# High End Exel Bandcalculator by Tobse



## Tobse

Hi Friends,

I made this calculator.

here with speed calculation:

https://docs.google.com/file/d/0BxmVItl59G_Zd3Y2bDczSFQ0bTg/edit?pli=1

here only the Bands: (more compact)

https://docs.google.com/file/d/0BxmVItl59G_ZWjV4QVVkMVlxSDg/edit?pli=1

It work with all band colors and need only two values to show you all dimensions for your band and your ball.

If you you gif him two values more it show you also the speed you will get !!!

that's probably the first calculator also calculates the speed ?

Sorry for the German language... maybe you can translate it with google ? this works quite well.

i am not a math expert.. but it works :king:

You are better? you can simply change the Exel table and post it as well.

i think this is the best Bandcalculator so far.

hope you like it.

BTW: some one can translate the table in english for me?

here you can see how we developed it:

http://slingshots.myfreeforum.org/viewtopic.php?f=7&t=1834


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## Hrawk

Very nice Tobias.

I'll knock up a translated version a bit later today unless someone beats me to it.


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## Charles

Sounds interesting, Tobse. Thanks for posting this. I have downloaded it, but cannot read German! I did not see any place for temperature variation. What temperature did you assume?

Cheers .... Charles


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## Btoon84

Nice contribution : ) thanks dude


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## Tentacle Toast

Great work, Tobse! You're a gentleman & a scholar for sharing with us! A tip for translation if one's browsing with their phone; an app called "Tranzilla" works well via the copy/paste method, & if I'm remembering correctly, it was free...Thanks again, Tobse!


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## Henry the Hermit

Looking good, Tobse. I was going to offer a translation, but Hrawk beat me to it.

Vielen dank.


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## Tobse

Glad you made a translation, this will be better than mine 



Charles said:


> Sounds interesting, Tobse. Thanks for posting this. I have downloaded it, but cannot read German! I did not see any place for temperature variation. What temperature did you assume?
> 
> Cheers .... Charles


You can use the "Gummi Kompensation" to adjust the speed if you have a chrony, the settings are made at warm weather and butterfly shooting, you can use the values set down by 0.2 if it's winter

i have tested it with some bands i have and speed´s i know from friends, and it looks to me like the calculator made good job.

what i really like, is that it fit also with my chrony vids i made, i test it with my 13mm vid:

9gramm / 0,35mm bands / 280mm long and the calculator show me the speed have in the video with exact the same bands. So i think it work good.

also the bands i use last summer for the 100m long range shooting made the same speed like the claculator displays.


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## Crac

I'd hoped this forum might have contained a few people willing to work on this...

My system is slightly different:

Page 1 is shown; the band is cut into 1000 pieces for analysis

Page 2 is missing... basically it's a lookup table from experimental material properties (applied tensile data fitted by myself to a 5th order poly)

Page 3 is ammo selection and analysis... the analysis is slightly weighted towards momentum but if you're not going for max speed it makes no difference.

Page 4 is missing, this is an input function used to generate curvy band profiles. (I'll solve the coefficients using calculus of variations = simple beans)

The controls are all on one page: the green boxes.

You dial a draw force in.

Add a draw distance

Change the ply number if needed

Round the ply width

Dial ammo from the based on size, or just weight

Double check the ball drag... or set it to a large hex nut (all this does is slightly more drag)

I'm sure some of you guys can figure out the rest... If in doubt add calculus


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## Hrawk

Translated version:


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## Tobse

Thanks Hrawk!

But you need the band leght in the yellow box, not the draw length. If your draw length 850mm you need 170mm for the calculator.


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## Hrawk

Tobse said:


> Thanks Hrawk!
> 
> But you need the band leght in the yellow box, not the draw length. If your draw length 850mm you need 170mm for the calculator.


My bad, I must have read your formulas wrong.


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## lightgeoduck

Dude, that is so cool!... I, as well, was going to offer the translation, but Hrawks is good enough ..

LGD


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## Tobse

Hrawk said:


> Tobse said:
> 
> 
> 
> Thanks Hrawk!
> 
> But you need the band leght in the yellow box, not the draw length. If your draw length 850mm you need 170mm for the calculator.
> 
> 
> 
> My bad, I must have read your formulas wrong.
Click to expand...

no, it was me, i made it at night and write Auszugslänge instead of Bandlänge lol...

if you are not a butterfly shooter you can made the Rubber compensation 0,3 higher or so, check it with a chrony... i have only butterfly settings here.


