Monster Trucks have a lot of science going on
No, really. I went to my first Monster Truck thingy (it wasn’t a huge show and there were only two trucks) over the weekend. I wish I had a) brought my camera and b) had my b5 press pass on me so I could have pictures and got to talk to the owners/drivers because any truck that goes around with tires that weigh 660 pounds each has got to have a lot of science going on.
Let’s look at the tricks they do first. You have the car crushing, flying through the air stuff. These folks have to be pretty careful about their launch angle or they are going to wind up upside down in a heap. Not to mention, and I saw this myself, any left or right tilting is a bad thing.
So what’s going on here? Basically, unlike a car, the weight isn’t terribly well balanced. You got huge freaking tires, suspensions that make a crane look like a wuss, and the fact that the top of the truck is really only a shell. A car, because it’s more compact, can handle a lot more fudge factor once it leaves the ground and still land on it’s tires. Oh yeah the tires … these monster truck tires (from farm equipment, actually) freakin’ bounce. So say front left hits the ground a bit before right front, well left front will bounce and throw off the whole bit and the truck is no longer falling just down but you have a lot of left-right-and all over the place going on.
Oh and I mentioned the suspension? Yeah, like six (or more) shock absorbers per wheel. Regular vehicles have one. Why six? Why the intense suspension anyway? Well it’s the whole up in the air thing. Okay that and wanting to bounce in the air and crush stuff. Because you have huge tires and what should be a top-heavy truck, you need lots of hydraulics to even out the bumps. Not enough cushion the top would smash down on the wheels or frame.
Originally monster trucks only had enough extra suspension to make it drivable, now they had extra, extra to do tricks.
While many of you might dismiss Monster Truck rallies, pay attention to what a driver has to be thinking about when he/she is doing these stunts. How high is the pile of cars? What’s my launch angle? Will I flip backwards? Am I going too fast so that if I bounce I might twist in the air (and die)? And consider the engineering that is needed to have something that high be able to be driven with 660 lb tires and 1100 horsepower engines (yes, 1100) running on racing fuel.
Science is everywhere, if you look for it.
May 14th, 2007 at 12:09 pm
Don’t forget the rotational energy, too. Four 660 pound (300 kg) tires, when spinning at a couple of
hundred RPM, will have quite a bit of stored rotational energy. Due to the law of conservation of (angular) momentum, if those tires stop (or start) spinning while the truck is in the air, well, something else has to start spinning, such as the truck itself. Couple this with the rotational momentum of the engine, transmission, and drive train, and this means that any change in the (angular) speed of the drive train while the vehicle is in the air can make the truck pitch and roll.
And, I bet y’all thought it was easy to jump cars in a monster truck. :-)
Dave
May 14th, 2007 at 12:26 pm
Dave … great point! I could really see that happening when those buggers hit the ground. I noticed they slowed down a bit before launching in space, probably to slow down the rotational energy a bit.