It illustrates an acceleration / deceleration profile and you can see the individual contribution of elbow (in blue) and wrist (in yellow).
Merlin’s comment and graph showing the largest angular velocity in the cast was due to wrist rotation gave me some second thoughts about the rotation center flow I have measured for a number of good casters. If the maximum rotation was due to rotation of the wrist, then you would expect the rotation center of the rod to be located near the wrist at around MRF.
However, in the casts I have analyzed the rotation center at the maximum angular velocity (MAV) point has been near the elbow not the wrist. What is going on to explain this difference?
To resolve this question I thought I could simulate a cast using different velocity profiles. Based on Merlin’s plot I selected this candidate profile that assumed a proximal to distal kinetic linkage in the angular velocities as shown below.
You can see that with this simulated profile when the rotation velocity for the elbow rotation was near its maximum the angular velocity for the shoulder and wrist were near zero. Thus you would expect the rotation center flow for this set of velocities would start at the shoulder, move to the elbow, and finish at the wrist. This would make for a nice well defined test case to check out my rotation center calculations.
The problem with this set of curves was that it resulted in an impossible rod motion. There was enough angle change in the elbow (62 degrees) that the forearm was pointed towards the ground at the end of the cast. Even worse the angle change in the wrist rotation was about 95 degrees, so that this “gumby” caster would have to have a wrist that could rotate like Linda Blair's head in the Exorcist. A good test candidate gone bad.
So how does a “wrist caster” use a combination of shoulder, elbow, and wrist rotations to make a cast?
Here is a three rotation axes model of the cast that will gives a geometry than can be used to covert the angular velocity data to an animation of the cast.
To use this model it is a simple matter to integrate the angular velocity data to get the angle change for each of these rotation points (shoulder, elbow, wrist). By adding in an integration constant value to get reasonable initial angles you can then compute the stick man’s joint positions and angle changes to simulated the motion of a cast.
Using the data Noel Perkins collected on a representative “wrist cast” you get this set of angular velocity values that Merlin showed earlier.
This data can then be used in a MATLAB animation routine to get this stick figure representation of the cast. You can see the angle between the rod butt and the forearm in this cast varied from nearly 90 degrees as the elbow is lifting up to around 40 degrees at the end of the cast. That 50 degree range is about the maximum change expected for a combination of normal ulnar (30 deg) and radial(20 deg) deviations.
How does that “wrist” style compare to an expert’s? Here are the measured values computed for the change in the shoulder, elbow, and wrist rotations that Chris Korich used in this accuracy cast.
From this plot you can see that the angular velocity added by the wrist rotation in this cast was much smaller than the values for the shoulder and elbow rotation.
Chris thinks it is important to use the big muscles in the shoulder and arm to enable the caster to make a sustained set of casts in tournament competition so as to avoid muscle fatigue. In windy conditions participants in the dry fly game can false cast more than a 100 times in the 8 minute time limit for that game, so using an efficient style is an important consideration for tournament casters.
As a result you will rarely see a “ wristy” casting style in top level tournament casters.
Here is the stick man representation of Chris’ accuracy cast. You can see there is very little angle change between the forearm and the rod butt in this cast so it is very unlikely the wrist would get tired of making repetitive “microsecond wrist” angular accelerations in this style of casting.
These plots show that different casting styles can use markedly different rotation profiles, and thus there is no general rule that the elbow or the wrist will be the source of the maximum angular velocity in a cast.
However, just based on the strength of the wrist in the radial/ulnar orientation, I would expect that most good casters like Chris would get their maximum rod rotations rates from their elbow and shoulder, not the wrist.
Gordy
"Flyfishing: 200 years of tradition unencumbered by progress." Ralph Cutter
You gotta IC center plot for that cast? I could really use it.
Bob,
For what it is worth, here are the IC variations for the "wrist cast".
You will be able to make more sense of this plot by looking at the flow of the red asterisk in this animation video.
