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  1. #1
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    Anyone advise a Heat Treater for bike Frames in the Bay Area

    Hello, during a routine tune up I noticed my wifes Superlight Santa Cruz 2001 had a crack in the toptube to seatube union. I am investigating how to possible go about repairing this crack. She rides very mellow and just got back on the bike after having kids for several years. I know the bike is old and thin but we just don't want to shell out for a new rig right now. This area should have had a gusset like the other unions but it didn't.

    I would like to repair this 'last year made in the usa frame' Santa cruz was no help, they want the original receipt and we don't have it. I have many options for the weld repair, the paint job is easy, but I am scared of the heat treaters and the damage they could potentially cause. I know there are professional turn key repair shops but I don't have $500 to throw down for this.

    If anyone could recommend a heat treater in the bay area that is familiar with 6061 bikes I would be very appreciative and it would save me lots of time.Anyone advise a Heat Treater for bike Frames in the Bay Area-thumbnail_img_2837.jpg
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  2. #2
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    I've not used them, but Thermofusion in Hayward have been recommended to me as being affordable. However, I guess that'll cost at least $400, before you prep/weld/(align?)/ream/paint/etc...

    If you do go down this path, first check that everything else on the frame looks perfect, I've seen quite a few of those frames with cracks in the rear triangle.

    Wrapping the area in carbon fiber would be a more affordable way to get a few more miles from this frame.

    I'd recommend against all of these options, finding a used frame for sale is certainly a better fix and probably cheaper. You might be able to sell the rear triangle and shock for the price of a used hardtail frame.
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  3. #3
    pvd
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    A 2001 mountain bike frame is worthless and a poor investment.

  4. #4
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    Ha, ok, glad you gave me that input. I suppose I should just throw it in the garbage and have my wife stop riding with the kids to expose them to trails and have fun... or take the 50$ I plan to fix it with and buy a huffy at Walmart instead.

    Wow, that is a really harsh reply that is actually very assumptive and not helpful. YES, I realize how nice the new frames are and how much better the new bikes are. I do not have piles of cash to throw at a new bike right now for her. I am likely going to sandblast it at cost using a unit I have access to minus materials... then use a friend to weld it who is an expert welder of all types of metal. HE likely has the 6061 I need and if he doesn't McMaster has the piece I need for under 10$. The oversize gusset I am planning to possibly use is located such that I might be ok for years without heat treating. With some stress analysis software that I use often it took only an hour to do a quick model and estimate the gusset I need to make the annealed strength good enough and possibly not do T6 hardening. then I rattle can the paint job back. If done right, I have had rattle can paint jobs hold up decent, not as good as a $200 powder coat, but good enough.

    The heat treat question I felt was fair to ask the local experts...Not everyone always needs to throw away what mostly works. One day we will get her a new bike, that time doesn't have to be now. The way she rides the bike isn't going to fail catastrophically, it will crack, and I maintain it myself and inspect it pretty regular. it will be fine for a few more years.
    if it cracks again right away I will probably fix it. I can fix anything, do it all the time.
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  5. #5
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    thanks for your thoughts, great input and good ideas, I had not thought about wrapping with Carbon. Very interesting idea, will look into that... if not for this time next time... I am lucky enough to know a few welders, I can machine the gusset, have painted bikes many times over the years. The mechanic work is trivial, have all the tools.
    if I can get a heat treat job for under probably 100 to 150$ I might heat treat it, else I might put in a bigger gusset and see how long it lasts... will look into the carbon wrap idea. thanks so much,
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    Pvd is an arrogant a$$. I won’t to say whether he’s a donkeys, camels or horses a$$, but the seven pointed star says he’s one of the three… And for the record I’m not saying he’s a dumb a$$
    Without getting into too much personal information, I’ll leave you to decide if your wife is light enough for this frame treatment. If the riders light weight you can arrest the cracks with a drill on either end of the crack. Then put a seat post into the first half inch of the seat tube and clamp it firm. Mix some good epoxy and work it into the crack as your cycle a load on the seat back and forth opening and closing the crack to work the epoxy in.
    The reality of it is, if you have enough seatpost imbedded in the frame, the seatpost can become the structural member. Maybe get a longer seatpost if that’s not the case. Or better yet get a nice long seatpost to glue the son of a gun into the frame. Epoxy can come loose with steam and heat, so don’t think that epoxying a seat post into a frame is the last time you’ll get it out. But plan on it

