Looking into making a roll bar for the haynes roadster and I have just had a word with my local steel stockist and he says that you cannot bend standard seamless tube without it cracking or collapsing. He says you have to use annelled steel tube. Is he right, as anyone had problems bending seamless tube.

The tube is 50mm with a 3mm wall


Regards John

[Edited on 2/7/08 by jabs]

Sounds like twaddle to me - BUT how are you going to bend tube with that kind of wall. Do you have a hydraulic mandrel bender?

Depends what sort of seamless tube you have. 'As drawn' tube is very difficult to work without cracking or tearing. For this reason tube is often annealed or normalised after drawing to make it suitable for bending etc.
On the spec of the tube you should have a suffix

BK = As drawn
NBK = Normalised
GBK = Annealed

ETA If you find you've got BK then you will just need to anneal the section you want to work.

[Edited on 2/7/08 by MikeCapon]

quote:

---

Originally posted by SeaBass
BUT how are you going to bend tube with that kind of wall. Do you have a hydraulic mandrel bender?

---

He's talking out of his rear orrifice...

however - you do need a mandrel bender and 3mm thick CDS is tough stuff....

you need a tube bender not a pipe bender as the dies are the wrong size - but if you do a search on the site you should find loads of info regarding this.....

I use NBK seamless, bends nicely, I have also bent as drawn seamless and it was also fine although it took more effort to bend it.
As long as you don't try to bend a tight radius it seems to bend okay, you will need a proper tube bender to do it though, these 12 tonne hydraulic pipe benders from Machine Mart and the like aren't much cop

Cheers
David

[Edited on 2/7/08 by Minicooper]

quote:

---

Originally posted by MikeCapon
Depends what sort of seamless tube you have. 'As drawn' tube is very difficult to work without cracking or tearing. For this reason tube is often annealed or normalised after drawing to make it suitable for bending etc.
On the spec of the tube you should have a suffix

BK = As drawn
NBK = Normalised
GBK = Annealed

ETA If you find you've got BK then you will just need to anneal the section you want to work.

[Edited on 2/7/08 by MikeCapon]

---

Is this the type of bender to use

http://cgi.ebay.co.uk/NEW-12-TON-HYDRAULIC-PIPE-BENDER-UP-TO-2-DIAMETER_W0QQitemZ200233410455QQcmdZViewItem?hash=item200233410455&_trkparms=7 2%3A12%7C39%3A1%7C65%3A12&_trksid=p3286.c0.m14

quote:

---

Originally posted by jabs
Is this the type of bender to use

http://cgi.ebay.co.uk/NEW-12-TON-HYDRAULIC-PIPE-BENDER-UP-TO-2-DIAMETER_W0QQitemZ200233410455QQcmdZViewItem?hash=item200233410455&_trkparms=7 2%3A12%7C39%3A1%7C65%3A12&_trksid=p3286.c0.m14

---

Thats what I used for mine no problaymos but why the expense of seamless.
Cheers,
Bob

[Edited on 2/7/08 by splitrivet]

Well Chris's book says you can use seamed or seamless but from other threads thought seamless was best or is that only if you go serious motor racing

my race car builder friend says you should lube larger diameter tube to prevent it from tearing in the die

alternativly fire an email of to chris at mnr Harrogate.

They have a CNC mandrel tube bender that will be able to do you a hoop to your spec.they have CDS or T45 ( both stocked ussually ).

just over the hill from the 'Golf balls' Harrogate Skipton Rd.

I spoke to mnr, they will not make it as per book but want a signed letter stating the height and they will not supply unless they are certain it is the correct height for the driver/seat configuration. Suppose protecting their bottom and my head in-case of an accident.

which makes blooming good sense how ever you look at it.

In a week or two i'm going to be sitting in my car with the girlfriend holding a plank from the front of the chassis to 2" above my helmeted head. She'll then measure a height so i know how high to make my roll bar.

I've been in car crashes and rumour has it survived - i want to keep doing so.

quote:

---

Originally posted by jabs
I spoke to mnr, they will not make it as per book but want a signed letter stating the height and they will not supply unless they are certain it is the correct height for the driver/seat configuration. Suppose protecting their bottom and my head in-case of an accident.

---

quote:

---

Originally posted by MikeR
which makes blooming good sense how ever you look at it.

In a week or two i'm going to be sitting in my car with the girlfriend holding a plank from the front of the chassis to 2" above my helmeted head. She'll then measure a height so i know how high to make my roll bar.

I've been in car crashes and rumour has it survived - i want to keep doing so.

---

quote:

---

Originally posted by Dave Ashurst

quote:

---

Originally posted by MikeR
which makes blooming good sense how ever you look at it.

In a week or two i'm going to be sitting in my car with the girlfriend holding a plank from the front of the chassis to 2" above my helmeted head. She'll then measure a height so i know how high to make my roll bar.

I've been in car crashes and rumour has it survived - i want to keep doing so.

---

Girlfriend?
Holding a plank over your head?
In a week or two?

You and your long-distance plans.

---