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Offline Zme  
#1 Posted : 11 February 2021 17:23:43(UTC)
Zme

United States   
Joined: 02/10/2013(UTC)
Posts: 760
Location: West Texas
Hello everyone

I have a serious question concerning my Marklin 8869? (v100/212).

Why does the motor heat up after a short run?

I have several of this model and have taken them apart, cleaned all the parts in an ultrasonic cleaner, looked for damaged parts, lubed and reassembled, but I still have the same problem.

Is this a characteristic of the motor used in this locomotive, and it is common for them to run hot.

I checked this motor and made certain it was clean. I polished the surface where the brushes contact (someone out there knows the technical name for this). The brushes looked fine with plenty of material, not worn out. Is it possible, there is to much brush pressure. Could this cause it to overheat?

I even replaced parts in the truck assemblies, including new wheel contacts, gears, etc.

If someone out there has had the same problems, and came up with a solution, or have a suggestion, please chime in.

Thanks

Dwight
Offline Carim  
#2 Posted : 11 February 2021 21:42:46(UTC)
Carim

United Kingdom   
Joined: 15/09/2014(UTC)
Posts: 649
Location: London
Originally Posted by: Zme Go to Quoted Post
Is it possible, there is to much brush pressure. Could this cause it to overheat?



Yes! Try flexing them a bit. The thing they touch is the split-ring commutator.

Carim
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Zme
Offline Zme  
#3 Posted : 12 February 2021 00:15:32(UTC)
Zme

United States   
Joined: 02/10/2013(UTC)
Posts: 760
Location: West Texas
Thank you. I will check this and see if there is an improvement. Will make certain truck assembly is good also.

Take good care, I appreciate it.

Dwight
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Offline Mman  
#4 Posted : 03 July 2021 23:12:41(UTC)
Mman

United Kingdom   
Joined: 23/05/2021(UTC)
Posts: 247
Location: England, Guildford
I got interested in this post whilst looking for a Morley posting.
I have an 8875 BR216 Diesel which runs very hot such that the centre of the body is distorted.
Back in the bad old days of my Hornby Dublo if a loco ran hot it usually meant that the field magnet needed re-magnetising, but magnets have improved since the 1950’s. The HD prewar horseshoe magnets were the worst needing frequent attention, Märklin HO wisely used wound fields which don’t suffer from this problem (until they went digital).
Has anyone had to re-magnetise these tiny motors? I have a magnetisier somewhere and when I find it I’ll have a go to see if that improves matters.
ChrisG
Offline Zme  
#5 Posted : 04 July 2021 06:52:56(UTC)
Zme

United States   
Joined: 02/10/2013(UTC)
Posts: 760
Location: West Texas
Hallo. Hope all is well.

Yes I have a 8874 (216) which had the same issue. It got to the point where the shell would not snap to the frame.

I disassembled this locomotive completely and adjusted the pressure of the brushes. I never considered the magnets were an issue. When I do a cleanup like this I clean the motor and re-oil the gears and wheels.

Since my work, this engine runs smoothly and is quieter, so it was worth doing. Fortunately, I did locate a replacement shell.

If you want to consider doing this, it may be wise to get the parts diagram, but this is an older model and I did not find it on the Marklin site. Perhaps someone has this and can post it here. These type of locomotives are fairly easy to work on. You don’t have all the wheels to re-sync, you don’t have a motor which is soldered in, etc. The drawbacks might be a difficulty getting needed parts and they are small and easy to lose. Just be careful and take your time.

Best wishes.

These are great locomotives, with a heavy frame. It will pull many wagons, it is worthy.

