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Discussion Starter · #1 ·
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
 

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First of I have to say that this is amazing and even if I don't win I think I would buy it.

1.Suggested name:
SBC (Sling & Band Caucalator)
CBC (Catapult & Band Calculator)

2. Rationale for the name, if any:

3. Do you think that 10$ would be appropriate for this program, yes, no, any suggestions:
I think that's a good generous price, specially for beginners that are very curious about everything sling related I bet even asking for $15 is good

4. Is Mac version of this program important for you:
I am not a Mac person but I would say yes since not everyone has a PC and prefer Mac

5. How do you like the concept of this program, any other suggestions:
Really interesting and might help people find what they are looking for without having to buy different bands and such and might get more people interested in slinging if I knew programming I would of loved to help with the he development of this program but sadly I don't :(

Sent from my SM-G960U using Tapatalk
 

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Excellent work!

I had the idea to calculate the speed based on different taper shape or tube size. One major reference is some known setups. But i never had time to investigate how to implement it.

It seems you have spent a lot of time to study the algorithm!
 

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1. Suggested name:

Slingshot Ballistics Calculator

2. Rationale for the name, if any:

It describes the programs and has the right tone.

3. Do you think that 10$ would be appropriate for this program, yes, no, any suggestions:

More than fair - although you might consider selling the program outright to some of the slingshot manufacturers and custom designers like Saunder, Simple Shot, Pocket Predator, Gamekeeper John. YSYEO, Dan Hood, Mark Seljan, and everyone else that I forgot to mention.

4. Is Mac version of this program important for you:

Yes - I am a Mac person

5. How do you like the concept of this program, any other suggestions:

Great concept. There are programs for archers to determine what type of arrow spine for a particular set-up. Could this be used to recommend ammo for a particular set up, or bands for particular ammo. Ultimately, I am going to ask my best friend, w professional engineer, to explain all of this to me. I did not do well in the sciences!

Can you copyright this?
 

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Discussion Starter · #5 ·
Hi JASling, JPD-Madrid and Blue Raja,

Thank you for your suggestions and ideas!

cheers,

jazz
 

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Discussion Starter · #6 ·
Hi all,

It is January 11 21:00, the deadline for this giveaway.

I got suggestions for the name for my software from:

JASling - SBC (Sling & Band Caucalator) or CBC (Catapult & Band Calculator) and

Blue Raja - Slingshot Ballistics Calculator

and I got an encouragement from JPD - Madrid.

The number of entries is less then I expected but enough for me. The suggestions are in line with what I myself was thinking and now I will give these and some other names to the company that will make web page for me, domain, hosting etc. and they will check if these names are free or not.

As for this giveaway, all entries are appealing (in the sense of my announcement) and I will give them a free copy of my program (JASling and Blue Raja). This applies also to JPD - Madrid who did not give me a suggestion but gave me an encouragement, which I really need after three years of work that I invested into this.

I will PM them about the instructions of how they are going to download the program as soon as my site is on, and if that does not happen for any reason they will get their copies via some file transfer site.

Thank you very much again for taking part in this giveaway and thanks to all those who read this very long thread!

cheers,

jazz
 
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