PW GP-7 stalls as lead collector truck wheel contacts switch frog

[kpolak]

When the engine enters a switch from the turnout side, the front wheel of the collector truck contacts the frog, and the engine stalls, and trips the e-unit.  The e-unit can be cycled, and the engine can continue on, but this is annoying.

This doesn't happen at all switches, only 2 of 11 but it doesn't happen with any other engines, leading me to suspect the Geep.  I also have a 1666 steam loco, and a 8111 switcher.

I have checked:

1.  That the fiber pins are in the correct spot. 

2.  There is Power at the switches.

3.   The track, and GP-7 wheels are clean.

Suggestions?

Kurt

[lionelsoni]

First determine whether a momentary open circuit or short circuit is stepping the e-unit:  Shut off the e-unit and run through the switch while watching a light, other than the locomotive's headlight or an analog voltmeter, powered from the track voltage.  If the light flickers as you go through the turnout, the problem is a short circuit, otherwise an open circuit.

[kpolak]

Thanks Bob!

OK,  the light flickers:  Short Circuit.

What next? 

Kurt

[chuck]

How many pickups are on the GEEP?  Is this a single arm pickup on one truck, a pair of single arm pickups (one on each truck), paired pickups on one truck, paired pickups on both trucks?  E-units trip when current is cut/inrrerupted.

Are all of the other switches the same type (aka O-22's)?  If so, the problem may be in the switch and not the loco but the arrangement of the pickups on this particular loco may be more susceptible to the problem than your other loco's.

[kpolak]

Paired pick-ups on the collector truck. 

The problem only occurs when the engine goes thru the switch, motor first.

Kurt

[Frank53]

I am having a similar problem with a post war New Haven 2350. Stalls over the switch. The "thumbtack" coupling device seems to make contact with the frog. It is a lazy coupler that hangs a bit low. Had it repaired, brought it home, ran it over one switch - boom - it's lazy again. May need to replace the entire assembly.

[chuck]

Check the spacing on the pickups and compare it to the length of the piece of moveable center track that forms the switch point.  The loco's pickup roller wheel base may not be able to bridge the point and the engine may cut power when crossing the points at slow speed.  If this is an O-22 switch, the wire that feeds the point is probably not making good contact with the switch point.  I had this happen and it was a pain to diagnose because the switch would sometimes work and not others.  The weight of the loco would either cause the wire to seat or unseat.  When I took the unit apart I could see the solder joint had failed and this was causing the odd behavior.  A loco with a different pickup arangement would crusie through the switch because there was always one pickup making contact either in front of or behind the moveable point.  Only a loco with just the wrong spacing would stall and cycle the E unit.

[kpolak]

Check the spacing on the pickups and compare it to the length of the piece of moveable center track that forms the switch point.  The loco's pickup roller wheel base may not be able to bridge the point and the engine may cut power when crossing the points at slow speed.  If this is an O-22 switch, the wire that feeds the point is probably not making good contact with the switch point.

I'm comming into the switch from the radius turnout side, and the rollers don't get to the moveable center.  As soon as one wheel hits the plastic frog point, the unit shorts.

Kurt

[chuck]

Which model switch?  The insulating pins are not on the same rails on all switches.  O-22 uses the "outside" rails, the 1122 uses the inside rails.  If you have the pins on the "wrong" side, there may not be a return path for the electricity to compete the circuit.  The plastic frog won't conduct and if the outside rail is isolated, you may not have a return path.

[kpolak]

These are the O22 switches.  The fiber pins are at the yellow stickies.

Kurt

[chuck]

Does it stop running when it hits the metal insert in the frog or when the outer wheel hits the second built in isolation block on the outer rail just past the beginning of the outer  plastic "gaurd rail"?

[kpolak]

It stops running when it hits the metal insert in the frog.

Kurt

[chuck]

If this only happens on two of the switches it seems most likely the problem is in the switch.  There are jumpers and straps in the switch base that make the non derail function work.  One of these may be loose or shorting against something else, particularly one of the other rails.   Olsen's Toy train site has the service manual on line.  If you have a multimeter with a continuity function you can compare the switches that work with the two that don't to see if there is a pattern of failure. 

The insert should be tied to the non control rail.  If it isn't, or the weight of the loco causes the insert to become "isolated", the engine will stall.  The control rail is supposed to be isolated and on the outer side there is a 3/4" gap between where the second built in isolator on the outside rail ties back into the main return circuit.

Does the Geep have traction tires? 

