Thanks, Mulva. Was it difficult to find tubing that would telescope without binding yet not be too loose?
What size beams is everyone using? S beams or W beams? I was thinking in terms of an S8 x 23lbs/ft.
im a little thin on details, its been a few years and I lost my plans with the last computer crash, but as I remember no troubles with the tubing, its just standard 4" and 3.5" sq tubing, 3/16 wall(I think my local supplier had to order the 3.5", he didnt stock it), it fits well with no interference from the inside seam.
the beam is an S beam I already had on hand, 6x i don't remember lbs/ft, it spans just over 9' if I remember correctly, which was enough to allow me to drive my truck through it without pulling the mirrors in. I sized it for 3 ton, but I only have a 2ton hoist on it.
it is a heavy thing though, I have to use the front end loader to change the height setting on it, so its not as "mobile" as I had originally hoped for.
Over here in the UK you can buy telescopic tubing made to tighter tolerances so that next size pairs slide smoothly inside each other. I imagine that such can be found in your area. Around 20% cost loading compared to the standard stuff and a bit over half price of cold drawn seamless which, in my experience, slides just fine. If the sizes and wall thickness appropriate to the load can be got I'd pay the extra. Had to make a 3 ft long drill to clear a couple of rough patches inside when doing a "materials supplied" job to get proper action on one part. A bit of smoothing on the outsides too. Prolly worked out at around 10% chance of problems per metre in my case which was frustrating but no major worry.
Thanks Mulva and Clive - all very helpful information! -Chris