Mathy question

[billtebbutt]

Hi folks,

Trying to understand the finer points of an incident (without the benefit of video) this past weekend. I need math to do it, and I can't do the math.....

If a FF was travelling at say 80 mph, was then launched into the air, travelling at about 2.5 feet above the track and parallel to the track's surface (at least initially), roughly how far would it travel before touchdown? I do have one still photo that gives me the preceding info. There is a LOT that goes into coming up at a rough answer here, I know....

I am trying to figure out what caused the extensive damage to the back of the car, as I then ended up very quickly decelerated from my landing speed into a tire wall front end first. My best guess so far (the car is not yet back in the shop to look at it) is that I almost cleared the track but landed gearbox first on the outfield curb, which basically sheared off the box.

Bonus points for an educated guess at the g-force deceleration over the 2 feet of travel through the tire wall/rubber apron/fence. Thank goodness for the Hans device.

cheers,
BT

[TimH]

Thank goodness for the Hans device.

Oh, yeah.

Without contributing to the physics numbers, or seeing the actual damage, I would still mention that the momentum of the motor will sometimes shear things when the rest of the chassis comes to a sudden stop.

[David Ferguson]

An object in normal gravity (32 ft/sec^2) will take 0.39 seconds to fall 2.5 ft, if the object was moving at 80 mph (117 ft/sec), it would travel a little over 45 ft in that time.

[billtebbutt]

An object in normal gravity (32 ft/sec^2) will take 0.39 seconds to fall 2.5 ft, if the object was moving at 80 mph (117 ft/sec), it would travel a little over 45 ft in that time.

Thanks David, that squares that circle. I will bet when I get the car back here, we will see the impact of the outfield curb on the gearbox case.

cheers,
BT

[Wee Bobby]

An object in normal gravity (32 ft/sec^2) will take 0.39 seconds to fall 2.5 ft, if the object was moving at 80 mph (117 ft/sec), it would travel a little over 45 ft in that time.

Just a dumb question...
If it takes 0.39 seconds to fall from 2.5 ft., wouldn't it take another 0.39 seconds to rise up from track level to 2.5ft.?

[R. Pare]

That would be dependent on how he was launched - it could easily be faster or slower.

[david oleary]

That would be dependent on how he was launched - it could easily be faster or slower.

The last time I got a FF AIR BOUND when I fixed it I did not realize until the next day that when I landed the flywheel hit the bell housing and snap the crankshaft, it started up ok but blew up in 3 laps of hardship practice, it was a brand new motor, after disassembling the crank was snap at the very last journal and you could see the teeth marks in the bell housing.
You should check inside the motor before starting.

[jtaphorn]

The last time I got a FF AIR BOUND when I fixed it I did not realize until the next day that when I landed the flywheel hit the bell housing and snap the crankshaft, it started up ok but blew up in 3 laps of hardship practice, it was a brand new motor, after disassembling the crank was snap at the very last journal and you could see the teeth marks in the bell housing.
You should check inside the motor before starting.

David, Unfortunately, I had an identical experience with my FC after being airborne. After rebuilding the car and not the engine, it lasted 3/4s through the 1st race when the crank broke with a portion exiting through the block with the rod. Sad day.

[EYERACE]

I forget the math I used when encountering a raw guard rail at Sebring years ago - went from about 55? to zero in about 18 inches - over the years I keep rounding down on the number but maybe I pulled 17 to 18 Gs ?? Yes, I like my HANS

[BorkRacing]

Hi folks,

Trying to understand the finer points of an incident (without the benefit of video) this past weekend. I need math to do it, and I can't do the math.....

If a FF was travelling at say 80 mph, was then launched into the air, travelling at about 2.5 feet above the track and parallel to the track's surface (at least initially), roughly how far would it travel before touchdown? I do have one still photo that gives me the preceding info. There is a LOT that goes into coming up at a rough answer here, I know....

I am trying to figure out what caused the extensive damage to the back of the car, as I then ended up very quickly decelerated from my landing speed into a tire wall front end first. My best guess so far (the car is not yet back in the shop to look at it) is that I almost cleared the track but landed gearbox first on the outfield curb, which basically sheared off the box.

Bonus points for an educated guess at the g-force deceleration over the 2 feet of travel through the tire wall/rubber apron/fence. Thank goodness for the Hans device.

cheers,
BT

I did the calculation with an 1100lb car going 100mph. 29G's