Rene Herse Chainstays: 1.0mm, 0.8mm, 0.7mm Wall, re: Planing

[John Clay]

My recollection is that the BQ consensus on performance (as in best propulsion performance) is that laterally stiffer rear ends (thicker wall stays) are superior.

Is that still the belief?

If so, then what is the rationale for the thinner wall stays, aside from weight?

Why isn't there a 0.9mm stay?

What wall thickness stays are y'all using?

If stiffer is better then I'd expect 1.0 and 0.9 availability....and then a 0.7 for those who are trying to shave of the maximum amount of weight.

Or am I behind the times??

Thanks,

John Clay

On the Cody Scarp

Tallahassee, Florida

[Michael Wong]

You probably know that tubing diameter makes much more difference for stiffness than thickness. For example, a 16x0.7 stay will be stiffer than a 12x0.9.

I'm pretty sure the BQ theory of planing is to have stiffer chainstays and flexible seatstays. I don't think Jan Heine has made a specific statement on lateral vs vertical stiffness, but in his test of the Open Min.D, he said it was the one of best planing bike he's ridden. The Open is designed to be more stiff laterally than vertically, though it may not be that stiff laterally either. I rode a Min.D and found it to be very responsive at the pedal.

I have an Elephant National Forest Explorer. Upon examination, I thought it would quite flexible, but I found the ride to be suprisingly stiff, which I mostly attribute to the chainstays. 

I'm not sure one can actually measure planing, but I think of it as benefitting seated efforts. I find the NFE,whose seatstay design looks like it would be very flexible, does pretty well climbing while seated.

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[John Clay]

Thanks Michael.

Yes, I'm aware of the effects of diameter vs wall.

This question is limited to conventional steel frames with straight seat stays and a given CS geometry, in this case 22.2 ROR stays; it could be other profiles but I use and RH offers 22.2 ROR; assume no vertical compliance.

Is anybody else up on the current thoughts framing this subject? I let my BQ subscription lapse a couple of years ago simply to reduce accumulation of stuff and so may have missed recent developments/theories/data.

Anybody? I distinctly remember that stiffer (and that means laterally) was felt to be better for propulsion/planing.

Has that notion evolved differently? Presumably, and I seem to remember this too, the 1mm wall stays were offered to provide best planing performance. If that is so, if stiffer is still thought to be preferable, then why the 0.8 and 0.7 wall stays? And if some variability is desired I'd think that a 0.9 would be offered.

I am puzzled.

Thanks for any insight,

John

[rthrst...@gmail.com]

John, I don't know what the garage scientists are saying (but am interested!), but have been conducting a personal experiment along these lines. I am 6'6"/200 lbs, and find that some old all 531 frames are simply a bit too flexible for me and my riding style, at the sizes I ride: for example, a Motobecane Le Champion (62 cc st ; 60 top tube ), or a Gitane Tour de France (same size). So I bought an old Trek 414, with slightly stiffer Ishiwata 022 front triangle (9-6-9), and hi-ten stays. (Ishiwata 0265) -- it accelerates much better than the Reynolds frames. So I then found a Trek 530: all Ishiwata 022. Nice-riding frame -- but doesn't accelerate *for me* like the 414 does. It seems to be the chainstays/seatstays.

Ishiwata 022 stays are listed here: http://www.equusbicycle.com/bike/ishiwata/catalog2/pdf/Ishiwata%20Catalog%202%20opt%203.pdf

Chainstays are 22.2/12 ... .8 thickness.

Ishiwata 0265 stays are 22.2/12 1.0 thickness. Seatstays are similar.

I also found this comment, for what it's worth: https://www.bikeforums.net/classic-vintage/1062772-stiffness-vintage-steel-vs-modern-frame-designs.html: 

“FWIW, the high end Bianchis used to use SP in the downtubes and chainstays, and Columbus SL in the rest of the frame. This made them pretty zippy. Lawee/Univega and I believe Miyata did the same in their bikes throughout the line up."

