Possibly a slight difference in pivot screw tension, or port hole diameters or positions?
So many variables in a situation like this, but so what if there is a slight difference between the two when running free. Put them both under different loads and they'll run however they need to in accommodating that resistance.
Another way to go might be to put exhaust throttles on both of them so they can be individually tuned and balanced.
Re: "Another way to go might be to put exhaust throttles on both of them so they can be individually tuned and balanced"
I had given that some though because I knew there would be speed differences in all but wide open running, I thought about making a spacer plate in between the boiler mounted steam chest & the boiler, but in the end I didn't think it worth the effort. one way to stabilize/time the running is to have them (drive axles) linked together, & that is the reason for my part #2 engine build (yes, your hearing it here 1st ) this one will have 2 #35's with the axles facing inward & joined by a Jensen #25 heavy flywheel, I'd like to incorporate ball bearings into this model, but that would take some doing as there is not enough extra material on the stanchions to allow for the extra room needed for the roller bearings...needs some thinking on. I had always planned on building both of these from the onset & have all the needed materials on hand, this one shall be called J-42R, I haven't done a build thread for years....but if there is enough interest, I would be willing to start one for my fellow steamers/friends.
