Does anyone have any experience or knowledge concerning building giraffes out of BMX cranksets and hubs? Building the frame is a non issue for now, but I want to know if i can use, say, a profile hub and attach a sprocket instead of a freewheel to achieve a 1:1. I think that a normal bmx crankset can be incorperated into a frame with no problem, but if anyone knows better i would appreciate some advice.
Weld the freewheel so it’s not a freewheel anymore.
Just put a few tacks on the part of the freewheel that spins, or a bead around it. Depending on the metal, as long as the hub isn’t aluminum, weld the freewheel to the hub also, incase it loosens off.
If i do that I’ll have a 45:9 or 45:13 or so kind of gearing ratio instead of a 1:1
then you will just go really fast, thatd hurt if u bailed though. 
Obviously you’re going to have to replace atleast one of the sprokets, if not both to get straight gearing. Other than that you should be able to use all the bottom bracket chain and wheel components, so you only need a frame and saddle to complete your giraffe.
I’ve always thought you could get away with just mounting the saddle on the front header tube, and changing the gearing for a close-ish ratio. If everything else was left in place then you’ve got a ridable BMX (albeit with a fixed hub), and a giraffe that’s hard but not impossible to freemount.
STM
Since BMX cranks are long, you don’t want to have a 1:1. I built one with about a 1:2 and it works fine.