Homebrew Big Shot

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7 years 4 months ago #136869 by Davej
Homebrew Big Shot was created by Davej
I finally got my mini-mill back together after several years of neglect, and started on my long stagnant Big Shot project. The problem is that I've now forgotten all the fine details. Can anyone tell me what some reasonable design parameters would be for the stretching of the tubing? I am using an aluminum painter pole and some latex tubing that is something like 14mm OD with a 2mm wall thickness. The tubing slides onto 1/2" steel U-bolts.


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7 years 4 months ago #136878 by Nimbadon
Replied by Nimbadon on topic Homebrew Big Shot
Hey Dave, when you say " stretching of the tubing ", are you talking about pouch design or attaching the pouch to the tube?

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7 years 3 months ago - 7 years 3 months ago #136883 by Davej
Replied by Davej on topic Homebrew Big Shot
Oh, I was wondering about choosing a length for the tubing and estimating the necessary pole length. Attachment options for the pouch would also be of interest. I expect to build the pouch out of 2-inch tubular webbing and am collecting the material I will use to build the trigger. I don't need to be able to shoot very high.
Last edit: 7 years 3 months ago by Davej.

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7 years 3 months ago #136885 by TreeTramp
Replied by TreeTramp on topic Ballistic projectiles anyone?
Basic math needed for 5/8” od x 3/8” id latex tubing

I found a book that addressed the kinetic energy calculations that bases “horsepower” on tubing size that is elongated to various percentages of elasticity.

It warps my mind but the results are easy to follow.

I use a 40 pound bag of salt to stretch each band and measure its extended length compared to its relaxed length for a single band launch tube so a dual band sling shot will have twice the power.

10” band pulled to 20” long is at 100% elongation and has a little power.
10” band pulled to 30” long is at 200% elongation and has decent power.
10” band pulled to 40” long is at 300% elongation and has the most power.

I aim to fall between 300% and 400% as elongation becomes very hard to pull and you approach the breaking point at 500%.

Determine your draw strength in pounds that you can pull easily.
Determine your elongation distance of your devices arm.
Then you can determine the relaxed length using:
(drawn length-relaxed length) divided by relaxed length

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7 years 3 months ago #136890 by Davej
Replied by Davej on topic Ballistic projectiles anyone?
Hmmm... interesting. I have read that the Big Shot uses 19" of tubing length?

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7 years 3 months ago - 7 years 3 months ago #136929 by Nimbadon
Replied by Nimbadon on topic Ballistic projectiles anyone?
I made this "little shot" for advancing in trees where it's hard to get a good swing going, might give you some ideas

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Last edit: 7 years 3 months ago by Nimbadon.

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