Speed Matching Tips and Tricks Part 2


In my last post I wrote about some observations I’ve made in my experiences using the Bachrus Speedometer to do speed matching. This time I’m going to describe the steps I go through for my locomotives.

I start by setting up a spreadsheet to keep track of the speed table in scale miles per hour that will be used to map the CV values to actual speeds. It would look something like this (completely made up numbers):

Speed Step Scale Speed Loco 1 Loco 2
1 2 15 18
2 4 20 23
3 6 25 28
28 56 100 105

The first column is the speed step as it maps to the actual CVs, the second column is the target scale speed. Then there is a column for each locomotive that is going to use this table. The values correspond to the CV values that result in the desired scale speed.

To get these values I start with a locomotive and put it on the speedometer, before I start figuring out CV values I run it for a while on the rollers to make sure the motor and drive train are warmed up. Once I’m ready to start I use JMRI and OPS mode programming to set all of the speed steps to the same value which should be relatively close to the target speed (largely a guess) and then I take a throttle and set it to the maximum speed and adjust the steps until it matches the target speed. At this point the speed table is flat.

Next I pick the next speed and move adjust every step except the first one until I find the second step. I basically repeat this for each step, leaving each find value in as I go so by the end you’ve got your full table. I also copy this to information to my spreadsheet as I go for safe keeping.

Once you have more than one item set up you can start testing them together. You’ll want to pay attention to the acceleration and deceleration programmed into the decoder, if you find a locomotive behaves differently going in reverse you can tweak the forward and reverse trim and if a locomotive just needs a little help getting started you can program in some kick-start.

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