Supersonic Darts - The Effects of Inducing SPIN - I learned something!

I carefully modified a couple Anferov Bullets to see if we could actually induce a spin on the just from the airflow over them- without rifling. We also try to determine if a fin-stabilized projectile can benefit from spin-stabilization.
While we didn't SEE an improvement in stability, there can be OTHER benefits that we haven't given much thought before now.
OG's own KZbin Channel:
/ tahow7798

[@SoddingGit]

"Using high tech sorcery" - I love living in these futuristic times😄

[@blvp2145]

Any sufficiently advanced technology is indistinguishable from magic. -Arthur C. Clarke

[@dyl7769]

Exacto knives these days are futuristic. WW3 joke btw

[@SaganTheKhajiit]

My favorite kind of sorcery

[@ashleyking8851]

I'm so shocked these gunmen also know warlock magic

[@WapTek123]

to make it spin without bending the fins chop the trailing edge dual bevel to a single as in from this /\ to this |\ or /|

[@tony66au]

A lot to be said about Keeping it simple with as little complication as possible and the OG Anferov illustrates this nicely by virtue of its efficacy in tests. Shout out to Officer Gregg for supplying the long tubes of KY for the drop test ;-)

[@therogers4432]

I think they were left over from the rider that one of his Country/Funk/Disco/Rock-bands from the '80s demanded to appear at a certain venue, along with 20,000 yellow peanut M&Ms and a gallon of Drambuie...

[@USMCOrdy6541]

"Not to be confused with this type of Fin." - I got a hefty chuckle out of that one!

[@st3v3h4py]

I'm seeing a meme of "straight Finns vs not-so-straight Finns"

[@KOZMOuvBORG]

Thought they'd use the Beyond the Press couple as an example of straight Finns.

[@mattfleming86]

Perkele!!

[@Tunkkis]

@@st3v3h4py "Not so straight Finns" are called swedish-speaking Finns.

[@brianstearns3692]

@@Tunkkis Man I would hate to be Finnish and have someone use my likeness to demonstrate a "Not so straight Finn"

[@shmuckling]

I've found that too much spin can actually make slight imperfections in the projectile manifest as worse stability and accuracy than if there was less spin. That said, a well constructed projectile, with minimal surface imperfections and good source of drag at the back end will generally benefit from a little spin. Also, it is often the case that even unnoticeable surface imperfections will induce a slight rotation on a moving projectile without having been designed to do so, and that little bit of rotation is often enough to stabilize the projectile in flight.

[@sierraecho884]

I absolutely agree with you.

[@warrenpuckett4203]

kzbin.info/www/bejne/oonIqnibjbhgmck check out what happens at the rear 3:35 on 4:00 a F-22. It has a computer controlled actuator for stable flight control. Be kinda hard to shrink for a shotgun projo.

[@ThatOneGuyEmblem]

if there is anyone in this comment section that plays Disc Golf, they, as well as myself, know exactly what you mean. any imperfection in the disc, both visible and non-visible, have a HUGE impact on the performance of said disc, whether for better or for worse, lol.

[@ferret_max7800]

You highlighted what I tried to say in my comment much better, thx

[@santyclause8034]

Centerline has to be true or your have an unbalanced journal effect. Roundness also has to be pretty good. One point this video upload didn't touch upon is how the balance of the projectile affects its stability in flight. These points made concerning roundness and centerline regard projectile spin, they will affect it. Lengthwise the projectile balance point also has to be Forward-of-Center (FOC in archery) so the point -or head if you like- leads the tail in flight, and vanes stabilise tail swing so your dart will 'fly true' and strike hard. If you do not make total-dart-mass balance upon a point some percent forward of the mid-length, the projectile will tumble. Which means whether the head strikes the target point first, or does not, is only a gamble. It also means all the kinetic energy will not be transferred into an impact force directly behind the tip.

[@Jonoman777]

I agree with the idea that if it's already stable it's just gonna be hard to improve on that. but I think if the bent fins were to work I'd imagine they'd have to be extremely precise and consistent.

[@mk6315]

I’m gonna nerd out for a second. I think you need the whole fin to be angled, like how a supersonic fighter jet’s elevators do. possibly due to the shock cone not letting enough air pass over a small angled fin?

[@mk6315]

Also I wonder if the obturation ring is causing a vortex to extend out over the majority of the fin like a kFm airfoil?

[@Jonoman777]

@@mk6315 you're probably right. I mean traditional slugs have straight cut "fins"

[@dj1NM3]

@4:19 I'm more amazed that just canting part of the fins actually imparts spin when falling through the water and it went straight, instead of angling off slightly like the unmodified one. ...but whether that really translates to more stability in flight? ¯\_ (ツ)_/¯ I would hazard a cautious guess that the variable of sabot separation might have more effect than spin, on accuracy.

[@VanderNugget]

I’d be interested to see the water tank drop comparison if the tanks were 30 feet deep (or whatever). Over that distance the effect might be more obvious one way or the other.

[@-BigTMoney-]

That canting can be caused by the bullet not being dropped as straight when it entered the water, or dude not dropping from the center of the top

[@Archimedes.5000]

Spin reduces effect of poor separation on accuracy

[@michellewilt4479]

Very interesting test that I would love to see repeated with the 40 degree and various other angles vs the straight finned projectiles. That being said, I know these rounds are hard to come by right now and I hope that very soon they will be quite plentiful for you to test with again.

[@bobbybritt1797]

Depends on the range also, because if it rips a gut, then what range to be at to make it vicious?

