Tripod Help Needed

Unless I'm missing something, if the legs are 120° apart, they all lie in a plane, so don't form what most people understand by a tripod.

Cheers..........Codey

You've got three Euler columns here (over 40:1 L/D ratio) and in the absence if unrestrained pin connected joints you have to assume all the load will go on one leg. Go find a copy of Roarks "Formulas for Stress and Strain" or some good strength of materials text and do your calculations. You likely cannot afford to put this structure under full load testing without having good calculations to hang your hat on.

FWIW my gut feel here is that your 6 meter long 3-1/2" dia columns are going to buckle under the 4000 lb load and maybe even under 1/3 of that.

Ed Weldon

I've built dozens of tripods. Ironically, the strongest one I ever made is also the lightest. There is a tendency to think in terms of the strength needed to handle compression loads alone and to forget to address torsional rigidity. It makes no difference how much weight the tripod can carry if it wraps up around the Z axis and then loads and unloads in a cyclical pattern.

Shape is just as important as material properties. Make your top plane triangular and your legs as trusses. the difference will amaze you.

L.J.

This example was made from a pair of aluminum crutches. It's shown holding a 4300mm Schiefspiegler telescope whose high magnifications demands a good rigid mount.

Here is a closeup. Simple design. It's the truss shape of the legs that makes it effective.

L.J.

What I understand is that you want to make tripod for site work such as lying pipes etc. You want to mount Manual Chain Pulley Block in centre to lift 2 Ton load. In that case 3" pipe can sustain the 2 Ton load.

My only comment is that your design will be hard to erect. Sch80 pipe is really heavy. Also that it would be a good idea to attach a strong 'loop' at the base of each leg through which you would thread a chain connecting all three legs together. This will keep the legs from 'sliding out' from under the load.