Supersonic Darts - The Effects of Inducing SPIN - I learned something!
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- Опубліковано 11 жов 2024
- 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 UA-cam Channel:
/ tahow7798
"Not to be confused with this type of Fin." - I got a hefty chuckle out of that one!
I'm seeing a meme of "straight Finns vs not-so-straight Finns"
Thought they'd use the Beyond the Press couple as an example of straight Finns.
Perkele!!
@@st3v3h4py "Not so straight Finns" are called swedish-speaking Finns.
@@Tunkkis Man I would hate to be Finnish and have someone use my likeness to demonstrate a "Not so straight Finn"
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 ;-)
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...
"Using high tech sorcery" - I love living in these futuristic times😄
Any sufficiently advanced technology is indistinguishable from magic.
-Arthur C. Clarke
Exacto knives these days are futuristic. WW3 joke btw
My favorite kind of sorcery
I'm so shocked these gunmen also know warlock magic
to make it spin without bending the fins
chop the trailing edge dual bevel to a single
as in from this /\ to this |\ or /|
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.
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?
Also I wonder if the obturation ring is causing a vortex to extend out over the majority of the fin like a kFm airfoil?
@@mk6315 you're probably right. I mean traditional slugs have straight cut "fins"
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.
I absolutely agree with you.
ua-cam.com/video/lXeyEeXS-cg/v-deo.html 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.
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.
You highlighted what I tried to say in my comment much better, thx
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.
The closing summary was the best thing I've ever seen in any of your videos. Great learning moment, thank you.
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.
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.
Depends on the range also, because if it rips a gut, then what range to be at to make it vicious?
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!
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 🙏
thanks Andrew
I miss Danny... 😢
@@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.
Great Video!! I have 40yrs of Archery Experience and there is always the discussions of Straight vs Helical Fletching
for Field Points. I use Straight Feathers on my Longbows and Recurves.
Love how you explain everything watched you for a long time and always learn something new..
thanks Ian
The best channel. The style hasn't changed much over the years, no smash like bullshit and whatnot. Always straight to the point and entertaining.
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 😉.
YES! Exactly! Put the fins in front. That's what you meant, right? 🤪
@@dotar9586 what?
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.
@@-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.
That's why somebody gets to test it.
I was listening intently,. and then I thought, Jeff would be a pretty good teacher. He does explain things pretty thoroughly.
@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.
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.
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
Spin reduces effect of poor separation on accuracy
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 👍
Oh hell yeah more awesomeness from this kickass channel!
thank you!
I don't have anything to add, just wanted to say this was an excellent video! Went above and beyond in this one!
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.
Yeah...lob em out 50-100 yards to see if it helps farther out
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.
@@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%
@@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.
@@abhijeetsutar5259 you're entirely correct! I completely forgot about the l.e and t.e shock waves 🤦♂️
Thanks for testing these and showing your results.
I love you, Jeff. I love O.G. too.
Take it easy out there. 🤙🏾
thanks!
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.
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.
Dimitri.. thank you for your contributions to this channel
Fin stabilized sabo rounds that are shot from smooth bore tank canons are also strait finned and some are going over 5000fps.
Not all are straight finned. The US is going to slightly canted fins for better stability and accuracy.
@@markfergerson2145 roughly 1/2 a degree, per The Chieftain
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.
@@Falconguygaming Yep, and he should know.
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.
i like how much conversation there is about fins
greetings from finland 🇫🇮
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
Despite the poor video quality we all still love you. I am always impressed by the work you and the others(I still count Danny) put in to making these videos. While the spin is impressive it really doesn't seem to add anything to it's terminal performance. It just reflects how well the original design and manufacturing was done.
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.
where you gonna find a helical bird though? :p
In my own ventures of crafting sub sonic projectiles, I can say that angled fins like this will make the projectile more stable, but unless the angles are perfectly uniform and the setting of the projectile is extremely precise, the spin will cause the projectile to stabilize in some random direction once it's in flight. Kudos to you guys for making content based on what your viewers requested. Top notch content as always.
Officer Greg, you make what has to be my favorite type of videos. Guns, ammunition, sarcasm, wit and results. I’ve enjoyed each one I’ve seen. Stay safe, shoot straight!
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.
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.
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.
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.
I think a lot of folk try to liken rifled barrel bullet ballistics to slugs from a smooth bore without realising a bullet from a rifled barrel may be rotating at 300,000 R.P.M. At those speeds the bullet to all intents and purposes resists pitch and yaw as each physical input is only applicable for minute fractions of a second and bullet's length, weight, c.o.g etc need to be very carefully matched to rifling twist rates as they can be over as well as under rotated. Over rotated bullets may literally fly apart due to the huge forces involved and insufficient spin won't stabilise them at all. Just expecting to put a bit of rotation to an object and assuming everything will miraculously sort itself out is somewhat naive. Companies don't spend huge amounts in r+d to produce crap that someone else will turn to gold in a ten round test in their back forty. Kudos for attempting to reply to all the backyard ballisticians, though where they got their degrees baffles me. It has taken me 30 years of reading to to get a grasp of what I'm actually altering when I make home loaded rounds in terms of internal and external ballistics..
