Speed matching issue on different layouts

[jagged ben]

So the somewhat bizarre update to this is that the source voltage is higher at the club, where the locos run slower.  Using the sum-of-DC-to-each-rail method, it comes out at about 14.7 compared to 14.0 on the Zephyr at home.  (The different club boosters vary by about .3V too).    Which basically means it has to be a voltage drop issue.  Accurately measuring the voltage drop is difficult though, without the 'Gnd' terminal on the club boosters being handy to the track all around the layout.  I ended up testing with the club multi-meter's AC setting, since it seemed to be decent at measuring the real DCC voltage on its AC setting, being only about .2V different on the no-load measurement compared to the DC.   Testing a handful of locos I got as much as 1.85V drop at full throttle accelerating.    At home the same MM measured a max drop of 0.08V on the AC setting, and 0.03V using the DC method (a little imprecise since I couldn't be sure I was always measuring with the same load). 

So... still a bit of unknown involved.   But I'm thinking that I will just order some diodes and try dropping the home test track voltage 1.4V, rather than try to simulate the voltage drop at home.   I think all I really need is for the decoders to get enough voltage at the club compared to my test environment that they will start moving at the same low speed steps. 

[peteski]

Too bad you don't have a RRampmeter handy. That way you could accurately measure the DCC voltage on the track right next to the loco (both at home and at the club).  That would take out all the guesswork or workarounds using standard multimeters.

Any possibility that the club would spring for one of those (for all the members to use)?  Or maybe one of the club members has one of those RRampmeters at home and would be willing to let you borrow it?  My NTRAK club has a RRampmeter in its inventory.  It comes in handy for troubleshooting.

EDIT: fixed spelling - my brain has a problem spelling RRampmeter.

[jdcolombo]

Listen to Peteski.

A RRampmeter is an essential diagnostic tool for a large club layout (or even a large home layout) that uses DCC.  Not cheap (about $100 for the latest version with all the bells and whistles; a stripped-down, but still functional original version is about $70 from e-tailers), but a fraction of the cost of a top-level Fluke multimeter that will also read these voltages.

Lots of places sell them.  Do a search for RRampmeter (all one word).

John C.

[mmyers]

Get an 1156 light bulb  and a socket for it from the local auto parts store. Use it to place a load on the rails while measuring track voltage. That should put about a 2 amp load on the rails. test all around to see if there is uneven voltage. The layout may need some wiring improvement.

Martin Myers

[jagged ben]

The layout definitely needs wiring improvement, and that is realistically a twenty-year ongoing project that we are half-way through and will likely have to begin again once it is finished.    Kinda-like painting the Golden Gate Bridge, it is never over.  That would be a whole other thread and I'm not going to go into the details.  I mean, jeeze, there's only a couple actual miles (not scale miles) of wire involved.   Also, for the most part, it works fine, and it will almost certainly be much easier to make my locos fit the club situation than vice versa. 

What I'd appreciate here is any electrical theory to help ascertain the best way to reduce voltage on my test track to get a functional facsimile of the club layout with higher v-drop.   Or, alternatively, if anyone thinks there's a better explanation than relatively high v-drop at the club, I'm all ears.

I'm planning to order some diodes and try that method.  Keep in simple stupid.  If that produces a satisfactory adjustment when programming loco speeds then good.  If not, I'll be looking for other solutions to adjust the test track voltage.

[Maletrain]

If the problem is really voltage drop due to loads in different locations with different wiring issues, then it seems like the speed matching problem would be different in various places on the club layout, and maybe also different at different times in the same club layout location if some other loads besides your consists are in the same power sector.

If I was the one trying to do something about the perceived problem, the first thing I would do is make a test at home that could demonstrate that the actual problem is the DCC track voltage under load.  I think the diodes would help do that.  Or maybe you could switch power supplies or set the voltage in the DCS - I am not familiar with your particular DCC system at home. 

I would speed match a pair of locos that are giving you problems at the club using your regular home setup.  Then add diodes (or whatever) in the home setup to reduce your track voltage there and see if that produces the same mismatch as at the cub.  If so, at least you now have a way to tune the consists at home to have the best average performance at the club.  You will probably need a loop to test at home, not just a few feet of track.

If the problem proves to be DCC track voltage, then I would take the consist to the club and measure the track voltage across the rails when your consist is on them at multiple locations to see what a good average would be to use at home to speed match for cub use when using your home system.  It is important to use the same volt meter for all measurements across the rails.

As long as the rail voltage under load at the club doesn't vary to much from location to location and time to time, it should be possible to get reasonably good speed matching for club use.

[jagged ben]

Yeah that's more or less the plan.  Since the Zephyr comes with no features to adjust the voltage, I'll drop the voltage with some diodes and see if that reproduces the behavior I see at the club.  If it does. I'll reprogram some locos, take them back to the club and see if tue speed matching stays good this time.  If that plan doesn't pan out we'll look at next steps. 

Currently waiting for diodes to arrive by mail.