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Understanding The Physics of Slingshots


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#41 nike

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Posted 21 October 2016 - 09:56 PM

good  :violin:



#42 busySteve

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Posted 18 March 2017 - 03:36 PM

After about almost a year, I have revived the band stretcher.  I am nearing completion.  Here is a video of the semi-functional prototype:

 

https://youtu.be/eYJuDPhxSVI

 


Edited by busySteve, 18 March 2017 - 03:36 PM.


#43 busySteve

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Posted 24 March 2017 - 06:51 AM

So the band stretcher phase 1 is basically complete. In this demonstration is measured the banding of my axiom champ and calculated a 221 fps velocity. When a measured it with the Chrony, I got 221 fps. That's pretty neat.

https://youtu.be/bHnlaZkOac4

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#44 Dr J

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Posted 24 March 2017 - 07:54 AM

Are you guys serious! If you have to go through all of this to enjoy a slingshot then there is no way it can be fun.


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#45 busySteve

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Posted 24 March 2017 - 08:00 AM

I am a computer scientist, this is how i have fun. But, it still does not equal plinking a can 20 meters.

#46 treefork

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Posted 24 March 2017 - 08:12 AM

You need to take a break from the computer and truly enjoy what slingshots are about . No measuring devices or data needed . Allow a deeper part of your brain to engage and give  you all the necessary data to shoot .  When you shoot enough a chrony isn't needed . You know what your bands are doing . Most of all yo're have a pure child like fun . 



#47 busySteve

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Posted 24 March 2017 - 08:26 AM

I really appreciate that. I don't do this all day... when I take a break, which I do as often as possible , I shoot with no devices. But, I like to exercise my gray matter from time to time. Thanks again for the advice.

#48 busySteve

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Posted 24 March 2017 - 08:45 AM

One sarcastic question though... how did ya'll respond to this post so quickly? Smoke signals or was it with a computerized device? Hmmmm.... have fun today folks!

#49 Chesapeake Inuit

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Posted 24 March 2017 - 12:30 PM

Scientists recently made a "time crystal" at the University of MD.  Really.  Something about it being active (motion) in time but not in space.  It hurts my head thinking about it and even some physics types do not understand it.

 

Even still I will eventually understand it if only in a very, very crude way.

 

I am glad there are scientists like you that work on fun projects like your band stretcher.  Amazing that the prediction was dead nuts on!

 

A lot of the info in this thread hurt my head as well but it still very cool to work on it "just cause."

 

Not as much fun as shooting but still very interesting.  I'm going to get that book your recommended.

 

Top marks to you for your work!



#50 busySteve

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Posted 24 March 2017 - 12:50 PM

Scientists recently made a "time crystal" at the University of MD.  Really.  Something about it being active (motion) in time but not in space.  It hurts my head thinking about it and even some physics types do not understand it.

 

Even still I will eventually understand it if only in a very, very crude way.

 

I am glad there are scientists like you that work on fun projects like your band stretcher.  Amazing that the prediction was dead nuts on!

 

A lot of the info in this thread hurt my head as well but it still very cool to work on it "just cause."

 

Not as much fun as shooting but still very interesting.  I'm going to get that book your recommended.

 

Top marks to you for your work!

 

Oh my, what a compliment, I nearly cried... but smiled instead.  I must offer my thanks!

 

busySteve



#51 TimR

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Posted 24 March 2017 - 02:01 PM

You're quite the craftsman, I am in awe.

 

FYI - well you probably know this but maybe it will help somebody - Middleton covered some of this, less technically, in Man Powered Bullets.

Google Amazon Practical Guide to Man Powered Bullets.  I tried to link but this PC blocked it.

 

It's a must read for anybody who is into slingshots.  I got it interlibrary loan but it's probably worth buying.



#52 aiping

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Posted 25 March 2017 - 04:12 AM

Hi Steve, great job and achievement !!!

 

Can you also calculate tapered bands for example

 

Thera band black / length 27 cm / taper 9 cm to 3.5 cm ?

 

Thanks in advance and all the best from A-Ping

 



#53 busySteve

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Posted 25 March 2017 - 06:08 AM

What is your draw length?

#54 busySteve

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Posted 25 March 2017 - 05:13 PM

What is your draw length?

Aping,

I assumed 32in draw length and ran a test. I also assumed 10mm steel ammo. Photos and video are below.

