Here’s something I’ve been thinking about for awhile. How do you measure scale mph in HO, and what is the simplest way to measure it? For example, there is a staff review of an Atlas ALCO RS-3, and in it they said the locomotive reached 78 scale mph at 12 volts. I’m just curious as to how this works.
Boulder Creek Engineering has a speedometer you can buy. I don’t have one but I do have their working scale and it’s very reliable and well made. A nice video and description is on their site.
https://bouldercreekengineering.com/
I’m sure there may be other speedometers on the market too.
oldline1
Try this:
http://www.stonysmith.com/railroad/speedcalc.asp
I use an Accutrack IR readout but it is more of a fun accessory than a necessary tool.
http://cs.trains.com/mrr/f/744/p/260149/2923972.aspx
Good Luck, Ed
My eye. I think I’m a pretty good judge as to the speed of my train. While watching the real thing, and listening to the box detector, I was surprised that the train was actually doing 46 mph. As it went by, it seemed like it was much faster.
I place myself “trackside” on my lay out, and watch how it passes track side structures.
I have discovered that with the DT400 I use, the speed step number on the screen seems to be real close.
I’ve watched enough Amtrak, and when I run passenger trains, I use the same judgement.
But I don’t to get any closer than that. I’ve never encountered a problem where I needed to know, or needed to measure the exact speed.
Maybe for some that’s important, knowing the exact speed.
Mike.
I have 121’ of HO mainline which equals 10539’ or just a few feet less than 2 scale miles. I time a full trip (average with 3½% grade) 2 minutes = 59.9 MPH.
From the NMRA site:
Mel
My Model Railroad
http://melvineperry.blogspot.com/
Bakersfield, California
I’m beginning to realize
Excellent Mel, I didn’t know. Now have to find a stop watch and play around with it. Maybe just to check out my throttle readings.
And NO, I don’t have a smart phone or a computor hooked up the my lay out.
Mike.
Mike
I have some parts on order to attempt a wireless speedometer from a towed car similar to the Boulder Creek Speedometer using a pair of Arduino Nanos.
I received the magnets yesterday but the Hall Effect sensors didn’t clear China Customs until the 4th so it will be a while. I have everything else for the project.
Mel
My Model Railroad
http://melvineperry.blogspot.com/
Thank you all. You’ve given me some interesting food for thought. I have no urgent need for this, but like I said, I was just curious. But, you never know what you might need and when.
did both the stationary, and the mobile versions a few years ago , worked well …based on arduino’s …
if you want an inexpensive way to measure speed, just a stopwatch and two spaced markers will do it …
i use 28 speed steps, and geared steam engines, one smph per speed step …pretty easy to set up, in jmri or just cv’s
Here is a nice, easy. low-tech solution.
HO scale is 1:87.1somethingsomething.
60 MPH is 88 feet per second.
So, for HO scale, you can say that 1 foot per second is 60 MPH HO scale, close enough.
1 inch per second is close enough to 5 mph, 2 inches per second is 10 mph, etc.
All you need is some colored pins an inch apart and the timer on a cell phone.
I just push two buttons on my NCC controller and get an audible report.[swg]
Having a somewhat inquisitive mind I decided to test the accuracy by timing trains around a 20’ x 6’ loop that I can isolate from the rest of the layout. The audible report was dead on as far as I could determine.
I just wish the audible report was a sexy babe voice instead of Bob from accounting.[(-D]
The early QSI decoders would tell you via voice what the scale mph was at the time by pressing one of the function buttons, F10 or F9…I forget.
I have run enough trains, and have essentially correctly spaced telegraph poles, such that I can get pretty darned close watching the trains move past items how fast they are going. Also, with steamers, I can make a rough estimate of their speed by recalling their driver diameters and counting the cyclic rate of the crosshead or the turn of the main crank per second.
Also, for steamers, their maximum horsepower at the rails would be produced, across driver diameters, at about 4 cycles of the piston/main crank per second, a bit less truthfully. So, if I need my head-end producing maximum horsepower for a given consist and speed, and terrain, I make sure it’s not in ‘drag’ configuration, as a Y6b would be on the Blue Ridge, but churning quite nicely at ‘express’ speed.
There’s a one-page article in the September, 2003 issue of RMC, entitled: “Scale miles-per-hour at a glance”.
S.M.P.H. = .6818 X SCALE FACTOR X DISTANCE (in decimal feet) ÷ time
The scale factors are:
O = 48
S = 64
HO = 87.1
TT = 120
N = 160
Z = 220
The author simplified the formula somewhat, but used a stopwatch and a calculator for timing.
I’m not so fussy, and decided to simplify the formula even more, creating a chart of speeds in increments of 5mph, up to 40mph (the highest allowable speed on my layout) with a rounded-off elapsed time using the second hand on a watch.
While I’ve not formally created “speed traps”, the plan is to use measured lengths of straight, level track, each with signs indicating the “Start” and “End” points.
In HO scale, for example, the speed trap might be only 5’ long in one area, and 10’ or 15’ in others. Each would have a chart of times and corresponding speeds affixed to the layout’s fascia.
For my HO scale layout, travelling through the 5’ “trap” in 59 seconds yields a scale speed of 5 mph, in 30 seconds it’s 10 smph, 10 seconds 30 smph, and the hogger’s hitting the limit when he gets his loco through in 7 seconds.
The main purpose is to allow operators, including myself, to have a sense of what speed is appropriate, especially since most of the mainline does have signed speed limits.
On the many grades, most trains will have difficulty reaching allowable speeds on uphill trips, and likely the opposite situation when descending those grades, dependent, of course, on the tonnage trailing.
Wayne
I’m sure they have a CV for that. Check the manual. [swg]
Mike.
I created a printable, at-a-glance table in Excel similar to what Wayne posted and have that up on the wall: (Click table to enlarge)
All I need is the table, a watch or stopwatch, and two fixed points.
To capture a range from 0 to 60 sMPH, I broke down the measuring distances into three main categories: 3’, 1’, and 3". I use the 3’ distance for clocking fast moving trains and the 1’ & 3" distance for slower moving units. It’s inexpensive, doesn’t require electricity, and I can measure it anywhere on the layout. No special device needed. All I’m looking for is a ballpark idea.
Tom
Divide scale miles traveled by hours.
Find a large part of your layout, maybe even a couple of laps around the main line. Measure it with a ruler, and convert real feet into scale miles. For HO, multiple real feet by 87 to get HO scale feet. Divide scale feet by 5280 to obtain scale miles. The answer will likely be a decimal fraction of a scale mile or two.
Use a stop watch to measure how long it takes the train to cover the scale mile[s]. Convert from seconds to hours by dividing measured seconds by 3600 (number of seconds in one hour)
Divide the measured scale mile[s] by measured time in hours to obtain scale miles per hour.
A hand calculator makes it a lot easier.
All of these different formulars and charts ! [:O] and methods! They all have fixed points, and a stop watch involved
I’m not the OP, but I’ll stick with the simple formula from the NMRA that Mel posted.
Mike.
EDIT: That is of course, if I was totally out of mind as to how fast my train was running. Hasn’t happened yet. [swg]
I did all the math one time: In HO the number of inches travelled in 5 seconds equals speed in miles per hour.
Dave
A question for those who use their DCC throttle to indicate scale speed. Does setting your DCC system to run a fast clock affect the speed reading?