Adjust Roller Contact Spring Pressure on Lionel MPC GP9 8759....

[stjr]

First let me say how awesome this web site and this forum are. You "guys" are great! Now to my "challenge". I'm setting up my Christmas Village and as part of that I test run trains to make sure all tunnel clearances are good.

I ran my Lionel MPC 8759 and saw it was triggering the E-Unit over switches. So I checked the pickup rollers and noticed they don't have the tension they used to. It appears that over the years the roller contact spring (part# 8209-120, it's a flat piece of brass) has become bowed so the rollers are not maintaining good contact with the center rail. My question is, how can I get into the truck assembly to reshape the contact spring? I checked Lionel's exploded diagram (which I was able to find and download because of this great forum) for this power truck, but there is a plastic cover over the contact spring which the exploded diagram does not show. I included pictures to show you what I'm seeing for clarity. I can I remove the plastic cover to get at the contact spring?

I hope you can help!

Steve T

Prescott, AZ

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[cwburfle]

That piece of plastic is not just a cover. It is the bottom of an insert that is placed between the metal sides before they are staked together. Off the top of my head, that insert provides the lower armature bearing and two of the wheel bearings. It also holds that contact spring. It may do other things too, the idler gear posts MAY be part of the casting too, I'd have to look at a motor. You would have to remove the wheels and completely separate the motor's side frames to remove the plastic part. I don't think that is realistic. The only thing holding that contact spring in place is the little plastic stud in the center (shown in your picture). If you unsolder the lead wire, it may be possible to lift the spring off the stud and slide it out, but that might leave a bad bend in the spring. Are you certain the tension is reduced? Before heading down this road, I suggest a careful cleaning both the pickup rollers AND the wheels. On most MPC Geeps, you can add a 2028 pickup to the dummy truck. Doing so would solve any center rail pickup problems.

[stjr]

Hello CWBURFLE! Thank you so much for the quick response.I took a second look at the exploded view and everything, I mean EVERYTHING is held by (what Lionel calls) the truck frame. There's no way I'd tear into that!

But I LOVE your idea of adding a 2028 pickup to the dummy truck. I did that to the dummy unit so that it was lighted (nothing sadder than an unlit dummy unit) and it was easy-peasy. I will definitely go that route.

In regard to your asking if there is a tension problem; when I turn the engine upside-down, the rollers fall back to an almost level position. They hardly "stand up" at all. Another symptom is; the engine runs great on track until is encounters a switch. I surmise the rollers bounce when they hit the switch and break contact; triggering the E-unit.

Thanks AGAIN!

Steve

[ADCX Rob]

That spring is not sitting level in the truck frame for some reason, whether from physical damage or not seating right, but I've never seen one just lose it's "tune".

It is easily removed and replaced, and you may not need to unsolder the wire lead to it if there is enough slack:

Remove the rollers(w/o further distorting the spring):

Flex the spring UP in the center off the plastic locating standoff:

Slide the spring towards the fuel tank clearing the front crossmember:

Slide the spring forward toward the coupler:

And now it's free of the motor truck, secured only by the wire:

The spring should actually be quite straight across it's entire length until the slight bend that presses on the back of the rollers:

The installed spring w/o rollers should just give a little tension against the crossmembers:

Reverse the procedure to reinstall the spring.

[stjr]

Holy Crap Rob! This is just awesome! It looks completely easy to do. And the pictures are awesome! Thank you so much!

Between your's and CWBURFLE's suggestion I am good to go! Just one question, (and not to sound too stupid) what's the trick for removing the rollers?

Steve T.

[ADCX Rob]

Hold the roller in the fully extended(down on rail) position with needle-nose pliers in one hand, slip a slotted screwdriver between the roller bracket and the spring, giving the screwdriver a slight twist to disengage the spring from the roller tang and wiggle the roller bracket out and away from the spring.

It is literally a 4-second task.

[ADCX Rob]

[stjr]

Rob! I followed your procedure and I had the spring out faster than I could type "Abracadabra"! The spring was definitely bowed. It's just a brass strip. I curved it back the opposite way a bit and slid it back without issues. Thanks again!

CEBURFLE....the 2028 pickup is on order and should be in shortly. My GP9 will be rock solid!