[@ronniepirtlejr2606]

I say try with less of an angle on the fin.... say half of what you have now? Or Maybe try multiple shots & each one with a different amount of tail fin angle? Who knows? Maybe a certain degree of angel will make it work better than all of the rest? Although the straight fins shoot fantastic!

[@dibingsdibingens8463]

Im here now since the channel had around 10.000 subs, and over all these years you guys constantly manage to deliver totally top-tier content, and even the comment-section is a uniquely-wholesome and peaceful place filled with lots and lots of decent nice people from all over the world. Big thanks to all of you, stay safe and have a nice day 👍

[@jordanhorst6]

The angled fins might also work better with a different ratio of fin size and angle to projectile mass. A shallower angle may impart a more gradual spin or perhaps the 40 degree angle would work better on a heavier projectile etc. Of course it may end up being the opposite 😉.

[@dotar9586]

YES! Exactly! Put the fins in front. That's what you meant, right? 🤪

[@jordanhorst6]

@@dotar9586 what?

[@-JohnSmith-]

Rotating objects are stable but that's when the whole thing is spun, when that force is being imparted on an unbalanced part you get the wobbles.

[@Sableagle]

@@-JohnSmith- In that case you want to get in touch with Fireball Tool and get some 0.3" steel rod with a spiral cut at 1 turn in 1.123 inches for that same 40° angle inside 0.4" steel sleeves with a 0.05" thickness, so instead of fins you have air channels through the full length of the bullet. It might also be interesting to have two sets of them, one solid all the way through inside and one with 0.2" holes drilled centrally up the back of the core to half the length, or multiple sets with multiple tail hole depths, to see how the shift in centre of mass affects behaviour.

[@timothyprice9064]

That's why somebody gets to test it.

[@carlbrown8830]

Jeff, Your camera work is why I love to watch your channel, and OG is the icing on the cake! For centuries, native Americans have been constructing arrows with a twist in their fletching. They knew about ballistics long before the invention of gunpowder.

[@andrewdobosz3682]

Just wanted to say, been a fan for a long time. Great content as usual. All ways entertaining and educational in a non bs way that i appreciate. Thank you Jeff, OG Danny forever 🙏

[@taofledermaus]

thanks Andrew

[@RichardCranium321]

I miss Danny... 😢

[@Glasher1]

@@taofledermaus I wasn't surprised at all that the first spin stabilized dart's flight was erratic, if that was the dart shown at 1:13 with the drawn lines on the fins, because the fin angles (imo) were not symmetrical.

[@regsparkes6507]

I was listening intently,. and then I thought, Jeff would be a pretty good teacher. He does explain things pretty thoroughly.

[@davidjernigan8161]

Perhaps too much angle on the fins. It would most likely require a new tail section in order to put a minimum angle of 3-5 degrees on the entire fin which would probably work better. A true test would require longer range shooting with 3 or more rounds of each configuration which you probably can't get enough projectiles and sabots to do.

[@haydenc2742]

Yeah...lob em out 50-100 yards to see if it helps farther out

[@Eatherbreather]

Exactly what I was thinking - also if the entire fin was curved/angled rather than straight with a bend as this should prevent shock waves forming where the bend is made? Supersonic aircraft have "all flying" tail surfaces to prevent shock waves forming where the control surface hinges would be otherwise.

[@craigwilliams9154]

@@Eatherbreather I'm guessing that the sharply angled fins might be producing turbulent air flow near the kinks. I wonder how a gradually curved fin, and at reduced angle angle (as suggested by David Jennings above) might improve rotational rate and accuracy.. As a side note, spin stabilization is frequently used in sounding rockets at average out payload trajectories. Of course, the aerodynamics become weirder as your test objects shrink so the comparison isn't 100%

[@abhijeetsutar5259]

@@Eatherbreather Any deflection in a supersonic flow results in a shock-wave. Even for a "all flying tail surface" will generate a shock-wave at both its leading and trailing edges albeit on opposite sides of the airfoil. The same applies to the continuously curved fin. In this case the leading edge will shock the airflow into subsonic speeds over the concave side of the fin, while the convex side will have gentle expansion waves that actually accelerate the airflow but will generate a shock wave at the trailing edge to shock it to the same speed and direction as the overall airflow. The purpose of having an all flying tail is to provide the pilot greater control authority over the plane.

[@Eatherbreather]

@@abhijeetsutar5259 you're entirely correct! I completely forgot about the l.e and t.e shock waves 🤦‍♂️

[@headcheesefry]

The fins only hit the air when the projectile is not straight so there isn't any extra drag when supersonic, just the minimum necessary to stay in line. The angled fins will push the tail of the round in a direction that is not toward the centerline and make it unpredictable because it isn't a constant force. Love your channel, found you years ago when my kid wanted a hex bug for Christmas and I didn't know what the heck it was. Keep up the good work.

[@NoGoodNamesLeft]

Oh hell yeah more awesomeness from this kickass channel!

[@taofledermaus]

thank you!

[@pantherplatform]

It's the people that _don't_ comment. That's what makes this channel Great.

[@kimgriffith1054]

Thank you very much for allowing us to tag along for the testing. It was interesting. I don't feel spinning a stabilized projectile will assist much. That said, you don't know until you test. Stay well and best to the crew.

[@mikeks8181]

There is a science/ math to Make any round More Stable While Spinning! That's why we just let the Manufacturer do it. A Great intro for handloaders to see how to start! Thanks again for another Wonderful Video!

