I believe it would be slightly more optimal if the knife only rotated 1/2 of a rotation. That's what I always aimed for when I was practicing throwing knives, based on the logic that less angular velocity would provide a longer "sweet spot" time during which the knife would be at the optimum angle for deeper penetration, so if the rotation speed was off by a little bit it would still be closer than it would be if the rotation speed was "off" by the same absolute amount but with a 3x-6x faster rotation speed.
In the third video of this series they show an improved version where before throwing the knife one can choose the number of rotations, down to the minimum value of 1/2 of a rotation.
That assumes your child will pick up your interests which is certainly not guaranteed - mine sure did not even though I did try to engage them in similar (though less high-tech) exploits. I have two daughters who both grow up liking typical daughter-things like horses (which is not that odd given that my wife is a horse vet and we have 3 of the critters around the farm) and books instead of all those noisy smelly dangerous things I'm wont to play with. I did manage to build a three-wheeled soapbox car with my oldest daughter with which she then competed - and won - a soapbox race, the thing was loosely shaped like a bee and painted to resemble one, bug eyes included (bubble plastic with some red spray paint does wonders). It had Ackerman steering (cobbled together using rebar and welded-on nuts for bearings) and was dangerously fast, just the way those thing should be.
I can imagine being the neighbor on the other side of that fence.
(peeks head over fence) Hey neighbor, what's that thumping sound I've been hearing all day?
Oh, that? Just my knife throwing machine. Nothing to worry about - I've worked out all the math, and my smart 13-year-old wrote the code, and there's plenty of safety margin with this little block of wood I've mounted on the fence to absorb the knives. And the machine has only activated without anyone telling it to once or twice. Like I said, nothing to worry about!
I loved the project but I couldn't stop thinking about a knife flying over that fence, or getting shot backwards (that thing returned pretty fast). It would have been more sensible to put the block of wood on the side of their house.
This guy should win dad of the year award. Seriously. I gave my son a knife for his birthday when he was 7, but this is taking to a whole another dimension. I should also mention that growing up in eastern Europe back in the day, when I was 14, I was building a gun in my bedroom. It blew a hole in my palm when I was testing.
but a robot knife thrower is not the same in intrinsic priciple as to WHY we throw knives...
Its subtle but significant. The movement of throwing a knife is very same to throwing a person, that is ; the physical body movements of throwing a knife are the same as the movements of throwing a person, swingin a sword etc...
They are movements designed to train you when you dont have an Uki.
Here is me at ~60 feet, knife on knife. But this movement is the same as several throws in Bujinkan.
If I may ask the question you're answering: throwing a knife is almost never an effective attack. distraction, yes; but it seems a silly thing to do in actual training.
As you say, however, knife throwing is very useful as training for throwing anything else. With knives you've got to have so much so close to perfect for it to work at all. When you throw a rock the number of important variables is much lower; but what you've learned with the knives still serves you well.
This is basically correct, the factors that you focus on when throwing a knife are the same factors you take focus upon when throwing a human.
The visuals are the arms, but the core is the hips and their placement.
When you watch me in that all distance vid, you see that the real power comes from the hip rotation, but the precision comes from the upper shoulder displacement. Thus the training of the hips sans Uki.
We've been training with them since ~1989 - but these are the movement styles that map with arts, aside from pure bujinkan movements such like our Soke, Hatsumi - but there is a cadre of bad-ass ninjutsu folks in the US, no not richard whatevere...
but look up van donk, hatsumi, and others in akban, krav maga and bujinkan.
--
There are several throwing style - spin, no-spin, spike (which is the same as no spin) but here is an example of me in my garage
(Also this was handle thrown, which implies no-spin.... but honestly spin throw, blade held is my preference, this is why you see me wearing gloves in vids... Never throw a knife without PPE (gloves)
Trust me - being sliced by a knife leaving your grip at velocity is no fun.
EDIT: Oh Yeah - always grind down the edges of any knife you intent to throw.
The only thing that matters is the pointy part. And the mass of the knife and your skill. The cutting part does not matter.
Do you know why Katanas were curved, because they got more cutting edge ratio with a single pull/strike.
throwing is about puncture, hence stars and blah - and its a portion of why ninjatos were straight - because they were designed for piercing in small enclosures (hallways)
The movements are designed around the "small circle jujitsu" principles as booked by wally jay - not only was he a teacher of mine he was a neighbor and we lived 2 blocks from him in Alameda..
Stuff Made Here (https://www.youtube.com/@StuffMadeHere) also has a lot of similar content which is pretty great. Really respect the generalist skillet that can pull of these kinds of complicated projects.
