Identify this old Army Genset

[GeorgeTaylor]

The tag is messed up but I can read that it produced 115 VAC. Magnets in the flywheel are too weak to produce spark (will not even hold a washer) so I gotta figure out how to fix them. Otherwise it just needs some minor parts.

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[Ed Radtke]

engine is Jacobsen.civilian parts fit.

[GeorgeTaylor]

Finally gave up the "be nice to it" routine and went to the tags with a wire brush. To my surprise they are raised letters. Here they are:

Generator GN-51D
Order #29387 | PHILA 51
120/240 VAC | 300W
2.5/1.25 Amps
60hz | 3600 rpm

Engine GE-12-G
2 stroke
Jacobsen

The magnets in the flywheel are weak enough that they will not hold a 1 inch pan washer. I figured out which magneto pole was which with a compass.

So far I cut off a 6 inch section of carbon steel an inch in diameter and have wrapped it with about an inch & a half of bell wire. Transformer or solenoid wire would be better but I am working with what I have on hand. I connected a 12V battery and figured out N & S with a compass once again.

I am hoping to reenergize the magnets in the flywheel by clamping the N pole of my improvised electromagnet to the S pole of the flywheel and vica-versa.

The magnets look to be cast into the flywheel so if this fails I will be looking for parts. Any way to match up to the correct civilian varient of the flywheel?

[KidDynamo]

I wouldn't be too quick to mess with the flywheel magnets as it is fairly rare for them to be the problem, tho not impossible. Consider cleaning the points to spotless, oil free that you can pull a pristine business card through them and leave no trace. The try for spark again. If none, then repeat.

The gizmo in your last two pic's is a rectifier that takes an a.c. feed from the generator, converts it to d.c. and then feeds it to an electromagnet in the little dome-topped gizmo nearby and the two items act as a highly stable governor provided all works good.

I guess the governor action boils down to the strength of an electromagnet balanced with the strength of a spring. Not sure of the adjustment procedures but as the speed of the engine increases, the resultant d.c. voltage goes up, resulting in a stronger magnetic field. When all is properly adjusted, the engine is held at 3600 rpm (I think).

I have a rectifier on one of mine that is just a pile of corrosion. If I get to it, I was planning to replace it with whatever I can find and go from there. I have a box of old rectifiers but maybe not a "look-a-like".

There were quite a few different generators using this engine and frame. Different outputs for different service requirements. Near as I can tell, they were made in WWII and also Korean War era. The full package had a plywood carrying case, a canvas cover, spare parts & tool kit, and a manual.

I have 2-1/2 units, all 110v/220vac like your's, but no case or canvases.

[GeorgeTaylor]

The rectifier has that green bi-metal oxidization but I don't think it is bad enough to be a problem though I have not run the genset yet so it remains to be seen.

The points, condenser and coil are spotless & new. That is the way it was when I bought it. This genset has practically no wear on it any where other than handling wear.

It would appear that my screwdriver was the first to open the blower housing and my wrench the first to open the Carburetor for inspection. Even the terminal posts on the gen-head are without scratches.

The magnets on the inside of the flywheel are just plain weak - failing to hold even an inch diameter washer. If you hold the spark plug wire and rotate the crank you get a tiny jolt, but none more.

From the inside of the flywheel there is a cavity behind each magnet just large enough to hold a smallish NiB magnet I removed from old computer harddrives. With these in place I get a much harder jolt and the spark plug does work so I am sure it is the magnets. Thanks for the input though. I will remember to keep that area spotless.

Since you have at least two working models I wanted to ask if they are under-rated they way military gensets typically are. Also I wanted to ask what kind of power I can expect to derive.

Thanks for the help!

[John Newman, Jr.]

See if you can find any identification on your flywheel. It should say who made it (Wico or Eisemann, most likely) and give a model number. I have a couple of Jacobsen parts engines and might have a good flywheel that would match.

[GeorgeTaylor]

WICO Electric Company

Part No. Y4988

[GeorgeTaylor]

Okay, the electomag did reenergize the magnets a little but not much. Then again I was improvising and it was likely not very good for the task.

Anyway there is a small cavity behind each magnet. I have stacks of little Super Magnets that I pulled out of old harddrives. Some small and some larger. I took two of the little ones, figured out which was north and south facing and inserted 1 each in the cavities with JB weld filling the rest to hold it in place. Opposite were balancing holes so I filled two of those with JD Weld as well to offset the added weight.

Put the flywheel on and lots of spark! Gingerly reassembled the genset and it started on the first crank! No vibration from it at all so I reckon I got her balanced out pretty good on the flywheel.

Running wide open though, like the regulator is not working. The rectifier has bi-metal corrosion so I will try and clean it up some. It was pushing about 145 volts though so it makes power. Yipee!

[John Newman, Jr.]

Glad to hear you were able to get it running. I did turn up a flywheel from an old Jacobsen, but it has a different number. Mine says it is Part Number Y3054. I don't know what the difference might be between them. The only things I can think that would be different would be the inside diameter and the position of the keyway. I didn't think to measure the inside diameter, but I did note the keyway position. When looking at the INSIDE if the flywheel and the magnet is pointed straight up (12 O'Clock), the keyway is pointed at about 3:30.

[GeorgeTaylor]

Thanks, I will take a look at mine and see where it lines up. While I am there I will measure inside diameter to see where it falls.

[GeorgeTaylor]

Anyone got a manual on this genset?

Generator GN-51D
Order #29387 | PHILA 51
120/240 VAC | 300W
2.5/1.25 Amps
60hz | 3600 rpm

Engine GE-12-G
2 stroke
Jacobsen