Monday, February 28, 2011

Slingshots stronger than firearms?

I just received my copy of Richard Middleton's interesting book "Man powered bullets".

It was printed before I got into slingshots (book is from 2005), so none of my devices are mentioned :-)

But there is one thing mentioned right at the start that got me thinking: The pendulum test.

Mr. Middleton's conclusion is that man powered bullets will always be slow (in comparison), but can be very heavy.

The formula for energy is e = 0,5*mass * speed * speed. So even a .22lr bullet will show much more energy than even my strongest slingshots - because the speed is squared in the energy formula and only half of the weight counts. Yet when fired into ballistic gelatin or even into water, the slingshot ball will cause a lot more damage and travel more far.

Mr. Middleton employs a different kind of test. He uses a pendulum and shoots against the lower end of it. The more it swings, the more momentum got transferred.

And it happens that a slingshot ball will move the pendulum much more than an air gun pellet or even a .22lr. And he uses fairly weak slingshots.

Momentum, as Mr. Middleton points out, is just mass times speed.

Let us compare.

The .22lr (I am using a yellow jacket HP hispeed type now) flies at 440 m/s and the bullet weights 2 gramms.

That is 194 Joules of energy.

My strongest handhelds shoot a 36 gramm .75 lead ball at 75 m/s.

That is 101 Joules.

So one could assume that the .22 is almost twice as powerful. But let us look at the momentum side.

.22 HP HS long rifle: 0.88 Newton
.75 "slingshot": 2.7 Newton

The pendulum swings out three times more far when you hit it with a slingshot (albeit a serious one).

So not only does the slingshot ball outperform the .22lr Hispeed, it even outperforms a .38 Special - which has 319 Joules of energy, but delivers only 2.13 Newton of momentum.

The slingshot is - momentumwise - on par with the 9 mm Luger (9x19 Parabellum), which brings 2.9 Newton, and just a bit under the mighty .45 ACP (3.4 Newton).

Of course the high speed of the firearms bullets have a lot of advantages. They don't drop as fast when you shoot long distances. The have way better penetration through fabric, skin and bone. But if you look at how much momentum they transfer, slingshots can compete pretty good.

PS: I recommend the book! Worth every penny, and you will have a good time.

Sunday, February 27, 2011

New video: One Slingshot per minute


Saturday, February 12, 2011

Antler Scales On Multiplex Frame

I still have lots of antler material and decided to try using it as scales for a Panther frame.

I started out with 18 mm multiplex, but thinned it down to 16 mm for a better balance.

Then, I cut of two slices from a thick antler part, sawed them out to fit the frame and glued them on. Then, the usual rasp, file and sanding job. Brown ink and linseed oil for the antique finish.

I am blown away by the look and feel of this slingshot, an instant favorite shooter now! The thick handle with the lower part beeing even thicker gives a fantastic grip.

Hammer grip, thumb+index support grip, flats, tubes, a very versatile frame indeed.

Friday, February 11, 2011

Poor man's scope

PMS = Poor Man's Scope!

I did it, just made a frame with an adjustable length of aluminum tube as a sight. The tube is adjustable in 2 ways, vertical and horizontal. It does not even make the frame much more bulky, and the contraption can be disassembled quickly.

Aiming works real well, you can easily center down the length of the tube. In theory, this should deliver reproducable shots as long as you use a fixed anchor point (e.g. the corner of your mouth.

It is too dark to shoot, will do that tomorrow! Can't wait.

Wednesday, February 9, 2011

Jack Sparrow's Slingshot Pistol

I recently watched "Pirates Of The Carribean" again, and I got an idea.

I made a slingshot pistol that looks like a pirate's weapon!

Simple, robust lock and trigger were called for, so a nice push-up system with a metal hinge was installed. The stock design is following flintlock pistol shapes from the 17th/18th century, and of course the pistol had to look antique.

So I used coffee brown ink to dye the multiplex and the round "barrel" rod, then sanded it lightly and oiled it with linseed oil.

I installed a neo magnet to hold (steel) balls in place, but it works with leas just as well.

It is very powerful (three layers of TB gold per side) and also really accurate.

Go hit 'em, Jacky boy!

PS: I filmed the making steps and may upload a how-to video in case enough people want to see it. I am not sure as I already have a how-to for a sling-x-bow.

Sunday, February 6, 2011

Handheld Slingshot Ballista

As announced, I made a handheld inswinger "ballista" slingshot, to find out if it brings additional power.

I made a really wide fork and attached little "plattforms" to the fork ends. Then I added a lever on each side, which can swing inside of the fork. I also installed a stopper that I covered with some black tube, so that the returining lever will be cushioned some.

I attached short pieces of Thera Gold to the shorter end of the lever, and a normal hunter band set to the longer tip ends. I used 8 mm aluminum tube as "axis" for low friction.

It works, and actually I get about 20% more speed than from a conventional frame!

Here is the video:

It's fun.