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Toyman01 GRM+ Memberand MegaDork
9/6/17 6:51 p.m.

There was some interest in this generator in the Hurricane Harvey thread. I hadn't planed to do this quite yet, but since that little breeze south of here is looking to be a real witch, I figured I had better dig it out and see if it still runs. It didn't look too promising. I don't think it's run in 7 years. surprise

I actually built this not long after hurricane Hugo, the major hurricane that hit Charleston in 1989. I spent a long week after, with no electricity, no A/C and no hot showers. I vowed to never do that again. 

The engine is a 900 cc Kubota 3 cylinder diesel. This engine spent a lot of years running the hydraulic system on a bucket truck. I think it had 3500+ hours on when I got it. My father acquired three of them for almost scrap price.  The generator head is a Harbor Freight special rated at 10Kw. It's pretty nasty under there.

The engine is rated at 20 hp at 2400 rpms. The generator requires 3600 rpms to produce 240 v at 60 htz. That meant running a belt drive. I have it set up so the with the generator turning 3600 rpms, the engine is turning 2150. It makes for a pretty quiet setup.

The generator was designed for the side load of a belt drive, the engine wasn't. That meant using a jack shaft with a couple of pillow block bearings.  The shaft is 7/8" and is connected to the engine with a Love Joy coupling. The belt used to drive the generator is a 1" wide, 1/2" pitch, synchronous drive gearbelt. Gearbelts will transmit the hp without the side loads required by V belts. At the time, about the only option to order these was Grainger. The coupling, belt, and pulleys were the most expensive part of the project. 

More to come. 

Toyman01 GRM+ Memberand MegaDork
9/6/17 7:24 p.m.

This thing has been sinking into the ground behind my shop since we moved into this house. The tires were flat and wouldn't take air, so I hooked it to the truck and pulled it around to the front of the shop on flats. The sides were well rotten, lots of small animals had taken up residence. I removed the worst of the rot and rodent nests and then made a run to the store for some diesel and fuel line. The on board fuel tank had started growing algae 10 years ago and been abandoned. I stuck the return and suction line in a 5 gallon can. I added water to the radiator and checked the oil. The battery I just pulled out of the Abomination just happened to fit perfectly. 

Surprisingly enough, it fire right up. 

Well I tried to embed this but it looks like we may have lost that capability. You'll have to go to Youtube. https://www.youtube.com/watch?v=h7Fr2qsv-L0

Trying again. https://www.youtube.com/embed/h7Fr2qsv-L0

The rest of this is going to be a picture dump. If you have any question, post them here. 

Engine control panel.

Generator panel. Both volt meters have died, but the frequency meter is still working. Once the engine warms up, it sits pretty steady at 60 htz.  This is a 12 X 12 PVC box with the lid cut out for the receptacles and meters. 

Cooling fan is a junkyard special. I'm not even sure what vehicle it's from. It draws out of the cabinet to keep the engine heat off of the generator.

Control side. There is a clear door that closes in front of the panels.

Battery tray. Right below that is the fuel filter.

 Primary fuel pump. Injector pumps don't do suction very well. This is a cheap electric fuel pump.

This is the governor. They are very hard to find. I bought an entire non-running WW2 generator to get it. There were some servo driven electronic governors just coming on the market when I was building this but they were extremely expensive. I may do some additional research on that again. 

If you build one, I highly recommend doing this. This is the oil drain. It beats the hell out of climbing under the machine to find the drain plug. 

It got a oil change after I ran it long enough to get it up to temp.

That's about it. Hopefully I won't need in next week. 


RossD MegaDork
9/6/17 7:51 p.m.


mazdeuce MegaDork
9/6/17 8:20 p.m.

So all you have to do is spin the generator head at the right speed to give you 60Hz and you can plug stuff in? Is it really that simple? 

fasted58 MegaDork
9/6/17 8:30 p.m.

Cool build!

I had an Onan 15KW 4-cyl. gas genset that I wanted to convert w/ a VW diesel w/ direct drive, although the gas engine was good.

I had planned on using an old school aftermarket cruise control to maintain the RPM, the kind sensed from the driveshaft. I'd bet the later aftermarket cruise controls may be much better than what I was planning.


