Frames for little people

[jon_norstog]

from time to time I get requests from clients to build children's bikes. In fact, I've done enough "mini" BMX bikes to give them their own model name: "Fallen Angels"
Tube selection can be a bit problematic, because most frame tubes have long center sections. When you are building with a 44-46 cm (C-C) top tube, the actual tube length between miters can be as short as 40 cm. If you cut the top and down tubes out of typical tubes, you will be lucky to have some of the taper at each end, but little or no butt.

True Temper makes a few tubes with short center sections, HJ carries them

1.125" HRCXDT2 242mm center section .8-.56-.7 650mm OAL
1.25" HOX2TT 244mm center section .7-.56-.7 610mm OAL
1.375" HOX3DT2 270mm center section .9-.6-.7 665mm OAL

I've used Reynolds (R525) tubes in the past on slightly larger frames with pretty good success. These were "junior" and "expert" sizes, bigger than "mini" but not quite as big as a regular adult BMX bike. I may bring one of these to the Oregon Handmade Show.

jn

[Mark Kelly]

Why not do as the Ti builders do and "externally butt" plain gauge tubing to meet your requirements?

[jon_norstog]

Mark,

Most of the straight gauge I get is .9mm wall - much too thick for a kid's bike. Definitely there would be no point whatever in "externally butting" that stuff. FWIW I use .9-.6-.9 butted tubes on my adult BMX bikes - that's about right for a combination of stiffness and response.

jn

[afwalker]

Thanks for the info, hadn't noticed those tubes before.
Unless I'm reading the HJ specs wrong, the 1.25" HOX2TT center section is 153mm, and the HOX3DT2 was 296mm.
Probably should have used some of these for my daughter's 26" mtb I just built.
cheers
andy walker

[steve garro]

True Temper makes a few tubes with short center sections, HJ carries them

1.25" HOX2TT 244mm center section .7-.56-.7 610mm OAL
1.375" HOX3DT2 270mm center section .9-.6-.7 665mm OAL

I've used TONS of these tubes on bikes of all kinds.
Two of the most common tubes I use, actually.
- Garro.

[jon_norstog]

I've used TONS of these tubes on bikes of all kinds.
Two of the most common tubes I use, actually.
- Garro.

Steve,

It's heat treated! I don't usually go .7-.4-.7 for adult riders, but then I'm getting a slightly rougher clientele than you are. Including some bike-destroying monsters. I get a more, shall we say, **genteel** clientele I will definitely use lighter tubing.

jn

"Thursday"

[steve garro]

Steve,

It's heat treated! I don't usually go .7-.4-.7 for adult riders, but then I'm getting a slightly rougher clientele than you are. Including some bike-destroying monsters. I get a more, shall we say, **genteel** clientele I will definitely use lighter tubing.

jn

"Thursday"

Almost a decade of using those tubes on whatever they are long enough to fit on - stick the long butt forward.
I always get a rap from I don't know where that I only make heavier bikes but as you see it's not true.
Those make a fine 29er front triangle as long as the DT is long enough which is mostly with an ATC of <440ATC and it works great on 26" MTBs x 100mm fork, .7mm towards the BB, the .9x10cm butt to the front.

But, you're right - no BMX, dirt jumping or trials bikes from me, but trail bikes that get ridden mighty hard.....
- Garro.

[Eric Estlund]

From back in my BF days- this was on a bike I brazed up.



115 crank arm with a 53t large ring for a rider with a 16" inseam.