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Model Railroading > consist "lurching"


Date: 09/18/22 08:15
consist "lurching"
Author: exrtc

Is there a way to eliminate the lurching that sometimes occurs when units are consisted?  I am using the same sountraxx mobile decoders in identical locomotives, clean wheels and track, with BEMF (CV 10) cut out ( set to zero).  CV's 23 and 24 are set to 128 in both engines.  When separated the locomotives run identically, but when coupled with a load they seem to fight each other, especially downgrade.

Chris Rye



Date: 09/18/22 09:10
Re: consist "lurching"
Author: sarailfan

Slack in the drive train (use thrust washers to eliminate lateral movements in the worm gears) and slack in the couplers. Sergent or equivalent have a prototype amount of slack vs the 6" or more of Kadees, and the difference is noticeable especially if you have a sticky car further back in a consist.

Posted from Android

Darren Boes
Lethbridge, AB
Southern Alberta Railfan



Date: 09/18/22 10:00
Re: consist "lurching"
Author: raytc1944

The same thing happens sometimes on the big roads.  I remember riding on an EMD and or GEs or ALCOS in mixed consists and it seemed like you were getting kicked in the butt.  This was caused by different makes/models loading up either slower or faster than the leader.  



Date: 09/18/22 10:30
Re: consist "lurching"
Author: ATSFSuperCap

While it is possible to reduce this from happening by installing washers on the motor armature and worms to reduce the slack or end thrust in the drive train in the end the spur gears in the trucks are over running the worm and jamming against it causing the motor and drive to stop rotating which is the cause of the learching.    If these are Athearn units check to see if they have plastic worms.    If so changing them to brass worms may reduce the problem.   Also using Labelle gear oil on the gears will help.    Unfortunately in the end physics is the decider.   That is why Hobbytown of Boston used true helical cut gears in the trucks as they will not bind up.    Do not confuse Walthers advertising saying they use helical gear drive, they are NOT helical cut gears just angle cut which does improve the running perfomance a lot and likely does reduce the gears jamming on the worm as they are cut to match the worm.    All the other drives just use straight cut spur gears in the drive.



Date: 09/18/22 10:34
Re: consist "lurching"
Author: exrtc

Thanks for the tips.  The units in question are Athearn Genesis. 

Chris Rye



Date: 09/18/22 10:51
Re: consist "lurching"
Author: ATSFSuperCap

Interesting.    I would not have suspected the units were GEN.    I have GEN F's and FP45's running and have not had the problem with them but my max grade on my helix is around 2 percent so maybe it is not steep enough to make this happen.   Another thing to try is run the units separated but down hill and speed match them that way.    Another try would be to set one unit to run slightly slower in an attempt to keep the gears from over running on the other units.   I have done the latter but it was on a pair of 2-8-2 steamers which were a severe mis match, one is a Broadway Limited totally rebuilt to ATSF appearance and the other is a Sunset brass ,  I set one to run slightly faster than the other to keep them from jamming up, it worked pefectly.



Date: 09/18/22 17:53
Re: consist "lurching"
Author: wabash2800

I would say that just because they are identical locos out of the box doesn't necesarrily mean they are speed matched. You may have to bite the bullet and try some speed matching. If Athearn can provide them with wheels out of gauge, they sure as hell can have other differences. A number of my Genesis locos wheels were out of gauge.

Victor B.




Edited 2 time(s). Last edit at 09/19/22 22:30 by wabash2800.



Date: 09/18/22 19:10
Re: consist "lurching"
Author: KA7008

FWIW, I have multiple Genesis locos doing the same thing.



Date: 09/19/22 08:40
Re: consist "lurching"
Author: funnelfan

Have you tried running them side by side consisted to see which one is running faster? Check the speed through the entire speed range. One may have a weak motor and is running slower than the other in all or part of the speed range.
 

Ted Curphey
Cheney, WA



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