Weak magnet?

Post Reply
User avatar
RSR Engineer
Posts: 81
Joined: Sun Oct 07, 2018 11:18 pm
Location: Freistaat Bayern
Contact:

Weak magnet?

#1

Post by RSR Engineer » Wed Apr 10, 2019 11:33 pm

A friend of mine recently gave me a loco that he said he wanted to see go to a good home. She's an H0 gauge Japanese brass model of about 1965-1970 vintage. Evidently she hasn't turned a wheel in years and her performance is a bit quirky. Before testing her I gave a 10,000 mile service - oiling round, commutator cleaning etc. On starting I find she draws anything between 0.6 and 1.7 amps. This goes down to 0.4 - 0.7 once she gets rolling. Also, the loco is at first very slow, even on full voltage. Starting with the load simulator pushes the amps to 2.0, which blows the breaker. The loco is very sensitive to a 1 in 68 gradient, being faster downhill than up. The wheels turn perfectly evenly - no sign of binding. All these things lead me to suspect that the magnet in the motor may have lost some (or perhaps much) of its strength. Can anyone please confirm (or contradict) this theory? I'd be grateful for any help I can get on this.

There's a picture on flickr: https://www.flickr.com/photos/53775591@ ... 783700505/

Cheers and many thanks,
Artur

Mountain Goat
Posts: 591
Joined: Fri Oct 05, 2018 12:57 pm
Contact:

Re: Weak magnet?

#2

Post by Mountain Goat » Thu Apr 18, 2019 7:38 pm

Two possibilities here. One is a weak magnet and the other is a little oil on the commutator plates. However, with oil the symptoms I have had are plenty of speed at first and then it slows as the oil dries, and then some smoke with slow running and then the controller trips.
A weak magnet tends to be weak and I have had the overload trip which indicates a high current draw or a short circuit. I believe it is a weak magnet, which usually happen on models around 40 years of age or older.
Enjoying freelance modelling in 7mm narrow gauge Feel free to ask questions relating to the Mountain Goats Waggon & Carriage Works thread.

User avatar
RSR Engineer
Posts: 81
Joined: Sun Oct 07, 2018 11:18 pm
Location: Freistaat Bayern
Contact:

Re: Weak magnet?

#3

Post by RSR Engineer » Tue Apr 23, 2019 6:24 pm

Thank you, MG, you've confirmed my suspicions. I suppose I could acquire a couple of small neodymium magnets and mount them alongside the main one. Perhaps you or another member can advise me on what strength they should be how to orient them and hold them in place?

Cheers and many thanks,
Artur

footplate1947
Posts: 566
Joined: Fri Oct 19, 2018 8:32 am
Location: Norham, Northumberland
Contact:

Re: Weak magnet?

#4

Post by footplate1947 » Tue Apr 23, 2019 9:15 pm

Have a look on ebay, a few sellers......... One reliable seller I have bought a lot of spares from is john050272
He sell a lot of Hornby spares. He has most Neo Mags ........ And his prices are reasonable....................John
If only there was enough hours in the day..................John

User avatar
RSR Engineer
Posts: 81
Joined: Sun Oct 07, 2018 11:18 pm
Location: Freistaat Bayern
Contact:

Re: Weak magnet?

#5

Post by RSR Engineer » Tue Apr 23, 2019 11:07 pm

Many thanks, John, I'll follow that up.

Cheers,
Artur

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest