Design problem

well it is difficult to chose with out all specifications, material are relative to the use, so I think you'll need to do "the maths" ... first you find the maximun streght

τmax=Tc/J

T=torsion value

c= external dia

J=polar inercial moment, for a pipe or a tubing it is=pi(Doutside^4-dinside^4)/32

that you can calculate the security factor, it will be at least 8 for a rotation case....

security factor= 0.33* Tensile Strength, Yield (from material pipe)/τ max

Note: those calculations work if only you have torsion, if you have more kind of forces you must to calculate a force combination for the critial point.

I hope it can help....

Nice Avatar

Well I see where you are going, I"ll need to get the yield value or the Tensile Strenght value to find the Tmax. The "c" external dia is the same as (Doutside^4)??

This may be more spicific on what Im trying to do is how to calculate the braking point or failure force of a 3" round structural tube with a 1/4" wall thickness and 20' long. What kind of force and amount would it take to twist it until it snapped??

thank you

you must to fien the tensile strenght for yield but if you want broke it you need the ultimate tensile strenght of material... and yeah C=Doutside

normaly estructural tube is A-36 you can find more information in www.matweb.com

you mean snapped with torsion only??? well just change all for a security factor least than 1, you can iterate diferent torsions loads....

structural pipe or structural tubing?

I can ony see a difference in semantics not engineering.
I'd use anything that can withstand about twice* the torque I'm going to apply and is fit for purpose regarding cost, suitability for the required fixing methods, corrosion resistance etc.

*Or maybe more depending on how I'm applying the torque, to allow for shock loads.

Del

If you are going to power this device from a tractor's pto, you will have a lot more to consider.

I suppose it will also depend on how itchy the soil is that you need to scratch!

A pipe is measured ID - a tube is measured OD. Important to know when measuring flows and volumes.

Some may also argue that pipe is a vessel and tube is structural, but I would have to argue against that as an absolute statement. Also more often than not, tubing uses wall thickness as a controlled feature. That is; wall thickness is toleranced and has a nominal target dimension.

_{Hey! I just went to type in the symbol for cents and realized there is no key for such! When did this happen?}

Pipe follows a schedule and tubing is forgiving as to specifying wall thickness which will overtly reveal the measure of your task...