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Mitsumi motors running hot


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I have noticed that the Mitsumi I fitted as a replacement for a K's HP20(?) motor gearbox runs very hot driving only a replacement brass gearbox of unknown manufacture, see photo.

So I  tried instead an open frame motor of similar dimensions to see how that performed and it's barely warm to the touch.

Then ran another Mitsumi under no load and 12 volts as before, again it ran hot.

It appears to be a characteristic of the design, question is - does it lead to a shorter life?

P.S.

Any ideas on the manufacturer of the open frame motor and also the gearbox? 

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Edited by Virgil
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13 minutes ago, Virgil said:

I have noticed that the Mitsumi I fitted as a replacement for a K's HP20(?) motor gearbox runs very hot driving only a replacement brass gearbox of unknown manufacture, see photo.

So I  tried instead an open frame motor of similar dimensions to see how that performed and it's barely warm to the touch.

Then ran another Mitsumi under no load and 12 volts as before, again it ran hot.

It appears to be a characteristic of the design, question is - does it lead to a shorter life?

P.S.

Any ideas on the manufacturer of the open frame motor and also the gearbox? 

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Hi ,

 

The motor is labelled M15N-3 which according to a post on this forum has a nominal rating of 8 Volts not 12 Volts.

 

Regards

 

Nick

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5 minutes ago, Virgil said:

Nick, is there a 12 volt rated version?  I thought this was one as I'm sure that I bought it in a batch that was advertised as 12 volt.

Hi,

 

I don't know, the links to the motor on Mitsumi's website produces a message: "404 page not found at present".

 

There are or were some Ebay offerings that say its an 8V motor (as well as others saying 12V).

 

 

Regards

 

Nick

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7 minutes ago, Virgil said:

Nick, is there a 12 volt rated version?  I thought this was one as I'm sure that I bought it in a batch that was advertised as 12 volt.

 

The advertised rating of miniature electric electric motors is is very variable - a little web browsing will find the same motor with, apparently, several different stated ratings.

 

The Mitsumi M15N-3 is perfectly happy running on 12V; if it's running hot then look to the mechanism to which it is attached.

 

If you go to https://www.electronicsdatasheets.com/manufacturers/mitsumi/parts/m15n3-series , you will find that, whilst the nominal rating is 8V, the stated voltage range is 6V - 28V.

 

Regards,

John Isherwood.

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OK John, I have tested two Mitsumis so far and they run hot under no load, I will test the rest of the batch to see how they perform. 

Thanks for the input and link to the data sheet.

Regards

Doug

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16 minutes ago, Virgil said:

OK John, I have tested two Mitsumis so far and they run hot under no load, I will test the rest of the batch to see how they perform. 

Thanks for the input and link to the data sheet.

Regards

Doug

 

How do you define ''run hot under no load''? Is that applying maximum power from your controller, to a motor that is not connected to anything, for a significant period of time?

 

If so, I would expect any motor to get warm / hot under such treatment.

 

In service, connected to a free-running chassis via a sensible reduction gearbox, the motor should not be stressed to the point where it overheats.

 

Regards,

John Isherwood.

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John, thank you for the post.

 I have since carried out running tests of several different makes of motors which has led me to the following conclusion.

Hornby black can motor - as fitted to Bulleid pacifics etc;  ran similarly hot to the Mitsumis after about 5 to 10 minutes at 12v no load.

Bachmann can motor - as fitted to split frame models;  also ran hot as above.

The unknown make skewed 5 pole motor as seen above in photos, tested as above can motors - barely warm to the touch.

Why is it different? 

My thoughts are firstly that it is open frame allowing much more cooling, seems obvious really - oh well!

So Mitsumis are probably no more prone to hot running than other can motors - even under stress.

 

P.S I shall continue using Mitsumis but not for the pictured chassis above as the open frame motor's higher rotational speed suits the low ratio gearbox fitted and so will better suit the passenger loco.

Regards

Doug

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I've had some issues with Mitsumis appearing to run hot. I had put one into a pannier tank and was concerned about how hot it was getting so I stuck it onto the rolling road and ran it all day at an exhibition - no problems at all. I now have these motors in 3 loco's and they run really well so I gave up worrying about the temperature. I have to admit I have a smallish industrial layout where the running is stop/start and I'm interested to see how others have found them when running under proper load on a continuous run. However I'm very pleased with them overall. 

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The original open frame motor looks like a DS10 (very high revving motor), while the gearbox looks like a Mike Sharman milled brass box. It has been 'tweaked' with small washers , I remember this was one of the things to do on it to improve things.

 

The DS10 may just need new brushes, common failure on them - Branchlines I think still do them.

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