Bonneville Parachute

[Nexxussian]

I'll need a parachute for Speed Week 2011 as the record got upped in 2010 ( ~179, G/GMS Bonneville Bugeye, congrats guys ).

I would like to have DJ safety make me one, however I have some members of the team lobbying for "economy".

Specifically they suggest I get one from Summit, Jegs, etc for a dragster.

I have asked people that know in person I have asked on a few other forums, and that sounds like a bad idea (as I expected).

However I haven't run a parachute on anything, so it's difficult to get some people to listen to me.

Those of you that have run a 'chute, help me out, what reasons can I use to, well, reason, with the doubters?

[Bville701]

For one DJ Safety will ask you many questions to make sure the parachute you get from them is the right size and length, and they are usually at Speed Week every year so if you run into any issues you can talk with them directly.   

[Cajun Kid]

Whatever chute you decide on, DJ, Deist, Jegs, Summit, Stroud LSR, Simpson etc,,, make sure you tell them the weight, speed and show them a picture of the car and also make sure the chute pack is mounted and the anchor line is attached at the right height.

Charles

[Tman]

Ironic? that you got 3 times the replies on the HAMB in less time. 

[Dynoroom]

But is the information from the Hamb any good?

If you do a search you will find plenty of information on 'chutes

[Avanti Kid]

I bought my last chute just before Jim Deist died, I asked him to design a chute with longer shroud lines and a bigger bag to make packing the chute easier.  Jim had a software program to help with the requirements for my chute, he asked me how much my car weighs (4,300lbs) and how fast will I go? Told him we planned on 220mph. From this data he manufactured my chute which has worked great so far at speeds of 216mph and very stable.  Yes, its very important where the chute shroud lines attach to the car, if attached too low it will pull the cars front wheels off the ground when it deploys; if attached too high it will lift the rear wheel off the ground. So you need to find the sweet spot for good deployment and keeping the car stable during shut down. Also short wheel base cars like my brother's Pantera, you have to deploy the chute while the car is still under power, but with my Avanti (longer wheel base and better balance of ballast) I can ease off the power then deploy the chute, thus not loading the engine's connecting rods with the force of the chute opening under full power, like the Pantera needs or it will spin!! Hope this helps you some.  Dave

[bvillercr]

Like many have said before, all cars are different.  The general rule for parachute mount is at or near the cam height of the engine.  Everyone deploys their chutes different, I put the clutch in and then pull the chute after coasting a little while.

[SPARKY]

A Kid---recheck your statement about mounting---is it possible you have it backwards---

[Tman]

But is the information from the Hamb any good?

If you do a search you will find plenty of information on 'chutes

About half of the replies said ask here  It is easy to see that the shear #s of folks over there will get more activity. Myself? I am digging through old threads here wearing out the search funtion trying to get answers to some of my Qs............great reading. Trent

[Nexxussian]

Thanks guys, lots of pearls of wisdom here.

I appreciate them, but, I'm looking for reasons I can quote to those that are telling me to cheap out and why it is I want a custom 'chute instead of some "drag race special".

Thank you all.

[jimmy six]

This is from my experience and not from any manufacturer.. My car runs in the same speeds you need to go and weighs approximatetly #3000. I personally like a tri-form chute because it can easily be choked down as your speed increases. A long time LSR race told me to be very careful with a cross-form chute over 200 and I trust his experience. My 3 lines are currently choked over 1/2 way and I stop fine at El Mirage and Bonneville. Good Luck............

[MAYOMAN]

SPARKY is right - the scenarios above regarding chute line mounting is reversed.
Ideally, the parachute lines will be positioned so they pull through the center of gravity of the car. Typically, the canopy will run inflated about one foot above the ground, so the center point of the inflated canopy above ground can be determined. Drawing a straight line from the CG to the canopy center point you will determine where the mounting point of the shroud lines should be above the ground.
The X and Y position of the CG can be determined with scales and a little geometry.
Mounting the anchor point too low can lift the rear wheels, upsetting the car.
Mounting the anchor point too high will unload the front wheels. If the body also pitches up in front it could cause a blowover, so the correct position needs to be determined carefully.
It probably would be a good idea to check the reaction of the car to the parachute deployment at progressively higher speeds rather than relying on plane geometry calculations.
Good luck!

[ol38y]

Thanks guys, lots of pearls of wisdom here.

I appreciate them, but, I'm looking for reasons I can quote to those that are telling me to cheap out and why it is I want a custom 'chute instead of some "drag race special".

Thank you all.

Maybe show them the video of the Lambo at Texas...  BTW, who's driving the car? I would think they should hold the most sway. JMO

[Avanti Kid]

Thanks guys for the corrections on where to mount the chute and what the outcome could be, sorry on getting it backwards!!  Dave 

[MAYOMAN]

There is a handy CG height calculator available at http://www.longacreracing.com/articles/art.asp?ARTID=22.
You just gather the data and plug in the numbers. Also, you can calculate the horizontal location from the front axle centerline as well.

Again, this is a starting point that needs to be validated running the car.