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  1. #1
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    Adhering braze ons

    I just bought this item... http://www.ebay.com/itm/221094758568...568%26_rdc%3D1

    Instead of welding it to my aluminum frame, do you think this would work?.... http://aeropack.net/images/J-B_Weld_new.jpg

  2. #2
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    This looks like a really bad idea... what you can do is to use a set of those that is actually bolted together... check out at novacycles.

    http://www.cycle-frames.com/bicycle-...-AL-FRAME.html

    The only thing u need to do is to drill the whole and maybe use locktite but is pretty straight forward.

  3. #3
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    I'm not too crazy about drilling a hole into a downtube. Maybe I will hire a welder to actually braze it on.

    Or I can drill a hole in a hose clamp just big enough to fit over the braze on piece.....
    worm-drive.jpg
    Last edited by starving; 08-16-12 at 10:10 PM.

  4. #4
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    You cant braze the ones you bought in an aluminum frame to start with.

    You need to get aluminum bosses and get them tiged or miged to the frame, simpler to put the ones in the picture because you dont have to paint the bike, with mig or tig is almost sure that the bike might need a good retouch.

    Good luck.

  5. #5
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    Are you saying I can't use these for aluminum because of the downtube diameter?

    The thick aluminum downtube on my bike is actually shaped to have the diameter of a steel downtube on the sides. I have 2 bikes with the same exact downtubes, but only one came with braze ons. The one with braze ons work perfectly with downtube shifters made for steel bikes.

    Anyway, I will try my hose clamp idea. If it works, I will post a photo.

  6. #6
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    What im saying is that the one you bought are for steel tubes not for aluminum, unless you know somebody that magically can braze steel to aluminum you cant use the bosses you bought.

    Probably your bikes have the bosses glued, you cant weld/tig/mig or braze aluminum and steel together... you can glue it tho.

  7. #7
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    Glue is fine. I don't care how sloppy it looks. It's a cheap bike. This putty works on all surfaces..... http://www.amazon.com/Weld-8267-S-St...owViewpoints=1

    Better yet, putty combined with a hose clamp.

  8. #8
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    First of all, you can't braze or weld steel to aluminum.

    Secondly, for the hose clamp idea, I can almost guarantee that it won't work well. You might get it to work for a short bit but as the hose clamp bends with use of the shifter, the shifting will get worse and worse.

    And there is a good chance that the hose clamp just won't hold the brazeons well enough at all. Hose clamps aren't really designed for the kind of tension that shifter cables will put on them.

    However if you can find a more solid style clamp, it *might* work reliably. I searched google for motorcycle exhaust clamps and came across these:
    http://www.motosport.com/motorcycle/...EXHAUST-CLAMPS

    Now those could possibly work if you braze the brazeons to the clamps. Not sure if the clamps being stainless throws a monkey wrench into the plan though.

  9. #9
    Senior Member DannoXYZ's Avatar
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    Ferrari actually has a process called Feran that can join steel and aluminium. Some sort of brazing with a filler metal that sticks to both. Don't think it would be cost effective for you to send your bike to them to attach two shifter bosses.

    Hose-clamp will not work, because it will get in the way of the boss-cover washers. These have a precise square-shape on the back side that must fit over the shifter-boss. Then the outside of the washer has slots that the fingers of the shifter mates with.

    JB-Weld will also not work. I tried this 30-years ago and have seen numerous other people try. It never worked. Here's a thread where I referenced a real epoxy with 4x the bond-strength of JB-Weld: 1990 Trek 1000 Aluminum Downtube Shifter Broke Off/Broken. Options? Pics inside!. However, this will ONLY work if you have sufficient surface-area for bonding, which you will not with just the bare boss.

    Easiest and cheapest solution would be to use a clamp-on shifter-boss assembly. Two bosses with a band-clamp specifically designed to hold the bosses in position. These bands came in different diameters to fit different tubing-diameters:


    http://farm3.staticflickr.com/2645/4...760_z.jpg?zz=1


    http://i.ebayimg.com/t/DOWNTUBE-SHIFTER-BOSS-CLAMP-BAND-4-CAMPAGNOLO-SHIMANO-/18/!CBi,u!QB2k~$(KGrHqYOKj4EzdTL,)ruBNIKos3qMg~~_3.JPG
    Last edited by DannoXYZ; 08-17-12 at 12:42 AM.

  10. #10
    bike whisperer Kimmo's Avatar
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    What Danno said. You might have to look for a bit to find one in the larger diameter an aluminium downtube is likely to be.

