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DIY Welder Project

JoeKultgen

Registered
Hi All,
It's been a while since I posted here. I didn't have the space or resources to tackle anything interesting and after a while I wasn't even lurking. It looks like that's about to change.

I moved to the Philippines a while back. In the coming year I'll be tackling a project that requires a substantial amount of welding on 4mm hot rolled mild steel plate. Running mains power to the work site just isn't in the budget. Neither is a new engine driven welder. Large portions of the country are, "off grid". There are *NO* inexpensive broken welders. When they break, they get repaired and/or sold to somebody who will fix them. Used machines sell at not much of a discount from new price.

I'm going to be stateside from Feb. through June of the coming year. Shipping a commercially built rig, or even the generator head off of one, back to the Philippines would drive the price higher than buying new locally. A home built welder head based on a heavy duty alternator should be under my economy shipping limit (50 lbs.) and labeling it "scrap auto parts" should get me under the minimum value for assessing import duties.

At this point I'm sort of pre-scrounging parts. I've got a 1 liter three cylinder including computer and wiring harness out of a Chevy Geo lined up as a power source for the trial and error phase. I've got a cheap Arduino programmable controller with four stepper motor modules. Since I'll be using the controller to regulate field current and engine speed, I'll probably be better off starting with a blown alternator. It would be nice if it had good bearings and winding's but I can fix that if I have to.

Does anyone have suggestions regarding the source for a core?
Any ideas on where I might scavenge heavy gauge magnet wire for a choke coil? Any (constructive) criticism?
 

Tracy T

Subscriber
Last Subscription Date
07/16/2019
I dont know, kinda a unique situation you have. How expensive are dc batterys over there? you may be better off using batteries to weld with and using a heavy duty truck alternator to keep them charged. I know around the mines they have used the batteries on a mining scoop and what ever part of the scoop that varies the speed to weld with. just dont think a alternator is going to hold up well welding for very long.
 

Heins

Subscriber
Last Subscription Date
01/02/2020
We had a DC generator rigged up to weld with years ago. It did a good job of welding but I was afraid it may harm someone if they got shocked by it. There was a thread on Smokstak about building a welder with a DC generator and they didn't think there was any danger. I think the DC generator is still around here, I'll have to look tomorrow.
 

cobbadog

Registered
I like the idea of buying a usable 2nd hand welder while your back in the States give it a good run for a while and if it works well, strip into manageable size/weight pieces and send it back to your new home.
 

JoeKultgen

Registered
The two big roadblocks to shipping one back from the states are size/weight and import duties. The only feasible shipping option is called a balikbayan box. These are used by Filipinos abroad to ship things to friends and family back home, generally items too heavy or otherwise restricted for air travel. These boxes are available in different sizes, none of which will handle an engine powered welder. A consolidator pulls together enough of them to fill a shipping container. On this end they get broken out and the final leg is handled by local shipping firms.

The value limit on a balikbayan box to stay under the customs radar is 10,000 Pesos, (about $200 US). Other forms of shipping, you have to stay under $45 or pay import duty that can range from 5% to 300% as determined by the import duty dart board or possibly the wheel of imports. I've never heard of two customs agents quoting identical duty on the same customs declaration.

Good used 3 cylinder diesel engines are cheap and available, The better ones are Yanmar and Kubota sold as Japanese surplus. A 14-16 HP costs around $400. A new Chinese knock off of the same engine costs about the same and if you need parts, finding something that will fit is a complete crap shoot.

To get really consistent welding rod here you'd have to do a bulk buy of enough to complete the entire job. Even then, there's no guarantee that whatever you bought will age gracefully. The closest thing to universally available is Chinese made 6013 and 7018 in 3.2mm or 4mm @ P500/5kg. (just under a buck a pound and probably worth every penny)

Any welder I cobble together is going to have absolutely zero support from a dealer network. That means when it breaks I have to be able to tear it down and rebuild it from basic components that can be sourced or fabricated locally, with limited access to machine tools.

It WILL break, everything breaks here. Some pretty impressive stuff gets built anyway. That's one of the things I love about this place. So, that's the background.

My plan, subject to revision, is to get my hands on the highest output alternator I can find. Then, gut it to a rotor, stator and brush holder before I hang it on that borrowed Geo engine. I intend to hook up the stator in a delta configuration then run the 3 phase output to a high capacity bridge rectifier and the welding cables with a choke coil on the ground side. I *should* be able to use the Arduino as a programmable controller to juggle the engine RPM and field current to get a volt/amp combination that will let me run a decent bead. That's all I really need, a way to lay down a decent bead with the available electrodes on whatever recycled crap they're using to make Chinese 4mm mild steel sheet.

