Center of gravity is major factor

Hoerchner

Hoerchner

Joined
Jan 8, 2006
Messages
111
After reading the throwing book that relies on a lot of electrical tape at the handle end of a long blade, the book that introduces the "circus-throwing" term, and I apologize for not having the name handy, it occured to me that the basic reason that style works is by moving the center of gravity away from the middle to discourage rotation and then using a little pressure as the weapon is thrown to further discourage turning.

Using that as the basic theory I have made two types of knives, some with weighted fronts and another with a weighted rear half of the handle, and I have gotten very accurate and consistent with both styles. Relatively speaking, of course.

For the end weighted knife I used a $25 tanto tactial style knife, removed the plastic handle, bolted close to a 1/2" slab of brass to each side of the knife to replace the last 3"s of the handle, a slab of wood on each side to complete the handle, and while it weighs a ton it will go where you want it for 10 to 12 feet and penetrate a car door with ease. It still fits in the sheath, too.

The front weighted ones are the most fun, and they are just cheap dagger style throwing knives with more brass bolted up to about 4"s from the tip and then attached to bamboo handles filled with Gorilla glue for strength, stray pins and a hose clamp or two, and the length is 10" to maybe 24", I don't have them with me for more accurate sizes, and they will hit maybe 6 to 12 inch circles at 12 to 20 feet, and poker cards under 12 feet 75% of the time or better. No spins, any random distance or angle.

Anyway, that's my theory. By getting the center of gravity within 25 to 30% from either end, the spin can be eliminated within limits, of course, and you can just put the point where you want it. Any feedback? Erich
 
I think your physics are very well applied, sir!

Also, I might add that you may be the first person who can stick a tanto! That's normally the least "throw friendly" of the knives, and I'm impressed.
 
As the author of the book in question, I am quite interested to hear that you have gotten good results using my methods, but also that you have evidently been able to front-weight knives and reduce spin. That's a new one on me. You may have discovered something.

In my later works, , that is, my video and the updated version of the book, I have been giving a more precise formula for knife balancing: 38 percent of the total length of the knife, on the handle side, should be the balance point. (This is according to "phi", the "golden section", if you're interested in geometry).
 
Ralph,

Do you mean the balance point should be 38% of the knife's length starting upward from the butt of the handle?

That's interesting. How did you make the association with this and phi? There's quite a story in that.
 
Yes, that's it, 38 percent from the butt or 62 percent from the point.

I was reading about phi in a book about ancient Egypt, which claimed the proportions of the pyramids are full of phi, and suddenly it hit me that phi might very well be the point at which I liked a knife to be balanced. I made careful measurements and a series of experiments and confirmed that phi works well for all types and sizes of knives, at least for me. So since then, I've gone with it as the "perfect" balance point. I first introduced this in my original "gold edition" dvd, a couple of years ago, and it appears in all my materials since.

I should point out that a "phi" knife is not necessary to throw in the style I use; I have demonstrated the ability to throw all kinds of objects not balanced at phi on video (do a search for Ralph Thorn on youtube and you will find big sections of my video free online, by the way, some of them placed there by friends of mine, some by strangers, as far as I can tell). My style of no spin depends mostly on basic grip and especially wrist action.

But a "phi" knife does help and makes my no-spin easier to learn. There's a video clip showing off the new knife design we did online somewhere, too....
 
eralphthorn said:
I was reading about phi in a book about ancient Egypt, which claimed the proportions of the pyramids are full of phi...
Click to expand...
Not surprisingly to you, Ralph, but perhaps to the reader first hearing this term... phi is used all over the place. Most table designs follow the principle, as do architectural room sizes. A wide variety of web pages are laid out according to the concept (not BFC, though! :)), and more.

Check it here.

So I assume it's actually 38% from the butt end, or 61.4852916% from the tip end... to be precise. :D
 
I am out of town right now, so I can't check my throwers precisely, but it makes sense that there is a center of gravity point that is easier to control than others, or rather a point that is the easiest, and the closer the actual is to the ideal, the easier to control. And why wouldn't phi be that point, since there is something about that ratio that is beyond our current ability to completely quantify. And, if testing supports it, which it evidently does, that adds even more mystery to why phi is so often "right". Very curious, indeed.

I will get up some pics of my forward-weighted throwers, and the tanto, when I get back home. Erich
 
Hoerchner said:
...since there is something about that ratio (phi) that is beyond our current ability to completely quantify.
Click to expand...
I disagree. If you check the link I provided, you can see the formula for yourself. It is, by definition, quantifiable.

Ralph certain quantified it with his 38:61.4852916 ratio. I'd say that's pretty well quantified. Ralph's got it down to a ten-millionth of a foot.

But your point about the center of gravity is well founded: all objects rotate or tumble around their center of gravity. If the center of gravity is controlled (which would utilize the least amount of force and energy), all rotations of the knife will be controlled outward.
 
eralphthorn said:
I should point out that a "phi" knife is not necessary to throw in the style I use; I have demonstrated the ability to throw all kinds of objects not balanced at phi on video (do a search for Ralph Thorn on youtube and you will find big sections of my video free online, by the way, some of them placed there by friends of mine, some by strangers, as far as I can tell). My style of no spin depends mostly on basic grip and especially wrist action.
Click to expand...

LOL You will also find quite a few videos of a crappy 80's tv show called Thorn Birds.
 
If I call my lawyer it will be to sue the Chinese, who pirated the whole video, as I was told by someone in Taiwan.

I find phi pretty fascinating but the math scares some people off, so I just give the formula and don't go into any details.
 
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