    Also, pretty much nobody gets welding done on aluminium frames, because the frame has to be heat-treated again afterwards.

  11. #11
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    What about Krazy Glue Gel? I could glue the boss as well as the part of the downtube shifter housing that contacts the downtube.

    Since I want a downtube shifter for my front derailleur only, I can buy that pre-made boss clamp, and glue the whole clamp to the downtube since it is too small for the aluminum downtube.
    Last edited by starving; 08-17-12 at 07:52 AM.

  12. #12
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    Just forget gluing; it won't work and you will make a mess of your frame. If you cannot find clamp-ons which fit CORRECTLY, maybe you should consider bar-end or stem shifters.

  13. #13
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    Gluing won't work because there's a constantly changing shear stress on the part, which will ping it off in fairly short order. You'd need quite a bit more area at the base for glue to work. If you check an aluminum frame with a glued-on braze-on you'll see they have much larger bases, and also bolster the glue with one or two rivets.

    Your best bet is to drill it across and use a pair bosses designed to be mounted this way, as suggested by ultraman. If you only need a boss on the right side, and it's for a cable stop and not a lever, you can drill the one side, install a riv-nut, and screw the boss to that with a longer screw. For this to work, you'll need a few extra steps.

    1- countersink/counterbore (or Dremel) the back of the boss so it clears the protruding head of the riv-nut and sits flush.
    2- shape the boss so the curvature matches the tube
    3- drill out the threads of the boss, so the screw slips through an engages only the riv-nut threads. (critical - you cannot engage two threads at the same time)
    4- remove the paint on the frame under the boss so you can bond it directly to aluminum, not paint.
    5- bond the boss to the frame, with bonding product made for this job, or super glue as a substitute, and tighten the assembly using the through screw to the riv-nut. Note - the glue is only to stabilize the joint, but it depends on the screw for strength. Do not attach the cables until the job is fully cured (I always add 24hrs for a safety margin).

    This would be better yet with an aluminum boss, but your steel one will work if you can't find an aluminum one. Given what's involved, don't let saving a few bucks reduce the quality of the job, and use the steel one only if you cannot find an alloy one. Also don't worry about the hole, the boss fully buttresses it so it won't affect the strength of the tube in any way. Manufacturers drill tubes to install bosses all the time.
    Last edited by FBinNY; 08-17-12 at 08:57 AM.
    FB
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  14. #14
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    Thanks guys. I regret not buying this bike instead.... http://www.bikesdirect.com/products/...lt_dt_xiii.htm

    Downtube shifters and granny gear capable.

  15. #15
    Light Makes Right GV27's Avatar
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    Quote Originally Posted by dsbrantjr View Post
    Just forget gluing; it won't work and you will make a mess of your frame. If you cannot find clamp-ons which fit CORRECTLY, maybe you should consider bar-end or stem shifters.
    +1. What are you trying to accomplish? Friction shifting or the look of downtube shifters? If the former, take dsbrantjr's advice. If the latter, get a different frame. Seems like a good "classic" bike would be a much better bet that some POS BikesDirect bike. Just my $.02.

    Chris

  16. #16
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    Quote Originally Posted by starving View Post
    Thanks guys. I regret not buying this bike instead.... http://www.bikesdirect.com/products/...lt_dt_xiii.htm

    Downtube shifters and granny gear capable.
    put the regrets aside and do what you need to make this one the way you need it to be. Or consider selling it and start fresh. If you're using a front derailleur and handlebar shift levers, buy the bolt on kit and install it. You'll be very happy with the results if you do the job carefully.

    However if you're using downtube levers, then I suggest selling this and buying something else. The constant movement of downtube levers will make the bolt-on kit less than ideal, and it could be an ongoing source of frustration. I'm not saying it can't or won't work with DT levers, just that it'll need more frequent service, than you might want. You can make these work very nicely, however, if you bolster them with glue to stabilize the parts so they don't work loose with lever movement.
    FB
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    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

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  17. #17
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    Quote Originally Posted by GV27 View Post
    Seems like a good "classic" bike would be a much better bet that some POS BikesDirect bike.
    Chris
    I started bike racing in 1985. I have 2 BikesDirect bikes. They are excellent for the price. Since I no longer race, and I am a good mechanic, they are perfect for me. Most of the "name brand" bikes these days are made in China anyways.

    The reason I want a downtube shifter for my front derailleur is that the Shimano ST-2300 brifter sucks for front shifting.
    Last edited by starving; 08-17-12 at 10:14 AM.

