Here is a neat little presentation on the DC motor runaway:
The one I saw was on a winch drive with a compound wound motor. The supply to the shunt field failed. Slightly more complicated.....the shunt field had two different voltages. One for high torque low speed and the other for low torque, high speed. It was in this latter mode that the shunt field supply failed. Not only was the motor in a bit of a state, there was a tangled mess of wire rope.
It was quite an interesting application, as it happens. It was a tin mining dredger in South East Asia. The dredger floats in a man-made pond* and a bucket elevator digs up the stuff at the bottom of the pond. The dredger moves from side to side on the pond and that's where the winches come into action. There are two forward and two aft on opposite sides of the vessel. They are anchored to the left and right hand banks of the pond. One set, forward and aft, say on the left had side, winches in pulling the vessel towards the left bank. Those on the opposite side which out (render). The bucket elevator thus works across the face of the excavation rather like the operation of a milling machine - just on a little bit bigger scale.
*Calling it a pond doesn't really convey the scale of it or anything else.
I was hoping your link would take us to a live demonstration.
If Billy Idol or John Denver is on your Ipod go and re-evaluate your life.