Hobart mystery to me

[Mech3]

I have just aquired a hobart 300 portable welder. From what I can tell it is a GR3152 Spec 972B
300 watt 40 Volt welder
12KW 3ph
110/220 ac power
the best I can read on the tag then there is a tag on the frame
US Army Corps of Enginers
model: 1951
engine: Chrysler Ind
it is a flat head 6.
My question is where does all this AC power come from? Both ends of the generator has segmented commutators no slip rings any where.

[Mech3]

I can look down beside the brushes and see the commutator but I always thought segmented was a DC generator to have AC you need an alternator with brushes and slip rings.

[Pin Head]

I can look down beside the brushes and see the commutator but I always thought segmented was a DC generator to have AC you need an alternator with brushes and slip rings.


That is correct: segmented commutators are DC. What makes you think it is an AC generator? Most welding power supplies of that vintage are DC because rectifiers that could handle welding current were expensive and unreliable in the 50s. Usually, the auxiliary power is 110/220 DC on these units.

[Mech3]

I am going by the tag on the generator control panel it says.

12kw 3ph 60 cycle 64/32 amps
110/220 volts AC power

[Pin Head]

Maybe you haven't peeked closely enough to find the slip rings yet. At 12 Kw, they won't be small.

[Hobart Expert Bill]

Mech 3,
I do not have any info on the spec. 972B other than the first units were built in 1949 and continued through the early 60's.

The auxillary power slip rings should be inside the generator end cap that extends out of the lower front pannel. Are there 4 115 VAC recepts on the right lower panel and 2 220 VAC recepts on the left ? There should also be two sets of welding output studs, one AC and one DC. The second set of brushes should be at the back of the rotor at the fan/engine coupling for the welding power.

[Mech3]

Wow there is a third set of brushes on slip rings there, I went back and looked
The control panel is on the side of the machine under the side cover it has 3 duplex recepticles for a total of 6 110 plug ins 3 220 twist lock plugs above that then on each side of the outlets are 3 studs from top to bottom for a total of 6 studs I assume that is for the 3 ph. On the welder panel it only has 2 post one Ground pos one electrode neg with a polarity switch std and rev i guess center is off no AC welding hook ups or switches to weld AC. Looking at the panel the engine is to your right, looking through the opening between the engine and generator you have a small set of brushes and commutator plus another set of brushes running on slip rings. Fan for it is in the center of the generator and on the left looking inside the generator is large brushes and commutator.

[lars66]

I have just aquired a hobart 300 portable welder. From what I can tell it is a GR3152 Spec 972B
300 watt 40 Volt welder
12KW 3ph
110/220 ac power
the best I can read on the tag then there is a tag on the frame
US Army Corps of Enginers
model: 1951
engine: Chrysler Ind
it is a flat head 6.
My question is where does all this AC power come from? Both ends of the generator has segmented commutators no slip rings any where.

My Hobart 300 amp is the D W designation 971b specs made 5-26-1950 with all the power options including 3 ph.

[Mech3]

Wow!! I can go and tell my wife that I actually got something that they made two of this time. I haven't got mine running yet. Could you tell me how they are for welding? I am not real concerned about the power, I figure it is a nice bonus. I just wanted a good DC welder and the price was super right on this one. I didn't even have to spend the money to get it here as the man delivered it to me. Then I got to hunting info on it, which dosen't exist. I thought that once again I had something that they only built one of. I have a yard full of such items. Any info you may have would be much appreciated.

Thanks Dale

[lars66]

Mine welds great, nice and smooth with 7018. I have never found any manuels for mine either. The engine is a 251 c i chrysler industrial and a little thirsty so I havent used it much in recent years.

[Mech3]

I got the engine running today. I still have welder problems the fine tune reostat is broke, it is very large and pops out for remote use. I know there is no manuals available for this machine. Would one work out of something else? I was also wondering does this control the voltage from the exciter? If so can it be temporarily jumpered to be able to test further before spending a pile of money for parts to find it is fried. Thanks for your help.

[Pin Head]

Yes, the fine current control rheostat typically regulates the power in the exciter circuit. If it is broken, then the circuit is "open" so you can test it at full power by bypassing the rheostat temporarily. You can download a schematic for a DC only Hobart generator of similar vintage here:
https://webfiles.uci.edu/cglabe/Photos/HobartG261scheme.pdf?uniq=95e1kd
Chances are it will be very similar except for the AC side.

[Mech3]

Finally got a chance to work on the welder again today. I found a couple bad brush springs on the exciter, I started to still some of my wifes bobby pins and build some springs, then decided it would be to wide to get very many wraps. Just wondering if anyone else has a fix for this. I also found I need to do some rewiring once I got the fuel tank off and could see the wiring on the back of the panels and especially coming out of the center windings for the AC which is under the tank. I am glad it didn't power up now. 12Kw of 220 3ph would of be a fireworks show I wouldn't want to see.

[Mech3]

I am in search of engine info such as points setting, plug gap, and valve lash. The best I can tell it is a 237 cid engine, the tag on the side says IND 7A-2 but unable to find any more info on this engine. Any help would be greatly apreciated. Thanks

[Pin Head]

The same engine was used in the same vintage Dodge military trucks, like the M37 power wagon. Search the net for "Dodge M37" and you should find what you are looking for.

[lars66]

I am in search of engine info such as points setting, plug gap, and valve lash. The best I can tell it is a 237 cid engine, the tag on the side says IND 7A-2 but unable to find any more info on this engine. Any help would be greatly apreciated. Thanks

Thats the same engine specs mine carries. I put a rebuilt engine in mine many years ago and was told by the rebuilder it was a 251 C I.

[Mech3]

Thanks for the help. I have found so far that the engine is a 251 block, same bore and all as the 251, but has a shorter stroke on the crankshaft to make it a 237. I also found the valve lash settings, but it list two different possible exhaust valves with different settings, standard exhaust valve sets at .012 or a sodium filled valve that sets at .020, so now I need to decipher what valves I have.

[MM251]

I have a variation of this model. Mine only does DC welding (which it does beautifully) and it has a 3KW 110V DC secondary generator. This does work and has proved handy when out on a jobsite. The Milwaukee brand of tools has long been built to run AC or DC. My 4" grinder, purchased in the last year or so, is still marked to run on 110V AC/DC. Otherwise, Ac is not available to me. The flat head six runs like a top, and I especially like the sound of the engine, as it has about one foot of 4" exhaust pipe without a muffler. Music to my ears! :D :D

Good luck - it's a great machine.

[old fart]

Try Mitchell Motor Parts in Ohio 614-875-4919

[Mech3]

Well, I finally got it to welding about 3 weeks ago, got the AC generator side working this past weekend. Sweet welding abilities, But I think it may be bigger than a 300 amp machine, even though that is what is stamped on the plate. I can weld 5/32nds 7018 rods with the settings at 3 medium uphill, or you can run flat and hot at 3 high. I can turn every thing down 1 low and run a 6011 3/32nds good. Is that normal for a machine of this size? A friend of mine, who does shut down work, said it seemed as hot or hotter, than the lincoln vantage 500 they were using on his last job site, and a whole lot smoother.

Thanks for all the help.

[ventureline]

Well, a 300 amp machine will put out over 400 amps, though best check your rpm via your auxillary power in HZ, should be around 45 HZ low and 62 hz high idle no load

[Mech3]

I checked it and it was at 58 Hz high idle I didn't think to check at low idle I will do that this weekend.

Thanks