Over heating trains when going all the time

[spzero]

Hi all, we have a few 9 volt trains that race around our shop window and it's great, passers by love it and so do we, however on a hot sunny day (like today) they keep stopping due to the motors overheating. I know I could just stop them or swap them over more frequently but its not the highest priority when trying to run a business, any help with reducing problems running for extended periods would be great if anyone has any tips.

[dr_spock]

You could install an awning outside the window to provide some shade if your local bylaws permit them. Put some fans inside to blow cooling air over your train layout. Paint the train motors a light color to reflect light and heat. Black gets hot under the sunlight. You could hook up the transformers to a programmable timer and set up cycles of running and resting/cooling.

[Zerobricks]

Or reduce their speed?

[legoman666]

run it with a lamp timer, 30 minutes on 30 minutes off.

[jtlan]

Do the motors actually feel hot to the touch, or do they just stop working? I know a lot of clubs remove the thermistors from their 9V motors, which appears to be a common repair for motors that stop after running for not too long. While the thermistor is there for thermal overload protection, I've heard that it is a bit overzealous (and only gets worse with age).

[Ashi Valkoinen]

Or reduce their speed?

Reducing speed means heating up your 9V speed regulator, since on lower voltages (lower trains speed) it dissipates the not used perfomance as heat.

[spzero]

Thanks Everyone, train motors are really hotting up when its sunny, (the Maersk train seems to be the worst culprit but also the heaviest,) but happily run all day when the sun is less bright, like today, a timer would be okay but want it going as much as possible, but maybe I can give them a few 5 minute breaks in the afternoon when sun is at it's hottest, A fan could work (I have a wind turbine on it's way from bricklink, shame it hasn't got aerodynamic blades as if it did it would work as a fan) Maybe a little motor driven windmill could work placed next to the track with the right elements, .

[lightningtiger]

Reducing speed means heating up your 9V speed regulator, since on lower voltages (lower trains speed) it dissipates the not used perfomance as heat.

Why ?

Lower voltages mean lower current flow hence less power.......Ohm's Law states that current is proportional to voltage and inversely proportional to resistance, plus since total power (useful + wasted) equals the product of voltage and current leads to less Volts means less Watts.

Now a 9V controller uses a LM317 if my research is correct.....memories of trade school when I built a variable power supply.......it only got hot if you draw heavy current, since the motor has resistance it will take a higher voltage for said current to flow. Lower voltage means lower current flow, less magnetic flux with less field strength to boot to cause the motor's rotor to rotate.

Now a fresh idea......could there be a mechanical reason for the stopping......i.e. motors bearings ?

[legoman666]

Why ?

Lower voltages mean lower current flow hence less power.......Ohm's Law states that current is proportional to voltage and inversely proportional to resistance, plus since total power (useful + wasted) equals the product of voltage and current leads to less Volts means less Watts.

Now a 9V controller uses a LM317 if my research is correct.....memories of trade school when I built a variable power supply.......it only got hot if you draw heavy current, since the motor has resistance it will take a higher voltage for said current to flow. Lower voltage means lower current flow, less magnetic flux with less field strength to boot to cause the motor's rotor to rotate.

Now a fresh idea......could there be a mechanical reason for the stopping......i.e. motors bearings ?

Because it uses a crappy linear voltage regular that dumps excess voltage as heat. At full speed, it's simply passing on the 9V from the input to the output. At the slowest speed, it's dumping about 200mA x 7V = 1.4W onto an internal heatsink. The motor itself doesn't experience this, but the circuitry inside the speed controller.

Motors are not as simple as resistors. The voltage across them decreases as their speed increases. So say you're running it at full voltage and you stall it. You'll have 9V across the motor. But if you let motor spin while still supplying the 9V, suddenly you'll only have 4-5V across the motor. The other 4-5V will be back EMF. And if you had an "ideal" motor at 20C at sea level blah blah blah, it'd have no voltage across the motor, but would produce 9V back EMF. And then the current through the motor is related to the voltage across it divided by the resistance of the motor coils.

Source: I'm an electrical engineer.

Edited April 21, 2015 by legoman666

[Heppeng]

I think Ashi might have been thinking of old fashioned train set resistance type of controllers. Set them on a slower speed (higher resistance in the controller) they can get hotter. I don't think lego made any like that, unless the old blue 12V controller was? The others use transistors which don't dissipate heat to slow the train down, they just cut the power.

[spzero]

i did lightly oil the motor as that was my first thought, Yesterday I tried my little shunter going around with a small load behind it, and it was fine despite the heat, so I think I need to just lighten the load and all should be well.

[Q3671]

lower the primair power 230 V~ to 200 V~ then the secundair power go 9 V= to 8 V=

[Brickthus]

I take it you are using a standard 9V controller? This provides smooth DC power, which is good, so lowering the voltage by 2 speed settings should help a lot. A bit more heat in the regulator is OK - it can cope with that.

If you were using a 12V controller (as would be used for the 12V lamp posts) then I would recommend not using that to power 9V trains - the motors hate the half-wave-rectified power of the 12V controller and this would make them buzz and quickly heat them up.

I have used a dual variable 30V 3-Amp bench power supply to control heavy 9V trains at exhibitions. I often run at no more than 7V, often as little as 5V. This power supply has smooth power and heatsinks for its transistors so it can supply lower voltage all day.

Other than that, minimise the friction in your train wheels. The road-rail vehicle has tiny wheels that would cause more friction. The 12V wheels of the truck also have more friction than most 9V wheelsets (except the ones that were problematic a few years ago). Check with each wagon that the wheelsets rotate freely for a long time when spun with the wagon upside down. Also reduce the weight of any heavy wagons. Weight adds load to the motor, which reduces back-EMF, increases the current and the motor heats up in proportion to the square of the current.

Mark

[spzero]

thanks everyone I am using the LEGO 12 volt for the lights (and also the scalextric car) and the LEGO 9v for the train, It has been much better with a smaller and lighter load (the rail road car is not the best but it was a little different and I applied a drop of oil to each wheel and it wasn't a problem (I wish I could have a longer train but its not happening) the train pictured has been the happiest but I keep changing the rolling stock and engines etc for variety. thanks for the help guys n girls