Once I have it working stateside, I'll pull it off the Geo engine, throw it in a box and add enough welding cable to max my shipping weight. Accessories like ground clamps and electrode holders are cheaper here. So is the cable but I don't trust the insulation on the local stuff. This is the country where the Chinese ship the stuff that won't meet Harbor Freight's high QC standards.:)
 

JoeKultgen

Registered
I dont know, kinda a unique situation you have. How expensive are dc batterys over there? you may be better off using batteries to weld with and using a heavy duty truck alternator to keep them charged. I know around the mines they have used the batteries on a mining scoop and what ever part of the scoop that varies the speed to weld with. just dont think a alternator is going to hold up well welding for very long.
That's one of the things I'm concerned about also. I'm hoping that if I find an alternator that can do better than 200 amps and then use a programmable controller to vary the field current and engine speed I can get something that will lay down a nice bead with 1/8" rod while the alternator stays cool enough for continuous duty.

Batteries are about the same price as stateside and I'm looking at welding for hours, not minutes. This is also a very poor country. A battery bank large enough to be useful would need an armed guard to keep it from walking off one piece at a time.:)
 

cobbadog

Registered
What on earth are you going to be building?

Is another option to get a genset and an arc welder . I have a small inverter arc welder that weighs next to nothing and handles long hours of use with no problems.
 

JoeKultgen

Registered
What on earth are you going to be building?

Is another option to get a genset and an arc welder . I have a small inverter arc welder that weighs next to nothing and handles long hours of use with no problems.
I have used one of those as well and was quite happy with the performance. But that was running off of mains delivering a true sine wave. I've heard the performance and reliability suffers when you try to run them off the square or modified square wave AC delivered by the less expensive gensets. Anything that feeds them properly is in the same price and weight class as a stand alone engine powered welder.

Also, as I've mentioned in other posts this is a poor country. The odds that an item will get stolen are heavily influenced by how easy it is to identify and the size of the potential resale market. Blackouts are common enough that everybody is looking for a good deal on a genset. Small inverter or buzz box welders are almost as popular. A contractor might be interested in an engine powered welder, but not if it's a "one off", and certainly not if the legitimate owner might spot it at a job site and get the cops involved. They buy equipment to solve problems, not create them.
 

Sonny Reese

Registered
Not positive of exactly what you are looking for, but p-1 aircraft generators were used to make welders around here a long time ago. --- I have one and also another p-1 somewhere.They are 400 amp dc,(the good stuff!lol!!)
Anything homemade will have severe time restrictions to prevent overheating/burnout/etc.
I have seen some regular alternators used but they have a severe limit on time til burnout.
The Kenworth W-900 I drove had a 200 amp alternator on it. When it burned out and had to be changed, that sucker weighed a ton! -- I think it was heavier than the p-1's.
I know this is not much help, but I am just tossing out some suggestions for you to ponder over!! Good luck on your venture!
 

JoeKultgen

Registered
Not positive of exactly what you are looking for, but p-1 aircraft generators were used to make welders around here a long time ago. --- I have one and also another p-1 somewhere.They are 400 amp dc,(the good stuff!lol!!)
Anything homemade will have severe time restrictions to prevent overheating/burnout/etc.
I have seen some regular alternators used but they have a severe limit on time til burnout.
The Kenworth W-900 I drove had a 200 amp alternator on it. When it burned out and had to be changed, that sucker weighed a ton! -- I think it was heavier than the p-1's.
I know this is not much help, but I am just tossing out some suggestions for you to ponder over!! Good luck on your venture!
Thanks! At this point, suggestions based on experience are exactly what I'm looking for. The deepest I've gotten into motor-generators was rewinding the armature on a fried Onan. So maybe I have a slightly skewed idea of "homemade". If I have to strip the stator and hand wind it differently to get something that will do what I want... yeah, I'll go that far.
Time I've got, money is a problem.:)

It's my understanding that all you need to make electricity is a magnetic field moving past a conductor, but as they say, "the devil is in the details". The big difference between generators and alternators is that one moves the coils past fixed magnetic poles and the other moves magnetic poles past fixed coils. I played with automotive generators when I was young and a large part of their weight was the pole pieces and the heavy steel case needed to hold them in rigid alignment. An equal weight alternator has a much higher percentage of it's weight in the windings, the part that does the work. The pole pieces in an alternator are in the rotor, where they act more like a gyroscope than a boat anchor. The other reason generators got retired from the automotive scene is because they made their power in a moving part. The entire output had to pass through brushes to get it out where you could use it. The only reason alternators even have brushes is so you can control the output by varying the field current. Use a permanent magnet rotor and you can ditch the brushes, but lose versatility. As far as power goes a kilowatt is a kilowatt regardless of how you juggle the numbers to get there, though the best efficiency is going to happen in a fairly narrow band.

