View Full Version : D2 Generator speed?
12-23-2009, 10:17 AM
On the D2, D311 engine, what is the gear ratio of the generator shaft to engine speed?
It is driven from the camshaft, which would be 1:2, but I donít know how many teeth are on the generator gear. Iím thinking about running a small 110/220V alternator say maybe 3kw from this drive point as itís not doing anything at the present time.
12-23-2009, 12:05 PM
They all appear to run through a 25 tooth idler with either 20 or 14 tooth generator gears....so if I got my numbers right;) you would get a choice of 1.25 or 1.78 times engine speed.
Crank gear is 25 tooth, Cam is 50 tooth.
12-23-2009, 03:24 PM
Microlink - The parts book tells you the number of teeth on every gear in the gear train .. so it's easy enough for you to calculate the generator speed from a given engine RPM. Just make sure you have the right P/N for the generator and gear, there is more than one generator used and sometimes more than one generator gear, with a different number of teeth, on a lot of the older Cats.
12-23-2009, 04:52 PM
Thanks, Old Magnet and OzDozer.
Iíll pull my generator and see which gear it has on it. How many HP do you think I can safely pull off this location? Iíll size my A/C generator based on a safe load limit.
12-23-2009, 05:49 PM
Largest generator fitted to that engine was 6vDC @ 50A. That is 300W. And, 1 Horsepower=746 Watts.
12-23-2009, 05:59 PM
18a 24V = 432 watts.....not much different.
12-23-2009, 06:11 PM
Even at 50% efficiency thatís only about 1 HP.
The gear train is much more robust than that, however
The cam gear has to be doing what? Maybe 10 HP? The
Marine engine had a fresh water pump on this drive point but
I have no idea of itís load. Seems like the total load on the cam gear
would be the weakest link.
12-23-2009, 10:32 PM
You probably can get away with a GM 10SI alternator that is rated at 12vDC and 65A without any problems. There have been enough conversions that drive the 10SI alternator and no report of gear problems. Which means that you have about a 1HP to 1.5HP load with that alternator when its at max load.
The alternator will have an efficiency above 50%, more likely 85% or so.
12-24-2009, 10:33 AM
I don't want to encourage you in to having a gear train problem but I have occasionally seen hydraulic pumps mounted to the generator drives (specifications unknown) but I'm sure they would exceed the hp of the generator. Depends on how adventuresome you want to get I guess, knowing what the failure consequences would be.
12-24-2009, 12:25 PM
Thanks Old Magnet,
Yes Iíd like to pull 5-7 HP off that spot but the ďfailure consequencesĒ has me spooked. Letís see, the cam gear shatters thenÖÖÖBut the gears are big and after 57 years :eek: still look new, do I dare?:confused:
12-26-2009, 09:48 PM
Every pole in an alternator is a load spike to the drive. The heat treating technology was rather crude back there 57 years ago.
12-27-2009, 05:34 AM
I'd imagine the weakest part of the front gear train would be the key in the crankshaft gear. Even so, I'd expect that the front gear train would be able to cope with around 3-4 HP being drawn off it.
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