A question for Jim Banner

[engineerkyle]

Hi Jim,

Didn't you have a quick and dirty method for judging scale speeds?

Something along the lines of;

COUNT HOW MANY SECONDS IT TAKES AN HO TRAIN TO TRAVEL 10 INCHES, AND THAT NUMBER EQUALS IT'S SCALE MILES PER HOUR.

Or something,

Please refresh my memory.

[Mark Damien]

I don't know , but I'll give it a shot.

The working out part.
1 mile = 5 280 feet
5280x 12 inches = 63,360inches
63,360/87ho scale = 728 inches/hour
728/60 minutes = 12inches/minute


12/60 seconds = 0.2inches/second @ 1mph.

The bit you need to know
0.2x45mph = 9inches/second

0.2x70mph = 14 inches/second

[Matthew (OV)]

Not quite that complicated if it's only distance you're scaling.

5280 / 87 = 60.6 feet per scale mile.

Divide by 10 to make it manageable.... 6.06 (round to 6, unless you're good enough with a stopwatch to click the difference between 6' and 6'.72"; I'm not!)

Measure a section of track six feet long.

Using a stopwatch of some kind, time how long the train takes to go 6 feet.

Multiply by 10.  This is how many seconds the train takes to travel one (scale) mile.

Divide 3600 by the number you got.  (3600/(seconds to travel 1 scale mile))

Your result is in scale miles per hour. 

Example:  Your train takes 12 seconds to travel 6 feet.
12 * 10 = 120.
3600/120 = 30 scale miles per hour.

Now ... there are those astrophysicists among us (and some Metaphysicists as well) who will discuss the scaling of time as well as distance.... leading to fast clocking, and readings in scale miles per scale hour .... which WILL make your head spin.  For me, just scaling  the distance makes things work very well, and realistically!

Matthew (OV)

Oh, and I know I'm not Jim, btw ... but since he's not been in yet....

[Seasaltchap]

From: Matthew:

Example:  Your train takes 12 seconds to travel 6 feet.
12 * 10 = 120.
3600/120 = 30 scale miles per hour.


or another way -

60 mph = 88 feet/sec.   (A Popular Given)

(88 x 12)/83       (1/83 the scale)

12.72 inches/sec

I think at 30mph(scale speed) the loco should only cover 6 inches a second, when it would cover 12.72 ins/sec at 60mph(scale)

QEF.

[Seasaltchap]

Correction 1/87 Scale. - very small correction - still rounded to the same figures.

I think it was the method that was important.

[Jim Banner]

Using the exact scale for H0, namely 3.5 millimetres per foot, 60 miles per hour works out to 12.126 inches per second.  But 12" per second is close enough.  I like to look at this as two 40 foot box cars per second, and if two go by every time I count one thousand and one, one thousand and two, etc., then that is close enough to 60 miles per hour for me.  If only one goes by per second, then it is 30 mph, a good speed for a drag freight.  A yard speed limit might be 10 mph.  Since this is 1/3 of 30 mph, it must take three times as long for a car to go by.  So that is one 40 foot car every 3 seconds.  Coupling speed in real life is around 3 mph, or 1/10 of 30 mph.  So the train should be moving only one box car length every 10 seconds.  (in scale, it is hard to couple at this speed, even with Kadees, if picking up a single car.)

Incidentally, using box car lengths makes this speed check independent of scale.  And if the cars are 50 foot, you will still get closer that just guessing.  Next time you get caught at a level crossing, you can pass the time figuring the speed of the passing train.   

[Bill Baker]

Jim, what you said makes sense to me.  All of that math above was giving me a head ache.  I'm just glad no one asked about the "string theory".  No telling where that conversation would go.

[Seasaltchap]

Bill,

I don't think my 3 line eloquent response should receive a smack-down.

Surely you can be more eloquent too.

Regards

[Bill Baker]

Stewart,

I apologize my friend....absolutely no smack-down was intended.  I have always been anemic in math and was suffering through the ratios several of you were mentioning above.  I have a close friend who is a mathematics professor at the University here and he was discussing the string theory with me and a couple of other friends the other night and I must admit my eyes started glazing over and mind became numb.  This was what I had in mind when I mentioned it in my previous post.

Still friends?

[engineerkyle]

Using your formula, I'd say this one was going about 20 mph.

http://video.google.com/videoplay?docid=8358545292025148502

[Seasaltchap]

Bill: Understood. I obviously got the wrong end of the stick.

[Jim Banner]

Kyle, I agree, somewhere around 15 or 20 mph.  And looking good doing it.  Our tastes in music are a little different, but not our taste in trains.