Howdy, when I was skydiving back in the 80's, I built a DAS for altitude
and loads on the chute vs time. most skydives were from a 10,000 ft in a
flat and stable freefall, with a pull altitude of 2500, average speed at
pull 114-122, parachute opening speeds between 1.35-1.55 seconds, load
cells saw 1.4 to a 1.6 G load with a diver weight of 195 lbs including
chute. one time I did a freefall by standing on my head from 10,000, speed
186 at 3000 pull.....load of 2.7 G in 1.35 seconds.....(ouch!) mainly what
I see by the data is the chute takes a certain amount of time to open,
regardless of speed, and the loads seen are mitigated by the stretchyness
of the nylon system, now we were gathering data at 40 bits a second/channel
and we had enough memory to grab 4 channels for just over 3 minutes, so we
could see the entire jump. we did 38 jumps and never had any loads spike
more than the averages I just mentioned. Now it don't mean that there MIGHT
be a spike, but it would have to be awfully fast to beat the data speed we
recorded at. I packed the chute to open "right now!" and "slow" and this
did not show much change in the data we gathered for either loads or speed
of opening.....just my opinion, but I had data to back it up.....don't ask
for it though, its' in an old 8088 with a crashed drive......
John Robinson, Mechanician
Mechanical Engineering University of Wisconsin
1513 University Ave.
Madison, Wi. 53706
608-262-3606
Current World Land Speed Record Holder
Bonneville Salt Flats
H/GCC 92 cu.in. 1980 Dodge Colt
144.396 MPH set 2000
MPS-PG 441 c.c. 1967 BSA Victor Motorcycle
95.193 MPH set 2001
Antarctic Ice Driller Oct02-Jan03
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