CAR'S ACELERATION VALUES 1

[pardal]

Hi all , could you tell me what are the most common acelerations values on a car .
I'm interested on the aceleration when draging , from a street car to a 1/4 mile drag cars.


Pardal

 

[Metalguy]

If a car were to accelerate at a constant 1g for 1/4 mile, it would take something like 9 sec., and it would be traveling ~150 MPH at the end. For a while many years ago it was thought those numbers would never be bettered, because to accelerate at 1g the coef. of friction between the tires and the strip would have to be 1.0, and the common physics books said that was the "upper theoretical limit".

But hot-rodders didn't always know the physical laws, and now funnies and top fuelers run well over 300 mph and ~4.5 sec. So *you* figure out the g force and COF!

 

[c2s]

A typical production sedan will spike about .5 g's off the line and decreases to around .2 g's by about 30 mph.
Kevin

 

[KingSumo]

What is the best part suited to measure this acceleration?
The ADXL202 of analog-devices (+2g/-2g range) can do the job?

 

[c2s]

Their low pass filter of 12.5 HZ will probably need some add'l filtering to get it down to a usable, readable range. Typically, you want vehicle handling filters below 5 HZ.
Kevin

 

[GregLocock]

ARe you trying to measure the longitudinal acceleration of the car? Measure its velocity (eg use the ABS tonewheels) and differentiate, if you want accuracy. Suitable strain gauge type accelerometers are made, but they are tricky to set up and expensive.

The problem is that the vehicle pitches as it accelerates, so you measure the pitch angle as part of your acceleration.



Cheers

Greg Locock

 

[DanT]

If an accelerating 100 inch wheelbase vehicle's nose rises 4 inches and the tail drops 4 inches the difference between a horizontal vector and the vehicle CL (error?) is about 0.3%.

some folks claim good results and swear by the hot rod toy GForce gizmo.

 

[GregLocock]

Good example, check your maths



Cheers

Greg Locock

 

[willeng]

PARDAL:

As already stated rolling resistance, aerodynamic drag etc etc all play a part in this game & to give approx acceleration rates of different vehicles is best worked out yourself. This is a threotical evaluation & can be used for compairing different vehicles.
To find your acceleration rates:
Firstly work on losing 15% power due to drive train losses etc etc. This gives us 0.85% efficiency factor.
Now to find the acceleration rates we need Flywheel torque in lbs/ft,Drive wheel torque lbs/ft & Wheelthrust in lbs.

Drive wheel torque= Flwheel torque x gear ratio x diff ratio x 0.85

Wheel thrust= Drive wheel torque/ rolling radius of tyre in feet, measure in inches & convert to feet. multiply inches by 12 to get figure.

Acceleration force in g's= Wheel thrust/ weight

1 g= 32.174 feetper sec per sec
you can work out the feet per sec by multiplying 32.174 x the g,s worked out.

 

[xs650]

Willeng, You can cut through most of maths if you have rear wheel horsepower data available.

Thrust = power/velocity

Thrust = (rwhp/velocity)*375

Where:
rwhp = rear wheel horspower
Velocity is in miles/hr
375 = finagle factor to beat the English sytem of units into giving us an answer.

 

[willeng]

xs650
Can you give me some examples of acceleration forces in g's using your calculations.