# Need tube diameter and wall thickness advice.



## disease (Nov 27, 2007)

Here is the project. A simple and very inexpensive steel frame that can be used for off road riding and commuting. The low to mid range mid nineties KONAs are serving as a design template. Fork will be rigid.

I can get the head tube, bottom bracket shell, and dropouts from Nova cycles or some other supplier. I plan to use straight gauge heat treated 4130 chromoly from Aircraft Spruce. If the seat tube is not the correct ID, I will install an aluminum shim.

For the intended purposes stated, what diameters and wall thicknesses should I use? I am 6', 150 lbs, and ride fast but not wrecklessly. I am less concerned about weight than durability. I don't want frame that is too stiff or too whippy, and could carrier panniers for light commuting, not touring.


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## Francis Buxton (Apr 2, 2004)

Advice that I was given:
Don't get the pre-drilled bb shells, as they warp too easily during brazing. Get the 37mm OD Head tube stock.

If you're using straight gauge, go with 0.035 wall for the main triangle. 1 /38" (35mm) down tube, 1.25" (31.75mm) top tube. I might recommend buying an externally butted Nova seat tube, as they aren't crazy expensive and size right for a 27.2 post.

I used 5/8" x 0.058 for my seat stays, as that's what my local supplier had. They bent well with nothing inside them (sand or water) with no crimping. Probably overkill.

CurbDestroyer used 3/4 x 0.035 for his chain and seat stays and it looks like it worked well, but you will for sure want sand or water in them if you bend them. 0.049 is supposed to work a little better than the 0.035 for bending. The 0.058 is pretty frickin' heavy, for sure.

All of the above is probably a bit overkill for your weight, but it should be durable. I don't think you can really get straight gauge any thinner than 0.035 (0.9mm), so that's probably what you're stuck with.


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## disease (Nov 27, 2007)

Are you sure that 0.035" isn't too thin for the main triangle, especially at the welds? remember, this is only 90-110 ksi tubing. It's not high strength. I should have mentioned that it will be TIG or fillet brazed.



Francis Buxton said:


> Advice that I was given:
> Don't get the pre-drilled bb shells, as they warp too easily during brazing. Get the 37mm OD Head tube stock.
> 
> If you're using straight gauge, go with 0.035 wall for the main triangle. 1 /38" (35mm) down tube, 1.25" (31.75mm) top tube. I might recommend buying an externally butted Nova seat tube, as they aren't crazy expensive and size right for a 27.2 post.
> ...


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## coconinocycles (Sep 23, 2006)

disease said:


> , this is only 90-110 ksi tubing. It's not high strength. .


don't forget to weigh the benfits if tensile strength, MOE, elongation, ductility and ultimate yeild strenght............they make airplanes out of it..........check out the strength specs for easton's top of the line aluminum offerings and get back to us on your findings.........just sayin'......there's allot to think about beyond straight tensile strength #'s...........Steve.


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## jay_ntwr (Feb 15, 2008)

disease said:


> Are you sure that 0.035" isn't too thin for the main triangle, especially at the welds? remember, this is only 90-110 ksi tubing. It's not high strength. I should have mentioned that it will be TIG or fillet brazed.


Remember that ksi is "thousand lbs/square inch".


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## disease (Nov 27, 2007)

coconinocycles said:


> don't forget to weigh the benfits if tensile strength, MOE, elongation, ductility and ultimate yeild strenght............they make airplanes out of it..........check out the strength specs for easton's top of the line aluminum offerings and get back to us on your findings.........just sayin'......there's allot to think about beyond straight tensile strength #'s...........Steve.


I researched some tube makers' dimensional specifications and found several inexpensive butted tubes that were 0.9mm(0.035") at the butts.

I guess I will stop worrying and just build the damn thing! Thank you for you advice.


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## Vlad (Feb 7, 2004)

My Standard STA BMX frame, back in the day was built of .049 steel throughout, front to back, and weighed 7.5 pounds. Total overkill, even for BMX.


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## rustola (Jan 15, 2008)

Not sure if price is the primary motivator for going with straight gauge 4130, but the cheaper butted tubes (eg TT Verus) aren't really that expensive. Possibly cheaper than straight gauge if you're buying small quantities. Just did a quick lookup, Aircraft spruce has 1.375x0.035 at $4.95/ft, figure 3' so about $15. Henry James has a 34.9 9/6/9 Verus downtube for $9.25.


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## SuspectDevice (Apr 12, 2004)

Vlad said:


> My Standard STA BMX frame, back in the day was built of .049 steel throughout, front to back, and weighed 7.5 pounds. Total overkill, even for BMX.


