Scale speed

[Meter rat]

How do people work out the scale speed, of their models? That is if you are concerned about these things. Or any one has given it any thought.

This is a formula I found while looking for a simple method. I did not want to go down the whole time, distance thing, as I will be honest, my maths ain’t that great.

Apparently mathematicians. And engineers who build boats for use in test tanks use this formula for obtaining scale speed.

SS=RS/SQRT(S
SS=Scale speed
RS=Real speed
S=Scale

To calculate a scale speed, divide the real speed by the square root of the scale.

How accurate would this formula be? My view is if boat designers use it, must be right?

Most people on FB have decided that to get scale speed, you just divide by 1/16. So a full size tank covering 16km in one hour is travelling at 16kmh. Their logic is a 1/16 tank will travel at 1kmh as 1km is 1/16 of 16km.

I am hoping to get some serious advice on here, and not be shot down by the blawbags, like on FB.

[jarndice]

This is a question asked some time back and it's answer should be found if you trawl through the relevant pages on the forum.

[Model Builder 4]

This question comes up from time to time but I've never really given the whole scale speed thing a lot of thought to be honest. Something along the same lines though is when people say that a tank/vehicle is too fast, surely this is relative to the operators input on the controls right
The tank/vehicle will only move as fast as you move the controls/sticks, if you invest in a fancy radio or control board you can setup parameters to your liking but if you are using a standard basic setup you are pretty much stuck with what you got.
As most people who have just bought the coolbank stuart will tell you that it's very fast even for a light tank, now this may not be an ideal solution but if you are planning on keeping the original transmitter and board you could always add a gimbal stick restrictor, I've attached a picture of what I I'm going to do on my radio, by limiting the movement of the sticks you therefore restrict the top speed, you could make it to whatever size you think is the right amount of movement to get the speed that you are happy with, I've shown it in white so it stands out but you could make it any colour you choose, I will be making mine from styrene sheet but I would imagine anyone with even a basic grasp of 3d printing could knock one of these up in no time. The other pictures that I've attached show a stick shift type for vehicles and these will only work if you have the throttle on one stick and steering on the other but you can see what is possible. They do not need to be fixed permanently as you could just use double sided tape to stick them onto the gimbal so if you ever get the urge to go wild and let it rip at full speed it can be removed to do so. Just an idea for those on a budget

Cheers,Lee.

Sent from my SM-G950F using Tapatalk

[Dogberry]

This is how I work it out when I am trying to find the right gearbox ratios. I use the following logic

Find out the maximum road speed of real tank for example 40KPH
Find out the distance between each track link pin ( Easy with German WWII tracks as each had a code giving that distance) say 150mm
How many teeth on the Drive wheel say 20

At 40 KPH is (x1000) =40000Metres per hour or (divide by 3600) =11.11metres per second

So 11.11 mps (x 1000 div by 150 = 74 )the tank needs to advance at 74 track links per second or (Divide by number of teeth 20 =)3.7 revolutions of the drive spoken per second or 222.222 revs per minute.

Now if you count the number of max RPM of your model tanks drive wheel, number of teeth and you know the distance between the track pins of a real tank you can calculate the scale speed of your tank.

[Son of a gun-ner]

Well, I'm a mechanical Engineer, and my wife is an electronics engineer and mathematician.
I've just been reading up on this on the net and now my brain hurts, with "proof" of concept claims, along with reasons to debunk the obvious.
One that made me laugh out loud, was a chap from one camp that stated "The fact that something has appeared on a website does not make it in any way correct." As he makes what he considers correct information on a website This particular individual, tries to prove their point by mentioning that boat designers have been using that formula for over two hundred years, with no links to those 200 year old websites.
Which I must say, gave me a clue at to what this formulas is all about.

Well, I think I understand why there are two schools of thought on this, and it is because one has become confused (over internet time, with far too many experts not asking "WHY") with actual scale speed calculating. Scale speed calculating is just purely fractions, whatever fraction the length is of the original, that is the fraction used to calculate speed.
It's funny, the person making claims about people "not understanding concepts like squares and square roots" actually doesn't understand why they are used in this instance.
The formula you have shown and from what I can surmise, isn't for a straight forward "Scale Speed" calculation, this formula is for calculating what scale model boat would be needed (or what speed to simulate in a test tank For a given scale) to give an accurate interpretation of wind and water effects on a full sized boat, mainly a sailing boat at the desired actual speed. I haven't fully looked into it, and my Mrs is away at the moment, but I can come back to this with more. We just have to remember, because water and wind effects on a sailing boat can't be scaled down, they had to work out a calculation to account for this. Which involved a lot more to end up with this simple formula.
If this formulas was just for scale speed, a half scale 1/2 vehicle would be traveling at over eleven mph where the full sized vehicle was doing 16mph which is totally ridiculous as a scale speed of a half.

[jarndice]

This question comes up from time to time but I've never really given the whole scale speed thing a lot of thought to be honest. Something along the same lines though is when people say that a tank/vehicle is too fast, surely this is relative to the operators input on the controls right
The tank/vehicle will only move as fast as you move the controls/sticks, if you invest in a fancy radio or control board you can setup parameters to your liking but if you are using a standard basic setup you are pretty much stuck with what you got.
As most people who have just bought the coolbank stuart will tell you that it's very fast even for a light tank, now this may not be an ideal solution but if you are planning on keeping the original transmitter and board you could always add a gimbal stick restrictor, I've attached a picture of what I I'm going to do on my radio, by limiting the movement of the sticks you therefore restrict the top speed, you could make it to whatever size you think is the right amount of movement to get the speed that you are happy with, I've shown it in white so it stands out but you could make it any colour you choose, I will be making mine from styrene sheet but I would imagine anyone with even a basic grasp of 3d printing could knock one of these up in no time. The other pictures that I've attached show a stick shift type for vehicles and these will only work if you have the throttle on one stick and steering on the other but you can see what is possible. They do not need to be fixed permanently as you could just use double sided tape to stick them onto the gimbal so if you ever get the urge to go wild and let it rip at full speed it can be removed to do so. Just an idea for those on a budget

Cheers,Lee.

Sent from my SM-G950F using Tapatalk

Controlling the speed is half of the problem and your idea addresses that very well but the other half is the unrealistic accelleration and that is not going to be sorted out on the Heng Long/Taigen transmitter.

[Son of a gun-ner]

I conclude that the formula using square roots, is used for calculating the ratio between size and speed of sailing boats within the constant that is water.

The trouble I find with the internet, what is spreading to tv, the more it's used for research, it's like people copying the wrong homework with some wording it their own way not to be caught out for copying. A bit like Chinese Whispers.
Historians and fact checkers need to visit libraries, and read actual old pre internet books.

[Kaczor]

The main problem with stock models is not the radio but the gearboxes. In my Jagdtiger, after modifying the gearboxes, when using a standard Taigen radio, the model drives more or less realistically and does not accelerate like Formula 1. Coolbank Stuart have small gear ratio and that's why is so fast.

[Jimster]

I used my radio parameters to reduce top speed and turret rotation speed as well. I get my kicks from trying to drive as realistically as possible. It drives me nuts to see an RC tank take off like a formula 1 race car and then stop on a dime. But, to each their own.

[Ecam]

I'm thinking that some one soon will come up with a simple add on gear reduction for the stock motor in the Stuart. From the reviews that I have read on the Coolbank Stuart they all seem to list the speed as the number one complaint.