I intend to install a decoder in an old Athern PA1. Pretty new to all of this so following advice in books I decided to make it a smooth runner on dc before starting conversion. Had an old Sagami motor that I used to replace the Athern Motor. Thought that would miraculously make it a silky smooth running drive train. Nope. It still starts slowly and then binds after a few inches to maybe a foot of distance at low voltage/slow speed running. BTW it’s worse forward than in reverse. Next, I replaced all that old suspect drive train with clear rubber tubing from the local hardware store. Had to put tooth picks in it to keep it from flopping around but the tube now runs true and straight as a temporary measure. Didn’t fix the problem. Next I used Pearl Drops tooth paste to burnish all the gears. That didn’t work either. Neither did a bunch of other things I tried. everything has been cleaned and lightly lubed more times than I care to think about.
I am amazed at the amount of slop between the large gear and its mounting peg/post that it runs on. I can take it all apart one more time and measure if you need me to but I have a feeling that this a “standard problem” with a standard fix???
Will the trucks roll freely when it is off the engine? If so look at the trucks again. If they roll well, try adding or replacing the washers in front or rear of the worm gears.
When you say bind, do you mean the engine locks up, or just does not run well?
Are the axle gears split? It’s happened to me before with Athearns, and that will cause a good bind no matter what you do. Athearn still makes replacement gears for their newer diesels, but they can also be used for the older ones if you have an NMRA standards gauge to check the wheel distance of each axle.
Looks like Athearn had at least 4 versions of the PA1. If you have lost the part diagrams, you can probably find your particular model here: http://hoseeker.org/athearn.htm.
If that part is really sloppy, I can see where the worm could cause the gear to rack from side to side causing a problem. As J. W. asked, does the truck itself roll freely when disconnected from the motor drive?
The trucks roll freely with the worm gears removed. I have checked. All wheels drop perfectly into the guage.
Binding: the train runs 5 to ten MPH for a few inches and then stops. At that point I can nudge the fly wheel a little to get it going, or increase voltage quite a bit or reverse direction.
Thanks for the quick replys, I will try extra washers on the worm gears.
Like Darth said, I would check for split axle gears, which can cause the hesitation you’re describing every time the split between the teeth comes into mesh with the truck gearing. The truck may still freewheel without a hitch because there isn’t much load when you roll it, and there might be at least one other good axle gear to do the work of the bad one.
Actually split axle gears won’t cause the binding…You will hear that “thump” thump" thump" of crack gears.
Sounds more like a drive shaft bind…
I would check the drive by hand by turning the flywheel.I would remove the drive shaft from one side while doing the check.This will isolate the problem.
Is the motor seated correctly? The motor must be completely seated or it will cause a bind in the drive shafts.
If this hasn’t run for awhile I would check the contact between the trucks and chassis. In fact I would look at all the electrical contacts before I did anything else. Is the motor good? Check it by connecting it directly to the power. Put the drive shafts back in. Check the axle gears. Clean the wheels. And don’t forget the most important thing, give it a kiss on both couplers.
My dad has a couple of P2K GP9s that had bad gears. They would go for a ways, then bind up and stop. Back up a bit, and they would go again. Replaced the axle gears and all was well.
