Just spotted this thread! Ive just been down to my local engineering firm and they are adapting a 100mm threaded 16mm round bar (studding), putting a blind hole in one end of it, tapping this hole inside plus having an extra sleeve/collar to help support the bar onto the motor shaft. My plan is the to be able to secure wheels to it afterwards with locknuts. Im having ten made to start with at £5 each. Ill probably araldite the bars to my Argos 18v Challenge drill motors. Ill put a pic on my profile next week.
Re gold motors vs drill motors. The golds are much much more powerful! Even the 24v Silver motors I flog for £5 have more power than drill motors. We use drill motors cos they have the gearbox already and they are cheap.