In regards to your application, the theory is that the SlopeAlert unit would trip a switch output when a predetermined angle is established, whereby the front of the vehicle rises up as it jets down the racetrack – the switch idea is to shut of the fuel (perhaps), which would cease forward momentum, thus lowering the front end before it reaches the “point of no return” as you aptly put it.
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Gosnell notes that the G-forces experienced during a run will affect the inclinometer. However, he feels with testing these forces could be compensated for to still detect a specific angle. The best way to test this would be to find a team willing to mount one of these on their car, then wire it to an open channel on the data recorder to tell when it fires.
WHEELIE CONTROL
Another device that has potential is Toby Graham’s Wheelie Control unit. One of Graham’s claims to fame is being drag racing’s traction control guru. His wheelie control unit was designed for outlaw street tire classes where wheelie bars aren’t allowed. The device senses vertical G’s and fires an output that typically retards timing to keep the front end down.
When initially considering this product, despite my spare time studies of physics, my concern was whether this device could distinguish between the vertical G’s of a normal launch and the vertical G’s when a car is down track. A dragster hiking the front end up to some degree at launch is normal and necessary. After putting the physics book aside after realizing I was looking at it upside down, I think this could be avoided by simply delaying the device off the wide open throttle switch. This may, in fact, make the device better. If making it get off the starting line without ‘tripping,’ then the sensitivity could be quite a bit lower.
Being the amateur physicist I was concerned with the directions force would be applied in such a wheelstand situation. Looking at the Harker incident, the car would already be in a wheelstand when the device would need to fire. I asked Graham how much angle affected the box, and the fact the motion was not truly vertical, but following the motion of a circle (the rear tire the center point). This was his response:
The vertical G doesn’t change that much during a car’s acceleration off the line. Imagine a car hooked to a beam that is perfectly horizontal. You could accel this car at 100 G’s horizontally/inline and the vertical G would still be 0g. Of course the rear of a car squats when it leaves the line initially, so in the real world you do see a bit of change in vertical G, very negligible though. However, when a G-meter is mounted in a car to measure vertical accel and the car starts to rotate…vertical G decreases. The Vertical G-meter starts to not only measure vertical G but also horizontal. If a car is accelerating down the track, the vertical G not only decreases because the car is rotating, but also because it is ‘seeing’ horizontal accel too. I won’t get deep into the math, but when you know a vertical G, do a bit of trig and you also know the angle of the car.
Currently the Wheelie Control looks at the vertical G 100 times a second. When the vertical G is lower than the user set threshold, it starts counting the amount of times the threshold is greater than the measured vertical G. If this condition exists 10 times continuously, i.e. a tenth of a second, it turns on a 12v signal. I set up the counter function to eliminate the system from false triggering. It isn’t a perfect device because like I mentioned earlier the car is accelerating forward at the same time. However, the inline accel curve is pretty consistent from run to run. Knowing this, the vertical number might be skewed a bit yet it still is a good bench mark to use.
LET’S DO SOME TESTING
Once again, the remainder of this season would be a prime opportunity to test such a device on a dragster. Ultimately, in testing the only real way to detect the full extent would be to have one of these devices on board during a major wheelstand or blowover. I think it could be conceivable once some preliminary data was collected to have a closed test session with a couple of very experienced drivers and tuners. Marty Thacker is a driver that comes to mind that has mastered a controlled wheelstand. (I know Marty is honored I volunteered him. Sorry, didn’t have time to call before writing.) If a controlled wheelstand could be reenacted, the device could be calibrated and ultimately tested.
A few other suggestions exist. I consulted Bob Ottow aka “Automan” for his engineering knowledge. His thoughts lean towards engineering a wheelie bar with its own master cylinder to apply the brakes and control a wheelstand. We’ll look into that more next month. Also, while talking to my dad, Rick, who works in civil construction, laser surveying technology presents some interesting ideas. An optical device could be developed. A laser benchmark could be set, say past the sand trap. If the front end got higher than a preset height, it would fire the shutoff. Proximity switches are a possibility we’ll look into as well.
I apologize for the excessive length, but I feel it is ground that needs to be covered. If you have an idea, please feel free to email it to us here, or comment on my website at InsideTopAlcohol.com. There may be a method I’m overlooking one of you have. Necessity is the mother of invention, and I hope we can ‘invent’ something to prevent these blowovers.
Now that you’re On the Tire, go forth and spread the good word!
will.hanna@insidetopalcohol.com
