A BC wheel with hand cranks and a freewheel hub sounds like a fun vehicle to ride! I would like to try it!
Today’s work:
Looking good!
I’ve been making a reinforcement plate for broken Qu-ax Profi saddle and a plate for self-made long seat post while my friend drilled a stem on a lathe to grip ‘bottom bracket’ in it
The penguin incarnation is ready and tested
The penguin incarnation is ready and tested. I managed to ride it right away with ratio 1 : 2,15 (13 to 28 sprockets; 20" alike 43") - optimal in my opinion.
Displacement of the saddle back from the center is OK - I didn’t feel it when riding.
Remaining work:
- taking up the backlash of sprocket wheels
- making a chain of required length for giraffe/handcycle incarnation
- painting the frame
Video of the 1st test:
That’s a sweet penguin! Congratulations on this project! It looks a little bit like an idea I had to turn a trials bike into a penguin and I’m glad to see your design in action. Thanks for posting the video! It’s making me rule back in a freewheel penguin as a possibility down the road. Is the sprocket protected by the saddle during a UPD?
Very cool! I love the creativity, and can’t wait to see the “hand-cycle” mode in action.
Yesss, I love it . Elevation and speed… you’ve got them both on that penguin. It must feel like your flying up there. Great job Dimah!
I’m sorry I didn’t get the question 
What do you mean by UPD?
upd = unplanned dismount
Thanks unibokk!
waaalrus, yes, I think it’s protected by the saddle and by cranks/pedals:)
Does anybody have an idea how to attach sprockets to crank or where to buy a proper cotterless crankset (maybe from a giraffe) with 22-35 cogs (maybe aiexpress or some other Chinese store)?
25t and 28t bmx sprockets are common and inexpensive. They show up on AliExpress as well as eBay, Amazon, etc. Because of the small size, there is just one bolt that attaches the sprocket to a matching style of crank arm. (Sometimes listed as “bolt drive” sprockets.) You can get “Euro” bottom bracket bearings to fit a standard road or MTB bottom bracket shell for those cranks. Depending on what length you need, finding the cranks in a suitable length might be the challenge.
Thanks, but I’ve already considered this option. I’d like something compatible with cotterless of ISIS (but in case of ISIS I’d have to buy a new bottom bracket).
Now I have part of a cassette like this -
- welded to the crank. Problems are:
- cassette’s spline diameter vary so it’s hard to arrange sprockets and spacers in the right sequence
- backlash between cassette and sprockets
- one cog of the 28 t sprocket broke off and I don’t have a substitute
So I’m looking for other options. There are so many standards of b@cycle cassettes or cranksets and I’m confused. A perfect option would be if sprockets could be easily mounted or changed.
Shimano-style cassettes (“Hyperglide”) use the same spline for every sprocket. It is easy to make custom sets or to replace an individual sprocket in one. I have even mixed different brands of sprockets.
I think Uniglide is my choice
But I don’t get it. On older b@kes these splines were part of a cassette. Are they part of a hub nowadays? Can I buy it without a hub? Do they even separate? I don’t dig this b@ke sh#t…
Yes “freehub” designs took over 20 years ago or so. It’s hard to keep up when things keep changing like that, isn’t it? 
A big factor was the length of unsupported axle for a freewheel having 7 or more cogs, with 130 mm dropout spacing and a highly dished wheel. The freehub design puts a bearing under the outer end of the cassette, as far outboard as it can go.
Yes you can buy the freewheel part by itself. Or steal one off the hub of a junk wheel. It unscrews from the hub, with a 12 mm internal hex if I’m remembering correctly. It’s been ten years or so since I’ve disassembled one but I don’t remember any provision for it working in a fixed-gear situation. Check me on this but I think you could spin it loose with back pressure if the freewheel is disabled.
Yes, I remember bent axles on my old b@kes. I even managed to brake one axle somehow.
The way I see it is taking the freewheel part off and welding only splined cylinder to a crank (for leading sprockets, not where the wheel hub is).