Also just to note. What you are describing are the forces on the disc at t=0 if we measure time starting at moment of flight. But the moment of flight isn't when the disc leaves your hand. The moment of flight, or t=0, is actually when the disc BEGINS TO PIVOT out from your fingers. It can be considered the first rotation and why the leading edge points nose down when supinating your hand (because the disc has gyroscopic properties at t=0)
Thank you for your insight! And I did ask the dog to be quiet, I just don’t think it understands English. My mic wouldn’t turn on so I apologize for the xtra noise. I fixed it when I got home, so the next video should have less ambient sound.
Nice. Back in the day when all DGs were also all around frisbee competitors, competing in 8 or more events, like Freestyle, we all knew the 90 degree rule. Force applied to the top or bottom near the outside of the disc shows up 90 degrees later in the direction of the spin! Mentioning the airbounce technique was perfect. As in another comment, this applies to disc angle on impact, hilside or basket. Rollaways dont happen by some mysterious luck of the DG gods. It is both predictable and avoidable if you understand the physics and you execute correctly. Thanks for a must-know video... PDGA 308
You could say at the hit point it is experiencing angular acceleration- gaining angular momentum and spin. It is this angular momentum that "turns on" the gyroscopic procession effect. It certainly makes sense that it has enough angular momentum while still in contact with the hand to cause gyroscopic procession effects to occur. The same effect can be seen when discs land- the big hyzer skip is an upward force on the side of the disc being "redirected" to the nose of the disc.
Agreed, thank you for the clarity in your comment. I suppose I am just being careful to avoid calling it a gyroscope since we are pivoting from the rim and not the center of the disc, while trying to break it down in as simple of terms as possible.
Pete - what you're describing is exactly the same phenomenon that occurs with rotating helicopter blades. Gyroscopic Precession and Phase Lag in rotating blades means the pitch angle change in the blades takes place 90-degrees after the swash plate made the control movement. Never made the connection this is what's happening with a thrown disc, but the similar physics now completely makes sense. You'll find much more research and explanations for GP and PL in helicopter rotors that can be transferred to discs.
Yes! I’ve flown rc helicopters and still love flying rc sailplanes these days which opened the world of reading the wind and air up to me for disc golf. My experience with the helicopters started me thinking about this stuff many years ago!
I can attest to the maxing out of the coffee pour in the wrist. The harder I tried to flex it down, the more nose up I would get when wrist tried to release at hit. I was shocked trying the key turn to get more down numbers on my tech disc. Part of me is in disbelief about the tech disc numbers on nose angle, but this discussion is making me trust the data a bit more.
I've been pounding people on the "nose" of the disc for a while. And what is taught as the nose is not the nose. its what you're saying. I took high speed footage to prove it as well. The hardest part of this whole situation is explaining that your grip to relation of your wrist flexation is really important and how we set up our body. Pouring the coffee is only part of the equation, how our arm is able to move is another. I think what you're possibly meaning to say is that its taking linear torque and turning it into rotational torque. Because were taking leverage and turning it into speed and spin basically. I'm a bit skeptical on this whole flip the disc over method though. Because the idea there is that were imparting off axis torque on a disc to essentially try and get a gyroscopic effect of pushing the nose down. I think that we could be publishing this particular data in more of a "bandaid" form, vs some of the other things. As in. It's being presented as a fix for everything, not as part of the total picture.
Thanks for your comment! The main point was to try to simplify the understanding of what’s going on. Yes, pouring the coffee is part of the equation, however many act as though they have a 5 gallon bucket of coffee and the over exaggeration causes other problems. A careful pour the coffee technically gets the disc in line with our wrist. Yes, the “flip the disc” technique isn’t the full answer and is as you say a “Bandaid” and will inevitably cause other form issues, I currently believe that the “flip the disc”, “turn the key” and “suitcase” method lead the individual into proper flexion of the wrist. This flexion is felt fully as an opposition to the elbow being “up”. This being done properly in effect keeps the thumb from rolling under and dominating the swing. Case and point, if our footwork is off, our hips will tend to be off, our reach back then be wacky, and our timing will be off, so the “flipping the disc” idea as well as other ideas like it will also be a bandaid with some placebo effects but ultimately will not make for a consistent throw.