Toyman01 GRM+ Memberand MegaDork
9/6/17 8:55 p.m.
mazdeuce said:

So all you have to do is spin the generator head at the right speed to give you 60Hz and you can plug stuff in? Is it really that simple? 

Yep. A two pole generator turns 3600 rpms. A 4 pole generator turns 1800. It's that simple. There are a few diodes that are important to getting the fields started, but they are built into the generator head. 

Most of them don't even care which direction they turn. 

As a general rule, two pole heads are the cheap ones. 4 pole heads cost more but turn slower. 

If I had it to do again, I'd probably buy one of these and direct drive it at 1800 rpms. These are on Ebay for about $600 for a 12kw head. Do a search for ST Generator Head. 

java230 SuperDork
9/7/17 10:43 a.m.

Thanks for posting this!! I am thinking of winter plans.... And that may include a generator/shed.

alfadriver GRM+ Memberand MegaDork
9/7/17 11:45 a.m.

Great job, and great inspiration.

One note- some of your opening pictures betrayed the tension of "does it run" before you posted that.  You can tell the engine is spinning.  :)


edit- where can people find those engines???  It's a pretty cool set up.

Toyman01 GRM+ Memberand MegaDork
9/7/17 12:21 p.m.

In reply to alfadriver :

I have a habit of fixing things first and taking pictures later. wink

EastCoastMojo GRM+ Memberand Mod Squad
12/9/17 6:10 a.m.

Zombie thread, canoe removed.

Ian F
Ian F MegaDork
12/9/17 8:06 a.m.

Zombie or not, I'm glad it was resurrected as I recently thought up a similar idea for building a generator for my E350 diesel camper van build. Except using a 250A alternator to charge a bank of house batteries as well as an automotive A/C compressor to keep the interior cool during the summer. I've found small air-cooled diesel engines and would use a 12V fan cooled A/C condenser to draw air across the engine.

I'm trying to think of reasons why this won't work, since I've never seen it done before and I can't believe this is an original idea.  

alfadriver GRM+ Memberand MegaDork
12/9/17 8:35 a.m.

In reply to Ian F :

Small air cooled diesel???  Que?

Are you talking the larger tractor style engines?

Diesel vs. gas- for you, that's a great choice, since you are adding supplemental power for a diesel truck.  On the gas side, I keep wondering if there's a more efficient way to choose a small gas motor.  But one can't really get a decent fuel map of any engine to determine the most efficient engine for that. 

What's so interesting about the engine Toyman found- it's quite similar to the stationary engines that went to greatness in racing.  Like the engine Cooper used.... 

Ian F
Ian F MegaDork
12/9/17 9:20 a.m.

In reply to alfadriver :

A quick search found this one on the Northern Tool site.  although my hope is find something not quite as expensive.  $3000 isn't much less than I paid for the van... I know diesel engines are more expensive than gas engines, but this is like a factor of 10, which seems kinda nuts.  Obviously, something with electric start is a requirements so it can be operated remotely. 

Of course, the easy option is a generator designed to be used with Sprinter vans, but those sell for literally twice what I paid for the van.  Plus, I'd then have to figure out another A/C option.  The van currently has rear A/C and my hope is to make use of that system after splitting it from the engine/cab system.

You may be a good person to ask - how much HP does a typical modern R134 automotive compressor require? I've seen data of roughly 5 HP, but nothing very definitive. I can do an approximate HP requirement for a 250A alternator by backing into the HP:KW values.

The general idea would be the engine driving the A/C and alternator, keeping the clutch on the compressor. When charging needs arise, the clutch wouldn't engage. 

bigdaddylee82 UltraDork
12/9/17 10:01 a.m.

In reply to Ian F :

You can find Yanmar L70 single cylinder, air cooled, diesels, with electric start, on eBay for <$500, probably a lot less, if you're patient.  L70 is around 6.5 HP.


Ian F
Ian F MegaDork
12/9/17 10:13 a.m.

