I have the opportunity to get a Detroit Diesel 6-71 marine generator that is rated at 75kw. This is a 2 stroke engine that operates at 1200 rpm. It seems like it would be a nice generator to grab, as it would require limited run time. Does anyone know how you would you cool it? Another obstacle is dealing with the 3phase power. Any input would be helpful.

1200 RPM sounds slow to me. Those old two strokes liked to run near the top of their RPM range to put out power. We pump water with one in an old truck frame that still has the radiator and fan.


http://www.youtube.com/watch?v=rhR10JUbi3U

Eurcab

-three phase power should be no problem, just use two of the three termanals for 220v single phase, same as the pannel in your house. Tom

Tom, thats ok if you're dealing with North American 3-phase. If Eurocab is in Europe, different story. The voltages are usually different.

I believe the normal operating rpm of the 71 series in genset applications was 1200-1400 rpms, as far as cooling, the non marine versions had a conventional radiator water pump setup, water pumps should be widely available, and any decent radiator should work fine.

quote:

Originally posted by Biotom:
Eurcab

-three phase power should be no problem, just use two of the three termanals for 220v single phase, same as the pannel in your house. Tom

Wrong Tom, to get single off three you use only one phase and a neutral, (edited to add) you are right if you want 240 single, 120 single would be as above.

fab
-you are correct, 220v is 2 phase. I use a 10 hp 3 phase motor running on 220 to create 3 phase for my lathe. Tom

quote:

Originally posted by Eurocab:
I have the opportunity to get a Detroit Diesel 6-71 marine generator that is rated at 75kw. This is a 2 stroke engine that operates at 1200 rpm. It seems like it would be a nice generator to grab, as it would require limited run time. Does anyone know how you would you cool it? Another obstacle is dealing with the 3phase power. Any input would be helpful.

1200RPM is waaaaay to slow for a Detroit. They don't call them Screamin' Jimmys for nothing. For continuous operation with a load on the engine, you have to have at least 1800 rpm. Lugging one of these Detroits will kill them

Is this the inline 6 or the 6V-71? The inline engine is very durable. I would cool it with a proper radiator from a truck salvage yard. That way there is no worrying about cooling capacity. Run this engine with a proper thermostat or you will have nothing but problems with oil longevity and oil consumption. When under load, diesels pump out a lot of heat. Diesels cool off when left to idle. Also don't let the 6-71 idle for long periods of time as fuel droplets can accumulate in the cylinders called 'wetstacking'.

Detroits are smokey under load so oil consumption can be hidden from diagnosing a potential consumption problem, just keep an eye on how much oil is used between oil changes (about every 50 hours, 100 hours for the filters). Detroits are very durable, but you have to know how to run them right.

Eurocab
Wow, after reading all you folks posts I wasn't sure I could ever be of any help....but you are in my alley here.

The generator end of the power unit determines the RPM the engine will run at. 1200 RPM was the standard for 60 Hz gen sets several + years ago. I love them. They are much quieter and last much longer. The next step in RPM is to 1800 for 60 Hz then on up to 3600 for the newer cheaper units. Fewer poles in the generator means it has to spin faster, but it is cheaper to build.

fuelfarmer
You're right it is pretty slow. Thus the 75 KW. IIRC the 1800 RPM gen sets with a 671 non-turbo were about 110 KW. The nice part is that piston doesn't go near as far in an hour at 1200.

For European use they just slow them down to get 50 HZ. That one would turn 1000 RPM for a 50 HZ setup.

Anyway, Eurocab, this vintage should be a 12 wire generator. If you look at the tag on the generator it may show wiring diagrams for various voltages. If the wire numbers in the diagram (or if you open the unit up and look at the wires coming from the generator) are for 12 wires (there may be two smaller wires called F1 and F2, ignore them for now) it can be wired to any configuration to give you three phase, single phase, dual voltage etc.. Depending on how it is wired now it may or may not give you the single phase voltage you want.
See:

www.marathonelectric.com/generators/iomManuals.jsp

The ZIG ZAG 1 phase on page 10 may be the way you want it.

