Overheating Mashima 1224

Model and prototype rolling stock, locos, multiple units etc.
David Knight
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Overheating Mashima 1224

Postby David Knight » Mon Jul 10, 2017 1:38 am

I wonder if I might tap the collective wisdom for a little help? Quite recently one of my engines has been overheating but for no obvious reason. The mechanism runs freely, the motor, a Mashima 1224, has been lubricated but not to excess and until recently was behaving itself. Now after only a short run the brushes and the end bearing heat up to the point they are too hot to touch. Any suggestions as to where to check next? :?

Cheers,

David

Enigma
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Re: Overheating Mashima 1224

Postby Enigma » Mon Jul 10, 2017 9:03 am

Interesting. I have just 'finished' a chassis for a 16xx pannier using a High Level double reduction gearbox and a 1224 Mashima. So far I have given it a relatively gentle running in on my test track and it all seems to be running very smoothly. However, after several minutes I found that the motor was very hot to the touch so stopped the running and let it cool down. The chassis was new and possibly a bit 'tight' but it ran OK without the motor fitted. I had lubricated all the bearings and adjusted the mesh of the worm and first gear so that it wasn't to deep. Is it a trait with these motors to run hot?

My thought is that, if they are motors originally designed for say, ejection drives in VCR machines, then they are probably not designed to be continuously used. Running a loco around a tail-chaser layout would, in the electric motor world, probably be considered a situation where a continuously rated motor should be applied. On a small shunting plank then there is little opportunity for lengthy and non-stop running periods so excessive over-heating may be avoided.

So, as the OP asks, could there be a long term problem with this version of the Mashima, do the other versions 'suffer' in the same way and, if so, should we be worried about eventual melt-down?

In the past I have had a smaller one self-destruct with a melted brush holder but at the time blamed myself for possibly creating a short circuit or similar within the chassis. Perhaps I was actually over stressing it.

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Noel
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Re: Overheating Mashima 1224

Postby Noel » Mon Jul 10, 2017 9:59 am

Having at one time been an EMGS member, I still have a copy of their manual. The page for the Mashima 1220/1224 was published in 1992, so the specification of the motor may have changed since, but it shows that the 1220 is the more powerful of the two, with the 1224 having a much slower rpm, but lower power output, due to high armature resistance. It also suggests that the 1224 can be stalled for up to a minute without damage.

The suggested gear ratio is 1:30 or 1:38 [presumably what was available at the time], against 1:50 or higher for the 1220. It recommends the use of plastics compatible oil. The subjective comment is that they are smooth running motors of modest power which should, with appropriate gearing, give satisfactory performance in a wide range of smaller locos.

Does any of that help at all?

I'm no expert on this area, but previous reading suggests that problems can also arise if the securing bolts are slightly too long, or the gearbox is not entirely square, so that tightening the bolts distorts the motor casing. I assume that you have ensured that the loco slips before stalling?
Regards
Noel

Enigma
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Re: Overheating Mashima 1224

Postby Enigma » Mon Jul 10, 2017 10:54 am

My running in techique is to have the chassis/loco running against something heavy across the rails so that it is constantly 'slipping'. Cheaper than a rolling road ;)

I've not yet had any negative instances using this method - and very rarely (if ever) had anything stall.

The 1224 was recommended (possibly by Chris Gibbons) as a suitable motor for this loco and the 'box is a relatively high reduction but not one of his very high ones.

David Knight
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Re: Overheating Mashima 1224

Postby David Knight » Mon Jul 10, 2017 12:38 pm

Thanks for the ideas so far. A little further background, the locomotive in question is the J72 I built on this forum some time ago and has a HighLevel 54:1 gearbox. I had to replace the brush holder/bearing section due to melted plastic in that area from the same problem and had high hopes that a new holder and a cleanup of all the associated bits would help. It didn't. :(

Cheers,

David

Philip Hall
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Re: Overheating Mashima 1224

Postby Philip Hall » Mon Jul 10, 2017 12:51 pm

I think the EMGS manual sheets are still current, but the 1224 was always the weakest and lower revving of the two 12 series motors, but I found it smoother in starting and running. I have one fitted in a Riceworks NBR 'R' 4-4-0T married to a set of Ultrascale 50:1 gears (the recommendation was for 38:1 but I went a bit higher for a better starting performance). It's last extended run was around the DRAG test track at the AGM held in Devon a few years ago, and it trundled around for an hour with ten wagons in tow quite happily. I didn't notice any excess heat.

I would think you might have a rogue, or maybe from a small rogue batch.

We don't normally have problems with hot motors, in contrast with the old days. I remember the late Ken Northwood setting a 50 wagon train with a 42xx or a 72xx in motion when I once visited the North Devonshire Railway; the current draw of a big Pittman was substantial and after a couple of long circuits you couldn't touch the top of the boiler! It was whitemetal, too...

Philip

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Tim V
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Re: Overheating Mashima 1224

Postby Tim V » Mon Jul 10, 2017 3:25 pm

Something in the back of my mind says the 12:24 was prone to overheating, I have a couple of them in the scrap bin.

Once the 10 series motors were introduced, I started using them as standard; a substantially better motor.
Tim V
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martin goodall
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Re: Overheating Mashima 1224

Postby martin goodall » Mon Jul 10, 2017 7:01 pm

I cannot claim any personal experience of using these motors, although I have several squirreled away as part of my contribution to the European Kit Mountain.

I have been in the habit for a number of years of filing useful tit-bits from this and other forums, and I see that there has also been discussion in the past about 1024s over-heating. Some report the problem; others have never experienced it.

The problem would not therefore appear to be confined to the 12 series but may also affect the 10 series motors. However, it seems that quite a lot of people have never encountered a problem at all.

