old motors and magnets

QUOTE (Mike H. @ 27 Nov 2008, 15:53) <{POST_SNAPBACK}>.. are these new 'super' magnets being advertised any good? I have a lovely old Wrenn, Lyme Regis, which is perfect in every way but a bit slow. I actuially bought one of these new magnets and it did get a lot better but am I risking anything?
The greater risk is in running a motor with a weak magnet. If you dismantle an open frame motor to the extent of taking the magnet out of the magnetic circuit of the pole pieces and armature it often will weaken the field. With less magnetic field, there will be greater current flow through the motor windings, this can lead to overheating of the motor and ultimately a burn out. The only significant problem from installing a replacement magnet with higher field strength is if the bearings are worn sufficiently for the magnet to be able to pull the armature off centre into contact with a pole piece.

QUOTE (Lord Castellan Creed @ 28 Nov 2008, 01:07) <{POST_SNAPBACK}>Sometimes slow is better, as I have fast ones that are not very good. does the motor run by an electromagnet? If it does maybe the coil either end has uncoiled.

***DC motors in common brands always use permanent magnets. All DC motors use the permanent magnet on the frame to repel the field created by the windings of the armature, with each "pole" being an electromagnet.

Loco's with weak magnets simply become very weak and as 34c said, they draw more current than is healthy. I learnied this the first time at 5 after disassembling my "duchess f Montrose". Fortunately we were living close to Liverpool so a vist to Binns Rd service dept helped out and re-magnetised it!

When locos have weak magnets they will usually rev quite responsively / happily when held in mid air but when on the track are sluggish - they may even lack the power to even pull themselves along properly.

Adding the correct NEO magnet will improve motor efficiency and improve running in all old dublo/wrenn locos.

Remagnetising is very possible - Modelspares offer this service very cheaply in UK.

Richard