Why has my Hornby Class 700 motor failed so soon?

Bought new and after a relatively short period the engine would not run due to a failed motor. A new motor was purchased from Peter's Spares, who had a vast stock of them, possibly indicating a common fault.

So why did the original motor fail?

I needed to gain access to the inside of the motor can to find out. The four arrows in the photo show the cleaved flaps that were twisted away to allow rear panel removal. I used electrical cutters to hold the boss and lever off the panel from the can.

Attached to the rear panel are the armature contacts. The contacts are four extremely fine (thin) metal fingers. Some were deformed from both the feed and return and had moved away breaking electrical contact with the armature.

I carefully bent the fingers back to a position of likely contact and reassembled the rear panel.

Applied power and voila! the motor ran. I cannot recommend this as a fix as the fragility of the design will undoubtedly cause it to fail again.

As to the new motor installation I shall have to run the engine only for special occasions and hope this will extend its life.

Postscript

I wondered if I could strengthen the contacts. With a lot of fiddling I was able to push the electrical contacts out of the housing. I then lightly soldered a strip of thin phosphor bronze strip to cover the fingers and reassembled. This has provided more robust and worked perfectly well. I could not reinstate the cleaved flaps to hold the rear panel in place, which is no big problem as the motor is held in the engine such that the rear panel cannot come loose. So, now I have a spare motor in case the other one fails.