Slingshots Forum banner
1 - 7 of 7 Posts

· Premium Member
Joined
·
3,228 Posts
This slingshot is the core of all my own-designed slingshots to date. I have ruthlessly stripped away everything but the common elements, preserving only that which worked and discarding everything else. If you overlaid this over The Shootist and the T1, you'd see the almost same cant and offset to the handle, the same fork width, the same low fork height, the same primary contact points with my hand. It shares the forefinger cut out as the Black Silk, the Thumb ramp of the Shootist and the thick rounded fork tops of Clone Trooper (based on Perry's PS-1) and the subsequent thick forks I made in Syn Wood, Black Acrylic and home made laminates. It has the stripped down, weight saving thinness of the carbon and Acrylic T1's and the construction and finish of the forged iron and desert ironwood traditional Y-fork.



I know it's ugly as sin and it won't win any competitions. I deliberately threw aesthetics out and allowed only the fit of my hand and the biomechanics of my hand, arm and body to shape it. It shoots better than the T1 slingshots and weighs a fraction of the full ergo target shooters (Shootist and Black Silk). I plan to take this jungle trekking as my primary food getting tool for anything reckless enough to wander into range.

The first thing you might notice is the profile was based on the T1. I simply marked every part that was in contact with my hand and under pressure and cut away the rest. The only part below the fork tips that my hand is not in direct contact with is the 3/4" between the forks. The forks themselves have been narrowed to the point where there is nothing showing but flesh.

Another departure is that I've increased the cant of the handle compared to the fork tips to 45° from about 25° on the T1. This means my radius and ulna (the long bones of my arm) aren't at all crossed during the draw and shot.

As the handle serves as the middle, ring and pinkie brace, no front slab was needed. There is a single protrusion, a block of desert ironwood to support my weak thumb knuckle. This is affixed with epoxy and seated Corby pins attached to the frame by bolts that are tapped and peened through the frame. In retrospect I should have forged the thumb knuckle support to fit my hand rather than adding a block, but I was exploring a potential new board-cut template.



This slingshot is all about the way the frame takes band tension forces and transfers them to and though my fingers, hand, wrist and arm. This is shown by the following series of images. Taking the T1, I looked at where I could feel pressure and how it could be better distributed so that by finger joints were supported and how the thumb and forefinger should pass the force through my wrist and the long bones of my forearm. I wanted the fingers to have to exert as little force as possible, with most of the pressure taken by the inner knuckle pads of the forefinger and thumb, with an even distribution and then have the forces go straight down those fingers' metacarpals (the bones inside the palm attached to the fingers).

Below you can see how the main contact points of my hand match the shape of the frame almost perfectly. With a wrist band, I can almost shoot it open handed like this.



The fingers wrap over. The forefinger provides directional finesse and the lower fingers lock the handle in and frame under draw and the flip on release. The palm pad at the bottom is under less pressure. It's offset to centre the wrist cord on the bottom of my wrist. I sometimes use the hole to secure it to a karabiner on my belt.



With the frame locked down at the forefinger and handle, the thumb takes fully half the force under tension and so the thumb knuckle must be supported, or it will over extend, risking repetitive stress injury and inducing a tendency for the fork to twist to the right.



Under the support of these three contact points all the force is transferred through the thumb and forefinger's metacarpals. The force is centred directly between them through the middle of my wrist, much like an archery bow handle. The wrist can flip up and down, but the centrepoint between the fork tips is very low when canted forward under draw and the lower three fingers can well handle it. The wrist lanyard, which is a braided leather thong tipped in my own nickel silver aglets, simply allows for thoughtless and near effortless shooting. Granted, I can feel a lot of force going through my thumb and forefinger knuckle when shooting with Hunter Bands, but I generally use these for upper limit testing and to reveal any flaws in my design.



Today I received my Field and Express Bands from Bill. These seem like a marriage made in heaven with this frame. They are fast, accurate and the power is ideal for the fork. These are Field Bands pictured.



The rounded and fat 1/2" Teflon fork tips should help to reduce wear on the bands. They make the delivery feel sweet.
 

· Premium Member
Joined
·
3,228 Posts
Well, I'm quite surprised that nobody's pointed out that it looked like a deformed frog or something.

I was avoiding posting any directly front-on pictures of the T1 until now, but there's no reason why I can't show it I suppose. I need to show it to explain how this came about. Here are two pages from my 10 page design analysis on the T1 and showed the genesis of The Core's design as a 'what if' study.




I guess you can see, my design style is a mixture of freestyle creativity in the workshop (when in the workshop drinking English beer) and deliberate analytical engineering at home (when I should be doing something far more important like forcing my girl to do endless pages of mind numbing and soul breaking repetitive Chinese calligraphy exercises.) That's what you get for having mixed cultural heritage.

Wow. This is really something new! Congrats.

I would LOVE to see a video about that slingshot in action. Any chance?

Oh, and I nominate this beauty for slingshot of the month - May.

Jörg
Jörg, I have recorded two short videos at 320 res x 15 fps and uploaded them to the following temporary links. You may use them on your channel if you wish.

http://www.l2i.org/temp/CoreShot.AVI
http://www.l2i.org/temp/CoreDesign.AVI
 

· Premium Member
Joined
·
3,228 Posts
hey Picasso
Yes, I suppose it does look like a slingshot that was sculpted by a surrealist on absinthe. There's probably a bit of Salvador Dali's melted clocks in there too. Not that I'm an artist, or even a student of art. It just happened that way; it came into being and it turned out that it shot well, so it stayed out of the scrap bin.
 

· Premium Member
Joined
·
3,228 Posts
Discussion Starter · #26 ·
or throw it all away and take a completely fresh start...
Absolutely Do NOT!
My tendency to move on from already proven designs is what created this in the first place.

I will probably take this one hunting next month, but in the meantime I plan to train and experiment with new ideas.

If I evolve the design: I've done some back of the envelope load modelling and I think I can reduce the weight with a partial or full composite construction. I can make this out of G10, carbon fibre, aluminium or maybe even Kydex. I can't reduce the size because that's determined by my hand, but I can eliminate the thumb ramp, instead building the support into a three dimensionally curved fork. I can forge sweeping curves into the tips to eliminate the need for the tips. These changes would offer important advantages. The thumb ramp takes as long to make as the fork, because of the precise seated drilling and the finish work. The tips are a pain too; Teflon doesn't stick, so they have to be mechanically fitted with two nickel rivets per fork.

If I do something new: Well, I've a couple of ideas. First, some people like to shoot sideways, so I could work on a C-fork. This design has already lost all symmetry, so it makes a good platform for an upright shooter. Second, I could reduce the forks even further but shield the hand with an above-the-hand design that works more like a glove than a fork.
 

· Premium Member
Joined
·
3,228 Posts
Discussion Starter · #27 ·
Sorry, we are at crossed purposes. To clarify, when I said I was considering throwing out the design I meant the premise that the fork must be supported my the thumb, forefinger and knuckle pads of the other fingers, not the physical frame I had made.
 

· Premium Member
Joined
·
3,228 Posts
Discussion Starter · #29 ·
1 - 7 of 7 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top