Low cost homemade welder for building a hot rod frame.

Low cost homemade welder for building a hot rod frame.​

　
I'm making a late '50's style front engine dragster with a model T body for the street. No one makes a frame for such a rare combonation, so I'll have to weld one up myself. I don’t weld for a living, so I don't want to spend a lot of money on a welder. Yet, I want good strong welds that I never have to worry about or question. Can it be done? I think so.

I hope to refine a very old and proven idea - a homemade welder made out of car batteries. There is some evidence that car batteries were used for welding way back in the '50's. It was rather primitive though, without much control over the electricity or ability to recharge the batteries very easily. I hope to be able to fine tune the welding current and automatically recharge the batteries using safe, very inexpensive parts.

In order to get the voltage needed, three batteries will be used. Most hot rod cars already contain an alternator and one battery mounted to a power source (the engine). They will stay in the HAMB friendly car, and the rest of the welder will simply hook up to it like jumper cables. Through the magic of relays, the alternator should be able to charge all three batteries between welds (see the schematic). One man should be able to lift the welder to throw it in a trunk to go anywhere (because it only has two batteries).

I'm not a professional, so don't sue anyone if anything bad happens because of this post. I'm experimenting, not giving any advice. Hopefully, someone else on the HAMB can use the information - if nothing else, for entertainment.

If you can find any improvements, flaws or safety issues, please chime in. I'm all ears!

This is a really long post.

Will it work?
As long as the end of welding rod "sees" the electricity that it needs, it doesn't care where it comes from or how much I spent on it. It needs about 40 volts DC and about 150 amps. If we can deliver that to the end of the welding rod, it will penetrate and weld 5/16 inch steel. It can’t help it. It has to.

Voltage:
3 batteries x 12volts each = 36 volts. That’s 10% short of the ideal 40 volts. The lower voltage will only make it a little harder to hold an arc. I’ll adapt my technique by holding the rod 10% closer to the work - no big deal.

Amperage:
I took a look at the battery in my friend's little 4 cylinder Nash Metropolitan. It’s rated at 460 amps. That’s a bit much, even though it’s a small battery in a small car. It would have to be reduced to weld anything thinner than ¼ inch plate. Your hot rod with a big engine should have even more amperage than that. Some wire wrapped around a Bakelite cylinder with a selector arm should make a simple, cheap and effective amp controller.

It seems very promising that HAMB friendly car batteries are capable of producing more power than needed. I’ll have to actually try it out to see what the duty cycle is. It should depend on the alternator, the speed the batteries can recharge, how much heat is produced , and whether or not it can be dissipated fast enough.

Is it feasible?
For many people, the time investment is better spent earning money to buy a welder rather than making one. I understand that. That’s cool. This probably doesn't make much sense to you. But for some of us it makes a lot of sense.

I already have most of the stuff laying around the garage. I think I can scrounge most of the rest for cheap. Old central air conditioning relays can be bought by the pound at a local scrap metal yard. You could scrounge more traditional relays from some old industrial equipment from the '30's, '40's, '50's or early '60's. Old batteries can be purchased cheaply at salvage yards. (I already have one extra laying around the garage.) I’m going to have some fun building this thing just to see how close to free I can get it. I’ll make a bill of materials so we can keep score.

A simple, sturdy wooden shelf to hold the batteries and wiring together would be handy and cheap. A removable tray on top for welding and grinding supplies would also be nice to have (but not essential) (see picture). Everything could be stored together in a corner of the garage and scooped up with an antique two wheel dolly when needed. Or, wheels and a handle could easily be attached.


Advantages:
It’s inexpensive. It doesn't need a costly 220V plug in the garage. It’s as portable as a HAMB friendly car. In a pinch, it could still be used without the traditionally styled car at a reduced capacity. It’s very powerful. It’s a D/C welder instead of an A/C. It can be used as a heavy-duty jump starter for most pre-1962 vehicles.

Disadvantages:
The batteries will not last as long as a typical welder transformer does. It can’t be used it indoors because of the explosive gas that batteries produce when they are being charged. A running hot rod or custom has to be present, so that makes it difficult to take up elevators.


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Caution:
Do not weld on the same car that is charging the welder!

The ground cable on a DC welder is normally positive. The car’s ground is normally negative. It will short everything out if it touches anything metal on the car that is charging it.

If your car has a positive ground or is only 6 volts, do not use this welder. It will short out.

Make sure your work isn't touching the charge car or it will short out. It’s OK to weld on another car, regardless of its wiring, so long as it’s not touching the charge car and/or is not electrically connected to it (such as with a jumper cable or by both cars touching the same fence).

