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Building a Mercedes powered generator


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  #1  
Old 04-20-2010, 10:20:57 PM
Johnny Uncool Johnny Uncool is offline
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Default Building a Mercedes powered generator

I pulled the diesel motor from a 1980 Mercedes 300D that had a bad transmission. I had been running the car on WVO. I am looking to build a generator set with it and I was hoping for some insight / advice.

The engine is rated at 77 hp at 4000 rpm. If I assume a direct relation between hp and rpm, that should give me just under 35 hp at 1800 rpm, and about 23 at 1200 rpm. This should allow me to drive a 26 kW and a 17 kW generator respectively (If anyone has better info on this please let me know). My plan is to use a belt drive and for now run the engine at 1200 rpm to help minimize the noise, and because initially I will not need the higher output. I would use a 1.5 to 1 pulley ratio to get the 1800 rpm at the generator. I am thinking of buying the larger generator to keep my options open in the future. Will running a 26 kW unit with an engine putting out 23 hp work out?
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Old 04-20-2010, 10:33:18 PM
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Talking Re: Building a Mercedes powered generator

You would only get about 20 Kw Electrical, at a Maximum, out of a 23 Kw Shaft Input. You will have to build yourself some kind of Governor, to control the Output Rpm Steady, while allowing the engine to provide more power and torque to the Genend.
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Old 04-20-2010, 11:19:45 PM
Wayne 440 Wayne 440 is offline
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Default Re: Building a Mercedes powered generator

If I read this correctly the OP estimates 23 horsepower at 1200 rpm.
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Old 04-21-2010, 12:36:07 AM
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Talking Re: Building a Mercedes powered generator

That is True, HOWEVER, There are still loses between the Shaft Horsepower, here expressed in Kw, and the Electrical Kw that can be extracted from the Genend. Friction, and Heat, mechanical, and Resistance Loses in the Stator Windings. All these can add up to say 10%, or so easily. You NEVER get 100% energy conversion.
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Old 04-21-2010, 01:06:35 AM
Ken Karrow Ken Karrow is offline
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Default Re: Building a Mercedes powered generator

I'm not at all familiar with the engine you are dealing with, but with gasoline engines, particularly ones use in autos and trucks, I feel you are shakey ground assuming a direct relationship between rpm and hp. Reference governor item. West of the 100th meridian there were belt drive governors in common use when converting auto engines to run irrigation pumps. However I can't remember what was used for a rev limiter in case of a broken belt though the load of pumping would limit revs to some extent. In a generator application a broken governor belt would do drastic things to cycles and possibly voltage depending on your control system. Ken
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Old 04-21-2010, 06:07:12 AM
armandh armandh is offline
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Default Building a Mercedes powered generator

those 4 cycle auto engins had plenty of torque
your hp at 1800 rpm might be a bit low but i doubt proportional
do you remember what the engine RPM was in high gear at 60 MPH
that is where i would tatget the belt drive ratios

PS
get the biggest gen you think it will handle or you will need
its hp load is proportional to it's electrical load

again the guy that used an after market auto CC

http://www.youtube.com/watch?v=Baq84lpsM1Y

PPS noise level is also proportional to load above the no load but correct HZ level

the more load you apply the louder it gets without changing pitch [hopefully]
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Old 04-21-2010, 11:01:39 AM
K D Redd K D Redd is offline
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Default Re: Building a Mercedes powered generator

With roughly 2 HP needed per KW output, your 35 HP at 1800 RPM would produce about 17 KW, 23 HP at 1200 RPM would produce about 11 KW. That said, I am one who thinks that you should have a bigger generator head than the engine can drive. I would rather see Black Smoke from an overloaded diesel engine than various colors of smoke from fried stator or rotor windings. If you could find a 20 KW 1800 RPM head for your 3 liter Benz that turns 1800 RPM would be , I think, about right.

Kent
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Old 04-21-2010, 05:27:42 PM
Jim Rankin Jim Rankin is offline
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Default Re: Building a Mercedes powered generator

I would advise against belt driving direct from a crankshaft mounted pulley. You need a pillowblock bearing on a short shaft to at least split the load between the PB and the rear main bearing on the engine. Put the pulley as close to the bearing as possible.

