[PRCo] PCC speed

[Boris Cefer]

Today we tested our rail grinding car after an extensive overhaul. The car is quite common PCC car (Tatra T3 type), but with air applied rectangular grinding blocks instead of rear track brakes. For the purpose of rail grinding the car is stripped of field shunting to obtain lower balancing speed. There is only one field shunting contactor (F) which provides full field shunting of rear motors' fields during coast.
We made a speed test with following results: 25" wheels, cca 700 Volts, full field, slight downgrade about 0.2% and the speed we gained was 60 kilometers per hour, aka 37 miles per hour.
Adjusted to 600 Volts and tangent level track, we can expect balancing speed approximately 30 mph. Of course, this figure cannot be accepted as an objective indice and we would have to test several more cars under similar conditions, but it gives some idea what the balancing speed of PCC car would be if the field shunting was not introduced. Also remarkable was that after cutting out all accelerator's resistance, the rate of acceleration became obviously lower than in case the field shunting was applied.
Boris