# Replacing old Mehano motor



## pygmalion (Apr 29, 2018)

Recently I have discovered a bunch of old Mehano(tehnika) model trains from my youth and I decided to bring them back to life, by repairing coupler holders (http://www.pinteric.com/modeltrain.html), making new railings, replacing motors and digitalization. Of course these locomotives aren't worth much, so I tend to use inexpensive elements, like laisdcc decoders.

Currently I am picking up a replacement double shaft motor. Being physicist, I like to do things analytically. I have measured existing Mehano motor 12V unloaded frequency (200 Hz = 12000 RPM) and gearbox ratio (8.5 to 1). I haven't (yet) measured motor power though, because this is rather a complicated procedure. Since Mehano model trains have low torque the idea is to reduce motor frequency and/or increase motor power (power = 2 * pi * frequency * torque).

There is a plenty of inexpensive motors on EBay; frequency is always specified, but there is no specification on motor power. *I have realized that those modern motors are much smaller than the fourty years old ones (three to four times smaller in terms of volume), but I assume that due to stronger magnets and more precise design their power might be even higher. Is this assumption correct?
*

Second, despite most motors have frequencies above 10000 RPM, I found a few with frequencies between 5000 and 10000 RPM. *Which frequency would be most appropriate if the gearbox ratio is only 8.5?*

Thank you for sharing your experiences and giving some advises.


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## gregc (Apr 25, 2015)

pygmalion said:


> Mehano motor 12V unloaded frequency (200 Hz = 12000 RMS).


RMS is what? (root mean square)


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## pygmalion (Apr 29, 2018)

gregc said:


> RMS is what? (root mean square)


Thanks for pointing to this _lapsus calami_.


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## ebtnut (Mar 9, 2017)

I think we have a mis-match in terminology here. In general, model motors are rated in RPM (rotations per minute) per 12 volts DC. There shouldn't be any RMS component since it is DC, not AC we're using here (unless we're talking Marklin). Gear boxes are normally measured in a ratio, such as 37 to 1 (typical for steam models) or maybe 13 to 1 (sometimes used with diesels). In most applicatons you would like to have motors with lower RPM's and higher gear ratios to better achieve scale speeds.


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## wvgca (Jan 21, 2013)

noticed that you edited your post .. RPM instead of RMS, any ways

usually you are better off replacing with a motor that is the largest that can be fitted within an enclosure, and a motor that at unloaded speed is not more than maximum speed that is desired for the final resulting system


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## J.C. (Dec 24, 2016)

replacing a motor isn't rocket science as wvgca says , start with something like this https://www.ebay.com/itm/Sagami-283...020731&hash=item5209520913:g:E0AAAOSwozxa6MRR


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## pygmalion (Apr 29, 2018)

Thank you for your suggestions. Still, I want to quantify improvement done by motor replacement. I try to study model train characteristics as analytically as possible.

One can observe my work by reading my blog Model train nostalgia.


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## DonR (Oct 18, 2012)

Many of us are not technically astute but appreciate
the results of all this brain power.

But, when it comes to model locos the important factor
in addition to efficient motor and gearing is weight.

The weight of the loco presses the wheels against
the rails and the resultant traction is pulling power.
Many of us add more lead when we can fit it in.

A heavy HO diesel loco can easily pull 20 or so cars,
even more if the cars are equipped with metal wheels.

Another factor you should want to check is amp
draw. You can do a stall test. Most of the new
motors would likely stall out at less than an amp.

Most run their locos as a scale 35 or 40 mph or
less...the slower the speed, the lower the amp draw.
As a result, we can run 4, 5 and 6 locos at the
same time with even the most primal DCC controllers.

dON


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## pygmalion (Apr 29, 2018)

If anyone is interested, I did some theoretical and experimental analysis of motor characteristics that can be seen here: Model train nostalgia - original versus modern motors

Based on your suggestions, I decided to transfer to Mitsumi motors. They are a bit slow and can achieve the equivalent top velocity of 53 mph, but are also much more efficient.