While in Vimeo you can see the I.C. flow for the non-realizable "Gumby" angular velocity cast that was described in the introductory post and shown below:
You can see that with this simulated profile when the rotation velocity for the elbow rotation was near its maximum the angular velocity for the shoulder and wrist were near zero. Thus you would expect the rotation center flow for this set of velocities would start at the shoulder, move to the elbow, and finish at the wrist. This would make for a nice well defined test case to check out my rotation center calculations.
Much to my relief this test case shows that the routine I am using to calculate the I.C. flow for the rod rotation is giving the expected result.
Gordy
"Flyfishing: 200 years of tradition unencumbered by progress." Ralph Cutter
That all makes perfect sense to me. Looking at Chris's accuracy cast, it is the type I have seen countless times by fellow casters on small streams. I looked in a mirror at my humble casting stroke and compared it to Chris's. I keep my wrist straight like he does but the rod is more parallel to my forearm than his. I also don't bring the rod as far down as Chris. In short, I use less shoulder and more elbow. I think I should have used an aproximation at the elbow rather than a foot below the rod but on it's centerline in those early calculations. It was the best guess I could make at the time.
All this work you are doing is really adding to our knowledge of casting. I think it is far more insightful and productive than coming up with, IMHO, overcomplicated ways of helping poor average joe pick a rod.
Till my dying breath, God hope its not soon, I'll think that ERN and MOI (or frequency if you must) gets you 90% of the way there. With those two numbers, I could narrow the rods I would have to cast to find one I wanted to use by a big big bunch. But that is just me.
Gordon,
Very ambitious undertaking, given all the different degrees of freedom of movement in our joints. Wish I had a greater background in anatomy to be of more service.
IMO the further you move away from the core the higher the velocity with a subsequent loss in torque.
I am a wrist caster and use my wrist in multiple planes depending on the cast being executed. Roll casting is almost all wrist, very little elbow and no shoulder except to anchor. Tip casting is more for your accuracy cast where velocity is not required, more single plane control. Shoulder comes into play for greater distance especially at the beginning of the forward stroke. This is followed by the elbow and finally the wrist, as you've stated.
Excellent work
One question if the above cast is acceleration, why are the majority of the figures positive. Decel should be negative values and equal the accel. Looks more like a velocity curve with all the graph as positive values. But the velocity shouldn't dip to zero and then climb.
One question if the above cast is acceleration,
and
Looks more like a velocity curve with all the graph as positive values. But the velocity shouldn't dip to zero and then climb.
Eugene,
Look at the dimensions on the y axis again. Those are angular velocity curves not angular acceleration curves.
The dip to zero and positive increase in the angular velocity of the rod is due to the rebound of the rod as it returns from MCF. That is a very common signature, and shows up in nearly all the casting analyzer graphs you see of good (and not so good) casters.
Gordy
"Flyfishing: 200 years of tradition unencumbered by progress." Ralph Cutter
very interesting stuff. It would be very interesting indeed to compare an accuracy stroke to a distance stroke. I'm sure that the latter will see more wrist utilised. I'll try to get something over to you next week if you want?
very interesting stuff. It would be very interesting indeed to compare an accuracy stroke to a distance stroke.
Paul,
In order for the angle change in the rod to be the sum of the angles for the shoulder, elbow, and wrist rotations, it is necessary for those rotations to be in the same plane.
That was true in Chris' cast, but because of the continuous plane changes that go one with the rotations applied in a distance cast, I don't know how you could digitized 2-D video data to come up with accurate 3-D vector rotation data.
I'll try to get something over to you next week if you want?
More data is always good, so it would be good to see it.
The point of this analysis is that casting does not necessarily have a proximal to distal kinetic linkage as it does for most throwing motions. The wrist may or may not be the joint that provides the most angular velocity depending on the caster's style.