Ya know. I was trying to wrap my head around why "turning the key" helps with nose down. It just didn't make sense. But this really cleared it up for me. As you supinate the wrist in the pocket you basically over correct into the "finger nails up" finish. Thanks homie. Glad i watched this video.
This is so good Pete, I've just started putting what you were saying about the nose of the disc and it's straightened out my putts dramatically! This video is solid 💯
You should team up with the guy from Zona Disc Golf. I think he’s a physicist. He could probably give the technical reasoning behind your practical observations.
It's still a gyroscope even if it's attached to our hand. It's just that a fully grown man is easily strong enough to dominate the gyroscopic effects of a 175g disc spinning at 1000-1500rpm. Try it with a two-ton flywheel spinning at 6000rpm and you'll realize that it doesn't stop being what it is just because you put your hand on it.
Agreed. From reach back to the 4000ths of a second before it rips from the hand it there is the equivalent of a half rotation imparted on the disc, which on techdisc reads as a ramp up to 800rpms. The main thing up for discussion for me was, can we call it a “gyroscope” when being leveraged from the edge, or is there a different scientific definition we are supposed to use. I feel I’m grasping the general understanding of what’s going on and sharing it, but I try to be careful to not make assumptions in my own statements sense I don’t have a phd in physics.
Awesome! I have a TechDisc on the way for a disc golf physics and biomechanics research project I am working on at my university. Pretty excited to try it out! I made a similar tool to what you are showing with a magnetic top spinning while hanging.
Cool stuff. I've gotta watch more of your videos. Why is it behaving this way? Because it is spinning very rapidly while we are holding it. The disc is spinning at its maximum rate at the moment of release. The hand (fingers included) is what causes the spin (and all the stuff leading up to the release). So of course the physics will act like it is a spinning object. This video made it sound like this was in question or unknown. Please forgive me if I misunderstood. I had not thought of this before. This is so cool!
Hi Scott, I think the basic point is: the disc does take on angular momentum just before the the release, the forces we impart upward or downward at that point are called “off axis torque”. The exercise for me was to state this in as simple a way as possible as well as allow you to see me perhaps struggle to simplify it without getting the language wrong for all the physics majors. :)The question needing better explanation is: can we call a disc that is still in contact with our hand, being levered from the edge, a “gyroscope”, and or what do we call it if it is not technically called a gyroscope till its free spinning on its own. My point is stating that the disc is taking on angular momentum through the last bit of our throwing motion, and thus has the capability to resist off axis torque. If our last point of contact forces upward or downward in swing plane or from our fingers imparting a dis-symmetry in pressure, the effect of force will be observed on the “tail” of the disc at release.
If you hand has any force on the disc like you mention it would wobble Before it rotates the way you state. That force only happens after the disc is spinning.
“Off axis torque” cannot exist unless the disc is in some way experiencing angular momentum before exiting the hand and fingers. Dis-symmetry in pressure between the thumb and fingers on the top and bottom of the disc at the moment of release does account for wobble.
Prediction.. three force directions, normal force, downward force, and tangential force… if you apply downward force it will split that force into two components of that downward force, a force normal to the disc and a force tangential to the disc which direction the disc is spinning from my point of view im not sure but I think the rotation of the disc will push/change/reverse the tangential because you are applying a negative force which will make one of the other forces negative in respect.. magnitude aside just positives and negatives
Really interesting video Pete! Thanks for sharing this. Do you think this means that the ulnar deviation/pour the coffee is trivial or do you think that a combination of ulnar deviation and the supination/flipping the disc is essential to get the desired amount of nose down?
A form of Radial deviation grip is where most folks start their disc golf journey. Somewhere along the crease in the palm in line with the knuckles. Our goal is to line the disc up in the crease on the hand from between the index and second finger along the crease that runs along the them/palm into the wrist. A soft ulnar deviation will line the disc up along the forearm and wrist. “Pour the coffee” should be given with a caveat of “is HOT, pour gently, or you’ll spill and scald your yourself”. When we over exaggerate the pour, we inevitably will bind the hinge (our wrist) along its extension path, which will lead to it wanting to unload radially part way through the release, often leading to a nose up issue. If we grip the disc properly, I think much of this discussion will inevitably work itself out. “Flipping the disc” over the wrist, is a “feel” exercise that helps us find a position not totally natural. If we stand and hold a power pock position with the elbow up, forearm level and disc flat, we will find that there is not much room for the wrist to supinate, drop the elbow and we can supinate farther because the elbow is the “limiter” to that movement. Pronation is super easy to do in this situation because most of the movement available along this axis is free to use especially since the gripping muscles pull in that direction. Supinating of the wrist puts downward pressure on the disc and the nose will go up. If the grip is set up properly the muscles will work in such a way as to help the throw rather than harm it. These “feel” exercises (flipping the lid, turning the key, suit casing, etc)are not the final solution, but rather a gimmick to guide us into what the proper position feels like so we can better align our body’s with the action we wish to produce.
so on a forehand throw, would the reaction be on the front instead of the back of your disc.... meaning, when you have the same focus on nose-down as with the backhand, the disc tends to go nose-up...
Assuming the forehand is RHFH, we would be imparting a counter clockwise spin. From the last point of contact, the effect would take place 90* away in the direction of rotation. Let’s assume our release point is at near the 9’o’clock point on the disc in relation to the direction of the throw, the effect would be at the 6 o’clock position.
I have one (a lot more than one) question about something that you're alluding to but I'm not sure if you have explained yet. When your forefinger becomes the last point of contact and pushes upwards on the disc, it's causing the disc to tip nose down a little. Is there a way to control this? Are you saying that the fan grip has less rim pressure so the pop off doesn't cause the disc to go nose down as much and a stronger power grip would force the nose down a little more on release? Would you want to minimize this release point contact to minimize wobble or are you sacrificing power when you minimize release point contact?
Thank you for the question. I generate basically the same amount of spin with a modified fan grip as I do with a power grip. One interesting point I noticed is that the grip pressure is distributed near the same but slightly different. Power grip: my index finger squeezes around the rim to itself with the thumb covering/pinching down over it, while the two middle fingers squeeze into the palm as well as the pinky finger. Modified fan grip: my index finger squeezes around the rim to itself with the thumb covering/pinching down over it, while the two middle fingers stack over the pinky and each other then squeeze into the palm but through the flight plate. If the fingers are squeezing up and into the palm it tends to keep the thumb from dominating and causing the pronation or turning in/rolling under of the wrist through the release point. At the moment, this is the biggest takeaway. With both of my grips the thumb and index finger come free of the disc at nearly the same time. Check the video that I posted just before this one for that video footage. I think a certain amount of wobble is almost unavoidable because the thumb comes off a smooth top while the index finger is snapping off a ledge. I’ll do some coaching and form videos in the future, but for now I’m enjoying sharing the why of what’s going on with a disc. Once I get a few of these out, it will be easier to understand why I believe in certain methods of throwing and How we influence the gyroscopic system of a disc.
did i miss the part where you tell us HOW to throw nose down? i seemingly finished the video still not understanding how to achieve nose down.. am i to assume that to get the nose down i need have the bottom of the disc "underneath flate plate" facing my chest within the power pocket vs the top of the disc? or are you saying we should attempt to throw nose up so opposite of coffee pour making back of disc nose up but the back is really the front and when released the back becomes the front?? im still confused??
