Speed Matching

Speed Matching Locomotives

Once the decoder is installed in the locomotive, the job isn’t completely done. To get locomotives so that they can be used in consists (multiple locomotives running together) , they need to be ‘speed matched’. This includes locomotives from the same manufacturer and even the same locomotive model. Depending on the motor, gears, and amount of runtime (drag), most locomotives will run at different speeds. If hooked into a consist, the faster locomotive(s) will attempt to pull the slower locomotive(s) causing wheel slip, decreased pulling effort, overheated motors, and possible decoder failure.

Fortunately, decoders have the ability to speed match locomotives built in. The simple way is to use CVs-2 (starting speed), 5 (top speed), and 6 (mid speed). There are two different methods of speed matching locomotives: either by having a "standard" locomotive and then adjusting the other locomotive speeds to match or by using a standard length of track and figuring out the speed by timing the locomotive. For the club, it just seemed to make more sense to use the timing method. By using Atlas 11 radius snap track, anyone (who wanted to) could build their own speed matching track, although the club also has one for member use.

Using Atlas 11” radius snap track, we have a fixed, consistent diameter loop of track for testing. Next is to determine the circumference of the circle:

11 inch radius circle of track = 69.12 inches (2Rx3.14)

So now we can create a scale speed chart based on the distance:


Test Track	Radius >	*Module*	9 3/4" R	11" R	*Module*	12 3/8" R	13 3/4" R	15" R	19" R
Distance	Traveled >	*48"*	61.7"	69.1"	*72"*	77.8"	86.4"	94.3"	119.4"
	100	4.3 Sec	5.6 Sec	6.3 Sec	6.5 Sec	7.1 Sec	7.9 Sec	8.6 Sec	10.9 Sec
	95	4.6 Sec	5.9 Sec	6.6 Sec	6.9 Sec	7.4 Sec	8.3 Sec	9.0 Sec	11.4 Sec
	90	4.8 Sec	6.2 Sec	7.0 Sec	7.3 Sec	7.9 Sec	8.7 Sec	9.5 Sec	12.1 Sec
S	85	5.1 Sec	6.6 Sec	7.4 Sec	7.7 Sec	8.3 Sec	9.2 Sec	10.1 Sec	12.8 Sec
C	80	5.5 Sec	7.0 Sec	7.9 Sec	8.2 Sec	8.8 Sec	9.8 Sec	10.7 Sec	13.6 Sec
A	75	5.8 Sec	7.4 Sec	8.4 Sec	8.7 Sec	9.4 Sec	10.5 Sec	11.4 Sec	14.5 Sec
L	70	6.2 Sec	8.0 Sec	9.0 Sec	9.4 Sec	10.1 Sec	11.2 Sec	12.2 Sec	15.5 Sec
E	65	6.7 Sec	8.6 Sec	9.7 Sec	10.1 Sec	10.9 Sec	12.1 Sec	13.2 Sec	16.7 Sec
	60	7.3.Sec	9.3 Sec	10.5 Sec	10.9 Sec	11.8 Sec	13.1 Sec	14.3 Sec	18.1 Sec
S	55	7.9 Sec	10.1 Sec	11.4 Sec	11.9 Sec	12.9 Sec	14.3 Sec	15.6 Sec	19.7 Sec
P	50	8.7 Sec	11.1 Sec	12.6 Sec	13.1 Sec	14.1 Sec	15.7 Sec	17.1 Sec	21.7 Sec
E	45	9.7 Sec	12.4 Sec	14.0 Sec	14.5 Sec	15.7 Sec	17.5 Sec	19.0 Sec	24.1 Sec
E	40	10.9 Sec	13.9 Sec	15.7 Sec	16.4 Sec	17.7 Sec	19.6 Sec	21.4 Sec	27.1 Sec
D	35	12.5 Sec	15.9 Sec	18.0 Sec	18.7 Sec	20.2 Sec	22.4 Sec	24.5 Sec	31.0 Sec
	30	14.5 Sec	18.6 Sec	20.9 Sec	21.8 Sec	23.6 Sec	26.2 Sec	28.6 Sec	36.2 Sec
	25	17.5 Sec	22.3 Sec	25.1 Sec	26.2 Sec	28.3 Sec	31.4 Sec	34.3 Sec	43.4 Sec
	20	21.8 Sec	27.8 Sec	31.4 Sec	32.7 Sec	35.3 Sec	39.3 Sec	42.8 Sec	54.3 Sec
	15	29.1 Sec	37.1 Sec	41.9 Sec	43.6 Sec	47.1 Sec	52.4 Sec	57.1 Sec	72.4 Sec
	10	43.6 Sec	55.7 Sec	62.8 Sec	65.5 Sec	70.7 Sec	78.5 Sec	85.7 Sec	108.5 Sec
	5	87.3 Sec	111.4 Sec	125.7 Sec	130.9 Sec	141.4 Sec	157.1 Sec	171.4 Sec	217.1 Sec

Using OPS mode programming and start by setting CVs 2 thru 6 to "0".

Next get locomotive creeping; read throttle setting (DT throttle reads in %); multiply 255 X throttle reading/100 - use