Sheehan took this proposed "fourth jump" fairly seriously ...
Before reading the paper, I got the impression that it was a "theoretical" scientific paper without any intent of ever actually performing this event in track meets or elsewhere.
After reading it, I see that sure enough, it's loaded with scientific equations, where he predicts "catapults" in the 18m range, and that Sheehan himself has actually self-tested his theories about how this event would work.
But other than his speculation of why this event is not yet popular, there is no hint that this is anything but a serious proposal of a serious new event.
One might ask why this event has not been pursued up to now. Its absence can probably be traced to the lack of large, safe landing pits in the late nineteenth and early twentieth centuries that would have been necessary to contest it.
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As catapulting requires relatively large pits, it did not find its way early into the canon of track and field events, was not instituted into the early Olympic Games and, therefore, was never seriously pursued. Basically, its absence appears to be a historical accident.
He appears oblivious to the "Pole Vault for Distance" and "Canal Jumping" that have been documented in this thread. Instead, he regards this as a completely new event.
He refers to the "Catapult" as "the fourth jump" because there's two vertical jumps - one with (PV) and one without (HJ) the aid of a pole, and only one horizontal jump (LJ) - without the aid of a pole. His proposed "catapult" fills this gap in the jumps. I don't think he's oblivious to the TJ, he seems to consider it as just another horizontal jump without a pole.
Sheehan proposes that Catapult technique would consist of 5 general phases: (1) Approach (run-up), (2) Pole bending, (3) Pole unbending, (4) Push-off and release, and (5) Landing.
These phases follow traditional fiberglass pole vaulting (for height) technique fairly closely. It's the differences that I find intriguing!
During the "Pole unbending" phase, he proposes this:
As the pole unbends and the jumper descends, the elastic potential energy of the pole and the catapulter’s gravitational potential energy are converted back into the kinetic energy. During this phase, it is conceivable that the vaulter could continue to increase his mechanical energy via reaction forces from the ground.
For instance, one can imagine the vaulter pulling down on the pole then letting up on it in a resonantly sequential fashion; that is, to resonantly pump the pole so as to increase his kinetic or gravitational potential energies. Resonant pump of this sort is well known and is used in a number of athletic endeavours, for example, to drive a child’s swing; to ‘pump’ a wave in ocean surfing; and to ‘fishtail accelerate’ in skateboarding.
I can't visualize this. How would this work for horizontal fiberglass pole vaulting any different than for vertical fiberglass pole vaulting? Does this boil down to "double-bouncing"? Triple-bouncing? Will there be sufficient time for "double or triple-bouncing"? I don't think he "gets" the physics of this part of the vault, no matter whether it's horizontal or vertical. I don't think you can just
"pull down on the pole then let up on it" repeatedly. It doesn't work that way!
I do see in the "Canal Jumping" vid how the athlete balances on the pole. As he climbs it, his CoG rises, slowing the descent of the pole. This appears to give him ample time for further climbing. But with a bending pole, isn't the entire action going to be quite fast - just as in the vertical PV? There's no time for double-bouncing, is there? When I think of "double-bouncing" all I can visualize is how you bail after a bad takeoff. You hang onto the pole and it bends a second time, just before you ride it safely to the pit. But if you're in the middle of a GOOD horizontal jump, I can't see how you're going to be positioned to "double-bounce".
Sheehan then proceeds to explain how the athlete can shoot off the end of the pole - like a vertical PVer, except in more of a horizontal direction.
In the "Landing" phase, he describes 3 alternate techniques: (1) like a LJer, with 0° rotation, (2) like a PVer, with 180° rotation, (3) like a PVer, but with a full 360° of rotation. He speculates that the 3rd technique would be the most difficult to perfect, but would be the most optimal for reaching maximum distance. I think he's probably nailed this aspect of the catapult, but IMHO it's of marginal importance compared to what you do in the SWING phase. Come to think about it, he doesn't really mention the word "swing", other than the "child swing" analogy in the quote above.
... one expects experimental performances up to roughly 18 m. It is predicted that competition jumps will actually exceed this value because the catapult appears to involve less substantial accelerations and stresses than the pole vault and so mechanical energy losses and inefficiencies should be less severe. It is speculated that competition jumps might exceed 20 m, measured from take-off, or roughly 15 m measured from the plant box, the most likely place for competition measurements. This expectation should influence the size of landing pits, which should radiate outward from the catapult plant box 15–20 m, be sectored like throwing fields (~60° opening angle), and be filled with deep (~0.5 m), well-fluffed sand.
Lastly, he doesn't talk much about SAFETY. He talks about a sand-filled sector "like throwing fields". But I wonder if he really understands that what he's proposing creates a HUMAN PROJECTILE rather than an INANIMATE OBJECT (a shot put) landing in the "throwing field"?
After acknowledging early in the paper of
"the lack of large, safe landing pits in the late nineteenth and early twentieth centuries that would have been necessary to contest it", he makes no mention to a viable solution to this, other than a landing pit with "well-fluffed sand". This isn't exactly innovative. That same sand existed
in the late nineteenth and early twentieth centuries!
I pity the poor athlete that tries to train and compete in the CATAPULT whilst also competing in the POLE VAULT. The two just won't mix! In PV, you're taught how NOT to shoot past the end of the pit, whereas in CATAPULT, you're ENCOURAGED and REWARDED to do exactly that!
In CATAPULT, you need to use a SOFT pole, so that you can blow thru to project your body in the horizontal direction, whereas in PV, you need to use a STIFFER pole, so that you DON'T blow thru!
Hmm... I can think of LOTS of reasons why this will never catch on in a traditional ATHLETICS competition.
i can, however, see some potential for it as an EXTREME sport - perhaps in conjunction with a Beach Vault.
The vaulters would either land on the [hopefully] soft sand, or perhaps into the water. The entertainment value would be the huge distances that the athletes can potentially jump, and the danger factor. But it can't be so dangerous that normal, good catapults cause injuries.
Really, it's just a new twist on the CANAL JUMPING that's already done in the Netherlands!
Yeh, it's dubious, to say the least. But you know, if this event is ever held on the Pacific Coast, I'LL BE THERE!
Kirk
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