The following can be used to calculate scale miles per hour for any scale and any timed length of travel. Best to use a stop watch to time the travel over a measured distance.
L = length of travel in inches
F = scale factor
T = time in seconds for locomotive to travel length.
Scale MPH = ((L x F/12)/5280) x 3600/T
Example: If it takes 5.2 seconds for a HO locomotive to travel over two straight pieces of Bachmann sectional E-Z Track.
L = length of travel in inches: 18 inches
F = scale factor: 87.1
T = time in seconds: 5.2
Scale MPH = ((18 x 87.1/12)/5280) x 3600/5.2 = 17.1 MPH
---------
To use Microsoft EXCEL
Cell A1 enter length travel in inches
Cell A2 enter scale factor
Cell A3 enter time in seconds
Cell A4 enter the scale MPH formula =((A1*A2/12)/5280)*3600/A3
OR if you don't have a calculator handy ;)
Divide MPH by 5 to give Inches per second.
60MPH/5 = 12 Inches/Second.
Multiply Inches per Second to give MPH.
18 Inches/Second X 5 = 90MPH
Dear Stewart,
Have a hot Cha & recline with a good [model railroad] magazine.
Works for me. :)
For those with aching heads, there are speedometers available. For example, see: http://members.shaw.ca/dispatcher/misc.html#speedometer
I posted one of the headache causing formulas.... and I myself use a "Speed Scaler" .... bought it from the Accucraft booth at the Springfield show years ago .... it's a bicycle speedometer mounted on an aristo truck with a talgo mounted coupler .... you can set it for whatever scale you like (1/29, 1/22.5, 1:20.3 etc.) because it asks for a calculation of the bicycle's wheel to calibrate it.... it comes with a table for the correct values.
Once programmed, you couple it to the rear of your train, and it displays the speed (and distance, even) on the screen as the train passes by!
Matthew (OV)
Quote from: Mark Damien on February 14, 2007, 06:36:03 PM
OR if you don't have a calculator handy ;)
Divide MPH by 5 to give Inches per second.
60MPH/5 = 12 Inches/Second.
Multiply Inches per Second to give MPH.
18 Inches/Second X 5 = 90MPH
Mark, your method works for HO scale only.
Ooophs, I'm in the General Discussion area - not HO.
I'll just take myself outside & give myself a good sound thrashing. ;D
In addition to all of the excellent analyses above, here's another way to keep it simple. 88 feet per second for 60 MPH works in any scale if you use scale feet. Therefore, take a scale rule (a good thing to have anyway if you don't want to be constantly calculating) and measure 88 feet along the right of way. Then a train crossing that distance will be going a scale 60 MPH.
Cheers, Ken
Stewart, I have read and reread your response (2 posts up) and do not know what you are unhappy about. Are you possibly confusing "thread" as in a bunch of posts that are somehow related, with "string" as in "string theory?" Bill Baker was basically saying he liked the simplicity of counting box cars and seconds approach to estimating speeds. He also mentioned string theory as something that would really confusion if we discussed it here. (Maybe Bill and I could collaborate on a "String Theory of Model Railroading" thread sometime on a slow day. ;D)
For a simple explanation of string theory, click on this link:
http://superstringtheory.com/basics/basic4.html (http://superstringtheory.com/basics/basic4.html)