These engines tend to buck coming down hill with a train. Hope buck works, or maybe jerks ? Anyway we put washers in the running gear to take up the slack… Helped but not a cure…
Anyone have any futher fixes ?
When we run two together it appears to get worst.
Any help would be appreciated
Not an expert, but hope this helps.
[1] Are you using a quality powerpack like an MRC Tech series? Really makes a difference in performance.
[2] Did you check the axles as well? Mine bucked and made clicking noises. I had to replace all six axles on a new GP9. After a good long break in run on a friend’s layout, she’s a smooth runner. Your GP7 may be like my GP9. 1st or 2nd run that sat on a shelf for several years.
Same answer from the Atlas forum. Check out NW Shortline web site. Look for the 3/32 thrust washers. They really help in taking the slop out of the gears.
not know about that the engines i’ve work good
Yup, too much play in the drive shaft, need some additional thrust washers around the worms and then they will run fine.
–Randy
When coming down a hill your locomotives are taking in the stress of the train behind it and what will tend to happen are the motors trying to hold back all that wieght so that it doesn’t speed up, so your getting a jerking. When you add locomotives to the train it tends to happen with all of them. The last loco on the train will be slowing down because of the wieght of the train wanting to come down wants to go and then your second loco will speed up because its feeling that the train slowed and now it wants to go. And then if you have a third loco on, the second locomotive will want to go because the the last loco wants to slow down and in reaction the first locomotive wants to slow down because your second unit wants to go. This is probably whats happening and to fix this is to make your hill less steep or make your trains shorter. Theres really not alot you can do about it. Its just how an electric motor works.
James
If your layout is DCC there was a post (by Rinker I think) abouy a type of decoder that creates the same problem. If I remember correctley the decoader was set up like a cruise control on a car. Sorry for the lame reply…tooo much grey hair and mileage I guess…John
Not really, you’re thinking about Back-EMF and the only way it would cause any sort of jumping would be if it was set way too strong, so that the decoder ‘overreacts’ to load changes. Even then it wouldn;t buck back and forth, but rather make noticable jumps as the speed changed instead of smooth changes. The problem here definitely is the excessive end play in the worm gear bearings at the top of the truck. I have 3 P2K GP-7’s and they do the exact same thing. One was really bad - it was missing the single (inadequate) washer that is installed at the factory. I need to order the NWSL washers and fix mine up.
–Randy
Switch your pack out before you tear apart the loco. Sometimes when a pack starts to get weak or is getting old it shows up as voltage and amp drops. When the loco is coming down the grade it has just crossed the highpoint in the grade which makes the train and cars free wheel for a short time. When it comes down the grade there is one point in which the cars are really pushing hard on the loco, which changes the amps then. Going up is fine though for you as I can see, coming down is a different story, so change packs just for a simple test first.
try to get some gear lube its common for locos to sit in the boxes for so long that only a short run in will (dry) them out
imoa