[@ianchastain3920]

Love how you explain everything watched you for a long time and always learn something new..

[@taofledermaus]

thanks Ian

[@harlech2]

"Just be glad it's in English..." OG, I swear to God, you would be the only cop that could write me a ticket and have me howling with laughter.

[@jackwarneckii4406]

I love the behind-the-camera banter between you and OG. The "interruptions" are just part of the fun.

[@markbreidenbaugh6033]

Fin stabilized sabo rounds that are shot from smooth bore tank canons are also strait finned and some are going over 5000fps.

[@markfergerson2145]

Not all are straight finned. The US is going to slightly canted fins for better stability and accuracy.

[@Falconguygaming]

@@markfergerson2145 roughly 1/2 a degree, per The Chieftain

[@kj3n569]

Tanks are the exception to the rule. Any rule. Because nothing can tell an American Main Battle Tank what to do. They are the Chuck Norris of vehicles. Carry on.

[@markfergerson2145]

@@Falconguygaming Yep, and he should know.

[@ninjax4909]

Tank APFSDS rounds ALL spin. Their fins are straight but not in line with the projectile, the entire fins are very slightly rotated to one side. Roughly half a degree, generally to give the projectile just enough spin to be more accurate than no spin, while not having any of the disadvantages of high spin.

[@BenjySparky]

Jeff and OG y'all rock! Love the channel and content! I'm here for the algorithm! Peace

[@johnharder5618]

I like your videos As I sometimes hunt White Tail deer with a shotgun here in NW Ohio ( I prefer to bow hunt or use a handgun ) I sometimes need to harvest a deer at 100+ yards to help control White Tail Doe numbers to help with crop damage I feel that a projectile that is getting added spin from the fins can be a good thing Because as the projectile flies down range the air drag slows it down So as it slows down straight fins will impart less stabilizing effect So to help stabilize the projectile the bent fins will impart a rotational stabilizing force even as the slug slows down I feel the straight fins will greatly loose the stabilizing effect as the slug goes sub sonic

[@Jay-mv7xv]

We love you Jeff! Thanks for the interesting content! Hi to OG, too!

[@Cheveyo888]

Seeing that spin rate made me wonder how a heavy, sharp, screw would perform with similar fins if properly weighted.

[@v.Hohenheim]

On a fast moving screw stabilized by fins you would get no spin from the screws thread. The airflow would be moving over the thread and not spiraling through it. What the thread would most likely would do is disturp the airflow around the screw. That would make the airflow reaching the fins turbulent and therefore make them less effective.

[@Cheveyo888]

@@v.Hohenheim aye, I was thinking more in terms of the threads effects on target. Didn't consider the added turbulence though

[@volentimeh]

@@Cheveyo888 There are some nails that have a square profile and a gentle twist to them (for better grip) that may be more suitable than the close spacing on even a coarse screw thread.

[@andyreid7274]

My favorite mass accelerator channel on youtube

[@danishpuma]

If spin had any advantage in finned projectiles, you can be 100 percent sure they would do it on tank rounds but they don't.

[@Tuluet]

But they do You can clearly see that the projectile winds up spinning speed as it moves trough the air. kzbin.info/www/bejne/fqaaaqZ7dpqLa6s

[@Okararu]

imo i think it actually makes it worse. The fins already make the projectile extremly stable and no finned projectiles use curved fins. Arrows have straight fins, tank apfsds rounds have straight fins, rockets have straight fins. Spinning projectiles without fins are more stable than those who dont spin because of gyroscopic effects, but spinning fins would just ad more drag and therefor worsen the performance. Especially since the fins actually normaly prevent those projectiles from spinning. Thats what i think at least.

[@pierre-henrivince4591]

@@Okararu They actually do angle the fins on APFSDS projectiles at about 0.5° (so almost nothing at all) but even this slight angle helps it spin a slight bit and this stabilizes the round that extra little bit.

[@Okararu]

@@pierre-henrivince4591 have you got a source for this? I can't find anything online.

[@jonathonspears7736]

British Challenger tanks actually have anti-rotation sabots for their APFSDS as the spin reduces the accuracy on modern ammunition which is 1 reason nearly all MBTs have smooth bore cannons now.

[@lawrenwimberly7311]

I love your hands on scientific approach to these ridiculous rounds

[@Horus2Osiris]

We use a 5° helical fletching on our hunting arrows, traveling ~300 ft/sec... not 40° traveling at 1400 ft/s... too much power!

[@JamesSmullins]

I was thinking the same. 3-5° is all that's needed but I noticed something else as well. Our fletches are angled the entire length but for these they only bend the ends. They basically created two opposing forces and that's not good. It also would have been better to have the angle match the rotation of the rifling of the barrel because that induced a third opposing force that had to be overcome. Most archers know to match heliocoil with arrows rotation based on how the string is twisted, same would apply using rifling as the start point for determining angle.

[@bobbybritt1797]

It'll rip the target at alil closer range, depends on the range

[@andresmonagas7662]

That right, I'm just wondering if ~5 degree angle will be enough considering that is traveling at a supersonic speed and the fletching is probably behind the supersonic shockwave

[@metamorphicorder]

@@JamesSmullins they werent shooting them out of a rifled barrel. He specifically mentions that at least once and in a on screen text he mentions that he meant for them to spin backward so no one could say he just used a rifled barrel.

[@JamesSmullins]

@@metamorphicorder he said he bent them in the opposite direction of the rifling so people couldn't say they were cheating.

