360 - mini hypnodisc

[Eventorizon]

The only time I have seen more than one engine joined successfully is here... though its not just as simple as bolting 2 motors together... or even 3!
[attachment=0:118a27qu]napier_deltic_animation.gif[/attachment:118a27qu]
3 opposed piston engines joined together, sharing the same 3 cranks. Used mainly in the 50's and 60's in diesel electric trains.