# Chopped bends on chainstays



## pvd (Jan 4, 2006)

I'm thinking of doing some chainstays with chopped and welded bends. What do you folks think?


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## sirknumskullgt (Apr 10, 2008)

absolutely if I understand you correctly. You mean to cut the tube halfway-ish then bend it and reweld along the cut right? I do that on all my chainstays and anywhere I need to bend the streamline tubing I use. Works great because you save some of the original material and its easier than cutting the tubes at the right angles which is tricky so that they will line up perfect.


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## pvd (Jan 4, 2006)

That's close. I use 30/16 stays and when I bend them, especially the greater bends, they get quite a bit thinner in cross section if they don't buckle or fold.

I was thinking of cutting the tube completely to make the angel. I'm thinking that I will distress the tube a bit much to bend just part of it. Also, I keep a greater cross section if I have a full mitre.

Just looking for horror stories or problems to watch out for especially since these are chainstays.


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## themanmonkey (Nov 1, 2005)

I've seen it done a few ways over the years. The way I liked the best was to basically cut a wedge out of the inside and bent around that. Weld up the seam and it looks really clean and the HAZ is a bit smaller. I've seen folks just cut the angle and do a full butt weld for the new. The prior I've only seen a couple times and have never heard of a problem. The latter I've seen be fine and I've seen broken. I think it's more about the skill of the builder than the limitations of the material.


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## sirknumskullgt (Apr 10, 2008)

yah what the manmonkey said. I like cutting it and bending it to prevent kinking in the tubes. Does look very clean from the outside as well.


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## Walt (Jan 23, 2004)

*I've done it*

Albeit only with with 3/4x1.5"x.049 box-section 4130. I was building a mountain bike frame for a fellow who is 400 pounds, and I couldn't conceive of any of the chainstays on the market being strong enough.

I cut at about 8 degrees, flipped, and butt welded back together. Then I installed a crossbrace on the finished stays that was welded in on both sides of the butt weld to help reinforce things.

So far (touch wood) it's been 3 years and I haven't heard of any problems.

For a more normal chainstay, I like the monkeyman's idea. Never done it, though.

-Walt


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## swift (Apr 3, 2007)

I'll preface this by saying I've not tried it...but here's an idea, albeit a heavier option.

Sleeve the stay before the bend. Either tack it or pin it to the stay in an area that will cover apex of your bend. Complete the bend and then finish brazing sleeve in place.

I'd probably do all kind of crazy/fancy/unnecessary work on the sleeve trying to express an artisan's approach but certainly not necessary.

Again, I've not ever done this. ...Just an idea. YMMV.


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## brant (Jan 6, 2004)

pvd said:


> I'm thinking of doing some chainstays with chopped and welded bends. What do you folks think?


I think it's a great idea - though my builders (mass production factories) never wanted to do it.

Hence the "on-one wishbone" has mitred junctions, rather than cut and welded corners.

You could mitre and cap off one tube end... That could look neat. More weld area.

Ever tried anything with bits of plate in the chainstay area? - I've been working on that this afternoon after I heard Lynskey had a new water-jet cutter guy, and I wanted some more tyre clearance on our Ti frames...


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## shiggy (Dec 19, 1998)

[email protected] said:


> ...Ever tried anything with bits of plate in the chainstay area? - I've been working on that this afternoon after I heard Lynskey had a new water-jet cutter guy, and I wanted some more tyre clearance on our Ti frames...


I have


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## Peter E (Feb 16, 2004)

Titus used to do it on their Ti hardtail, the HCR.

Here´s how I did it. Not that god with the TIG so I braze. lathed end plugs with solid ends. braced them to the tubes, cut to the right angle and braced everything together. Looks good but have not tried it yet. Hope it works


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## pvd (Jan 4, 2006)

I did a test stay. I was concerned about the strength. I almost went over to a strut. I spent about 20 minutes staring at the stay. Then I gave it hell. I beat the **** out of it. Hammer, vise, bending...

It's funny. The welded seam was the strongest part of the structure.

I'm going for it. Pics later.


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## rocwandrer (Oct 19, 2008)

Depending on how sharp the bend is, you may need a web gusset spanning the inside of the tube. This gusset would look a little like what Peter did, think of this gusset as something that would block the flow of water inside the tube, and get welded at the same time as the joint between the two pieces of tube and you get what I mean. The reason for the gusset is to prevent the new flexure mode you created from killing the tube in fatigue. 

When i have done this in the past, I've done extreme angles with one tube intesecting another capped tube's sidewall. For less extreme angles, I take a wedge out of the tube about 3/4 of the way through a round tube (far enough so bending it closed doesn't produce ears), or all the way to the opposite wall on rectangular tubing. I then close the wedge and braze or weld the seam, grind it slightly (don't do this unless you do the next step too...), and braze on a patch over the seam that is either bent flat stock (rectangular tube), or cut from a curved (thicker wall, slightly larger diameter) round tube. In the case of the round tube, I've used pieces cut from the tops of the end cuts off unicrown fork blade tops, heat bent thicker tubes, etc. I wish I could find a picture....

edit: with welding, depending on the filler strength, no post weld grinding and no patch gusset might be ok. with brazing, the bronze isn't strong enough to prevent the joint from tearing out without a lot of build, so the gusset looks better and gives better clearance. That same issue is my only worry with Peter's joint pictured above. If that tube is a seatstay, it might be fine....


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## Peter E (Feb 16, 2004)

rocwandrer said:


> edit: with welding, depending on the filler strength, no post weld grinding and no patch gusset might be ok. with brazing, the bronze isn't strong enough to prevent the joint from tearing out without a lot of build, so the gusset looks better and gives better clearance. That same issue is my only worry with Peter's joint pictured above. If that tube is a seatstay, it might be fine....


that's the left chainstay, 3/4"-0.035.

The brazed area is 5 times greater than the cross section area of the 3/4tube. I'm a little concerned too. I'll let you know if it breaks...


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## pvd (Jan 4, 2006)

capping one of the stays would have been a good idea. I should have thought of that. I'll do that on the next bike.

The stays turned out nice. I'll post some pics later.

I'm going home now. Happy new year.


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## rocwandrer (Oct 19, 2008)

Peter E said:


> that's the left chainstay, 3/4"-0.035.
> 
> The brazed area is 5 times greater than the cross section area of the 3/4tube. I'm a little concerned too. I'll let you know if it breaks...


the issue is if it subjected to bending stresses, and how those might be distributed by your plug, as it sounds like you already know... road or mtb use?


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## Peter E (Feb 16, 2004)

mtb


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## pvd (Jan 4, 2006)

Here's what I got done on that stay.

Clearance for 2.35"+ with 16.75 stays.










Test peice. Same as the final version, but beat up, smashed and bent.


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## brant (Jan 6, 2004)

pvd said:


> Test peice. Same as the final version, but beat up, smashed and bent.


wonder how it would be in fatigue loading though? Driveside stays get screwed by fatigue in my experience - we stopped using chainstay bridges and switched to gussets on the outside as a common failure mode of our earlier frames was a fatigue propagating around the stay from the chainstay bridge weld.


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## pvd (Jan 4, 2006)

Fatigue is definately the real issue. I can only try and see how it works. I figure that if something survives the beat down test, it's worth a run or two down the hill.

My impression while pounding the stay was that the weld actually improved the structure of the tube. With bending the tube gets very thin cross sectionally. With this segmentation, it stays wider. The weld acts almost like a support beam around the tube as well. It didn't want to crush there. Putting an 0.035 cap between the tubes would be stronger, but i'm wondering now if that is needed. We will see. It would be a good time to have a cycleing test rig in a HALT chamber right now.

Strutting the bend with a capped segment would be the strongest, but adds a huge amount of work and changes the astetic.


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## pvd (Jan 4, 2006)

Here's a map of the clearances for those bends. Note that this will give 75mm of clearance at 330mm from the axle, aproximately the widest part of the tire.


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## coconinocycles (Sep 23, 2006)

uuuummmm.......i can fit a 2.35's with c-stays @ 16.75" onto a 73mm shell with room no sweat.......the deda 0/3's.........just sayin', steve.