[@TimberwolfCY]

Fascinating. Absolutely fascinating. I suspect any accuracy increase/decrease will be more pronounced farther out. For projectiles that large, that fast, being already so stable, I'd imagine nothing less than 30 or 40 yards will demonstrate much difference. Here the uniformity of the fin angle will be key IMO. The water test was an ingeniously simple pre-test and I really enjoyed seeing that. I do hope you make some follow up videos; seeing the corkscrewing air *behind* the one angled-fin bullet/dart was particularly visually satisfying. Thank you!

[@Dean-zx6nx]

The “angle” in that orientation could cause the wobble, What about like a 3 degree offset, like arrow fletching?

[@nateb4543]

Ya i was thinking that with a sub 300fps(barely) arrow, the difference between 3° and 2° is noticable. 1000fps seems like a half degree should be plenty. Granted the surface area is smaller

[@ifv2089]

Yeah I'm thinking this is just like adjusting the Helicoil or straight vanes when I'm tuning in the mathews monster compound arrows.

[@joearledge1]

Might be something worth experexperimenting with especially with precision at longer ranges. The logic is sound, many fin stabilized projectiles have some degree of spin imparted by the fine (arrows for hunting or competition like ya'll pointed out and I'm fairly certain some munitions do too) I'm sure there's a "sweet spot" for the angle of the fins for a given projectile for a given velocity. But like you said, I believe that the ideal angle is much closer to 0 degrees ( like the 0.5 you mentioned). I'm sure there's some sort of physics/ engineering equation for this that would help narrow your experimental range of angles and velocities.

[@Seelenschmiede]

Spin for arrows is used to negate the archers paradox where the long and thin arrow shaft wobbles through the air

[@ifv2089]

@@joearledge1 there is some tuning involved but I find a well made Helicoil arrow works well and have noticed preformed well outside over straight

[@MikePuorro]

Forgotten weapons - That guy is a legend

[@illagevidiot8254]

Its funny that you jumped into machining defects because I was thinking exactly the same thing after the first shot went soo poorly and the rest didn't. I think thats the more likely culprit than anything when it comes to the major wobble it has. I don't know how you bent it, but it could be caused by an inaccuracy in the bend itself. I dunno, I'm not a ballistics expert.

[@Keldor314]

Not just the aerodynamics of the bend, but also the way the bullet is seated in the casing. I have the feeling that these sorts of bends are just asking for defect related inconsistancy in flight.

[@illagevidiot8254]

@@Keldor314 Yeah, in all fairness, the bend itself isn't representative of what proper spin stablizing fins usually are. Generally the fin as a whole is angled rather than the bottom portion of it being bent, In my uneducated opinion, having the drag coefficient spread out over a longer distance would create a more stable flight than what was done to these rounds. If you picture drag as a force being applied to a nose heavy object travelling at speed, the benefit to having a nose heavy object would be detrimented by the bend due to it being isolated at the far opposite side of the object. In effect, I think it would act more as a lever in a way, which would be amplified by any discrepancy in the bend itself. This could be as simple as the composition of the material (i.e. the crystalline structure of metal) creating a different curve in each bend, even if the bend itself was created in the same location, and at the same angle. Whether or not having the fins angled as a whole wouldn't create similar effects is beyond my ability to picture these things in my head though. I'm willing to bet that these rounds would be far more stable, but I have some doubts over whether or not they would be even better off than they were before modification.

[@enolwlfe]

💪👍 another awesome show fella's as always. the round your shooting ROCKS! I'd buy a box or 2 for my arsenal that's for sure.

[@blvp2145]

OG is the science. He wears a white lab coat and I just know I need to trust him.

[@imperfectlump6070]

he is the "science".

[@BeingFireRetardant]

@No Touchy Same goal, different approach. Simply comes from being a Task Force 69 veteran...

[@itsjustjoe3790]

Your high tech sorcery visuals are actually very cool. Thanks for another educational video.

[@lonewolf8820]

Aerodynamics change dramatically at supersonic speeds and the angled fins may increase the coefficient of drag and change the balance of the bullet. This would mean as speed is increased on the bullet, slight variations in how it travels through the air would be magnified. Because of all these factors, I really dont think it needs angles on the fins.

[@supercjs6044]

Not that I'm exactly an expert on this by any means but as far as I'm aware the angles on fast moving projectiles when it comes to fins tend to be very small, having heavily angled fins, even like the ones in the video would come as a detriment more than anything else. Plus when it comes to spin stabilised projectiles that are actually in use they are considerably more well designed over all. (I'd also guess the design of the projectile its self has a lot to do with whether spin stabilisation is a requirement or whether it would even be of use.)

[@Stacy_Smith]

@@supercjs6044 I'm not an "expert" per say, either, but at 46yo I've had a tire or 2 balanced in my life. So I would have to agree that by putting spin on a fin stabilized projectile you're doing more harm than good.

[@supercjs6044]

@@Stacy_Smith As far as im aware a large part of whether its even worth it to begin with is the design of the round you're firing. Imparting spin on a round designed to go without for instance won't do much to help, among a million other factors.

[@Eatherbreather]

I liked the water drop test. I expect the bent fin sample would reach terminal velocity sooner than the straight fin sample - given a long enough column of water to fall through. Bent fins should mean more drag/less range in exchange for improved stability, in theory. I don't think spin is needed on these slugs. Excellent video as always 😊

[@jcims]

The problem with inducing spin after the projectile leaves the barrel is that it will introduce gyroscopic precession early in the flight. This will create a force perpindicular to the axis of rotation and cause *exactly* the type of instability you see in the first shot. This doesn't happen inside the barrel of course because the bullet is basically swaged into the rifling and has no ability to rotate on any axis but the one of the barrel. Over time as the spin rate increases this will get damped out. My guess is that straight fin stabilized is probably more accurate at short range and the spin+fin stabilized might be accurate over very long ranges (where the spin can pick up after the round slows down and the control authority of the fins begins to decrease). One potentially interesting experiment would be to place the fins at the center of gravity of the projectile.