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## Tobse

i just want to say, if you want to use the speed calc, and you want good result, you can only use 4 of them, for every 16 bands it is not very good...

https://docs.google.com/file/d/0BxmVItl59G_ZMEZNdzRqZU5xbFU/edit?usp=sharing


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## Charles

No doubt I am just being a dolt, as usual. But I tried playing around with Hrawk's translation of the calculator, and just was not getting decent results. I would really appreciate it if someone could post a step-by-step set of screen shots showing how to use the calculator. For example, what bands are needed to shoot a 45 gram projectile at 55 meters per second? For another example, what bands are needed to shoot a 10 gram projectile at 107 meters per second? And some examples in which one starts with bands, draw length, and ammo weight, and calculates velocity.

THANKS!!!!

Cheers .... Charles


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## Crac

Charles, your questions have infinite numbers of solutions!

Generally:

 I'm not sure 40 fpe is possible without substantially increasing the draw force.... But I'm sure it's still in your reach.

49.3 fpe not 50??? ([email protected]/s) you must SOME fork extension if you're going to pull it with the similar force to your previous fine efforts: Hmmm; same force, 4 foot extension plus 30.5 inch draw -should be over 50 fpe...

And 10g, not 1g for 107 m/s? (57.27J / 42.42 ftlb or a tenth of these!)

Surely you could *just* back of envlope the sizes?

Secondly... perhaps more importantly: Then these tools are written often they have a prefered 'direction' it maybe not be so simple to turn the whole problem around. One could study the preview to see how I added the guidance figures (The green input field is often linked into the orange output field straight above it)


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## Charles

The question I have is how to use the calculator. I do not seem to have figured out how it is to be used to calculate anything useful. Probably just a short between the keyboard and the chair.

Cheers .... Charles


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## Tobse

Charles said:


> No doubt I am just being a dolt, as usual. But I tried playing around with Hrawk's translation of the calculator, and just was not getting decent results. I would really appreciate it if someone could post a step-by-step set of screen shots showing how to use the calculator. For example, what bands are needed to shoot a 45 gram projectile at 55 meters per second? For another example, what bands are needed to shoot a 10 gram projectile at 107 meters per second? And some examples in which one starts with bands, draw length, and ammo weight, and calculates velocity.
> 
> THANKS!!!!
> 
> Cheers .... Charles


Charles, You must fill in the green box from the top down - Bandlenght - ammo weights and bands thicknes.

and now you will see in the blue box everything you can get with this ammo and your band.

*BUT you have to know, this calc dont work with big ammo! *

you need other settings for the big stuff! it´s just made for *Targetshooting to find fast bands with a **flat **trajectory, *for big ammo you will never find bands for a flat trajectory because they are always slowly...

even your 10 gramm ammo is actually a heavy ball! this calc work at best with 2 - 4 gramm balls.

if you want to shoot a 10 gramm ball at 107 m/s... this will be very very hard to made...

anyway i made you a screenshot from the calc there you can see what kind of bands you need for this job... but i think it will be NOT succsessfully


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## Charles

Thanks so much, Tobse. That helps a lot.

Cheers ..... Charles


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## Tobse

Glad it helps 

you could also say that this calc displays of course bands for heavy 64 gramm ammo *and* a flat trajectory! BUT... *no one* can draw this bands 

so this calc shows also big balls are not good for targetshooting  because you can´t shoot it with fast bands...


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## Dayhiker

Thanks Tobse and Hrawk. This is a welcome and valued addition to the list of tools I have gleaned from this forum that enable me to avoid over-taxing my limited brain power.


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## Viper010

Dayhiker said:


> Thanks Tobse and Hrawk. This is a welcome and valued addition to the list of tools I have gleaned from this forum that enable me to avoid over-taxing my limited brain power.


same for me, thanks a lot guys!


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## ShesHowdew

I'm a total noob! This is a great tool! Thank you!


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## studer1972

Makes me want to sing 






Thanks gents, good tool.


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