This was not a “how to video” on how to throw nose down. This was really to help everyone understand what is “the nose” and how gyroscopic procession, and how the the pressures of off axis torque drive nose angle. I’ll do some coaching style videos on the future and explain ways to help drive the nose angle down. There is another video before this one discussing” the last point of contact” I’ll say this. If at the release point the wrist pronates, or thumb rolls under/pushes down on the top of the disc, the nose will go up. If at the release point, you supinate the wrist, keeping the thumbnail pointed to the sky, and fingers under the disc keeping upward pressure towards/into the palm, your will have better luck throwing nose down….. “Coffee pour”… the whole purpose of this phrase is to get the disc level and in line with the wrist and forearm, Moving it from the disc lining up well below our elbow. If we push the coffee pour to an opposite extreme, (a common problem now) as if pouring a bucket, the alignment of the disc will point not through the center of our forearm but across our forearm and above our elbow….this binds the wrist and exacerbates the nose up issue in the end.
This is a true statement. Maximum rotational velocity is reached at the same moment that the disc is departing hour hand. No additional rpm's happen after this moment.
Hi Josh, it's been a wile, hope you are well my friend! To your question: Basically yes. Let's think of it this way: if we pronate the wrist/roll our wrist under, we will have a downward pressure on the top of the disc through the hit point, because the thumb is our point of contact on the top of the disc, this seems to drive the nose up. If we supinate the wrist through the hit point (think turning a key clockwise for rhbh) it basically stops the thumb and wrist from rolling under removing the majority of downwards pressure and at minimum allowing for a neutral nose angle. In my last video, I showed a super slo-mo clip of my fingers and hand at the release point. For me at least, it looks as though my index finger is the last point of contact on the disc, this could in turn mean that part of my negative nose angle is possibly due to the upwards force of my index finger on the rim at the moment of release. @980 frames a second, the thumb and index fingers release separation occupy only 2 frames. It's sooooo fast. Im not trying to let go with my thumb or index finger, it's just what happens when I follow through on my throws correctly....Perhaps that's for another video!
@@DiscgliderPete I think this is a symptom of thumb placement as well. Thumb to close to center is probably going to cause the thumb to be the last contact point and if it's closer to the rim it should come off before the index finger snaps off
I’ve been coaching disc golf for quite a wile, and discussing these ideas for years. Learning the what’s going on with disc flight and how our swing influences it has helped me come to some practical approaches to coaching.
It does take a certain kind of courage to drill a hole in a perfectly good disc. It felt nearly the same as throwing my favorite driver over a water carry to an island green..
That is the question that is posed, and the correct answer we think is: yes. We are adding angular momentum to the disc from the power pocket through the moment of release. When rotational forces are being added to the object it begins behaving similarly to an object with gyroscopic procession. The common vernacular we use in disc golf is “off axis torque”. This term makes no sense if the disc is not spinning or moving in a way around an axis by which it could in effect “resist the torque ” from an off axis force.
What is needed in this discussion of angle of attack is slow motion video of "nose down" actually flying better than a neutral angle of attack. Tech Disc is a great tool, but I am very skeptical that what is being called nose down = a negative angle of attack and not roll angle instead. Nose up is a common problem for sure, and I believe what people are getting from videos like these is how to reduce nose up angles and get closer to a level release, which is a great benefit and can add big distance. Having the disc be anything other than completely parallel with the pitch angle is problematic and will increase drag substantially. Imagine this: You are driving in a car going 60mph you have a disc on a pivoting fixture that only allows positive or negative pitch (nose down, level and nose up) You stick this fixture out the window and you start with the disc perfectly level (and parallel with the cars trajectory through the air) this is optimal. If you move the nose up even 1 degree, the disc will want to go up and if it is not allowed to, there will be a lot of drag. The same is true for nose down. A negative angle will make the disc want to go towards the ground. A disc is also a wing, so the exception to all of this is that in level flight, most discs create lift, and this can result in a disc gaining a little altitude while also have a neutral angle of attack. Disc spin adds gyroscopic stability, but a non spinning disc has the same wing shape and generation of lift, etc. I contend that ANY level throw that gains altitude after release has a zero or a positive angle of attack. Any throw that loses altitude immediately after release has a nose down, negative angle. I will be very interested if these concepts can be proven wrong with something other than the Tech Disc. Anyone work at a wind tunnel?
It is like how a spoiler is used to keep a race car on the track. To increase down force, the spoiler becomes more vertical to add downward pressure. The car is built low to the ground to minimize air under the car that would lift the car. My hypothesis is that the “nose down”release probably stabilizes to neutral quickly whereas a nose up release of any kind will catch a lot more drag since the disc would be like a parachute underneath and lift more and more never getting to flat. A perfect 0 would likely give you best flight but slightly nose down probably is better side of error than slightly nose up.
The interesting thing to consider about this, is that a disc in flight is not reactive to itself over the center of balance. During the initial portion of high speed flight the lifting force or center of pressure moves behind the center of balance. This in principle lifts the “tail” of the disc, but due to gyroscopic precession, the effect takes place 90* away in the direction of rotation, which we then observe as “turn” (rhbh/ clockwise spin). As the disc slows down the center of pressure moves ahead of the center of balance and is part of the reason why we observe “fade” at the end of flight. I would make a hypothesis that negative nose angle imparted at the release point while throwing upwards, helps the disc “get on plane” or arrive at a neutral angle of attack at a higher altitude and farther down the fairway and helps the disc take on the forces more predictably during the high speed turn portion of the flight. Should we start simply with a neutral angle of attack, the finishing part of the flight would have a higher angle of attack or more nose up finish during its fade due to how the center of pressure advances ahead of the center of balance. If the Disc was simply a wing like an airplane wing or a foil on the back of a car, it would be a far more simple algorithm to understand, but the moment we add spin and thus gyroscopic precession and stability it becomes far more complex. It would seem to me then, that to “error” with a couple degrees negative nose angle early in the flight, especially when throwing up or higher than level, is far more beneficial than to error with any positive nose up which adds more induced drag from the start, and limits distance immediately.
Great reply Pete. The logic is sound and getting people to stop throwing nose up is great for the sport. Curious, is all your info supporting when the lift is fore and aft coming from Tech Disc data? Playing with the simulator on their site and having 10 degrees of nose down give more distance than a level release is, well, unlikely. We need good mythbuster side view style slow motion video of various releases that prove this concept.
Well the disc will retain the inertia you put into it after release and even though its not independantly suspended from its center it is enough of a gyroscope to manifest even MORE of the "offset effect" that gyroscopic precession is (btw I think the spellchecker nailed you in the title of the video =). In essence your fingers stabilize the disc only partially and the one axle we truly care about when we want to manipulate noseangle is more or less free from interference by us since the force we apply is more or less aligned along it and thus has no lever to work with so even though it's not fully a gyroscope until you release it is enough of one to respond accordingly. I also find the behaviour of beat-in discs fascinationg in this context as their "extra understability" works differently than what you get from simply having a low partingline since the uneven "wavy" topside of a beat up disc essentially generates slightly more lift with the side that rotates against the airflow which serves to lift the nose of the disc more and more during the flight which is kind of what you want for a soft "extended" landing on a long throw. I think the best analogy to explain that effect would be something Czesław Antony Marchaj called the "flow memory effect" in his book "Sail Performance". In essence he described how airflow does not immidiately detach in response to sudden increases in angle of attack as demonstrated by not only birds flapping their wings but windsurfers pumping their sail generating more power than they should by static analysis. The uneven surface of a slightly warped disc that is spinning would in my opinion also benefit from this effect and I think that is primarily why their behaviour is so special. Finally re: Precession I think the MIT lecture given by Walter Lewin on gyroscopes is still one of the best on youtube.
Hey thanks for that explanation! Since you are casually blowing my mind a little maybe you can explain physics behind the turn of the disc. Is it like a pressure difference thing combined with gyroscopic procession?
@@chrisp9824 Well first of all just like with an airplane wing lift comes from the movement of air over the top and airspeed across the surface matters because more speed => less pressure (air is essentially a gas in motion). The "microwarping" of a beat up disc won't do much on the side turning with the airflow but on the "upwind" side it will basically vibrate against it. This "vibration" essentially does the same thing as a windsurfer who pumps the sail => it moves up and then down again to "yank" the air down with it. This then creates a force "lifting" both the left side of the disc and the "precession" then also lifts the nose over time. In contrast the "off the shelf" understability of a disc with a low partingline works by pushing the nose down which then causes the precession to turn the disc over into an anhyzer. With premium plastics it really won't show up much though since it takes a lot of abuse to bring a disc to this level of wear but slightly overstable molds in a baseplastic that really distorts on impact will showcase this quite well after you deliberately abuse it to add 2-3 steps of understability. I've also had a few biofuzion Trespasses over the years that got to this stage of wear after 6-8 weeks in the bag.
@@chrisp9824 "dimpled" top wouldn't usually be the same becuase most of the time the dimples are made sharp enough to detach the airflow just like on a golfball as is the case with the Latitude 64 "Raketen" and "Missilen" discs.. I have a Raketen and the price of the extra speed is that the lift of the disc is cut in half. If the surface was softly "wavy" it might work better but it would need to be subtle and the alignment should be much like the spokes of a wheel.
If we do release the disc nose-down, does it actually fly nose-down for more than just a few feet out of the hand? There is a whole new set of forces as it begins to fly. Can you please take your TechDisc and actually throw it in the field, and record the results for the first few seconds of flight.
Tech disc as I understand reads only the first three feet of flight. You pose a fantastic question. First, the disc nose angle is measured in relation to launch angle. So let’s say -2 degrees nose down compared to launch angle of 6 degrees up would technically be 4degrees compared to level ground. The initial negative nose angles seem to help a disc thrown on a higher launch trajectory move forward higher off the ground and longer before stalling. Once a disc is spinning in flight, it now is responding to the forces of air passing over and under it. At rest, a discs center of balance is basically the center of the disc, but as the disc moves forward through the air in flight, the air moving over the disc creates Pressure or a lifting force. When flying at high speeds the center of pressure moves behind the center of balance, so in effect the air moving over the top of the flight plate begins lifting on the disc behind the center of balance. This is what is partly responsible for the high speed “turn” of a disc. The more “under-stable” discs tend to divert more air over the top of the disc generating more lift. As a disc slows down its lift diminishes, so the center of pressure begins to move forward in front of the of the center of balance, and we begin to see the discs precession towards what we call “fade”.
For me, it’s all fun. I absolutely love throwing, competing, watching all the flight shapes, coaching, and in this case seeking out understanding of disc flight dynamics and the physics behind it. I’ve procrastinated on creating a video about this for probably 5-8 years. I’ll post coaching and fun content later:)
Would love another vid where you show it from your POV so it's easier to see instead of having to invert in our head. With the camera set up looking away from you, you could hold the disc out in front of the camera. On the point about when it becomes a gyroscope, I don't know anything about physics, but if you apply a force to the disc just before it ejects, there should be a lingering impact of that force (e.g., pushing a side down) which is then certainly present when it is more purely a gyroscope
This was an awesome video, Pete. The live gyroscopic precession demo was one of the best I've seen for disc golf physics! I'm in the research and planning stages of making a comprehensive disc physics video, and wanted to see, would you be ok with me using a clip from that demo in my video? I would make sure to mention your channel and give credit, of course. Let me know what you think :)