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.
Good thinking
How are duey and reese?
8:00 - I knew I liked you Jeff, and The Smiths reference made me smile.
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~
I really enjoy watching all of the tests. no matter the outcome. There is always something to learn, and it is always fun.
We use a 5° helical fletching on our hunting arrows, traveling ~300 ft/sec... not 40° traveling at 1400 ft/s... too much power!
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.
It'll rip the target at alil closer range, depends on the range
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
@@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.
@@metamorphicorder he said he bent them in the opposite direction of the rifling so people couldn't say they were cheating.
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!
Seeing that spin rate made me wonder how a heavy, sharp, screw would perform with similar fins if properly weighted.
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.
@@v.Hohenheim aye, I was thinking more in terms of the threads effects on target. Didn't consider the added turbulence though
@@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.
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.
The “angle” in that orientation could cause the wobble, What about like a 3 degree offset, like arrow fletching?
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
Yeah I'm thinking this is just like adjusting the Helicoil or straight vanes when I'm tuning in the mathews monster compound arrows.
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.
Spin for arrows is used to negate the archers paradox where the long and thin arrow shaft wobbles through the air
@@joearledge1 there is some tuning involved but I find a well made Helicoil arrow works well and have noticed preformed well outside over straight
💪👍 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.
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 :)
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.
Windbag. And also wrong in most of your comment.
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.
@@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 ;)
Very interesting Jeff and OG. I was just telling a friend to sub to y’all’s channels this morning.
Thank y’all for all you efforts you put into y’all’s channels 😎❤️🇺🇸
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.
But they do
You can clearly see that the projectile winds up spinning speed as it moves trough the air.
ua-cam.com/video/Hu79sEA5X5I/v-deo.html
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.
@@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.
@@pierre-henrivince4591 have you got a source for this? I can't find anything online.
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.
Jeff, you have a great taste in music. These videos are well paired with enjoyable soundtracks. Another great video, thanks for sharing!
(and by that I mean everything from the heavy metal instrumental tracks to these smooth beats. a wide variety of good taste!)
thanks Desmond
I thought that looked like JR.
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.
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.)
@@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.
@@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.
Hi there Jeff & OG. Just wanted to say you my top favorite UA-cam channel by far and happy to see your video monetized.
OG is the science. He wears a white lab coat and I just know I need to trust him.
he is the "science".
@No Touchy
Same goal, different approach. Simply comes from being a Task Force 69 veteran...
The whole time I watched this I was like "It isn't about stability its about the rotation averaging out any drift!"
And then you mentioned it at the end. Important stuff.
A fin stabilized projectile is stable, but that doesn't mean it doesn't fly at an angle. It inevitably produces lift in some direction. It can also oscillate, and in extreme cases it could lose a fin or become damaged while penetrating brush, etc. Spin also helps separate sabots consistently, although that is not a factor when the spin only starts after sabot separation like this.
Most of all, it compensates for the difficulty of cheaply mass-manufacturing finned projectiles with good consistency.
Answered my question about airflow over the fins…😮
Maybe less fin angle? I’m very curious about this…Fascinating!
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.
I love the behind-the-camera banter between you and OG. The "interruptions" are just part of the fun.
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.
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.
@@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.
I love your hands on scientific approach to these ridiculous rounds
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.
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.
@@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.
Featuring the Return of the Rifled Water!! This was an awesome Video guys. As much as I love the longer videos, I do love these Quick Test Clips like this.
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
Depending on the length of the vane, the angle increases with the length of the flight vane
@@lukebaker1167 know but just keeping it simple bro
@@mikemitchell9157 2 ezy Mike!!!
We love you Jeff! Thanks for the interesting content! Hi to OG, too!
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?
It's the people that _don't_ comment. That's what makes this channel Great.
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.
I thought that weathercocking only happens because of the rocket's thrust.
@@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.
I really enjoy the science that is applied in these videos, with just the right amount of humor. 🤣🤣
thanks!
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
I was wrong and you were wrong
Have a nice day
@@leifvejby8023 yeah it's not the first time and damn sure won't be the last hahaha
@@alexduke5402 Same here
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 😊
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 😳
Ship them over and we’ll try it out! She won’t miss them. 🤷♂️
Ha! I'd feel bad shooting them.
Learned as much from OG and Jeff as I did in college, and it's debatable if this is more important.
Very nice explanation of what's going on with the fins. Thanks..
Your high tech sorcery visuals are actually very cool. Thanks for another educational video.
The lab coat looks pretty slick OG, making videos UA-cam does make you an official scientist. Or so I'm told.
Somewhat related, in a college engineering course we were experimenting with the same principles on model rockets. While not exactly the same, we did come to the similar conclusion about spinning the rockets helping to negate some of the defects from the materials.
One fin design we attempted was angling the entire fin structure from 5 to 15 degrees. The effect was more pronounced and seemed more consistent compared to angling just the tips.
