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3,354 Posts
Hi all,
Just as any other slingshot enthusiast I was always interested in the intricacies of how, actually, slingshot physics works, regardless of the fact that I rely much on experience and feeling.
So, couple of years ago I started to read and learn about basic physics and in this regard ballistics and I also started to learn a basic programming language. My goal was to make a program that would be handy to me and possibly to the others when making slingshot related decisions.
And here it is, the program is finished and all I need is a handy name for it and I decided to consult members of this Forum for this. In the meantime, I am in the process of finding people who will make a web page for me and other related issues.
For the moment this is a PC version, and Mac one is on the way.
I tested the program and it has decent reliability: it predicts exit velocity in the range of -0.5 to -1.8 m/s, that is, for smaller ammo it shows 1.8 m/s higher prediction, and for larger ammo it shows 0.5 m/s higher prediction, and I consider this to be decent. (Some parameters such as resistance of the bands over forks, pouch air resistance etc. have not been taken into account because for vast majority of shooters these values are unknown so that higher prediction is expected.)
For a horizontal shot from 1.5 meters of height it shows +-1m, which I also consider acceptable.
However, the true value of this program, in my opinion is not in how well it "competes with reality" but in its ability to show differences among a range of values of any of the relevant parameters, therefore making relevant comparisons between setups.
I intend to charge some amount for this program. I am a retired person and I can live comfortably on my pension, however, I do not have funds to invest in a professionally done version, which is my ultimate goal (one quotation that I got here where I live is 2 people 2 months each = some 8000 dollars.)
In order to take part in this giveaway you just need to read the basic description of the program in the text that follows and answer couple of questions at the end of this thread.
The giveaway is open for 5 days and ends on January 11, 2020 at 21:00 Bosnia-Herzegovina time (GMT+1).
I retain the right to select 5 winners, or, five names I find most appealing, no matter that only one can be given to this program and each of these members will get a free copy of the program - even if for any reason I do not put it on the web.
Also, even if none of the suggested names is given to this program, still these five members will be considered winners and will get what I promised.
Try to keep one suggestion per member. If more than one, I will take only the first one into account.
My obligations towards the member whose name is selected fot the program end with the delivery of the free copy of the program.
About the program:
Firstly, this is an educational tool where the user will better understand the inner workings of slingshot physics.
Secondly, it will enable the user to bring more informed setup decisions.
Thirdly, it can assist the shooter when target shooting.
This is how its Main Screen looks:
![Shema glavnog ekrana.jpg]()
The Main Screen allows you to manipulate any of the relevant parameters in real time and get Exit Velocity and Exit Energy immediately. The lines with arrows show basic relationships among parameters.
Most of these parameters are what might be considered "Internal Ballistics", but some are relevant for "External Ballistics", that is, for the flight of the ammo through the air.
The Parameters are: Drag Coefficient, Ammo type (Ball, Cylinder, Cube), Dimensions (Diameter of the ball and of the base of the Cylinder,, Height of the Cylinder, base of the Cube), Specific Weight of the material, Volume, Reference Area, Energy per Reference Area, Forks Height, Target Height, target Size, target Distance, Draw Power, Rubber Weight, Pouch Weight, Ammo Weight, Total Weight, Draw Length, Stretch ratio, Active Band/Tube length, Elongation, Exit Velocity, Exit Energy, Air Temperature, Air Pressure, Humidity, Air Density, Gravity, Shooting Angle.
The program opens with a Default File which brings Default Parameters with it. However, you can tweak your parameters any way you want and save this as your file. Of course, you can have any number of your files on the disk tailored for various types of setups (hunting, target shooting etc.) and open them whenever you want.
Besides real time tweaking of the parameters there are three more advanced functions:
D - or Dump; when you make a change in your parameters that you like you can click on D - button and write down all the parameters from the Main Screen for further reference, and you can do this 24 times and then copy or save these parameters as a file which can be imported in a spreadsheet. (All files produced in this program can be saved as .txt files and imported or directly copied into a spreadsheet.) With strategically changing main parameters you can expect a lot from this function.
1D - this function allows you to produce a one-dimensional table with more structured approach to the problem, for example, I asked the program to start with 3g Ammo and finish with 12g for a given setup. I then imported the data of Ammo Weight, Exit Velocity and Exit Energy into a spreadsheet. Then, because the scales of velocities and energies are quite different I took highest value for velocity and highest value for energy and made them 100%, and recalculated other values to be some percentage of these highest values. And I got the following:
![table.jpg]()
![graph.jpg]()
2D - basically the same as 1D but two independent parameters can be changed at a time, however, this function is still in development.
