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Need help with bending calcs #185819 03/30/09 02:10 AM
Joined: Jul 2002
Posts: 8,379
Trumpy Offline OP
Member
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.

Thanks.


Tools for Electricians:
Re: Need help with bending calcs [Re: Trumpy] #185821 03/30/09 12:26 PM
Joined: Jul 2004
Posts: 9,569
G
gfretwell Offline
Member


Greg Fretwell
Re: Need help with bending calcs [Re: gfretwell] #185823 03/30/09 01:09 PM
Joined: Mar 2005
Posts: 1,213
S
SteveFehr Offline
Member
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.

Re: Need help with bending calcs [Re: SteveFehr] #185824 03/30/09 10:29 PM
Joined: Aug 2007
Posts: 853
L
leland Offline
Member
Beyond my scope.

Perhaps for missile defense we would need to be that precise.
Otherwise... Damn close is good!

Re: Need help with bending calcs [Re: leland] #185825 03/31/09 12:23 AM
Joined: Jul 2004
Posts: 9,569
G
gfretwell Offline
Member
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 ;-)


Greg Fretwell
Re: Need help with bending calcs [Re: gfretwell] #185830 03/31/09 11:16 AM
Joined: Jul 2004
Posts: 783
L
LarryC Offline
Member
"screen cage" ?

Larry C

Re: Need help with bending calcs [Re: LarryC] #185832 03/31/09 12:17 PM
Joined: Jul 2004
Posts: 9,569
G
gfretwell Offline
Member
Screen cage = Aluminum pool enclosure.


Greg Fretwell
Re: Need help with bending calcs [Re: gfretwell] #189437 10/07/09 11:45 PM
Joined: Mar 2008
Posts: 27
G
gpsparky Offline
Member
Take your Hickey bar along just in case


Sometimes not getting what you want can be an incredible stroke of luck.
Re: Need help with bending calcs [Re: gfretwell] #189440 10/08/09 03:19 AM
Joined: Jul 2002
Posts: 8,379
Trumpy Offline OP
Member
Originally Posted by gfretwell
I just looked at my "Ugly" book.

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.

Re: Need help with bending calcs [Re: Trumpy] #189464 10/09/09 06:56 PM
Joined: Apr 2002
Posts: 7,233
HotLine1 Offline
Member
Mike:

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.

Also, Benfield has a good bending book.



John
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