I am not an electrical expert but if the circuit breaker is tripping this would indicate an electrical fault, either short circuit or contact somewhere due to damaged insulation possibly. Have you given everything a good clean to ensure it is not a build up of dirt and dust causing the problem? Have you tried looking for a circuit diagram online?
The vibration is probably due to the action of the cutter bar, an Allen scythe is just the same. With drive to cutter bar disconnected you should find the machine runs smoothly.
The axle shaft is not splined but does have key in a keyway, it should come off using a hub puller. You can remove gearbox side cover without any parts falling out. Other members with more detailed knowledge will be able to give more information.
I am sure Andy can bring a 56 with plough, Carl has a 35, if you could bring a 5 and 30. I can bring a 50, 220 (or whatever model it is, not entirely sure) and maybe something else which may not be running. I can also bring soil shredder and cultivator frame to go on my 56.
Before starting have you opened drain cock on bottom of crank case to drain off excess fuel/oil, remember to close it again before starting. The shavings hang on the insert that goes in the intake tube see page 8 of the manual which shows how air intake is assembled.
I wonder how many different models we can have attend? 5, 10, 30, 35, 56, 222 etc ??? Also what implements, rotavator, plough, soil shredder, cultivator etc???
Carl SIMAR 35 s/n 350884 was delivered on 12-3-56 to Enfield Highway Co-op Society Ltd, 112 Ordnance Rd, Enfield; details taken from factory records which I am custodian of. Do you have operators manual and parts list for the 35? If not I can supply copy via e mail, drop me a personal message if you need them. The wood shavings are the thin ones used as packing material for plants etc. When you say pot, which part do you mean?