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## perttime (Aug 26, 2005)

Some bikes in the tougher end of the spectrum seem to go for a plate in that area. Evil Sovereign was one and here's another:
http://2soulscycles.blogspot.com/2007/07/white-gloss.html


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## Peter E (Feb 16, 2004)

I went with a plate. think PVD´s chainstay will be stronger though


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## pvd (Jan 4, 2006)

I love the way that plate turns into the ICGS mount on the 2Souls bike. That is a very elegant solution.

https://2.bp.blogspot.com/_UL0C8nFqg8E/Ro4QFyJCOuI/AAAAAAAAAC4/rDnCFnY1RU4/s1600-h/P7030016.JPG


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## scooter916 (Jan 2, 2006)

pvd said:


> I love the way that plate turns into the ICGS mount on the 2Souls bike. That is a very elegant solution.
> 
> https://2.bp.blogspot.com/_UL0C8nFqg8E/Ro4QFyJCOuI/AAAAAAAAAC4/rDnCFnY1RU4/s1600-h/P7030016.JPG


That is pretty *****in, now all it needs is a hammerschmidt


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## RogerDoger (Sep 20, 2008)

So how goes it?


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## Schmitty (Sep 7, 2008)

coconinocycles said:


> uuuummmm.......i can fit a 2.35's with c-stays @ 16.75" onto a 73mm shell with room no sweat.......the deda 0/3's.........just sayin', steve.


+1

73 shell, triple rings, .75 stays with a simple bend, plenty of room at 425mm for a 2.35.

My guess would be any kind of interupted stay on the drive side will not pass the test of time.

-Schmitty-


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## BeatAFool (Jan 14, 2008)

I was wondering the samething. 

I'm just finishing up a frame with chopped/bent stays. I'll put my fatass on it next weekend and see how long it last.


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## rocwandrer (Oct 19, 2008)

BeatAFool said:


> I was wondering the samething.
> 
> I'm just finishing up a frame with chopped/bent stays. I'll put my fatass on it next weekend and see how long it last.


Same here.

I can say that my particular chopped and bent stays look rather a lot more like an industrial accident than an intentionally made part, at least from an aesthetic viewpoint. But they appear to clear the 110mm tire, crank/rings, and my heel with plenty of room, so I'm not terribly unhappy.


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## Smokebikes (Feb 2, 2008)

Here's our spin on a solution for fat tire clearance for a 29'r........definately not as elegant as some but does the job nicely......so far. :thumbsup:


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## BeatAFool (Jan 14, 2008)

I'll try and post some pix of my cs's. They look pretty good so far but I still think they're gonna break with my fatass pushing it.


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## brant (Jan 6, 2004)

Lynskey just finished my frame with my new plate chainstay on the driveside.


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## DWF (Jan 12, 2004)

brant said:


> Lynskey just finished my frame with my new plate chainstay on the driveside.


Serious question: Instead of doing all that, why not just have a simple plate cut out for both sides like you would a soft tail? Doesn't need to be thick, attachment is simplified, symmetry is good, etc., etc.


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## brant (Jan 6, 2004)

DWF said:


> Serious question: Instead of doing all that, why not just have a simple plate cut out for both sides like you would a soft tail? Doesn't need to be thick, attachment is simplified, symmetry is good, etc., etc.


"All that" isn't "all that" really. It's just a plate with two cuts and a two bends. It's not hard.

The only soft tail I've done had tubular chainstays.


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## DWF (Jan 12, 2004)

brant said:


> "All that" isn't "all that" really. It's just a plate with two cuts and a two bends. It's not hard.
> 
> The only soft tail I've done had tubular chainstays.


Simple thin plate across the length of the BB shell; no secondary ops. Round equal length stays, ends square cut for bullets/domes. Easy to manufacture and assemble and is very adjustable for a bunch of different apps.

Just throwing it out there.


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## perttime (Aug 26, 2005)

What is the practical purpose of the cuts?
They look cool. I bet the North of England mud thinks so too...


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## brant (Jan 6, 2004)

DWF said:


> Simple thin plate across the length of the BB shell; no secondary ops. Round equal length stays, ends square cut for bullets/domes. Easy to manufacture and assemble and is very adjustable for a bunch of different apps.
> 
> Just throwing it out there.


I don't think there's enough material in there to do what I wanted to do (chainring clearance and big tyres).


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## brant (Jan 6, 2004)

perttime said:


> What is the practical purpose of the cuts?
> They look cool. I bet the North of England mud thinks so too...


It's to triangulate the plate part across the BB shell without having to weld in another tube.


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## perttime (Aug 26, 2005)

mmm,
which is harder:
- making the cuts and bending as needed
- bending as needed and adding a triangular plate/gusset?


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## brant (Jan 6, 2004)

perttime said:


> mmm,
> which is harder:
> - making the cuts and bending as needed
> - bending as needed and adding a triangular plate/gusset?


