REPOWERING  GUIDE

RPM TABLES

For Popular 12 Volt Motors

Can Motor Background

During the mid 1970s various importers started selling models with compact efficient motors.  These motors had been developed for tape drives, camera drives, electric shavers and other portable electric devices.  They were readily adapted for use in model locomotives.  Not all of these motors were successful as used.  Some really bad motors needed replacement.  Fortunately suppliers like NWSL, ProtoPowerWest jumped into supply the hobby with replacement motors.  Some importers like Kato, West Side Models and others stocked replacement motors for their models.  In the 35+ years since,   Internet sellers on sites like eBay have added quality motors, sometimes unmarked to the available supply.  Some unmarked, unlabeled motors are included in the table below;  help in identifying these mystery motors would be appreciated.  The motors have been organized by width.  Note: A photo of each motor is linked to the Photo Number in Column 1.

Motor RPM Test Information

Brand Model Number Shaft Size Width        mm Height   mm Length       mm   MOTOR   RPMs 12 Volt
Photo Start 2 volt 4 volt 6 volt 8 volt 10 volt 12 volt Load mA
M-26 WestSideModels    (quiet) 1230 1.3 12.7 12.7 30.1 40 1375 2985 4570 6075 7735 1000 2.4
M-5 Johnson Controls unmarked 2 15.4 20.2 32 360 1170 2400 3660 4980 6230 7870 8
M-6 Mabuchi FF-180PP 2 15.4 20.2 32 335 1095 2400 3600 4800 6060 7660 10
M-1  Ebay ??  Double End unmarked 2 15.4 20.2 32 650 1360 3100 4500 6230 7900 9675 56
M-24 Taneda 1627 2 16 16 27.2 500 3000 9200 13100 18700 23600 24500 41
M-7 Sagami                (quiet) 1630 2 16 16 30 40 1530 3630 5550 7400 9700 12900 80
M-25 Taneda 1630 2 16 16 30.4 150 2000 4325 6650 8950 11600 15000 27
M-13 KATO HM-5 2 17 20.5 33.2 140 900 3100 4950 6850 8625 10975 52
M-2 Canon                   (quiet) EN22-R11       CN22 -03 2 18 21.9 32.8 125 1340 2850 4195 5685 7210 8865 36
M-4 Canon DN-22               CN-22 2 18 21.9 32.9 110 1200 3000 4440 6050 7560 8920 50
M-20 Canon         Double-Ended w/Universal EN22-712N      CN22 2 18.1 21.7 32 25 1245 2915 4430 5970 7575 9090 40
M-14 Nissei unmarked 2 18.1 20.8 33 1300 810 1800 2675 3665 4525 6000 12
M-16 Mabuchi FA 2 18.2 24 30.4 53 1800 3830 6000 8100 10150 1285 76
M-8 Mashima (2335) 2 18.3 23.5 33 425 1175 3150 4725 6375 8120 10150 56
M-18  Ebay ???  unmarked 2.4 19.4 21.8 39.7 350 1450 3225 4900 6900 8600 11000 135
M-3 Pittman PG6212A008    10.8 volt 2.6 19.6 22 31.9 275 1010 2525 3940 5350 6720 7750 92
M-9 Sagami 2032 2.4 20 20 32 200 1280 3210 4800 6830 8500 9900 82
M-21 NWSL 20324          Single End 2 20 20 32 465 1205 2765 4475 5950 7650 9225 76
M-22 Mellor 2032           w/Flywheel 2.4 20          25.3 20          25.3 32 100 1355 3450 5445 7520 9360 11400 83
M-23 Canon CM 22 2 21.7 21.7 32.8 45 1900 4800 7800 10600 13300 15000 120
M-10 Sagami 2236 2.4 22.2 22.2 36.8 60 1215 2990 4850 6510 8300 10100 80
M-17 NWSL 22403 2.4 22.2 22.2 40.2 720 600 1710 2720 3810 4860 6900 70
M-11 KTM 2336 2.4 23 23 36.3 36 810 2185 3600 5020 6400 8460 125
M-19 WI M7T0726A 3 25.3 SQ 26.4 12 285 1110 1900 2720 3500 4580 62
M-12 Sagami 2835 2.4 28.4 28.4 35.3 600 900 2160 3100 4200 5280 6760 60
M-15 Holland 990412012602 3 29 29 40.5 44 670 1535 2280 3160 3960 4850 13