Buck Rogers sure would be proud ! Much Love Guys
Jeff and OG y'all rock! Love the channel and content! I'm here for the algorithm! Peace
Over bent the fins...airflow can only change at 15° angle otherwise it creates turbulence and can result in the weird airflow...I would recommend trying these again with only a mild 15° bend in the fins not the huge 40° angle you used (think 3 angle valve job on an engine intake...cut at 15° 30° and 45° this way the airflow bends around the valve instead of creating turbulence and slowing itself down thru the intake port) pretty cool to see it either way...great job! Keep em coming!!!
Oh and dropping it in the water, rotation or not...it's gaining velocity due to gravity, a fired bullet once it leaves the barrel no longer has energy being applied to it, so it will slow down
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!
I used to make slingshot crossbows as a hobby and I made every thing by hand, including darts/arrows/bolts. I used bamboo kabob skewers for arrows but being smart I tested hundreds and hundreds of styles, I settled on something that was deadly accurate but also cheap and super easy to make. I would put crafting wire wrapped a bunch of times at the end near the point so the darts were front heavy, then I’d use some thin card board from a cereal box for fins. I’d hot glue the cardboard in fron of the knock, and I noticed the darts would be accurate but not as much as I wanted, always like a five inch group from about 20-30 feet away, but then I realized I could bend the corners of the card board like a fan and get spin stabilization. Easily doing 1-2 inch groups after that. I miss being 16. I was such a crafty smart kid. I still am, just don’t have a work shop anymore.
As seen with dart blasters SCAR BARREL is a usualpy adjustable device which adds rifling at the end of the blaster. Adding too much of a twist on the rifling causes the dart to "whirleybird" and spin out from overstabalization. I'm sure sub vs super sonics plays a part. But food for thought for those who are interested.
Finally found another person who knows which part the sabot is. I thought the whole internet was wrong. Also, if you dig real deep into aerodynamics, a spinning object affects the boundary layer of air against the skin. In artillery for example, we know the spin of our projectiles alters the course of the round, especially in windy conditions. I wouldn't assume the only effect of spin is stability.
I'm no airflow simulator but counting the fact that the projectile is traveling nearly Mach 1 the fin angle is way to big, comparing to a tank apfsds round we're the angle on the fins is barely visible. Another factor to take into account is the machining done on the actual round with when traveling a such speeds can cause tumbling as show in the video. Great video and I love what you guys do
"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.
I still miss that cool old guy!!! True gentleman
I was supposed to go to bed after watching this video, but Finland was mentioned. Now I need to go and celebrate it on the marketplace. PERKELE!
Hahaha... just love seeing the flight of these darts heading to the target... Thanks Jeff and OG
You guys are awesome. Thanks for the great content... I've used many minutes of my life on both your channels. Thoroughly entertained in all the minutes used. Haha
Awesome! Thank you!
A man who can acknowledge his humanity is deserving of respect
Ahhhhh yes the great wizard of supersonic aerodynamic testing fantastic as always. I see the magic is working flew true and accurate.
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.
My favorite mass accelerator channel on youtube
When there is eccentricity in a round, spin will make it describe a helix in flight, while no spin will describe a divergent arc. That arc increases with roughly the square of the distance. So, going from 25 to 100 yards you would see 16 times the deviation. That is ignoring any polar inertia which multiplies the effect of increasing distance. The four horseman here are shape, weight, velocity and range.
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.
Content alone is a 10 on this video but throw in OG, Greg's shootin an u're camera skills an editing. Nice video Jeff an those shells be what 20 dollars each at store... I think they'd be high. But I want them.
thumbs up for including the clip of Ian (gun jesus) in the intro description! cheers!
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.
As always awesome video, the best part was the high quality graphics at the end lol 😂👍🏻🔥🤘🏻
Wait, this fun little video was a FULL TEN MINUTES? It flew right by! Holy cow!
The video of Ian giving the Franklin armory guy a verbal beat down was epic
This brought out the inner nerd in me. I fly a supersonic jet. I can attest that by doing aileron rolls, it has a negative impact on where the jet is pointed, if accuracy is your desire. Additional data point, this jet has a symmetrical wing, so it only sees or cares about the angle of attack. And lift is lift, whether its producing it in a tight spiral or upside down. But what I found interesting, at supersonic speed, I expected the boundary layer to separate further, leaving the fins behind the bullet with low to no influence on the flight of the bullet. It is a factor on jets past mach 1, the faster you go, the further the boundary layers moves out and away from the control surfaces on the tail. It makes the jet feel like there is a delay between control input to how the jet responds. Clearly not the case with these rounds, as it was spinning right out of the barrel.
Love the Morissey cover, it was very good🤩thanks Original Geoff I’m gonna dig out my vinyl this weekend🤗
( don’t tell the OG we sometimes spell Jeff with a G (eoff) in the UK. That’s gonna scupper the original G thing perhaps.
Mind you I think you have had senators called Geoff maybe with that spelling??? Michigan??
Man, that’s a tough day filming now, who is the original OG…,😱??
( thanks to you both as danger show and tmouse are a joy to watch and have been for a long time🙂 (obviously danger show not quite as long, but, you get the point) thanks to you both for making and sharing the content. 👍👍👍
Another awesome video! Nice work gentleman.
"More stable than stable" is our motto.
Pretty cool, I like the water test.
I was surprised they spun that much in flight