Best wishes

Dwight

Offline Poor Skeleton  
#6 Posted : 04 July 2021 16:48:15(UTC)
Poor Skeleton

United Kingdom   
Joined: 09/10/2015(UTC)
Posts: 550
Location: England, Cambridge
Originally Posted by: Mman Go to Quoted Post
I got interested in this post whilst looking for a Morley posting.
I have an 8875 BR216 Diesel which runs very hot such that the centre of the body is distorted.
Back in the bad old days of my Hornby Dublo if a loco ran hot it usually meant that the field magnet needed re-magnetising, but magnets have improved since the 1950’s. The HD prewar horseshoe magnets were the worst needing frequent attention, Märklin HO wisely used wound fields which don’t suffer from this problem (until they went digital).
Has anyone had to re-magnetise these tiny motors? I have a magnetisier somewhere and when I find it I’ll have a go to see if that improves matters.
ChrisG


Funnily enough I have been investigating this very issue this weekend. I have a pair of 8874 loco which I have re-motored with modern 5 pole motors. Yesterday I was running them together double heading a 10 coach train and I noticed that one of them was running much hotter than the other. I traced the problem to the bogies the mechanisms of which were much stiffer than usual. I adjusted the pickup wipers a bit, but the biggest difference I saw was in loosening the securing screw by a tiny amount. I also felt that the exact alignment of the bogie frames made a difference, so I positioned these to give good clearance to the gears. The loco now runs really smoothly - actually better than its partner.

I'm also of the opinion that the old 3 pole motors run hotter than the 5 pole, though I am suspicious the motor I have has become demagnetised

Hope this is of help, all the best


Chris

Edited by user 04 July 2021 20:56:14(UTC)  | Reason: Not specified

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Online JohnjeanB  
#7 Posted : 05 July 2021 01:31:33(UTC)
JohnjeanB

France   
Joined: 04/02/2011(UTC)
Posts: 3,084
Location: Paris, France
Hi Dwight
Here are some possible cause of motor overheating / burning (When I was using N gauge)
- When adding a magnet for signalling. The magnet was too close to the motor and distorted the magnetic field and caused the motor to overheat and burn.
- Excessive force on brushes can cause the motor not to start and burn
- Excessive use of very slow starts: it endangers the motor that when stalling may cause the motor to be reduced to a resistor
- Power supply wave form. Some waveform may cause motor overheating

You should not be the only one as for N gauge it was not rare to replace a motor (almost never happen to me in HO gauge Märklin)
Cheers
Jean

Edited by user 05 July 2021 13:12:18(UTC)  | Reason: Not specified

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Zme
Offline zoooctan  
#8 Posted : 06 July 2021 05:33:58(UTC)
zoooctan

Singapore   
Joined: 07/09/2019(UTC)
Posts: 65
Location: Singapore, Singapore
Hello, thank you all for such an informing thread. I'm quite fascinated by the topic of motors getting magnetised or having been affected. I too have a few locomotives with strange behaviour. One for example, (Rio Grande 4-4-0) seems to stall often. But when pushing the motor amatures with a toothpick, they start running once at a moderate speed. if I go to a slow speed or often from a stop, the motor has trouble starting.

Can someone share more with me about what happens when a motor gets demagnetised? What are the symptoms and what are the possible rectifications?
What I can see so far, is that cleaning alone is not enough?

Thank you
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Zme
Offline Mman  
#9 Posted : 06 July 2021 08:16:50(UTC)
Mman

United Kingdom   
Joined: 23/05/2021(UTC)
Posts: 247
Location: England, Guildford
Originally Posted by: zoooctan Go to Quoted Post
Hello, thank you all for such an informing thread. I'm quite fascinated by the topic of motors getting magnetised or having been affected. I too have a few locomotives with strange behaviour. One for example, (Rio Grande 4-4-0) seems to stall often. But when pushing the motor amatures with a toothpick, they start running once at a moderate speed. if I go to a slow speed or often from a stop, the motor has trouble starting.

Can someone share more with me about what happens when a motor gets demagnetised? What are the symptoms and what are the possible rectifications?
What I can see so far, is that cleaning alone is not enough?

