Framebuilders - R&R bottom bracket lug on Cardiff track, and indtroducing myself.
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11-05-08, 03:34 PM
hello all, i've been lurking around for a bit. Time is coming when I'll begin my project, removing and replacing the BB shell on an old italian track frame.I'm also doing some work on a fork I picked up to go with the ^^ mentioned frame. I still have few questions before I begin but let me begin with an introduction that may save some misunderstanding.
I'm from portland or, and have a work back ground in tool and die making, and CNC manufacturing. So I am a machinist, but not a button-puncher only. I have also worked at the local steel mill, welding drag buckets. i mention this, as i feel I have pretty good grip on metal work, what color=whattemp and so on. While i havent done fillet brazing (or lugged brazing) , I have watched others enough times to feel i can begin some test joints with some scrap frame bits. I will do this first before doing R&R on the cardiff. I feel like I have the right filler on hand as well. i have some harris safetysilv56, some harris low fuming bronze in 1/16 and harris white and black fluzes. This is what avail at the local welding supply and was recommended by a few local builders. So with that preface, on to my questions.
I am still in the dark as to what torch tip and flame cone to use for lug work, different from fillet work? I'm using my pop's tanks, guages and torch and he said a small rose bud tip for a smaller tight soft cone for fillet and the largest rose bud 3/4" with 12+ holes for the BB lug, this makes a big, soft cone with lots of noise. he's no frame builder, so i wanted to ask you guys what torch tips, and flame profiles you use and like.
My plan is to use the harris 56% silver and the harris white flux on the BB lug, and the LF bronze and the harris black flux on the fork( it needs a new steertube, and the blades attached, it was "sweated" apart by the prev owner, a local framebuilder) am I on the right track with my filler/flux choices?
The fork crown is the std "silva" flat-top, tange blades and suntour drop outs. the blades are chromed about 1/2way which will match the frame's paint with proper masking and paint and decals. the steer tube is from NOVA, prethreaded 1" 240mm single butted.
The BB lug is the everest co brand road shell from NOVA as well. the CS sockets will need some adjusting I believe, but only 1-2 deg.
thanks for any and all comments. i appreciate it.
Rosebud is a general area heating deal, you can use it for brazing say a cast pump body because it throws out a lot of heat and gets big parts hot. That sounds to me like a cutting a welding torch gig. Framebuilders are normally using the single point nozzles sorta in the 35-50 thou range. The heat is not poured on directly but sort flicked on and off in a tangent. Normally they are using small bodied aircraft torches.
The Harris white flux and 56% no cad is a good way to go, though it seems like a lot of folks prefer similar stuff from either Henry James or Freddy Parr. Another option is bronze. Never tried that myself. I'll leave the rest of the lug stuff to others, except to say if you were planing on heating a chromed part, don't, bad for the health. With your background you probably know that.
11-07-08, 08:08 AM
First of all, why are you replacing the bb shell? If the threads are buggered, you can get an insert to convert Italian threads to English from bringheli.com (he used to sell them anyway).
There is debate regarding what size tip to use but many builders go for a fairly large tip (Victor 3 or so) with a gentle flame for BB work.
Make sure the tubes fit the sockets snug if you are going with 56% silver. If the sockets fit loosely, brass is a better choice.
11-07-08, 04:22 PM
Thanks for the info on the nozzles, thats the bit I'm still in the gray about. This is my father's oxy-acy set up. It's on loan so I need to invest is my own, for future frames and bike projects. What torch/guages is everyone using? I suppose mean "brand" but I'm assuming oxy acy, am I wrong?
I'm replacing the BB as it has a crack running halfway around the base of the seat tube lug, where the seat tube socket and the spindle shell meet. My first thought was to drill it to prevent further propagation and then TiG it, since thats what I'm most comfortable with. But the few local framebuilders said thats a no-no, the heat from TiG will make the old tubing brittle and most likley crack the Bb shell. I then though of doing a quick brazing repair but I was told the heat would "sweat" the filler out. So I was under the belief that replacement was my only option.
TIG won't harm any metal you are likely to come across in bike building (that said I don't know the specific metal you are dealing with here). There was a whole BS as much as possible campaign to stop the barbarians which left the industry to develop a path for rehabilitation after they were stuck with the fact that steel forward would be mostly welded. TIG may add enough heat to cause problems for adjascent brazed joints. of course they could be rebrazed. TIG is also ideal for taking a very slow stitch approach that won't build a lot of heat. It will take a lot of heat, to get the braze out.
