At work we will be bending some steel pipes (1/2", 1" and 2"). We will be using a Bramley hydraulic bender, one like I haven't used in years. I can't for the life of me remember, how it is that you calculate the amount of steel actually taken up by the bend itself.

I used to know this stuff off by heart at one time, but obviously, if you aren't using this sort of theory every day, it tends to slip your mind.

What we will be doing is making up a series of pipes with 90 degree bends at each end, these need to be done without cutting or welding any bits in after the bends have been made. These pipes and bends need to be pretty much spot-on, so guessing is not really an option.

Can anyone please help?, I've looked all over the internet, but all people want to do is sell me benders.

The circumference of a circle is 2*pi*r (2 x 3.1415 x radius). There are 360 degrees in a circle, so just take the ratio- 90 degrees would be 1/4 of the circumference. You just have to know the radius of your bender. Be aware that the effective radius changes depending on what size conduit you're bending, since the inner radius will always be the same for your bender, but you need to use the mid-point radius for this calculation.

If it's a REALLY complicated bend, I'll just draw it in CAD and measure the arc-lengths there instead of trying to calculate it all by hand.

I just looked at my "Ugly" book. He has a lot of stuff but the best tip was to mark a piece of scrap pipe of each size, bend it with your particular bender and see what the "take up" is. In real life, if you make it "long" on both ends you can cut that one to fit and you then know where the rest should be bent. I have done that before myself (starting "long") on a complex piece and cut it down to fit. When I was piping the lights into my screen cage I admit I was way over my head on this bending and I had lots of scrap but if you didn't know how many cork screws and crooked saddles I threw away you would think I knew what I was doing ;-)

Yeah, I have the Ugly's Handbook here, (courtesy of Bill A a few years back) and it is the gift that keeps on giving. Damn, have I learned a lot out of that book, I carry it with me everywhere I go. Formulae, Trig, you name it, them books are always good value.

#189464 - 10/09/0907:56 PMRe: Need help with bending calcs
[Re: Trumpy]

FWIW, I use 'Ugly's' as the text for the 'Basic Electricity' course that I teach at UCVTS. It's a 'Great Little Book', starts with Ohm's Law & goes on from there, plus it's a relatively inexpensive book.