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-   -   OAT is a stupid concept (https://www.dgcoursereview.com/forums/showthread.php?t=85598)

 Dave242 03-28-2013 03:13 PM

OAT is a stupid concept

OK....the title is trolling for a reaction. :D

But, if you look at the physics of throwing a disc, you impart almost no torque (rotational force) on any axis of the disc except revolving around the Z axis (the injection dimple in the middle of the disc).

OAT means Off-Axis Torque. It means your throwing motion is imparting spin to the disc in an end-over-end manner (or side-over-side).

If you compare the forward velocity and on-axis rotational velocity imparted on the disc at release, it will absolutely dwarf any rotational velocity that is off-axis. The only thing you see as a result of OAT is wobble or flutter. OAT is almost completely immaterial to how a disc flies.

OAT is an inaccurate term that needs to go. What really needs to be talked about is the plane of the disc upon release (or the "hit").

Or....do I misunderstand what OAT is?

 Carnavas 03-28-2013 03:18 PM

I was thinking it was if some part of your limb kind of moves off the flat plane upon release, causing the disc to not release completely flat?

 jrawk 03-28-2013 03:18 PM

copy/paste from my post in the feldberg video thread:

There is more to OAT than just verticle axis wobble. There is also horizontal axis OAT.
Picture the disc rotating flat without flutter... but instead the axis is not on the center of the disc. Think of a hammer being thown. The axis is not on the center of the handle, it's closer to the massive end. Or, think of the design/shape of the Aerobe Epic. It does not spin on center axis until it flattens out.

EVERY THROW has a brief moment of horizontal axis OAT because we hold the disc with one hand.

Probably not the best term, but neither is snap, and that will never go away.

 Carnavas 03-28-2013 03:22 PM

It should always rotate around it's center of mass, and in a normal circular disc, the center of mass will be the center of the disc. Right? So as soon as it is no longer part of the system that is your arm, the axis will always be the center, unless there is mud or you cut a huge chunk out.

 AndyJB 03-28-2013 03:31 PM

Wobble and Flutter I use for two different situations. Wobble is OAT (or what people call OAT for the sake of argument here) and Flutter I use to describe what happens in a strong headwind or when you don't get a disc up to speed. What does my terminology have to do with the discussion at hand? Nothing, I'm just bored.

 Toro71 03-28-2013 03:37 PM

Quote:
 Originally Posted by jrawk (Post 1924555) copy/paste from my post in the feldberg video thread: There is more to OAT than just verticle axis wobble. There is also horizontal axis OAT. Picture the disc rotating flat without flutter... but instead the axis is not on the center of the disc. Think of a hammer being thown. The axis is not on the center of the handle, it's closer to the massive end. Or, think of the design/shape of the Aerobe Epic. It does not spin on center axis until it flattens out. EVERY THROW has a brief moment of horizontal axis OAT because we hold the disc with one hand. Probably not the best term, but neither is snap, and that will never go away.
A different axis would be if you flipped the disc like a coin into a wishing well. You may be thinking off-center axis, but the disc won't fly that way...unless it's an Epic.

 Toro71 03-28-2013 03:43 PM

Quote:
 Originally Posted by Dave242 (Post 1924538) OK....the title is trolling for a reaction. :D But, if you look at the physics of throwing a disc, you impart almost no torque (rotational force) on any axis of the disc except revolving around the Z axis (the injection dimple in the middle of the disc). OAT means Off-Axis Torque. It means your throwing motion is imparting spin to the disc in an end-over-end manner (or side-over-side). If you compare the forward velocity and on-axis rotational velocity imparted on the disc at release, it will absolutely dwarf any rotational velocity that is off-axis. The only thing you see as a result of OAT is wobble or flutter. OAT is almost completely immaterial to how a disc flies. OAT is an inaccurate term that needs to go. What really needs to be talked about is the plane of the disc upon release (or the "hit"). Or....do I misunderstand what OAT is?
As I understand it, IF I understand it, this is basically right. but it wouldn't have to be 90 deg off-axis to be off-axis. I think someone on here described it once as, imagine you're spinning a quarter on a toothpick with your finger. If you don't spin exactly perpindicular to the toothpick, you're applying some off-axis torque, causing in this case the wobble.

I'm not sure I'm grasping what you're calling the disc plane vs. release angle.

 mashnut 03-28-2013 03:43 PM

Quote:
 Originally Posted by Dave242 (Post 1924538) OK....the title is trolling for a reaction. :D But, if you look at the physics of throwing a disc, you impart almost no torque (rotational force) on any axis of the disc except revolving around the Z axis (the injection dimple in the middle of the disc). OAT means Off-Axis Torque. It means your throwing motion is imparting spin to the disc in an end-over-end manner (or side-over-side). If you compare the forward velocity and on-axis rotational velocity imparted on the disc at release, it will absolutely dwarf any rotational velocity that is off-axis. The only thing you see as a result of OAT is wobble or flutter. OAT is almost completely immaterial to how a disc flies. OAT is an inaccurate term that needs to go. What really needs to be talked about is the plane of the disc upon release (or the "hit"). Or....do I misunderstand what OAT is?
The plane of the disc is important, but if that doesn't match the plane you're pulling through on you have issues. That most often happens when rolling your wrist as you throw. It causes wobble, decreases distance and can make for unpredictable flights if you're not in control of it. Sure, that torque is a small percentage of the total torque applied, but I think it's disingenuous to say it has almost no effect on the discs's flight.

 Dave242 03-28-2013 03:44 PM

Quote:
 Originally Posted by jrawk (Post 1924555) EVERY THROW has a brief moment of horizontal axis OAT because we hold the disc with one hand.
Yeah....if you think of it that way, the axis you are torquing at the moment of release is very close to the point on the rim directly across from your pinch point (since you are impeding your grip/pinch point's forward velocity while the rest of your disc is moving forward.

The only way you can get on-axis torque is some goofy wrist curl and arm motion that has a radius equal to the disc. :confused:

OAT is a dumb term.....even dummer that it sounds all scientificky yet manages to get the science all wrong.

Who even coined the term? It is only in the last couple years on DGCR that I have seen it (not like I go a lot of other places and read about throwing mechanics).

 Dave242 03-28-2013 03:50 PM

Quote:
 Originally Posted by mashnut (Post 1924606) The plane of the disc is important, but if that doesn't match the plane you're pulling through on you have issues. That most often happens when rolling your wrist as you throw. It causes wobble, decreases distance and can make for unpredictable flights if you're not in control of it. Sure, that torque is a small percentage of the total torque applied, but I think it's disingenuous to say it has almost no effect on the discs's flight.
Normal wrist roll does not cause noticeable wobble. You would have to really intentionally flick/twist your wrist hard to impart wobble that way. An unclean release caused by the disc hanging/sticking on your finger/s causes the visible wobble.

The problem with wrist roll as you correctly point out is the plane of the disc on release. Off-Axis Turn of your arm gets your wrist to roll.

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