> is there any information about combining gearboxes. If two engines
> power say one rotor how can this be acomplished without total
> synchronization of the engines?
The strength of the shafts automatically "synchronizes" the engines.
The engines cannot turn at different speeds. Sort of like how the
crankshaft on a multi-cylinder engine sychronizes the motions of the
seperate cylinders/pistons.
This does not guarantee that each cylinder is putting out exactly the
full percentage of power expected, and this can lead to some rough
running, but synchronization does not need to be perfect, only good
enough that the resulting roughness is not destructive. Consider
multi-cylinder engines with more than one carburetor. Adjusting carbs
to "sync" is im****tant, but does not have to be perfect. There is
usually a "balance" tube connecting the manifolds just downstream of
carbs, to aid this.
In completely seperate engines one can gang the throttles, and monitor
manifold pressures. Engines will run at same rpm (guaranteed) though
not necessarily at exactly the same power output. It is also possible
to put torque sensors on each engine and diagnostically monitor the
results. This can ensure going to full (or at least greater opening)
throttle immediately upon loss of one of the engines.
