You don't have to have a rotating arm. Just install a racking arm about 1"-2" above the bottom of the conical & dump your yeast. It creates sort of a funnel in the yeast & the racking arm sits inside the funnel. When I built mine I used a 1/2" polypropylene ball valve, a bulkhead fitting, polyethylene tubing & a 90 degree fitting. Got all the parts at a Farm Store. The ball valve was ~$20. The rest was chump change.