Calculating the scale speed of OO gauge models

[Dungrange]

7 minutes ago, Nearholmer said:

Is it that our brains are capable of monitoring the near-imperceptible vertical, rather than horizontal, movements, and spotting that the rates of acceleration within them don't match gravity?

 

Probably.  I guess there is also the issue of things like air resistance.  In a vacuum, two items will fall at the same rate.  The problem is that we don't live in a vacuum, so although a hammer and a feather were observed to fall at the same rate on the moon, we don't see that in every day life on Earth.  You can therefore undertake a calculation as to how much you want to slow your film down by to correct for something like gravity, but any adjustment is never going to be wholly accurate for all properties.

 

@meil and I may disagree on the relevance of gravity to the calculation of a 'scale speed' for a model train on a horizontal track, but he is definitely correct when he says: 

 

On 20/04/2021 at 15:05, meil said:

the dynamics would be all to cock.

 

There are loads of things that don't scale correctly: inertia, momentum, drag, engineering tolerances, etc.  Therefore, I don't think it would ever be possible to film a model and not have something that makes it appear not quite like the prototype.

 

However, I don't think that changes the fact that you can calculate a scale speed in the horizontal plane along the line of our track and run our trains at that scale speed.

 

27 minutes ago, Nearholmer said:

I've been watching with fascination as the simple answer to a simple question has expanded into complex answers to complex questions - all very interesting.

 

That is the joys of RMWeb!!

 

 

[Dungrange]

4 minutes ago, Hroth said:

Its the snide "the calculation is a simple one" that amuses me.

 

I agree.  To be a simple calculation, surely there would need to be an integer number of telegraph poles in a mile: not 29.33 telegraph poles per mile. 

[Reorte]

25 minutes ago, Hroth said:

 

Its the snide "the calculation is a simple one" that amuses me.

 

Some aspects help - one yard a second is very close to 2 mph, so a telegraph pole every 2 seconds would be 60 mph. So it's then down to how good you are at doing a single division mentally - the sort of thing that might be simple for Holmes but isn't for the likes of me who's been using calculators and computers for those sorts of numbers for a long time!

Edited April 21, 2021 by Reorte

[Nearholmer]

The trad method was to count wheel-beats on jointed 60ft rail lengths over a minute. IIRC, 88 equates to 60mph, and I’ve certainly forgotten the rest, although 45mph (66bpm), 30mph (44bpm) etc are easy by proportion.

 

 

Edited April 21, 2021 by Nearholmer

[TheSignalEngineer]

1 hour ago, Reorte said:

Some aspects help - one yard a second is very close to 2 mph, so a telegraph pole every 2 seconds would be 60 mph. So it's then down to how good you are at doing a single division mentally - the sort of thing that might be simple for Holmes but isn't for the likes of me who's been using calculators and computers for those sorts of numbers for a long time!

And of course pole spacings weren't all the same. They could vary due to such factors as the weight of the route, positions of bridges, stations etc. Quarter mileposts are easy. 10 seconds = 90 mph.

14 minutes ago, Nearholmer said:

The trad method was to count wheel-beats on jointed 60ft rail lengths over a minute. IIRC, 88 equates to 60mph, and I’ve certainly forgotten the rest, although 45mph (66bpm), 30mph (44bpm) etc are easy by proportion.

 

 

Even easier, if you count the beats in 41 seconds that is the speed in mph on 60' jointed track to 99.78% accuracy.

[Nearholmer]

The obvious answer to the OP’s query then, is to saw all the track on his layout into scale 60ft lengths, buy a watch with a sweep hand, and count wheel beats.

 

Easy really.

[AndrueC]

2 hours ago, Reorte said:

Some aspects help - one yard a second is very close to 2 mph, so a telegraph pole every 2 seconds would be 60 mph. So it's then down to how good you are at doing a single division mentally - the sort of thing that might be simple for Holmes but isn't for the likes of me who's been using calculators and computers for those sorts of numbers for a long time!

Conversely 1 metre per second is 3,600 metres per hour or 3.6 kmh. The answer is in the question: 1 m/s = 3,600m/h = 3.6kmh. It's not even wrong to say that 1 metre per second is 3,600 metres per hour. It is. It's only convention that suggests replacing 'one thousand' with 'k' is better.

 

New York is approx 6,000km from London. It's also approx 6Mm from London. Or 6,000,000m from London. Whatever floats yer boat.

 

If we know that telegraph poles are 55 metres apart then:

 

55/2*3600 = 99kmh. Jobs a good 'un. Doesn't require much mathematical ability.

 

But if you insist:

 

99/1.6 = 61.875 mph 

 

Familiarity counts for a lot but when you look at it from the perspective of global trade and mathematics metric seems to be the better answer. It would of course be better if we could all do arithmetic in our heads and were good at fractions but that's not how modern education leaves us. The metric system makes most things simpler and for sure having one globally agreed set of measurements has to be best.

 

It saves a tonne of bother and avoids a litre of tears

Edited April 21, 2021 by AndrueC

[Reorte]

1 hour ago, AndrueC said:

Familiarity counts for a lot but when you look at it from the perspective of global trade and mathematics metric seems to be the better answer. It would of course be better if we could all do arithmetic in our heads and were good at fractions but that's not how modern education leaves us. The metric system makes most things simpler and for sure having one globally agreed set of measurements has to be best.

 

It saves a tonne of bother and avoids a litre of tears

Oh gawd, not the metric debate again, which wasn't anything to do with the Sherlock Holmes example (yeah, it would if they were convenient fractions of a kilometer, but the same's true if they were convenient fractions of a mile, like the quarter mile posts are, no difference really).

 

As for "simpler", it would be if we all had the same everything and all individuality was destroyed, but once things do the job well enough I'm satisfied and generally find "improvement" just make the world a less interesting place for what are really generally quite trivial gains masquerading as "so much more convenient" (a phrase I've come to loathe).

Edited April 21, 2021 by Reorte

[Il Grifone]

20 hours ago, Nearholmer said:

The trad method was to count wheel-beats on jointed 60ft rail lengths over a minute. IIRC, 88 equates to 60mph, and I’ve certainly forgotten the rest, although 45mph (66bpm), 30mph (44bpm) etc are easy by proportion.

 

 

 

In the time of Sherlock Holmes rails were shorter than 60ft. Sixty yards in 4mm scale would be just under 2' 6". I suspect we place our telegraph poles at about a foot apart  (I do anyway - it looks about right to me, even if it isn't).