Austin Seven Starter Motors 1929 - 32
- with thanks to Crankhandle - the newsletter of the Hereford A7 Club
- Ray Moses
- Download this article here
These motors are the ones that replaced what has become known as the ‘bacon slicer type’ and are similarly mounted inside the car over the gearbox. They are becoming rare and are expensive at Autojumbles.
All is not lost however. If yours fails a cheap replacement for armature and field coils can be found in Ruby type starter motors. The parts that are unique to the 29 - 32 type are the end plate carrying the brushes, the bendix drive gear assembly and the terminal on top of the main body. The main difference to the Ruby type is that the earlier rear mounted motor rotates in the opposite direction.
To convert a Ruby starter you need the earlier end plate and brush assembly. The orientation of this is critical so note the position in comparison with your failed earlier starter. You will also need to transfer the bendix drive. The Ruby one designed for opposite rotation is needed for a front mounted starter.
Some of the 29 - 32 starters used a ball bearing at the drive end flange. Most of this type I have found to have cracks in the bearing housing, so it is best to use a Ruby type that has a plain bearing and is more robust. The mounting holes have the same spacing.
The terminal on the body is a button contact on the Ruby type and a threaded terminal on the earlier design. The button can be drilled and tapped with care or a suitable brass bolt modified. Retain the insulation to isolate the terminal from the main body. Field coil leads may have to be extended to match the earlier end plate and brush assembly. If the field windings are sound in the original motor the body can be used with a Ruby armature.
The Ruby armatures seem to be more robust than the earlier type and will withstand regular use at 12 volts. The earlier type tends to fail due to a breakdown of insulation between the windings and the shaft.
Thankfully there are plenty of Ruby type starter motors around for reasonable prices so adapting these for earlier cars is not depleting the stock of Ruby type spares by any significant amount.