i saw a 3 wheeler unicycle and have to have one. and after realising my
lack of money ,i decided it needs to be built, and i geuss i just
wanna give it a go.
I have read a few things such as the wheels may slip .e.t.c. but a 3
wheeler still seems easier than trying to build a girraffe becuase the
weight goes through the wheels as well as the frame, so i geuss the
frame doesn’t have to be as strong.
I’m gonna scrounge my parts of bicycles in general, jus do it as cheap
as possible, has any one got any tips/advice/warnings worth reading?
make sure when you put the tires on they are flat. when you put them on flat and have them touching or almost touching, once you put air in them, there will be a lot of pressure on the tires and they wont slip.
also, have fun building it, post a picture or a link 2 one if you can after you’re done
Don’t get the wrong impression you can build a “weak” frame because the wheels support each other. The wheels do not support each other. You jam them together as tight as you can for traction, but they don’t hold any weight. Your frame still has to do that job.
Also depending on your wheel size, a 3-wheeler will be taller than a 6-footer. Do the math. Remember your pedals will be on the top wheel, and you’ll be however high above that you would be on any other unicycle.
3-wheelers are very visual, especially if you put something in the wheels so people can see them rotating in opposite directions. They’re great in parades, and unlike a regular giraffe they’re much better for wheel-walking. But they are also heavy, and can be damaged if allowed to drop. Another reason why I guess it needs to be at least as strong as a giraffe frame…
A 3-wheeler frame also is not trivial because of the strong tendency for the wheels to de-track. The wheels have to be strong and stiff and the frame needs to align them properly and keep them in line.
Here is a pic of the 3 wheeler that I built last fall (no pun intended) I departed from the usual design by using a 5in idler as the center wheel.
I found that using high pressure tires reduced slip with the least amount of rolling friction. I have Kenda Qwest 100psi tires on it.
My frame is made out of 1-1/2"x3/16 flat strap steel.
Al Lieffring, do you have a gallery? I’d like to see some close up pics of how you attached the top and bottom wheels to the frame. Did you use bearing holders? The bottom wheel is a regular 20" bike wheel right? I bet it looks great with a yellow frame!
I’ll have to go and find up how the setup works on the photo gallerys here. When I do I’ll snap some pix and post them.
At the upper wheel I used main cap holders. Because I didn’t think the dinky 6mm bolts could take the load I bolted a bracket over it to hold the upper and lower frame together. I have oval slots for the center axle and at the bottom dropout I have a backwards tensioner. Screws to push the axle up instead of pulling like a chain tensioner. The pressure needed to keep the tires from slipping tend to spread the wheels apart.
Cro-Moly (e.g. 4130) is popular, although this is not cheap in the UK.
or best cost:
Mild steel, although you will pay in additional weight as the wall thickness will be much greater.
Round tube will flex less than flat, for the same weight. Flat might be easier to work with, although I have never used it.
If you have limited welding & fabricating experience I would suggest making a few normal frames first & experimenting, personally I am not ready to build this level of project (although it is on my maybe list). Also whatever you budget it as costing multiply by atleast 3!
You’ll notice if you look closely at the frame extenders that they have small holes for the axles of the bottom two wheels. These holes are just large enough to accomodate the axle. When I drilled the plates I was using a handheld drill and the bit wandered slightly while starting the hole. Also, the top hole was punched out with a press at the place I bought the steel. Their tolerances were so loose that it took them many (maybe 15)attempts before the results were anywhere near acceptable. Lucky for me they only charged me for the ones that were usable.
Anyway, when you figure that there are two holes on each side of the frame plus the two large holes for the top wheel and the 4 holes for the bottom two wheels, the loose tolerances add up. To get the whole thing to even bolt together required leaving the bolts loose until it was all assembled then gradually tightening everything up. Once tightened there was a twist to the frame.
One thing that this got me thinking about though was –
What if you intentionally rotated the wheels 45 degrees around the y-axis. The bottom wheel would be 90 degrees offset from the top so that when you pedalled forward you’d move to the left and backwards pedalling would move you to the right. I’ve never seen anything like this before so perhaps this is your chance to be the first!
The SH frame is engineered to much tighter tolerances and fits together perfectly. This, combined with the fact that the aluminum legs of the SH model don’t twist like the flat steel blades makes for a significantly more solid ride.
It’s also worth mentioning that with the SH design there are only three pieces to the frame - the seat tube/crown and two legs. With the schwinn modification there are five pieces to the frame - two frame legs, a seatpost, and two extended frame legs. Each of these are connected in such a way as to allow movement (even when tightened down some movement could still occur). The SH frame, when assembled has no movement at any of the assembly points.