Clicking on the Shoot! button the program calculates the Range (how far the ammo flies), Height, Velocity and Energy and makes a table of these results (to the left of the window):
![flight window.jpg]()
But it also writes down all relevant parameters for this shot and each new shot is written down as a new column (table in the middle of the window). It also draws the graph of Range, Height, velocity and Energy of the flight (right).
The program allows you to change Draw Power but also to set width of the bands and the weight of the active part of the rubber for that power so that when you manipulate draw power you also change the width of your bands and weight of the bands/rubber (for tubes this works in 100% increments).
You can manipulate Draw Length and Stretch ratio and automatically get Active Band length and Elongation. This also changes the weight of the rubber in real time.
There is a possibility that the user imports their own Stretch ratio function, that is, a .txt file which sets Draw Power for each Stretch Ratio so that when the user manipulates stretch ratio he/she also manipulates Draw Power automatically.
Target window helps the user to get the feeling of how high above the target center he/she needs to aim in order to have a clean hit, where Forks Height, Target Height, target Size and Target Distance are taken into account. It allows him/her also to get the feeling of basic trajectory shape for various target situations:
![Target window.jpg]()
The program originally works in Système international (d'unités), or „SI" units for short, with automatic conversion in United States customary units, or „US" for short.
Oh, almost to forget: there is also a "Hand Slap" window which tells you the energy that is left in the system after the Pouch stops accelerating the Ammo, actually, it does not tell you if you are going to get a Hand Slap or not because it does not calculate the energy loss while the bands and the pouch travel past the forks and go back, but still you have an indication..
Now, if you are willing to help me with the name of this program please do the following:
DO NOT use QUOTE function of this thread, but only copy the following numbered lines and write anything you want!!
1. Suggested name:
2. Rationale for the name, if any:
3. Do you think that 10$ would be appropriate for this program, yes, no, any suggestions:
4. Is Mac version of this program important for you:
5. How do you like the concept of this program, any other suggestions:
Thank you all in advance!
cheers,
jazz
Just as any other slingshot enthusiast I was always interested in the intricacies of how, actually, slingshot physics works, regardless of the fact that I rely much on experience and feeling.
So, couple of years ago I started to read and learn about basic physics and in this regard ballistics and I also started to learn a basic programming language. My goal was to make a program that would be handy to me and possibly to the others when making slingshot related decisions.
And here it is, the program is finished and all I need is a handy name for it and I decided to consult members of this Forum for this. In the meantime, I am in the process of finding people who will make a web page for me and other related issues.
For the moment this is a PC version, and Mac one is on the way.
I tested the program and it has decent reliability: it predicts exit velocity in the range of -0.5 to -1.8 m/s, that is, for smaller ammo it shows 1.8 m/s higher prediction, and for larger ammo it shows 0.5 m/s higher prediction, and I consider this to be decent. (Some parameters such as resistance of the bands over forks, pouch air resistance etc. have not been taken into account because for vast majority of shooters these values are unknown so that higher prediction is expected.)
For a horizontal shot from 1.5 meters of height it shows +-1m, which I also consider acceptable.
However, the true value of this program, in my opinion is not in how well it "competes with reality" but in its ability to show differences among a range of values of any of the relevant parameters, therefore making relevant comparisons between setups.
I intend to charge some amount for this program. I am a retired person and I can live comfortably on my pension, however, I do not have funds to invest in a professionally done version, which is my ultimate goal (one quotation that I got here where I live is 2 people 2 months each = some 8000 dollars.)
In order to take part in this giveaway you just need to read the basic description of the program in the text that follows and answer couple of questions at the end of this thread.
The giveaway is open for 5 days and ends on January 11, 2020 at 21:00 Bosnia-Herzegovina time (GMT+1).
I retain the right to select 5 winners, or, five names I find most appealing, no matter that only one can be given to this program and each of these members will get a free copy of the program - even if for any reason I do not put it on the web.
Also, even if none of the suggested names is given to this program, still these five members will be considered winners and will get what I promised.
Try to keep one suggestion per member. If more than one, I will take only the first one into account.
