attaching aluminum alloy to steel... how to?

overdraft

overdraft

Coast to Coast
my feeble brain is telling me that you can't weld these two materials together... solder? silver solder? braze? some kinda glue? doesn't need to be crazy strong, but does need to be fluid tight... i'm trying to attach an alloy fitting to a gas tank, so to add to the fun the steel is thin guage... any thought? thanks!
 
Compression fitting with o-rings ether side? I don't know any glues off hand that can withstand gas and vibrations but I haven't checked the superglue isle in the parts store lately. You have to use that fitting, what are ya doing with it?
 
Silver solder will be plenty strong enough to connect the AL with the steel. Just make sure you put plenty on there, you can always grind it down smooth AFTER you make sure you have plenty of meat. If possible, I'd drill and tap the hole in the tank also, just for safe measure against vibration.
 
silver solder won't bond to aluminum, that needs a tin based solder, and I have a feeling you'll have problems with the joint due to the vastly different properties of each metal. the only reliable way to join those two would be mechanical, like rivets or bolts
 
Might help to know what we're talking about - what sort of fitting? Something for a petcock?
 
rockcitycafe said:
silver solder won't bond to aluminum, that needs a tin based solder, and I have a feeling you'll have problems with the joint due to the vastly different properties of each metal. the only reliable way to join those two would be mechanical, like rivets or bolts
Click to expand...

I was unaware of this, and I stand corrected.. :eek:
 
rockcitycafe said:
silver solder won't bond to aluminum, that needs a tin based solder, and I have a feeling you'll have problems with the joint due to the vastly different properties of each metal. the only reliable way to join those two would be mechanical, like rivets or bolts
Click to expand...

Agreed

Edit: FiberGlass maybe...?
 
find a way to weld a steel bung onto tank that has threads which can then thread on your filler cap?

have some pics of what your working with?
 
also im pretty sure bronze solder should work... its used on both steel and alloy framed bicycles if im not mistaken.
 
There isn't a welding process precise enough for welding aluminum besides TIG, because the actual metal melts before the oxides. Basically what I'm saying is the inside melts before the outside, making it terribly difficult to get any kind of bead or flow going. You can weld aluminum with a small Oxy/Acetylene torch, but its not going to be pretty whatsoever, and your metal needs to be extremely clean.

You will have to weld a bung like Rocan said, or tap the tank and fitting to thread together. But remember, aluminum and steel together can create galvanic action after quite some time. Theres no way you can get this fitting in steel?
 
what exactly type of cap are you having?? most alloy caps that I've had the pleasure of dealing with are threaded, maybe the solution is having a steel bung made and threaded?
 
Yeah, are you talking about a flip-top Monza style cap with a threaded mount? Like this:

62209003.jpg


I have one on my alloy tank, but it's not even threaded on. The guy who made the tank just flared out the filler hole and used some sort of epoxy to mount the cap in place. My previous alloy tank had a proper threaded bung, which as mentioned, could be any material at all.

Let's see some pics of the cap and tank.
 
Tim said:
Yeah, are you talking about a flip-top Monza style cap with a threaded mount? Like this:

62209003.jpg


I have one on my alloy tank, but it's not even threaded on. The guy who made the tank just flared out the filler hole and used some sort of epoxy to mount the cap in place. My previous alloy tank had a proper threaded bung, which as mentioned, could be any material at all.

Let's see some pics of the cap and tank.
Click to expand...
you got it! i was just gonna post the pic and describe what's going on... so on mine it will be a close fit between the neck of the tank and the bottom ring of the cap (based on internet voodoo and measuring... may not be close at all when it gets here!) so i wouldn't need to flare the filler hole, just glue it in place as you describe maybe? i'm a boat guy so i'd use cold cure because it has some flex as compared to say, polyester so that might help with differing expansion rates? but i would think there would maybe be a real product... or could i just use tin solder?
 
do it right. the way i said to do it. thread it on man.

as for the thing sealing in place, shouldnt be that big of an issue as you wont really have to take it off again. and if you DO want to keep it free, just put some copper anti-sieze on it.
 
If you can, ideally you'd want to weld on the matching threaded bung and then just screw the cap into place. That's the right way to do it. Buy a steel bung that matches the threads of the alloy cap, weld the bung to your tank, and you're all done.
 
Rocan said:
do it right. the way i said to do it. thread it on man.
Click to expand...
Tim said:
If you can, ideally you'd want to weld on the matching threaded bung and then just screw the cap into place. That's the right way to do it. Buy a steel bung that matches the threads of the alloy cap, weld the bung to your tank, and you're all done.
Click to expand...
ah yes...spoken like people with welding rigs! lol! here's how this looks to a suburban garage builder like me...
"that'll be our minimum shop charge buddy... $125"
"ouch! well, i guess i gotta bend over for ya..."
three weeks later
"oh, that little job? ya sorry, we had a bunch of commercial jobs come in... i'll have it done for you next week"
three more weeks later
"ya sorry buddy, the metal on that New Old Stock tank that you spend a hundred hours finding and spent way too much for because it was perfect? ya, the metal was thinner than we figured so we burnt through in a couple of places. we've tacked them up for you but you'll have to put on some bondo so i'm only gonna charge you $100"
the very next day on DoTheTon.com
"permatex makes this metal adhesive called AllTankFix that bonds to everything! it's only $4.95 at cambodian tire! I used it to do that exact job you're describing"
"fml"
 
lol... I think you'd probably want to find a small machine shop to do the work, if you get a piece of steel pipe that's a little larger than the threads, you can bring it to a machinist who can thread it and cut the rest down for welding with you there. It shouldn't be more than a half hour job if he doesn't have anything else set up on the lathe. Bring some cashes and snacks, machinists like those... Hell, I'd do it for cashes and snacks ;D
 
Tim said:
Yeah, are you talking about a flip-top Monza style cap with a threaded mount? Like this:

I have one on my alloy tank, but it's not even threaded on. The guy who made the tank just flared out the filler hole and used some sort of epoxy to mount the cap in place. My previous alloy tank had a proper threaded bung, which as mentioned, could be any material at all.

Let's see some pics of the cap and tank.
Click to expand...

you mean the great evan wilcox doesn't include threaded bungs and glued the gas cap on???
 
rockcitycafe said:
you mean the great evan wilcox doesn't include threaded bungs and glued the gas cap on???
Click to expand...

No - the great Evan Wilcox may form metal like it's silly putty, but the lack of baffles in the tank and epoxied on filler cap tell me he knows nothing about motorcycling.


Roc City Cycle FTW! You're gonna make me a tank for my SR500 :)


www.roccitycafe.com
 
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