Soft mount, hard mount the debate goes on uselessly of course. The engine doesn’t care but everyone seems to think it does. Horse pucky. Take a look at engines today some are soft mounted many are hard mounted. Hard mounted dirt bikes produce a ton more internal forces than any airframe could. Your lawnmower shakes, vibrates and bounces over uneven ground without a problem. Soft mount every car, truck etc is soft mounted. Soft mounting simply reduced engine oscillations and noise to the frame/passengers in a vehicle mostly for comfort.

Some RC exhaust manufacturers will not warrantee their exhaust systems with a soft mount.

My earliest bike was a 1956 Arial Red Hunter it and most bikes I have owned since have all had the engine hard mounted. Norton came along with their feather bed frame (soft mount) it reduced some of the engine oscillations to the rider they claimed better comfort. It had nothing to do with engine durability or longevity. I have never heard any manufacturer claim as much.

If you really think about it does it matter where the oscillation occurs? It could be between the engine and airframe but some will be transferred to the airframe anyway.

If you hard mount it the oscillation will occur between the landing gear and ground when not flying and between the airframe and the air that surrounds it when in the air. In the latter cases the airframe will absorb and dissipate much of that vibration. In our application is comfort a consideration? Absolutely not so the only consideration is the effect on the other components of the airframe. Balance the prop and spinner and I doubt you would see any problems unless the motor itself was badly out of balance or had a bent crank from a previous ground strike or crash.

Get real look around and see how many are hard mounted vs. soft mounted.

In my opinion balancing your prop/spinner is more important than whether your engine is hard or soft mounted.

Dennis Pratt