Hornby X04 motor won't start after 20 minutes of runnin

[shildonboy]

I have a Hornby R3704 Battle of Britain loco with an X04 motor, the newer type without felt lubricating pads.  The loco was bought used and was in desperate need of a service.  

 

I serviced the loco and it runs well.  After 30 minutes of running if I stop it the loco does not restart unless you touch the armature windings and give it a lgentle nudge.  You can feel the field magnetisim in the winding so it is not a pick up issue.

 

Any thoughts?

[DCB]

Sounds like the windings might have become detached from commutator.  Mis aligned brushes will cause poor starting, they should be exactly on the centre line  of the armature and quite often are not.  X04 powered locos sometimes suffer from the worm gears winding up as the driven axle is pushed sideways by the worm on starting.  I fit thrust washers where I can to limit sideplay on the worm wheel to just a few thousandths  of an inch.. The Bob is a bit tricky as it is centre axle drive, Ok with Triang wheels but not good of you add Romfords

Edited April 29, 2019 by DavidCBroad

[RedgateModels]

could be very worn brushes too, but my money's on a blown winding.

 

Let me know if you want an exchange

 

http://redgatemodels.co.uk/?page_id=100

[Pebbles]

It seems most likely that the problem relates to heat.  I have comes across a similar problem where after a period a temperature rise results  in a short in the windings. However, It is also possible that arcing - caused by dirt etc - between commutator segments would cause similar problems and is far easier to deal with.  

[shildonboy]

I took the motor out of the loco and cleaned the commutator segments with ASALCO which is a commercial motor cleaner surprising how much gunk came off the thing.  Ran it for an hour last night under no load and it started fine.  Running it again tonight in the other direction again with no load.   After cleaning the sparking at the brushes is almost completely eliminated.  Also running cooler.  The winding connections are all intact - checked at X10 magnification.  I will also remove the brushes and perform a high Q test to see if there is an open or short inside the windings.

 

[Ben Alder]

Going back to my Hornby service agent days i found that it was usually a mix of dirty wheels and clogged commutator gaps. A dig with a scalpel to clear them out and a clean of the brush contact surface and the armature worked wonders almost always. Plus the removal of excess oil that too many had clarted over every accessible point.

[shildonboy]

put everything back together and so far everything runs  smoothly with nice low speed control.  Will see how it holds up after running for a few days