Landracing Forum
Tech Information => Technical Discussion => Topic started by: olepaw on March 24, 2012, 08:12:16 PM
-
This is several questions in one. Is it a good idea to mount the parachute in line with cam shaft of engine? Building 87 Firebird. Is the structure of the rear bumper bar strong enough to support the force or should it be tied to the cage of the chassis?
-
This is several questions in one. Is it a good idea to mount the parachute in line with cam shaft of engine? Building 87 Firebird. Is the structure of the rear bumper bar strong enough to support the force or should it be tied to the cage of the chassis?
1. A good rule of thumb is cam height is close to CG so that is a good height to mount the Chute anchor line.
2. Bumber bar may not be strong enough, I would not trust it to mount anchor line,, I would mount to chassis or cage crossmember...
3. The bumper area may be strong enough to mount the chute pack, but not the anchor line.
Good Luck,,
Charles
-
Look at attaching the tow line attachment point on the push bar. Many are done this way.
-
Here's a link to the formula for finding the CG. Wayno http://www.longacreracing.com/articles/art.asp?ARTID=22
-
thanks i'll check, that all out.
-
When I built my 53 Studebaker many moons ago, I mounted the tag line below the rear bumper.
Once I got the car to run over 200, when I pulled the chute it would pitch me forward and the car wanted to get loose at the same time.
A few years back I moved it up to camshaft centerline by building a bracket off of the push bars as Glen spoke of.
This raised the tag line mount 8" higher and the results are amazing.
The hit of the chute is firm but doesn't pitch the car (or me) and the car never wiggles at the hit.
It is a good starting point but you ought to talk to guys running simillar vehicles to yours.
They can share their experiences with you and save you a lot of work. Land Speed Racers, unlike most other motor sports, do share knowledge and tips with each other. Bob
-
yea i know about sharing , we used to race circle track , and if you were fast , it was mind game time. . i' done with that.
-
This is several questions in one. Is it a good idea to mount the parachute in line with cam shaft of engine? Building 87 Firebird. Is the structure of the rear bumper bar strong enough to support the force or should it be tied to the cage of the chassis?
Some say from camshaft [because its figured to be close to center of gravity on most cars without a lot of scaling and math] and in line with center of parachute when open. Others say at least camshaft height.
Check out our 222 Camaro under ''Getting ready for Bville'' in Build Dairies page 110 and the build is the 3rd from top.
Shows how chute pull is mounted. cam height is about 17'' in front of motor and back ot tube were cables come out of bumper is 20''[ aproximate, no water in big intercooler tank or water tank]
No problems when hitting chute and I opened both by accident at over 275 mph.
Chutes are top fuel- Funny car 12 ft.
JL222
-
In 1996 Jim Deist told me 30 feet back from CG, 7 feet above the ground, pull a line with a string from your vertical and longitudinal CG, where the string "exits" the car is the best pull point. Put the anchor loop on a roller to prevent friction break as the line snaps into pull. It worked perfect every time.
He said the 7 foot number was due to chute interaction with the ground.....not a good idea.
This is from memory, folks, and the 30 foot number is a little fuzzy...might have been 35.
Someone please correct me if I'm wrong. Thanks!!
Regards, JimL
-
Check out Wolfe Racecraft- they make 4th Gen chute mounts, maybe give
you an idea of how to best build yours. Ours is camshaft height, it doesn't
kite, deploys clean every time.