How do you measure scale mph in HO?

[bearman]

This thread begs a question.  Are the speed steps on a DCC system linear? For example, is step 6 double the speed of step 3?

[Spalato68]

This is interesting question. I have never measured it, but it can be checked relatively easy, measurng several "control points" on a speed curve. 

Hrvoje

[tstage]

bearman

This thread begs a question.  Are the speed steps on a DCC system linear? For example, is step 6 double the speed of step 3?

They can be if that is the default of the OEM decoder.  More than likely it will be slightly exponential - i.e. with a gradual slope at the beginning (Vstart) and end (Vmax) of the speed table and a sharper one nearer the middle (Vmid).

Tom

[jrlyman]

I have been using an Excel Spreadsheet which I created. One can select ANY length of track (in inches), use a stop watch to measure the time for the train to traverse that selected distance, and read the train speed in miles per hour directly from the chart. I believe that my method is easier to use than any of the methods shown here. I don't know how to put it into this forum but will email a copy to anyone who asks. I can email you the Excel spreadsheet or a printout of ANY selected distance that you choose. All you will need is a stopwatch. I use various easy-to-generate printouts of my method quite often.

http://[e-mail]

[RailfanS]

One option that I haven’t seen mentioned yet is a different product from boulder creek engineering. It’s called their RollBy speedometer and consist of a board to be mounted in a car and an phone or tablet app. Although it’s more expensive than the measured distance and stopwatch method but I find it pretty useful for speed matching. I made a review on it recently: 

RollBy Scale Speedometer Review/ How I DCC Speed Match
https://youtu.be/W1F_A-l12xI

[bearman]

tstage

 

 

bearman

This thread begs a question.  Are the speed steps on a DCC system linear? For example, is step 6 double the speed of step 3?

 

They can be if that is the default of the OEM decoder.  More than likely it will be slightly exponential - i.e. with a gradual slope at the beginning (Vstart) and end (Vmax) of the speed table and a sharper one nearer the middle (Vmid).

Tom

 

 

Based on your response, I consulted the BLI Paragon3/2 manuals.  There is an interesting graph, identified as Motor Speed Curve, voltage vs speed step.  The factory default shows a linear relation between voltage and speed step, which leads me to believe that there is a linear relationship between speed step and locomotive velocity if the default is not fiddled with, at least for these two decoders.

[pomilian]

 For anyone interested, I have built two different speedometers based on the Arduino. One is stationary and built as a passthru over the tracks; The other is a rf transmitter unit that rides in a car and a handheld receiver display.

If interested in building something like this, please contact me off-line for more information. 

pomilian(at)sbcglobal(dot)net

Paul O

[garya]

For our friends who use the Metric system, I came up with the following formula:

(.0357 X Scale Factor X Distance in Centimeters) / Time in Seconds=

Speed in Kmph

If you want meters for your distance, use 3.57 as your multiplier.

Scale factors are the same, 160, 87, etc.

[bearman]

Using an Accutrack II speedometer, I measured the scale velocity for a range of speed steps with a PowerCab throttle.  The relationship is not necessarily linear and I suspect that it is decoder and/or weight of the locomotive dependent.

[ndaily]

Here's another way to measure speed.  Set two markers 176 scale feet apart and use this chart:

MPH	5	10	15	20	30	40	60
sec.	24	12	8	6	4	3	2

Cheers!
Nathan

P.S. just to be clear, the number of seconds to go between the two markers will give you MPH. -N

[Wolf359]

That looks pretty easy to set up. I have a chart that shows HO scale feet that I'll have to dig out.

[DR DENNIS GORDAN]

In the 1950's the New York State Thruway warned drivers that, at 60 mph, the limit at the time, a car was traveling 88 feet per second, so don't tailgate. Anyway, that means, since HO is 1/87 full size, one actual foot per second is virtually 60 scale miles per hour, each foot per minute is a scale mile per hour, each inch per second represents 5 scale mph.