Well, July is doable but close, depending on your crew and shop. 15' diameter is a fairly small TT so is it smaller than 2 sheets of ply in both directions and 2 professional
level carpenters with proper tools and equipment, should be able to knock it out in 40 hours or less. You can drive it as a rim drive with a tire or a cable/chain drive. Decide on the method of drive before building as the construction of the frame is different. Also figure where the motor and drive will be located on your
stage, it might make a difference on the construction if there are obstructions or you need a path for scenery or actors
etc. For a 15' TT, running at, say, 4 rpm max, a 3/4 hp should do, 1 hp will be fine. More hp is ok but unnecessary. Spend the money on a good center bearing and have a center shaft and mounting plate welded up at a metal shop if you do not have welding capability in your own shop. Take the time to design or have designed, your drive
system, that is just as important as the TT itself and should be the first thought, not the last.
You mentioned noise. The motor is rarely the noise maker. It is usually the casters and the rumble they make. Inverted casters, casters on the floor pointing up are usually quieter.
I know this is a very quick gloss over,hope it gets you going in the right direction. Do check the past threads, they will help you a lot.
Michael Powers, Project Manager
ETCP Certified Rigger -
Theatre
Central Lighting & Equipment Inc.
675 NE 45th Place, Des Moines, Iowa, 50313