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## Jscullans (Jul 8, 2019)

I have a 4-6-2 I replaced the motor in so I could install a decoder. I’m not one that looks at stuff in the same attention to detail and scientifically but I do appreciate a smooth running model. I saw a thread a couple months ago where they were talking about a Chinese branded six pole motor that is absolutely fabulous supposedly. My preference is the cannon iron core motors. They have a substantial amount of torque and I get ones that are good for up to 24 volts so I know I’m not running the risk of burning one up as easily. I normally use the dn22 which is easily available on eBay


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## pygmalion (Apr 29, 2018)

Jscullans said:


> I have a 4-6-2 I replaced the motor in so I could install a decoder. I’m not one that looks at stuff in the same attention to detail and scientifically but I do appreciate a smooth running model. I saw a thread a couple months ago where they were talking about a Chinese branded six pole motor that is absolutely fabulous supposedly. My preference is the cannon iron core motors. They have a substantial amount of torque and I get ones that are good for up to 24 volts so I know I’m not running the risk of burning one up as easily. I normally use the dn22 which is easily available on eBay


Thank you for sharing your experience. Canon DN22 has no-load speed of 6600 RPM @ 24V, which means it is even slower than Mitsumi M24N-1 that has 5900 RPM @ 18V. Despite the dimensions are the same, I cannot use Canon DN22 as I need double shaft motor. It seems that both motors are three pole.

Since you are using it on 4-6-2, you do not need high speeds, so it seems to be a good choice. For my diesel locomotives theoretical top speed of 53 mph with M24N-1 is a bit small, but since no model railway has long sections of straight rails to realistically develop higher velocities, maybe this is OK.


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## pygmalion (Apr 29, 2018)

I have finalized the motor replacement. Since nothing is perfect, the effective speed goes from impressive 1kmh/1mph up to less than impressive 65kmh/40mph.

I must now decide whether to proceed with motor replacement for all remaining locomotives. What is your opinion? Is that speed span acceptable? Seeing video of the updated locomotive might be helpful:


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## MichaelE (Mar 7, 2018)

IMO, 65 kmh is plenty fast for that type of locomotive especially on a smaller layout.

Even my high speed passenger trains are seldom ran at speeds faster than 80 kph on my size layout.


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## pygmalion (Apr 29, 2018)

All I have is bunch of Burlington Northern diesel locomotives ALCO Century 415, ALCO Century 430, ALCO Century 628, ALCO RS-2, ALCO RS-11, ALCO S-2, EMD F-7, EMD GP-18, EMD SD-40, EMD SW1 (Model train nostalgia - Burlington Northern locomotives). Many are switchers, but a few are "real" locomotives. So 65kmh/40mph is fine for all of them?


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## Jscullans (Jul 8, 2019)

On a small layout especially with freight trains that is about all the faster you would see any prototype going unless you’re on a main line then you may see up to 70 mph but most layouts are small to the point where that train would lap the layout in a matter of a couple of seconds and it would never look correct.


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## MichaelE (Mar 7, 2018)

Like Jscullins said, the speed should fit the layout size.


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## Jscullans (Jul 8, 2019)

I have a 10x16 layout with double track main line around the whole thing and I don’t run any train much faster than about 60 scale mph otherwise that’s too fast and that’s even running my rendition of the super chief which would have run somewhere around 100 in real life. Also with speed comes noise from the wheels which in my layout room can get awful deafening. When you have a 60 plus car train on it the noise just gets louder too. Usually I only have about 15-20 car freight and about 10-15 car passenger trains max


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## MichaelE (Mar 7, 2018)

My passenger trains seldom run over 50 mph and normally around 35 or 40 mph. Same for my single freight train. The Rhätische Bahn consist never sees more than 25 MPH. At times even that seems fast. Mine is 11x16, but with a lot of curves.


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## pygmalion (Apr 29, 2018)

May I ask what are those layout dimensions? Feet? Meters?


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## MichaelE (Mar 7, 2018)

That is in feet and the second figure should be 13' not 16'. There is also a seven foot five track yard and engine service facility that borders the front wall. The layout is practically a wrap-around except for the entry doorway to the room.

The longest straight section is 9' but it is not really supposed to be seen as it's on the back side of the layout and is partially hidden by higher track in front of it. The second and third longest straight sections are 7' and 5', but are also partially hidden by terrain before exiting tunnel portals.

There are more curves exposed and fast trains do not look correct at more than about 45 scale MPH.


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## J.Albert1949 (Feb 3, 2018)

pygmalion wrote:
_"Many are switchers, but a few are "real" locomotives. So 65kmh/40mph is fine for all of them?"_

Old switchers like the S2 and SW1 had top speeds in the range of 30mph or so.
40mph tops. They had small wheels and low gearing, speeds faster than that would damage the motors and running gear. There were speed restrictions when these type of units were included in a "road consist".

