I just saw an old Huffy 3 speed bike with internal gears and was wondering if this hub or a similar hub could be converted to a unicycle hub. Has anyone tried this? Thanks for the input.
It is possible to turn a 3 speed bicycle hub into a 2 speed fixed gear bicycle hub. You end up with a fixed gear bike that can shift between two gears.
Sheldon Brown has a web page that describes converting a Sturmey Archer 3 speed hub into a 2 speed fixed gear. The Bikesmith in Seattle also did three speed hub conversions to two speed fixed gear. The Bikesmith recently closed up shop, but he still plans on making the two speed fixed gear hubs. The challenge is getting in touch with him now that he doesn’t have a shop.
So yes, it can be done. But you end up with a bicycle hub which would only be useful on a giraffe unicycle. Getting it modified with a pedal spindle so you could put the hub in a standard unicycle would be difficult at best and impossible in practice.
A two speed fixed gear bike would be quite a kick though. 
On the subject of shiftable hubs, I first contacted schlumpf innovations the manufactuers of two speed bottom brackets,
April 2003 - a day after taking delivery of a my coker.
Being the owner of a recumbent trike with a mountain drive bottom bracket (1 to 2.5 step down gear), which can be pedalled backwards, and gears are changed by pushing a button in the middle of the axle with your heel, and being aware that schlumpf also make a speed drive (1 to 1.65 step up), I decided to contact them about a geared unicyle hub.
Schlumpf replied promptly, telling me that they had just been
thinking about the same thing themselves, and a geared hub would take about twelve months to develop.
In May this year I checked their website (www.schlumpf.ch) and they have indeed made a shiftable hub. It is still in the development stage and it is very narrow. I e-mailed them giving them the specs for a hub to suit a remanufactured coker (self-interest) and they replied that they would be making several variations of their geared hub.
Hope this may be of interest.
d00dz, there is this harper fella, he made a shiftable hub, he said it wuz gonna be made available 2 the public 4 under $50!!!
w00t
(joke)
john
I found that schlumpf website too- it will interesting to see what the cost will be on the geared hub.
Based on the price for the bicycle parts he makes I’m expecting a price of at least $450 (USD) for the unicycle hub with cranks. I wouldn’t be surprised if it was more than that due to the small unicycle market compared to the bicycle market.
Wow, this would change everything. Our dream may one day be reality. A remain a very hopeful, --chirokid–
Uhm, I think Sturmey Archer made a 3 speed fixie a long time ago. But they’re hugely rare. I think Sheldons got something on it somewhere. I think it was modeled the ASC? (maybe?)
Yup. Sheldon Brown has a page describing the Sturmey-Archer ASC Three-Speed Fixed-Gear Hub. Quite cool. I didn’t even know such a hub ever existed until I went browsing around Sheldon Brown’s site yesterday.
Too bad it’s a bicycle hub and not a unicycle hub. 
You could always make a real short giraffe with it. I’m up for it. How bout it, science?