From: belboz@frc2.frc.ri.cmu.edu (Barry Brumitt)
Subject: Re: AAD cutters vs. pullers
Reply-To: belboz@frc2.frc.ri.cmu.edu (Barry  Brumitt)
Organization: Field Robotics Center, CMU
Date: Mon, 11 Jan 1993 22:38:56 GMT

   From: beutel@chdasic.sps.mot.com (Jim Beutel) 
   Date: Mon, 11 Jan 1993 16:58:08 GMT Lines: 40

   Hi gang,

	[ cutters vs. pullers? ]

   Having two pins only doubles the issue for me. When I am ready to buy a
   brand new rig, it will be a single pin.  In the mean time however, I feel
   it would be safer pulling the pin a small half inch back from under the
   loop. The cutter I would think, stands a fairly good chance of NOT actually
   cutting the loop. It only gets one shot at it I believe. It is not like
   cutting a steak where you can cycle the blade back and forth.....

According to the CYPRES ad, the cutter has never failed to cut a loop in any
test case. In fact, I beleive it was stated it was capable of cutting the
reserve *cable*, not merely a small peice of cloth. ! Not something you should
worry about, IMHO. However, please recall free advice is worth what you paid
for it! Oh, it won't cycle, as I'm under the impression the CYPRES uses a
pyrotechicnic charge. (The Sentinel definitely does).

   Also, if the loop is cut from inside the reserve container, such as the
   Cypres design, what are the possibilities that the loop may hesitate from
   feeding its way out..? Any delay at under 1000 feet is not exceptable.

(acceptable.)
The loop doesn't *have* to "feed it's way out. If you've ever seen a reserve
packjob, the loops is under *lots* of pressure. The force of the pilot chute
spring and all the compressed fabric (less important than the former) will
force the flap open, the pin pulling the loop behind it.


(Cross Sectional view *)
KEY:  {' = loop.} {|| = Gromets}



		   ^			
cable____________=='===      <----pin {=}
flap--------------|'|----
            ------|'|--------other flaps...
           spring  '  spring				}
                   '					} Reserve
                  (')        <----loop cutter{()}	}
                   '					}
-----------------------------bottom of container



That spring will push up as soon as the loop is cut below. The loop will
follow the pin as the flaps open and the pilot chute leaps force, anchoring
itself like a rock in the ever-thickening air, stopping you mere moments from
impact from our beloved mother earth.

Oh, a pin puller won't work if your reserve pin is bent, or if the pull force
is too high... 

I'm thinking of getting one too. Money is really the only issue. The article
in Skydiving about the CYPRES and the recent article in parachutist were most
thought provoking. Perhaps the "only pansies and idiots wear AAD's" image will
vanish from our sport someday!

Barry

(*) Hey, ASCII art is tough! God knows if this is legible to *anyone* but me. 

--
Barry Brumitt                        belboz@frc2.frc.ri.cmu.edu
RI Graduate Student                  (or) bb1v@andrew.cmu.edu
Field Robotics Center                Phone: (412) 268-7144
Carnegie Mellon University           "Who is John Galt?" $ Skydive!

Boring Disclaimer: The opinions contained herein do not necessarily
=-=-=-=-=-=-=-=-=  represent those of the FRC, SCS, RI or even CMU. 




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