This is very cool home engineering, and maybe I'm getting soft in my old age... but whenever I see something like this I have to wonder "why violence." I guess it's some inherent trait we have.
The ads are so obnoxious and unskippable that I prefer to close the tab even at the price of missing to watch educating and substantive content. No, I'm not going to buy Youtube Premium.
As someone who has carried a pocket knife for most of my life, I very rarely think of the knife as a weapon. When I was younger, me and my friends would throw knives at trees. Sometimes we would throw hatchets at trees. It's fun and very satisfying to finally stick the knife/hatchet.
It probably could have been simpler and lighter if it accelerated the knife using rollers like a baseball throwing machine. It would have also eliminated the problem of calculating how much to spin the knife.
I don’t think the typical knife is stable in flight that way.
In my layman’s physics, the knife edge will keep pointing forwards if the knife handle would decelerate faster than the knife blade, when thrown that way in isolation.
So, you either need more mass in the knife blade or more air resistance in the knife handle to get that.
Readit News
(peeks head over fence) Hey neighbor, what's that thumping sound I've been hearing all day?
Oh, that? Just my knife throwing machine. Nothing to worry about - I've worked out all the math, and my smart 13-year-old wrote the code, and there's plenty of safety margin with this little block of wood I've mounted on the fence to absorb the knives. And the machine has only activated without anyone telling it to once or twice. Like I said, nothing to worry about!
but a robot knife thrower is not the same in intrinsic priciple as to WHY we throw knives...
Its subtle but significant. The movement of throwing a knife is very same to throwing a person, that is ; the physical body movements of throwing a knife are the same as the movements of throwing a person, swingin a sword etc...
They are movements designed to train you when you dont have an Uki.
Here is me at ~60 feet, knife on knife. But this movement is the same as several throws in Bujinkan.
https://www.youtube.com/watch?v=ks_sBg85suA
Its all in the hips.
Check out Flying Steel and r/throwing
Unrelated but still fun ;
https://www.youtube.com/watch?v=u3I6lbpF68Q
As you say, however, knife throwing is very useful as training for throwing anything else. With knives you've got to have so much so close to perfect for it to work at all. When you throw a rock the number of important variables is much lower; but what you've learned with the knives still serves you well.
The visuals are the arms, but the core is the hips and their placement.
When you watch me in that all distance vid, you see that the real power comes from the hip rotation, but the precision comes from the upper shoulder displacement. Thus the training of the hips sans Uki.
This was my professor ;
https://www.usadojo.com/larry-cary/
Ive trained with every single person in these photos...
Recently my best friend and training partner got back from Israel where he was doing some akban training... https://www.youtube.com/@AkbanOrg/videos
We've been training with them since ~1989 - but these are the movement styles that map with arts, aside from pure bujinkan movements such like our Soke, Hatsumi - but there is a cadre of bad-ass ninjutsu folks in the US, no not richard whatevere...
but look up van donk, hatsumi, and others in akban, krav maga and bujinkan.
--
There are several throwing style - spin, no-spin, spike (which is the same as no spin) but here is an example of me in my garage
https://www.youtube.com/watch?v=KtCYnjeaog4
(Also this was handle thrown, which implies no-spin.... but honestly spin throw, blade held is my preference, this is why you see me wearing gloves in vids... Never throw a knife without PPE (gloves)
Trust me - being sliced by a knife leaving your grip at velocity is no fun.
EDIT: Oh Yeah - always grind down the edges of any knife you intent to throw.
The only thing that matters is the pointy part. And the mass of the knife and your skill. The cutting part does not matter.
Do you know why Katanas were curved, because they got more cutting edge ratio with a single pull/strike.
throwing is about puncture, hence stars and blah - and its a portion of why ninjatos were straight - because they were designed for piercing in small enclosures (hallways)
The movements are designed around the "small circle jujitsu" principles as booked by wally jay - not only was he a teacher of mine he was a neighbor and we lived 2 blocks from him in Alameda..
Some of my favorite stuff on YT by far.
https://www.youtube.com/watch?v=X9zXcnSXNF0
https://www.youtube.com/watch?v=Puo6Vgcbxps
https://www.youtube.com/watch?v=vsTTXYxydOE
Violence was never in my thoughts.
In my layman’s physics, the knife edge will keep pointing forwards if the knife handle would decelerate faster than the knife blade, when thrown that way in isolation.
So, you either need more mass in the knife blade or more air resistance in the knife handle to get that.
Nobody cares which point on a baseball hits the bat, although they do care about spin because it contributes to path changes via aerodynamic effects.