So someone, somewhere is having a similar experience. I agree that .9 and 1.0 chainstays would make sense. Columbus SP are 1.0. For someone like me, perhaps more flexible seatstays (.8) and stiffer chainstays like the Columbus SP ones would make sense?

I just looked at the Kasei tubsets Rene Herse sells (never looked before): does look like one can select 1.0 chainstays....but no .9, which might be ideal for some riders.

AS

[hans jatzke]

Hey John,

I'm glad you are bringing this up because I was thinking on this for a new frame I wanna put together. I'm no expert on this but I know that the length of a tube + walls thickness + diameter of a tube all influence the tubes stiffness. So when thinking about what wall thickness to use for chainstays I was gonna choose the thinnest wall for the shortest chainstay lengths and then thicker walls for longer chainstays. I've never designed for disc brakes but could see that you might need a thicker wall to account for the added stress they act upon the chainstays.

Best,

Hans Jatzke

Hobby-ist Framebuilder

Philmont, NY

[fordb...@gmail.com]

Not to hijack a thread- but Hans- do you have a local supplier of welding tanks and supplies ? I live near Philmont and want to find a supplier. I'd rather not go all the way to Menands...

Also- I'm glad there's a hobbyist frame builder nearby...

Ford in Ghent, NY

[John Clay]

Some of you might be interested in the spreadsheet I developed for comparison of main tube flexibilities; the latest version is linked in my December 31, 2020 post, here:  https://groups.google.com/g/framebuilders/c/QaOg8c-17eE

John

[Michael Wong]

Thanks John! I did one of those too. It was tricky for tubing like Genius, with asym butts.

I may not have understood your original question. My understanding is JH has selected the thinnest wall and therefore flexiest tubing for his seatstays because he believes that is what planes best. So the RH Kaisei seat stays are only .6. It is an interesting question why he offers only 1 seat stay thickness but three different chainstay difference.

I only mentioned the carbon bike as I understand some carbon bikes today are starting to adhere to some of JH's tenets and the design is much more visible than with a steel bike.

The wider bike industry still seems allergic to lateral flex. 

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[Hahn Rossman]

John-

CS stiffness (or lack of) has a couple variables. Wall thickness, dents/bends, and length. Since the tube is relatively slender for its length, the length matters a lot. The wall thickness works out to varying almost directly in proportion to thickness (10% thicker= 10% stiffer). The length on the other hand is more like 5% shorter is 15% stiffer @ length=400mm. 

It should be noted that the CS is not entirely loaded in isolation and is part of the rear triangle (which is a pretty great 3D structure).

So why the different thicknesses? I don't think there is a specific rationale from Kaisei, but it's what they have tooling for and feel like provides a selection for builders to tune the ride of the bikes.

Try making a bike with shorter stays than you have in the past (which brings it's own headaches) or maybe much longer and see what you think about the differences.

Hahn Rossman

 

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[John Clay]

Just saw this Hahn; thanks for the reply.

I grok all of that, but my question is different and of course assumes all else equal; it really boils down to whether or not BQ & Co have revised their thoughts re rear end flexibility. Not too long ago BQ opined that stiffer rear ends were beneficial to propulsion (hence thicker wall CS); more recently BQ has made statements contrary to that.

What has changed in BQ's thinking?

Implicit is that all else is identical, rider, frame particulars, etc.

Thanks,

John

[Michael Wong]

As I understand it, sometime before 2008, JH was test riding with Mark Simmons for a review, one on a stiffer bike and one on a flexy bike. They were either testing a Ti bike or a Jeff Lyon. On that day, one of them was always faster on the flexy bike.

In 2008, they did a double blind test with four bikes of varying stiffness. I believe our own Alex Wetmore participated. I believe BQ interpreted the results of that testing to indicate that the flexier frame was the most efficient. It "planed" the best. JH and Mark were surprised as before that they had always assumed stiffer was better.

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