Hi everyone,

I have built a fairly professional engine dyno, but I ran into some issues with resonant torsional vibration in the driveline from the engine to the eddy current brake. Now I was wondering how other people are handling the situation.
Here are some specifics about my setup: It's an aircooled 4,7 liter 7 cylinder radial aircraft engine. The whole point of the dyno is to run the engine without prop of course. Now unfortunately my brake has about 2,5 times the moment of inertia of the prop normally run on the engine. The engine manufacturer can't provide a permissible range for prop MOI on the engine, so I can't rely on that to be sure it's fine to rigidly connect them at all (I did it anyway, obviously). He also can't provide the lumped MOI for the rotating assembly of the engine, so I can't do a torsional vibration analysis on the shaft. I'd say this situation is pretty average for engine dyno operators.
Currently I have a fairly long shaft (about 1m / 3ft) connecting the engine to the brake and encountered torsional vibration around 1300 RPM (operating range is 800 - 2400 RPM). I have a list / plan on what to change mechanically to make the entire situation better (shorter more rigid shaft manly). That pushes the resonant frequency higher, but I can't be sure that the original resonance I encountered wasn't some higher order and if I push that out the top of the RPM range a lower order doesn't come in the bottom.
I also want to measure and preferrably monitor the torsional vibration in the future, but that's not quite straight forward. Preferrably I would want to put strain gauges and an arduino on the shaft, but transmitting something off a spinning shaft at 2000 RPM isn't that easy (I haven't tried, but apparently it might be difficult).

So my questions:
what are the experiences of other engine dyno operators/builders with torsional vibration in the driveline and how do you handle it?
Does anyone have experience in either measuring or live-monitoring torsional vibration on a dyno?