[lionelsoni]

I don't have an 022 here to look at, so this is guesswork:  I see in the service manual that there is an "auxiliary rail" that starts just at the point where the frog meets the curved rail and extends several inches into the middle of the turnout.  It is not so much a "rail" as a plate apparently intended for the wheel flanges to run on through the frog.  It is wired internally, with actual wire not a strap, to the straight outside rail.  The wire seems to pass very near the center-rail strap.  If that wire has come in contact with the strap at that place, the part of the wire between to point of contact and the outside rail may have burned out.  The wheel flange may be deep enough to contact this (improperly and perhaps intermittently hot) "auxiliary rail" to produce the short circuit.

So you could look for track voltage on the auxiliary rail, perhaps with a little pressure on the probe.

[kpolak]

This is a Lionel 2338 w/magnatraction.

Nothing uncommon electrically with the switches, working correctly and not.  I installed card stock under the wire connecting across the center rail.

The power seems to disappear as the as the front wheel on the control truck rides up on the plastic frog, until the opposite side wheel contacts the curved rail, after the control rail, about 1/4" in travel in total.

It seems like the rear wheels of the rear truck are not connected to each other when they get to the track.  The rear wheels should take care of the ground as the front wheel rides up on the frog, and disconnects.

I've checked the front and rear wheels of the truck for continuity, and they check out.

Thank you,

Kurt

[chuck]

The two switches that give you problems, are the turnouts on the same side, aka left?  Are these opposite of the ones that work with the loco?

Also, when you were testing continuity on the switches, did you try putting pressure on the suspect parts to make sure it isn't the wieght of the loco contributing to the problem.

[kpolak]

One's a left one's a right.  Both a problem in the same spot, when approached from the turnout (radius) side.

I did apply pressure, no change in continuity or resistance.  It seems to be linked to the front wheel leaving the rail, and riding up on the frog, until the wheel contacts the aux rail.

Kurt

[chuck]

On the switches that do work, does the loco behave the same way regarding riding up on the frog?

I pulled up the service manual for the loco. There is only a single wire feed from the pickup collectors to the hot side of the E-unit.  If the two switches you are having trouble with cause the truck to ride rough and the pickup wire is loose, it might cause a momentary interupt in power and trip the E-unit.  There are plenty of return paths for the current off of any wheels on any of the four axles, but only a single power pickup.  Along the same lines, check the springs and pickup arms.  If only one of them is making good contact and it's the one being bumped at the frog it might also account for the current interupt and the cycling of the E-Unit.

[kpolak]

On the switches that do work, does the loco behave the same way regarding riding up on the frog?

  The other switches all work correctly, and the anti-derailing is in great condition.

The two switches in question seem to be a newer pair.  Flat head screws secure the baseplate, instead of the hex style 'mini bolt' of the other switches.  The only similarity so far has been that the aux spring clip at the booster pin isn't springy enough to connect when the constant voltage plug is removed.

  There are plenty of return paths for the current off of any wheels on any of the four axles, but only a single power pickup.  Along the same lines, check the springs and pickup arms.  If only one of them is making good contact and it's the one being bumped at the frog it might also account for the current interupt and the cycling of the E-Unit.

I cleaned everything, wheels pick-ups, wd40'd the contact rollers until wd40 ran clear out the bottom of the pins...then a good dousing of the denatured alcohol.  I also re-checked resistance in all the collector parts back to the pick-up wire.

I recently rebuilt the loco.  (aha......) no really, this is all correct all the way back to the e-unit, all fresh wire per the Greenburgh repair guide.

Everything inside the switch seems to be origional, and in very good condition, and I just cleaned all the internal contacts as well.

I think these two have me beat...Keep this problem in the back of your head and you might wake up one night with A-HA!

Thanks for all the help,

Kurt

[kpolak]

If the two switches you are having trouble with cause the truck to ride rough and the pickup wire is loose, it might cause a momentary interupt in power and trip the E-unit.  There are plenty of return paths for the current off of any wheels on any of the four axles, but only a single power pickup.  Along the same lines, check the springs and pickup arms.  If only one of them is making good contact and it's the one being bumped at the frog it might also account for the current interupt and the cycling of the E-Unit.

I owe you an apology Chuck.  You solved it here and I missed it.

I set-up a line of old track, and deformed the tops a bit, some sides, some center rails, and it's something in the collectors, causing the power outage.  I can't tell if it's at the springs or in the rollers.  But that's it.  Everytime I hit a bump it shorts.

I'm ordering a new collector/roller and spring assembly today if I can find one.

Thanks,

Kurt

[chuck]

Glad to hear you got a bead on it.  To be completely honest, this type of incident is what sold me on Command control.  I had a loco that could only "go right".  Every time it hit a left handed turn out, wham, derail and a big short circuit.  I couldn't see what was going on from the console and everytime I had someone try to "help", things went bad.  With the CAB-1 I could sit right there and play it out in slow motion.  It was a bad pilot truck spring.  Looked fine on straight aways, could take curves no problems.  Hits the frog on the switch and "boingggg", off she goes.  Good luck with the repairs.