Knife Throwing Machine Part 3 - Physics of Penetration

Visit brilliant.org/QuintBUILDS to start your 30-day free trial learning STEM, and the first 200 people will get 20% off their annual premium subscription.
Company that built my custom hard case for the thrower:
www.SKBCases.com
Printer for the 3D Printed Axe:
formlabs.com/3d-printers/form...
If you liked this content and want to support more of it the best thing you can do is join my super awesome Patreon supporters who made this video possible. To become one of them visit:
/ quintbuilds
If instead you prefer a one-time donation option, here's a PayPal address you can use: [e-mail]
Detailed Behind the Scenes Video on BUILD2:
• Stabbing Science - Beh...
Merch: www.quintbuilds.com/shop
Details on accessing the DISCORD server can be found on my Patreon page. If you want to discuss projects with others and get my input, that's the best place to do it.
2nd Channel with engineering and coaching to help you learn:
/ @build2
Quint's Background: • Quint reveals his back...

[@QuintBUILDs]

This channel would not exist without the support of patrons. I'd love it if you'd consider visiting www.patreon.com/QuintBUILDs and help support the channel. That is, assuming you like this kinda stuff and want to see more. Of course you can also like, subscribe or comment (or all three) as that helps too! Quint

[@Istandby666]

Hi, I have a crazy idea you maybe interested in. It's an DC axial flux generator. Have the drive shaft as part of the rotor. To see how many watts a drive shaft can produce. Not all drive shafts are created equal...lol Modification maybe possible to a vehicle. Before doing something outrageously stupid. Make sure doing a project like this has a bigger benefit on your side.

[@custardcatcher5195]

exercise bikes dump energy. if they were hooked to generators how much energy would an average person make?

[@garethbaus5471]

I love that you basically reinvented the axe, and demonstrated why they are so good at penetration.

[@halfjack2758]

more of a war pick tbh

[@slavanikulin8069]

Yeah. I’m something of an axe myself

[@garethbaus5471]

@@halfjack2758 The edge geometry is thin and at least 1 bevel has been sharpened so it kinda blurs the line between the two.

[@Leron...]

AHHHHHHH! Quint! I've been complaining about those four random, impossible floating squares from the 7:11 Wolverine escape scene for nearly 15 years now! Thank you for being the first other person I've ever met who was bothered by it before I pointed it out to them!

[@QuintBUILDs]

😁

[@billr3053]

Good catch! Those SFX artists went to CG art school alright but failed basic physics and material science & integrity. Gamers fast-tracked into high-paying jobs. Latte drinking script kiddies. No real world experience. Things just float, dontcha know!!!

[@TCFYTB]

Same, was wondering that for over 5 years now. Fun to find someone else who could see that.

[@JD2jr.]

Easy. center of the door is foam for soundproofing/insulation, and it expanded/"self healed" between swipes. It's a metaphor for Wolvie's situation, honestly. Art.

[@finn8518]

@@billr3053 my god chill out. it‘s an oversight, not some big revelation about the world and the lives of the SFX artists

[@matz4k]

Who else was freaking out when they saw the awesome case? I know Adam Savage would absolutely love it :D

[@DC_DC_DC_DC]

I admit

[@mwilliamshs]

Just a standard industrial case...eBay has them, as does Amazon, SKB, Pelican, Anvil...

[@matz4k]

@@mwilliamshs yep, but having a fitting case with a fitting inlay for you own, custom knife thrower will never not be awesome.

[@quequotion6862]

This weapon just keeps getting better. I really seriously hope they get an offer to license the design to a high-end FPS. I need to fire this at some baddies, and I want every detail.

[@Zeriador]

I do love a nice case with foam fitted spots for things

[@stoffel89]

I like the fact that you use physics in your examples. For kids its awesome, they can actually see what is what. They dont just have equations infront of them.

[@arial_01]

Hey! One reason that your stabbing may have been less than expected is because thats not a very efficient way to stab. Usually, its more of a outwards thrusting motion with the hand in front of the pelvis (this is done while taking a small step forward with your front foot, assuming you are standing in a stranded kickboxing stance. This lets you put your body weight behind the knife.) You can get more power that way! Another thing to note is that it is common to unconsciously limit power in your stab to stop your hand from slipping onto the knife, maybe try one that is meant to be stabbed with and will have a better contour for gripping, or one with a guard for your hand.

[@AdamCeladin]

Throw is still way more powerful than stab ,) proved many times

[@arial_01]

@@AdamCeladin not exactly disputing it, just pointing out how he could improve his technique!

