RailPro > RailPro Specific Help & Discussion

MU Problem

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nodcc4me:
Hope that works. Let us know.

KPack:
Ron, if you are running the two engines light (no cars), you might see the rear one "hunt" a little.  This is most likely because the lead locomotive is experiencing no load, therefore it's trying to figure out what to tell the rear locomotive to do.  Lead experiences no load = rear locomotive slows down.  When the rear locomotive slows down = lead locomotive senses a load and tells the rear to speed up.  When running a train, there is a constant load on the lead locomotive due to the weight of the train behind it.  Any adjustments that the rear locomotive makes are minor and not noticeable because the load is never fully taken away from the lead locomotive. 

When you get a chance, run both with some cars behind and let us know what you find.

-Kevin

ronp:
Kpac, thanx for the reply.  I'll try that very thing.  Again, it will be a bit.  Having an outdoor layout allows the weather to exclude some days from operation. 

G8B4Life:
I can only echo what Kevin has said, though I'm not entirely sure that's exactly how it works; it is interesting that Rings own video shows and claims that two loco's running MU'd but not coupled run at the same speed with no train attached, even if one of them is significantly faster than the other one when run by itself. For an experiment try running them MU'd but not coupled together and see what they do.

The only thing I can really offer further than re-running the full load current test for each loco is that the lurching your experiencing (hunting is a different train phenomena) may be exacerbated by the couplers you use; if there is a lot of slack between the coupler faces then there is more distance for the loco's to lurch before any load is transferred and compensated for.

- Tim

ronp:
Good weather today so was able to get the trains outside on the main.  Both of the recommendations I received helped solve the problem.  First I redid the load tests on both locomotives.  It took me a few tries to get valid tests.  Just doing this greatly reduced the hunting problem of the second loco.  I ran them linked both coupled and uncoupled.  I then drove the locos outside with about 30 cars; everything seemed to smooth out.  I ran the train back and forth, up and down a 2% grade at speeds from a crawl to moderate.  All went well.  I would like to thank both Al and Kevin for their help.  Frankly I was somewhat lost.

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