Well, this is a first! (Loco Meltdown)

[tehachapifan]

The offending motor has to be hotter than 140F.  Typical residential hot water maxes out at 140F for scalding prevention.  I've never read about a shell melting under faucet hot water.

That seems like a more appropriate melting temp. 110ish would be spooky low, especially since I have other locos that seem to operate near in the vicinity of that.

Interesting situation Russ,
I’m sorry it mucked up one of your beautiful engines. Although I don’t have experience in that exact mechanism/ decoder/ keep alive combination my LifeLikes are very similar and the same principles apply.
I would be inclined to think there was some kind of problem with that specific motor. All of the suggestions about heat sinks and ventilation are fine but are addressing the symptom and not the root cause. I run switchers with open pole motors in much the same conditions for hours without problems. I’m sure you have too.
Does the armature spin freely if turned by hand? Is there something impeding the rotating assembly from turning easily like a dry or misaligned bushing or fuzz in the worm or truck gears? This in my mind would be the first cause of excessive amperage draw causing the motor to overload and run hot.
Just some thoughts.

Jim

Thanks, Jim! Yeah, this one hurts!

These mechanisms seem to be very high friction by nature and the friction seems to come primarily from the truck design. These are pre the axle points and cups era and have an inner metal on metal friction bearing much like a Kato N scale GP50 and others. If you were to spin the top truck gear by hand, you would feel a great deal of resistance compared to, say, a LL SW9/1200 truck. Because this friction bearing is also where the electrical contact is made from the wheel to the truck, you have to be extremely sparing with any lubrication or elec. pickup quality plummets. I used to use graphite here but eventually found that I could use an EXTREMELY tiny amount of LaBelle Lite Oil here and retain good contact. It isn't just the bearing that seems to cause all the friction though. There's also something with the way the gears interact with each other where there seems to be a lot of torque or something.  Also, I had forgotten about a pvt. message conversation I had with Daniel Leavitt way back when I built my first SW1500 after he built his, where I was expressing concern over the heat the motor was generating. So, this isn't an isolated occurrence with just this unit.

I took a bunch of readings last night with the thermometer as I ran the offending loco between steps 3 and 5, with a shield made from a thin sheet of brass on one side and no shield on the other. I also took readings before I drilled out the exhaust stacks and after. The short of it is drilling out the stacks helped and the shield helped....at least a little. Drilling out the stacks slowed the heating process by a couple minutes, which was way more than I expected. The shield also slowed the heating process significantly. Here were my readings (in degrees in Fahrenheit):

                 Unshielded Side         Shielded Side
                     
                       102.0                         97.7
                       105.4                       103.1
                       109.2                       103.8
                  range exceeded              105.2
                       108.6                       106.3
                  range exceeded              107.0
                         "  "                         108.3
                         "  "                         107.6
                         "  "                         108.6
                  range exceeded       range exceeded

                    (Loco stopped/cool-down)

                   range exceeded             109.0
                        "  "                          108.8
                        "  "                          107.4
                      108.5                        107.4
                      107.2                        107.4
                      107.2                        105.9
                      104.5                        104.3
                      101.8                        101.6
                      100.4                        100.3
                      99.1                           98.9
                      98.0                           98.2

It was also very clear during this test is that the motor did heat up much faster when in speed step 3 or 4 than when in 5, but it wouldn't cool back down once in speed step 5. It is also pretty clear that the shielding helps, but it did eventually reach the "range exceeded" mark. What temps were reached after that is unknown. If the heating only slows with the shielding but eventually reaches the point that shell damage will occur, it may not really help that much (save for possibly dispersing a pinpoint area of high heat over a wider area).

[nscaler711]

Maybe worth it to buy an Infrared laser Thermometer.
They have a range much higher than the medical ones and you can use them for other things as well.
https://www.harborfreight.com/121-infrared-laser-thermometer-63985.html

I would have posted a Flir like thermal camera, and then I hawked at the prices. But that would also pinpoint the problem area too.

On your original shell, I see you have a wire mesh over the radiator, I wonder if drilling holes there would help too.

[Mike C]

  Here is a site that lists the various melting points for plastic . I used to work for a plastics Mfg when I was a bit younger and this site seems to go along with what I know . The thing is that it will deform before becoming liguid , Probably a lot less . Maybe around 140-150 degrees . I know that the plastic out of the mixer was not too hot to touch , but after being extruded it had to pass through a 25-30 foot water bath before it could be pelletized  .  Mike

https://plasticranger.com/melting-point-of-plastics/

[mmagliaro]

About reading the current...
What is the power INPUT to your DCC booster?  Isn't it just some big transformer, or a power "brick" of some kind?  Or does it plug straight into the wall.  If it's a power brick, you can put the ammeter in line THERE.  Now you are just measuring straight DC ( or possibly 60 Hz AC, , but multimeters can handle that well).   Get a baseline current with nothing running, and then run your engine and subtract off the baseline to get the motor's current.

