DB tubes/frame mod'ing: Figured I'd ask
So, I did bunch of searching and reading. I'm impressed! The lot of you FB'ing guys are quite informed. Within all the great info, though, I still have the question....
I've toyed with the idea of building a bike frame, someday. After all the reading of everything involved......tools, materials, skill required.....I'll probably never do it. It's just not that important. Seemed like it'd be a fun adventure for a while, but then reality of it all sets in. It's a lot of cost just to be a backyard hobbyist. But, I've atleast learned how to make a homemade jig...hehehe.
That in mind, I've long deliberated over modifying a mtn bike frame I've had that's a little too big. Then, I thought.....given the paragraph above....I'd just sell or trade it. But, within this time, I just haven't found something I was really looking for....though, it may be out there. But, nothing seems to be getting any cheaper...lol!
So, with this mtn bike frame, I imagine I could have it mod'd and wind up with exactly what I've wanted and still cost less than another frame. (Plus, I've just gotten tired of acquiring crap). The frame is a DB cro-mo and atleast an inch would need to come off the TT length and height to have it fit just right. To do this, the TT, the HT, and the DT would need to be cut off and relocated with the DT welded at a steeper angle to keep the HT at the proper height. Problem is the butting.
I've read and seen pics wherein folks have had a frame modified or repaired, so cutting out tubes and/or relocating them appears okay to do if the circumstances will allow for it. But, in reusing the existing tubes, I have concerns about how much of the tubes are butted. IOW's, if I were to cut off a half inch or so from either end of the TT (for example), would there be enough butting left for a solid structure? I gather I couldn't really know unless I could see the insides of the tubing. Even then, how can you tell? Also, which tubes are actually butted? I read usually only the DT and ST are butted with most production frames. Would that be true? This a mid-end Giant "designed" in the US......but, probably actually made in Taiwan or some place.
If the ST is butted, the TT, being move down an inch, would be rejoined just opposite/a little lower than level with the center point of where the chain stays are joined at the back of the ST. Right now, the TT is joined above that location.
Here's a very close example of how it would wind up looking at the TT/seat stay/ST area:
Although, my end product frame would retain a horizontal TT and not sloped like that one. This would mean I'd be left with a couple of inches of ST sticking up where the seatpost is inserted, but I figure if the ST is butted there, and the butting atleast extends lower than where the seat stays are joined, cutting it down and slotting it for post binding purposes is probably okay. This would give me about 4 inches of exposed seat post in the end.
Anyway, I'm not intending to weld it back together myself. I met a professional structural welder who would do the TIG stuff. I'd only be doing the cutting and mitering on my jig so as to have the mod'd frame set up to take it to him for the welding.
Maybe this is a bad idea...lol! And, I hope I'm not frustrating the hell out of you guys who are tired of answering questions like this. The welder seems to think it's a fine idea because the welding points would be fresh compared to if I were wanting things rewelded in the original locations (save where the DT connects at the BB). This from a metallurgic stand point. The HT could be flipped around to weld to the front side, for example. It just depends on the butting issue. I realize new tubes don't cost that much....relatively, but if the original tubes can be reused, why not try? If it's a failure, I'm only out the $20 or $30 I could have gotten for selling the frame. Not a big deal.
So, what do you guys think? If there's any details you'd need to know, ask. And, whatever the consensus opinions, I'm not gonna argue them....promise......jus' so ya know.