It sounds as though it is something that requires empirical scientific/technical investigation by someone who has both the requisite professional background and the right scientific instrumentation to get to the bottom of this issue.

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Will L
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Re: Overheating Mashima 1224

Postby Will L » Mon Jul 10, 2017 10:52 pm

martin goodall wrote:I cannot claim any personal experience of using these motors, although I have several squirreled away as part of my contribution to the European Kit Mountain.

I have been in the habit for a number of years of filing useful tit-bits from this and other forums, and I see that there has also been discussion in the past about 1024s over-heating. Some report the problem; others have never experienced it.

The problem would not therefore appear to be confined to the 12 series but may also affect the 10 series motors. However, it seems that quite a lot of people have never encountered a problem at all.

It sounds as though it is something that requires empirical scientific/technical investigation by someone who has both the requisite professional background and the right scientific instrumentation to get to the bottom of this issue.


A motor running hot when in a verifiably free running chassis would de cause for concern, but, as lot of modellers fail to realise that the the biggest load on the motor is often the internal stiffness of the chassis and any motor asked to work at the limits of is abilities is going to get hot. Therefore occasional reports that some people have managed to get get a particular motors to overheat isn't necessarily a reliable commentary on the motor in question. More likely to do with the general difficulty in getting a coupled chassis to run freely.

The 1024 is my favourite motor, I have made one run hot but only when I abused it

David Knight
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Re: Overheating Mashima 1224

Postby David Knight » Tue Jul 11, 2017 1:26 am

Will L wrote:A motor running hot when in a verifiably free running chassis would de cause for concern, but, as lot of modellers fail to realise that the the biggest load on the motor is often the internal stiffness of the chassis and any motor asked to work at the limits of is abilities is going to get hot. Therefore occasional reports that some people have managed to get get a particular motors to overheat isn't necessarily a reliable commentary on the motor in question. More likely to do with the general difficulty in getting a coupled chassis to run freely.

The 1024 is my favourite motor, I have made one run hot but only when I abused it


The engine in question is the one built in this thread viewtopic.php?f=19&t=1037 So CSBed from the start and it will roll when pushed (with the motor removed) with no binding. I have to wonder if the fact that both the front bearing and brush housings both heat up is a factor. I checked to see if there was any great resistance with an Ohm meter and it was negligible. I have older 1224s that have not (as yet-touch wood) been a problem. That said, this motor is now pushing 7 years old, is in a favourite engine and may just be past its prime.

Cheers,

David

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Jol Wilkinson
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Re: Overheating Mashima 1224

Postby Jol Wilkinson » Tue Jul 11, 2017 6:51 am

One cause of over heating could be loss/reduction of the residual magnetism in the motor, something collectors of Hornby Dublo and other old electric toys are familiar with. This requires an increase in voltage and current to achieve the usual level of power output. So more wattage means more heat.

The later 14xx and 10xx Mashimas were apparently fitted with more powerful rare earth magnets. Could it be that the magnets in the 12xx are more prone to loss of magnetic force and hence suffer from overheating.

Edward45
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Re: Overheating Mashima 1224

Postby Edward45 » Tue Jul 11, 2017 8:17 am

If possible I would be incline to take the motor apart and give it a thorough clean. The symptoms do look as if a short is occurring, worse case would be the windings, but a dirty/damaged commutator or brushes can also cause similar problems. In view of the age of the motor have you ever changed the brushes?

David Knight
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Re: Overheating Mashima 1224

Postby David Knight » Tue Jul 11, 2017 1:09 pm

Cleaned and lubricatedjust this weekend. The brushes appear to be in good nick with no sparking and decent size. I considered the possibility of a short and certainly the symptoms point in that way but the motor starts well and problems only show up after the thing has been running for 15-20 minutes.

Cheers,

David

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jsherratt
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Re: Overheating Mashima 1224

Postby jsherratt » Wed Jul 12, 2017 8:36 am

I've had problems with Mashima motors overheating, though in my case they were both 14mm motors rather than the 12mm. As a result of this, I always run them in carefully before they are firmly installed in a locomotive. 5 minutes one way light, rest, 5 minutes light the other way, rest and so on.... And then the same with the gearbox attached before it goes in the chassis.

I seem to remember reading somewhere (?) Mashima motors can run "warm" but how warm is warm??

I've had to replace two motors, in each case they were exchanged without difficulty. One of the motors ran so hot (while lightly test running a 4F light engine) the plastic melted such that the brushes were not in contact with the commutator.

John

Edward45
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Re: Overheating Mashima 1224

Postby Edward45 » Thu Jul 13, 2017 12:29 pm

This is a shot in the dark. Remove the brushes and check that the shaft spins freely.

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Jol Wilkinson
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Re: Overheating Mashima 1224

Postby Jol Wilkinson » Thu Jul 13, 2017 2:02 pm

David,

if the motor shaft spins freely and the loco hasn't got excessive friction in the drive, then it may be a problem within the motor.

The EMGS Manual quotes 96mA for a 1224 at 12v with a power output of .4W. Max (safe?) currrent is quoted as 250mA.

I suggest you use a meter to check max current draw. If in excessive of those figures, then there could be a short in the windings which might be causing the armature or brushes to overheat, or the magnets have lost power. That requires extra current to create the same power output and hence creates more heat.



Jol

David Knight
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Re: Overheating Mashima 1224

Postby David Knight » Thu Jul 13, 2017 2:41 pm

Jol,

I've been leaning in that direction as on a number of occasions the bulb that I use as short circuit protection has glowed merrily with no obvious source other than the motor and the SCR on my controller has also become warm.

I think the time has come to bid farewell to this motor, salvage the usable bits and bin the rest.

Thanks to all who contributed.

Cheers,

David


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