provide both radial and axial support. these bearings have much lower profiles for any given inner diameter giving a uni builder, like me, the option of greatly reducing the size of the bearing holder.
smaller bearings+smaller bearing holders=lighter unicycles.
uni application appropriate bearing=less flex+longer bearing life.
Any interest in revolutionizing the world of uni bearing standards?
Update on pre production frames: CAD work is done. took me a while cause i’m using a newer program that i’m not too familiar with. The sheet metal is at the lazer cutter. That’s right…. Lazer.
The bearing holders have been machined, but I’ve changed my design a bit and need to remake them. Luckily this will cost me no more than an hour of my own time…. Much more reasonable than 150 bucks that some have to pay…
if anyone wants my old ones for a custom uni, let me know… 50-75 bucks or so, I’ll pay shipping. they’ll accommodate a standard profile bearing (see above).
I’m not using the needle bearing idea (yet) cause I want the frames to be able to accommodate standard parts. But I will certainly be toying with the idea soon.
The first three frames hsould be done within a few weeks. I’m working twelve hour days and the holidays are taking up some valuable uni making time.
Thanks for all the information you all have provided, it has helped me in my journey as I hope my meager innovations will someday help you.
I don’t like the way the bearings on the Profile hub slip on so loosely on the hub. Because of the loose fit they can rock or slip on the hub even when they are clamped in really tight with the bearing spacers. It’s just sloppy. When I’m riding I can sometimes feel the axle slipping or rocking in the bearings.
To fix that I used LocTite sleeve retainer. The sleeve retainer fills in the gap between the axle and the bearing and makes it all tight. A much better ride. I can no longer feel the axle rocking or slipping in the bearing. Much better.
I will still be able to pull the bearing off even with the sleeve retainer. The sleeve retainer isn’t that strong. However, I fear that one or two of the spacers might be “locked” on the hub now because some of the LocTite oozed out while the bearing was slid on. If so, that would be a problem because it would be almost impossible to remove the spacer without damaging it. I’ll see if the spacer is stuck when it is time to replace the bearings.
Now that the bearings are LocTited on the Profile axle I can overtighten the bearing holders to the point that the bearing bind and the wheel will not spin freely. Before when the bearings were loose on the hub I could overtighten the bearing holders till the bearings bind and yet the wheel would still spin freely because the axle was just slipping (grinding) inside of the bearing.
About the needle bearing idea. I tried the Kore platform pedals a year or two ago.
The Kore platform pedals use a needle bearing instead of a bushing. When new they spin very nicely. However, on the muni they only lasted about three months of Winter riding before the needle bearings were completely shot. The cage the needle bearings were in just disintegrated. I’m not sure what caused the failure. It may have been because of the funky side-loads that pedals get when on a muni. It may have been because dirt and grit got inside there. I don’t’ know why, but I do know that they didn’t last. Granted they were small needle bearings. Maybe larger needle bearings as would be used on a unicycle axle would hold up better than the tiny skinny things in the Kore pedals.
Is this “flex” or lateral motion caused by the displacement of the inner race with respect to the outer race or by the inner race sliding on the axle because the axle diameter is smaller than the inner race ID?
LASER. It’s an acronym. The “S” is for stimulated.
i have never felt any of the bearing slop on my Profiles that is spoken of here.i love the slip on bearing thing about Profile.John,i think you got a factory second axle or maybe the inner race of your bearings are a micron out…should have bought Campy…
I’ve only felt the bearing slop on my muni. I’ve never felt it on the trials uni. I pedal a lot harder on the muni. What I can feel is a bit of a knock or a slip when I pedal hard. It only happens occasionally but is still annoying. Since LocTiting the bearings on I have not felt the knock or slip so I’m confident that the cause was the axle slipping inside the bearing and that the LocTite fixed it.
I only LocTited the bearings on the muni. I left the trials uni as it was.