Which brings us to design issues, where my understanding gets a little fuzzy. An automotive alternator needs to deliver DC voltage in a relatively narrow range under load that varies from a battery maintainer trickle to the full rated amperage. A genset has to deliver AC within a narrow range of voltage and frequency over a wide load range, anything from a cell phone charger to the starting load of a refrigerator compressor. Welders (AC or DC) seem to work best when you can deliver a regulated current under varying load.

Inverter welders do this by taking mains power and making magic with semiconductors. Materials technology that will allow semiconductors to handle that kind of load is a fairly recent development. You don't have to look very far to find a welder you can lift with one hand that will do 1/4" mild steel in a single pass, for less than $100, including shipping. If mains power at my work site was an option I'd go this route.

Unfortunately, it's a BYOE, (Bring Your Own Electricity), situation. Inexpensive gensets use an alternator not a whole lot different from the one in your car to power solid state electronics that deliver anything from square wave to heavily modified square wave that has enough steps to do a pretty good imitation of true sine wave AC. Inverter welders and transformers don't handle square wave AC very well. The closer you get to true sine and the more power you need, the more it's going to cost you. By the time you have a genset that can power a decent welder you're in the same price range as an engine powered welder. There is no free lunch. If I was doing this stateside I'd shop around for a used Onan and power an inverter welder with it. While the Onan has many virtues, low shipping weight isn't on the list. The power grid is iffy enough here the green machines are all over the place. A used one at a reasonable price is harder to find than an honest congress-critter. The people who have them, ain't givin' them up.

Best balance between time and money would probably be shopping salvage to find an old engine driven welder with a blown engine and pull the generator off. The shipping would still be a killer and there's a good chance customs would assess import duty based on the new price of an equivalent item. Good luck with that. So, it's going to be DIY starting from square one.
 

JoeKultgen

Registered
Square One

I've decided to separate the "nuts and bolts" posts from suggestions and comments. That way anyone who just wants to check out the hardware doesn't have to wade through all the background. If these posts start to read like a series of lecture notes by somebody clueless try not to take offense. I discovered a long time ago that the quickest way to find out how much I don't know is trying to explain a subject to other people. :)

Here's a generic automotive alternator broken open. It was part of an article a guy did on attempting to rewind one for use in a wind generator. (not happening)

The important part is that the rotor has 8 magnetic poles and the stator has 24 slots. From the factory, those slots are filled with three windings 120 degrees out of phase. Each winding is made up of 4 coils 90 degrees apart. Each coil goes through eight changes of polarity, four complete cycles as the rotor makes one full revolution. If I haven't messed up the math that should give 60 cycle AC at 900 RPM. I'd have to modify the rotor to change this and for me at least that isn't practical. It's starting to look like the best way to get a welder out of this is going to be rewinding the stator for single phase and hooking up a cheap inverter welder.

This is a tiny 35 amp unit. Does anyone here have a high output auto alternator, (dead or alive), they're willing to peek inside and verify that it uses the same geometry? That is, 8 pole rotor and 24 slot stator?
 

cobbadog

Registered
I am not going to pretend I fully understand all that is being posted but I am finding it a very interesting read.
All the various ideas of achieving the same outcome really makes you think.
Keep posting what you find and hopefully I can keep up with it.
Cheers Cobba.
 

pegasuspinto

Registered
Just buy the biggest alternator you can get, and use the DC output. Rewinding to try to get single phase out of it won't work well. And a car alternator at 900 RPM aint gonna do squat-they are meant to spin at high speed-hence the small pulley on the alt vs the large pulley on the engine. If anything, a large alternator has more poles.

My feeling is jerry rigging a solution might be OK for patch jobs or quick projects, but if you expect to get 3 years of welding out of this thing, you're probably going to be money and hassle ahead to just get a real engine driven welder. Most of them also have AC output for things like grinders and lights.

If you are going to go the 'cheap inverter welder' route, i'd be tempted to tear into the welder, and try to feed the DC internal buss with the alternator.
 
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