Reply to "Tachometer Readings"

I did some bench testing and conducted some time trials with my Marx 333 Hudson-type 4-6-2 locomotive. The 333 is probably the finest locomotive that Marx produced. It weighs 2 lbs and 6.4 ounces.

My test rig, instrumentation and methods are described above.

I first bench tested the locomotive at 7 VAC, and the motor's amp draw was 1.14A, 7.98 Watts. Bench testing like this allows me to get a good idea of how much power it takes just to overcome the combined friction loss of the drivetrain.

I ran the locomotive only on the track described above, and measured the elapsed time to cover 5 laps, while also measuring the amperage, at 5, 6, 7, and 8 VAC. I did not go outside this range because the locomotive wouldn't run consistently at voltages less than 5, and would run dangerously fast at voltages greater than 8. My results are:

Without tender or passenger cars

I then ran the locomotive with its diecast tender and three lighted passenger cars on the track described above, and measured the elapsed time to cover 5 laps, while also measuring the amperage, at 7, 8, 9, 10, 11, and 12 VAC. I did not go outside this range because the locomotive wouldn't run consistently at voltages less than 7, and would run dangerously fast at voltages greater than 12. My results are:

With tender a three passenger cars:

It is interesting to compare and contrast the results when the 333 locomotive was operated at 7 VAC. On the bench, the power requirement was 7.98 watts. On the track without anything in tow, the power requirement was 10.71 watts. On the track with a tender and three passenger cars in tow, the power requirement jumped up to 14.7 watts.

The 333 runs slower than the 999, it is more powerful, and operates within a wider range of voltages. The 333 however, does not run very well on 0-27 tracks because the turns are too tight and the drive wheels get hung up, loose adhesion, and start spinning. Other differences between the 333 and the 999 - the 333 has smaller diameter drive wheels, so at comparable rpms, the 333 will run slower than the 999. The 333 has a gear ratio of 9.74 to 1. while the 999 has a gear ratio of 5.4 to 1. The 999's motor runs at much higher rpms than the 333. See my tachometer readings above.

One other observation, it takes a good deal of power to pull the lighted passenger cars - because of the rolling resistance of the wheels, and because of the resistive friction of the lighting pickups. I did some interesting testing of the rolling resistance of my train cars and I produced some interesting data which I will provide in a follow-on posting.

One final note on my 333 - it does not have an e-unit ( I physically removed it) and the headlight is an E10, 24V cold-white LED screw-type bulb. So my locomotive is running a little more efficiently than a stock 333.