Differential steering

[maddox10]

Depends on starter motor, more modern ones could be timed PM motors, but old school starters are series wound.

If you take a series wound starter motor as it comes, and reverse polarity, you also reverse the field of the electromagnets, resulting in net no change whatsoever.

To make a car starter reversing, you need to seperate the field windings and the stator windings, and make sure you reverse the polarity on 1 of the 2.Another issue is that the body is electrified, that to has to be adressed.

Also, car starters are ment for short bursts of very heavy torque production. Not for continious running, and this is reflected in the construction. Very low internal resistance for example.


The Fiesta starter we used in Project One was rated 800W @12V, but could easely draw over 250A , making it to hot to handle in a few seconds.

Next bit of problem. You need a very rare kind of speedo to control it.

All in all, I would suggest using a car starter for weaponpower or such, not drive. I tried, and didn't like the result.
Project II Hex'em, therefor, used a Bosch 750.

[widow_twanky]

I'm just speccing up a heavyweight. the issue would be finding a diff suitable!

Maybe if you looked on ebay for a transaxle for a mobility scooter you would find what you are looking for. (Make sure you get the faster ones, the 4mph ones aren't too good for us!!)

The only problem you have with these is they're 20:1 in a single stage making the input gear quite small. These can break if you run them against a brake which apparantly is the major cause of failure. So it's either a big bag of input gears or Kenny and some tool steel.

http://www.ebay.co.uk/itm/mobility-scoo ... 3a6a67db18

[widow_twanky]

oh and trev had a sort of linear actuator powered thingy powered by a bosch 35W motor (which you get with the car seat when you buy it) on the front wheels of mighty mouse which seems an awful lot less faffing about than using a braked system. Didn't have a really good look at it but might be worth speaking to him.