[@AdamCeladin]

@@arial_01 of course and better knife thats for stabbing mainly with better point

[@arcanealchemist3190]

that will increase the amount of force you apply to the stab, yes, but it will be force added over time, not so much to the initial impact force. you're absolutely right about the end result, but it's pretty much the difference between the depth from one stab, and the depth after you take that stabbed knife and drive it in with a hammer. except instead of a hammer, it is your hand/body pushing against the knife after your fleshy bits squish and your bones bend slightly. by the time the push from your hands reaches the knife, the initial impact is over, or nearly over and youre applying a second force. if the question was "how do I improve my stabbing." this comment would be the answer. but the video exists to explain why the stabbing was inferior in the first place, not to optimize stabbing :P

[@user-pw5do6tu7i]

I like the idea that this data could be used in game indie games quiet easily. Instead of a thrown knife doing 20 damage, you calculate the exact penetration depth (assuming you are fighing planks of wood), from there you could use that depth to scale actual damage.

[@AdamCeladin]

Thats totally amazing that you were able to achieve that your machine can throw no spin/Half spin and full spin....Incredible! I would also say deeper knife goes deppends on the weight/shape of a knife (Your seems pretty light maybe 160 grams?) Minimum for good throwing knife would be around 230-250 grams and also skills of a thrower....because power comes for throwers over time its not something you gonna learn in one day and what you created in the end was more concept of War hammer rather than axe and war hammer was known to be able penetrate armor bcs of the high velocity thats focused on very small hardened tip with only one goal to penetrate deep....for example i can throw my knives in to the target so deep that i can walk on them but i am 5 times world champion so not everybody can do the same. Amazing video thank you :)

[@gameeverything816]

You've upped your production values/editing skills. Much more entertaining with the jokey edits. Hilarious and entertaining, as well as informative!

[@afroteddybear]

00:56 That's a Smarter Everyday Baseball ... Cool! Now back to my regulary unscheduled SCIENCE!

[@tmhurley27]

Came here to make this comment.

[@Engineezy]

Amazing video! Great to refresh on some of my old physics knowledge

[@DaimyoD0]

Wow. It's never been more clear why war axes and war hammers are so effective, and why lighter swords are often preferred. Velocity and leverage are often much more valuable than mass. I've always wondered, does momentum factor into penetration depth and terminal ballistics? With a projectile or a stab or a strike with a blunt weapon.

[@bigassasin21]

Quint, I gotta say I love your videos! This video was really well put together! And as I have loved them all this one as by far the best quality I would say. Thanks for exploring the world in a fun and educational way, then documenting it for all of us to watch.

[@robertsmith4681]

Stumbled upon your channel today, gotta admit this is a kind of test I have not seen performed before and it is quite fascinating.

[@nicholascody8168]

You remind me a lot of the KZbin channel civil engineer and you deserve just as many subscribers as them. Keep it up. Love your stuff!

[@mrharvest]

That's some very good sciencing there! I was so surprised of the results

[@benscootin4329]

I haven't been this excited about a revisit since hand-fan. ❤❤❤❤❤

[@Erikve]

Crazy content, I love the combination of physics, mechanics, mathematics, fantasy and real life.

[@aydenberard3416]

Awesome Video! Deserves much more love!

[@Name-js5uq]

The ending was precious. Loved it when your son took off the mask.

[@nonsequitor]

The physics of impact and short duration energy exchange has always done my head in. .. outstanding video 😉

[@ajsilva5939]

Axe type handle + knife = rediscovering the tomahawk

[@theeternalcelebrationpeopl7681]

Brilliant! Absolutely brilliant! 👏

[@joshuagibson2520]

Amazing. Don't ever change my friend.

[@jbrownson]

Excellent video and editing, thanks!

[@robine5280]

That was a pretty damn smooth transition to the sponsor 😂

[@QuintBUILDs]

Why thank you! 😁

[@cods1pe3r]

The making something more flexible also making it stronger point also applies to end mills. When cutting a material with sudden hardness changes HSS end mills can flex instead of shattering, making them better for the application than carbide. This especially applies to cutting something that has one material inserted into another where one of the materials might come loose and move.

[@nedmacallen]

The edit and script are great! Keep it up!

[@viniciusnoyoutube]

Amazing video, great work.

[@BytebroUK]

Good to see you back - it's been a few months. Good vid. (And 'overly refreshed me' really now wants to try 'axe-throwing'!)

[@dennismadderra3916]

Love your Smarter Every Day baseball! Mine sits on my desk at work.

[@babelnumber5]

What fun that family must have. So cool.

[@darrenstettner5381]

Dude! I’ve been throwing since I was a kid and pondered this exact thing for so long.

[@owenkandela3322]

One of those Dad jokes at the end Lol.

[@pepperpeterpiperpickled9805]

excellent video

[@3DIYOriginal]

Awesome 👏🏻👏🏻👏🏻👏🏻

[@VeNoM0619]

Thank you

[@unogazzy84]

AWesome video as usual One tip though. 2:03 Shorten the chain a couple of links. I know that this is not a likely gear to ride with but still. You can see the chain hit the rear derailleur.

