boostedgsr1234

hi there, im looking into building my first hard tail mountain bike frame from aluminum, iv been into metal fab. and tig welding for several years now, so making a jig and welding expertiese are not my issue.
My main question is what size material to go with, i really like klein's frames alot, the light weight fatter tubing style, but i cant seem to find very much info on what size, and type of aluminum to use, i know alot of bike are made with 6061-t6 but what i.d.,and o.d.? and above all where to get it, another big question is, is there any place i can buy the main parts like the head tube, the crank tube and the pieces for the rear wheel?
im sorry in advance for the amature questions but id really like to get this right the first time, im new to the site so if there is a better forum for my questions please point the way
thanks
joe

NoReg

You are in the right place. I would trot over to Nova or Henry James sites and peruse their catalogs. High end Aluminum bikes may require that you have the whole frame heat treated, and there is little advantage to the end result in a diamond frame that it would really be worth your while. On the other hand both steel, and to some extent ti, are quite home fabable, and will allow you to use oversize tubes or other stylish approaches. You should probably get deeper into this before throwing up any preconceptions as to what kind of material and end look you may want, since there can be significant variations in the degree of cost and difficulty without ending up with a bike that you would choose over another in a blind test, or that you would find had a higher cool factor.

There are oversized steel options also.

boostedgsr1234

thanks for the info, i checked out novacycles.com, they are great,, i decided on what im going to do, im going to buy there stainless steel bottom bracket lug, and a seat lug, then tig weld stainless chain stays and seat stays to that, then the front of the frame (the top tube, seat tube, and the down tube) i will build from carbon fiber, ( i work at a composite shop)i can miter the carbon tubing just like regular steel and bond it to the steel lugs and the head tube by wraping carbon around them.. i can just slip the carbon tubing in the lugs sleeve and bond it in with a high strength epoxy we have, then fair the carbon, it should look pretty good and be fairly strong.. what do u think?

NoReg

Normally you braze to a lug, not TIG. There are some lugsets like the Henry James MTB luset that hasn't lugs for the chainstays and you are intended to fillet braze them but TIG would be fine also. In general you can't bond carbon tubes to a lugset. Those designs assume a brazed joint to steel. When you bond to a carbon tube you are using secondary bonds, and essentially just bonding epoxy to epoxy, without any continuity in the fiber. As a general mater, that kind of bond requires sleeving with a 1.5 x tube diameter overlap, generically. You might be able to find some lugs like the Pacenti artisan lugs that would allow you to get a deeper interface, or you can just weld steel tubes to standard parts to make your own lugs.

If you want to wrap the tube junctions you don't really need to have lugs at all, just seems like a stress raiser. Carbon is normally matched with aluminum, there is good epoxy bond potential and they seem sufficiently strong for the various mechanical interfaces. So you would get an ALuminum BB and HT and just wrap them, which would take one back to the question about how to weld on the aluminum stays. At least the parts are smaller if they need heat treating. Nova does sell some aluminum, parts, and has tons of stuff not in the catalog. You could just ask them whether they have alloy rear end parts that don't require heat treating, though that would tend to be much lower efficiency that the carbon you are contemplating. They also sell carbon rear ends, that might simplify some fab.