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Slingshot-on-a-Stick Progress

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Unread postAuthor: saefroch » Sat Dec 04, 2010 9:37 am

boyntonstu wrote:I would rather walk around with a light weapon that can be instantly drawn with ease and fired with its maximum energy output.
Please do read my previous post. I consider his data invalid on the loss of energy with time after the bands are stretched.

boyntonstu wrote:Can you think of a way to build a mechanism that will assist your fingers holding the pouch without any moving parts?
Your fingers are already a moving part. I do not see the significance of using your fingers over a device you've built yourself.

I do not contend that this device is better than a normal slingshot, please try to understand that. I also do not contend that it is easier to hold the pouch back with friction than with friction AND one's arm. The stick is simply replacing the arm, and the fingers aren't under any less stress than a normal slingshot.

What's the draw weight on your latest model anyway?
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Unread postAuthor: boyntonstu » Sat Dec 04, 2010 10:25 am

Take a rubber band and a fish scale.

Pull it and hold it at a fixed length.

Watch the scale and you will see the force decline with time.

Your conclusion differs will all known experience.

Until you do this experiment and correct your statement, I will no longer respond to your unscientific posts.
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Unread postAuthor: velocity3x » Sat Dec 04, 2010 10:50 am

boyntonstu wrote:I would rather walk around with a light weapon that can be instantly drawn with ease and fired with its maximum energy output.


Light weight and instantly drawn? If your goal is loading/firing speed and convenience of carry, IMO a conventional, hand held slingshot would be far superior to one extended 4' in front of the shooter.

As you said:
"Crossbows are not slingshots and slingshots are not crossbows."

Certainly no offense intended but, I think if a shooter needs a slingshot with the power produced by 4' of draw, it's time to switch to a crossbow. Isn't this much like attaching a handgun to a 4' stock attempting to make it achieve rifle performance?
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Unread postAuthor: saefroch » Sat Dec 04, 2010 11:02 am

Experiment is completed, using a bungee cord and a Zebco Deliar 228 fish scale. I conclude that a non-digital force measurement device cannot measure the heat differences that Mr. Middleton describes, since his data shows about a 7.7% loss due to temperature, and my fish scale has about a 7.3% error, so the fish scale itself swallows all but a .4% change. This is why nobody ever observes the effects he has cited, since nobody measures the draw weight of an elastic material with very high accuracy over a significant period of time.

Experiment is unable to show the effect you cited. Do you have any other ideas? Honestly this has piqued my interest now.

velocity3x wrote:Isn't this much like attaching a handgun to a 4' stock attempting to make it achieve rifle performance?
No, not really. It's more like putting a bipod on a .22 rifle in an attempt to make it a sniper rifle. I do agree with boyntonstu that his design is superior to normal slingshot designs for ease of use. Also, it's not extended in front of the shooter until you're aiming it, and even then you can move to your side like a traditional butterfly draw if you don't want it poking out so far.
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Unread postAuthor: boyntonstu » Sat Dec 04, 2010 11:29 am

velocity3x wrote:
boyntonstu wrote:I would rather walk around with a light weapon that can be instantly drawn with ease and fired with its maximum energy output.


Light weight and instantly drawn? If your goal is loading/firing speed and convenience of carry, IMO a conventional, hand held slingshot would be far superior to one extended 4' in front of the shooter.

As you said:
"Crossbows are not slingshots and slingshots are not crossbows."

Certainly no offense intended but, I think if a shooter needs a slingshot with the power produced by 4' of draw, it's time to switch to a crossbow. Isn't this much like attaching a handgun to a 4' stock attempting to make it achieve rifle performance?


A rifle is aimed by lining up the front and rear sights.

The further apart they are, the more accurate the aim.

Having the fork 4 feet in front of you and the pouch also in front of you is a very good way of sighting using 2 distant points.

Steel coils springs on cars weaken over time.

It does not take a leap of imagination to understand that the stretched rubber force declines much more rapidly than steel.

IMO A rubber band would be a better choice than a bungee for the test.

Try one and report back.

As to the Stick replacing your arm when shooting a slingshot:

The Stick does not need a wrist brace because there is no force on the wrist.

A drawn slingshot has the drawing elbow bent more than 90* and with the butterfly close to 180*.

