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Hi all, I have a P2K SW9/1200 which is driving me nuts. I have a switching layout and love locos that crawl along at very slow speeds. This SW runs very nicely in one direction, but in the other direction it "hunts" a bit, and its most noticable at slow speeds. I've taken it all apart, cleaned out the old crap in the gears, lightly oiled it and while its a touch better, it still does it. I know I'm being really picky, but I don't get why its good in one direction and not the other.
When I hear "hunting" in reference to train operations, I think of a truck pivoting back and forth so the flange on one side hits the rail then the flange on the other side hits the opposite rail. It has been identified as the cause of some crashes. I think you mean something else though.
The odd thing is, my GP60s do it as well, but only while I run them together. If run individually, they don't have that problem. They are speed matched, and the BEMF is turned off on DCC.
The label I use for this behaviour is "jack rabbiting".
On a loco I have which had such a problem, the cause was the pick-ups on one truck having an alignment which led to a lose of contact in one direction. The intermitent power supply seems to have led to jack rabbiting.
This is one possible reason you might investigate. I'm not familiar with p2k loco pick up systems.
Other reasons could be dirty wheels (an alternative on the intermitant pick up thesis), or even shorts. I believe the p2k SW1200 has an issue with metal trucks and an unfortunate deisgn of picking up motor power from the chassie. If DCC, you'd know this by now as the decoder will get smoked.
Mechanical reasons would be buckled wheels, out of gauge wheels, or binding somewhere in the power train. The former can be tested with the NMRA wheel and track gauge. The later with an analogue mutli meter and a good'ol fashion transistor throttle.
For testing power trains for binding, test the motor independantly first (ie: remove it). Set the meter to mAmp and DC current (from throttle: + to meter then chassie, -to chassie). Test motor at 12V DC and record result (a Mashima might be about 30mA or so. Some brands of motors draw a lot more).
Then systematically add the drive train components, testing again at each step. Also watch the annalogue dial for wiggles. This helps you find the binding section. And that's all! This method is used to test kit build steam loco chassies but is also useful for trouble shooting issues such as described in this thread.
