Rollcage - How to calculate a multi-plane bend??

[2MEKE]

I've tried bending the A hoop for my rollcage but obviously my calcs were wrong looking at the bent mess of tube on the shed floor

So...can some explain the maths to work out the angle of the bends AND the angle the tube needs to be rotated to form it up like the sketch below?? The legs are vertical.

[kbushnz]

Have a read thru this article. http://www.hotrod.com/techarticles/body ... ewall.html

Google search works good.

[wsr4x4]

Start in the middle and work your way out ,trail an error you w
ill pick it up

[churchill]

Whats your bend radius and tube diameter?

[churchill]

Just happened to be on solidworks over lunch.







If I've read your drawing right the angle should be the grey one on the pic below. 147.5º

[2MEKE]

Nice...wish I had access to SW
What I'm really wanting to figure out is after putting in bend B the tube is moved to the start point for bend A of the but how many degrees do you rotate the tube so the top of the cage will finish perpendicular to legs??

Whats your bend radius and tube diameter?

CLR = 88.9, tube OD = 33.4

[coxsy]

you gain on a bend the outside dia of the pipe

[churchill]

Yeah SW has it benefits, especially doing what your doing it can make things a bit easier.

Ok, I think I know what you mean, how does an angle from horizontal for the top pipe when you are about to bend A sound? I'll have to do it at work tomorrow though.

[2MEKE]

That sounds good

Just been to the shed to try an idea on some scrap tube...

1. bent A to 80 degrees,
2. moved the tube through to the start point for bend B
3. rotated the tube 75 degrees anti-clockwise (looking from the front - it's a protools/jd2 style bender)
4. bent A to equal 30 degrees

A test fit shows it's pretty close...maybe just luck tho

[churchill]

Ah I understand how you do it now!

According to SW you are really close.



First bend B to 76.9º
Move through to A startpoint.
Rotate anticlockwise 69.2º
Bend A to 32.5º

Let me know how you go.

[2MEKE]

Thanks heaps for CADing that...it confirms I'm on the right track.
The actual measurements not quite those on the sketch but at least I know how to work it out now.

Now back to shed I go

[churchill]

No worries, happy I could be of some help.