With the Stick, always less than 90*.

With a slingshot there is air between the drawing arm and the fork.

With the Stick, the air is replaced by wood, hence no force required.

Viewing the video should underscore the advantages of the Stick design.

This is not rocket science, but it helps that I am a retired rocket scientist.


.
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Unread postAuthor: saefroch » Sat Dec 04, 2010 1:09 pm

IIRC, nobody said anything about a force on the wrist...

Does the angle of one's elbow really matter with the stick? I understand the benefits of holding it out in front to aim, but wouldn't it still not strain the elbow if one held it in a position like a normal butterfly draw? I understand this is impractical, but could have some benefits if one's wrists became tired from resisting the relatively large torque applied when holding it only at the end.

With a rubber band, error is still simply too massive (~6.3%, and there's no way I can detect a 1.4% difference on a fish scale) to show any measurable difference.

boyntonstu wrote:Viewing the video should underscore the advantages of the Stick design.
I'm not disparaging the stick design, never have.
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Unread postAuthor: boyntonstu » Sat Dec 04, 2010 1:37 pm

Pull start a lawn mower starting with with your elbow past the 90* position and compare the strain with your arm straight out and going to 90*.

Yes, it really matters.

Wrist rockets and low fork designs were developed to lower wrist torque.

There is another major advantage that the Stick offers over a fork held slingshot; back snap to the fingers.

A painful experience when shooting heavy bands and they snap back.

This discussion would be very short on http://slingshotforum.com.

You may find it educational.
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Unread postAuthor: saefroch » Sat Dec 04, 2010 2:12 pm

I'm not talking about elbow strain when pull-starting a mower (for then it's definitely significant), I'm referring to elbow strain when holding the slingshot-on-a-stick in the drawn position. Does the angle of the elbow matter then?

The torque I'm referring to is not generated by the position of the fork or the drawn bands, but by the weight of the slingshot-on-a-stick trying to rotate about the wrist joint that's holding it. Throwing some reasonable (I think) numbers at it:

I measured a random 4' plank at 2.5 pounds, and estimate the rest of the weight of your setup at .5 pounds, I get 2.22 pound feet of torque, assuming you were shooting at an angle down of about 60 degrees in the video.
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Unread postAuthor: boyntonstu » Sat Dec 04, 2010 2:37 pm

I'm not talking about elbow strain when pull-starting a mower (for then it's definitely significant), I'm referring to elbow strain when holding the slingshot-on-a-stick in the drawn position. Does the angle of the elbow matter then?

Yes, pulling 25 pounds or holding back 25 pounds requires muscles.

Since you can rest your palm against the end of the stick, you are no holding back with your wrist.

Surprisingly, the thumb and the index finger closed around the marble dose not feel like they are straining.

Try holding your extended bungee with a stick between one end and your palm while also holding that end with two fingers.

Or, attach to bungee to one end of a stick and draw it incrementally as you grasp further up the stick.

Compare that to air.

Remember the forward hand which act to support the Stick weight and it also acts as a pivot point for the lever.

The fork end of the Stick wants to go down about the pivot due to gravity, while the stretched rubber wants to pull it towards you.

As it falls, the rubber resists the down moment.

Believe me, it is really worth doing it this way.

Everyone who has tried it has expressed surprise at the difference.

There is a lot in play here.
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Unread postAuthor: saefroch » Sat Dec 04, 2010 2:57 pm

boyntonstu wrote:Yes, pulling 25 pounds or holding back 25 pounds requires muscles.
You still haven't answered my question, so I'll answer it for myself, just for demonstration purposes. No, the angle of the elbow does not matter. Do a little experiment to prove this if you want; squeeze your thumb and index finger together as if holding a pouch. Change the angle of your elbow. Does that cause strain?

boyntonstu wrote:Surprisingly, the thumb and the index finger closed around the marble dose not feel like they are straining.
Could that be because your draw weight is only 25 pounds?

Of course one could support the stick by extending the left hand out to support it, but I thought in the video you were demonstrating that it could be held from the very back end. Question answered, thanks.

If the extended rubber is parallel to the stick (sin(90)=0) it doesn't place any torque on the stick.

Would you please stop trying to convince me that the stick design is superior to a normal slingshot? I was convinced from the first time I viewed the video that it was.
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