Need help making a rim into a pulley

[Wrench]

In the old days they just used a leather belt sewn together. This allowed people to run belts off car rims, M/C rims and bicycle rims

 

[Wrench]

Kinda sounds like ya need an Accu Link V Belt.
They can be ordered by the foot to make any length ya want, These are Old School style V Belts and what replaced the old leather belts. Modern corded rubber V belts replace Accu V Belts.
Harbor Freight sells an Accu V belt or www.usabearingsandbelts.com
Here are some pic of Accu V belts

 

[darwin]

He'll need a reduction motor for 30 rpm.

 

[Frogslayer]

Yup reduction motor and maybe look at a dryer belt. How do you plan on overcoming the freewheel? Or are you just going to spin it backwards and hope the chain stays on whatever gear you want cause the derailleurs won't be guiding the chain on to the sprockets. Post up a pic of the rim and we'll be able to suggest possible belts better.

 

[Frogslayer]

And why do you need so much power? 1hp is quite some power for art, and probably like 700 watts of power. Cheap to run for short bursts but expensive to run all the time