We spent the month of July in 1998 building Kink Empire Rev B's. All .065 Ten freaking pounds! God those sucked.


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## restlessrider (Nov 29, 2007)

I agree with rustola - check Nova's tubeset deals too, since you are getting other pieces from them. They often have good sets for 29ers that are very cheap when compared with buying individual tubes.


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## Vlad (Feb 7, 2004)

SuspectDevice said:


> We spent the month of July in 1998 building Kink Empire Rev B's. All .065 Ten freaking pounds! God those sucked.


I remember those! The dropouts were hideous. I spent my childhood scavenging BMX frames and parts, and easily spent more time trying to keep that garbage dialed than actually riding it. As overbuilt as the frames and parts from that era were, it was a relief to finally have something that was reliable enough.

Do you have an inside line on an old Spooky-built Barcode?


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## Thylacine (Feb 29, 2004)

disease said:


> Are you sure that 0.035" isn't too thin for the main triangle, especially at the welds? remember, this is only 90-110 ksi tubing. It's not high strength. I should have mentioned that it will be TIG or fillet brazed.


Depends entirely what you're making the frame to do, and what your skill level is. Chances are, the answer is no if you're using a rigid Kona as a 'design template'.

The only reason to use plain gauge 0.035" wall 4130 vs Double Butted 0.9/0.6/0.9 4130 - assuming the design calls for that thickness - is to save dollars IMHO. Go with the butted tubing unless you plan on never riding the thing.

An external butted (bulge butted) seat tube is a nice one-stop solution from Nova or True Temper.


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## SuspectDevice (Apr 12, 2004)

Vlad said:


> I remember those! The dropouts were hideous. I spent my childhood scavenging BMX frames and parts, and easily spent more time trying to keep that garbage dialed than actually riding it. As overbuilt as the frames and parts from that era were, it was a relief to finally have something that was reliable enough.
> 
> Do you have an inside line on an old Spooky-built Barcode?


Besides having the drawings for them up on the wall at home, no.


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## rocwandrer (Oct 19, 2008)

Francis Buxton said:


> Advice that I was given:
> Don't get the pre-drilled bb shells, as they warp too easily during brazing. Get the 37mm OD Head tube stock.
> 
> If you're using straight gauge, go with 0.035 wall for the main triangle. 1 /38" (35mm) down tube, 1.25" (31.75mm) top tube. I might recommend buying an externally butted Nova seat tube, as they aren't crazy expensive and size right for a 27.2 post.
> ...


bad advice on the bottom bracket, imho. get a couple of the $4 prethreaded heavy wall BB's, and some straight tubing of about the same wall to practice on mitered to scrap tubing to be sure you can get a good joint without warping. it isn't hard with the heavy wall BB's, and they aren't much heavier than the thin ones.

5/8x.035 is overkill for seatstays, and 0.028 is readily available, but a little more finicky to work with. 5/8x0.049 will free bend (simple support, like a conduit bender head) cold without kinking. 5/8x.058 is crazy heavy.


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## nicolacycles (Oct 17, 2008)

SuspectDevice said:


> We spent the month of July in 1998 building Kink Empire Rev B's. All .065 Ten freaking pounds! God those sucked.


Yeah BMX went thru an aweful period of way overbuiltedness. how about those kmc garage door chains?


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## Francis Buxton (Apr 2, 2004)

rocwandrer said:


> bad advice on the bottom bracket, imho. get a couple of the $4 prethreaded heavy wall BB's, and some straight tubing of about the same wall to practice on mitered to scrap tubing to be sure you can get a good joint without warping. it isn't hard with the heavy wall BB's, and they aren't much heavier than the thin ones.
> 
> 5/8x.035 is overkill for seatstays, and 0.028 is readily available, but a little more finicky to work with. 5/8x0.049 will free bend (simple support, like a conduit bender head) cold without kinking. 5/8x.058 is crazy heavy.


I didn't say not to get pre-threaded, I said not to get the pre-drilled (like the ones Paragon sells). The pre-drilled ones are the thinner ones, and he felt basically the same way that you (apparantly) do, that the heavy-walled ones weld better, but really aren't much heavier.

Yeah, 0.058 is crazy heavy, but I could pick it up over lunch vs. waiting a week for it.


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## Francis Buxton (Apr 2, 2004)

nicolacycles said:


> Yeah BMX went thru an aweful period of way overbuiltedness. how about those kmc garage door chains?


