Run Away Consist

[SCL1923]

Hi all,

I am looking for some advice from ones who have had a run away problem and then hard braking in a consist.
I run mostly 7 to 12 passenger car services with 4 loco's, Athearn Genesis F7's ABBA hard wired with Keep Alive all in great working order with a prototypical speed of 50-60MPH. I have a helix of just under 2% grade.
I am having difficulty with an understandable small increase in speed on the downgrade and then hard braking, back to normal, then hard braking again until it gets out of the helix. I've gone back & forth with using the Top Speed at 100% then at about 60% with not much difference. I double checked & all the software/hardware is up to date.
Even without coaches behind, I am still having the same problem, although perhaps slightly less braking. All wires inside loco's are well soldered and track and wheels are clean. I've basically ignored this for a year, but honestly it's getting the best of me.
Also a shout out to everyone going to the Rocky Mountain Train Show in Denver this weekend!

Chris

[ON28]

Perhaps hard-wiring four motors together magnifies the effects of uneven track/roadbed and voltage variations?

I have the same issue, the draft (stretching) and buff (compressive forces) on my trains in my compact 28-inch radius, 3-1/2 turn octagonal helix. Remember, the compensated grade is steeper than designed due to the effects of curvature, my infrastructure isn't perfectly even, and the 1:1 railroads deal with the same competing forces within a train. I speed-matched my locos which are all KA-equipped, but even with load sharing some diesels (Atlas, Intermountain, Bowser) just MU better than others (early P2K). As with the prototype, train handling matters, so operators can't just leave their train to descend the helix and must pay attention to changes in current and voltage and max downgrade speed. As it should be.

I can't speak to long passenger trains, but you may want to see if you can shim any low spots/lower high spots in the track.

 

[SCL1923]

Thanks for the reply, but I feel the need to clear up a misconception. The motors are hardwired separately with there own LM3-S module in each locomotive. Each loco is separate from each other. Thankfully there aren't any low and high spots in the 36" radius curvature in the helix so I can rule that out. I'm starting to think that even though RailPro advertises communication between linked locomotives that helps with push pull, downgrades of 2% is just too much. Which is unfortunate because load sharing is the main reason I went with Railpro, & I really don't think a 2%- downgrade is too much especially for 4 linked locomotives controlling the same speed. None of my DCC consists have this problem on the same downgrade. It's almost like the communication of speed parameters between the loco's needs to be tightened up. I really hope there is a solution out there.
Just returned from The Rocky Mountain Train Show...busy...busy. Love it!

[faithie999]

Send Tim Ring an email describing the situation and see what he has to say.

[William Brillinger]

I find it best to pick up the phone for support from Ring.

[G8B4Life]

Do any other RP equipped loco's do this when MU'ing in the helix? Do any of the F7's display this behavior singularly? as a pair? when going downgrade? While I don't doubt that the load sharing might not work as well downgrade as it does on the level and upgrade I've not heard of anyone reporting this before and I'm confident that others have run MU's downgrade as well so it would be good to eliminate all those variables.

- Tim

[Josephbw]

It sounds to me like a gear lash problem. As you go downhill the play in the gears will allow the engine to surge forward, then the lash is taken up. and it slows down. On a long downhill run, this will take place multiple times. The cure might be shims behind the brass gear in the trucks.

Joe

[William Brillinger]

"It sounds to me like a gear lash problem."

I was thinking the same thing.

[SCL1923]

Do any other RP equipped loco's do this when MU'ing in the helix? Do any of the F7's display this behavior singularly? as a pair? when going downgrade? While I don't doubt that the load sharing might not work as well downgrade as it does on the level and upgrade I've not heard of anyone reporting this before and I'm confident that others have run MU's downgrade as well so it would be good to eliminate all those variables.

- Tim

Thanks Tim, I have 2 sets of 4 F7's MUed that DO display this occurrence and one pair of SDP40F's MUed with 12 coaches that DO NOT display this problem. And a couple of singularly run steam loco's that Do Not display this occurrence.
This morning I tested a single loco with 12 passenger coaches with no occurrences. Adding a second loco however, DOES display this problem. Also got out my inclinometer and measured the gradient of basically 2%.

[ON28]

"It sounds to me like a gear lash problem."

I was thinking the same thing.

Also called cogging.

[SCL1923]

Na, although there is some slop in the Athearn Genesis gears, the others are Walthers Proto with helical gearing which are tight...tight.
These are also brand new within two years of purchase with well worked in motors.

[TwinStar]

I have a friend in Chicago who has a layout with grades and he installed RailPro in a portion of his fleet. None of them, not a single one, would operate correctly going downhill. They would buck and kick like you can't imagine. He wound up ripping the LM's out, giving them to a friend of ours, and going back to DCC. His experience jumped to mind when I read your post.

[ON28]

I have no problem running my HO diesel fleet up and down my 28-inch radius, 3-1/2 turn helix. There is some slight buff (pushing) and draft (pulling) in a train, as with the prototype, but a good engineer can and should manage that with careful handling.