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https://youtu.be/Ff3LA48dPME

#55 busySteve

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Posted 25 March 2017 - 06:48 PM

You need to take a break from the computer and truly enjoy what slingshots are about . No measuring devices or data needed . Allow a deeper part of your brain to engage and give you all the necessary data to shoot . When you shoot enough a chrony isn't needed . You know what your bands are doing . Most of all yo're have a pure child like fun .

I put your advice into practice and made it a point to have have today. The way I did was by way of a recently obtained G10 mini-champ from Rayshot. It is amazing!!!

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I spent hours shooting 1/4 inch and 5/16 steel at cans. I have no idea how fast I was shooting, or the tension of my bands, and that's ok with me . Your advice went a long way and the kid inside is very glad I did it. So thanks again.

busySteve

#56 aiping

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Posted 25 March 2017 - 07:04 PM

Hi Steve,

you did much more than I expected, thank you so much!
I need to apologize as I did not specify the exact draw length and ball dimensions / weight:

- draw length 53-54 inch
- steel ball 9,5 mm

One thing maybe important to mention that the 9 cm TBB is wrapped around the fork of my Semi-tube slingshot so that there is no interference with the rubber itself. My latest results with ChronoConnect App :

9 x 3.5 cm taper / 26 cm length

- Thera Band BLUE => draw 150 cm for 9.5 mm steel will give you around 350 fps / livetime around 20 shots

- Thera Band BLACK => draw 135 cm for 13 mm steel will give you around 300 fps / livetime around 30 shots

http://slingshotforu...erties-changed/

I will repeat these tests ASAP.

Again thanks!!! A-Ping

#57 busySteve

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Posted 25 March 2017 - 07:52 PM

Hi Steve,

you did much more than I expected, thank you so much!
I need to apologize as I did not specify the exact draw length and ball dimensions / weight:

- draw length 53-54 inch
- steel ball 9,5 mm

One thing maybe important to mention that the 9 cm TBB is wrapped around the fork of my Semi-tube slingshot so that there is no interference with the rubber itself. My latest results with ChronoConnect App :

9 x 3.5 cm taper / 26 cm length

- Thera Band BLUE => draw 150 cm for 9.5 mm steel will give you around 350 fps / livetime around 20 shots

- Thera Band BLACK => draw 135 cm for 13 mm steel will give you around 300 fps / livetime around 30 shots

http://slingshotforu...erties-changed/

I will repeat these tests ASAP.

Again thanks!!! A-Ping

That length of stretch is too long for my stretcher by several inches. It might be too tight as well. Let me see what I can do. I should make it butterfly friendly. So I'll have to set it up with cable and longer wood. I may make a floor mount version to eliminate these restrictions.

I'll keep ya'll posted.

#58 busySteve

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Posted 25 March 2017 - 08:57 PM

Hi Steve,

you did much more than I expected, thank you so much!
I need to apologize as I did not specify the exact draw length and ball dimensions / weight:

- draw length 53-54 inch
- steel ball 9,5 mm

One thing maybe important to mention that the 9 cm TBB is wrapped around the fork of my Semi-tube slingshot so that there is no interference with the rubber itself. My latest results with ChronoConnect App :

9 x 3.5 cm taper / 26 cm length

- Thera Band BLUE => draw 150 cm for 9.5 mm steel will give you around 350 fps / livetime around 20 shots

- Thera Band BLACK => draw 135 cm for 13 mm steel will give you around 300 fps / livetime around 30 shots

http://slingshotforu...erties-changed/

I will repeat these tests ASAP.

Again thanks!!! A-Ping

That length of stretch is too long for my stretcher by several inches. It might be too tight as well. Let me see what I can do. I should make it butterfly friendly. So I'll have to set it up with cable and longer wood. I may make a floor mount version to eliminate these restrictions.

I'll keep ya'll posted.
I was able to shorten the hook cable an stretch to 51 inches. The numbers gathered resulted in a calculated 347.59 fps with 9.5mm steel. Here's a pic of the results:
aae7561749bb24012864370448712d95.jpg

#59 aiping

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Posted 27 March 2017 - 02:36 AM

Steve! You're incredible fast. And I must promise my wife to clean up the attic before using it again as a shooting range, call it busy A-Ping.
However, you proved that 350 fps with
9,5 mm is no black magic. Drawweight is about 10 kg? A draw of 150 cm should produce between 385 and 400 fps. So it's now up to me to deliver ☺.

#60 Imperial

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Posted 27 March 2017 - 03:26 AM

i think theres a flaw in this study. how long are  you holding the shot before letting go ? does it make a difference ? 






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