OT: not Proflex but 7000 series tubing repair question

[Happy Valley]

(I ran this by Terry and he seemed to think it would be okay to ask here)

My Proflex is running well at the moment but this problem is with a road bike I have:



Any thoughts whether and how this might be fixable would be greatly appreciated. The crack also runs down 4 0r 5 mm below and under the binder lug toward the pinch slot that can't be seen in the pic.
This is an older GT and it's really a great frame, one of my favorites, lightweight and the 7000 series tubing is rigid without a lot of flex. I'd hate to trash it. Thanks for any help.

BTW, the crack didn't happen from riding, it was on a roof rack and hit by a low flying aircraft. (actually it was a tree limb bashing the seat....but that would just sound dumb   )

[orange]

Well to be honest if you hadn't mentioned Terry already I would have asked him, he's the aluminium welding expert

[jeffhop]

cut it off just below the break then slot the front of the tube by drilling a small hole first then hacksaw down to the hole then fit a standard seatpost clamp, make sure there are no burrs left though. might work, worth a try anyway.

[shovelon]

Kinda Proflex related.   

Everyone needs a spare bike while the "precious" is getting that makeover.


Okay, 7005 is the aluminum considered the welder's helper, as  resists annealing during welding. That is the point of 7005, otherwise it would ALL be 6061. 6061 when fully heat treated is definately better, but at that higher cost.

So if it was mine, I would weld it.  Does ya know the seatpost diameter?

Terry

[Happy Valley]

cut it off just below the break then slot the front of the tube by drilling a small hole first then hacksaw down to the hole then fit a standard seatpost clamp, make sure there are no burrs left though. might work, worth a try anyway.

Thanks, I'd really just as soon a mechanical fix if it could be done. If I were to cut the seat tube below the crack I'd have maybe 16 or 17mm left on the front side (even less on the back side) above the top tube. Then there's taking into account the weld joining the top tube and seat tube. Scant little there to work with.

[Happy Valley]

So if it was mine, I would weld it.  Does ya know the seatpost diameter?
Terry

Yes, it's a 27.2mm seatpost. (1.07 in)

[jeffhop]

if it was mine i would cut it and slot it, you only need about 8-10mm of frame for the seat post clamp to sit on, you could also fit a deeper clamp if you wanted more security, with a 27.2mm post i would imagine its a 31.8mm clamp required. i would also fit a 400mm seatpost so youve got more post in your frame so theres less stress on the top.

[Happy Valley]

you only need about 8-10mm of frame for the seat post clamp to sit on

Really. I had thought I'd need more to get the tube to "pinch" and I wonder if it would have a tendency to pull away the weld where the ST joins the TT?

Well as I said I'd much prefer a mechanical fix that would work over welding only because I doubt finding anyone in my area (western mass) having the chops to do it right. There are welders and then there are bike welders, and even the latter being darn few I imagine who can successfully deal with aluminum.

Not like this guy anyway. 
http://idriders.com/proflex/smf/index.php?topic=2850.15

What are the chances this is either/or, cut or weld? By that I mean if I took a shot at getting it welded (and it didn't work) could that damage the tube to where cutting and slotting would no longer be an option?

[shovelon]

you only need about 8-10mm of frame for the seat post clamp to sit on

Really. I had thought I'd need more to get the tube to "pinch" and I wonder if it would have a tendency to pull away the weld where the ST joins the TT?

Well as I said I'd much prefer a mechanical fix that would work over welding only because I doubt finding anyone in my area (western mass) having the chops to do it right. There are welders and then there are bike welders, and even the latter being darn few I imagine who can successfully deal with aluminum.

Not like this guy anyway. 
http://idriders.com/proflex/smf/index.php?topic=2850.15

What are the chances this is either/or, cut or weld? By that I mean if I took a shot at getting it welded (and it didn't work) could that damage the tube to where cutting and slotting would no longer be an option?

So if you are really sure it is 7005, and you do the prep yourself, I think there would be little chance a weld guy in your area would wreck it. It is 6061 alloy that you have to weld really fast or it will detemper completely. Done just right 6061 will bounce back very well. It is the heat dwell time that kills it.

 I can send you the filler rod, which is 5356, and make sure they use it. Personally I would grind off the blocks like that guy in the other post, and use a clamp.

[Happy Valley]

So if you are really sure it is 7005, and you do the prep yourself, I think there would be little chance a weld guy in your area would wreck it.

Going by the frame sticker, says "7000 series aluminum-heated treated"

Could it be something other than 7005? I'll try to find any additional info tracking down what I can glean from the manufacturer.

Couple of last questions if I could:
Prep would entail removing paint, binder blocks.... anything else?
What might I want to explain to a welder about this job?

Thanks for your indulgence on this Terry, OT and all, maybe others will find it useful at some point I'll let you know how it turns out.

[shovelon]

Prep would entail removing the paint and grooving out the crack of any dirt and such, and the blocks if you desire. The idea is that the welder slaps the bike on his bench, attaches the ground clamp and drives in the weld. This should take less than 15 minutes and the charge should fall under the minimum charge, which in most cases is half an hour. My rate is $80 an hour, so my minimum is $40. I get guys bringing in greasy, crusty, plated, painted crap. It takes more time to prep it than actually doing the weld. I tell em, if ya can't eat off it, I can't weld it. You get the picture. If you have a steel tube or rod the same diameter as the seatpost, you could split it, and use as a backing for the weld penetration to rest against. Then smack it out and your seatpost should still fit with little fuss, or else you may have to drum sand it slightly.

To clean, I use a stainless steel wire brush same size as a toothbrush. I get mine from McMasterCarr.com. They are about $1.50 each. Scour the paint off then acetone the area. If the crack is not fresh, you might take a file to groove the crack, and brush some more. That's it.

7000 series weldments means 7005. There aint no other that I know of. The weld should probably take less than 10 seconds to weld the crack. No way the heat affected zone is gonna anneal before it cools again. The high strength 5356 filler is going to freeze and start strain hardening the area too. This is where the recommended oven stress relief comes in(typically the powdercoat sequence takes care of that). Or just let it sit for a week minimum for the stresses to dissipate on their own. There will be some slight aging taking place as well.

Let me know if you want some 5356 rod. About 8 inches should be enough, and I can pop it in the mail. It's got the alloy stamped on it. 

[Thunderchild]

HV,
2 Votes of confidence for Shovelon.  He has successfully repaired two of my bikes(7000 series aluminum).  You can find pictures of both in the forum and in my gallery.

Thunderchild

[jeffhop]

just give it to terry, he is after all the `master` ally welder on this site, wether he admits it or not  and if i ever get a frame in need of repair in the uk proflex or not im going to seek his advice first.

[shovelon]

Hey thanks Jeff.