Kirk Frameworks

[David Kirk]

Originally Posted by Gwerziou

This is a gorgeous piece of work. I’m curious about stainless steel frames - in general but more specifically, I have mostly seen them fillet brazed and/or lugged, but only occasionally TIG welded. Is there an advantage to a certain method with this material? I see on the custom bikes channel a Stelbel Inox model that appears to be TIG welded (looks nice!), but I have read that TIG welding stainless is extremely difficult. Is that so?

I don't do any welding of stainless myself so I can't speak from direct experience. My f-building friends who TIG stainless say that it's a bit like welding Ti in that it needs to be super clean and have a freshly exposed surface for it to weld well. So in that way it's like brazing - sand it, clean it, flux it, and braze it in a super short period of time. Take a break for a phone call or lunch in the middle of it and it can all go to poo in short order.

I braze the tubes together because the temperatures needed to do it are so much lower than welding that it doesn't result in a Heat Affected Zone (The HAZ one hears about with welding) that weakens the tube. This allows for me to use thinner tubes than most would use when welding them and to have zero concerns about the tube failing because the tube got so very hot.

When silver brazing stainless (lugged or fillet) the joint gets up to about 1200°F which is far below then temp where the molecular structure of the tube changes. Tig welding on the other hand gets the stainless up to it's melting point (about 3600°F) and this is far above the temp needed to change the structure of the tube. So with long term use a welded bike is more likely to have the tube fail in its HAZ than a brazed bike that doesn't have a HAZ.

Stainless is a fussy material to work with and it has some odd quirks. It's spendy and takes a lot of practice to get the processes down so that one can make a profit building with the material. And even when you are good at it it take more time to properly hook to pieces of stainless together than it does steel. I guess this is one of the main reasons there are so few stainless bikes being built. But I love the stuff....strong and light and stiff and it has that same magic carpet ride that steel does. It's worth it to me.

dave

[OtayBW]

Originally Posted by David Kirk

...Stainless is a fussy material to work with and it has some odd quirks. It's spendy and takes a lot of practice to get the processes down so that one can make a profit building with the material. And even when you are good at it it take more time to properly hook to pieces of stainless together than it does steel. I guess this is one of the main reasons there are so few stainless bikes being built. But I love the stuff....strong and light and stiff and it has that same magic carpet ride that steel does. It's worth it to me.

dave

Interesting, Dave. Aside from the fabrication quirks, are there any benefits over steel in terms of performance or does steel=SS for the most part? I ask this as an owner of both a SS and steel, but differences in geometry and build make it hard to distinguish pure material characteristics from one bike to another. Thanks and keep up that great work!

[David Kirk]

Originally Posted by OtayBW

Interesting, Dave. Aside from the fabrication quirks, are there any benefits over steel in terms of performance or does steel=SS for the most part? I ask this as an owner of both a SS and steel, but differences in geometry and build make it hard to distinguish pure material characteristics from one bike to another. Thanks and keep up that great work!

If one were to build a stainless frame and a steel frame with tubes of the same diameter and wall thicknesses then the weight and ride will be the same.

However...(you knew this was coming)...stainless tubes like Reynolds 953 are thinner than any steel tube one can buy. The 953 material is bizarrely strong so the tubes can be made thinner and lighter while still being stronger. It's cool stuff.

So if one were to build two framesets - one fully stainless and one fully steel the stainless build will be lighter and and have a slightly smoother ride. And once you factor in the weight of paint on a steel frame going unpainted stainless is a win-win.

Does that make sense?

dave

[lavi]

Originally Posted by David Kirk

So if one were to build two framesets - one fully stainless and one fully steel the stainless build will be lighter and and have a slightly smoother ride. And once you factor in the weight of paint on a steel frame going unpainted stainless is a win-win.

Does that make sense?

dave

Thank you for these answers. I am certainly NOT a weight weenie. However, just curious, in ballpark terms, what might be the weight difference be between these two frames?

I know someday I'll be in the queue for a custom-to-me frame...and this is the question I have: Do I want steel or SS? I like your painted frames very much. I also dig the look (and utility) of the raw SS. Having the SS frame with it's smoother ride would be cool.

[OtayBW]

Originally Posted by David Kirk

If one were to build a stainless frame and a steel frame with tubes of the same diameter and wall thicknesses then the weight and ride will be the same.

