WW2 US Army Homelite Generating Set

[nutgone]

Hi, I have recently started to restore a WW2 Homelite US Army generator. I understand these old Homelite sets are quite common over there, but over here, in the UK, they are quite rare.
So far I am learning as I go, this is quite a complicated machine, but very well engineered. Basically I am looking for any information I can find. I would like info on the engine, the starting procedure, possibly a fuel system schematic & any info that's out there for the genny side of things.

It's a model PU-4/CPN-2 & has 2 outputs. It's rated at 115v AC 400 cycles & 27v DC.
I'm guessing the 27v DC is charging voltage for 24v systems. I can also guess the 115v AC 400Hz is for Radar systems, but would like some clarification on this if possible.

I have no idea how many amps or watts this thing is capable of either. There are a couple of information plates missing from the unit, but I know it was built late in 1944. I didn't even know it was a Homelite (that's taken me a long time to work out ).

From my restoration I have found out it's a disc valve 2 stroke engine, very well designed. It has a complicated fuel delivery system, which includes the fuel tank positioned below the engine. Some say it's pressurised with crank case pressure, but I don't think this is strictly true, it's a bit more complicated than that.

So, any information on these sets will be great. I would even like to know what this particular model was used on. Was it airplanes or tanks or something else?

I have a few resto threads going on, with full pictures & in-depth commentary on what's going on. (am I allowed to post up links? Please delete the following if I am not)
Here's the resto thread on a US site....
1944 Homelite PU-4/CPN-2 - SmokStak

& here's the resto thread on a British forum....
WW2 US Army Homelite Generating Set

& here's a link to the Photobucket album where I keep all the pics of this project....
http://photobucket.com/nutgonesyankgenny

Thanks in advance for any help, I love this site, there's some great stuff on here. You see some US army stuff at the shows here in the UK, maybe I'll take some pics at the next show I attend (at the end of the month) & post a few up here.

 

[leedawg]

Was looking at all the pics on smoke stak. Looks great you do know its a 400 hz unit noticed that on the voltage regulator. Sweet little machine though.

 

[nutgone]

400Hz isn't such a massive problem over here, in the UK, as our houses all run on 240v anyway, so I was only going to power some light bulbs from it (we use 110v on our construction sites, for safety, so 110v incandescent light bulbs are pretty easy to come by).

It certainly is a neat little machine, I just wish I knew more about it. I'm starting to believe this particular model was fitted into aircraft, during the war, for stand-by power.
Funnily enough I also have a similar British item, only this was a ground based unit, used to power up Lancaster & Harvard bombers & was built by the Douglas Motorcycle Co.

All these engines (& more) are actually the joint property of my twin brother & me, they've all been left to rot for the last 15 years or so, we're slowly restoring them all.

 

[steelypip]

Interesting. The 90-100 octane tag suggests that it was expected to run off of avgas, which, along with the 400Hz and two stroke (lightweight) nature of the beast suggests that you're right about it being an aircraft-mounted APU.

What I found most interesting about it (other than that wacky crank-timed rotary intake valve) was the fuel mixture instructions: 16:1 with 30W oil would be a very smoky exhaust, and with point ignition would be an absolute beast to start on a cool day. This dovetails with the memoirs I've read about people dealing with (often with blunt objects and curses) the external two-stroke APUs used for B-17s and B-24s at bases in the UK.

For the record: I would not run it on 16:1 30 weight oil. It will smoke and be hard to start. Probably the closest you could easily get in a decent, modern lubricant would be a racing two-stroke lubricant for air-cooled motorcycle engines. The Klotz brand is one good example, and might be available in UK. I'm especially fond of the ones with some degummed castor oil in them because it's such a good EP lubricant and preservative. Besides, it smells good when it burns.

A second choice would be chainsaw engine oil - they're air cooled as well, and tend to run more oil in the mixture than is seen in recent larger two-strokes. Find a professional woodman or two and ask what they use for lube in their chainsaw engines.

I would be cautious about using a modern two-stroke lubricant at less than 20:1 in the engine just because it isn't designed to direct the oil into the bearings efficiently as a modern two-stroke would be.

 

[nutgone]

Interesting, you talk about lubricants. I've been thinking about this & I was going to use the original mixture, but straight oils are quite expensive these days, & like you say, it'll be hard to start (I believe these units could use the 27v DC genny as a starter, so this probably wasn't such an issue back then, & I could turn it over with 2 12v batteries connected in series, but I don't know where to connect them).

I didn't want to use standard 2 stroke oil. I use it in my other old 2 stroke engines, & usually at 25:1 (although they too are originally 16:1 machines, but modern oils are so much better), but these don't have complicated disc valve systems in them, you've obviously seen the pics, that disc valve runs metal to metal, so relies on a good film of oil between the two parts to keep them from wearing prematurely.

Thanks for the suggestion of racing 2 stroke oil, that sounds like the best option. I had thought about mixing a modern engine oil. maybe a multigrade, at 16:1, instead of the straight 30 oil, but I don't know how a modern oil would mix with petrol & these modern multigrades tend to have detergents & suchlike in them.

Now I'm concerned about the octane rating of the petrol (sorry, Gasoline ) I hadn't realised that 100 rating was so high. Over here we get regular (95 RON) & super (98 RON) petrol, but I believe our octane rating system is different to yours.

I guess all I can do is get the best I can. I'm not sure there's much in the way of adjustment on the timing of these machines, but I can soon find that out.

Thanks for the replies so far & for all the suggestions, it's all really helpful & very much appreciated.

 

[steelypip]

The octane ratings are less of a concern than you might fear. The US military standardized on US SAE Research Octane Number through all of WWII, and I believe that's very close to the EC rating system standard. You should be fine with 95 RON fuel. Miscibility with the two-stroke oil should be good as long as there isn't too much ethanol in the gasoline (which is not, I believe, commonly a problem with fuels in UK and Europe). Do be sure to mix the fuel and oil at room temperature, though - the racing two-stroke lubes tend not to go into solution well below freezing because the castor oil gels.

I wouldn't worry much about retarding the ignition timing - it's unlikely that you'll be running the engine at high loads or extreme temperatures, and that's where octane sensitivity might rear its ugly head. The cylinder and head are well finned and the cooling fan looks more than sufficient. I suspect that they run cold under most circumstances.