Never use the welder anywhere that the explosive gas can become concentrated.
　
Hooking it up to the traditionally styled car:
1. Make sure the weld button on the welding rod holder isn’t being pushed.
2. Hook the welder up to your battery like you would jumper cables. Simple.
　
Operation:
1. Select the amperage desired using the wire wound resister dial.
2. Hold down the weld button on the side of the welding rod holder.
3. Strike an arc.
4. Let up on the button between arcs to charge the batteries.

Schematic:
Here’s a schematic I came up with. I’ve been over it a dozen times and can’t find any more silly mistakes. Maybe one of you can improve on it or find some flaw I’ve missed.

Basically, there are 3 circuits.
1. The welding circuit is in Andalucite Blue.
2. The charging circuit is in pre '62 Chevy Orange.
3. The switching circuit is in Cumberland Green. It’s job is to switch between weld mode and charge mode. It will either charge the batteries or weld, but it won’t do both at once.

How it works:
The welding and charging circuits are pretty self explanatory.

Weld:
The relays hook all three batteries up in series with the work. That makes them produce 36 volts. The alternator is disconnected from all but one of the batteries - the one in the car. The circuit sees the alternator and car battery as one big 12 volt battery in series with the other 2.

The variable resistor limits the current. It is a simple wire wound around a tube with a selector arm. The longer the wire is, the more resistance it has. The selector arm selects its length, therefore, it selects the current. (Careful, the wire can get red hot!)

Charge:
When the weld button is released between welds, the relays disconnect the work and hook all three batteries up in parallel. That makes all of them act like one large 12 volt battery. They are now the correct voltage for the 12 volt alternator to charge.

Switching:
The switching circuit is a little more complicated.
I’m using 2 central air conditioner relays. Their coils take 24 volts to energize. I already had two very small 12 volt sealed lead acid batteries left over from a former project.

The electricity comes out of the negative side of the small relay batteries, travels up the thin green wire, takes a right onto the welding cable (It can’t go to the left.) and waits for the weld button to be pushed before it can go any further.

Once the button is pressed, it allows the electricity to pass down the green wires, through the relay coils and back to the positive side of the small relay batteries. Once the relay coils are energized, they switch the welder into "weld mode."

Recharging the small relay coil batteries:
After the weld button is pushed but before an arc has been struck, the relays are all switched to weld mode. That puts all the large batteries in series, giving us 36 volts across all 3. We can tap 24 volts from between two of them to recharge the small relay batteries.

The diodes are hidden inside old vacuum tubes so they will be on topic for the HAMB and my post won't get deleted again. They act like one way valves for electricity. Electricity can only flow through the diode in one direction (indicated by the arrows). They keep the small batteries from discharging when the welder is in charge mode, when the rod sticks to the work or when the big batteries run low.

Explosive Gasses:
Lead acid batteries produces an explosive gas when they are charging. Most HAMB'erific cars deal with this by having a lot of air circulating around the battery. The air dilutes the gas enough so that it can’t ignite under normal operating conditions.

I plan on setting the welder in front of a hot rod or ckustom car's fan intake. The back of the shelf is open so air can pass through them and around the batteries. That should dissipate any gasses so they will be too diluted with air to detonate. Also, it’ll help cool them a little.

Never use the welder anywhere that the explosive gas can become concentrated.
Welding produces sparks that fly away at all angles. Charging batteries produce explosive gas. Keep the two away from each other, either by distance or some sort of barrier or shield.
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My last homemade welder post was deemed, "off topic" by the moderators and got deleted. So I threw some HAMBish verbage in here to illustrate how we all might benefit from an inexpensive welder. Then it got late and I got a little silly and went overboard with it. I hope the general concept comes through and it passes this time.

I believe there will be some HAMB'ers who could use an inexpensive, safe, powerful welder. It would allow them to spend more money on hot rod or ckustom parts for pre 1962 vehicles or perhaps even spend that saved money on an alliance membership to the HAMB.

 

Exactly what I was thinking......

 

whiskey tango foxtrot

 

I have no idea how feasible this design is, or what kind of welds it might produce, and I won't even express an opinion at this point, but I just saw an episode of "STUCK WITH HACKETT" on cable (the guy is nutz! But way smart...), and the dude welded some stuff together with car batteries in pretty much the same configuration-it worked! No joke!

EW

 

Originally Posted by Big Bad Dad, "EEK!"

I expected some simple statements like, "It won’t work." or "You’re a dumb ass." While those may be true, they are entirely useless unless you explain WHY.
For instance, "The welding cable ground is positive and the car’s ground is negative. You’ll short everything out and burn your car up if you try to weld on it, dumb ass!"

Now that’s useful! (You don’t have to call me, "dumb ass" if you don‘t want to, though. )


What makes you go, "EEK!"?

Is it scary because it's homemade? Makes gas? Might shock you?

Please elaborate.

 

Cool idea if it works, MacGyver would be jealous.

 

Let's see.

Three cheap car batteries, $40 or so each with the core charge. Used at the junkyard, $15 each with a core charge.

Cables, clamps, etc. ... $??? I suppose you could use a $10 set of cheap jumper cables here.

Risk of loss of life and limb through afro-engineered home made welding apparatus, and potential failure of said welding - priceless.


Or, you can go buy a cheap stick welder to make the frame with. Watch Craigslist, I bet you can get a working used 110V welder for under $100. I know I have an old one here I bought years ago and it was under $100 brand new, I'd be shocked if you can't get the same kind of thing brand new from Harbor Freight for a similar price. Since you're making a frame, and not a body, you don't need the ability of a wire feed welder. Of course, those can be had pretty damned cheap too.

And, there are professional welders who could easily put together your frame as well, if you're unwilling to spend $100 or so on the right tool for the job and don't really know what you're doing anyways, perhaps you should farm the work out to someone who does so that when you drive the car down the street it doesn't break in half from a crappy welding job, and kill you and who knows who else.

 

Let me guess, you haven't bought a battery in the past several months to a year......

Here as of late, most batteries are $75 or more plus a core charge...

You're right, a used stick welder (or even a cheap ass new one) would be cheaper.

 

i've seen good used stick welders go at house/shop auctions for $45 bucks. dont screw around now.

 

while I think it may be an interesting experiment, is your frame where you really want to test it out??? if you are bent on trying a homemade welder then I'd make the misses some lovely yard art.

 

i have to agree, a car chassis isn't where you experiment or learn to weld...

 

Last new one I bought was... a while ago, yes.

I mean, the idea is nice if I'm stuck on the side of the road in an emergency or something, but for a car frame I want to be able to set the thing up to get the correct penetration so the weld is a good one.

 

Offroaders do this in a pinch with only one battery and jumper cables. I'd buy a used buzzbox though.

 

In the right hands, I'd hazzard a guess that this rig could be made well enough to work and probably be safe. But, as there are no UL listings on home-built rigs like this, I can only imagine what might happen in inexperienced hands. So let the builder and user beware, as you can't sue yourself, eh? Gary

 

It works.
as stated earlier its an old trick used by 4x4 enthusiasts in a desperate pinch to get them off the trail.
You don't need all the relay mumbo jumbo either.

If I were out by the treeline and lost a spring perch, I'd take my battery from the vehicle and another battery out of my buddies 4x4 and use two sets of booster cables along with some 3/32 multipurpose rods and have at it.
No battery would remain inside the vehicle as if you stick the rod you run a risk of burning off a lead terminal or even exploding a battery(s), with the resulting acid bath being bad for the vehicle finish...not to mention your eyes/body!

I WILL get home....and there I would remove my crappy looking welds and do the repair correctly with a real welder.

Your confusing what you Can do with what you SHOULD do.

You MIGHT pull it off...and thus make the naysays (like me) look foolish in your eyes...but really:
Its your frame.

It deserves better.

Now...if your building a Rat Rod.......

 

MacGyver just pooped himself...

 

When I was a kid (13) I saw this setup being used at the stock car races. It seemed to work good enough...

 

cold welds are the worst - i can't see that thing penetrating any size of steel much - but it's your @$$ if you don't get it right, not mine

 

Looks like fun (mad sicentist kind), but if saving money is the idea,go by a proper welder. It is not only the battries, wires, cables, ect, but the cost of gas burned to charge the unit. Not to mention the load (wear & tear )on your alt. This welder gets expensive fast if you burn up your alt.Or worse yet over heat your engine.
That being said, post it if you bild it. I love back yard eng.

 

No money is the mother of invention! Have at it, I had to.

 

it scares me just knowing that frame was not welded with a modern welder ! tech crew at the race track should be able to ask questions about HOW the frame was made, and how it was welded !its not only you're life thats in jeopardy , its everyone who lines up next to you ! after knowing that , i'll just watch from a safe distance !

 

Actually, if I remember correctly, MacGuyver DID do this! He welded together a broken connecting rod for an airplane engine with batteries, jumper cables and silver dollars as filler rod!
Don't think I'd be flying the friendly skies here!

 

Afro engineered, What the Fuck is that?? We're talking Cubin shit here my man. Get with it.

 

been a offroad trail fix for years but.....thats it. would NOT build anything with this setup!!