I, as all of you have been reading all of the ideas on chutes and how
they deploy etc. The thought of a shock absorbing device makes me wonder
about this due to the old saying in engineering for every action there
is a re-action. OK, the rebound must be considered in this arrangement.
True, it will assorb to a point and then the tow line will also absorb
additional shock. However when all of this absorbtion is done there is
going to be some rebound to the shock unless the reverse travel is
stopped.
It's possible the rebound could start to oscillate. How much, if any is
a question I don't have an answer to. Keeping the chute in a straight
line in clean air with the proper length tow line is something that
needs to be developed for each vehicle. As said earlier ask the chute
manufacturer giving him all of the details of the car or bike liner
first.
The other thing I see a lot of is the loop of the tow line at the attach
point to the vehicle tears through because the pin through the bracket
is 1/2 or 5/8 dia. A minimum sleeve dia. should be at least 1 1/2 dia.
This gives the loop a lot more surface area to pull on without the knife
edge effect of the smaller dia. Don't forget the heat caused by friction
as well. The sign of any fraying is a good indicator to have it checked
by the experts.
The faster the speed the smaller the chute. When we were drag racing we
were told to pull the chute under power. This is not a problem as while
the vehicle is accelerating and the chute is pull the mass of the canopy
and the risers and tow line come out at a little faster rate. If the
chute is pulled during deceleration the mass tries to stay in the chute
pack waiting for the pilot chute to get enough air to pull the main
canopy out.
There have been film studies on this and pulling the chute in the last
few feet won't hurt the speed but could make a big difference in how you
stop. But the above remarks and those on the list all have to be looked
at and given thought.
We in the timing stand see a lot of things happen to the back of the car
and when we do we tell the crew what could be causing the problem. I'm
not the expert in chute design, but I do care about safety and anything
I can do to prevent something from going wrong.
Glen ( waiting for the next lakes meet)
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