Calculating scale speeds

[Paul M.]

How would one calculate the scale speed of a locomotive? Model Railroader does this a lot, but they don't seem to provide a method or equation for calculating this.

[pdlethbridge]

 At 60 MPH a car is going a mile a minute. If you divide a mile by 87 you get 60'+ .  At 60mph in a model train would cover 60+feet in 60 seconds, a foot a second, if it was 30 mph, it would take 2 seconds to go a foot, 6 mph, 10 seconds. If you increase the distance you increase the time by the same amount at the same speeds.

[Yampa Bob]

Check this site:
http://www.spec2000.net/rr_site_pages/rr_scale_dfn.htm

Here's the formula:
Scale Speed (mph) = 1/88 (a constant) X Speed (feet per minute) X Scale Ratio.

Note that for HO scale, the 1/88 constant and the scale ratio (87/1) nearly cancel each other out in the equation.  Therefore for HO scale "Feet per minute" = ~Scale miles per hour.

Measure the distance around a loop, say it's 20 feet.  Time one lap, say it takes 10 seconds for the lap.  That's 120 feet per minute or 120 scale mph. Very simple.

[SteamGene]

Great site, Bob!  Now, if you'd only sent us to use Good Search to benefit the B&O Railroad Museum.....
Gene

[Yampa Bob]

Thanks Gene.  Well, I keep a link to that site handy as this question comes up often.  I keep forgetting about "Good Search", force of habit I guess.  I promise to do better. 

I copied Ross's "Scale and Gauge" page to my computer, check out the entire site for great information.

[az2rail]

Here is a calculator.

http://home.cogeco.ca/~trains/rrsoft.htm

I hope that linked.

Bruce

[Yampa Bob]

Nice calculator.  I entered values based on my scenario above, came out to 118.6 mph, compared to 120 using  "feet per minute" as a rule of thumb for HO, close enough for me.

[CNE Runner]

Here is a calculator.

http://home.cogeco.ca/~trains/rrsoft.htm

I hope that linked.

Bruce

Hey Bruce,

Thanks for the heads up on that website. The scale speed calculator works greatI I will look at the other neat things the website contains when time permits.

Ray

[az2rail]

I'm glad you guys like the calculator, but I have one of my own. If the engine leaves the tracks going around a corner, I'm going to fast.

Bruce

[Yampa Bob]

I heartily agree with your concept.  I think any preoccupation with scale speed is rather academic.  I run my trains at what looks to be a "realistic" speed.  I never think "Gee, I must be going 90 mph here, I better slow down."

The only time I do a speed test is in conjunction with a pulling test, if a loco won't maintain the speed I want at 1/2 throttle, I take off some cars or add a helper.

[Atlantic Central]

My tests with the Aristo Train Engineer and the 13.8 volt power supply I use have shown than many of today's models run at a prototypical scale top speed at the NMRA suggested 12 volts.

This allows me to use the full speed range of the Train Egineer Throttle, another "free" benifit of my control system.

Eample: Proto2000 EMD E8, 13.5 volts measured, scale speed clocked - 90 mph. Actual top speed of prototype EMD E8 with standard passenger gearing - 88 mph.

Sheldon

[Pc6275]

I measured out a scale mile on my ho scale layout how would I calculate the speed?

[jward]

As was stated before measure the time over a given section. On a previous layout I used a 6 foot section (two lengths of flex track is 1/10 of a scale mile) and multiplied the time by 10. If the resulting time is 60, 60 scale mph.

Here is the chart I used for reference.

240 sec     15 smph
180 sec     20 smph
120 sec     30 smph
 90 sec     45 smph
 60 sec     60 smph
 45 sec     90 smph
 30 sec    120 smph
 20 sec    180 smph
 15 sec    240 smph