Support - Motor

In this article, you can find information, tips, and help regarding questions you may have surrounding motor control and troubleshooting motor problems.

Locomotive Running Backwards (of Headlight Operation)

What is important is observing the direction of the throttle/controller with respect to the directionality of the locomotive's motor and its functions. If the motor control alone is reversed of the selected direction of travel, you should simply swap the orange and grey wires to the motor. If the lights alone are reversed of the selected direction of travel, you should fist ensure that CV29 is not improperly configured. If CV29 is configured correctly (an even number) then you may have mistakenly entered incorrect values for the lighting CV's (49 and 50). If BOTH the motor and lights are reversed of the direction of travel, reconfigure CV29 to reverse the directional conditioning of the decoder.

How to Test a DC Motor

Motor/Brush Integrity Test:

1. (Do not install a decoder) If you have a DC dummy plug, it may be helpful for this test. Do not install ANY decoder, jumper, etc. at this time.
2. Use your multimeter to measure the resistance between the motor brushes. An initial reading for a typical HO-scale motor should be between 60 and 300 Ohms. Record this initial value on a piece of paper.
3. Rotate the flywheel while the meter is connected and checking resistance. Record the highest and lowest values you see on the same piece of paper. If this value is significantly higher than 500 Ohms, or is less than 100 Ohms, this indicates a bad motor. You may do as many revolutions as you like. We recommend a minimum of two full revolutions.

Motor Current-draw Test

Requires: A) DC power supply of at least 12V B) single, loose piece of track C) wheel rollers (recommended):

1. If available, install the DC dummy plug. If you do not have one, short the track and motor terminals, or run alligator clips directly to the motor terminals from the track pickups inside the locomotive.
2. Get yourself a separate, isolated piece of track. This track MUST NOT be connected to ANYTHING except the locomotive's wheels.
3. Place the locomotive on rollers, or otherwise hold it in place.
4. If you have a DC power pack, connect the Positive side to one of the rails (doesn't matter which).
5. Leave the Negative side of the DC power pack disconnected.
6. Set the DC power pack to 12 to 14 Volts. You should verify the voltage by using a DC voltage check function on your multimeter. Once set, disconnect the multimeter from the DC power pack.
7. On your multimeter there should be a third terminal (red) for checking DC Amperes. Move the Red lead from the Volts/Ohms terminal to the Amperes terminal.
8. Run an alligator clip from the Negative side of the DC power pack to the Black lead from your meter.
9. Set your meter to DC Amperes. If your meter has multiple settings, use the highest one.
10. While the power pack is still set to 12 to 14 Volts, touch the Red lead of your multimeter to the OTHER rail (Negative rail). Your meter will now create a complete circuit and the locomotive will start running the motor.
11. Record the idle DC Amperes while the locomotive is not under load. This value should be in the 100's of milliamps.
12. Hold the engine back, or press down (while on rollers) to add a load. Be generous with your force, but do not fully stall the motor.
13. Record the peak DC Amperes. This value must not exceed 1 Ampere. If this value exceeds 1 Ampere by a significant amount, the motor is not suitable for a 1 Ampere rated decoder.

Steps to Improve Motor Performance

TCS recommends following the below sequence of operations if you find your out-of-the-box motor performance to be unsatisfactory; however, if you are observing poor motor performance, it is more likely that your motor is in a failure condition, or is not of sufficient ratings/quality to be used with a DCC decoder. An example of one such motor would be a "pancake" style motor such as those found in older Rivarossi models. For best performance, TCS recommends motors with at least five, skew-wound poles and an iron core.

