Finding tube length

Hey all. I have some ideas for a rear tube bumper but have some questions. I have access to a nice tube bender at work, and I’m a welder, so not so much of an issue putting it all together. I’m just concerned on how to find out how much tubing I’ll actually need.

For example, let’s say the main tube that wraps around the whole length for the rear bumper, I want 10” on the sides, and it’s 60” across (this is all hypothetical). How do I find out how long that piece will be before its bent? And how do I find out where to bend them, so the sides are 10” and the middle is 60”? I know the radius of the bend plays into it but what’s the math to figuring out the total length of the tube, and where to start my bends.

This will help to make less mistakes and waste less tube, thus saving money lol sorry if this doesn’t make much sense. Appreciate any input!

 

d = 2 π r (θ/360°)
d = arc lenth
r should be the diameter of your tube (outer diameter)

So depends on your bend angle, your straight sections + the arc lengths will be your your max tube length
That's the math basics

There's more to it regarding your tube bender - material, hot or cold bents etc - you need to see what the machine calls for, some CAD programs help out with that

 

So *roughly* if I were using 1.25” tube, and making a 90* bend…the straight length of the tube would be 2x3.14x1.25 which is 7.85”

or do you divide the 7.85 by 4 since it’s a 90* bend?

I’ll have to ask the engineer at work to school me on this subject lol

Edit: how does the radius of the bend play into finding the unbent length?

 

watch a few youtube video's on conduit bending. every bender model is different. there's the bending radius, there's also 'take-up', which is the amount of conduit that 'disappears' into the bend. in this case, there's also going to be a 'start' and 'end' to the bend, points that will be specific to the machine model you're working with.

if you've got a bender there, there's a good chance someone really knows how to use it. it'll be well worth bribing them with a case of beer to trade the secrets. or just bend what you need.

but as always, absolute worst case, you can always just bend short sections to make the turns you need, and weld straight sections in to complete the bumper.