  7. #7
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    By putting in a gusset, you might actually be better off not heat treating it. Heat treating increases the hardness & the brittleness. This is what causes the cracking to start. I would probably put 2 gussets on there, one each side of the tubes, with the edges of the gussets aligned with the center line of the tube/pipe. When looking down on the bike from above. Bit hard to explain. If you're careful with the heat input during welding, you can still get a very good % of the parent/base metal strength. It's been a long while since I developed any procedures for Aluminium welding, but I seem to recall over 90% With the GMAW (MIG) process, we could get it through the pressure piping & vessel code requirements, without post weld heat treatment. But that would look a bit ugly on a bike frame

  8. #8
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    If you are considering no heat treatment, then don’t bother with a gusset. All the extra heat you will put in, will negate any “benefit” from the gusset. I’ve repaired loads of aluminium frames over the years, for me, I’d just weld the crack and then ride it. Just keep an eye on the entire frame for more cracks, that 1 was more than likely cyclic fatigue, the rest of the frame will have been through similar loading.

    Edit, Don’t blast it to strip paint. You’ll maybe make it harder to spot any other cracks.

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    Sounds like you're getting a few different replies here, so I might as well add my .02

    I think searching for an "affordable" heat treater is probably pointless. It's an industrial process that is expensive and requires skill to achieve correctly. Ever wonder why so few builders in the US build in 6xxx series aluminums?

    I think my vote is to repair the weld, then put a gusset over it. When you bring 6xxx aluminums to welding temperature, they anneal. So if you just weld the crack, you'll leave the only annealed part of the frame in the zone where it was getting the most stress (why it cracked to begin with). If you at least throw a good gusset between the TT and higher on the ST, hopefully the added metal will offset the lack of heat treat. For all the aluminum frame repairs I've done, I've just added extra metal where possible, and it seems to work.

    But I also agree that if you can't do it cheap, just find another bike. There are loads of mountain bikes from the 2000s that people are practically giving away.
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  10. #10
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    I'm also in the "drill the ends of the crack, have your friend weld over it, rattle-can it, and be done" camp. Any more effort and expense isn't worth it.

  11. #11
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    Wow, thanks all for the great input, we really appreciate it!!
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  12. #12
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    Thanks for the input, this is what the rest of the other gussets on the bike look like...
    you mean like this, and one on each side??Anyone advise a Heat Treater for bike Frames in the Bay Area-img_6811_gusset.jpg
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    Quote Originally Posted by ventana1 View Post
    Thanks for the input, this is what the rest of the other gussets on the bike look like...
    you mean like this, and one on each side??
    Yeah. Pretty much. Here's what I would do personally. Just a quick sketch. You don't want to concentrate the stresses in a small area/point.


    I just had a quick look, & you typically lose about 40% in strength from welding, with no post weld heat treatment. Not the end of the world

    Edit -if the frame is 6061, I'd be using 5356 filler wire for the repair. A bit stronger than 4043.
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  14. #14
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    Why would you brace it on the side that *didn't* crack?

  15. #15
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    Hey!

    Just go for the carbon fiber sleeve solution. Heat treating an aluminum frame, is not simple (you’ve got to follow a very specific heat / time curve)…

    Also,
    your welder have to attach this frame on a jig, in order to avoid distortion.

    CF is easy. I will describe you a “very amateurish” procedure, that you will actually enjoy

    - Take off the wheels, drive train disk, saddle etc. Leave on the seat post (for added rigidity). If possible strip the suspension arm too.
    - Place the bike somewhere you can work on it (a bike stand will be ideal).
    -Cover the rest of the bike with masking tape and plastic film. Add some carton box sheets on the floor. You may want to mask the bike stand too!
    -Mask the area you are going to work. Expand more than the crack of the frame on both tubes...
    -Strip the paint with a wire brush (please do wear eye protection and gloves).

    Now you are ready for the fun part.

    -Cover the raw aluminum using the aluminum etching kit (west epoxy) or one of those (usually green) epoxy primers, like the NUBIAN.
    -Work several layers of CF (I prefer the unidirectional). DON’T place all layers on one session! Use the wet method with a paintbrush and some high quality epoxy (I have used West Epoxy Systems very successfully).
    -For added safety I would add a layer of unidirectional Kevlar.
    -Press every layer with electric tape (sticky side up), by wrapping it tightly over each layer. Open holes on the tape after wrapping with an awl. The tape will look like perspiring!
    -Wait between layers for curing.
    -Sand lightly (wear safety glasses & a mask) before the next layer. You may smooth any irregularities here.
    -Wipe with acetone.
    -Repeat as many layers as you want (given the fact that a “layer” is more than one layer, but actually a stage on covering, you may only need 3 repetitions. A CF one, a Kevlar one and a final CF.
    -For showing off purposes you may finish with a final thin layer of woven CF of your choice.
    -Sand very lightly and paint a layer of epoxy
    -Varnish it.