As long as the rod rotates about a reasonably horizontal axis the rotation center calculation should point to the joint that is providing the most rotation at a given point in time. You can see that rotation center flow effect in the "Gumby cast example". In the distance casting styles I have measured, the rotation center is generally near the elbow at the point of maximum angular velocity so it would be interesting to see if that is the case for your style as well.
The strength of the elbow is much higher than the strength of the wrist in making rotations in the radial/ulnar plane. The range of motion of the elbow is also much larger than the 50 degrees that is possible with the wrist, so from a force over distance distance standpoint I think the elbow has more potential to apply more work energy to the line as well.
Gordy
"Flyfishing: 200 years of tradition unencumbered by progress." Ralph Cutter
All this work you are doing is really adding to our knowledge of casting. I think it is far more insightful and productive than coming up with, IMHO, overcomplicated ways of helping poor average joe pick a rod.
Words of advice. Don’t poke the bear, and be careful whose ox you gore.
I have been following the activities of this mutual admiration society
Way cool! Just amazing, Spectacular work going on here.
Very ambitious undertaking Excellent work very interesting stuff.
and am trying to figure out what it all means.
It seems to me, and probably any individual who ever considered the subject, if one wants to cast, one needs to use three sets of muscles, arm, elbow, and wrist. Also, the stronger the combination and coordination of these muscles, the more distance can be attained. Please tell me how mathematically demonstrating this is more insightful, productive or useful than what every angler knows a priori.
I will grant the participitans derive great joy and pleasures from their mental masturbation, and more power and pleasure to them. But don’t try to tell me “proving the obvious” is productive.
By the way, if you really want maximum distance, you need a rod, and the CCS can help you choose the one with the maximum loaded frequency. :p
I think with the finger grip/cradle grip that I utilise I would expect that most of the rotation comes from the grip, not the elbow. After all the rod rotates through 170 or 180 degrees, while the elbow during the Casting Stroke (excluding Slide) rotates through only about 90 degrees during this time.
I think with the finger grip/cradle grip that I utilize I would expect that most of the rotation comes from the grip, not the elbow.
Paul,
Just looking at your videos, I would agree with you.
Who was the kid in the second video? That stiff wrist style is very similar to Chris' accuracy stroke.
Unfortunately the 30 fps frame rate in those videos is too low to get a meaningful rotation center plot. If you can find something taken with your high speed camera from the casting arm side I will be able to do a similar analysis by digitizing the shoulder, elbow, wrist, and rod angle positions to get the corresponding angular velocity values.
That would confirm your feeling that most of the rotation is coming from the wrist in your casting style.
After all the rod rotates through 170 or 180 degrees, while the elbow during the Casting Stroke (excluding Slide) rotates through only about 90 degrees during this time.
And that shows that to get 90 degrees of rotation out of the wrist it has to rotate out of the radial/ulnar plane. You are no doubt using some wrist pronation to get that kind of angle change, and that will put some twisting rotation on the rod while is it unbending.
As described here top tennis players use a lot of wrist pronation to increase their racquet speed just before impact in their serving motion.
This is where Tom's two axis rotation velocity sensor would provide some very interesting data on the timing of that twisting effect.
That twist is a likely candidate for producing the the horizontal "tail" you and Bernd are discussing in the distance thread. However, I do not know why hauling at the same time would produce an even bigger effect.
This is just more evidence that there is no one best way to make a cast. As noted earlier:
The wrist may or may not be the joint that provides the most angular velocity depending on the caster's style.
Gordy
"Flyfishing: 200 years of tradition unencumbered by progress." Ralph Cutter
I'll try to take some high speed video of both styles as they are now. It would be an interesting comparison. I know that for the accuracy the rod rotates at the beginning of the CS, whereas for the distance there is a slight delay and the rotation acceleration is held back until as late as possible during the CS.
They are not interchangeable for distance and accuracy. I know Steve Rajeff says the same because I heard him state exactly the same thing 6 years ago. In fact that's how I learned it!
Don’t poke the bear, and be careful whose ox you gore. 