Whatever you do don't rev the engine past the RPM rating for the generator end. It will throw the copper in the generator all over your yard.. :-)

If it still has the marine heat exchanger on it you could recover the waste heat from it to do your BD. It could also have a wet exhaust manifold on it which allows even more waste heat recovery.
Hope this helps.
Tom2

Wow, thanks a lot for the information. I am getting excited about this. I was thinking that instead of wasting the third leg, what if you had a battery bank to store the electricity on the other leg? Would that work? Maybe use an inverter to power the house after the battery bank is full? With 75kw it shouldn't take too long to load the battery banks and then shut her down.

quote:

Originally posted by Eurocab:
Wow, thanks a lot for the information. I am getting excited about this. I was thinking that instead of wasting the third leg, what if you had a battery bank to store the electricity on the other leg? Would that work? Maybe use an inverter to power the house after the battery bank is full? With 75kw it shouldn't take too long to load the battery banks and then shut her down.

Hahaha. Sounds like my place now. I do exactly that (the inverter and batteries) but only use a 12 KW for backup when running machinery or when it clouds up for a few days and it is seldom loaded much. What ever load you can come up with helps. It will slobber more under light loads. 75 KW is enough for several houses.

The advantage of using all phases when it is wired for three phase is smoothness. Unbalanced loads on a generator cause vibration. For single phase the Zig Zag is supposed to keep unbalance to a minimum if I remember correctly.

It may be from the WWII era. They are reliable but messy :-) the engine has an airbox that acts as a manifold for the blower to scavange exhaust out of the cylinders. Oil collects in the box so they put a drain in the bottom of it that stays open to blow the oil out on whatever it is aimed at. Plug the hole and the box will build-up oil until the engine starts lapping it up and then it takes on a mind of it's own and runs away.

Unless you like old iron (like me) you can probably find something a lot quieter, cleaner and easier to move around. A 1200 RPM generator end uses a lot of copper and they were not afraid of large castings back then either.

If you do get it and have questions I'd be happy to help. Just think, you could stick it in an electric bus and have the worlds heaviest hybrid. Tom2

akwrench,
I was thinking that a 75kw generator would not take 230 plus HP. That engine should run a looong time at 1200 RPM. The generators that we have are for standby use and run 1800 or 3600 RPM for only a few hours per year.

The inline 6 71 we run, maybe they all do, has covers on the side of the block that can be pulled quickly. Then you can see the pistons through the intake ports. I plan to take a peek after we run a bunch of SVO to see if the rings look OK.

Fuelfarmer
You are right. They didn't have near that kind of HP back then and definately not at 1200. They ran a lot of them that way. A 2 cylinder version of the 71 series was used in railroad cars for years on the refrigerated box cars.
Great pics. That is the airbox that the covers go on. You can see how easy it is to check ring,piston,and liner wear. you can use an awl or small screw driver to push on the rings to see if they are still free or to see if they have collapsed from overheating.
The earlier ones also had only two valves per cylinder. The N series has 4. Your pics are of an N series I believe. IIRC the low blocks (early ones) had round ports. Testing my memory here. Tom2

Detroits can be a bit of a fuel pig to operate, but they're so stump simple to operate that no one seemed to mind the fuel economy until fuel prices started to rise.

The earliest blocks that I ever saw were 70's vintage and had the rectangular ports. I think only the very old engines had round ports.

Just don't lug that engine and it will last a very long time.

It will be a little loud, even at 1,200 rpm. Some like the sound and some don't.

Fun project, keep us posted.

troy

I thought those 6 71s were fuel hogs also until my nephew did a little testing. I think he was getting around 4 gallons per hour at a reduced load. Under more load he is burning in the 6 to 8 GPH rang. If you crank them up they will use some fuel and put out some power. Even now it takes fuel to make power. For their time I think they did OK.

Anybody know what the max safe water temp is to run a 6-71?

If you watched the video linked in a previous post would you like to guess the RPMs. Turn the volume up and hold the speakers up to your ears.

Here is the link.

http://www.youtube.com/watch?v=rhR10JUbi3U

Check out the Detroit Diesels on this site http://www.emerson2-71gm.com

quote:

Originally posted by bburner:
Anybody know what the max safe water temp is to run a 6-71?

173 F is the highest temp thermostat I see listed but I ran them at 190 on a marine application with Amot valves and had no problems. Actually I've seen them a lot hotter than that from various situations. ( like from a loose nut behind the wheel ). Tom2