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From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: 10 kw generator project
Date: Thu, 13 Nov 2003 02:40:34 -0500
Message-ID: <>

Slightly off-topic but some folks are interested in my projects.

This is my current one - a 10kw diesel powered generator for my concession
trailer.  The opportunity to build one came about a couple of weeks ago when I
attended the Lawrenceville, GA hamfest.  A guy there had a 19hp twin cylinder
Deutz diesel engine for sale.  Brand new in the box.  At a giveaway price.  Of
course I had to take it home with me.  I'm probably the only one in this group
who has a diesel engine at the foot of his bed :-)

Then the search began for a suitable belt driven generator.  I found a
military surplus one but it weighed about 250 lbs by itself.  Since one
criteria is that two guys be able to pick the genny up and set it in a truck,
this was eliminated quickly.  Sad, because it is a tough generator.

After looking around on the net I found this place:

That 9kw rated one would do the trick and the price and weight were right on
the money.  It came in today.  According to the guy who owns the company,
these are from a contract cancellation and are being liquidated cheap.  This
is the same generator Northern gets about $600 for.  This guy ships free which
is worth probably $50, as the package weighed 109 lbs.

This is a very simple generator.  Brushless, self excited, two pole (3600
RPM), capacitor regulated (change the cap value to change the voltage.)  This
type of generator produces fairly significant harmonic distortion because of
the straight rotor and it doesn't regulate the voltage very well vs power
factor.  But since all my loads are resistive, it fits my needs perfectly.
And being capacitor regulated, it should parallel with another generator
without any complications.  For when I move up to my 4 cylinder engine :-)

I absolutely HAD to mate the two together and try 'em out before I went to
bed.  Here is the result:

The generator is running in this photo with about an 8kw load.  I had to
scratch up every heater I could find to make that load.  They're scattered
around the unit.  Stack heaters, heat guns, ceramic heaters, quartz-halogen
lights. I found that the generator would carry a 10kw load without excessive
temperature rise.  This same generator is rated at 10kw elsewhere so this must
be a contract thing.

For a 1 hour lashup this works amazingly well.  I'm getting a little belt
slippage which will cause me to change to a cog belt tomorrow.  The diesel
engine governor has a bit too much droop so I'm going to rig up a solenoid
that goes in series with the output to press on the governor arm.  The more
load, the more the governor is torqued.  That should make a nice,
non-solid-state, non-mechanical governor with enough gain for my purposes. For
those into I&C, this will insert some reset (integral) action into the control

The response of the diesel governor is impressive.  There is NO sag in RPM
with the application of full load from the no-load state.  There is enough
inertia and the governor is fast enough that the frequency stays constant
through the transient.  I can just about stall an Onan with that trick :-)

Just as a shot in the dark, I decided to gear the generator so that the engine
would run 2900 RPM with the genny at 3600.  This turns out to be right on the
money. Though the engine is rated for full power at 3600 RPM, it's a LOT
quieter at 2900.  I may try to drop another 100 RPM and see what happens.

The voltage is right on the money at 240/120 when the RPM is 3600.  I
experimented with adding capacitance and could raise the voltage several
volts.  This will be very handy when I have to drive a long length of cord.
I'll just add the cap and a switch so that I can invoke "high voltage" mode
when needed.

Depending on what the cog belt components cost, it looks like I'm going to
bring this thing in under $700 and under 300 lbs in weight.  Not bad at all.

One other little thing of note.  The cranking batteries are a pair of 17ah AGM
12 volt batteries, visible in the right of the photo.  These are the batteries
like I use in my scooters.  Normally one battery will do the job but these are
at the end of their lives.  Amazing how much power these little AGMs will

The Deutz engine is also very interesting.  The manual has instructions on how
to run it on everything from ordinary diesel fuel to vegetable oil.  Says to
thin the veggie oil with gasoline to keep it from solidifying.  Basically, it
says that anything that will burn, isn't gritty and has a cetane rating of 40
will work just fine.  I didn't have any diesel handy so I fired it on kerosene
for the first run.  Couldn't tell any difference between that and diesel as
far as sound or power goes.  Gotta try some french fry oil next :-)


From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: 10 kw generator project
Date: Thu, 13 Nov 2003 13:05:37 -0500
Message-ID: <>

On Thu, 13 Nov 2003 09:06:17 -0500, "JEB" <berndt at berndtmd dot com> wrote:

>Well I have two questions John...
>1.  I was thinking about making a generator with a gas 18HP motor off of a
>riding lawn mower I have.  I looked on ebay and saw those generators
>advertised that you bought.  I also saw other generators for about the same
>price but they put out max at 1800 rpm instead of 3600.  Wouldn't that be

Yes.  4 pole generators are superior in every way.  Except two.  Weight and
cost.  The 4 pole unit produces cleaner power, handles overloads better and is
quieter, particularly with unbalanced loads which make 2 pole machines vibrate

The other problem is, your engine won't make 18 hp at 1800 RPM.  If the torque
curve is flat (it isn't in a gas engine but generally is in a diesel) the
power produced would be half.  Yours would produce significantly less than
half, since the engine has a positive sloping torque curve.

The major part of my prototyping is to figure out how slow I can run the
diesel and still carry the load I have.  This engine is larger than required
so I can slow it down some.  Looks like about 2800 RPM is going to be it.
I've discovered through casual research that for the people I've asked, an
engine is perceived much less noisy if it doesn't run at 3600 RPM.  Probably
because we're all conditioned to 60hz noise in our environment.  Even a couple
of hundred RPM seems to make a large difference.

