# How to bend the top tube



## bricke (Jul 23, 2008)

Hi everyone, I'm designing my own 29er frame but I've got a problem.
My ideal frame will have a curved top tube, I'm talking about a steel frame, but my builder and every builder who I've spoked with says that's impossible to bend the top tube because of its fragility. Even if I tell they to use a straight 1mm tube they say it's impossible. 

So, how do you bend your top tube? What tube do you use? Actually I'm in california but I live in Italy, so i can easily found dedacciai or columbus tubes.

Thank you.

Ps.: any framebuilder in the north of CA?


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## adarn (Aug 11, 2009)

this guy is in norther CA and will bend all the tubes you want:
Inglis & Retrotec Cycles | Quality Bicycles Handmade in Napa, California


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## jcaino (May 26, 2007)

I think you need to speak to some more builders.


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## briderdt (Dec 14, 2012)

Coconino does it on all his frames. Just sayin'. No big thing. Roll former, tube filled with sand.


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## bricke (Jul 23, 2008)

Ok, but what kind of tube? 0.8mm? 1mm? 1.2mm?

I suppose you cannot use a variable tube like 0.8-0.4-0.8 or things like that...


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## adarn (Aug 11, 2009)

no, you can definitely bend thin wall or butted tubes if you are good at it.


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## briderdt (Dec 14, 2012)

Give Steve Garro on Velocipede Salon a shout out, he's usually pretty good with advice.


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## Walt (Jan 23, 2004)

You can bend all sorts of stuff. The thinner the walls/larger the diameter, the harder it gets to bend without causing problems, but it's doable for even very thin, pretty big stuff (I've bent 8/5/8 heat treated butted tubes up to 32mm, for example).

If you want to do this yourself, spend some more time searching the archives. This has been discussed a lot. If you are having someone else build you a bike, and they say they can't/won't do what you want... sounds like it's time for a different builder.

-Walt


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## TrailMaker (Sep 16, 2007)

Easy;

















You've obviously been talking to the wrong people.


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## bricke (Jul 23, 2008)

If that a Columbus/Dedacciai tube?


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## BungedUP (Aug 18, 2003)

Some tubes are more challenging to roll than others, and one problem becomes length, with bike-specific tubing.

I have successfully bent butted tubing. If I remember, the butt profile was in the neighborhood of a .9mm/.7mm sort of thing. This was with a shop built roller:









The issue of length is this: Often, there is not enough length to both roll the tube, and have a safe exit when the tube comes off the roller. This is more of a challenge with butted tubing. One way to get around it is to use tandem specific tubing, if you can get it. I've also considered adding sections of tubing onto the ends, as sacrificial pieces via welding or mechanical internal connection somehow. Using straight gauge material makes this easy - it usually comes in the 0 heat treat state, so is easy to bend, and you can just get it with plenty of extra on the ends.

This brings me to another variable, which you sort of get at with you question of tubing type: Not all bike tubing has the same hardness. TT OX Platinum/S3, Reynolds 853/725, etc., are too hard to roll bend easily in their out-of-box condition. Maybe someone has a way around this, but I have never been able to get that stuff to budge in a roller. I tried with a piece of 1.5" Reynolds (725 IIRC), and it actually polished my roller dies from the pressure - I've never seen anything like it. It changed the shape of the tube a little bit, but did virtually nothing like bend it.

TT Verus, and Verus-like tubes are great tubes for building bikes (as far as I'm concerned), and are soft enough that they will roll fairly well. Reynolds 500 series tubes, and possibly 631 would be rough equivalents. I think much of the Fairing tubes (Nova generics) would also probably fit in this category.

I'm not as familiar with the Columbus alloys, but I'm sure they have a similar tube type which could be rolled.

There are other forming processes that might work as well - There are many ways to bend a tube, and rolling is just one of them.


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## TrailMaker (Sep 16, 2007)

Hey;

Of course Peter is quite right, and you will never get better advice on bikes than he will offer, regardless of topic. My answer was a bit short on specificity. My example was using generic non hardened 4130 ChroMo straight .035 wall. It was easy in terms of setup, but it was NOT a gimme. It was quite physical to bend that 1.5 tube to the radius required. The 1.375 TT was a piece of cake by comparison. I've never tried any other types of tubing, mostly because tubes long enough for my bikes are not very common.

The Harbor Freight bender I have is pretty crude, but up to the task for occasional use like it will see with me. It will vary due to distance between rollers on different benders, but with mine there was 6" of waste on each end. This goes to what Peter was talking about regarding trying to bend production length butted tubes.


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## afwalker (Apr 26, 2012)

I bend non-heat treated tubes like TT versus without too much difficulty on a harbor freight roller with swagoffroad dies. The heat treated ones like OxPlat and S3 are not going to bend easily. Having good tight dies that prevent wrinkling help.
SWAG Tubing Roller Dies Compatible With Harbor Freight Tube Roller
Non ht-------------------------------------Ht













and that was packed with sand.
cheers
andy walker
Flickr: afwalker's Photostream


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## BungedUP (Aug 18, 2003)

TrailMaker said:


> Hey;
> 
> It was easy in terms of setup, but it was NOT a gimme. It was quite physical to bend that 1.5 tube to the radius required.


I know, right? Compared to a rotary draw type bender, even using hand operation, it always seems AMAZING how resistant that little thin section of tubing can be in a roller. I guess it comes down to leverage, but still...

I think that bending tubing is really interesting. I have such a different sense of metal alloys before and after bending them. Just yesterday I was bending 6061 and 6063 pipe. I thought there was NO WAY that the 6061 was going to bend in 6.5" radius. I was shocked when not only did it do it, but it was super smooth, and without and visible cracks (even upon close inspection of the surface). I had always been a little nervous to bend 6061 previously.


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## Meriwether (Jul 26, 2007)

I've got the cheap Harbor Freight roller with Swag dies and bend OX plat/Supertherm seat tubes with a lot of effort, but it's pretty easy once you figure out the method, all things considered. The Verus 9/6/9 top tubes I've done a few of too. Longevity? No clue yet.

Bending butted tubes is seemingly a new thing though that many builders stay away from until more "testers" are out. Retrotec has been bending straight gauge for decades. Coconino bends 0.8 wall custom drawn tubing (I think that's right?).

I think you may want to consider a US custom builder if you're set on that look of the frame.


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## bricke (Jul 23, 2008)

Thank you for all this advices, very apreciated!


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## TrailMaker (Sep 16, 2007)

BungedUP said:


> I know, right? Compared to a rotary draw type bender, even using hand operation, it always seems AMAZING how resistant that little thin section of tubing can be in a roller. I guess it comes down to leverage, but still...
> 
> I think that bending tubing is really interesting. I have such a different sense of metal alloys before and after bending them. Just yesterday I was bending 6061 and 6063 pipe. I thought there was NO WAY that the 6061 was going to bend in 6.5" radius. I was shocked when not only did it do it, but it was super smooth, and without and visible cracks (even upon close inspection of the surface). I had always been a little nervous to bend 6061 previously.


Hey;

What tube specs, and did you anneal the 6061 first? I've bent it before - 1" x .095 - but after annealing. I didn't think it would bend at all in its hardened state.


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