    After a few days (if you live in a warm place this sleeve will be surprisingly strong (and nice to look at!)

    A note.
    If, at the stage of brushing off the powder coating paint, some of it penetrates the crack, live it there!

    John
    For the pressing with electrical tape method got to:

    https://www.sheldonbrown.com/rinard/carbon_fiber.htm

    Good luck, enjoy the procedure!

    UncaJohn

  16. #16
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    wow, ok, I will have a read in detail in a bit and consider, I hadn't thought this path was that viable really until now I suppose. thanks for the input.
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    I definitely wouldn't be adding that gusset. Any strength that it may have added will be negated by all the heat you've put into the tube. You'll end up with a far far bigger part of 2 tubes that have now no longer got the correct heat treatment.

    Just weld the crack and Bob's your Uncle!!!

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    Quote Originally Posted by Cord View Post
    I definitely wouldn't be adding that gusset. Any strength that it may have added will be negated by all the heat you've put into the tube. You'll end up with a far far bigger part of 2 tubes that have now no longer got the correct heat treatment.

    Just weld the crack and Bob's your Uncle!!!
    Nah. There’s 2 mechanisms that cause cracking. One, is where the yield strength, then ultimate tensile strength of the material is exceeded, & the material cracks/fails. There’s visible bending of the parts.
    Two, work hardening, where small bending/flexing cyclic loading is concentrated into a small area, this causes work hardening & brittleness, the material will then fail at a much lower load than the yield/ultimate tensile strength. That’s what has happened here. What you need to do, is spread the load/movement over a larger area, to prevent stress concentration in a small area. I worked in Aluminium design and fabrication quite a few years back, we welded T-6 Aluminium all the time without post weld heat treatment, (I designed, wrote & had the welding procedures qualified) & as long as the design was right, it was very successful.
    Yes, ideally the repair should be annealed & then heat treated in a perfect world, but we’re looking for a quick, cheap stopgap solution.

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    Quote Originally Posted by uncajohn View Post

    Also,
    your welder have to attach this frame on a jig, in order to avoid distortion.
    Nah. The frame is already 99% welded. Builders remove the frame from the jig for final welding anyway. If you use balanced/good welding techniques, distortion will be minimal to inconsequential.

  20. #20
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    Quote Originally Posted by speedygz View Post
    What you need to do, is spread the load/movement over a larger area, to prevent stress concentration in a small area.
    Your gusset design does neither.

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    Quote Originally Posted by dr.welby View Post
    Your gusset design does neither.
    It actually does. The frame looks to be an old school design, with a very short seat tube extension above the top tube. And a shorter seat post. Not like the more modern designs, with longer seat tubes extending above the to tube. Which is why you see the gussets above the to tube on those designs. Yes, the gussets will be stronger in tension, but I don't think that's what we're looking to achieve here.

  22. #22
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    Quote Originally Posted by speedygz View Post
    Two, work hardening, where small bending/flexing cyclic loading is concentrated into a small area, this causes work hardening & brittleness, the material will then fail at a much lower load than the yield/ultimate tensile strength.
    Work hardening isn't a failure mode either.

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    Quote Originally Posted by dr.welby View Post
    Work hardening isn't a failure mode either.
    Sigh. It is the major contributing factor.

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    Quote Originally Posted by speedygz View Post
    Sigh. It is the major contributing factor.
    It's a fatigue failure.

    Work hardening is "the strengthening of a metal or polymer by plastic deformation."

    There is no plastic deformation at the weld.

  25. #25
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    Notice that the weld did not crack, but the metal next to it cracked. That is pretty common for aluminum frames. That is what heat treating should prevent. Maybe this bike was not HT properly. It should not cost that much to fix it. Use a wire brush on a drill to remove all of the paint back 1" from the repair, make one small gusset, have it welded. If it cracks again, buy a new bike. If you do all of the prep work, and make the gusset, it will keep the welding cost down.
    It's all about the machine. The design, and what makes it go fast.

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