I do love how he uses the grinder to notch the tubes. Feel like as a beginner it’s easy to get wrapped up in making everything perfect, when it’s probably not actually needed.
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Hei i’m thinking about bending my seatstays up to 60 ore 70 degrees. on the larger side. so the od is like 16 ore 14mm. have ever try someone a bend like this? is it possible to get a clean wall and a stable tube after? It should be in a very small radius. i don’t know like 30mm?
thanks for your ideas!
Welcome @Janosch
Are you bending 14mm or 16mm for seat stays? The discussion about this thread is for racks, which are much easier to bend. Tubes that are .5in (12.7mm) and larger diameters will need more complicated bending setups to avoid the tubes rippling and deforming see this thread for some examples.
30mm center line radius (CLR) is very difficult to achieve. Typically people will only bend down to 3in (76mm) CLR
The best tube bender for stays is the cobra bender: TOOB Bender | Cobra Framebuilding
If you are located in USA, Andrew at @BikeFabSupply may be willing to bend SS’s to your spec: BENT SEAT TUBES — BICYCLE FABRICATION SUPPLY
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Paragon sells 3/8" tube blocks so i use one or two of those and an angle finder to keep it all phased while holding the bender in the vise. For 1/2" i have a Rigid with a 1.5" CLR i believe and for 3/8 and 5/16" it’s the same tight radius bend that most seem to use and has many copies/manufacturers. I’ve also used a wood v-groove fork blade bender for longer curves, a 700c wheel with a c-clamp to hold the tube for even longer radius bends. The best bender for this would be a Diacro but I’ve also heard of builders finding ratchet benders on eBay, can’t remember the names of those though. The ratchet is nice for counting clicks to keep the bends the same.
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Skimmed this thread so not sure if discussed, but ive got a 10 mm pipe bender, tried bending some 10 x 0.8mm 4130 and it just kinked the tubing, any idea why? Just because the bender is low quality or am I doing something wrong?
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Thanks so much for your super fast answer! There are a lot of useful informations for me.
I’m located in germany so it’s difficult for me to get the toon bender from cobra. Also a bit to expensive for a beginner like me…
Maybe I can get some cnc machined parts like top eyes🤔 but may they will be to heavy
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There can be a few factors at play that cause kinking:
- Is the clamp holding the non-bent material slipping?
- Is the radius too tight?
- Did you apply even pressure through the bend?
- Is the follow block well aligned?
- Is there a discontinuity in the material?
Have you had success bending 10x0.8mm on that bender before or is this your first time trying it out?
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Was my first try, ill try again and look if i can spot some ofthe things you listed
I tried again with a bender for 13 mm instead of the “right” One and although it was just slightly deformed it worked much better than the 10mm one.
Hi… Anyone used a .8mm or 5/16 with a0.6mm wall thickness to make racks? Stainless 316… Im wondering if is too thin…
Thanks!
Lucas
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I have used similar 4130 in 5/16 and 0.035 walled. I don’t think I ever found 0.028" walled tubing.
You’ll find the .8mm is great for a nice light weight rack. For heavy duty touring, I would probably go with .049 walled in 4130. I have talked with a few folks and generally there seems to be some mistrust of the various stainless tubes, though I’m sure with thick enough walls, they would be fine too. You’ll have to use silver to braze them though which is more tricky.
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I made a rear pannier rack for my wife with .028" (0.7 mm) wall 5/16" (8 mm) tubing. Weighs under 6 ounces and has been tested to over 200 lb static load (i.e. I sat on it!)
The seatstay attachment is one-sided for two reasons: (1) her sidepull brake would get in the way on the other side, and (2) one side gives enough strength and another strut would add weight!
That reminds me, if you want max strength-to-weight ratio, avoid curves in the load path from the cargo to the ground. Curves in the plane of the top platform are fine, but avoid curves in the legs that go down to the dropouts or wherever your attachment is. Those downward struts are loaded in compression — think “column”. Columns support much more weight if they’re straight. Any curve at all takes quite a bit of their strength away.
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Thanks @bulgie and @Duanedr I found this pipes RVS pipes, that are for maybe gas or liquid made of 316L 0,6mm wall thickness.
Im skeptic about it… my only experience with 316L is with 3dprinting and seems a bit soft… at least compared with 17/4… so i dont know if is a good option…
In Europe i can get from aircraft spruce a good 4130 1/4x0.028… but it becomes a quite expensive… (not that i don’t like… they are amazing tubes and they weld really nice!) and can find RVS in 1mm (but i find ít could be thinner…)
I want to use 6 and or 8mm (1/4 or 5/16)… and used both 0.028 and 0.035. I like the idea of stainless for not painting/powder… and this pipes seem a good option to make some paint free and extremely light racks… And much cheaper than the 4130 from aircraft…
Any suggestions?? Do you recon these pipes above are ok? Also, anyone knows places for this kind of tubes in Europe??
This is the aircraft rack:
This is the RVS one:
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Fun custom rack video featuring Fitz Cycles
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I’ve built tons of 5/16" x 0.028 racks out of 4130. I’m bummed that this material is hard/impossible to find now.
I think 8mm x 0.6mm would be fine, especially if that is mostly on the platform and you use something a little more robust for the legs. I’m less convinced on stainless, I’ve just found it to be annoying to build racks with and it’s not as strong.
My lightest rack is a handlebar bag rack that is made of 1/4" x 0.028 and mounted to centerpull bosses and studs lower on the fork legs. It is 137 grams. The bag fits using Ortlieb pannier hooks that clip around the forward bar (instead of using a heavier decaleur). The only problem that I’ve ever had with this rack is that it is so close to the headtube that tall bags don’t fit under the handlebars. Most handlebar bag racks are a lot farther away from the headtube.
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Obviously, it depends on the load you’re carrying and other things. I have made racks from stainless and haven’t had problems. I think one was 316 and it felt too easy to bend so I switched materials after making the outer rim of the platform. I went to heavier walled 306 if I remember correctly.
Like Alex, I prefer 4130. I would reach out to Peter at Ceeway (framebuilding.com) and see if he can point you to a tubing supplier in Europe. He’s in UK but probably knows what other builders are doing on the continent.
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Humble lurker, not a rack maker. Just wanted to chime in with an interesting thought. Has anyone considered manufacturing rack-specific tubing from a bike tubing manufacturer?
- Collectively, we can probably eat through the minimum order quantity of the tubing quickly
- during the tube forming process the 4130 tube work hardens, so the tube might be stronger than the 4130 you can buy (need to confirm this)
- We would have control over our own supply
Is this desirable since most rack tubes will be bent?
I know of some folks who have bought tubing straight from the mill and that seems ideal for mass production. It does seem like the big framebuilding suppliers (BFS, FBS, M-G, etc) could stock more straight-gauge 4130 but maybe the margins on that aren’t good enough to make it worthwhile.
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Nice, I like simple racks. They are usually more elegant.
I’m a little surprised about the lack of backstop/tombstone. Is it for something other than a handlebar bag?