Thank you

It’s 50 years since I covered electric motor theory but if I remember correctly:
(Simple) motors such as these have a rotor and a stator.
The rotating part is the armature which in our case has 3 lobes for pre 2000 locos and 5 lobes for post 2000.
The stationary part consists of a pair of magnetic poles with magnetism provided by a shaped permanent magnet.
Since like poles repel each other (eg 2 norths) and unlike poles attract this is one of the principles of motor theory, electromagnetism theory has two parts: 1) pass current through a wire and it creates a magnetic field and 2) move a wire through a magnetic field and it generates a current in the wire.
Each lobe’s armature winding will have current passed through it creating a north pole say, then as the armature rotates the commutator (on which the carbon brushes press) will switch the direction of current flow to create a south pole in that lobe and so on as it turns.
These created poles react with the (permanent) field (a north and a south pole) of the permanent field magnet so each lobe of the armature will be alternately pulled and pushed to give a turning effect (torque).

Older types of permanent magnet are not really permanent; heat, mechanical shock, time and lack of a keeper * will cause the magnet to lose its strength.
The keeper in these motors is the steel armature between its poles. If the armature is removed from the field magnets they have lost their keeper and therefore some of their strength.
When the field strength is reduced, the push and pull effect with the armature and its changing poles is also reduced as is the back electromotive force in each lobe created by moving the wires in the lobes through the field from the permanent magnets is also reduced allowing more current to flow in each lobe.

So reduced power of the field magnets means: 1) reduced torque and 2) increased current in each lobe and therefore also 3) excessive heat generated.

* The remedy is to re-magnetize the field magnets using a remagnetizer which flashes a very powerful magnetic field around them, this is done with the motor fully assembled with the armature acting as the keeper in place.

With pre digital HO Märklin this was not a problem since the field magnets were also electromagnets not permanent ones - this is also why they would work with both ac and dc.

Long and wordy I know, a white board would have helped!
ChrisG

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Offline Zme  
#10 Posted : 07 July 2021 01:05:48(UTC)
Zme

United States   
Joined: 02/10/2013(UTC)
Posts: 760
Location: West Texas
Hello. I have noticed replacement motors now arrive in the anti static bags similar to electronic components.

In light of your comments I have reconsidered the procedures I use when doing a cleanup. I hope this will improve the outcome.

I noticed the tweezers I use to pickup and place cleaned parts are magnetized. Could this cause the parts to get magnetized also?

I looked up re-magnetizing motors on YouTube but didn’t really see anything. How could this be done on the small z scale motor?

Thanks for your comments.

Dwight
Online JohnjeanB  
#11 Posted : 07 July 2021 11:43:32(UTC)
JohnjeanB

France   
Joined: 04/02/2011(UTC)
Posts: 3,084
Location: Paris, France
Hi Dwight
In my opinion, the replacement motors don't need an anti-static bag (may-be only the color).
In the production of magnet, ferrite oxyde or Neodyme (strongest ones) are magnetized using very very powerful coils producing a large magnetic field during milliseconds.
This tool is way beyond what you can find in a normal household. Huge, heavy, costly.
Cheers
Jean
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Zme
Offline kiwiAlan  
#12 Posted : 07 July 2021 15:29:41(UTC)
kiwiAlan

United Kingdom   
Joined: 23/07/2014(UTC)
Posts: 8,082
Location: ENGLAND, Didcot
Originally Posted by: Zme Go to Quoted Post

I noticed the tweezers I use to pickup and place cleaned parts are magnetized. Could this cause the parts to get magnetized also?


Yes, that will cause small screws and springs to get magnetised enough to be a nuisance.

To make a demagnetiser, use the coil off an old mains transformer, and connect the leads to a marklin H0 analogue transformer (you could use the yellow and brown wires on the M transformer). Now with the power on move the tweezers or screwdriver slowly through the hole in the coil and then withdraw it slowly. Turn the power off and see if it is still magnetised.

You need to withdraw the tool slowly so the magnetic field it sees from the coil is slowly reduced. If you remove the tool too rapidly it could get far enough away from the field at the peak of the AC current leaving some residual magnetism.

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Zme
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