WOW - Subjective train speeds and actually measuring them!

I just received an Accutrax II Speedometer, and have been trying it out on my test layout. Pulled a couple of "convenient" locos to see what speed they really run at.

Well, I am flummoxed! I had set up speed curves / tables based on what looked right to my eye, as I watched the units going around the JACALAR. Well, they were SPEED DEMONS. What I thought was a sedate 30-40 smph was in the 60-70 smph range. I knew, at shows, that I needed to keep my locos on the bottom half of the throttle, but now I know why.

So, for my next trick, I will start creating custom tables for my roster, such that I can "read the speed" from the throttle setting. Was figuring I would take my "main line" locos (passenger and freight) and set the speeds so that (for example) throttle 10 = 10smph; 50 = 50 smph and 100=100 smph. And then take branch / smaller units to maybe a max 60 smph; and take switchers / yard units to a max 45 (or lower)

Would be interested to learn how others set their speed tables / curves

 

Before a recent op session, several of us tried to run trains through my Accutrack II Speedometer at what we thought was 5, 10, 15, 20, 30, and 40 MPH on my N-scale layout and on my HO switching layout. While some operators' first attempts at specific scale speeds tended to be closer to the desired scale speed than other operators', most of our first attempts through the speedometer at a particular speed were missed on the high side...regardless of whether we were running in HO or in N. After an evening of running trains at what I thought was closer to scale speeds, I went back and tested myself against the speedometer again...and, although I definitely ran closer to scale speeds after the session than I had before, I was still running too fast.

Tweaking speed tables so that % of power used matches MPH may work for some locos, but others may be geared so that 90 to 99% power only yields 45 to 50 MPH. With some of my locos, I've noticed that, even when set at the same % power, they will go through the speedometer at different speeds when running forward than when running in reverse. Also, when making repeated runs back and forth through the speedometer at a set % power, some locos pick up 5 to 10 MPH from the 1st passes to the 9th and 10th passes...suggesting % power and MPH that match exactly when an engine is warmed up, may not match as precisely when the engine has sat unused for a while. I haven't tested it on my helixes yet, but I wonder how much MPH at a certain % power will change on a grade. And how much difference is there when pulling 3 cars vs pulling 30 cars.

Even if we can't establish an exact % power to MPH match, it would still be useful to have a "ball park" % that would be relatively close to the desired scale MPH.