Model Railway Forum

Go Back   Model Railway Forum > Model Railway Construction > Wiring & Electronics


Reply
 
Thread Tools Display Modes
Old 23-05-2018, 10:04 PM   #1
Meir
Junior Member
 

Join Date: May 2018
Posts: 2
Meir is on a distinguished road
Default Bachmann GWR Class 57XX motor short

Hi guys

I'm new to the forums so hi .

I wonder if anyone can help with an issue I've got with a Bachmann GWR Class 57XX which I purchased off of ebay as a "good runner"?
A good runner it ain't lol.

It's a DC (non-DCC) unit which, the time I tried it, ran slowly down the track then starting smoking slightly. My benchtop PSU reported a sharp drop in voltage from 12v to 5-6v at over an amp.

Seems to me like a short.

I've stripped the loco down to the motor and get the same result when I apply power across the two terminals.

If I measure the resistance across the terminals then it comes out as a horribly low 4 to 5 ohms.

Anyone got any good advice on the next step? Beyond chucking it in the bin that is. I love the look of this loco and would hate to have to throw it away .
Meir is offline   Reply With Quote
Old 24-05-2018, 04:33 PM   #2
Mountain Goat
Unique Member.
 
Mountain Goat's Avatar
 

Join Date: Mar 2011
Location: UK.
Posts: 2,310
Mountain Goat is an unknown quantity at this point
Default

Seems to me that the motor may have found some oil onto the commutator. It could have run perfectly just after the motor had been oiled, but then as the oil starts to dry you get a slow running smokey motor (With an burning oily smell) and the loco may run for a short while with a lack of power, and then trip the controllers overload cut out.
I've had it in the past quite a few times due to my own error of over oiling the things!

I'm no expert and I can't tell you what the current or voltage will be when the locos do this. It maybe a different reason all together. It is just that it seems to me to follow the pattern of an over oiled motor.

The solution is to clean the motor commutator and the little brushes etc, and see if it makes a difference. Use cleaning alcohol if you can get it. I've used electrical switch cleaning spray, (Not oil based), but be aware that some sprays can discolour paint, so remove the body entirely if trying such a spray. Alcohol sold for cleaning purposes is a much safer option.

Last edited by Mountain Goat; 24-05-2018 at 04:41 PM.
Mountain Goat is offline   Reply With Quote
Old 26-05-2018, 09:43 PM   #3
Meir
Junior Member
 

Join Date: May 2018
Posts: 2
Meir is on a distinguished road
Default

Thanks for the reply Mountain Goat.

Could be what you're saying, but it's definitely drawing a huge amount of current. If I set my benchtop PSU to 1amp then it'll go to that and try and take more. If I set it to 2amps then it does the same. It's definitely acting as if there is a short.

the trouble is is that I'm new to model railways and many of the engine cleaning and maintenance techniques are unknown to me. I.e. I couldn't currently tell you what a commutator is, for instance.
I'll go off and do some youtubing etc to see if I can find out .

Thanks again for the advice!
Meir is offline   Reply With Quote
Old 26-05-2018, 10:06 PM   #4
Mountain Goat
Unique Member.
 
Mountain Goat's Avatar
 

Join Date: Mar 2011
Location: UK.
Posts: 2,310
Mountain Goat is an unknown quantity at this point
Default

Would the motor windings handle 2 amps if it shorted? Most DC 00 gauge controllers supply up to 1.5 amps. Go easy just in case.
Model railway controllers have a form of overload protection as a train jumping the track and shorting the two rails most of us have experienced. It is for events like these that our controllers need the overload protection.
Even my simple controller uses a bulb to protect from damage should I have a short.

I can help you with the terms of the motor. The central bit of the motor that turns (The whole structure that fits onto the shaft that turns) is known as the armature. Part of this armature has a segmented plate that the two brushes touch. This plate is known as the commutator. The commutators job is to supply current to each of the motors coils at just the right moment that it causes the motor to rotate as a coil acts as an electric magnet, and is attracted or repelled by the fixed magnets around the edge of the motor to cause the armature (Which has the coils attached to it) to rotate. [There are other types of motor which are slightly different but the basic principle is similar].
I hope this information helps. You may already know more then I do. I only know just enough to get by in regards to this hobby!
Photo shows my overload protection bulb (12V 15watt (I think its 15)) wired in series. The idea is that if there is a short the bulb takes the power instead and lights up which gives me a visual indication of a short. Modern controllers have much faster overload protection devices then my bulb. I just wanted to make a controller to run from a 12 volt battery.
Attached Images
File Type: jpg IMG_20180304_185417.jpg (325.4 KB, 6 views)

Last edited by Mountain Goat; 26-05-2018 at 10:12 PM.
Mountain Goat is offline   Reply With Quote
Old 27-05-2018, 12:41 PM   #5
RAFHAAA96
Trying-hard-to-re Member
 
RAFHAAA96's Avatar
 

Join Date: Dec 2009
Location: Moni, Limassol, Cyprus
Posts: 337
RAFHAAA96 is on a distinguished road
Default

I'll go off and do some youtubing etc to see if I can find out .

Be as cautious with the gospel according to u-tube as you are with the Wiki version, both having been posted by people who in their opinion are correct but in true may be talking, writing, spouting a load of old cobblers.
Any ‘ toob ‘ video that is extremely ill prepared without a hint of a script gets nil-points on my scoreboard, especially those where I am expected to watch the juddering out of focus back of someones hand rather than the subject under review they are stutteringly chin-wagging about. If you are going to post a public video then at least try to make it half competent.
Rob
__________________
Halton Brat, running Hornby 00 via Elite, Select Walkabout and eLink DCC using Railmaster Pro and occasionally Rocrail, β-tester. http://myweb.cytanet.com.cy/honnor/

Last edited by RAFHAAA96; 27-05-2018 at 12:44 PM.
RAFHAAA96 is offline   Reply With Quote
Reply

Bookmarks



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



All times are GMT +1. The time now is 04:04 AM.


Powered by vBulletin® Version 3.8.3
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.