Motor slung
Motor drive hung on the barrel
Now the reason for the length & bend of the motor bracket should be apparent!
The angle of bend was determined experimentally, so the motor and axle axes would align, and the plate would hang parallel to the end of the tank!
The axle shaft was cut to length so that the hanging plate was as near the end of the tank as possible.
The motor drive just "drops on" to the end of the axle.