Calculating speed

[GRandIfan]

I am running On30 and would like to know the speed of the train by knowing the discance and the time it takes to travel the specified distance. For instance, in a test, I marked out .0742 of a mile and it took 44 seconds to travel that distance. However, I do not understand how to acurately calculate speed.

[RR_Mel]

I use this calculator.

https://www.modelbuildings.org/scale-speed-calculator/

 

Mel



 
My Model Railroad   
http://melvineperry.blogspot.com/
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.

[mbinsewi]

That's an interesting site Mel, Thanks! 

Mike.

[wjstix]

Well, if a train takes one minute to go one mile, it's going 60 MPH. Doubling the amount of time it takes to go a mile reduces the speed by 1/2. So if it takes 2 minutes to go 1 mile, it's going 30 MPH. 4 minutes = 15 MPH. 8 minutes = 7.5 MPH.

Once you have those as the base speeds, you can fill in the in-between. If 60 seconds = 60 MPH and 120 seconds = 30 MPH, then halfway between in time - 90 seconds - equals halfway between in speed - 45 MPH.

In US O scale, 110 real feet equals one scale mile. If you can set a speed test zone that's 11 feet, you can calculate the speed by moving over the decimal point...if it takes a train one minute to a mile, it's going 60 MPH; if it takes it one minute to go 1/10th of a mile, it's going 6.0 MPH.

[gregc]

GRandIfan

I marked out .0742 of a mile and it took 44 seconds to travel that distance

0.0017 mile/sec = 0.0742 mi / 44 sec

0.101 mile/min = 0.0017 mi/sec * 60 sec/min

6.07 mile/hr   = 0.0017 mi/sec * 3600 sec/hr

 

[xdford]

I have a web page site which gives you two strategies to do the measuring.  While I use Telegraph poles, there is no reason why the markers could not be granite veins in rock, tall pine trees, fence lines etc and I cover N HO and O in the page...  Let me know if it is useful to you,  

https://sites.google.com/view/stagnesrailway06

Cheers from Australia

Trevor

 

[dstarr]

Speed in miles per hour is computed by dividing miles by hours. 

  You have to convert your measured distance into scale miles.  I measured the length of my mainline with a steel tape, giving me a distance in real inches.  Multiply that by 87 to make it HO inches.  Divide by 12 to make it HO feet.  Divide by 5280 to make it HO miles. 

   I used a stopwatch to time the train giving me an answer in seconds.  Divide by 60 to make it minutes.  Divide by 60 again to make it hours. 

  A calculator makes things easier.

[Doughless]

Very good points.  On my layout, it will be important to know if the train is traveling more or less than 20 mph.

[Overmod]

"Speed" is a measure of distance in a particular time ... or the time it takes to go a particular distance, like the distance between mileposts.  It does not have to be expressed in a 'standardized' way to be useful, but by convention we've come to express it in distance per unit time -- the time sometimes being in unit seconds, as with revolutions per second in steam locomotive design, or in unit minutes as in feet per minute, or in unit hours as in miles per hour.  The unit you use depends on what you intend to do with it -- and of course you can interconvert any given 'speed' value nto any other mathematically.

Part of the 'unit' choice carries over into measuring accelerations, which are in some English-unit calculations measured in 'feet per second change per second' (sometimes abbreviated fpsps and NOT spoken as an acronym unless you are Elmer Fudd).  You could always express this in mph/s, and some people do; you can express this in a time to reach a particular distance, as in eight- and quarter-mile drag racing, or a time to reach a particular velocity, as in 'zero-to-sixty' times or their metric equivalent.

Europeans can screw this up in the same way they complicate mileage by expressing it in liters/100km, which aside from being a decimal number with relatively little numerical change for serious economy differences is not useful for most 'guesstimate' purposes regarding vehicle mileage without some conversions difficult to do in one's head.  Do not make this mistake when deciding what 'formula' (or algorithm) you intend to use in your particular situation.

[Overmod]

Doughless

On my layout, it will be important to know if the train is traveling more or less than 20 mph.

Theoretically the 'easiest' way to accomplish this is to use the VASCAR method: use detectors that flag something on the locomotive or a test car very precisely -- it might be when the locomotive darkens a photosensor reliably, or crosses an electrical gap, or breaks a light beam -- and then precisely measures the time between two sequential activations a known distance, which can be a short distance, apart.  With a reliable timebase, you can measure the time between the two activations precisely, and the result adjusted to the unit used for distance (for models that might be inches, in metric centimeters, and in SI millimeters) will give you the speed directly, which you would then convert to scale mph.

"Scale mph" of course relates to denominating the test "distance" in scale miles, or feet, or whatever, which you might mark off or 'calibrate' using a scale rule.  That would remove some calculation steps and opportunities for 'error'...

[NorthBrit]

I am just curious.

 

Once a train has taken 44 seconds to do a journey  around the layout and there are four journies per day;  when does the next train depart?  Do you wait a length of time before the next departure?

 

Just curious.

 

David

 

[gregc]

  sc-dist  sec    mph
   0.0742  267      1.0
   0.0742  134      2.0
   0.0742   89      3.0
   0.0742   67      4.0
   0.0742   53      5.0
   0.0742   45      6.0
   0.0742   38      7.0
   0.0742   33      8.0
   0.0742   30      9.0
   0.0742   26.7   10.0
   0.0742   17.8   15.0
   0.0742   13.4   20.0
   0.0742   10.7   25.0
   0.0742    8.9   30.0
   0.0742    7.6   35.0
   0.0742    6.7   40.0
   0.0742    5.9   45.0
   0.0742    5.3   50.0
   0.0742    4.9   55.0
   0.0742    4.5   60.0