If you want to try it, I would go with a toothed belt or chain drive instead of a V-belt drive. The type of belt I would use is a Gates PolyChain GTor equivalent. A multiple row chain could also be engineered to run in an oil bath. It would take a bit more to do that compared to the dry belt.

http://www.gates.com/sync/index.cfm?...ocation_id=742

Direct drive off that engine at 1800 rpm with a coupling would be much preferable since you have to have a 2 bearing generator to do it the other way anyway.
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Old 04-23-2010, 12:47:29 AM
Ken Karrow Ken Karrow is offline
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Default Re: Building a Mercedes powered generator

Any chance the bad transmission was a manuel tranny and direct was still functional? If so you could run a prop shaft to a pillow block as per Jim Rankin and put the pulley or sprocket aft of the pillow block. Second advantage is that you could declutch while starting the engine so the starter would not have to crank the drive and gen head mass. Ken
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Old 05-02-2010, 12:01:40 PM
jdunmyer jdunmyer is offline
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Default Re: Building a Mercedes powered generator

Here's my VW Diesel powered genset project:

http://www.oldengine.org/members/jdunmyer/genset/

I try to describe the various issues and what we did to handle them.
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Old 05-13-2010, 08:55:05 AM
BHath BHath is offline
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Default Re: Building a Mercedes powered generator

Why waste all that HP? Get you a gear box run the engine 3600 rpm and drive generator at 1800 rpm. Generac does it alot. They will match up the HP and torque of an engine then get a gear ratio to drive gen at 1800 rpm. This giving them the best performance of HP to Gen size. Well just another thought of how to get it done. Really just depends on what you have an how deep your pockets are. Don't forget automotive governors might not be to great to keep the frequency steady. One trick some governor people do is to wide open the throttle lever and govern the speed using the shut off lever. I like the Woodward DPG 2200 series governors. Set them up with a laptop. Get the best performance. Trial and error if you dont have something to start from. Good luck.
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Old 05-13-2010, 03:44:59 PM
Wayne 440 Wayne 440 is offline
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Default Re: Building a Mercedes powered generator

Well I will comment on the elephant in the room if no one else will. IMHO, saying that "Generac does it" is a condemnation rather than a good reason to do anything.

Generac is also known for running fan drives thru radiators, thinking belt drive was a good idea in small units, changing engine suppliers way too often (and until recently making it all but impossible to find out who actually made the engine), putting transfer switch control logic in the generator housing, changing wiring/specification etc. and failing to update the diagram/manual.
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Old 05-13-2010, 08:06:48 PM
K D Redd K D Redd is offline
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Default Re: Building a Mercedes powered generator

ANY GEAR BOX introduces power losses in to the system. BELTS are the most efficient way to transmit POWER IF you need a speed change. If NO speed change is needed direct coupling would be the most efficient.

Kent
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Old 09-01-2019, 01:00:07 AM
rdbates1 rdbates1 is offline
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Default Re: Building a Mercedes powered generator

Not to latch on to a really old thread but I've been thinking about using an OM616 diesel too. I need 5kw to power a grid tie inverter and could add another 5kw to supplement heat for a boiler but that still only puts the needed hp at approximately 20hp. The hp curve shows 20 hp at 1500 rpm. Would this be enough of a load to avoid wet stacking especially with straight WMO and any idea of fuel consumption? The OM616 is supposed to be a very long lived engine but I'd certainly be open to ideas for other engines. I've looked high and low for a Changfa S195 but can't find one.
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Old 09-01-2019, 02:57:52 AM
Vanman Vanman is online now
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Default Re: Building a Mercedes powered generator

Instead of using electricity for supplemental heat at maybe 10 or 15 percent efficiency, I'd use waste heat from the engine as the primary source of heat at virtually infinite efficiency (heat would otherwise be thrown away).

I would say that, as long as the load is significant for the particular operating speed, the engine ought to do fine.

Keith
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Old 09-01-2019, 01:06:59 PM
rdbates1 rdbates1 is offline
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Default Re: Building a Mercedes powered generator

I'm planning to use the waste heat from the water jacket and also run a marine style manifold to pick up exhaust heat. My thought on electric heat was just to load the engine a bit more.
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Old 09-01-2019, 01:08:04 PM
rdbates1 rdbates1 is offline
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Default Re: Building a Mercedes powered generator

Also, any estimates on fuel consumption for this sort of setup?
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Old 09-01-2019, 06:28:29 PM
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Default Re: Building a Mercedes powered generator

Belt drive governor's used on combine's are pretty scarce these days. You might still be able to find one though at an affordable price. These governors are made by Pierce and Hoof. https://hoofgovernors.com/

Not sure about rev limiters? I would have to look into that myself.

Another approach would be electronic governor. There are several different types and styles of these Chinese governors. https://usa.banggood.com/ESD5500E-Sp...SABEgJaoPD_BwE A bit of research is needed if interested in this approach.

Robert
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