However...(you knew this was coming)...stainless tubes like Reynolds 953 are thinner than any steel tube one can buy. The 953 material is bizarrely strong so the tubes can be made thinner and lighter while still being stronger. It's cool stuff.

So if one were to build two framesets - one fully stainless and one fully steel the stainless build will be lighter and and have a slightly smoother ride. And once you factor in the weight of paint on a steel frame going unpainted stainless is a win-win.

Does that make sense?

dave

Fair point, and yes - it makes sense.
My SS is a Columbus XCr and my other steel is an EL-OS on a high-trail (DeRosa), so for me, the the fact that one is SS and the other is steel is lost in too many other variables. Thanks!

[David Kirk]

Originally Posted by lavi

Thank you for these answers. I am certainly NOT a weight weenie. However, just curious, in ballpark terms, what might be the weight difference be between these two frames?

I know someday I'll be in the queue for a custom-to-me frame...and this is the question I have: Do I want steel or SS? I like your painted frames very much. I also dig the look (and utility) of the raw SS. Having the SS frame with it's smoother ride would be cool.

Thanks for the questions -

- in VERY rough ballpark terms an unpainted stainless frame would be about 1/2 lb lighter than a painted steel frame. Not a huge amount but it's something.

- how to choose material? Well, like anything it depends I guess. It depends on your height and weight and how you ride. It matters where you live (raw stainless doesn't like living right near the ocean and salt air) and it matters what look you are hoping for. This is something we would figure out together during the design process. It's very individual and personal.

Does that add up?

dave

[lavi]

^^^

Yup. Gracias. It adds up to N=1.

I know, heresy.

[NHAero]

Originally Posted by David Kirk

Snip
It matters where you live (raw stainless doesn't like living right near the ocean and salt air) and it matters what look you are hoping for.
dave

I found this out with my Anderson here on Martha's Vineyard. Lugged, and slight rust spots on the main tubes just adjacent to the lugs - I think because of the tubes being heated at the lugs, but that's just a hypothesis. I sent it back to Dave Anderson who painted the main triangle.

I think that stainless brings out the highest craftspersonship of our most skilled frame builders. Looking at that Anderson frame always made me marvel.

[carlucci1106]

Originally Posted by lavi

^^^

Yup. Gracias. It adds up to N=1.

I know, heresy.

Yup, that's pretty much it. I look at my CSi, and think how the beauty of the design is timeless, how David probably was involved in its execution. I feel these techniques have been honed through his own exploration, hereafter- and now he has continued by honoring these principles with a modern look at the bicycle. I can only imagine how a Kirk made for me would ride, and how proud I would be to own.

I don't think you could go wrong if you choose either material, given that you let David guide you through the decision-making. I trust he wants the very best bike for you. Someday, Dave.

[robt57]

Originally Posted by lavi

^^^

Yup. Gracias. It adds up to N=1.

I know, heresy.

Where N=∞?

[carlucci1106]

Originally Posted by robt57

Where N=∞?

Lol. I just caught that error in the equation. Should be N=n+1

For me, going to infinity would require larger accomodations. It would make more sense to sell 2 or 3 other bikes and make room/fund the Kirk. Unfortunately, neither of those two scenarios are presently viable.

[David Kirk]

I just wrapped up this build and it will go into a box this afternoon and then head off to South Korea.

It's a straight up road build for short reach brakes and 30 mm tires. Should be a fun ride and it will arrive just in time for prime riding season there.

On to the next build..........

dave

[AngryScientist]

Nice one Dave. I'm sure the new owner's pulse rate went up a few ticks seeing these pics and hearing it's shipping. Ahh, the anticipation!

I wonder if a place like Korea is having as hard of a time (maybe harder) as we are getting parts. I hope he or she is prepared to build build build!

[madsciencenow]

Originally Posted by AngryScientist

Nice one Dave. I'm sure the new owner's pulse rate went up a few ticks seeing these pics and hearing it's shipping. Ahh, the anticipation!

I wonder if a place like Korea is having as hard of a time (maybe harder) as we are getting parts. I hope he or she is prepared to build build build!

That’s a good question and I’m wondering the same on parts there? I think there’s a PL member with a frame similar to this who prolly knows the answer. It would sure suck to have this beauty show up and not have a live on parts to hang on it!

…beautiful work as always, Dave!!


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[donevwil]

All these recent fillet brazed, bare Onestos has me wondering if Dave's hands are ready to revolt.