My obligations towards the member whose name is selected fot the program end with the delivery of the free copy of the program.
About the program:
Firstly, this is an educational tool where the user will better understand the inner workings of slingshot physics.
Secondly, it will enable the user to bring more informed setup decisions.
Thirdly, it can assist the shooter when target shooting.
This is how its Main Screen looks:
The Main Screen allows you to manipulate any of the relevant parameters in real time and get Exit Velocity and Exit Energy immediately. The lines with arrows show basic relationships among parameters.
Most of these parameters are what might be considered "Internal Ballistics", but some are relevant for "External Ballistics", that is, for the flight of the ammo through the air.
The Parameters are: Drag Coefficient, Ammo type (Ball, Cylinder, Cube), Dimensions (Diameter of the ball and of the base of the Cylinder,, Height of the Cylinder, base of the Cube), Specific Weight of the material, Volume, Reference Area, Energy per Reference Area, Forks Height, Target Height, target Size, target Distance, Draw Power, Rubber Weight, Pouch Weight, Ammo Weight, Total Weight, Draw Length, Stretch ratio, Active Band/Tube length, Elongation, Exit Velocity, Exit Energy, Air Temperature, Air Pressure, Humidity, Air Density, Gravity, Shooting Angle.
The program opens with a Default File which brings Default Parameters with it. However, you can tweak your parameters any way you want and save this as your file. Of course, you can have any number of your files on the disk tailored for various types of setups (hunting, target shooting etc.) and open them whenever you want.
Besides real time tweaking of the parameters there are three more advanced functions:
D - or Dump; when you make a change in your parameters that you like you can click on D - button and write down all the parameters from the Main Screen for further reference, and you can do this 24 times and then copy or save these parameters as a file which can be imported in a spreadsheet. (All files produced in this program can be saved as .txt files and imported or directly copied into a spreadsheet.) With strategically changing main parameters you can expect a lot from this function.
1D - this function allows you to produce a one-dimensional table with more structured approach to the problem, for example, I asked the program to start with 3g Ammo and finish with 12g for a given setup. I then imported the data of Ammo Weight, Exit Velocity and Exit Energy into a spreadsheet. Then, because the scales of velocities and energies are quite different I took highest value for velocity and highest value for energy and made them 100%, and recalculated other values to be some percentage of these highest values. And I got the following:
2D - basically the same as 1D but two independent parameters can be changed at a time, however, this function is still in development.
Clicking on the Shoot! button the program calculates the Range (how far the ammo flies), Height, Velocity and Energy and makes a table of these results (to the left of the window):
But it also writes down all relevant parameters for this shot and each new shot is written down as a new column (table in the middle of the window). It also draws the graph of Range, Height, velocity and Energy of the flight (right).
The program allows you to change Draw Power but also to set width of the bands and the weight of the active part of the rubber for that power so that when you manipulate draw power you also change the width of your bands and weight of the bands/rubber (for tubes this works in 100% increments).
You can manipulate Draw Length and Stretch ratio and automatically get Active Band length and Elongation. This also changes the weight of the rubber in real time.
There is a possibility that the user imports their own Stretch ratio function, that is, a .txt file which sets Draw Power for each Stretch Ratio so that when the user manipulates stretch ratio he/she also manipulates Draw Power automatically.
Target window helps the user to get the feeling of how high above the target center he/she needs to aim in order to have a clean hit, where Forks Height, Target Height, target Size and Target Distance are taken into account. It allows him/her also to get the feeling of basic trajectory shape for various target situations:
The program originally works in Système international (d'unités), or „SI" units for short, with automatic conversion in United States customary units, or „US" for short.
Oh, almost to forget: there is also a "Hand Slap" window which tells you the energy that is left in the system after the Pouch stops accelerating the Ammo, actually, it does not tell you if you are going to get a Hand Slap or not because it does not calculate the energy loss while the bands and the pouch travel past the forks and go back, but still you have an indication..
Now, if you are willing to help me with the name of this program please do the following:
DO NOT use QUOTE function of this thread, but only copy the following numbered lines and write anything you want!!
1. Suggested name:
2. Rationale for the name, if any:
3. Do you think that 10$ would be appropriate for this program, yes, no, any suggestions:
4. Is Mac version of this program important for you:
5. How do you like the concept of this program, any other suggestions:
Thank you all in advance!
cheers,
jazz