Test Methodolgy

The motors tested were held securely in a small mill vise; 1/8" heavy foam wrap cushioned the motor in the vise. Power was from a 15 volt rectified AC power supply.  Since most of us operate using rectified AC power; using such a power supply matches our needs more than a straight DC supply like a car battery.  Voltage was recorded using a 4" averaging meter.  A Simpson multi-tester was used for current readings.  Key to the test was a Model TC 802  digital photo tachometer distributed by Meter Depot.  This tachometer utilizes a red laser beam and reflective strips mounted on the motor shaft. Without the strips results varied widely and were unreliable.  At least five tach readings were taken at each voltage and then averaged and then rounded to the nearest multiple of 5.  Start RPMs are when the motor starts to turn smoothly. Some hobbyists think that this a good indication of low end torque, it is included at their request.  Note that one of the lowest START RPMs was recorded for motor M-26 which is the weakest motor tested; it was imported in a few models that were shipped without boiler weights. With the addition of a gearhead it was used successfully in several geared logging locos.

The Mechanism

Most Japanese models like the KTM model shown on this page used an assembled brass frame riding on coil springs on bronze bearings on each driver axle.  Early KTM models had an enclosed non-idler gearbox, with typically a 27:1 gear ratio.  Many large drivered engines might have a 37:1 ratio gearbox.   A large KTM open frame motor provided dependable power, connected with flexible tubing to the  gearbox.  The flexible tubing also restricts movement of the gearbox, keeping it aligned with the motor shaft.  While the tubing transmits power to the wheels, it also consumes a lot of energy keeping the gearbox aligned, raising current draw.  The photos below show a non-idler gearbox mechanism connected to the open frame motor by a short length of flexible tubing.  Note: the motor is mounted on an angled portion of the frame to align with the gearbox.

 



Modifications - Installing the Can Motor and flywheel

The motor shaft on this model is 2.4mm, a common size on Japanese models.  This is also the worm shaft size of KTM gearboxes.  NorthWest Short Line (NWSL) 2240 can motors also have 2.4 mm motor shafts.  The original MG-KTM frame had a motor mount angled to align with the gearbox.  This angled portion of the frame was milled off level with the bottom of the frame to allow the motor to be mounted level.  Two motor mounting holes (2mm) were drilled thru the frame to attach the motor.  The motor if mounted with a section of K&S channel running the length of the motor.  Since one of the motor mounting screwheads might interfere with the trailing truck it was countersunk into the frame.  The sides of the channel can be spread outward to lower the motor, if necessary.  Extra length 2mm screws were used to attach the motor.  They  pass through the frame, brass channel and into the bottom of the motor providing a strong secure motor mounting system that allows for quick disassembly and replacement.

Notice that the flywheel is mounted on the back of the motor.  This puts the flywheel in the steam locomotive model's cab, where there is more room for a larger diameter flywheel.  The larger diameter  provides a greater "flywheel" or coasting effect to the model when the track voltage is reduced or interrupted.  I no longer press fit flywheels onto motor shafts.  Instead I use a NWSL hand reamer that matches the motor shaft diameter to achieve a tight slip fit  and then use Loktite to secure the flywheel to the motorshaft.  Oil the motor bearing before mounting the flywheel, apply Loktite to the hole on the side of the flywheel that will be away from the motor.  This should prevent Loktite from entering the motor bearing next to the flywheel.  Test the motor/flywheel combination before mounting by running the motor at various speeds while held in your fingers.  The motor vibrations should be minimal, the same as they were before the flywheel was installed.

The new motor, flywheel, and drivetrain are a different profile than the original KTM components; modifications may be necessary to fit the superstructure.  Most of the work is enlarging the bottom for clearance for the large diameter motor and flywheel.  I use a variety of tin snips, files and carbide Dremel cutting burrs.  On models imported with idler gearboxes, the cast boiler weight has a notch to clear the gearbox.  A similar notch was carved using Dremel carbide burrs.  This is best done with the weight out of the model.  If the lead weight rest on the gearbox, interferes with the universal drive, or the flywheel rubs on the superstructure, when tested your ears will tell you that you have more modifications ahead.

Epilogue

I have used several can motors in brass models like those from KTM.  For all but the largest engines I use a NWSL/Sagami 2032 can motor. Originally these motors had 2.4mm shafts and were more rugged and durable than flat can motors like the Canon CN2231.  For smaller engines I used the Canon motor but recently switched to the Kato motor used in their HO diesels.  The flat can motors have 2mm shafts and do not tolerate the larger flywheels I like to use as well as the 2.4mm shaft motors.  For installations limited to small 16mm diameter flywheels these flat can motors are excellent.  For the largest KTM HO steamers I prefer the hard to find KTM 2336 can motors; the NWSL 2240 is a good substitute as is the slightly smaller and less powerful NWSL/Sagami 2236 can motor.