Monday, October 11, 2010

Geometry Continued and Tubing

Below is rSogn geometry with standover heights for different tire sizes. Do email me here questions about frame sizing.

Click on the table to embiggen.  


Here is what I would start with for all frame sizes:
  • rSogn: Standard diameter 8/5/8 top tube and 9/6/9 down tube.
  • The XL rSogn probably will have standard diameter 9/6/9 for both tubes. 
  • Heat treatment may be considered; This will increase stiffness strength and price.
  • 7/4/7 may be prone to denting. 


Erik said...

(Nerd alert) Heat treating won't increase the frame stiffness. It will increase its strength, fatigue life, and resistance to dents, but if you keep diameter and wall thickness the same, a heat treated tube will have the exact same feel as a non heat treated tube. (/Nerd alert)

I think all those tube specs look pretty spot-on.

Brien said...

Yep .. I'm sticking with a M .. thanks for posting the measurements for both sets of tires.

Anonymous said...

please try your hardest to keep the price where it is (or at least the pre-order price.) I don't want to have to worry about the price changing after putting down a deposit.

Ryan said...

I'd like to see slightly lighter tubing on the smaller rSogn sizes.
Maybe all 8/5 on the S & M?
Heat treating sounds like a good idea.

Anonymous said...

I vote for keeping the price in the range it's in, so I vote no to treating if it will raise the price more than say 100-150 bucks.

Here's a blurb about True Temper's heat-treated steel:

True Temper Verus HT tubing is precision butted heat-treated 4130 chromium molybdenum with unbelievable yield strength up to 175ksi. This increase in strength allows for smaller profile tubing, dramatically reducing the weight compared to stress relieved tubing. True Temper heat treatment results in microscopic fine-grained martensite formation, which increases the strength, hardness, and durability of the tube. Each tube has been designed from the ground up and heat-treated to specific levels to impart very specific characteristics and properties. True Temper Verus HT tubing has the perfect blend of stiffness, strength, ductility, and low weight, while retaining the classic “feel of steel.”

I'm a bit curious how making something harder does not affect its relative stiffness/flexibility.

Doesn't heat-treated also require more finesse with the tig welder, though? Make sure your build crew has experience with it (which is what may add most to the increased cost?)


giant hogweed said...

I'm not in favor of anything that increases the price. If there is a price increase I would like my deposit back.

Protorio said...

I'm considering swapping out my red Sogn frame for a new pewter one... so I hope its just strong enough to take a licking on trails like I do now.

Sean said...

@giant hogweed: The price will increase -if- we insist on 7/4/7, which would require heat treatment, for example. I would want to stay with 8/5/8 and/or 9/6/9 for that reason among others.

John Grasty said...

No heat treatment, no extra cost sounds just fine to me.

Erik said...

I'm interested to learn what the tubing material will be, and what the price difference would be to add heat treat. 8/5/8 isn't exactly plumbing pipe, so the steel will need to be at least of reasonable quality.

Michael_S said...

I guess we need to know what the price increase would be before we make a group consensus. Perhaps a 10-20% increase in price may be worth the savings in frame weight. I can go with what ever the majority opinion is.

Jim G said...

I vote NO on the heat-treated tubing.

Eric said...

Is standard sized tubing like current road bikes (ie, 28.6 top tube) or like my old RB-1 (25.4 top tube)?


Eric D

alex wetmore said...

Eric -- Standard sizing tubing is code word for 28.6mm downtube, 25.4mm top tube.

Mark -- Stiffness does not equal strength. Glass is very stiff, but not very strong. Kevlar is very strong, but not very stiff.

I think the proposed tubing specs sound good, although I wonder if the XL rSogn (not my size) should be a little beefier.

Rob in Seattle said...

I'd be curious to know what the price increase for HT tubing would be. The rSogn is shaping up to be a superb keeper frame, and if it's not *much* more for heat treated tubing I'd probably be willing to pony up for the benefits over the lifetime of the frame. I like the idea of not having to worry about denting or durability.

Sean said...

@Rob: Heat treatment would be about $25/frame.

Erik said...

For only 25 bucks, I would put my vote in favor of the heat treat. I agree with Rob that its a small investment over the lifetime of the frameset. That being said, I am sensitive to people feeling like they're being "upsold" after they've agreed to a lower price. I'm not quite square with changing the cost after someone has committed a deposit.

