starter motors
First of all you your right my figures were a little high but considering there's no real rating on a starter motor and never has been to my knowledge it would be a little difficult to quote an actual horsepower rating. I was simply trying to make a point that they would not be suitable for any other use.
Also you can't use the same math with starter motors that you use with standard motors, it doesn't work because of the way the motor is made internally and its intended use. A normal motor is designed to be used for extended period of time at a certain load and RPM. These motors or designed to basically self-destruct.
As far as reversing starter motors yes, it's easier to reverse motors with permanent magnets than motors with a coil. In order to reverse a motor with a coil you must either reverse the polarity of the Armature or stater but not both.
Because you cannot change the polarity of a permanent magnet, all you would have to do is change the polarity to the motor itself.
A dynamo or generator can be used as a motor but because of the brush alignment they are normally very inefficient. The size, weight and current draw of these motors versus the power they would produce would probably make them unsuitable for your use.
Even on alternator can be used as a motor if you want to do some Elaborate electronics to support it. An alternator woodwork much like a stepping motor. Of course you would have to strip the diodes and regulator out first.
Why don't you try going to some of the surplus stores on the Internet such as (
www.surpluscenter.com)or even (eBay) you might find what you need their for the right price. and I'm sure there is plenty of other places as well.
my point is it is morally better to spend an extra $5 or $10 on the right part then trying to make the wrong part work and maybe going through several different parts before you get one to work.
sam963258