Matching speed of two "identical" locos

[badgerV8]

This has been driving me nuts all day.....   

 

Two Heljan Class 17's, both draw the exact same current on DC at startup (0.11A), full throttle (0.21A) and stall (0.45A). Both have the same ESU Micro V4 sound decoders (from the same source), the exact same speaker installation and every single CV value is identical, with the exception of the top speed CV being 120 on one and 115 on the other to give the same speeds.

 

One moves off smoothly and accelerates smoothly and seamlessly to top speed in response to throttle. The other one starts accelerating smoothly, but has about 3 noticeable "speed jumps" where a throttle increase of only 1mph (Hornby Railmaster) gives a distinctly noticeable jump in speed.

 

I thought it may have been down to the speed tables being different but nope, they're identical....

 

I want to run these as a double-header, so any help / pointers / suggestions would be very welcome, thanks.

[WIMorrison]

Are they both equally well run-in? the motors in our model may seem powerful but compared to the effects friction can have they are weak and feeble.

 

that said, you will never get 2 locos to run exactly the same without changing the settings or alternatively using some external mechanism to match the speed such as a computer control programme or one of the handsets, e.g. Roco Z21 App that will do the speed matching for you.

 

I don't know of any shortcuts, sorry

[HLT 0109]

Speed matching is a time consuming and often frustrating procedure - I have done it several times with my 00 gauge locos (both steam and diesel) and you may find that you have to adjust the motor control for each loco separately until each runs at its best.  The prpcedure is set out in chapter 11 of the Loksound manual and would need to be done before speed matching.  You say you have matched top speeds - after adjusting motor control, you may find they need matching again - using the speed table and speed step 28.  However, it is best to start with speed step 1 and set the start voltage to that which gets each loco just moving - I run them one behind the other (better still, side by side on parallel tracks).  Once speed steps 1 and 28 are matched, then pick speed step 14 and get them matched by altering the appropriate CV value.  Bear in mind that, in order to use the speed table, CV29 must be set correctly. After that, it is a case of setting the intermediate steps, one at a time until you are happy with them.  I found it useful to write each one down as I set/altered them because you are almost certain to have to go back and change them slightly - especially if you then run on 128 speed steps.

 

In double heading , precise matching is not necessary but, if banking and there are sharp curves, it becomes more so.

 

Sorry if I am telling you what you already know but it is not a half-hour job.  Incidentally, using something like JMRI software or a Sprog makes the job easier but it is still time consuming.

 

Harold.

[badgerV8]

Thanks Iain & Harold.

 

The locos are both well run-in and free, the speeds are actually about as close as makes no real odds when sat at a given speed, it's the fact that one loco has definite noticeable (and audible, if sound is turned off) "steps" in its speed "curve" whereas the other is smooth as it accelerates, both speed tables being identical. I can't understand why one will seem to fail to accelerate with throttle input then suddenly step up a notch - it's almost like it has 8 speeds instead of 28 (or however many!).

[34theletterbetweenB&D]

It's a PITA, because all the settings will need reprogramming, but have you considered a reset on the troublesome decoder? I have lost count over the years of how many strange glitches in decoder performance have been eliminated by a reset. (Working guess, rectifies some small corruption of the operating software on the decoder.)

[SRman]

If you have JMRI Decoder Pro anda computer attached to your command station, you can save all the existing settings before doing a reset. You could then selectively rewrite the (for example) speed table settings back onto the decoder.

[w124bob]

Are they both equally well run-in? the motors in our model may seem powerful but compared to the effects friction can have they are weak and feeble.

 

that said, you will never get 2 locos to run exactly the same without changing the settings or alternatively using some external mechanism to match the speed such as a computer control programme or one of the handsets, e.g. Roco Z21 App that will do the speed matching for you.

 

I don't know of any shortcuts, sorry

I happen to have around a 20 Atlas ho 4axle locos, every single one bar 1 purchased over a decade could be matched simply by duplicating my standard speed table. Problems only arose when Atlas moved factories and the new one started to fit a different motor. I binned the motor, cannibilised an ancient chassis for a replcement and had no further problems.

[WIMorrison]

You are a very lucky man - I would buy a lottery ticket with the luck that you have.

[w124bob]

I wouldn't call it luck, Atlas 4 axle locos all share the same basic components, quality motors and well mould gears and Lenz decoders. The S series switchers being the exception but a shorter wheelbase bogie and smaller motor accounted for this. Now Athearn can be very hit and miss. I didn't have the same luck with my Baccy class 20's, 4 all completely different!