There are hardware factors which can affect the performance of your motor such as:

1. Stray or added capacitance across the motor terminals - if preset, any capacitor(s) in the motor circuit MUST be removed; elsewise, this stray capacitance will hamper or motor control. NOTE: Bachmann locomotives are guaranteed to have a capacitor placed in parallel with the motor. This capacitor will have noticeable negative effects on our motor control and must be removed.
2. Number of poles - motors with less than 5 poles will inherently not have as good of performance, especially at slow speeds. These motors can also make a lot of electrical noise (any audible noise).
3. Motors which are NOT skew-wound - having a non-skew-wound motor means that the electromagnetic field within the motor will not be interacting with the poles of the motor with as much consistency, resulting in dead times with weaker magnetic attraction between each pole. Skew-wound motors offer more consistent and smooth operation.

The ideal motor setup is a 5-pole skew-wound iron-core motor without any added capacitance or inductance.

Other factors play into the smoothness of your motor control. The most notable troublesome factors are:

1. The "tightness" of the drivetrain and gearing - In many cases, especially at slow speed, slight bumps and jerks are caused by slack in the gearing being eaten up or not. It is possible for the motor and flywheels to be rotating smoothly, but not the actual wheels due to the tolerances within the meshing of the gears.
2. KeepAlive is not installed or being used - It is impossible to perceive the loss of track power, but whenever a decoder  does not have perfect power pickup, the power supply will no longer supply power to the components (obviously). As such, the bulk capacitance on the decoder's power supply will be drawn from for the brief time power is interrupted to get the decoder through the interruption. Generally speaking, the voltage charge is less than the track power. As such, the maximum voltage and peak PWM voltage to the motor will be less for a short period of time. If you are very keen in your perception (and congratulations if you are), you can observe these "micro jerks" as the locomotive crawls. Using KeepAlive with a decoder that you are observing this situation on will clean up these observations because the decoder will continue to have power as supplied from the KeepAlive device.
3. Keep Alive IS being used but the power pickup is unacceptable - When using Keep Alive, it is possible to observe the track power disappear, unlike in the previous example. Since Keep Alive tends to power the decoder at a lower voltage than the track, when a decoder switches to Keep Alive power, it may slow down slightly. This is more obvious at high speed and when crawling. If you are observing jittering with Keep Alive installed, start by cleaning your track and wheels, and inspecting your pickups. You may have a loose or broken wire.

If you are not satisfied with the motor performance at slow speed, you should go through the following steps in order:

1. Use CV 29 to select the speed curve you would prefer to use
2. If using the 3-point speed curve, verify that CV 2, CV 6, and CV 5 are set to 0.
3. If using the 28-point speed curve, verify the value of CV 67 is less than the value of CV 68 (CV 67 default value = 8)
4. If using the 28-point curve, decrease the value of CV 67 to a value that is not 0.
5. If you are still not satisfied with the performance of the motor at this point, verify the values of CV 66 and CV 95. Both should be set to 128 by default. It is not recommended to modify these values unless you are running in a consist.
6. If CV 66 and or CV 95 are greater than 128, decrease as necessary to 128.
7. If you are STILL not satisfied with the motor performance, decrease the values of CV 66 and CV 95 by 4 at a time until you are satisfied. For sound decoders, you can alternatively use the Speed Matching menu in Audio Assist to make these adjustments in real time while the engine is in motion.

Note that you will observe superior performance always when using 128 speed step mode. Speed step 1/28 is equivalent to roughly speed step 3-4 in 128 step mode.

Coreless Motors

When using coreless motors you should not experience issues with speed control or overheating unless your model has a defective or poorly-manufactured motor. Generally speaking, the technology and manufacturing process for coreless motors is still on the leading edge, meaning the years of refinement seen in iron-core motors has yet to be realized. As such, each motor will inherently behave differently than others, and will result in potentially erratic control, especially at slow speeds or low RPS.

TCS prides itself in having the best motor control in the industry, attributing that quality to our auto-adjusting BEMF algorithm. Depending on the quality of the motor and the characteristics therein, this algorithm can be thrown for a loop at slow speeds. Over the course of the last two years we have made great improvements with coreless motor performance, but have found that the performance is really dependent upon the motor itself and not the decoder.