[@adabsurdum5905]

I believe that spin stabilization through angled fins is only realistic if it's machined. Any tiny inconsistencies between the fins would result in asymmetrical spin, which would make it a lot less accurate.

[@scrubsrc4084]

Theres so many varieties of curve to add to the fins, angled fins. Bent fins curved fins and they all impart different behaviour. Really interesting aerodynamic study.

[@joeisslow1638]

I would bet that having the exact same angle on each fin would affect accuracy. 40° angle was too much as well, the high rotational rate pushes the center of gravity too far forward and the drag from the fins isn't enough keep the front of the projectile stable. Maybe a 7-10° angle on the fins would still impart rotation, but not so much that it causes the front of the projectile to wobble. I like these rounds and I think if a company made them with higher precision machining (so the fins were exactly the same) no angle fins or spin woukd be needed.

[@thomasburleson9575]

fins put drag at the rear of a projectile and cause the Center of Pressure (CoP) due to drag to be behind the Center of Gravity (CoG). This gives stability to the flight. The high angle of the bend on the fins MAY force the CoP slightly forward but not the CoG. This would mean less distance between the CoG and the CoP thus the projectile would be less stable. Another, more likely, cause would be a slight difference between the bend angle on the four fins. This would move the CoP away from the centerline of the projectile and give a wobble to the tail.

[@joeisslow1638]

@@thomasburleson9575 yes, we are essentially saying the same thing. The high angle of the fins cause the wobble, and the varying fin angle will affect the overall accuracy. I didn't figure the CoP would effect much since all of the directional force is applied while the projectile is still saboted and in the barrel. I suppose that's why it's easier to leave the fins straight for minimum CoP instead of adding more weight to the front to move the CoG away from the CoP. Also if the fins were straight, but with a low angle, axial tilt along the whole fin as opposed to a sharp bend on the outer edge of the fin, the CoP would be more symmetrical and stable.

[@clarkrush5176]

Buck Rogers sure would be proud ! Much Love Guys

[@mikemitchell9157]

Fetchings on arrows usually do have some sort of helical put on them. Usually at most 3⁰-4⁰ at most. Edit. 40⁰ seems extremely excessive

[@lukebaker1167]

Depending on the length of the vane, the angle increases with the length of the flight vane

[@mikemitchell9157]

@@lukebaker1167 know but just keeping it simple bro

[@lukebaker1167]

@@mikemitchell9157 2 ezy Mike!!!

[@bozerliberty]

Hahaha... just love seeing the flight of these darts heading to the target... Thanks Jeff and OG

[@kmorris180]

I was wondering about the projectile you showed at the beginning. I looked at the fins and thought it would throw it out of stability due to the fins being at different angles. What are your thoughts on it?

[@notyou1760]

The most appropriate video genre for a Morrissey reference.

[@sacrificialrubber779]

Answered my question about airflow over the fins…😮 Maybe less fin angle? I’m very curious about this…Fascinating!

[@ifv2089]

Its always been a question with Archery to Helicoil or go straight vanes, tuned correctly. Not the same speeds at all but a Helicoil can help the arrow leave the shelf cleaner and recover slightly quicker than straight vanes. Traveling these speeds it is very intresting.

[@Shaylok]

Now this is an idea worth R&D. Lots of potential here.

[@alexduke5402]

My theory is with the super Sonic shockwave will not allow it to spin until subsonic. I'll check back in a few and see how close i am

[@leifvejby8023]

I was wrong and you were wrong Have a nice day

[@alexduke5402]

@@leifvejby8023 yeah it's not the first time and damn sure won't be the last hahaha

[@leifvejby8023]

@@alexduke5402 Same here

[@gamecubekingdevon3]

it is worth noting that it's the same on most main battle tanks from the 60s up to today (soviet T-62, T64, T-72s, etc... american abrams, german leopard 2, french leclerc, japanese type 10, etc...) and said MBTs are cappable, with a smoothbore gun and this kind of design of projectile, to score a hit on the moove at distances above 1km (and for more modern ones longuer than that, to such a point that the penetration data of most kinetic projectiles for today's tank is counted at 2000m of distance)

[@urishima]

I think I remember The Chieftain saying in a Q&A that APDSFS rounds actually do have slightly angled fins. If I am indeed remembering that correctly, then finding the right angle probably involved millions of dollar of RnD funds alone.

[@SuperBadVideos]

As always awesome video, the best part was the high quality graphics at the end lol 😂👍🏻🔥🤘🏻

[@alisahutako4518]

This is really interesting and really reminds me of something about old crossbows~ did you know that crossbow bolts have an angle on their fletchings to spin the bolt to improve accuracy~? I didn't know that either until several months ago when I was watching Tod's workshop~ in one of his videos he said that people in the past actually did this because it simply improves accuracy~ you guys should check that out and I will try to find the video to link it~

[@frankhinkle5772]

I like watching scientific testing! OG had on his white lab coat, so this must be scientific! Really, the production value is very high. Great photography and explanation. Thanks.

[@mperdue73]

Coming from the archery world, I can tell you that it is a thing to fletch arrows with helical feather. As with everything, you have people say it doesn't affect flight and ones that say it makes them more accurate. I was always in the helical camp.

[@zwenkwiel816]

where you gonna find a helical bird though? :p

[@PaulSteMarie]

My recollection of the physics involved is that spin stabilizes flight for a while, but eventually any precession will flip the body from spinning mostly axially to mostly end-over-end. IIRC, spin works best for short squat bodies, like frisbees, and fin stabilization works best on long skinny bodies, like arrows. If you're really interested, the book "Topics in Advanced Model Rocketry" from MIT Press/NAR goes through the diff eqs in excruciating detail.

[@malcolm_in_the_middle]

I do archery, and a lot of archers bend their fletching to impart spin. The main reason is that it gives the arrow resilience against crosswinds, rather than actually making fly better in normal conditions. I'd imagine it's similar in this case.

[@Darthdoodoo]

Good thinking

[@Darthdoodoo]

How are duey and reese?

[@Stacy_Smith]

I like the way you and OG troll the trollers. It definitely adds some comic relief to your videos.

[@drew79s]

The "Diabolo" shape that you're looking at is a drag stabilised projectile. The feature that defines a drag stabilised projectile is that the centre of mass is in front of the centre of pressure. That's why the base is hollow, to move the centre of mass forward. This is the same as Foster slugs... If you're bored enough, a conventional ogive projectile is actually stable in flight if loaded backwards... Fin stabilised projectiles don't use drag in quite the same way, but as you've suggested at the end the benefit is averaging error. The risk is that the fin stabilised projectile can be overspun which results in the flight issues that you've had in your example. Normally fin stabilised projectiles are spun something more like 20-30krpm as opposed to something closer to 3 million RPM for a rifle round. If you want a laugh for a follow up to this one, try a couple of degrees of angle in spin and have a look at the flight over a few hundred meters if you have the space. You could also put something more like that 20 degree angle onto opposing fins in the same direction... This should result in the projectile yawing in one direction. Simliarly if you're bored sabot separation is a really interesting space to look into. Usually it's important to ensure that the sabot doesn't touch the fins, as it results in a destabilisation effect on the initial flight of the projectile. The initial touch can have a significant impact on the flight accuracy. You might find that videoing the sabot separation could result in some interesting effects :)

[@hernerweisenberg7052]

If a diabolo is drag stabilized, then why do pretty much all airguns have rifling? Isnt that hollow skirt there for the same reason a miniball has a hollow skirt, to expand into the rifling? If you look at a used diabolo, you can see that the skirt has the most, sometimes the only rifling imprint.

[@chrisburnsed6349]

Windbag. And also wrong in most of your comment.

[@taofledermaus]

That isn't quite true because we can and have shot SOLID diabolo slugs without a hollow cavity and have achieved stability- many times. The hollow is actually there to act like a Minie ball and cause the pellet to obturate and seal the gases.

[@drew79s]

@@taofledermaus I just tracked down and watched the video... that was interesting :) I would assume that it's because the rear cone moves the centre of pressure rearward as well. In your video it looked like a couple of the shots were oscilating a little as well as the one that wasn't stable, but the rearward shot definitely inverted, so the centre of drag was definitely in front of the centre of mass. On an airgun the skirt definitely obturates as well, but a good design as one that does as much as possible with the same features :) It's also worth noting that, in your other video, the slugs were fired out of a smoothbore, same as this one and they don't have fins, so the flight has to be drag stabilised in this case ;)

[@TheDuckumz]

Guy looked like he just realized he shit himself when Ian asked him that question 🤣

[@mfree80286]

Paused at 4:54 ; the problem with spinning a fin stabilized projectile is there are parameters where the spin creates a positive feedback with regards to yaw... either great amounts of yaw or fast spinning will result in the advancing fin having much more effect on the projectile than the retreating one. Since this is off the axis of rotation, what you get is an increasing conical gyration, eventually ending up with the projectile twirling around sideways. This is why the model rocketry people try *extremely* hard to get their fins equalized and straight enough for no roll. Weathercocking (the nose pointing towards a disturbance to the flight path) is what's wanted, with good damping (no extreme motions, so no overcorrection/backcorrection wobbles). Spinning just introduces unequal off-axis forces that makes it much less predictable in response to a disturbance like a wind gust. If a coupled (spinning/finned) rocket is still stabilized and damps out, it could do so in any direction and not aligned with the initial flight path.

[@666Blaine]

I thought that weathercocking only happens because of the rocket's thrust.

[@mfree80286]

@@666Blaine Technically yes, but an unpowered projectile can do it too depending on it's overall stability, damping, and profile. It eats a lot of energy though.

[@raystarky3896]

Yes! Great video I love it! and a GREAT deal to learn here; 1st thing to notice is the very BLUNT nose on the TWIST projectile and just very simply it should have a SHARPER nose such as the ones that are rifle bullets SO::::::::::> I believe by giving that bent fin projectile a ROCKET NOSE would/should stop the tumbling/flubbing in the air before the point of contact/impact. SO why do rifle bullets have a curtain twist is because::::::::::> they are supposed to be more accurate and deliver great power/impact, but the rifle bullet does not stop there it also needs to have a boat tail, because it does not have fins to further stablize itself.

[@sunshadow7XK]

The grooves in the projectile have multiple functions: They grip onto the sabot, and also cause the airflow to "grip" onto the slug as it travels through the air.