In reply to bigdaddylee82 :

By my calculations I will need a L100. The L70 won't be enough.  I wish it weren't the case since it seems the L100 is substantially less common and more expensive. By a huge amount.  The one I found on eBay is well over $5000. 

bigdaddylee82 UltraDork
12/9/17 12:57 p.m.

In reply to Ian F :

Find a scraped refrigerated, "reefer," box truck or trailer, their reefer units are usually diesel powered.  Thermo-Kings are/were 3 cylinder Yanmars, and Kubotas are often used in some reefers as well.

If they can keep a 53' trailer refrigerated in the Summer, they should have plenty of power to run a gen head, and an automotive A/C compressor.

Stainless New Reader
12/9/17 1:24 p.m.

In reply to Ian F :

You may be a good person to ask - how much HP does a typical modern R134 automotive compressor require? I've seen data of roughly 5 HP, but nothing very definitive.

Not to stick my nose in someone else's conversation, but I might be able to offer something for your question. I am currently running a Chrysler RV2 compressor (R12) in my garage as an air compressor, and it's being happily powered by a garden-variety Sears 2 HP 120 VAC motor. I've never blown a 15 A breaker and the motor is barely warm to the touch, thus suggesting that it's not really working very hard. No problems up to 150 psi in my 20 G tank.

Also, there's a guy named M.C. Pletcher on YouTube who does all kinds of carnot experiments with auto AC compressors. He build a beer chiller out of a York and a treadmill motor, and the York wasn't spinning very quickly at all. You'll lose cooling power by "gearing" the compressor down, but it does mean that you can run the thing with much less motor power. 

Anyway, hope that helps.

Ian F
Ian F MegaDork
12/10/17 12:36 a.m.

In reply to bigdaddylee82 :

The problem there is space. Where would a 3 cylinder Yanmar fit under a E-350 van? Point of the driver behind this whole idea is to keep the system as compact as possible.  In reality, I'm not 100% sure the 1 cyl idea I have will even fit.  

In reply to Stainless :

Helps some, thanks.


alfadriver GRM+ Memberand MegaDork
12/10/17 7:47 a.m.

In reply to Ian F :

I'll have to look into it- I've heard the same info as you have- and I also know that not all compressors are the same- just like alternators. To the point I bet it would be possible to find a set up with the smaller diesel engine that would fit into overall concept budget.

bigdaddylee82 UltraDork
12/10/17 11:56 a.m.

In reply to Ian F :

While they're no B&S lawn mower engine, I believe they're more compact than you think.

Wally GRM+ Memberand MegaDork
12/10/17 6:45 p.m.
ProDarwin PowerDork
12/10/17 6:55 p.m.

Can you not use the van's engine as the power source?  I know its not the most fuel-efficient option, but it IS the most space-efficient option, as you don't need another engine.  And you don't have to maintain/deal with the complexity of another engine.  It would also allow you to keep the A/C system intact.  

Aditionally - how many things do you have in your camper that need an A/C power source?  Aside from appliances you can do a whole lot of stuff with DC.

Ian F
Ian F MegaDork
12/10/17 9:17 p.m.

In reply to ProDarwin :

Because a 7.3 idling away for 8 hours is about as subtle as setting off fireworks all night. The point to this is basically to install a generator to run the A/C- which currently doesn't work anyway, so I have the opportunity to divorce the rear A/C from the main engine and run off something more... discreet. 

Part of me (most of me) actually wishes the van had a gas engine. Then I'd just rig up a Honda generator, regular A/C and be done.  Regardless, I went to look at the van again today and it's starting to look like this whole project is DOA.

Petrolburner Dork
12/17/17 11:06 a.m.

I don’t know, a van parked with the engine idling says to me “waiting.” A van parked with a generator idling says “camping.” Where are you planning to be parked while one of these engines is idling? Campground?

Ian F
Ian F MegaDork
12/17/17 11:04 p.m.

In reply to Petrolburner :

Well... the intent was ski resort parking lots for DH racing.  A small generator humming away wouldn't bother too many, although I'd prefer something like a quiet Honda generator. 

Regardless, I did some fiddling with the van today and things don't look good. The interior is just not big enough. I was hoping the bikes would fit across width-wise with the front wheel off. Nope.  

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