Oxy somethingorother is a good bet. I use OP, and some others do also. OA is far and away the most comon but is dirtier, hotter (not much advantage here where welding and cutitng is not the use), and kinda a dangerous choice for the home shop. That said, if you already have the OA you aren't really adding anything new to the mix by using it, and that is what most use. The smith aa1a torch is the sort of thing. I use a Meco aircraft torch more like a TIG torch, but I like to weld with it also.
"with lots of noise."
You don't want the noisy setting you want the quiet more liquid one. If it is really noisy that usually means too much oxygen and you will burn carbon out of the steel.
11-08-08, 10:33 PM
My pop just dropped off his bottles, guages , torch and such and while there are 8-9 single hole nozzles, each with varying size orifice, I don't see a way to attach them to the torch. I think I may have the wrong fittings or possibly missing some fittings. The torch is a "WARD MASTER" brand like montgomery wards i believe, so that'll tell you how old the torch as well as the guages are, I'm guessing 1950's. the hoses however are new, last year, harris co. hose and adapters. I'll wait until monday when the welding supply shop is open, and get set up right. I did manage to get by my former workplace and procure some firebrick and refractory, for a nice little brazing station. My plan is to set up a little hot box for the BB shell. I suppose I will forge ahead, perhaps in error, with my plans to replace the BB shell on the frame, and the steer tube on the fork. Thanks.
11-09-08, 08:31 PM
peterpan1, the oxy-propane set up you mention, is that similar to the stuff used for HVAC? to get a similar flame, what happens to the tip orifice larger or smaller? I like the idea of O&P, propane is much cheaper here than acetylene. I can keep my oxygen stuff, correct? how about my acetylene hose? What torch do you personally recommend, other than the meco mini. I didn't like how hot it got with no handle.
I'm torn, if I must replace my torch handle ( my dad has since given me his OA stuff as an excuse to upgrade) I'm wondering if it's not wiser to switch to OP now. I'll have to ask my local favorites (sacha @vanilla, j. hufnagel, ira ryan) what they use. Since I have no previous attachment to one or the other, picking one and sticking with it to develop some skills is a must. Thanks for taking the time to answer my new guy questions, I really do appreciate it.
11-11-08, 12:42 AM
looks like I have gathered all the necessary items, and tomorrow I'll begin on the BB. I have been unable to get someone local to let me watch them do the BB shell. One of them also mentioned that replacing one is very difficult and he wouldn't do it, he'd be afraid something outside his control would cause a problem and he'd catch the blame.
So I've been looking around the ol internets in search of as much info as I can gather. I see that most builders do the main triangle first, putting the seat tube and down tube in the lug at the same time, fluxing and brazing them both at the same time. Is there an order? ST first? DT first? Since I am not disassembling the whole frame should I do them all (DT, ST, CSes) at the same time? working front (of the frame) to back? I also have questions about surface prep, I'm told clean surfaces make better joints, but should they be smooth as in wet sanded? or rough as in just after filing and sand blasting. Thanks.
11-11-08, 08:39 AM
No need to polish the metal, just clean it really well to foster a good joint - sandblasting is fine.
11-11-08, 08:18 PM
I wish i could tell you I've gotten to that point but I havent. I'm having trouble getting the old BB off. silly me thought it would slip right off. ha ha pretty good one, I know better now. Even lost my temper, havent done that in a long time (well not at an inanimate object anyways) it's now in many chunks, and theres lots left to file off. i did manage a 1/8" tear/crack in the end of one chain stay. It seems like it will be removed when mitered to fit the new BB, well i hope so at least. I'd hate to turn this into a BB and chain stay replacement. I figure if I come out of this will all my fingers and toes and some knowledge I will be pleased. If the bike is ever road worthy again, thats an extra bonus.
11-12-08, 03:55 PM
this morn i managed to pull the rest of the lug off.It was not pinned. If theres a way to remove lugs in one piece, so as to re-use the for practice etc.. Please share. Other wise i think in the future I will "pie slice" them so they come off real easy like when hot. I think the tubes are still in ok shape. the end of one chain stay is a little cooked where I tore it. I think that will have to be mitered off to fit the new BB anyways. I still have some questions before I proceed.
what order should I re-braze the tubes in? My plan is to flux both the DT and ST, and do them together one right after the other. Then, cool down, clean up, and flux and braze the CSs' .
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