Speed

[eagle37]

In the thread on turnouts, someone mentioned that
many "engineers" do not run their trains at "reasonable
speed."  What is "reasonable" speed?  Are you saying
trains are usually run too slow or too fast?  I do find that
I have more trouble with turnout when I try to run at
very slow speed.
eagle37.

[Yampa Bob]

In my area I often see coal trains running 70 MPH on long level straights. The track parallels the highway so I have paced them.  But winding through the tight valley curves they only run about 35. 

For HO scale, you can omit the 1/88 constant in the formula, and just say that if your train is moving at 40 feet per minute, then the scale speed is close to 40 mph.
Let's say your total loop is 30 feet around, and it takes 10 seconds to make the round, that's 180 feet per minute, or close to 180 mph.  Is that realistic?

I have 2 tests for turnouts going through the straight section either direction. At full throttle and at a creeping speed.  At either extreme, or any speed in between, it should be no different than running on a straight track, no wobble, noise, shimmy, shake or hesitations.  The only thing I will accept is a slight "tick, tick" as the wheels go through the flangeway, no more than a normal rail joint click.

So what's a "reasonable" speed for the curved section?  I don't know, I would make a wild guess at 10 mph or less. (10 feet per minute).  Check this site for the speed formula.

http://www.spec2000.net/rr_site_pages/rr_scale_dfn.htm

For a visual reference regarding the flangeway, see Figure 2 on this page.

http://www.nmra.org/standards/sandrp/s-1_Overview.html

My most acute sense is that of "feel". For checking turnouts, I use a loose plastic truck with metal wheels, fine tuned by reaming the journals.  I place my index finger on the truck center and push it through at varied down pressure.  You can feel the slightest imperfection, especially the wheel drop at the flangeway. 

Thoroughly read this page, particularly the section on "High Speed Operation":

http://en.wikipedia.org/wiki/Railroad_switch

[WoundedBear]

Applying that formula to my last layout yields this....

Mainline run was 66 feet.

It took a Shay about 9 1/2 minutes to make the circuit.

That equals roughly 6.95 feet per minute.

1/88 X 6.95 X 87

This gives a net result of 6.87 or just under 7 mph in scale. Fairly realistic for a geared loco.

Then there is the old Like-Life 0-4-0....lol

Mainline run still 66 feet.

This thing runs lap times of about 45 seconds....lol.

66/.75 equals 88 feet per minute.

1/88 X 88 X 87 gives a result of about 87 mph.

Little quick for a switcher but she'll give a slot car a run for it's money....lmao.

Sid

[kevin2083]

I clocked my repowered AHM 0-4-0 at 145 scale MPH. That was the last time it ran, since the curves didn't support those speeds. I get to repower it again.

[Guilford Guy]

Little quick for a switcher but she'll give a slot car a run for it's money....lmao.

Oh?

Or we could use another formula...
Multiply the feel traveled by the reciprocal or the scale first. HO= (ftx87)
Then divide that by the seconds it took to traverse that length multiplied by 1.47. (s x 1.47)

(Ft x Reciprocal of Scale) ÷ (S x 1.47)

So...
HO (4ft x 87) ÷ (6 s x 1.47) = 348 ÷ 8.82 = Approximately 40 scale mph

[Yampa Bob]

Why make it so complicated?  The 1/88 is a constant and can be omitted if the scale is HO.  Notice Sid's calculation:

1/88 X 6.95 X 87 = 6.87   The scale ratio and the reciprocal constant just cancel each other out.  So there is no need for a calculation if the scale is HO.   Feet per minute = ~ mph.   The error of  .08 mph is negligible.

Considering Ross Crain's credentials, I would suggest using his formula. 

(Doesn't anyone read all my posts?) 

I checked my post in the other thread about turnouts, and my statement was: "...few modelers run at realistic speeds."