For a while, I had a Mosh park bike that literally weighed 42 lbs. I finally had to get rid of it b/c I would hurt my shoulder trying to lug that thing around the skatepark. Of course, it didn't help at all that I hadn't ridden bmx in probably 10 years.


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## rocwandrer (Oct 19, 2008)

Francis Buxton said:


> I didn't say not to get pre-threaded, I said not to get the pre-drilled (like the ones Paragon sells). The pre-drilled ones are the thinner ones, and he felt basically the same way that you (apparantly) do, that the heavy-walled ones weld better, but really aren't much heavier.
> 
> Yeah, 0.058 is crazy heavy, but I could pick it up over lunch vs. waiting a week for it.


ah, sorry. I misread your post.


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## disease (Nov 27, 2007)

restlessrider said:


> I agree with rustola - check Nova's tubeset deals too, since you are getting other pieces from them. They often have good sets for 29ers that are very cheap when compared with buying individual tubes.


I will look again at True Temper Verus and Nova butted tubing. I had just assumed that straight gauge from Aircraft Spruce would be way cheaper. If inexpensive butted tubing is even just marginally more expensive, then it is obviously the way to go. The only problem with the Nova tubesets is that they are all BMX or 29er specific, and I want a standard frame for 26 inch wheels. I imagine that the only difference between a 29er and 26er tubeset(other than stay lengths) is that the 29er set will have a longer downtube, and maybe a longer seatube. The main tubes would be left with short butts if convereted to 26er sizes, which is good for keeping weight down.


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## coconinocycles (Sep 23, 2006)

disease said:


> The main tubes would be left with short butts if convereted to 26er sizes, which is good for keeping weight down.


 *exactly* wrong. do your drawing and get the tube lengths that are *just* long enough that you get the full use of the butting. don't chop off all the butting! just trying to help! Steve.


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## disease (Nov 27, 2007)

coconinocycles said:


> *exactly* wrong. do your drawing and get the tube lengths that are *just* long enough that you get the full use of the butting. don't chop off all the butting! just trying to help! Steve.


You are right. I don't want the frame to be too flexible. I will just build the main triangle for now, and then deal with the chainstays.


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## rocwandrer (Oct 19, 2008)

disease said:


> You are right. I don't want the frame to be too flexible. I will just build the main triangle for now, and then deal with the chainstays.


preserving the butts is about durability, not stiffness.


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## Evil4bc (Apr 13, 2004)

Vlad said:


> Do you have an inside line on an old Spooky-built Barcode?


I think my neighbor still has a green one sitting on the side of his house , saw it there one afternoon when I was over for a BBQ walked by and was like WTF that's a orignal T1

We had the T1 progression #002 at the bike shop i worked at back in the late 90's


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## BeatAFool (Jan 14, 2008)

I would just buy a elcheap 4130 double butt tubeset from nova or one of the other suppliers (whoever is cheapest and closest)....................... unless you live next door to Spruce you're gonna be paying shipping twice......... just my thoughts


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## Francis Buxton (Apr 2, 2004)

It's kinda hard as a newbie, but you really do need to have your frame fully designed before you buy any tubing, so that you get the correct length tubes.

You may find that one of the 29er tubesets will work for your bike if you choose the right length tubes. Mainly, it seems like you get the dropouts/brazeons 'free' when you buy the full tube kit. If you don't like the dropouts or a tube or two doesn't work right for your frame, you're better off to just pick and choose your tubes. The Nova 'kits' are a great starting place though.


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## coconinocycles (Sep 23, 2006)

Francis Buxton said:


> It's kinda hard as a newbie, but you really do need to have your frame fully designed before you buy any tubing, so that you get the correct length tubes.


correct. if you do not have a plan, you are not ready to buy supplies. 1st - learn how to read tubing spec sheets. the "tube kits" are aimed at 1st timers who are overwhelmed and just want to get at it. sure, in most cases it will work, but will it be optimum???? Steve.


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## carrion cycles (Sep 17, 2008)

SuspectDevice said:


> Besides having the drawings for them up on the wall at home, no.


i had a t1 progression build by you folks, best frame i ever rode!:thumbsup: 
also use to ride with a few kids from the brewster area that worked for you (or atlest said they did)


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## SuspectDevice (Apr 12, 2004)

carrion cycles said:


> i had a t1 progression build by you folks, best frame i ever rode!:thumbsup:
> also use to ride with a few kids from the brewster area that worked for you (or atlest said they did)


I think at one point anyone under the age of 20 who rode bikes in Putnam County pulled levers and polished tubes at Spooky for free.


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