Also, I would not be in favor of using 7/4/7, regardless of heat treat. I'm gonna be gentle and describe my self as "rouleuresque", and I think given these frames' stated purpose, the EL spec tubing would compromise durability as well as handling. I can go either way on the heat-treat issue, but I fear that 7/4/7 would be a knock out.

Eric said...

$25 bucks isn't much in the grand scheme of things. But, I'd be worried about denting with the thinner tubes. Maybe I've been reading too much Rivendell stuff lately.

Would this be too whippy for some light touring? I'm thinking around 25 pounds of gear in a Carradice saddlebag and a bar bag. I'm only 175 pounds, and I'd be on the XL Snekka.

James Black said...

I'm not really sure how to value the improvement that heat treating brings to this frame, all things being equal. I don't think heat treating should be a reason to go to tubing lighter than what you've described above. The tubing you've described above is pretty light and flexy already, and I think it will be a fine enough bike without heat treatment. But maybe it's worth $25 for stronger tubes (assuming they aren't any lighter/thinner)?

Anonymous said...

Okay, I'm officially slightly confused. I thought the heat treatment would be for the 8/5/8 and 9/6/9 (down tube). The 7/4/7 was added as a bullet, tacked on (I thought) to say, let's skip that, since it's prone to denting.

If that is the correct assumption, and heat treating does nothing other than make the frame stronger and more durable for $25, it's a no-brainer from my point of view. Think of it as a super cheap insurance policy. And we're already getting a sweet discount. Just my $25 worth.

Alex--I was talking about the increased hardness, not strength. "heat treatment results in microscopic fine-grained martensite formation, which increases the strength, hardness, and durability of the tube."

For those who want to get real nerdy, some interesting information can be found here:

<a href="></a>

(one thing it does point out is the need for extra care in welding heat-treated steel, though perhaps not as much after tempering)

Now I wouldn't know a martensite if it bit me in the behind, but my instinct says that if something gets harder, it will resonate differently. And that may in fact not affect ride quality one iota. I fully admit this may be a consequence of my layman's knowledge of any of the various points under discussion. Anyway, can't wait for my new frame, whatever configuration of martensite is agreed upon.


Anonymous said...

Oops, forgot a "

Seabiscuit said...

I'm voting for heat treatment, at $25 it's a very reasonable investment.

BetweenTheWheels said...

One more vote for heat treating from a relatively big guy (240) who will be riding an XL Snekka, hard.

Michael_S said...

I'm sure most of you know that the weakest part of the frame are the welds. Paying extra for heat aged tubing increases the tube strength but does nothing for the weld joints which is where most frames fail. You need to heat age the welded frame assembly to improve overall frame strength. I'm not sure the heat aged tubing in the same thicknesses buys any increased durability in the frame.It doesn't save weight.

Rob in Seattle said...

I don't know enough about the metallurgy or frame-making to pitch in on the merits, but Sean if you think it makes sense I'd be happy to pay another $25 for heat treating.

Brien said...

I'd be worried about too much heat on a pewter tube ... but what do I know about metallurgy? Nothing .... Either way is fine with me.

Anonymous said...

Michael S--actually the weld is not the problem, and if executed correctly is usually the strongest area. It's the area just outside the actual weld that can be compromised, as explained in the link I posted above. That is my one concern--that and if welding the tempered tubing requires some special skill, a la Reynolds 753 (though not as drastic.) In that case you'd have a bike harder to dent but easier to crumple just beyond a weld.

Of course, it's entirely likely ht bicycle tubing has been tempered so none of this is an issue. I always thought the process was used mostly on very thin or OS tubing.

Brien, don't worry, the only thing pewter is the free beer mug you get with the frame for being an early adapter.


Michael_S said...

Mark, I'm not sure where you learned about welding (a website?)but a visually inspected weld is only about 40% as strong as the wrought material. Yes the HAZ can have reduced properties but unless you inspect the weld with dye penetrant or xray to esnusre it is defect free it is not as strong as the parent material.

JerryTX said...

I'll gladly stomach +$25 for increased durability.

Protorio said...

If I'd pay an extra $25, I'd rather have something especially useful like reinforced holes in the drive-side fork blade for internal wiring of a front generator set-up.

So long as it can take a lickin', I'm happy, so heat-treatment is not necessary for me.

Rob in Seattle said...

Hmm. Good point Estaban. Internal routing for a hub generator would be super cool.

Have we talked about a kick-stand mounting plate?

Anonymous said...