I haven't done it the way I have for shits and giggles. I did it to retain the integrity of the material, give good mud clearance, allow ease of manufacture (water jet cut plate, press tool then does the bending required).

I presume when you say a "triangular plate/gusset" you're talking about replacing the middle "tang" of my design with a triangle? Then I worry you'd have a "shelf" for mud to sit on.


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## perttime (Aug 26, 2005)

brant said:


> I haven't done it the way I have for shits and giggles. ...
> 
> I presume when you say a "triangular plate/gusset" you're talking about replacing the middle "tang" of my design with a triangle? Then I worry you'd have a "shelf" for mud to sit on.


I know, and that is what I was talking about.

I have no claim to fame in bike design: just an armchair engineer looking at a new mousetrap, wondering if it kills mice better or not.

edit:
Nice dropouts and disc mount:


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## MichauxYeti (Nov 10, 2005)

Brant, what kind of housing/hose guides are you using that thread into the bottle bosses?


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## brant (Jan 6, 2004)

MichauxYeti said:


> Brant, what kind of housing/hose guides are you using that thread into the bottle bosses?


At the moment I'm going to use P-Clips, though there seems to be some controversy over that on a $$$$ ti frame.

I am off to Taiwan on Sunday and will hunt down alternatives.


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## shiggy (Dec 19, 1998)

brant said:


> At the moment I'm going to use P-Clips, though there seems to be some controversy over that on a $$$$ ti frame.
> 
> I am off to Taiwan on Sunday and will hunt down alternatives.


Where did you get that idea?


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## Thylacine (Feb 29, 2004)

Brant, get some mega thin stainless hose guides laser cut and bent up. P-Clips are rather low-rent, not to mention you can't mount three cables.


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## brant (Jan 6, 2004)

Thylacine said:


> Brant, get some mega thin stainless hose guides laser cut and bent up. P-Clips are rather low-rent, not to mention you can't mount three cables.


Just found some lovely CBC alloy ones on the vertech stand at the taiwan bike show.


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## Thylacine (Feb 29, 2004)

Pix pix pix


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## vulture (Jan 13, 2004)

Thylacine said:


> Brant, get some mega thin stainless hose guides laser cut and bent up. P-Clips are rather low-rent, not to mention you can't mount three cables.


Zip ties are really top shelf, 1/2 inch p clips will hold three cables together. I like the stainless Idea, I made a couple by hand just haven't persued mass prod yet.


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## DWF (Jan 12, 2004)

vulture said:


> I like the stainless Idea, I made a couple by hand just haven't persued mass prod yet.


They're available commercially. I had a supply of them some years ago and they work really well.


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## brant (Jan 6, 2004)

Thylacine said:


> Pix pix pix


On my flickr page - http://www.flickr.com/photos/shedfire

ps: Alex showed (slightly) an alloy 36in rim.


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## Thylacine (Feb 29, 2004)

Nah, I mean stainless 'clips' that attach to bidon bosses as per Brants requirements.

I costed some up but as usual here they cost a bomb. Hard to justify spending 500 bucks just to make some wafer thin stainless bits. That online machine shop place (can't recall the name......emachine or something?) might be the place for something like that.

Or then again I could just get something better from Taiwan.


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## DWF (Jan 12, 2004)

Thylacine said:


> Nah, I mean stainless 'clips' that attach to bidon bosses as per Brants requirements.
> 
> I costed some up but as usual here they cost a bomb. Hard to justify spending 500 bucks just to make some wafer thin stainless bits. That online machine shop place (can't recall the name......emachine or something?) might be the place for something like that.
> 
> Or then again I could just get something better from Taiwan.


Sounds like it's time for a pro/con evaluation. What's the pro of having bottle bosses drilled around the bike? I can think of a few cons. If you want a clean look on a SS/Gearie, why not just route the F/RD cables on the DT? When you run it SS, you can't see them. You're always going to have brake cables/housing so that's a non starter....I assume you're always going to have brakes....


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## Thylacine (Feb 29, 2004)

I've done a couple of bikes where there are hydro guides for the disc - as you rightly point out, you'll always run brakes - but on the underside of the top tube had three bidon bosses for the option of going geared.

On the drive side seatstay, I added a third hourglass rack mount to the middle of the stay (not shown) for mounting the rear derailleur cable. The rack mounts double as cable guides.

It's pretty clean i guess.


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