[@QuintBUILDs]

Yup, recently bought it used from a friend. Not sure how it got that way.

[@dmsanct]

reminds me of those medieval battle pickaxes. also the headpiece of those had a lot of additional weight so I'm guessing they knew you could mess someone up really bad using that configuiration

[@lilguyfinish]

my man has rediscovered the axe

[@skeleton_craftGaming]

man reinvents the axe... ( I love it)

[@rinokentie8653]

Interesting!

[@limbeboy7]

Haven't watched the full vid but as someone with an engineering background. It has to do with angular momentum. Simply put: angular momentum "multiplies" the force than when moving an object linearly

[@QuintBUILDs]

That's what I thought too!

[@PurpleHaze2k9]

a stab is extended release of energy. Its not all dumped at once. Thrown is dumped all at once.

[@papolele]

Cool

[@de0509]

Knife tonfa seems like a fun weapon

[@LIE4ME]

03:00 Hold up. I throw knives. This may be the most bad ass machine since whatever Egyptians used on the pyramids.

[@tommycrowley382]

Another potential reason the stabs don't go as deep could be the lack of a handstop and ergonomic handle, subconsciously limiting the power you are putting into stab to prevent your hand slipping down onto the blade. Put a rondel handle on that knife and you might go a lot deeper, though wrist strength will still play a role.

[@ajreukgjdi94]

6:20 grimace is absolutely necessary for the science to work

[@UltramaticOrange]

It took me forever to figure it out, but you remind me of the dude who builds the Battlebot, Kraken.

[@afroteddybear]

HEMA youtubers had a minor curfuffle anout the efficiency of over versus underarm in combat. Looking at your leverage analysis, Underarm has an advantage because you move the pivot to your shoulder. That might also be why throwing baseball over hand is slower than underarm softball.

[@justinandrus6731]

Nice flex with the smarter every day baseball

[@wamatt2476]

One reason I can think of is phycological. You can put more power into the throw than the stab because you know that it won't hurt. Kind of like, physically, your jaw is powerful enough to bit off your own finger, but if you try to do it, your mind just won't let you.

[@BeyondOrdinaryTV]

sir you your contents are superb, make videos about electricity generation

[@fizz576]

If I am not mistaken you could have gotten better results stabing the knife into wood if you used a better technique for example it helps to be in a proper stance. Though I should clarify I am not a physics guy I am just going by what I have read in old HEMA manuals.

[@jeffpkamp]

Great video. It is interesting to track down all the places that energy goes other than the obvious ones. You should do a more exhaustive version of Veritasium's "bullet block" video. I've always found his results for that video to be unsatisfactory and likely wrong.

[@ruthlessrubberducky5729]

1:12 Doesn't surprise me you are a fan of Destin's channel. Neat little crossover! You guys could probably make a great collab together!

[@johnniewalker3134]

The slow blade penetrates the shield

[@JamesRockefeller45]

I wonder how this transfers to punching how much does the weight behind a punch matter compared to speed of the punch

[@jossypoo]

Omg i ALWAYS wonder about the 4 hanging pieces when wolverine double cuts stuff.

[@lady_draguliana784]

Wolverine was inspired by Tekko-Kagi. Mounted thrusting weapons like the Tekko-Kagi, Pata, and Katar take vastly better advantage of the mass of the wielder to achieve truly insane results!

[@pharynx007]

oh hey, this video was randomly suggested to me, but you're actually relatively local to me. i've dated a few people from beaverton. (though it is an annoying commute, i hate the 26) very cool video

[@billi5920]

London ppl won't be needing to watch this one 🤣

[@mattmansarizona8868]

7:12 has bothered me since I saw the movie when it first came out... LoL!

[@winstonallen9590]

Very interesting science behind the art of knife throwing. I throw knives on almost a daily basis and one thing I have always wondered is if a no spin throw is more powerful than a half spin or full spin throw. If the knives were thrown at the same velocity in two different ways which one would end up striking the target with more force?

[@QuintBUILDs]

In theory the spinning ones have more energy but as you saw in the experiment, the difference is insignificant. Stability of a spinning knife is much better in my observation but you pay for it with distance sensitivity.

[@iteragami5078]

@@QuintBUILDs I was wondering if having a vertical setup (dropping it down onto the board with spin) would have had the same results as throwing it normally? Or if it wouldn't be a valid comparison.

[@trialspro]

I think youtube must have shadow banned this, possibly for making a "weapon". I realized I hadn't seen a video lately and had to search to find this (I'm a long time sub). Normally your videos are suggested for me. 2.9 million views first video to 23k views for your second and 17k for your third... something's fishy with the algorithm

[@LostSoulSilver]

Where can i buy your knife axe?

[@apathyreview3964]

So tomahawk 's? I shall await the video :)

[@fordfuzzyface7268]

Flexing material is good for bows...wonder how it companies to other bow materials.