Actually, I had a welding shop for 8 years that I recently closed. I did mostly furniture and sculpture, so I was not certified, and I never sold anything more structural than a chair or table.

I think the link I posted above has some worthwhile material, despite the fact that it's just a website. Here's a bit:
"...there is little control of what happens in the area next to the weld called the Heat Affected Zone (HAZ.) In the photo left, the HAZ is usually referred to as the etched area between the melted weld deposit (visible by the coarse grains) and the outer etching boundary which in most steels defines an area that reached about 1300 degrees F. This line exists because a metallurgical change occurs in steel at that temperature that can be revealed by chemical “etching.” In essence the HAZ was heated to a temperature from about the melting point of the steel (about 2500 degs F) next to the weld all the way to not heated at all. For issues related to tempering, if the 4130 was tempered to 1050 degs F to achieve the required properties, after welding we have essentially tempered the tubing next to the weld from 2500 degs F all the way down to the 1050 degs F and lower! The time at temperature will depend on weld heat input, wall thickness etc. In general we will have an area much softer than the “after tempering” 150,000 psi! In fact it will probably be no stronger than if we welded the more typically used 4130 Normalized. Normalized 4130 tubing was cooled much more slowly from a high temperature, never creating the hard brittle Martensitic structure but is also much tougher. Normalized 4130 is usually about 95,000 psi in strength. The mixture of metallurgical structures present in the HAZ of welded Q&T 4130 may contain some brittle areas..."

My main point is, I'm not sure there are any benefits to heat treating these tubes under consideration. The frame is only as strong as its weakest point.

Eric said...

I think it's important to consider not just catastrophic damage, but the daily bumps and grinds of a bike. Tougher, heat treated tubing should deal a little better with dent resistance, chainsuck damage, etc.

By the way, does anyone think a 25.4mm top tube coming into an oversized 1-1/8" headset head tube will look kind of strange? I have the image of the steel mtb frames with integrated headsets--this junction looks like a broomstick poking a beer can.

Erik said...

@Eric, "broomstick poking a beer can". Awesome, that made me chuckle. It is a good analogy, and actually kind of ties in to the rest of the welding thread. Running a little tube into a big tube makes the weld basically a butt joint, the weakest weld, and one that us engineery types are told to avoid as much as possible. The more similar the tube sizes, the more the weld is loaded in shear, not in tension (think of the fishmouth joint wrapping as far as possible around the joining tube). This makes for a far more robust joint.

I would say that the TT/HT joint is far less stressed than the DT/HT, so I don't think that its a big deal. Not the most handsome, but not likely to fail anytime soon.

Michael_S said...

Mark not to belabor this subject, or offend you, but I've been working in the metal fabrication (Rocket Engines)business as a Production Engineer & Mgr for over 20 years. Basically,you've misinterpreted the information a bit. Welds are by nature 20-30% weaker than the parent material. The biggest offsetting factors are joint design, as Erik states, and weld quality.

Changing subjects (please) ,I'd rather pay the extra money for added features such as a nice rear cable guide or the internal wiring holes for a dynamo hub.

Sean said...

Evening everybody, I have been slammed with a hundred or so emails, so I should be able to respond to comments pretty soon. At this point, I honestly do not think it would be prudent to consider any more braze-ons so as to keep both models intact until we receive the prototypes. Moreover, I have been receiving pre-orders so I will want to keep everything as is. Heat treatment is probably the only thing that needs addressing by tomorrow. And then there will be some other things I will share. Cheers.

Anonymous said...

Michael S. No offense taken, I readily admit to being a hobbyist welder not an engineer fabricator, and have no interest in proving I am right, just finding out what the deal is. Anyway, my main question way back jibes with the weld quality issue, which I think is more of a factor with HT tubing. Did not really mean for this to get so long winded, sorry! I think although I may have gotten there by the wrong route, we agree that heat treating is probably not necessary in this instance.


alex wetmore said...

"I think it's important to consider not just catastrophic damage, but the daily bumps and grinds of a bike. Tougher, heat treated tubing should deal a little better with dent resistance, chainsuck damage, etc."

It isn't clear to me that heat treating tubing does help there.

It is less likely to dent.

It is not less likely to be scratched by a chain (which is hardened too). Once it has deep scratches they are more likely to act as stress risers and cause a crack.

I don't see the win for heat treated materials on 9/6/9 tubing. I don't understand why the decision would be made for different sizes either, the heat treated tubes won't make the larger frames stiffer.