My 24" Bedford UW has a crank length of about 127.5 mm. It’s a standard 24" UW with a 24x1.75 street tire.
A crank length of about 137 mm would actually give the same crank ratio on the 26" as what I have on my 24".
The club I’m in has a 26" UW and it has really long cranks. I don’t know what it’s crank length is, I just know it’s long. It seems to be easy to ride with the long cranks. It would probably be better to error on the side of too long rather than too short for a general purpose 26 UW. Maybe a crank length of 150 or so.
I went the length of my hall about 3 times before it broke.
The plates covering the cranks weren’t thick enough metal and allowed the crank-ends to move underneath the plates. The plates were fine for vertical pressure on pedal (i.e. crank-end vertical) but horizontal pressure just made the crank-ends roll over within the wheel and bend the metal plates.
I’ve ordered me an UW pedal boss kit from unicycle.com. Then I’ll start again!
I’ve seen many pictures of UWs built this way. Does this design require a stronger rim, as compared to the disc style Udubs, because it’s only being supported by four points?