All the others (GPs RS's, Century's) would have maximum speeds of 65-70mph.


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## Chops (Dec 6, 2018)

Your depth of analysis far exceeds my grasp. I shall say that the crawl on your revamped locomotive is astonishing, but I did not get to see it function at intermediate speeds, if it could run a touch slower, I'd personally like that. Speaking of personal preferences, WOT? NO CABOOSE?


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## Jscullans (Jul 8, 2019)

My layout is 10x16 feet. As far as turns go the smallest radius curve I have is about 60 inches other than on a turnout.


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## Eilif (Nov 6, 2017)

pygmalion said:


> I have finalized the motor replacement. Since nothing is perfect, the effective speed goes from impressive 1kmh/1mph up to less than impressive 65kmh/40mph.
> 
> I must now decide whether to proceed with motor replacement for all remaining locomotives. What is your opinion? Is that speed span acceptable? Seeing video of the updated locomotive might be helpful:


Thanks for sharing this. I have a couple mitsumi's and a couple old locos I'm considering dropping them in and your results are very encouraging.
Much Appreciated.


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## pygmalion (Apr 29, 2018)

Chops said:


> Your depth of analysis far exceeds my grasp. I shall say that the crawl on your revamped locomotive is astonishing, but I did not get to see it function at intermediate speeds, if it could run a touch slower, I'd personally like that. Speaking of personal preferences, WOT? NO CABOOSE?


Of course it can go slower, I was just showing top and bottom speeds.

I guess this is fine for switchers, but for road switchers it would be better if both top and bottom speeds are 50% larger. At least from the real locomotive perspective. But it is impossible to get a motor of this size with double shaft that has RPM between 4000 and 10000 (ideal is 6000).


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## pygmalion (Apr 29, 2018)

Eilif said:


> Thanks for sharing this. I have a couple mitsumi's and a couple old locos I'm considering dropping them in and your results are very encouraging.
> Much Appreciated.


I am glad my effort was of help to someone.


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## pygmalion (Apr 29, 2018)

Chops said:


> Your depth of analysis far exceeds my grasp. I shall say that the crawl on your revamped locomotive is astonishing, but I did not get to see it function at intermediate speeds, if it could run a touch slower, I'd personally like that. Speaking of personal preferences, WOT? NO CABOOSE?


I'd gladly add caboose, but I have none for Burlington Northern. I know they are regularly sold in US for couple of dollars at EBay, but shipping to Europe is then $30+. If I could fetch several pieces and send them all in one packet, I'd gladly do that.


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## Jscullans (Jul 8, 2019)

I’ve looked at some models on eBay that were in the uk and France and Germany and wouldnt bid on them due to the price of shipping being astronomical


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## pygmalion (Apr 29, 2018)

Jscullans said:


> I’ve looked at some models on eBay that were in the uk and France and Germany and wouldnt bid on them due to the price of shipping being astronomical


Yes. Unfortunately the choice of cheap pre-1990 models is incomparably larger in US market than EU market. There are plenty ob BN cabooses available at US EBay and perhaps only one over-expensive model at EU EBay.


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## Jscullans (Jul 8, 2019)

That’s kind of surprising to me. Here in the states there is a relatively decent availability of the European models so I’m somewhat surprised that it’s not the same in Europe


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## pygmalion (Apr 29, 2018)

Jscullans said:


> That’s kind of surprising to me. Here in the states there is a relatively decent availability of the European models so I’m somewhat surprised that it’s not the same in Europe


Well, as far as pre-1990 Mehano models are concerned, there is a very simple explanation. Mehanotehnika locos were produced in my country (then Yugoslavia) during the communism. The whole production was exported, mostly to USA, to get "hard" currency. There was indeed a black market - for example my father knew one person working in the factory, and they were able to get some models, for a hefty price of course.

Furthermore, as BN is an *American* operator, it would not be very surprising that even other European producers sell most of BN locomotives in USA.

Lots of people in my country, me included, are still strongly attached to these American models for sentimental reasons. Others have moved on and are using exclusively European ones.

For whatever reason, the choice for cheap BN models in USA is much much larger. If I could buy *at least three cheap* BN cabooses with just one shipping, I'd certainly do so.


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