Max rpm for D3400

hello smf52 ,in the rack setting books i have ,it show max revs @1650 for d3400 industrial engine ,the d311 @1800 revs ,bruce oz

My book shows for 3 3/4 bore low idle 600 rpm high idle 1650 rpm and full load 1525 rpm thats from book printed in 1940 but they change HP of the D2 many times thru its production and many only involved raising the RPMs

There is no indication that I can find anywhere, that a D3400 can be run at 1800 RPM. I'd say you do so, at the risk of engine destruction. Remember, this is a low tech engine built in the 1930's, and which was obsolete by 1947, when it was replaced by the D311 .. which engine, WAS built, for higher RPM.

The problem that I see, is that the engine has to pull 1850-1875 RPM to sit on 1800 RPM under moderate to heavy load, to be able to generate 60Hz current. Engine RPM droop below 1800 RPM will see variations in frequency, voltage and amperage that could damage electrical equipment it is driving .. and generate more alternator heat as amperage increases, via lower voltages.

You could possibly pull these kind of RPM's, but it would need to be at a low HP rating (maybe 25 HP?), and not under continuous use. "Intermittent" ratings allow for temporary overspeed or higher HP output, but "Continuous" ratings demand a lower RPM and a lowered HP output. In my experience of running gensets, they run flat out for long periods.

smf52: You need to move to Europe or other countries that use 50 Hz power. Your D3400 genset would work well at 1500 RPM. Another option is to belt drive a 2-bearing generator using your D3400 with PTO mounted pulley. Generator could be mounted below, above, or to the side of the crankshaft centerline.

If a belt drive was used, it would need to be structured so that the engine driveshaft and the generator shaft were supported on the ends by a bearing.

"Overhung" (unsupported) driveshafts and generator shafts are undesirable, because of the excessive load placed on the engine rear main bearing, and on the generator front bearing, by the belt drive.

I agree trying to run the D3400 at 1800 rpm for any length of time is not a good idea. The PTO setup would be nice but finding that unit is unlikely.