Virgil Posted February 9, 2020 Share Posted February 9, 2020 (edited) 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? Edited February 9, 2020 by Virgil Add photo Link to comment Share on other sites More sharing options...
NIK Posted February 9, 2020 Share Posted February 9, 2020 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? 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 Link to comment Share on other sites More sharing options...
Virgil Posted February 9, 2020 Author Share Posted February 9, 2020 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. Link to comment Share on other sites More sharing options...
NIK Posted February 9, 2020 Share Posted February 9, 2020 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 Link to comment Share on other sites More sharing options...
Virgil Posted February 9, 2020 Author Share Posted February 9, 2020 Thanks Nick, I'm also researching further. Link to comment Share on other sites More sharing options...
RMweb Premium cctransuk Posted February 9, 2020 RMweb Premium Share Posted February 9, 2020 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. Link to comment Share on other sites More sharing options...
Virgil Posted February 9, 2020 Author Share Posted February 9, 2020 (edited) 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 Edited February 9, 2020 by Virgil Link to comment Share on other sites More sharing options...
RMweb Premium Michael Edge Posted February 9, 2020 RMweb Premium Share Posted February 9, 2020 I've not had any Mitsumi motors run hot and I've used quite a few now from various batches/suppliers. Link to comment Share on other sites More sharing options...
RMweb Premium cctransuk Posted February 9, 2020 RMweb Premium Share Posted February 9, 2020 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. 1 Link to comment Share on other sites More sharing options...
Virgil Posted February 9, 2020 Author Share Posted February 9, 2020 (edited) 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 Edited February 9, 2020 by Virgil Link to comment Share on other sites More sharing options...
Barclay Posted February 9, 2020 Share Posted February 9, 2020 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. 1 Link to comment Share on other sites More sharing options...
RMweb Premium spamcan61 Posted February 9, 2020 RMweb Premium Share Posted February 9, 2020 (edited) What kind of controller are you testing them with; if it's an old school low frequency PWM type that might explain your findings. Edited February 9, 2020 by spamcan61 1 Link to comment Share on other sites More sharing options...
Virgil Posted February 9, 2020 Author Share Posted February 9, 2020 It's a Hammant & Morgan Duette running on full wave and high impedance. Link to comment Share on other sites More sharing options...
Tim V Posted February 9, 2020 Share Posted February 9, 2020 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. 1 Link to comment Share on other sites More sharing options...
Virgil Posted February 9, 2020 Author Share Posted February 9, 2020 (edited) Tim, it's not a DS10, different brushgear and skewed 5 poles, also newish and unused. Thanks for the heads up on the gearbox, it's a nicely made piece of kit. Edited February 9, 2020 by Virgil Add photo Link to comment Share on other sites More sharing options...
Tim V Posted February 9, 2020 Share Posted February 9, 2020 I should have checked the one in my scrap box first! Link to comment Share on other sites More sharing options...
Virgil Posted February 9, 2020 Author Share Posted February 9, 2020 My DS10's in the scrap box too, minus a brush holder, spring and brush! Link to comment Share on other sites More sharing options...
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