[@ruandurand3971]

It helps to pull the seperated flow closer to the centerline axis of the projectile by creating low pressure cavity flow. This is why the fins have airflow over them. Having a smooth surface would most likely result in flow seperation over the leading edge shoulder and then miss the fins completely.

[@TheMemosteve]

Almost spit out my Red Bull with the " How Soon Is Now?" Karaoke bit...

[@pastorlarry7470]

I pastor a church in South GA and the other day for Ash Wednesday this lady had put some fake grapes on the communion table. They were made out of blown glass. As the praise band is singing I am looking at those glass grapes thinking to myself what would happen if you shot them out of ashotgun 😂🤣😂😳😇 The glass grapes in question are around 100 years old 😳

[@OGsDangerShow]

Ship them over and we’ll try it out! She won’t miss them. 🤷‍♂️

[@taofledermaus]

Ha! I'd feel bad shooting them.

[@ryanjohnson3690]

The science teacher we all wish we had in school

[@adg1017]

Sounds like the F18s were out that day. My son snd I saw them yesterday when I was in Visalia for work. Saw a two-ship, and it’s always cool to seem them flying formation!

[@SelinicaHarbinger]

due to the mention of arrows, as someone who does some archery I want to toss in my two cents. Even with fairly straight fletching and natural feather, the wing (shape) of the feather will impart some spin. It gets more pronounced with helical or angled fletching but from the slow speed and typically shallower angles, it's not a very fast spin. But for arrows it really only needs to help with the paradox and straighten the arrow flight out. Spin rate would matter on the stability of the spin stabilized finned slug too but that would require a lot of testing/modeling to find the right rate.

[@andrewhill2614]

Thank you for all your hard work.

[@spergalicious27]

That guy being interviewed was like a deer in the headlights 🤣

[@gavinkemp7920]

My understanding of riffling is its primarily their to stabilise in the barrel where defects in the bullet and barrel have a much larger effect. And whilst spinning could help correct the defects in the bullet, you are far more likely to have a defect in the bend of the fins that would be far more detrimental than in the defect in the bullet.

[@pauljs75]

Of course in some cases it may complicate things more as you have to do more to make sure the projectile is better balanced in regards to the axis rotation. (If not accounted for that may have a corkscrew path behavior rather than stabilizing.)

[@Simon_Nonymous]

Singing the Smiths at us - a rare treat!!

[@jeremywilliams3320]

spin stabilization allows for the minor imperfections to cancel themselves out instead of compounding them downrange

[@dickdastardly4236]

You need to shoot them with bent fins, through a rifled barrel, while in a tornado. Don't forget to wear your heat vision so you can find them on the giant tarp.

[@SeaWasp]

Don't forget to secure the target!

[@kj3n569]

It would also help to get tequila drunk first and then lay down on a bed. You get some major RPM's doing that! Or so I've been told.

[@EvillClaws]

don't forget to shoot sitting on a office chair whilst you spin around

[@metamorphicorder]

They actually need to set up a rig that will allow them to spin the rifle and have a wireless solenoid to be able to pull the trigger. Gotta try all the ways of atabilizing the bullet.

[@B.V.Luminous]

🤣

[@rayhall3010]

Always learn from you , I promise you , keep doing what you do ,

[@abdulnaggayev2142]

Охочусь 25 лет,пробовал разные пули,думаю,с гладкого,не дает врашнеие пулю.не стоит замарачиватся, а так,Greq вы супер,ждем,новых видосов,удачи тебе.

[@stoatystoat174]

anticlockwise can be widdershins in scotland, in common phrases such as 'the devils jigged thrice whiddershins about the kirk!' (edit: speling fix)

[@petermiller7028]

Barnes Wallace used shaped fins on his " earthquake" bombs, the logic there was if my memory serves me well to maintain stability in the trans sonic speed range...from my rc aircraft building days 30 degrees was often quoted as the maximum control surface throw to prevent flow separation...just comments not criticism and I am ready to be corrected. Great channel ..

[@EvanG529]

There's a lot of potential in induced spin. Like you said, the spin rate of the angled fin rounds was higher than if it were fired out of a rifled barrel. I would probably reduce the angle of the fins to match a normal rifle spin rate and see if the stabilization is more consistent.

[@matthewspencer5086]

When Barnes Neville Wallis needed to improve the accuracy of the Tallboy Earthquake Bomb (it was wobbling as gravity accelerated it past the speed of sound) he added some spin, but he did it by offsetting the straight fins (not bending the fins themselves) and he only did it a _little_ , certainly not as much as forty degrees. The result was nearly perfect. The difference between a Tallboy and a slug is that the Tallboy has time to build up spin before it reaches the speed at which stabilisation is needed.

[@reodds]

Great video as always. I'd like to see the straight fin version shot out of a rifled barrel. That should be the best of both worlds.

