How fast am I going?

Model Railroader General Discussion (Model Railroader)
1

Morning,

Just a question, as I am trying to learn to manage mainline speeds (45mph) and yard speeds (20mph).

In HO scale (1:87), if my engine travels 1 (actual) foot in 10 (actual) seconds, how fast am I traveling?

And can can you provide me the formula used or point me to a learning place?

Thanks

cplmckenzie

2

1 scale mile is approximately 60 feet in HO. If you travel 1 foot in 10 seconds you are traveling about 1/60th of a mile. There are 3600 seconds in 1 hour. Divide that by 10 seconds you get 360. Multiple that times 1/60th and you get 360/60ths which equals 6. You are going about 6mph. Since I started with an approximate figure, the final answer is an approximation as well but close enough for government work.

3

For a rough estimate, do the following. 60 mph is 88’/sec. In HO, that is about 1 real foot(87 scale feet) but close). So, 10 seconds to travel 1 real foot should work out to 10 scale miles per hour. Myself, I would use something like a 6 foot timing section. That works out to 60 seconds to travel 6 real feet - still 6 scale mph. Jim

4

Wow,

It seems like I am trying to go way to fast. As the longest stretch of straight mainline is roughly 4’, much much shorter in the yard.

btw.

anyone know the mainline and yard speed limits?

Thanks again

cplmckenzie

5

cplmckenzie,

If you are wanting a more precise measurement of your sMPH, the following is what I posted recently in another thread. For conveniece, I created a quick-glance chart - for both switching speeds and mainline speeds - in Excel, printed it out, and hung it on the wall…

FYI: Calculating scale MPH (sMPH) isn’t that complicated. All you need is:

  1. A predetermined length of track - 3" is quite sufficient for slow speed
  2. A timing device
  3. Your DCC locomotive
  4. Your DCC system set at speed step 001.

Time how long it takes your locomotive to travel from Point A to Point B and calculate the following:

  • Distance(ft)/Time(sec) = Rate (ft/sec)
  • Convert Rate to mi/hr and multiply by scale
  • End result: Rate in sMPH

Example: It takes 15 secs for my locomotive to travel 3" (or 0.25’)

  • 0.25’/15 secs = 0.02 ft/sec
  • Convert ft/sec to mi/hr and multiply by scale (or, 0.02 divided by 5,280’ x 3,600 sec x 87.1)
  • End result: 0.99 sMPH

Tom

6

Jim, I think you made a typo when you wrote ten 10 miles per hour. You had the correct answer in your last sentence.

7

For anyone nerdy enough to want a more precise figure than 6mph, the actual number is 5.9386363… mph. That’s using 87.1 as the scale for HO.

8

In calculating speed, it’s correct that you need to find a straight section of track vs, one curved? Also, I thought most moden trains go 40-55mph on the mainline (of course not accounting for weather, etc.).

9

Keep the below link in your smarphone or tablet.

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

Rich

10

I did calculations a while back and then went to a simpler system:

For HO inches travelled in 5 seconds equals smph. Your example gives the same result.

Dave

11

6 mph (5 * 12 inch / 10 second)

1 mph in HO is ~0.2 inch/sec (5280/87/3600)

1 inch/sec is 5 smph (scale mph)

5 is the magic number

    mph  5  10  15  20  25  30  35  40  45  50  55  60
 in/sec  1   2   3   4   5   6   7   8   9  10  11  12
12

Some decoders will give you your scale speed if you press F10. That is if you are running DCC.

13

I need to give this chart to my son. I don’t think he has ever slowed down enough to run 11 feet/second! Thanks for the table, very helpful.

14

Google “scale speed calculator” and bring up western reserve. You can plug in any variables and get the scale speed

15

I learned this from an old Staten Island Rapid Transit employee timetable. A 40’ car will pass a fixed point in 1 second when traveling at 28 mph. 2 seconds at 14 miles an hour, 4 seconds at 7 mph. A 50’ car passes a fixed point in 1 second at 35 mph. Since you most likely have 40 or 50 foot cars, and lots of fixed points, you should be good to go.