3 Stack SemCycle adjustments

My daughters unicycling club at school is going to be in a parade. They have a Sem Cycle 3 stack they want to use, but sometimes the wheels slip. I’ve noticed that the top wheel does not seem straight. Also I’ve read on this forum is that main cap bearings should not be overtightend, but I want it to not fall apart. I just read the topic “Uneven wheel gap on Yuni frame” and got good ideas about shimming and checking wheel truing and dishing. If any one else has any other suggestions it would be appreciated.
Ron Rupert

Tire pressure is the other way to control grip on multi-wheelers. But tire alignment has to be right before you can stress things. I don’t have experience with that wheel setup, but the shim approach sounds like the logical one.

Your bearing holders would benefit from those nuts with the nylon stuff in them that keeps them from unscrewing. If you don’t have that, make sure there are at least lockwashers on there.

For safety, you want lots of grip between your tires. A properly adjusted multi-wheeler will have a fair amount of friction in the drivetrain. Don’t expect it to roll smooth, you want it to not slip!

I’v observered that Primo the wall tires are popular for multiwheeld cycles such as yours, they seems to prevent slipage as well.

Sorry to change the subject, but I’m intrigued. How was this club formed and how many members are there? We’ve got nothing like that at any of the schools here.


Bruce Edwards (a.k.a. Yoopers) posted that he recently got a Semcycle 3 stack. Contact him and find out how he has dealt with the adjustments and setup for the 3 stack. His contact info is on his home page:

Thanks for the responses. I’m going out there Tuesday to make the adjustments and repair some of the other uni’s. I’ll email Bruce Edwards if I run into problems.
Andrew, her club I believe was started about 10 years ago. Some unknown person had left a unicycle in the P.E. room and a new PE teacher found it and wanted to see if any of the kids wanted to try it. Several did and they just grew from there. There are several unicycling clubs at schools around here, Gold Bar WA.

Sorry, I haven’t been monitoring the boards recently. Life is pretty busy these days.

Yes, we did buy a three-wheeler recently and have used it in parades. It is a real attention-getter for the crowds. When we purchased our uni, John Drummond cautioned us that the bearing holder bolts would loosen occasionally and would have to be retightened. Eventually it would settle down and maintain it’s tightness. We found this to be true. I kept a 10mm nut driver handy for parades and had to tighten the bolts about twice per parade. The tightness of the bearing holder caps really shouldn’t be any looser or tighter than an ordinary unicycle in my opinion.

We found that tire pressures of around 20 lbs. works well. John D. also warned us that all three tires should have exactly the same pressure for best results.

Two things to watch for and appropriate fixes; the bearing holder bolts should be tightened so as to keep the sections of fork extensions parallel with each other. That also helps with the second problem, having a tire track off to one side. We were able to quickly figure out how direct or maybe better yet, steer the tires back into track with each other. Let me see if I can explain it simply.

If a tire is tracking off to the right, the front left bolt should be tightened. That would draw the track back to the left. A mental visualization of the “steering” always helps me. Of course, the ol’ vicey versa is on tap for steering a tire to the opposite side. Gotta watch that the extentions don’t get out of parallel though with any steering adjustments made.

We’re having another problem though with our three-wheeler that should be mentioned. The stress on the top joint is taking it’s toll on the bearing holders. The bearing cap bolts of the top joint have bent and ears of our bearing holders have started to bend as well. Now the deformed bearing holder is preventing us from maintaining any degree of proper tightness of the bearing connection.

I’ve attached a photo. The first part shows the bolts, the second shows the bending ear of the bearing holder cap, and the third shows the paint pulling apart as the ear bends down.

I’m going to have a machinist friend of mine look at the problem and try to come up with a fix to strengthen the connection. Any suggestions or experiences from you would be helpful.

yoopers at inwave.com

I know this is an old thread, but seemed better to revive it than start anew?

I have the SemCycleXL 3 stack, and am attempting to get it adjusted where the top wheel doesn’t track off to the side of the middle wheel…
I bought mine used and falling apart… Have replaced tires and bearings, but we don’t ever ride it more than a few feet because the wheel ends up tracking off to one side… Will attempt the suggestion here to tighten the opposite side.

Have the same problem with the bent bearing holders, I put some rubber washer/spacers in the gap between the extensions in an attempt to reduce the stress there…

I’m curious about the tire inflation recommendation here; that all 3 tires should be the same. I’ve read in many other places that the top and bottom should be the same, but the middle should be barely aired up… Which is correct?

The top and bottom tyres should be your normal riding pressure. You pump these up first. Then pump up the middle tyre. It should be of a lower pressure so that it deforms around the top and bottom tyres rather than pushing them out of the way (so causing the wheels not to be in line). This way you should get good grip between the tyres and less chance of distortion on the frame.