[@brandonsharp9158]

I wonder if the wood backboard could provide inconsistency in the data? I imagine a knot in the wood would reduce the depth of the knife cut vs a softer spot assuming the same knife speed. Thanks for the great content! I love the experiment!

[@amosbackstrom5366]

That's why he has an entire board filled with data points 👉

[@granthaggard4658]

I’d love to see the error propagated with error bars shown on the graphs to give a better sense of the data’s significance.

[@SynthRockViking]

My personal opinion, is throwing knives are only useful for distracting/pissing off your intended target 😅

[@vittocrazi]

Well... Your personal opinión IS most likely mistaken. Look Up how Deep of a wound os needed to be Life threatening. And if It cuts wood, If It hits you hip, collarbone, ribs It may be crippling on pain alone. And on the skull It may be Life threatening even if It doesnt reach the brain directly. Truth IS ALL puncture wounds are very, very dangerous.

[@CDizzzle4Rizzle]

The lower the delta t the more force at impact.

[@mathewbriggs6667]

if you stab a lot of the energy gose into the none ridged structure known as your body the knife when thrown has no soft part to store all that energy that and its as simple as force over time wen you throw something its going way faster then when you just put your body weight into it try holding the knife ducktape it to your hand then stiff arm and run at the board you will go way deeper

[@wombatillo]

Durable is actually a little too wobbly for that. Tough 2000 or even Tough 1500 would have been much closer to a proper plastic axe handle.

[@werewolf74]

Before the reveal my guess is much of that energy is returned or absorbed by your body? Where as the throw, 100% of the energy goes in...? Ok so this is why fails are scary.

[@DannySullivanMusic]

From now on I will only cut my food by throwing knives at it

[@FlesHBoX]

I feel like after watching this I'm on some list now...

[@QuintBUILDs]

ROFL! 😂

[@samuelhart9087]

You made a hatchet.

[@BoatNectar]

Are you okay Quint

[@lightdark00]

This could have been a short, "Let's look at the equations, ooh velocity is squared..."

[@QuintBUILDs]

But so is omega for rotational...

[@listofromantics]

Perhaps... but where's the fun in that??? In addition, while some people can look at an equation and immediately intuit a cause or result, others watching these videos need concrete demonstrations / proofs to grasp the subject matter.

[@leviathan1082]

The 4 cut out squares in. The center forgot to physics 🙃 0:32

[@qwertyTRiG]

Face reveal, but no eye reveal. Seriously, that's an impressive fringe!

[@ahather]

now to adapt the throwing machine to axes?!

[@mathewbriggs6667]

lol man discovers hatchet

[@jgbizarro2726]

Looks like a Chinese dagger axe

[@jedhead5079]

You literallt made a gun that nullified learning to throw knives WOW

[@joemitz5913]

Just for the algorithm

[@rogeriocosta1035]

Missed the opportunity to use a human gelatin model to measure the velocity/energy needed to throw a knife to penetrate a human chest. You could show that kill someone throwing a knife is almost impossible.

[@AdamCeladin]

Not true its actually way more possible then you think ,)

[@risunokairu]

Ah, yes, the Knammerf

[@QuintBUILDs]

😂

[@alisterdcruz1667]

Does this mean throwing knives at people is more effective than stabbing them?

[@AlexanderZapataIndividual]

The image of wolverine cutting an x trough steel leaves squares suspended on air. Within the intersection of the blades. It dont makes no sense.

[@thepragmatist4607]

Anyone else still not get it? Its not at all obvious to me why 2 objects of identical energy and cross section (just one is heavier and slower, and one is faster and lighter) Would penetrate to different depths. Or is this not even what he is saying? I wish he used weighted knives in addition to a levered knife. It might have made more sense to me.

[@Razornuke]

Didn't you basically just make a war pick?

[@waitemc]

Oj Simpson we know your in the comment section

[@QuintBUILDs]

😂

[@longgowhereto]

No idea how I found this channel, but I am amazed! I am from a country with open borders and a lot of never had before knife crime. So I said to my girl, wether we leave our country or I get myself two Franziskas (no guns allowed there). I am at 8:02 and you will show me now, if I talked crap - I am extremely exited! Thank you! (btw we left)

[@seancoyote]

Now figure out if Nunchaku equals a stick or the stick is better.

[@twosquids]

There was so much in this video you could have clickbaited

[@QuintBUILDs]

Any favorites?

[@twosquids]

@@QuintBUILDs "perfectly straight knife throw?!? - knife throwing machine part 3"

[@jakesmerth1919]

Are we all going to pretend adding the handle to the knife didn't add levers? His elbow and wrist become the same levers they were when he threw a knife. All his data there is read wrong.

[@Alex-ph1th]

😆 "promo sm"