bending chainstays

[Rory]

Hi,
I'm working on building a fat bike, and need to bend either some
chainstays or 3/4" diameter tubes to get it around the 4.7" tire.

does anyone have any advice on how to do it?
thanks,
Rory

[jon norstog]

Rory, list:

I used to do this sort of thing - extreme bends in chainstays - by heating the tube and bending it.  I still use that method for bends over 18 degrees on a 3-4" radius in 3/4" x .035"  tubing.  And for almost any major bend in .028" tubing.


It helps me to mark the bend area with a mica crayon, and use a piece of next-size-up by .058" tubing to hold the piece being bent.  If you are careful you can get good clean bends that way, and even match them in a pair of stays.  Expect to burn up some tubing before you get it right.  The heated areas will be softer than the "normalized" tubing, and will be a little bendy.  You may want to use .049" tubing.

Good luck

jn


"Thursday"

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[Jim Merz]

> >http://search.bikelist.org(older content).

[Jim Merz]

Sorry for the empty post.

I bent Renyolds chainstays for my first MTB frames back in the day.
Thicker tubing should be easier, but these were less than 0.040" wall.
I plugged the small end with brazed on plate and filled the tube with
dry fine sand. Don't use glass beads. Pack the sand as tight as you
can then weld or braze a plate on the big end. You then use a torch to
heat the tube where you want to bend it. Get an even dark red where
the bend needs to be. The sand helps keep the tube from buckling. Once
your done cut off the plugs. This takes some skill. Some really nice
exhaust systems for race cars have been done this way, I am pretty
sure this was done by an English craftsman although I don't remember
his name. http://www.flickr.com/photos/sfisher71/4701370903/

Jim Merz
Big Sur CA

[Ray Brandes]

Another method is to fill the tube with one of the low melting alloys. 

Bend away, then immerse in hot water and melt the metal out. 

I have a bunch of it somewhere that melts around 160ºF.

You can get it from Ney Metals

Regards, Ray

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Ray Brandes, Panama City Beach, FL USA

[TIM.N...@comcast.net]

Another way to reinforce the tube is plug it with clay and fill it with water and freeze it. Then form it cold not hot . I did this with stays and ultra thin  unicrown fork blades and it works great.
Tim
www.lighthousecycles.com

Tim Neenan %7C tim.neenan%40comcast.net

---

From: "Ray Brandes" <ray.b...@gmail.com>
To: "Jim Merz" <james...@gmail.com>
Cc: "Framebuilders" <frameb...@googlegroups.com>
Sent: Tuesday, November 1, 2011 12:48:05 PM
Subject: Re: [Frame] Re: bending chainstays

[dave bohm]

Another method I have heard of is using a dish-soap and water mix (heavy on the soap)  Freeze overnight and the soap prevents the frozen concoction from cracking.  

 

Dave Bohm

 

---

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No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1411 / Virus Database: 2092/3989 - Release Date: 11/01/11

[TIM.N...@comcast.net]

Another way to reinforce the tubes is to plug one end with clay and fill it with water and freeze it. You then form it cold not hot. I've done this with stays and ultra thin unicrown fork blades and it worked well.

Tim
www.lighthousecycles.com

Tim Neenan %7C tim.neenan%40comcast.net

---

From: "Jim Merz" <james...@gmail.com>
To: "Framebuilders" <frameb...@googlegroups.com>
Sent: Tuesday, November 1, 2011 10:58:08 AM
Subject: [Frame] Re: bending chainstays

[Ray Brandes]

I like it! Water is very economical! = Ray

[mallard]

Nice one Tim, cheap Cerro !!! ... great trick.

tom mallard
   analyst-SDE | sustainable design
      http://www.mallard-design.com

[Eric Doswell]

Not too heavy on the soap, it shrunk quite a bit until I found the right blend.
E

dave bohm <dave...@cox.net> wrote:

>Another method I have heard of is using a dish-soap and water mix (heavy on
>the soap) Freeze overnight and the soap prevents the frozen concoction from
>cracking.
>
>
>
>Dave Bohm
>
>
>
> _____
>

>From: frameb...@googlegroups.com [mailto:frameb...@googlegroups.com]
>On Behalf Of TIM.N...@comcast.net
>Sent: Tuesday, November 01, 2011 12:55 PM
>To: Ray Brandes
>Cc: Framebuilders; Jim Merz

>Subject: Re: [Frame] Re: bending chainstays
>
>
>
>Another way to reinforce the tube is plug it with clay and fill it with
>water and freeze it. Then form it cold not hot . I did this with stays and
>ultra thin unicrown fork blades and it works great.
>Tim
>www.lighthousecycles.com
>
>Tim Neenan %7C tim.neenan%40comcast.net
>
>
>

> _____

>
>From: "Ray Brandes" <ray.b...@gmail.com>
>To: "Jim Merz" <james...@gmail.com>
>Cc: "Framebuilders" <frameb...@googlegroups.com>

>Sent: Tuesday, November 1, 2011 12:48:05 PM
>Subject: Re: [Frame] Re: bending chainstays
>

>Another method is to fill the tube with one of the low melting alloys.
>
>Bend away, then immerse in hot water and melt the metal out.
>
>I have a bunch of it somewhere that melts around 160ºF.
>

>You can get it from Ney Metals <http://www.neymetals.com/>

>
>Regards, Ray
>
>On Tue, Nov 1, 2011 at 12:58 PM, Jim Merz <james...@gmail.com> wrote:
>

