How do I run a Dynamo as a motor?

[DaveT]

By chance I have a video of me doing exactly this, should help

Thanks for the video clip they say a “picture is better than a thousand words”  so it now becomes very clear what I have to do. 

But, in my case would I Earth the dynamo casing to the positive and join the two terminals together to the negative to prevent reversing the polarity of my dynamos?

Dave

I've run both my spare Dynamos and they rotated in the right direction. 

I then removed the drive gear and connected them to a mains powered electric drill and ran at full speed. 

I then put a voltmeter across the terminals and the reading on one was 7 volts and the other was zero. Would I expect to get more volts or am I doing something stupid?

Without connecting the dynamo to the car setting everthing up and running the car how do I determine if the spare units are knackered?

Dave