Hornby Mallard

[timgray]

Evening all
My next discussion topic, purchased a non running Hornby mallard in Nice condition with 3 coaches and a tender drive.
Got it running fairly easily it had a stuck brush in motor. Usual clean and oil off it went with its 3 coaches, bit slow I felt.
Its been sat on a shelf for a while 3 to 4 weeks. Yesterday thought it was time for a spin round track. First few times round it was only just moving. Swopped tender unit from city of Nottingham and off it went extremely well. Put original tender back on and after a while It did pick up. So my point is have I got an iffy magnet in my motor or maybe a armature faulty. Your thoughts appreciated. I did check the current draw it is about 400ma

[Bigmet]

That's a high current draw, and it runs slowly compared to one in good nick. Could be friction from a very draggy gear train and/or axles or a binding bearing. Remove the gears driven by the gear on the motor shaft. Does the motor turn freely and easily? Does the tender roll freely on track when the motor isn't engaged? If either of these are a problem, fix it.

If that's OK, then does the motor run faster when given power while not connected to the wheels? If it doesn't and still draws a large current, motor knackered. They do give up, and are not worth the trouble of repairing.

[Mountain]

Sometimes the motors gear retaining spring may not be sitting right. Or it could need the communtator cleaning especially the gaps between the plates.
Whatever it is, I hope you find a solution.

[mossdp]

Oil contamination of the commutator is a common cause of slow running and high current draw. Commutator should be fairly bright copper colour with a few streaks of dirt. If it is near black, it needs cleaning. The slots between the segments need to be clean otherwise they conduct rather than the current going through the motor coils.

[timgray]

Yesterday I thought I would have a look at the mallard motor. One of the brushes was pretty badly worn at an odd angle plus the worn brush was tight in the holder. Comm cleaned two new brushes and springs fitted. Brush holder eased all reassembled with a bit of lubrication. It's now running again, need to check the current draw. What should this be for one of these ring field motors and any thoughts why brush is worn at an angle. Thanks for your suggestions to date. Royal mail TPO to set up today as its raining.

[Bigmet]

Current draw is very variable on these motors, dependent on both the exact design and the condition, as you are discovering relating to the latter. On 12V, 150mA is ideal, shouldn't exceed 300mA in my opinion.

Why is the brush worn in that way? Take your pick from the way it was assembled, part dimension mismatches, deformed or soft spring; and that's by no means a complete list of possible causes.

[timgray]

Thanks bigmet have eliminated 2 as new brushes and springs will check current draw after couple of runs.