Eddy current dynos are very nice animals. The reason is that the torque they absorb is directly proportional to the current through the coil. So they are much easier to control than the water dyno. The disadvantage to both eddy current dynos and water brakes is that they create huge quantities of heat. Because all the hp absorbed by the dyno is turned into heat. To solve this problem, dyno manufacturers started using brush DC motors, they later converted to three phase induction motors.

The advantage to using motors is that the power absorbed by the dyno is converted into electricity and fed back into the power grid instead of going up as heat. The other advantage to using a motor is that you can also power the vehicle or engine to simulate a vehicle going down a hill (for instance). In that case, the engine acts as a brake and the vehicle or dyno actually drives the engine.

The disadvantage to using electric motors, is that they are much more expensive that eddy or water brakes. So for cost sensitive applications or very large engines, these dynos are still used.

 

Very interesting reading..............<yawns>


Not to many drag race fans on here though. Nice math calculations but you are assuming that the dragster will have a .00 reaction time. Thats not possible without cheating. Human reaction time is around .2 of a second. The car will also have a reaction time. Due to this fact, and based on all of the math that you guys have worked on, I believe that the stock car will win this race.


Nuts did mention reaction time a few pages back but no one really picked up on it.


This hypothetical senario reminds me of the "Shockwave" truck racing the airplane. Has anyone ever seen that. Its really cool.

 

I first heard about this question from a radio station in Atlanta, They had a prize give away for the correct answer to the equation they supplied, and yes the drag car does beat the NASCAR "sorry ACE I know it's a stock car". They had reaction times figured in etc, etc. The radio station also had NASA supply the answer they used. I am not sure which station carried the contest as I can not get the radio station where I live. My youngest goes to school in Atlanta and is the one who told me about it. When he gets back to school in a couple weeks he is going to contact the radio station and see if he can get us the answers. He is positive that they used Tony Schumacher's speed and time. Which is what I posted for the question. The NHRA top fuel speed record is 336.15 mph and a ET record of 4.437 seconds.

They had thousands of responses to this question being they are deep in NASCAR Country, But the truth is the Top Fueler does catch and overtake the NASCAR.

I only asked this question for fun, there are some people "me included" that like to do a little math to sooth the brain. I let this thread go for awhile just to see the responses. There is alot of quibble going on about this and that, but what every one overlooked and it was even posted as an unknown hint. No one figured the amount of G-forces that the top fueler produces. Which can be called, "as close to getting time to stand still on earth". < not in the skies or you can't use any of the fastest land speeds in the world as they use gradual acceleration.

 

was we supposed to use E=MC²

 

Im thinkin Bryce and KNutz was sending this feller Email Down at the bottom this guy has some interestuing calcs

 

Another question has to be answered here. Is there a normal tree? If yes, then the dragster driver will anticipate the green light from the last yellow light and so the reaction time will be much less that 0.2 seconds. It will be more like thousandths of a second because these guys are so good. Seems to me that the christmas light can still work as normal because the stock car is going at a fixed speed.
Bryce

 

Furthermore, given that the drag racer has timed his start just right (according to the christmas tree), he will be moving prior to the stock car even hitting the start line. Here is a good reading on reaction times and starts. Staging

 

The problem I see with his calculation is that he assumes a constant acceleration in the first 1/8th mile. We make no such assumption in this thread. We assume constant acceleration in the last 1/8th mile. He needs the 1/8th mile speed (like we have) to come up with a more reasonable calculation.

 

Bryce:

There is no "normal" tree. It's either a sportsman tree or a pro tree. You probably know this. You obviously read a lot. In any case, this is not a real race. Its just a science experiment. A real race would be a drag car being given a green just as the stock car passed the beams. (that's why I jokingly said that the stock car would win)

You are correct in saying that you can anticipate the green if given a tree. On a sportsman tree there is .5 of a second between each amber and then the green. A good human reaction time is just under .2 of a second and most cars (both street or decently modified) have about a .3 of a second response time after you lift off the brake and hit the throttle. If you hit the gas when you see the last amber light you will have around a .500 reaction time....thus leaving the line the instant that the green comes on. Rookie drag racers beware, if you anticipate the last amber you will redlight with about a .300 light.


Oh and if the dragster moved past the staging beams before the other car hit the beams then the dragster would have redlighted.

I still say that the stock car wins. (and I'm a drag race fan) [img]i/expressions/face-icon-small-smile.gif[/img]


Bryce,

Do you have a GTX? Now that's a drag car!

 

I disagree Madwolverine. Seems to me if the drag race groupies insist that the end speed is calculated according to NHRA rules or whatever governing body they decide is appropriate). Then it seems fair to insist that the rest of the race is governed by the same rules. Seems to me that includes a tree that allows driver anticipation. So it seems to me that driver or car's reaction time is a non issue and has no place in this calculation. Come on guys.. make up your mind are you going to play by your own rules or not??

Now given that the dragster is governed by NHRA rules, the car can actually start moving prior to the green light as long as he does not trip the "starting line beams". In this article that is called rollout. Are you saying you are a racing fan and don't understand this effect?

We are not talking about passing the staging lights early, I am talking about moving between the prestage beams and the stage beams. The car can actually be moving prior to the green light. That is what the article I cited above is all about.

I have read about the two types of trees. My reference to a "normal tree" was to point out that there should be any tree there as opposed to no tree. As is "normal" with an NHRA (or other sanctioned) race.

If you don't insist on some conformance to a sactioned type race, then it seems to me you can say nothing about what the ET of 4.437 seconds even means!!!