[HAR*DC*COREphil]

does anyone know where i can get a few of them? i checked a bunch of the frame building sites but couldn't fund any

 

[Rik]

DIY?
That way you can also add a touch of uniqueness to the front end as well.

 

[dw]

You would have to build it yourself. Better have a HUGE downtube to weld to it if you want the frame to last.

 

[sikocycles]

Bill at clif cat uses them...

 

[ioscope]

Can't you just buy the steel tube in 4130??

 

[buildyourown]

There isn't a standard size steel tube that works for 1.5
For 1.125, there are several options that leave you with some material to ream after welding.
Unfortunately, you will need to get access to a lathe or get really creative.
One option is to use really thin tubing and braze reinforcing rings on the race area. If you're good with a hacksaw, you should be able to accomplish this without a lathe

 

[CreeP]

ya, something like this seems the best way.

do you have the standard measurements for 1.5"?

btw, you're looking at a tube of around 51mm in diameter which is 2inches, which is not really outlandish.

 

[CreeP]

if not, download here: http://www.onepointfivestandard.com/tech.asp

 

[buildyourown]

btw, you're looking at a tube of around 51mm in diameter which is 2inches, which is not really outlandish.

A 2" tube with a 1.95 ID only gives you .025 wall thickness.
Go with a piece of 2.125 x .065 and make some reducer rings out of 2.0 x .049

 

[CreeP]

i can't visualize 25 thousandths of an inch, you've got to work in mm, i'll do the math myself, that's .6mm which is, yes, a bit thin. you'd probably want something around double that.
however i mentioned the dimension solely as a figure for contemplation. You don't exactly see a whole ****load of 1.5" steel headtubed bikes. The only examples i can think of are Draco and a short lived version of the cliffcat tankass. In other words, to answer the question: "ok, so now i've commited to this, what have i got myself into?" Interestingly the draco uses/d a downtube of a significantly smaller diameter than the headtube. Far from ideal but it probably works out okay. If you were going to fillet braze the bike it would be that much less of an issue as your joint isn't as violent.

the more i think about it the more it seems like a machined headtube is the direction to go. but what do i know. -secretly zedro and buildyourown are thinking: "chuckle, chuckle, ya exactly, what does he know?"

BYO's idea just above sounds a charm. It may not be the prettiest, especially if you're stuck to standard bike tube diameters for the two abutting tubes, but it'll work.

 

[CreeP]

BTW, on the subject of joining tubes, those of you who've built bikes, and are at the moment, what method have you used for mitering? End mill, or abrasive type industrial notcher? Hole-saw cuttoff type? Hand filing?

 

[buildyourown]

BTW, on the subject of joining tubes, those of you who've built bikes, and are at the moment, what method have you used for mitering? End mill, or abrasive type industrial notcher? Hole-saw cuttoff type? Hand filing?

I have my own CNC mill, so that's what I use. It is very accurate, but it takes awhile to setup.
When I worked at a custom shop, we used hole saws in a bridgport. Reasonably accurate, but quick. You have to compensate for the hole saw "pulling" the tube about .010. Not much, but enough to see with the naked eye. You also usually need to finish the miters by hand with a file to get a water tight fit.

I know guys who can cut a miter by hand faster than I can with a mill. It just takes practice. Do you know about tubemiter.exe?

Never used the abrasive notcher before. I've seen some dope homemade beltsander setups though

 

[CreeP]

yup, that's what i used, er, my friend used, i use a Mac so he had to print out the patterns and we mitered the tubes by file. The plan is to get a JMR tube notcher.

it's gotta be handy having a mill.