A Sheave

It may be worth having an overhead door installer visit your sight. I assume they will have the parts you need for repairs.

The exact sheave may not be available but there is probably one on the market that would work. Others must have done this before you somewhere.

The bore diameter and key size is the important thing here as well as running clearance. The exact diameter may not be as critical but groove size is. Safety first.

If your sheave diameter is smaller, the door will travel slower but you will have more available torque for lifting.

If your new sheave is larger, the door will open and close faster but the function will be harder on your motor.

Worst case scenario is to have a machine shop make a new sheave using your old one as an example. Look into the hardness of the sheave, you may have to have it heat treated. If so, then material selection could make heat treating easier or harder.

Massey,Thanx. I was kinda vague, sorry. The idea is to support the counterweights from above using coil rod or wire rope to a HSS rectangle tube, or channel or.... The 1966 drawings have been scanned, copied, printed, marked on scanned.... etc. and most of the dimensions are illegible, even the BOM. What we are attempting to determine is if there is enough space to get the hangers inside. In this case, without being dorogtory.... Asking the contractor to ascertain this information is at best not reliable.
I was kinda hoping a "seasoned" engineer might see this and reply, "Oh, yeah, a PP5003, those babies are such and such a diameter and so and so in width...."
Thanx, none-the-less

Found this...

http://www.overheaddoor.com/commercial-door-operators/Pages/operator-rhx.aspx

Does the sheave drive something else where the diameter of the sheave is critical or is it just changing the direction of the wire rope. I.E. from a horizontal run to a vertical run?

If it doesn't drive something else, you could just get a 2 groove sheave with the proper I.D. and an O.D. close to the original size?

It's kind of difficult to determine which of the sheaves in your 2nd picture is the one you're talking about?

We have quite a few old rollup doors that appear to have the same operator.

If you will send me the door manufacturer and/or door operator OERM along with the size and any numbers you can get off the control boxes I may be able to locate some drawings in our archives.

Thanx, all. We did manage to obtain s cleaner copy of the 1966 drawings of the door and got the removal worked out.....