>Sorry for the empty post.
>
>I bent Renyolds chainstays for my first MTB frames back in the day.
>Thicker tubing should be easier, but these were less than 0.040" wall.
>I plugged the small end with brazed on plate and filled the tube with
>dry fine sand. Don't use glass beads. Pack the sand as tight as you
>can then weld or braze a plate on the big end. You then use a torch to
>heat the tube where you want to bend it. Get an even dark red where
>the bend needs to be. The sand helps keep the tube from buckling. Once
>your done cut off the plugs. This takes some skill. Some really nice
>exhaust systems for race cars have been done this way, I am pretty
>sure this was done by an English craftsman although I don't remember
>his name. http://www.flickr.com/photos/sfisher71/4701370903/
>
>Jim Merz
>Big Sur CA
>
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>
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>
>

>--
>Ray Brandes, Panama City Beach, FL USA
>

>--
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> _____

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>No virus found in this message.
>Checked by AVG - www.avg.com
>Version: 10.0.1411 / Virus Database: 2092/3989 - Release Date: 11/01/11
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[dave bohm]

" Not too heavy on the soap, it shrunk quite a bit until I found the right
blend."

Do tell, what is the secret sauce? I have never done it.

Dave B

[Wissahickon Cyclery]

The snow bikes get a 100mm BB shell and the bend required is not that dramatic.  I kind of feel it could be done with a standard bender and no extra efforts required.  I can bend 3/4" -.028" on a 4" radius collar with no extra anything.  I have bent .020" air hardened on a 6" radius collar but never tried on the 4" (mostly because it would end with stuff in the garbage).  All those extra efforts are not usually needed with a good bender that supports the entire tube during the entire process of the bend.  Most stuff under 4" radius collars gets an internal mandrel.

-Drew

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Drew Guldalian
Wissahickon Cyclery
7837 Germantown Ave Phila,PA 19118
www.wiss-cycles.com
www.engincycles.com

[Alex Wetmore]

I agree with you on the normal fat bikes that use 3.7" to 4" tires Drew.  Rory has his sights set high and is looking to use the Surly Big Fat Larry tire (made for the Surly Moonlander) which is 4.7" wide on a 100mm rim, and without very long chainstays.  That makes the bends trickier and leaves a very narrow area to thread the chainstay (and chain) between the crank and tire.

I've been suggesting that shooting for a <4" tire on the rear with a 4.7" on the front might be a good compromise, but Rory likes a good challenge.  It's hard to argue with that, but these bends are outside of my area of knowledge which is why he's asking on the list.

Making these huge tires work has some real challenges, I'm impressed that Q has been able to bring so many fat bikes to the market (Pugsley, Mukluk, and now the Moonlander).

alex

---

From: frameb...@googlegroups.com [frameb...@googlegroups.com] on behalf of Wissahickon Cyclery [wissc...@gmail.com]
Sent: Tuesday, November 01, 2011 2:27 PM
To: dave bohm
Cc: Eric Doswell; TIM.N...@comcast.net; Ray Brandes; Framebuilders; Jim Merz

Subject: Re: [Frame] Re: bending chainstays

[Eric Doswell]

I went really heavy on the soap (Dawn) and pulled my tube out of
the freezer to find the mixture had shrunk considerably. So I thawed it
out and backed off the soap and refroze until I got to about a shot
glass worth of soap in a half(ish) full 20oz water bottle.
I didn't do much specific research or note taking, because I went to
shoving the tube full of old brake cables after that.
E

[M-gineering]

On 1-11-2011 22:54, Alex Wetmore wrote:
> I agree with you on the normal fat bikes that use 3.7" to 4" tires Drew.
> Rory has his sights set high and is looking to use the Surly Big Fat
> Larry tire (made for the Surly Moonlander) which is 4.7" wide on a 100mm
> rim, and without very long chainstays. That makes the bends trickier and
> leaves a very narrow area to thread the chainstay (and chain) between
> the crank and tire.
>
> I've been suggesting that shooting for a <4" tire on the rear with a
> 4.7" on the front might be a good compromise, but Rory likes a good
> challenge. It's hard to argue with that, but these bends are outside of
> my area of knowledge which is why he's asking on the list.
>
> Making these huge tires work has some real challenges, I'm impressed
> that Q has been able to bring so many fat bikes to the market (Pugsley,
> Mukluk, and now the Moonlander).
>
> alex

I like to cheat with a piece of cranked cromoly flatstock instead of a
tube in the most critical area which also saves a bit of width

--
mvg

Marten Gerritsen
Kiel Windeweer
Netherlands

[Peter Meilstrup]

On Tue, Nov 1, 2011 at 2:54 PM, Alex Wetmore <al...@phred.org> wrote:
> That makes the bends trickier and leaves a
> very narrow area to thread the chainstay (and chain) between the crank and
> tire.

I've been wondering if elevated chainstays are going to make a
reappearance on fatbikes for this reason, to get out of the way of the
crank and/or chainring.

Peter

[Alex Wetmore]

In my sketches they haven't helped as much as I had thought they would. You still need to get the chain outside of the tire, and the chain and chainstay occupy about the same area.

Elevated chainstays plus a jack shaft help, but will result in a really wierd, heavy, and complicated bike.

Sent from my Windows Phone

---

From: Peter Meilstrup
Sent: 11/1/2011 3:45 PM
To: Alex Wetmore
Cc: Framebuilders

Subject: Re: [Frame] Re: bending chainstays

[mallard]

Consider if the cs's are lowered instead of elevated so they angle down from the bb a bit then level, then curve up ... this allows room for the tire without fighting the chain ...

 

Just a thought,

tom mallard
   analyst-SDE | sustainable design
      http://www.mallard-design.com

----- Original Message -----

From: "Alex Wetmore" <al...@phred.org>
To: "Peter Meilstrup" <peter.m...@gmail.com>
Cc: "Framebuilders" <frameb...@googlegroups.com>