>2. Why are diesel engines normally referred to as "engines" and gas or
>electric are generally referred to as "motors"?  :)

Got me.  Why are alternators called alternators when mounted in a vehicle but
generators elsewhere?  Crazy humans, I guess.


From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: 10 kw generator project
Date: Thu, 13 Nov 2003 13:20:25 -0500
Message-ID: <>

On Thu, 13 Nov 2003 09:48:36 -0500, Joe Bedford
<> wrote:

>Neon John wrote:
>> Slightly off-topic but some folks are interested in my projects.
>> This is my current one - a 10kw diesel powered generator
>Cool generator and diesel. Now how about building one with
>inverter output so that diesel can idle with no load? :)

I've given a lot of thought to that topic.  The hardware would be MUCH
simpler.  A high frequency alternator would be very much smaller and lighter
than the 60hz behemoth I'm currently using.

A major factor is time.  I've designed high power electronics for client
projects in the past and know how long it takes to make the design
bulletproof.  I have a huge amount of admiration for the engineers who design
these el-cheap inverters we're all now enjoying.  With a second restaurant
opening, my neon business keeping me busier than I like and the concession
operation, I just don't have that kind of time.  Maybe in a few months.

If/when I do one I'll probably copy the architecture of my Generac Impulse
inverter generator.  The alternator/rectifier (similar to a car one but
larger) generates the high voltage needed directly, about 350 VDC at full
load.  The CPU board drives a single big honking semiconductor (a FET I think,
might be an IGBT) for each polarity in a PWM mode to synthesize the sine wave.
The THD is under 2%.  The 4kw generator fits entirely inside the engine

My other consideration for this application is that once I flip the switch on
the concession trailer, the load goes to full and pretty much stays there.  No
possibility of idling until the event is over.

I have over 200 ft of 6/4 SO cable so I can locate the generator where it
doesn't bother anyone.  I have a fold-up box I made that is lined with sound
absorbent foam that I place over the generator to further damp the sound.  I
use this component approach instead of one big heavy package so that one or
two men can handle the parts without lifts or other mechanical aids.


From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: 10 kw generator project
Date: Thu, 13 Nov 2003 20:57:58 -0500
Message-ID: <>

On Thu, 13 Nov 2003 17:21:08 -0500, JD <> wrote:

>On Thu, 13 Nov 2003 02:40:34 -0500, Neon John
><> wrote:
>>Slightly off-topic but some folks are interested in my projects.
>>This is my current one - a 10kw diesel powered generator for my concession
>>trailer.  The opportunity to build one came about a couple of weeks ago when I
><much snipped>
>We live out in the boonies on a hobby farm and have a 35hp deisel
>tractor. I thought of getting a PTO genrator that would run of the
>live hitch on the tractor. Rading your post, I wonder if it would be
>possible to set up the gen you found to run off the tractor. Any

I don't see why not.  It would be easier to do it with a 4 pole (1800 RPM)
machine, though.  What is a PTO?  540 rpm or something like that.  To go to
3600 would require a pully ratio of 6.67:1.  If you put a 4" pully on the
generator that would require a 26" one on the PTO, if you do it in one stage.
An 1800 rpm one would only require a 13" one.  Of course you could do it in
two stages but that would require a jack shaft, bearings and so on plus
probably some welding.

Unless it's designed for the purpose I'd be leery about trying to take any
significant power off the front of the engine via the pulleys.  Many crank
snouts aren't sturdy enough to handle the stress.  there is a lot of torsional
stress generated by a 2 pole machine.  The torque requirement minimizes as the
poles line up and peaks as they reach the flux reversal point.  With the
StroboTach I can see my generator appear to rotate backwards several degrees
on each flux reversal.  A flywheel on the generator shaft would help, of

Have you considered one of those PTO generators?  They're not all that
expensive at about $1200 or so.  With those you just slide 'em on the PTO, set
the governor and go.  Northern has 'em for about $1800 but I've seen 'em
cheaper on the net.


From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: The case against Propane Generators in winter
Date: Sun, 07 Dec 2003 13:55:08 -0500
Message-ID: <>

On 07 Dec 2003 14:43:15 GMT, tmarik6440@aol.comnojunk (Tom Marik) wrote:

><< I'm getting the 5.5Kw diesel.  Any experiences on starting?  The plan is to
>be withing 50 miles of the southern border  November through April.
>Well, with this 19hp diesel engine I'm using on my generator project, turn the
>switch on.  Give it a few seconds to heat the glow plugs.  >>
>The engine is 10.7 HP two cylinder and 29 CID.  I don't have the manual and
>don't know if it has glow plugs.  It's supposed to start at minus 20 F.

It got down to 25 deg last night and after thinking about this thread I
wheeled the engine outside and let it soak for a few hours.  I then hit the
start switch immediately without allowing the glowplugs to warm.  Started
right up, though it knocked and belched a bit more than with the glow plugs
hot.  That's not 20 below, of course.

I don't suspect you'll have any problems.  If your engine is water cooled the
worst you'd have to do is add a block heater.  I really doubt that would be
necessary though.

If you're really worried I suppose I could roll the engine into my walk-in
freezer and let it soak at 20 below to see what would happen.  Have to check
to see if your winter fuel will gel or not.


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