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  #1  
Old 08-30-2004, 12:40 PM
Diesel on the brain
 
Join Date: Nov 2002
Location: Upstate Virginia
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Mercedes diesel as a genset engine

First, stop laughing at me

I'm always sitting around thinking of dumb ideas, and I've come up with another one. It involves mounting a 240D engine on a cradle and couple it to a genset head (or two).

The motivation is twofold:

A house that's all electric, including the well pump (480' down) running on 240 with two 30amp fuses. That would require a large generator - one expensive enough to make it not affordable to said homeowners.

A 240D engine running is less than the cost of a cheap diesel genset, and the engine and genset head are less expensive than a decent diesel genset.

The real question is about the governer. A friend of mine has a Unimog with the throttle pedal connected to a governor not to the normal throttle on the injection pump. This seems like what would be needed. Set it at 1800rpm (or something else if the genset is geared to the engine somehow) and then use the governer to keep it at that speed.

How doable is that?

How dumb of an idea is this?

I expect that the engine could have pleanty of muffler installed on it, and a sound-deadening cabinet (like the moderately priced home gensets come with) installed around it. Space really isn't a concern.

-Tad
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  #2  
Old 08-30-2004, 01:41 PM
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I am thinking about doing this with a DC welder and air compressor and generator..... So I think it is a pretty good idea...
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  #3  
Old 08-30-2004, 02:25 PM
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Beleive it or not, there are commercial Mercedes gensets available currently using the basic 603, with some variations, almost the same as in the early 300SDL and 300D. They may have offered other earlier MB diesels, at some point of time in the past!

Last edited by sarafin; 08-30-2004 at 03:00 PM.
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  #4  
Old 08-30-2004, 02:49 PM
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How about an old MB reefer engine? There should still be some of those around and they should already be set up to run at a constant speed. The main problems I see with this over an auto engine is availability of parts and if it is powerful enough.
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  #5  
Old 08-30-2004, 02:55 PM
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Automotive engines have different characteristics than industrial engines which would be better suited to this purpose. Power curve for one, governor another. Your first challenge would be to find or make adapters to bolt the units together. Industrial engines have standard SAE bolt patterns.

Looking for ways to exhaust the supply of spare parts for these cars is not my favorite topic.
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  #6  
Old 08-30-2004, 08:05 PM
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One of the main problems with using an engine from a car is how the power will be transmitted to the genset head. It is not as difficult as you would imagine but it will require some engineering. Your first option is to drive the gen head with belts. This is convienient because sheaves and belts are available in about a billion different combinations down at your local industrial power transfer supplier. Get a look at the master catalogue from Browning and you will be amazed at the options. The problem with belts is that a plain bearing crankshaft is not designed for large side loads from a big belt drive setup. It will literally pull the crank in contact with its bearings and bad things happen. The way around this is to use a flexible coupler. A machine shop can modify a flywheel or make you an adaptor to mount the coupler on the engine. The flexible coupler drives a jackshaft mounted in big pillow block bearings. The drive sheave is mounted to the jackshaft and the pillow blocks take the side load. The other option is to direct drive the gen head with the flexible coupler. I think the belt drive would be preferable as the ratios could be fine tuned to spin the gen head and the engine at their most efficient speeds. This sort of project is not all that difficult if you know how to weld and are a decent fabricator. I have built and worked on systems very similar to this for homebuilt hovercraft and they work very well with plenty more horsepower than the MB engine will provide. Regarding the control of engine speed, the simplest aftermarket cruise control would work fine and be very easy to adapt. RT
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  #7  
Old 08-30-2004, 09:48 PM
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Check out either the Harbor Freight or Great Northern catalogs. For $1,400 you can get a 20kw generator, the electrical head and the couplings to run it off a tractor pto. At full load these units require about 40 hp but then one usually never runs a gen set at max. These gens could easily be run off a car Diesel engine and I bet any governor assembly from a Diesel welding machine could be adapted to the set.

Check Diesel welding machine repair shops for rigs with burned out gnerators. They often have good engines that could be coupled to the above generators.

I have a 20 kw Yanmar Diesel with a Lima generator for emergency hurricane power-I live on the coast near Corpus Christi. I have a 3,500 sq. ft. house with 8 tons of ac. The gen set will carry all this load and supply my neighbors on either side with power. It uses about 8 gals. a day under half load.
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  #8  
Old 08-31-2004, 10:39 AM
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What about leaving the transmission on to select the best speed?
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  #9  
Old 08-31-2004, 12:10 PM
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Leaving the transmission on is a great idea....
It is just one of those things you would not tell people on this forum you had done... you would constantly be getting tempting offers to buy it.. LOL

Another possibility is using a double roller chain to get your gearing up... ( know of any laying around from that last engine rebuild ? LOL )
This takes away the excessive side pressure mentioned with the belt drive.... even though with ENOUGH belts ( sufficient friction ) I think the side friction would not be much of an issue...
Another possibility with a multisheave arrangement is to place a counter load 180 degrees from your generator...alternate the belts... left and right of the rear bearing...
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  #10  
Old 08-31-2004, 12:28 PM
Diesel on the brain
 
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Location: Upstate Virginia
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I thought about the transmission, but I don't think that it will help much. 1st gear for instance would speed the engine up in relation to the generator head, which isn't what I'd want. The 240 engine should have enough HP at 1800rpm to run any genset that I could find. Running the engine faster wouldn't really help me I don't think. 40hp at 1800rpm shouldn't be a problem.

-Tad
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  #11  
Old 08-31-2004, 12:35 PM
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space isn't a concern? How about getting a rusted out 240D and mounting the generator in the trunk? Direct the rear end of the driveshaft to be just above the rear differential and mount an old diff bearing and plate to the trunk floor. Connect both the gen and the existing diff to the driveshaft with clutchable belts or chains. Use existing cruise control. Now, you would have a MOBILE mercedes generator.
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  #12  
Old 08-31-2004, 12:50 PM
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With a transmission you could put it neutral for just engine or generator servicing. If you had a DC generator you could change polarity by putting it in reverse. And if you had an automatic it would downshift under load, and it would run through the gears when you started it up. What a toy!
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  #13  
Old 08-31-2004, 02:10 PM
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Leaving the transmission on helps in that you now have a way to keep the clutch... and it gives you an easy way to connect at the tail section.... the same way the driveshaft connects...and disconnect easily compared to some systems....You would probably use 4th gear... but in my case wanting to run an air compressor or other hydraulic pumps... ect... it it sometimes advantageous to have other speeds available without getting out of the proper torque curve for the engine....
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  #14  
Old 08-31-2004, 10:59 PM
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What? Me Worry?
 
Join Date: May 2003
Location: New Mexico, USA
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Question autotrans?

I have a 617 engine with auto trans from a 80 300 SD.
I was going to take off the trans and connect a generator head to it.
Would it be better if I kept the trans on it and connected it to the gen head??
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  #15  
Old 09-01-2004, 07:04 AM
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I would not personally keep an auto trans on something as important as a Generator.... I don't know how the shifting up to high gear would be engineered.... since it depends on vacuum , throttle position and perhaps also load.... as compared to simply sticking a manual trans into the proper gear and forgetting it...
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Old 09-01-2004, 07:04 AM
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