[@nanaki-seto]

Yep and a higher rate of spin will buffer out those imperfections to a greater extent (to a point) you will at some point reach a point of diminishing returns with great rotational speeds and if you continue pas the point of no increase of reduction of those defects you will begin to reintroduce the negative effects of the defects. Assuming forward moment is identical shot to shot to shot. You can actually test this with bow and arrow by taking a broad head and bending the tip of it on a 2 edged broad head. Then putting the fletching on to shafts at a angle and introduce spin to the arrows. Shoot in to a card board box at nearly the limit of the arrows range so you do not damage the broad head. If you bend it enough you can get a very drastic curve to the arrows trajectory or have it snap in to LOL. Yes i actually did this as a experiment for a college class long long ago. After a specific point the rotation of the arrow was to fast and the bend ended up steering the arrow to the left or to the right depending on what side the bend pointed. Below that threshold it self corrected and hit the proper point of aim. To get rid of human error i used a very rigid stand with about half a ton of weight holding it steady with the bow clamped in. To get the rate of spin i calculated it as i had no access to high speed cameras. Probably the most complex math i ever did in my life and i hated every freaking second of it lmao. The amount of deviation do to imperfections ither induced or incidental is directly proportional to the speed of the projectile fired or launched and the rotational velocity. These induced or incidental imperfections are corrected for by spin how ever not only do these corrections reach a point of diminishing returns but further increasing the rotational speed will re introduce the incidence of deviation directly proportional to the rate of spin stabilization and projectile velocity..... WEEEEEEE quoted from memory :\

[@markthe2nd741]

Try angling the entire fin about 10 to 15 degrees. You should get a more even airflow that way and less yaw inducing turbulence. Each fin needs to have the exact angle as all the other fins. Weight distribution may also be a factor in preventing yaw. Anxious to see what you guys come up with.

[@iwishiknew10]

Pushing buttons of approval

[@rickoshae1687]

absolutely love that the marketing director of franklin armory is so clueless.

[@taofledermaus]

For not having any notes, I think he explained it pretty well.

[@misterdubity3073]

1. If the bend in each fin is not precisely the same, you'll create some instability. 2. When striking the target, the spinning projectile will likely do more damage than the one that is not spinning, or at least different damage depending on the details. 3. The energy to rotate is stolen from the kinetic energy from the velocity, so the spin will reduce the velocity slightly (but probably by an insignificant amount).

[@kasuha]

I think such angled fins are actually going to make the projectile less stable than straight fins. Reason is that fin stabilized projectile always wobbles somewhat as it is flying and if it is spinning at the same time, it presents the air stream different "face" of the tail at the end of each wobble. Also combination of the wobble and spin creates gyroscopic effect.

[@Sableagle]

"Straight fins" there was rocking up and down a bit, but nothing like that first angled one. I think by bending the fins you're introducing a lot more things that can be imprecise, and they probably matter. Technically, arrows' fletchings *do* spin the arrows. That's why each fletcher only takes *one* wing of the goose. If you use feathers from both wings, your arrows try to go in circles. Take all feathers from one wing, they spin. Worth noting, perhaps, that the spin of an arrow doesn't stop it arriving point-first when shot from 80 m back using a 36 lb draw (yes, in England we mix our units as well as our drinks) and having to aim so high to hit the target that the sights had to be dismantled and reassembled upside-down just to be able to use the top of the upright of the frame, above the target, as an aiming mark.

[@michaelmoorrees3585]

1:45 - Gun Jesus ! This video has been blessed !

[@davidelliott5843]

Supersonic jets have all flying tails because the shock wave compression messes up hinged surfaces. These slugs need angled rather than bent fins. The Barnes Wallis Talboy bomb went supersonic on the way down. It’s fins impart a spin but the angle is very small. Check out the images on Wikipedia.

[@MrMidnight2236]

I gotta say , in the water test it definitly looked far more stable . Love that test btw .. very good way to see what your trying to explain . I think if the fins were manufactured for the spin and not diy bent after the fact ( no dissrespect ) it looks like it possably could make an improvement over the straight fins . Even if not much Just my .02 Love your videos and the work you put into testing and explaining things .. its a nice break from the normal guntube videos . I love to learn about things i have intrest in so its nice to have a channle that touches on the learning side a little more . While still being fun

I do believe that the spinning projectile should be more accurate. Straight fins will still allow the "bullet" to bob up and down or side to side and it can be seen in the slo-mo footage. The weight at the tip wants to go one side and the fins push to the other, giving a pendulum effect on the horizontal. It keeps the general projectile in a nice trajectory, but I think it'd affect the overall flight distance. That doesn't happen with the spinning "bullet", which might not be more accurate than it can, given the "bullet" but it might be more accurate on longer distances. Or at least that's how I see it in my head.

[@outcast170]

The idea that bent fins effected it at all was more surprising to me than anything else. Something this channel has proved repeatedly is that, in most cases, over engineering fine details usually doesn't have much effect, at best, and possibly hinders accuracy or consistance more often. Sure in many cases things make for a "neat" design, or possibly a slight overall improvement, but as with many other things, usually "keep it simple stupid" performs better on average.

[@Lost_Hwasal]

Long time archer here. All arrows spin, modern day plastic vanes will either be offset or have a helical pattern to induce spin. Fletchings have a natural curve in them and are reffered to left or right wing fletchings, even when fletched on straight this curve in the feather imparts arrow spin, additionally arrows spin by default due to how strings are made. Overwhelming consensus in the archery community is that imparting spin improves "accuracy" greatly. Supersonic ballistics and arrow flight are not the same, though.

[@vandercudo]

Nice to see Ian on the video.

[@oddis188]

Haha. As a Fin i have to approve this! 🇫🇮❤ perkele!

[@anthonybarker9123]

What did I learn from this video? That I REALLY need to find a way to get some of those slugs.

[@murisio]

i may come late to exlain this but giving angled fins would be actually pretty detrimental for the accuracy, since you are imparting a moment of rotation at a certain distance to the center of mass, so if theres any disturbance in the air flow it would actually make it describe something called "euler's rotations" and start tumbling as you can see in the slo mo footage, so it would be pretty rng based. Also take what i say with a small grain of salt, im an engineer student but i dont have a complete formation in stability mechanics