Bending Pipe and Tube for fun and profit

[andyrennison]

Well, maybe not profit.  I have read all sorts about bending tube and pipe in simple "clarke" benders. Some of this information is contradictory.  So I have decided to do a little experimentation and put the results up for discussion. Maybe we can collectively come to a "best practice" result???

So I have started with 1" mild steel ERW pipe.  Thats 1" Internal diameter, 1 3/8" External diameter.

I bent it to 90 degrees in a single operation with the wheels in the outermost position.  The results were underwhelming.  The image is below.

[spanners]

oooop,s  kinky 

[andyrennison]

So I made a few changes.

1. I filled the pipe with sand. This was acheived by
   a. Sealing one end with insulation tape, - yes the pressure at the end will be that low!
   b. Filling the pipe with water
   c. Carefully putting wet sand into the open end until the pipe is full of sand and the water displaced
   d. Sealing the open end with tape


2. Modifying the bender.
  a.  Drill a hole into the former centrally  below the forming curve
  b.  Create a strap to fit over the pipe that can be secured with a bolt through the hole at (a)
  c.  Weld a nut to the top of the strap and fit a bolt so that the pipe can be held firmly in the former.

The logic behind this modification is that the pipe rises out of the former as soon as the bend starts, so the pressure is not exerted in a progressive manner around the inside edge of the bend as it forms.

To make the test as tough as possible the idler wheels were placed at the most internal setting, and the pipe was bent to 90 degrees, the results are below.

[andyrennison]

there are a few things to comment on here. 

We did not use a bolt to hold the strap in place, but a bar, this slipped out towards the end of the bend which may have reduced the efficiency of the hold down strap

The bend seems to be heading in the right direction, but the idler rollers are now causing a problem. The pipe appears not to have moved through the rollers but instead dug into them.

Others have suggested putting some form of load spreading shim between the idler rollers and the pipe.  That will be the next addition to the test bed.  We will also lubricate the pipe.

After that we will experiment with progressively moving the idler rollers in (rather than starting at the innermost position)

[andyrennison]

oooop,s  kinky 

Indeed

[spanners]

its a crying shame that my dad passed away a while ago  as he was an expert of the old school and could even cut a pipe to lenth before bending it and after putting it through the bender it would come out within 1/16 of an inch of where it should be  and that was on pipe ranging from 1/2 inch upto 8 inch  it was an art to watch

i still have his  TUBELLA hydraulic bender upto 4 inch  he had a screw wound bender before that

[hunter]

Hi Andy,The tube you are using is only 3.1/6"wall,So you can't expect to get a good bend no matter what you try.To get anything like a decent bend you'll need 2,5mm wall thickness.

[andyrennison]

Hi Hunter.  This is an experiment in getting the best from what I currently have to find the best set up for the bender.  I have some CDS coming on Friday.  However, As the current pipe is 3/16" wall thickness that comes to about 4mm does it not, certainly it measures over 3 mm?  Or are you saying that the wall thickness needs to be thinner to get a decent bend? - i'm confused now ( Always actually )

[one arm bandit]

no you was right first time round the thicker the wall the better the bend. is good to have a play before hand,no point in wasting the good stuff.

[Dslam]

Please keep going with this. I will begin building a new frame for a project later this year and your experiences will be invaluable to me. Keep bending that tubing!!

[nabsim]

Andy I was going to try cutting some larger pipe to work as sleeves on the bit you want bending, I invisaged the 'sleeves' would be on the rollers but I have never got round to trying it. I thought that may eliminate the marks made by the rollers. This is just my logic though so may be total rubbish

[digger06]

tbh, looks like the corners are too sharp to me, are you actually gonna use 90 deg bends any where?

what did you expect trying 90deg bends on the inner roller settings,? its gonna leave roller depressions doin that, start from the outside in,like u said...

buy yourself an engineering book, itl show you how to bend pipework like spanners dad, its not hard once you know,
you may have probs bending cws in a erw set up bender, cws will react differently to erw, it may flatten even more, so all these experiments may be useless anyway, get extra cds and try with that

[haggis]

If you have a little time on your hands have a butchers at THIS THREAD It not on here but it shows a wealth of information on bending tube etc etc. How to do it accurately. How to stop the kinks and also how I built a V8 trike.
I have been bending tube for the best part of 30 years and most of my experience is show in the thread. I will gladly answer any questions you have.

My best advice is to purchase a good quality bender. In fact the one in the build is for sale as I have just bought a slightly better one.

[andyrennison]

Hi Guys. Yeah, Digger, I rather expected that, What I am trying to do here is find out how for myself how the various parameters interact with the kit I have, so i understand how things work together.  My thinking is to get to a point wher I know what can and can't be acheived.  And maybe the next guy to buy a bender knows more about what to expect than I did when I bought mine.

I would like to bring the front frame up perpendicular to the road, that will require a pair of 90 degree bends, apart from that, no, I won't need 90 Deg or sharp bends.

Haggis, that is a facinating thread, looks like an good evenings time to read through it all.  And thank you I will certainly ask

The CDS arrives tomorrow - So I shall be having a lot of fun this weekend

[one arm bandit]

great thread of the v8, the yokes and forks look very smart indeed,      andy i only had two nearly 90 on the lower frame rails the cds kinked a bit so i give it a dam good gusseting which insedently made it look better.