# minimum setup for brazing?



## etischer (Jun 16, 2008)

I don't know that i would trust brazing, I think it would crack over time. Are you talking about using brass? 

Maybe you could mig weld, spot weld, or rivenut it in place? You'd have to get your floor pan orange hot, and super clean to braze it properly, not sure that is feasible without burning the car down =) A hand held torch with map gas won't cut it, I dont think the brass would wick into the material anyways. It won't be strong unless you have alot of surface area.






dtbaker said:


> considering methods to fasten my rear battery rack to floorpan in areas where I cannot get to both sides (like into the 'tube' bulkheads)... would brazing be preferable to sheet metal screws?
> 
> if so, what would be the minimum cost brazing equipment that would do a decent job? can I get by with a little handheld MAP gas cylinder and tip and some brazing rod? Do I need other stuff?


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## ElectriCar (Jun 15, 2008)

I second the not trusting brazing. However all you need is the rods and a torch kit. Not sure but you may could use a bottle torch using Mapp gas. You can pick one up at Home Depot probably. Mapp gas is in a yellow bottle, propane is blue. Mapp gas is MUCH hotter than propane thus the gas of choice for plumbers.

Option 2 is an acetylene torch set. WAY more expensive than the above but you can use it for cutting, welding, brazing, heating and such. It's very versatile, especially on bolts and nuts that just won't budge. In that case it's called the "acetylene wrench"!


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## Coley (Jul 26, 2007)

You could use "pop" rivets but I would use small lag screws and then if you need to change something, it will be a lot easier.

Brazing is possible with the Mapp gas, but there again, if changes are needed.... and they usually are!


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## DIYguy (Sep 18, 2008)

The others are right on this... brazing does not melt the base metal .. it is not welding. It joins by capilliary attraction. It may fail in service. For brazing, you need an oxy-acetylene torch and tanks to do a decent job. 

I can't imagine a spot that you have access to do brazing and not be able to do SMAW (stick welding). Joints don't always need to be welded on both sides to have adequate strength. There are ways to prepare the joints to get more weld in the joint also, like cutting a "v" in the joint line to give more linear weld length. Slot and puddle welds increase joint strenth when added to lap joints, also if you are worried. Drill a hole in the surface member large enought to get the rod into and start at the bottom and fill it up in a circular motion. Use a 70 KSI rod also, like 7018, this is an all position rod and will give you a higher tensile strength than a 60 series like 6011. If you only have an AC welder, there are 7018AC rods made to run better with this type of machine. Otherwise, DC and away you go. 3/32 dia. rods will likely be best for the stuff you are working with. 

Regards,
Gary


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## dtbaker (Jan 5, 2008)

DIYguy said:


> The others are right on this... brazing does not melt the base metal .. I can't imagine a spot that you have access to do brazing and not be able to do SMAW (stick welding).


thats the reason I was considering brazing for this application. The floorpan metal is REALLY thin stuff. Even if I turn my stick welder amps down, as soon as an arc starts it melts a hole right in the floorpan. Its really hard to weld a 1/8 thick rack edge to a .020 thick sheet as far as I am concerned.... I am using 3/32 dia 6013 rods, and tried amps at different settings, and it seems that any arc at all just blows right thru the floorpan.

but... it is sounding like brazing may not be better than bolts/screws. I have several corners I can extend to be above 'bulkheads'. Still not easily weldable because they are so thin.

still pondering.....


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## DIYguy (Sep 18, 2008)

dtbaker said:


> thats the reason I was considering brazing for this application. The floorpan metal is REALLY thin stuff. Even if I turn my stick welder amps down, as soon as an arc starts it melts a hole right in the floorpan. Its really hard to weld a 1/8 thick rack edge to a .020 thick sheet as far as I am concerned.... I am using 3/32 dia 6013 rods, and tried amps at different settings, and it seems that any arc at all just blows right thru the floorpan.
> 
> but... it is sounding like brazing may not be better than bolts/screws. I have several corners I can extend to be above 'bulkheads'. Still not easily weldable because they are so thin.
> 
> still pondering.....


Ah, ok, now I understand. For sure, you will have issues with 3/32 rods on sheet metal! I was envisioning welding to a truck frame... (my conversion) 
Is your welder AC, DC or both? If you have DC, you could get a GTAW (TIG) torch, mild steel filler metal rod and a small Argon bottle. This would be the best way to do it, if you want to weld it. You can use the same filler rod with an oxy-acetylene torch also... but the heat is not as high density and controllable as TIG, might not be the best idea, depending on your skill and ability.
Small diameter GMAW (MIG) with .020 or .025" wire (body shop application) would also work ok.
Failing these options, you could use your stick welder and get some 1/16 rod and turn the current down to about 55 amps or so. It will still be tough to do a good job. 
The problem with unibody structures is to attach in only a few places and get enough strength for carrying something heavy like batteries. You need many attachment points to make it solid and reliable. Can you run a piece of angle along a underbody flange and attach in several places? Floor pan attachment makes me nervous.

G


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## dtbaker (Jan 5, 2008)

DIYguy said:


> Ah, ok, now I understand. For sure, you will have issues with 3/32 rods on sheet metal! ...
> Is your welder AC, DC or both? ...
> Small diameter GMAW (MIG) with .020 or .025" wire (body shop application) would also work ok.
> ...
> ...


Now you've got the picture. 

The whole front edge is flat and straight and right over a unibody bulkhead; great support there. There is another bulkhead supporting the rear suspension just a few inches behind the rearmost rail. I will probably extend the rails 'over' and drop down to flat 'feet' a couple inches square that I can bolt thru to the bulkhead. The sides are not quite a handy, but there is a bulkhead over closer to the sides of the car.....

At this point; how about some good ideas on the best hardware in the spots I can't get to both sides for bolts/nuts/washers? Are there any expansion bolt type things that would give me a good bite inside these bulkheads? I am looking for some way to get more square inches rather than threads in sheet metal that would tear out in an accident...

pictures at 
http://envirokarma.org/ev/gallery/081221_battrr01.vertsin.htm


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## DIYguy (Sep 18, 2008)

dtbaker said:


> At this point; how about some good ideas on the best hardware in the spots I can't get to both sides for bolts/nuts/washers? Are there any expansion bolt type things that would give me a good bite inside these bulkheads? I am looking for some way to get more square inches rather than threads in sheet metal that would tear out in an accident...


Probably rivnuts are you best option for a fastener I would say. They are like a heavy duty rivet.


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## dtbaker (Jan 5, 2008)

cool... Hopefully I can find them local and not have to order and wait! Sounds way less expensive than buying a MIG welder just for this job.... although it might be a great excuse. 

I just turned up one other thing... apparently a special deal I can add to my arc welder for thin stock.... anybody ever try one of these?

http://www.jcwhitney.com/autoparts/...tk-AllTextSearchGroup?Ntt=welder#BVQAWidgetID


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