Finish Line Beam Height

[Michael Pliska]

I think we have all probably lost a round (whether or not we knew it) to someone who took the stripe with body panels which were still in compliance with the 3" min clearance and 30" max overhang NHRA rules. Have you ever compared the height of the finish line beams to the starting line beams? The finish line is much higher, such that body panels frequently trip it. I asked the question of an NHRA guy about 20 years ago, and was told that the higher beams were to make sure the tire did not pass through within the timing system's sampling period (i.e., to make sure the timing system did not "miss" seeing the tire in the beam) when the car was running at a high speed. This was not a problem on the starting line, so they were lower there to make sure body panels did not interfere.

I'll bet that every national record in the pro classes was set by a car tripping the finish line with body panels, making it a 1317.5' pass instead of 1320'.

Why is the finish line beam still at this height? I would think that the modern timing systems are not in danger of missing a wheel, even at 350 mph. We end up with inaccurate ETs and the possibility of unintentionally giving up the stripe in bracket and .90 class racing.

I remember the first time I lost this way, giving up the stripe to a then-new Brogie roadster with its extended front "spoiler". I almost lost that way yesterday to a Suncoast roadster (gave up the stripe but ran dead on with a 0 while he broke out).

Thoughts/arguments/agreement?

[MikeSawyer]

Originally Posted by Michael Pliska

Why is the finish line beam still at this height? I would think that the modern timing systems are not in danger of missing a wheel, even at 350 mph.

Remember Steve Johnson in the final at Indy a few years back? It sure missed that one....

-Mike

[JimmyStack149K]

You should know your opponent and be aware of the ride height of the car you are racing. That way you know if you are racing the nose or the wheel.

[Michael Pliska]

Originally Posted by MikeSawyer

Remember Steve Johnson in the final at Indy a few years back? It sure missed that one....

-Mike

I thought there was an issue with his wheel not having enough area?

Originally Posted by JimmyStack149K

You should know your opponent and be aware of the ride height of the car you are racing. That way you know if you are racing the nose or the wheel.

But if it is close to the 3" min height you won't know which one to do. Wouldn't it be better to always know you are racing the wheel?

[racerhead]

Good topic.

I've measured my home track at 5". The body work on most tube cars will trip the beam with the nose. I saw a finish line photo of two comp cars (I believe Arnie martel was one of them) with one nose clearly in front but at full throttle it was high enough that didn't trip till the tire. The opponent's car was lower, a good foot behind, but because he tripped with the nose, got the win light. It's a quirk of the system.

Full suspension cars such as stock and superstock will trip with the wheel unless the driver drops hard, which collapses the suspension and trips the beam (often) with the front spoiler...this gets complicated because now the driver has tried to kill some et and actually picks some up. Makes for some funny numbers.

I believe it's actually pretty rare that it happens.

Bruce Deveau

[Chris Williams]

Virtually all dragsters made today have either a nose or wing, extending in front of the front wheels, with a vertical surface that is several inches high with the full intent of tripping the beams.

[Michael Pliska]

Here is a link to the aforementioned comp photo:
http://www.flickr.com/photos/9053883@N06/1356172176/

And some discussion about it:
http://forum.competitionplus.com/showthread.php?t=1491

This link has several other links, including the infamous Steve Johnson photo. In the case of missing his low profile tire, lower beams (as I am suggesting here) would have HELPED the situation, as they would have been below the height of the opening in Johnson's wheel, and guaranteed a longer duration blocking the beams.

Does anyone have a good reason why the beams should NOT be lower?

[MikeSawyer]

Originally Posted by Michael Pliska

Does anyone have a good reason why the beams should NOT be lower?

Bumpy tracks (picture taken between the cones):

.

If the beam hight had been the same as the starting line and the tire hops over it, then it doesn't see anything until the back wheels... The Pro Stock Bikes were wheelstanding through the finishline at Maple Grove because of the bumps there.

Also, take a look at the image below. A 3" nose, under braking, is not 3":



So now you'd be taking a whole bunch of cars that consistently take the beam with the nose of the car, and making it so they take it with the wheel, well, except under braking. Then you have the same problem of figuring out what the car is going to take it with again anyway...

-Mike

[Michael Pliska]

Okay, I hadn't thought about bouncy finish lines, but holy crap - they should fix that track!!!

If finish line wheelies are still a problem, they could run a guard beam that is higher but farther downtrack. The tire would stop the clocks 99.9% of the time, and they would still have a close timing result for the rare misses.

With the lower beams, you might have the occasional braking-induced nose trip, but it seems that it would be the rare exception. I would rather see true wheel-to-wheel racing the majority of the time.

[CBS jr]

Mike Sawyer.... nice dump job by looking at your front rotors. LOL Tell your dad hi.