  18. #18
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    Quote Originally Posted by FBinNY View Post
    put the regrets aside and do what you need to make this one the way you need it to be. Or consider selling it and start fresh. If you're using a front derailleur and handlebar shift levers, buy the bolt on kit and install it. You'll be very happy with the results if you do the job carefully.
    I actually installed these stem shifters yesterday..... http://www.amazon.com/Shimano-Sy20a-...+stem+shifters

    I don't like the stem shifters at all. They friction action is very sloppy. The Shimano SL-R400 downtube friction shifter is much nicer because instead of using tension from a tightening knob, it has a unique internal mechanism that keeps the shifter from moving when the chain is on the big chainring. Notice there is no tightening ring on the front shifter...... http://techdocs.shimano.com/media/te...9830612533.pdf
    Last edited by starving; 08-17-12 at 10:12 AM.

  19. #19
    Light Makes Right GV27's Avatar
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    Quote Originally Posted by starving View Post
    I started bike racing in 1985. I have 2 BikesDirect bikes. They are excellent for the price. Since I no longer race, and I am a good mechanic, they are perfect for me. Most of the "name brand" bikes these days are made in China anyways.

    The reason I want a downtube shifter for my front derailleur is that the Shimano ST-2300 brifter sucks for front shifting.
    They do seem to be pretty good for the price. But a used bike that is worth $300 is certainly going to be higher quality than a new $300 bike. That goes for just about anything you can think of. Hell, if you're good at wrenching you can get an awesome broken down old bike for near free and fix it up. Check out the Classic and Vintage section. The things guys produce by putting $100 into a $50 old bike are pretty impressive.

    Well, if you just want friction for your front and will be running a brifter for the back, it seems like it would make more sense to go for a bar, stem or shifter-mounted solution:

    Retroshift: http://retroshift.com/

    Paul's Thumbies: http://www.paulcomp.com/thumbies.html

    Velo-Orange bar mounts: http://store.velo-orange.com/index.p...22-2-23-8.html

    Rivendell's shifter page - several solutions here: http://www.rivbike.com/Shifters-s/132.htm

    Chris
    Last edited by GV27; 08-17-12 at 10:41 AM.

  20. #20
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    Chris, I am liking those "thumbies". Looks like they would allow me to install my favorite Shimano SL-R400 downtube shifters onto a stem or handlebar. Your post is the most valuable post of the day.
    Last edited by starving; 08-17-12 at 10:51 AM.

  21. #21
    Light Makes Right GV27's Avatar
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    Quote Originally Posted by starving View Post
    Chris, I am liking those "thumbies". Looks like they would allow me to install my favorite Shimano SL-R400 downtube shifters onto a stem or handlebar. Your post is the most valuable post of the day.
    Thumbies are sized for bars. There is a similar IRD part on the Riv page for quill stem mounting.

  22. #22
    Senior Member the_tool_man's Avatar
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    After the first few comments on glueing, I got a bit nauseated, so I didn't read the entire thread. Apologies if someone addressed this already:

    The futility of glueing, bonding, welding, etc has been covered. But I want to add that any bike I've ever seen that was properly set up to use a clamp-on downtube shifter has some sort of tab or boss to keep the shifter clamp from moving down the tube. My Fuji has a brazed-on tab specifically for this reason. I converted to bar ends (which I very highly recommend), and use the original shifter tab to hold a similar clamp-on bracket where the brake cable housings terminate along the down tube.

    Since your bike doesn't have this tab, I suspect any clamped-on shifter will gradually work its way down the tube, causing loose cables and damaging the paint on the frame. Or, aluminum being relatively soft, the clamp will dig into the aluminum, which will leave an usightly mark should you change your mind. Given that aluminum has no fatigue limit, I'm not sure I'd want gouges in the middle of an important structural member.

    All of this seems to stem from your desire for better shifting. Why not just upgrade components (better brifters or bar-end shifters, for example) or get a different bike?
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  23. #23
    coprolite fietsbob's Avatar
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    I just bought this item...
    set it aside in a bin for when you have a steel bike
    and are willing to burn the paint off , and braze it on with molten brass.

    Mechanically.. one may braze it on a backing piece, of steel,
    paint it, then Pop-rivet the backing piece onto the aluminum tube..
    Last edited by fietsbob; 08-17-12 at 11:15 AM.

  24. #24
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    tool man, looks like I am going with either bar end shifters or GV27's recommendation for adapters that let me mount downtube shifters onto my handlebar.

  25. #25
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    Quote Originally Posted by fietsbob View Post
    go with the band strap on suggestions..
    I cannot find one that fits oversized aluminum tubing.
    Last edited by starving; 08-17-12 at 11:43 AM.

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