| [GMCnet] Braking performance of the standard system [message #109037] |
Sun, 19 December 2010 19:39 |
Charles Aulgur
Messages: 78
Registered: March 2006
Karma: 0
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This subject sure generated a lot of discussion in the last few days,
some of it very interesting and some still showing there are still a
lot of people with questions concerning the viability of the
reaction arm system and wanting to see more testing. Almost three
years ago Rick Flanagan, myself, Jim K and some of his workers spent
two full days at Jim's place doing numerous testing on both OEM
braking systems and various configuration of the reaction arm
system. We had so many black streaks in the area adjacent to Jim's
place it got hard finding new areas to run the test. Most of the
testing was using Ricks GMC with various configurations of caliper
sizes and different types of brake pad material, both with and
without the reaction arms connected. Most of the testing was
recorded on one of Rick's video cameras and we measured the stopping
distances via tape measuring on most of the test. Rick had a device
on the rear of his coach that released a chalk marker when the brake
stop light switch was actuated and he never let up on his brakes
until the vehicle came to a complete. A lot of this video data is
summarized on Jim's web site. You can also see videos of the brake
testing I did during the develop stage on my original design on the
GMCWS web site. In my humble opinion, I don't think we need any more
testing. If you saw how Rick abused his GMC during this testing I
don't you would get many volunteers to do additional testing. I know
it sure won't be on my GMC.
There has been brake analyses published in the GMCWS tech reports and
sever people on this net have talked about their analyses, but nun of
them have addressed the negative affect that a swing arm suspension
has on brake performance. This is not something new. A patten was
issued many years ago for parallel suspension on motorcycles to keep
from lifting the front wheel off the ground during high acceleration
and is still widely used today on high performance bikes and most
independent rear suspension on todays automobiles. Reacting torque
generated my brakes or acceleration are one in the same.
Someone mention that all the energy developed during braking does
not go into slowing a vehicle. That is very true with all brakes.
The friction generated between the brake shoes/disc pads creates a
lot of heat which is lost energy and that is not utilized to slow the
vehicle. Everyone knows that the front of a vehicle dives somewhat
during braking. You can do the same simple vector analyses on the
front wheels as I used on the rear suspension. Just draw a straight
line from the tire/road contact point back to the cg of the vehicle.
This force is pointing somewhat up on the vehicle cg and if you
convert the angled force to the equivalent vertical and horizontal
force acting on the cg you can determine how much of the force vector
is utilized in slowing and how much is utilized in lifting the cg of
the vehicle. That vertical force is what is causing the front end to
dive because lifting the vehicle cg transfers more weight to the
front wheels. This is again wasted energy that is not being utilized
to slow the vehicle. This is way a sports car with a low cg has more
efficient brakes then a sedan with the same weight and brakes.
For all of you folks that don't believe all the B. S. being thrown
around about the Reaction arm (parallel linkage) but are serious
about wanting to improve the safety for your family please drive one
of the coaches with the reaction arm system installed if you get a
chance. You won't need to make a panic stop to convince you they are
worth the $5K-the seat of your pants and the feel of the brake pedal
will convince you.
Chuck Aulgur
La Mesa, CA
76 Royale with modern car feeling brakes
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