[tehachapifan]

Maybe worth it to buy an Infrared laser Thermometer.
They have a range much higher than the medical ones and you can use them for other things as well.
https://www.harborfreight.com/121-infrared-laser-thermometer-63985.html

I would have posted a Flir like thermal camera, and then I hawked at the prices. But that would also pinpoint the problem area too.

On your original shell, I see you have a wire mesh over the radiator, I wonder if drilling holes there would help too.

I may need to get one of those infrared thermometers. Thanks for the link!

As far as drilling out the front radiator fan area, I suppose that could help slightly but there's a lot of frame (and the decoder) filling the space between there and the motor. The motor wouldn't be able to vent thru there really at all. Plus, holes there would introduce light leaks from the headlight LED's, unless I completely reworked how they are installed.

Interesting side note, I did make two of these units that have a scratchbuilt fan and open louvers that are (barely) visible below the mesh...



I did ponder ways to make the fan actually rotate off the front worm shaft for strictly visual reasons, but never seriously pursued it for a number of reasons (mostly because the worm shaft didn't line up well) or considered it for actual cooling purposes.

  Here is a site that lists the various melting points for plastic . I used to work for a plastics Mfg when I was a bit younger and this site seems to go along with what I know . The thing is that it will deform before becoming liguid , Probably a lot less . Maybe around 140-150 degrees . I know that the plastic out of the mixer was not too hot to touch , but after being extruded it had to pass through a 25-30 foot water bath before it could be pelletized  .  Mike

https://plasticranger.com/melting-point-of-plastics/

Good info, thanks!

About reading the current...
What is the power INPUT to your DCC booster?  Isn't it just some big transformer, or a power "brick" of some kind?  Or does it plug straight into the wall.  If it's a power brick, you can put the ammeter in line THERE.  Now you are just measuring straight DC ( or possibly 60 Hz AC, , but multimeters can handle that well).   Get a baseline current with nothing running, and then run your engine and subtract off the baseline to get the motor's current.

I mat give this a try, thanks!

[tehachapifan]

Regarding decoder settings, could anything like BEMF settings potentially increase the temp of the motor? These models require a pretty high BEMF setting to run well at low speeds.

[peteski]

Regarding decoder settings, could anything like BEMF settings potentially increase the temp of the motor? These models require a pretty high BEMF setting to run well at low speeds.

Not from my perspective.  BEMF is just keeping the motor running at a constant selected speed regardless of the load (whether it is the mechanical binding, long train, or traveling up a grade).  If you disable it, you will have to manually compensate for all those variables, so you will just crank the throttle up to a higher setting.  The amount of power required (and also dissipated as heat by the motor) to keep the model running will be equal, whether the BEMF or you manually keeping the motor rpms at the desired level.

[tehachapifan]

May I suggest a really cool product?
https://www.digikey.com/en/products/detail/sunon-fans/UF385-100/1739059

Ok, even if you could find one, it would still take up too much space and still wouldn't work well in a Switcher or even a hood unit.

I’m actually a bit intrigued by these. Too bad they’re discontinued with no clear replacement in these tiny sizes. I could see maybe putting one in the cab just to get some air moving. There is a slight gap between the motor and the cab on my SW1500’s, where this could maybe be of some benefit.

I’m curious if their small size was the cause of their demise. I wonder if they produced more heat than they could dissipate.

[peteski]

How about replacing the motor with the largest coreless motor that would fit in the space?  Coreless motor is more efficient and have lots of torque. It would likely run cooler.

The other benefits would be that the winding basket is totally enclosed in a metal case (unlike the exposed rotor of the existing motor which spins very close to the plastic shell), and since the coreless motors have round shape, there will be more air space on the top and bottom of the motor.

[tehachapifan]

I built a SW1500 with one of those Bachman core-less motors, actually (sound unit). I ended up building my own frame out of styrene as I just couldn’t figure out how to adapt the Con-Cor/Kato drive for it.....



I checked the temp on this one the other night and was surprised to see it also got up to 107 degrees after one lap!

[kiwi_al]

How do you feel about running the two mechanisms upsidedown without their trucks and without their shells and measure the temperature as it is running. If the temperature is low then it's the drivetrain that is the problem. Just a thought.

[tehachapifan]

How do you feel about running the two mechanisms upsidedown without their trucks and without their shells and measure the temperature as it is running. If the temperature is low then it's the drivetrain that is the problem. Just a thought.

It's certainly worth a try, although I already know the drive produces a lot of extra resistance.

[peteski]

As far as coreless motors go, Bachmann ones are at the bottom of the pile.  They're ok, but not great.
To retrofit the loco with melted shell I would try to find a better quality motor which has a diameter and length as large as possible to fit inside the model.  The larger the motor diameter is, the more torque it will have. With extra torque it will not work as hard (or get as warm) as smaller diameter motors.

https://micromotor.eu has a wide range of coreless motors (they can be purchased through DM-Toys in Germany).

[tehachapifan]

Although it's been a while, I've visited that site before and recall not being able to figure out if I could get something with the correct length shafts. I'll check it out again.

[peteski]

Although it's been a while, I've visited that site before and recall not being able to figure out if I could get something with the correct length shafts. I'll check it out again.

They do have drawings: