Alternator welder with a twist, 6 HP lawn mower motor. will it work?

[BrettM]

I have a perfectly good 6 HP lawnmower motor just lying around begging to be put to use for a go-cart or something, when it struck me that I could make a portable arc-welder real easy doing the good old alternator welder thing.

All the real tech is already out there for getting the right alternator and hooking all that up, I'd really just need to build a frame to hold the motor and alternator appropriately and figure out the right size pullys (or direct drive even? )

So I guess my only question is do you think it will work? Will the 6 HP motor have enough power? I'd be looking to do 1/4" steel in a single pass.

thanks
brett

[Urban Wheeler]

Originally Posted by BrettM

So I guess my only question is do you think it will work? Will the 6 HP motor have enough power? I'd be looking to do 1/4" steel in a single pass.

thanks
brett

Doubtful. Read this thread then poke around in this forum

[braxton357]

Originally Posted by Urban Wheeler

Doubtful. Read this thread then poke around in this forum

Yeah, but grant was using a MIG welder and pulling 300 amps with an electric 5 hp motor. I say that you could easily (esp with the right pulleys) make an arc welder that will melt 1/4.

[fj40guy]

Originally Posted by BrettM

I have a perfectly good 6 HP lawnmower motor just lying around begging to be put to use for a go-cart or something, when it struck me that I could make a portable arc-welder real easy doing the good old alternator welder thing.

Brett,

Quick Sanity Check.... 1 hp = 746 Watts. That is in a "perfect world" with no losses (i.e. you'll never get there). So if you even get 70% power from that engine, you're talking about 6hp * 746 W/ 0.70 = 3000 Watts.

Those little welders (120V) need around 20 Amps at full pass to get a decent 1/8" plate welded up... About 2400 Watts.

So welding 1/4" steel plate will be a bit of a trick, but you could probably get it to run 3/16" rod for short periods of time.

Still if you aim to be able to weld 1/8" plate. Spin the alternator at 3x the engine (look under your hood to get an idea of how fast those alternators spin... measure the crank pulley, divide by alternator pulley) to get an idea.

Lots of stuff you can "learn by doing".

OK... I cheated, I have a ZENA unit with a mil-spec 4 cylinder. There is enough power to weld 1/4" AND run an air compressor. Air Compressor is 2 cylinders of a Honda 4 cyl (I'm a cheap bastard, engine spun a rod bearing and was bought for $20 scrap!).

Yep, next challange was a portable plasma unit. Never got that far.

Tom

[BrettM]

so I might be able to weld 3/16" at best? I guess I'll make a go-cart

[beyondhelp]

Well, this thread has me thinking... I have a mercruiser 3.0 (straight 4 gm style motor) that came out of my boat and I'll bet I could set that up to make a sweet welder/compressor/?? rig. It sits on nice flat mounts that make it look like it was meant to be used that way. Just need a carb and a closed cooling system...

Pic:

[Urban Wheeler]

Originally Posted by beyondhelp

Well, this thread has me thinking... I have a mercruiser 3.0 (straight 4 gm style motor) that came out of my boat and I'll bet I could set that up to make a sweet welder/compressor/?? rig. It sits on nice flat mounts that make it look like it was meant to be used that way. Just need a carb and a closed cooling system...

My dad has a boat with that same motor.... IIRC his boat has two water pumps. One to suck water in, and one to ciculate water around the motor. (If that makes sense.)

Braxton, he did say arc welder, but he didn't say mig or stick. I just figured amps are amps. Also, if Grant can stall 2 five horse electric motors, I don't think a 6 horse gas would do any better. As the rpms go down, torque decreases and then the motor quits. Electric motors have peak torque at zero rpm.
edit (from the first link I posted)
So I bought a 300A (continous) 28v alternator last year and did some stick welding with it. Stalls my two 5HP motors at about 333A. The nice thing about a rotary CC/CV power supply is that they are pretty efficient. A single phase 300A stick welder draws nearly 100A, mine draws 52, but its real noisy.
And then...
Well, it didn't last too long. I only had one of the 5HP motors hooked to the alternator. The top motor is as of now dead. So much for the stupid heat/current breaker built into the motor. the motor was NOT running on the start windings and none of the wires are melted (pulled the back off)....... I averaged 250A on a comfortable hot spray. I then got angry and turned up the wire speed. I sustained 300A, then my hand started to burn through the cotton glove so I stopped.


So I don't know. You might be right.

[braxton357]

I was just hoping that he'd try it and get back to us on how it worked...

[cavstoy]

a few capacitors in line will start the arc and prevent the motor stalling.

[AIRZUKI]

I have exactly the thing you want to make... it was a product of the Scott welder company.. it is basically a modified Delco alternator running in feedback through a Zener diode to the rotor.. the trigger comes off of the magneto of the motor...(mine currently has a 5 HP Kawasaki industrial engine on it but the unit used to have a 9HP Briggs... As stated before it will burn 3/16 okay... welding thicker you need to do in short bursts.

If I recall it uses the regular alternator pulley and around a six inch pulley on the motor (overdrive)...

[ScoutIITD]

8 hp

http://oak.cats.ohiou.edu/%7Eweinfurt/gaswelder.html

[TLCObsession]

Originally Posted by AIRZUKI

I have exactly the thing you want to make... it was a product of the Scott welder company.. it is basically a modified Delco alternator running in feedback through a Zener diode to the rotor.. the trigger comes off of the magneto of the motor...(mine currently has a 5 HP Kawasaki industrial engine on it but the unit used to have a 9HP Briggs... As stated before it will burn 3/16 okay... welding thicker you need to do in short bursts.

If I recall it uses the regular alternator pulley and around a six inch pulley on the motor (overdrive)...

I have seen this little sucker in action (a few years ago on the island) - very handy ... IIRC it is about the size of a small generator (Milkcrate sized). Very cool.

Jim

[horse_with_no_name]

do a search for zena welders, and good luck to you, a little redneck engineering and you 'll be welding like welderboy!

[doctor_cad]

I have rigged up an alternator welder using an old "Link Arc" belt driven unit. The engine is an older Kohler 8HP one lunger. It welds really well, and has 100% duty cycle up to about 140 Amps DC.

The unit is really cool because it uses secondary windings to 'self-excite' the alternator. That means you dont need a battery to provide field current and keep it running... Just spin 'er up and she starts to put out power! I suspect you could modify a large case delco to do the same thing, with a bit of creativity.

We built the frame from 3/4" plywood and 2x4s. Pretty simple design. Check out this sketch, I will post pics when I get home.

edit: I was looking at the case on the alternator unit, it is manufactured by Scott Industries... Pbly the same unit as the one Airzuki us talking about, but this one doesnt use the engine as a trigger, it self excites.

[BrettM]

well, I guess I'll have to try it then

[doctor_cad]

Definitely try it. Cheaper than a buzz box, and you take it in the bush. Heres another pic: