Roller Physics 101

Today we discus the basic physics principles that cause the disc golf roller to behave in its magical way.
I am not claiming to know all the technical details, as I am not a physicists. Im simply seeking knowledge and sharing what I find, often asking friends and engineers whom I know to be far more educated in the subject matter than I am, for guidance and greater understanding. I just am just a professional disc golfer in love with learning why these disc behave the way they do, and sharing with those around me the things I am continually learning, while In practice, trying to break it down into simple layman's terms.
I hope you enjoy it along with me..

[@Gratefuldad_420]

There are disc golfers that think they know, and then there is you...appreciate you sharing all this knowledge. thanks Pete, keep being awesome!!

[@DiscgliderPete]

Thank you:) though I am still learning. Just sharing what I’ve learned thus far.

[@cthomas3356]

Huge fan of this type of content.

[@DiscgliderPete]

Thank you for watching

[@nktaylo1]

This is some of my favorite content surrounding Disc Golf! Thank you!

[@DiscgliderPete]

I’m glad there are others that enjoy the same things !

[@novapunkx]

I love how you mix science with disc golf! Do more!!

[@rscraig9855]

The more you know the better golfer you'll be. Thank you for the education

[@russellsullivan7366]

Well put 👍

[@PirateDiscGolf-lk7ne]

This is the kind of content that needs a lot of views, not the stuff that is serving no purpose but to create drama. This is creating better and more knowledgeable players.

[@DiscgliderPete]

Thank you for the kind comment. I’ll continue sharing the things I’m stoked about in this wonderful game:)

[@notmyrealname8496]

great vid.

[@directandy]

I always watch these videos as least twice. Once for introduction and again for understanding.

[@DiscgliderPete]

Thank you for taking the time to watch! I’ll keep trying my best to help make the subject matter as easy to grasp as possible.

[@CarlTempleton77]

watched once, going to watch it again. :)

[@natekeeley1706]

Dude-- thank you so much for sharing the knowledge in these videos. You do such a great job explaining the physics.

[@DiscgliderPete]

Glad you like them!

[@sarinhighwind]

Ya know. My weird roller issue. You just explained why it happens. I didnt think about the ripums vs the change of the ground. So it causes off axis torque as it stabilizes.

[@oldguydiscgolf13]

Another great video, I always learn a lot from your videos and apply what I learn on the course and to fellow Frisbee flyers!

[@DiscgliderPete]

Thanks for sharing!

[@jeffgray5295]

These videos are gold! Your video on grip was a game changer for me. I immediately started feeling the snap that I was missing, and made good progress on nose angle.

[@JohnBell3]

These videos are great.

[@DiscgliderPete]

Thank for the visit

[@threeheadedmango1234]

I love this series. It is super interesting and useful to know how disks fly the way they do.

[@DiscgliderPete]

Glad you enjoy it!

[@chrisjensen9941]

Thanks, Brother!

[@DiscgliderPete]

You're welcome!

[@chrisproffitt6198]

great explanation Pete. keep this content coming!

[@nronayne]

I love throwing rollers and i love physics. This is great stuff that I've always thought about, but never heard anyone else discuss. I've also noticed that at the moment a disc lands, it gets an initial extra nudge from the ground, which sometimes adjusts the back edge of the disc and, therefore, the nose angle, making it look like the disc hit a stick or rock or something and so it shoots off in an unexpected direction (especially on forehand rollers when there is less spin on the disc initially). With this in mind, I'm starting to get the hang of nose angle manipulation out of the hand, in order to shot-shape my rollers more effectively.

[@DiscgliderPete]

Yes, if we don’t match the nose angle to the ground perfectly, it can’t take on the ground speed and extra spin efficiently, so the nudge you speak of is basically off axis torque because of the discs trajectory is not in line with its nose angle upon landing. Great observation!

[@ryansuter4424]

Cool video!

[@DiscgliderPete]

Thanks for the visit

[@bradenneffdiscgolf]

Awesome video Pete!

[@DiscgliderPete]

Thanks!

[@crusher26638]

Physics with Pete.

[@nordicdiscgolferatrumble9430]

Another great vid. Love these. Heres an idea for a vid: why do tomahawk and thumber throws pan slower when a flat top disc is used?

[@DiscgliderPete]

Thanks for the comment! I haven’t put much thought into that at the moment….my initial reaction would be I think It may be a similar reason to why a flat bottom boat is preferable to stand up in compared to a canoe. Then would work out the thought experiment from there. Lol Over-stable discs are often preferred for those throws also, so it’s possible that they help control the delivery and nose angle better for those throws.

[@nordicdiscgolferatrumble9430]

@@DiscgliderPete That's an interesting thought. Yeah flat+overstable = bombs

[@kinghorton418]

this is superb practical concept teaching. You can tell you're speaking from a point of knowing moreso than most these type of videos where they are regurgitating discraft wiki. My favorite roller disc right now is forehand with a Axiom Mayhem [13/5/-1.5/2]. If im understanding it correct, its ability to hit like ' / ' but flip vertical and remain ' | ' would be because enough spin, generating lift to pull it up vertical, but then the Gyro stabilizes the force between gravity (or lift?) pulling it like ' \ ' . Where more Spin would equal to a roller like i've described remaining vertical longer?

[@DiscgliderPete]

Over all I think you’re getting it. the lift force pushes against the ground, the ground pushes back, that effect takes place 90* away and causes the tail to move down, this in effect lifts the nose of the disc and is also responsible for the disc “standing up”. Higher Spin causes the disc to resist all the forces more, it stabilizes the flight and roll. Spin doesn’t cause more lift or turn…. Once/if a disc reaches a point of equilibrium between lift and gravity, the momentum and spin will allow for a longer run out.

[@sarinhighwind]

The amount of things to remember to talk about on the start must have been fun to record.

[@DiscgliderPete]

50 takes, stumbling on my own words, cutting out all the extra words….yes, it was messy:) Thank you for watching!

[@Jackleber]

Appreciate the new video Pete. Very cool channel content! Could I suggest discussing head/tail wind affecting stability as a topic?

[@DiscgliderPete]

I have big plans for that, and am currently working on diagrams to help explain it simply:)

[@ryansuter4424]

This video made me think that the less stable a disk is the less force I need to create an enough lift on the disk to counter the force of gravity.

[@DiscgliderPete]

I suppose a better way to say it would be: A little piper cub airplane takes less energy to get off the ground than a leer jet. The amount of lift they generate is dependent on different speeds and AOA. The less stable a disc is, the more the lift generated by that particular airfoil moves behind the center of balance at speed, this causing a disc to turn because of gyroscopic procession. Under-stable discs “turn” more. When rolling the discs flight lifts toward its top, if the center of the lift pressure moves behind the center of gravity, it causes the disc move towards turn, when in contact with the ground, the force on the ground causes the tail to drop lifting the nose.

[@isaknilsson71]

Hello! A nice explanation; do I understand correctly that you focus on the impact of lift only, leaving effects from low/high speed turn/fade out of this video? Would love a continuation adressing those for rollers, too!

[@DiscgliderPete]

I stated that “just because a disc is rolling, doesn’t mean its flight characteristics are negated in any way”. I did a video prior to this one explaining why discs turn and fade and and the effect of those forces with under and over-stable discs. This video was basically building on what was discussed there. In this video I’m hitting the basics of how a discs lift applies forces into the ground, which accounts for some of its curious behaviors on the ground. An understable discs center of pressure/(lift) moves behind the center of balance which would lift on the tail of the disc, but because of gyroscopic precession that force would transfer 90* in the direction of rotation and we would see the left wing lift up…. With a very overstable disc the center of pressure would stay in front of the center of balance lifting more on the nose, and because of gyroscopic procession we would observe that effect on the right wing lifting towards fade…. Thus is very interesting and complex because in both cases though the lift is towards the top of the disc, the “where the center of lift” is located would seem to be at opposition with the forces imparted between the disc and the ground. So currently for simplicity sake, sharing the understanding that the lift vector is very much responsible for a roller lifting and thus applying force to the ground, causes the “standing up” while rolling at high speed. Applying what we covered in the previous video towards this video was the intention, but I now see i didn’t make that super clear and I chose to not add more of that information into this video to avoid making a 30 minute video. Thank you for your comment, it’s valuable and I’ll try to work on being more clear and become a better communicator as I learn the art of sharing ideas on this platform.

[@isaknilsson71]

@@DiscgliderPete Wow, thanks for the comprehensive reply! I just want to make extra clear that what I wanted to communicate was curiosity, not criticism. Keep up the awesome videos!

[@DiscgliderPete]

@@isaknilsson71 of course! I love all the comments, they help me think critically about the subject matter and learn what ways I can become better at communicating ideas. Appreciate ya and thank you again for watching and reaching out. Do you have any questions or things you’d like to see on the channel?

[@isaknilsson71]

@@DiscgliderPete Ooh... well, apart from the "should I select roller discs based on glide and/or turn/fade", there are some special shots I've been wondering about. Like, does the flare skipper (backhand) go sharply left because the hit from the ground gyro-precession-snaps the nose "up" or for some other reason? And why doesn't a disc with lots of glide (lift) go straight into the ground when thrown upside down? Do discs have lift in both directions somehow? :P

[@alex9548470]

Pete Ulibarri out here doing the Lords work 🙏

[@DiscgliderPete]

🙏

[@JasperWhannell]

What’s the ideal angle to land at? Ideal stability for FH vs BH rollers?

[@DiscgliderPete]

That question is kinda the same question as “ what is the ideal angle for a hyzer?”…. Really it is very dependent on each specific shot, the terrain, the grass depth, the wind, etc. I use a Discraft Heat for 99% of my rollers. In the air, if I throw it on a hyzer I can flip it into a turnover, that will fade at the end, or less hyzer and it will flip up and the over and continue turning to finish right. I like to think of 45* as a starting angle to land the disc, let’s consider that the equivalent to a flat throw in the air. Just like an air shot, the rest is dependent on how fast or slow the disc is thrown and how flippy or stable it is.

[@bobbybobman3073]

Yeah I don't know of that helped me throw better rollers either, but it was cool to see. Also also my discs are suddenly more flippy than they should be. I hear rpm tends ro improve linearly with speed, up to about the 65-70 mph ball park. Then it tends to tail off pretty considerably, if youre at 1200 rpm at 60 mph you might only be at roughly say 1300rpm at 70mph. Are there any discs that are reliably stable with lots of forward push. Destroyers seem to be too much for me new at least, and even something like an mvp photon is very beefy. Ive throw over 500' with a shryke, pharoah, and prodigy d3. But they are not at all predictable flights. If I nail it, and hit all my angles perfectly I bomb with them but If my angles are wrong slightly its terrible. But a photon is hard to reliably get out to 400'.

[@DiscgliderPete]

Thank you for your comment. Yea, this wasn’t intended as a “how to”, but rather a “isn’t this fascinating” video. :) If you are throwing around 400’ with a stable disc, you probably are throwing in the neighborhood of 56-60mph. Your experience is relatively normal. Flippy discs fly farther with the correct angles, but are also more unpredictable. What you may need more of is Spin. That’s what makes disc “push forward” like you stated, the other would be a good nose angle. Nose angle is easier to correct than increased spin. However, both take work to get consistent. Gannon buhr, Paul Ulibarri, and a select few others have a spin rate that pushes over 1600rpms. Gannon throws in the 70+mph range and Paul in the mid 60’s. I know guys that throw in the upper 50’s with 1400rpm range. A lot of that is in the wrist and grip, and is a hard metric to get others to increase. I don’t have a magic coaching tip to increase it other than engagement of the wrist at the hit point. That fine motor and fast twitch muscle activation takes a lot of time to get trained. Think how long it would take to become proficient in writing with your off hand. It simply takes time. All this to say, there are a lot of excellent discs out there, but not one of them throws itself. You’ve got to find a disc that works with where you are at currently. For me, I’ve been absolutely blown away by how far and how straight the Discraft Athena has been flying for me. It’s flying nearly as far as my nukes, while still remaining stable in high speed flight. So hitting 400’ with both, but controlling the landing angle better with the Athena.

[@allenfrost2148]

I’ve wondered about the aerodynamics of domed discs which I prefer over flat discs that my friend prefers. How does the degree of done affect flight?

[@allenfrost2148]

Never mind. Just watched your next video. ❤

[@DiscgliderPete]

It’s a very great question! Here is general understanding and running theory on that flat vs. domed topic, it’s my copy and pasted answer from several other places I’ve had the same question. Thank you for watching! The flat versus Domey argument has always been a little comical to me, because some guys think the flat disc are more stable and the domey are under-stable, and other guys think that Domey are over stable, and the flat one stable. Domey discs tend to have more glide than flat discs. Let’s assume both have identical parting lines. There are many components to understand it all, from lift, to drag, and even release angle. My personal observation is this: I think the varying opinions at a result of a grip issue. Some guys love to throw flat discs while others prefer domey, and those are the camps they tend to stay in. When a person who loves throwing flat discs, throws a domey disc, they tend to believe it’s more stable. When a person who loves domey discs throws a flat disc, they tend to believe it’s under-stable. Hold a flat disc in your hand, be exact at how it settles into your hand, like you are ready to throw in the power pocket position, notice how the edge of the disc closest to your chest looks. Now grab a domey disc of the same mold, Hold it in the same exact manner as described above. I believe that you will observe that the domey disc settles into the hand in such a way that the edge closest to the chest will be lower by a 1/4” or so. This result is because the domey disc is slightly taller and the thumb sets higher over the flight plate pushing the edge closer to your chest down slightly, so what feels “normal” is a slightly different angle between the two disc, and would leave the domey, disc on more of a hyzer angle out of the hand compared to the flat disc. Thats my observations and opinion after years of observing the two groups and various opinions.

[@timeandspacevintage3380]

Disc golf bill nye

[@samgustafson308]

I don't think this is it. Your reasoning doesn't explain why a disc thrown on cut would stand up and even turn over. It just explain how the front and back of a disc would move. Here's how I think about it. A roller changes roll angle the same way that an air shot changes roll angle. The disc is experiencing a pitching moment because the lift is not perfectly centered. It is either a little forward or a little rearward of the center of mass. When the disc is nose down, the center of lift is rearward and you get high speed turn (I know you already know this :) ). An air shot will transition from nose down to nose up as gravity takes over and it starts to descend. Hence, low speed fade. The cool thing about rollers is that they are always traveling nose down. The angle of attack is always zero. That's just how a disc rolls. That means it is experiencing a turning pitching moment throughout its entire flight...or roll. That's what makes a disc "stand up". A centered lift vector as you explain it here, would not make a disc stand up. This also explains why overstable discs roll straighter than understable discs. They experience less of a pitching moment at zero angle of attack. It takes them a lot longer to stand up. Understable discs turnover like crazy, hence they stand up and curl really easy. Hope that helps!

[@DiscgliderPete]

To be fair, and to avoid a 25minute video, I did explain that just because a disc is now rolling, it doesn’t negate its flight property’s….. its flight property’s are a major component to its turn and fade, which also is a component to a great roller. How much turn a disc has in flight is determined by its stability or under-stability in flight characteristics. Under-stability is when the lift force moves behind the center of balance, and because of gyroscopic precession, causes the left wing to lift which we observe as flip/turn (rhbh). Over-stable discs don’t “turn” in flight, yet we do observe them “turning over” or standing up towards the top while rolling. Part of this is because of it interacting with the ground, and the fact that even though it’s “stable” in flight with the lift force remaining at or in front of the center of balance, it is still generating meaningful lift, that lift IS upward against gravity, and while on the ground the UP force of the lift is then imparted against the ground, thus the ground “pushes” back against the disc, up against the discs gravity and sideways against the force of lift the disc is generating. The force imparted against the lifting vector against the ground is responsible for forcing the “tail” of the disc down because of precession, and thus the “nose” of the disc lifts as a consequence. If the disc is rolled on an angle where lifting force is not greater that the gravity vector, the disc will remain cut…a secondary force would also be observed as the discs turn In cut is increased, it would also increase its force “outward” due to inertial velocity, this would also be observable as a similar effect to the lifting force pushing back against the lid/top of the disc, and the discs curve to want to straighten out. All very complex, but in the video I’m trying to super simplify it. Thank you for your comment and insightful observation.

[@samgustafson308]

Overstable discs *can* turn, they just don't for most human throws. That's because even if they are released with the nose down, they don't spend much time with a negative or zero angle of attack. The disc quickly enters the glide phase where the angle of attack is positive. But nearly every disc will turn at zero angle of attack. You have to get to something weird like a Tilt for this not to be the case. I understand trying to keep the explanation simple, but I feel like aerodynamic turn is the main factor at play in a roller. It explains why and how fast a disc stands up. The forces you talked about are a factor in the "flight" but they are a minor factor.

[@DiscgliderPete]

Yes, An over stable disc can turn depending on airspeed and spin velocity, but this isn’t a discussion about how a nuke flys and rolls if I threw it vs. Anthony Barela, because we know between us whose would flip more……but for all intents and purposes an over-stable disc that’s rolling under normal airspeed and groundspeed circumstances is still over-stable. It would in fact tend to stay as a “cut” roller because of its flight properties, as I stated in the video “when the angle of cut is more than the ability of the discs lift can overcome”. Meaning, the lifting force acting on the disc would be ahead of the center of gravity, this would cause the discs right side to want to lift because of precession, normally driving the disc in flight towards fade, this is coincidentally the side of the disc in contact with the ground while rolling. This is an interesting point to ponder, because the airspeed would be driving the disc towards fade or cut while rolling, while the contact with the ground would be causing either the tail to lift causing the tail to move towards cut, or drop causing the discs nose lift towards turn. This due to its lift and stability. The discs contact with the ground and its subsequent forces tend to cause the disc to fly differently. For me, a Heat is under-stable, for someone else with a lower arm speed it may be over-stable…. This then would be a conversation about flight numbers and their subjective meaning of their characteristics in relation to each person’s arm speed. An important factor I believe is how the spin increases by at least double when it becomes a roller. This increases its gyroscopic stability by 50%, and increases its resistance to off axis torque also. So its resistance to off axis torque is increased along nearly its entire flight So to sum up. Yes you are correct as far as I can tell in that a discs speed and flight characteristics are a major component in understanding rollers, but the added physics of the flight characteristics against the ground forces, is another large component. I’m not a physicist, like I stated in the description. I’ve sought out those that are and are smarter than I am to bounce ideas off of and try to gain understanding from them. This is a simple breakdown of what we’ve discussed and understood thus far. I humbly will continue to learn. Thank you for your comments, they definitely help move towards deeper understanding and critical thinking.

[@JustinTarahomi]

Love all this!!