60tbirdrick said:
I built this one and it works pretty good. It only cost about $300.00 in materials.
http://www.harwoodperformance.bizland.com/1941buick/Editorial_20.htm
That's a good looking design! Very nice of Mr. Harwood to provide such an excellent drawing, too.
I'm well into building my own and would have guessed your materials cost was high, before I started. That's about how much I've spent on new steel and will have some left over, but I used some that was already on-hand, too.
In his design, the vertical piece and pivot are at a fixed height. I'm trying to make mine adjustable by welding the "rotator sleeve", as he calls it in his drawing, to a 2" (nom.) pipe that fits inside a 2-1/2" (nom.) pipe. The fixed one is 34" and the one with the rotator sleeve is 32". The intention is to allow an upward extension of 10" - 14" while keeping plenty of the smaller pipe still inside the larger one.
My garage has an 8 ft. ceiling, so the maximum sensible height of the rotator would be 48". That 48" radius, 96" diameter, quickly gets eaten up by a bare minimum of 3" clearance at the floor for the rotisserie legs (without casters) and 9" clearance at the ceiling for lights. My '49 Olds is about 72" wide at its widest. So far, so good.
The Olds is 54", floor to roof. Geometrical center is therefore at about 27" up-down and 36" left-right, and the center of gravity is probably closer to the floorboard. Since I can't really calculate where that c.g. is, I'm also allowing for being able to adjust the drop of the body support frame below the rotator sleeve. (Think of an upside-down "L" with one leg stuck into the sleeve and the body support frame attached somewhere along the other leg).
Considering the car body as a nice, square-cornered rectangle from the end, the diameter of the cylinder it's going to take up as it rotates is the length of the diagonal of that rectangle, roughly. Making use of the handy calculator at
http://www.mathnstuff.com/math/spoken/here/2class/80/math.htm#rectd (uses javascript), I get a diagonal of 90". Bummer.
It's going to bump something, somewhere, just like Mr. Harwood ran into in his garage. It may _just_ scrape by if I raise my lights to be flush at the ceiling and raise the rotator sleeve to a height of about 46" - 47".
I may tie the two rotator stands together by running a couple of 2x2 11 ga. square tubes under the ends of the base at each stand. That would eliminate that 3rd leg with the front wheels in Mr. Harwood's design. That leg directly reduces the diameter of the space available for the body to swing in. Splitting it into two legs spaced out at the ends of the stands' bases and giving up the casters gives more swing space around the pivot, all the way down to the floor.
My "engineering" is by guess and hope. Each of the adjustment points will be pinned all the way through, not just jammed by friction with a lock-bolt. I don't want anything moving anywhere that I don't make it move. It's not that much trouble to drill a new hole in the pipes for a grade 8 bolt when changing to a different body. If I survive this thing, maybe some real engineer will review it to see if the survival was by luck.
Here's a link to a discussion about rotisseries from the Knowledge Base:
http://www.hotrodders.com/forum/tilter-rotisserie-ramp-79099.html
[edited to add:]
Added a diagram. The pasted car body image doesn't have the correct perspective for the diagram, but helped me visualize what was going on.
[edit, again:]
D'oh! The diagram I attached before didn't show the rotisserie. Attached another one, from my journal.