QuestionQUESTION: Hi, what is it about drag racing torque thats makes the front end lift off the ground when it takes off. Yes, I have the charger from the fast and furious on my mind haha... I know it was fake, but its still way too cool.
ANSWER: Gene,
My apoligies for being so late in answering.
Let's see if I can explain the physics behind front wheels lifting...
1) Driver steps on accelerator and lets out the clutch
2) Rear wheels begin to rotate forward
3) Since the Center of gravity is above the rear axle, as the rear tires drive forward, the body/chassis/engine are delayed in their reaction to the acceleration so they want to go backward (for every action there is an equal and opposite reaction), but they cannot go backward since they are connect to the rear axel via suspension, so they start ROTATING about the rear axel until something stops them...wheelie bars and gravity.
4) results...front wheels lift.
5) It is also due in large to the Ladder bars...but that is much to complicated to discuss here. Find a book and read up. just google "dragster suspension book" and you will find a wealth on knowledge available.
If I can be of any further service do not hesitate to contact.
Best Regards,
JQ
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QUESTION: Thank you... as a follow up, I have question in regards to the aerodynamic benefits of a cowel hood scoop... just how great is the significance of having one, and how would it demonstrate this in a wind tunnel test?
I'm studying to be an engineer, so really "I dig this stuff".
ANSWER: Gene,
I am assuming that we are still talking about Prostock 1/4 mile dragsters and not NASCAR. Fortunately I have been a part of a National Championship NHRA team and for once in my life I might know what I am talking about (LOL):
1) There is no aerodynamic advantage as the hood scoop is a significant source of drag.
2) The only purpose of the hood scoop is to redirect (at lower velocities) and ram (at higher velocities) as much air through the carb as possible. Actaully, the NHRA rules dictate hood scoop opening size and location, otherwise racers would have a much larger scoop to allow more air in the card at launch (that bing the most critical time to develop horsepower). I did the calculations once years ago, but if I remember correctly the most air that an engine can pull through the card is about 40 or 45 miles per hour. So logical follows that once the vehicle is traveling the same velocity as the air going through the carb, you are now trying to ram air instead of sucking air. At that point, the hood scoop is bad aero wise.
3) Proving this in a wind tunnel is as easy as making a test with a hood scoop, and then making a test without a hood scoop. That will show the effect to drag and lift. Or even chaning the shapes of hood scoop will show differences.
As you become a famous driver or engineer...feel free to ask questions...always happy to help.
JQ
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Behind
QUESTION: Cool, thanks... so to stay with the hood scoop for a moment, what would be the difference of having the opening in the front of the scoop as opposed to behind it near the windshield to create this vortex... here is a pic of the opening ovr the hump and in front of the windshield to illustrate:
AnswerSorry, but your photo did not transfer. Feel free to email it to jgquarles@yahoo.com
Several factors are involved (again, assuming that we are talking about dragsters):
1)at the starting line...maybe not much differece except to say this...lets say the rules allow a 36 square inch opening, would it be better to have a 6" by 6" opening on a hood scoop or a 2" by 18" opening at the cowl. I would think that the 6"x6" hood scoop opening would allow the air flow to stay attached and smooth. BTW, a big function of this is also the cubic inches of the airboz itself.
2) down the track...now we are talking about the difference between ram air in the scoop versus a high pressure area at the cowl...I still believe that raw air wins.
