Recent discussions about staging
effects on E.T. and RT, and the effect of wheel "rollout"
on same prompted me to invest a little time in some hardcore
analysis of this deal in an effort to put some numbers on it.
Of course any exercise like this is only as good as the "presumptions"
behind it, so I have to qualify it in that regard. I do believe
the presumptions are fairly realistic, however.
We all appreciate, I think, that
there's "real world" complications that introduce assorted
inaccuracies in the measurements used to record and report performances.
We discussed some of these here before, such as the error in
reported terminal speed based on a clock reading of time to travel
the last 66 feet, and the likelihood that the front spoiler rather
than the front wheel is tripping the finish line e.t.clock, due
to it's deflection under load and the height of the photocells.
We've also talked about less common situations, such as "bouncing"
or jumping over the finish line lights and tripping them further
back on the car. I disregarded any such "finish line"
complications in the analysis I performed.
The starting line presents its
own set of compromises. The "staging light" trigger
beam projects directly across the starting line, and is part
of two separate circuits. As a wheel enters and blocks the beam,
interruption of the circuit causes the "staged" light
to illuminate on the tree. Later, as this wheel rolls across
the starting line on a run, it allows the staging beam to once
again illuminate the target photocell across the lane. This shuts
off the staging light and starts the e.t. clock. Time is also
measured from the moment the last (or only) amber countdown light
is illuminated till the e.t. clock starts, and this is reported
as "reaction time." All pretty fundamental.
This arrangement does mean there's
a certain amount of "play" in the system, however,
as the wheel can block the light beam with any point between
its leading and trailing edge. We call this "rollout."
In essence, it means that supposed standing-start e.t. measurements
are in reality rolling start e.t. measurements....not much (a
foot or less) but rolling nonetheless, as the wheel is moving
forward as it exposes the beam starting the clock. Racers have
found that the greater the rollout before the e.t. clock starts,
the better their e.t. slip reads, as the time spent moving that
first foot doesn't show up. Offset front axle arrangements, with
the wheelbase shorter on one side of the car than the other,
is one approach toward maximizing rollout, and so common that
NHRA limits how much is allowed. The impact of "rollout"
on reported e.t. and RT is what "staging strategies"
are all about.
The analysis I conducted quantifies
the extremes that deep and shallow staging might provide with
our "real world" starting line timing system, and does
so in terms of numbers the IDENTICAL RUN would yield depending
on exactly where the car was situated within the "staged"
footprint.
I've assumed the following situation,
where this little illustration represents our dragstrip:
A-B-C------------------------------------------------D-E Point
"B" is the starting line and Point "E" is
the finish line. Point "A" is where the front of the
forward-most front wheel first flickers the staging lights upon
entry (I'm using forward-most and rearward-most terminology here
on the presumption of a staggered-axle car). Point "C"
is where the rear of the rearward-most front wheel leaves the
staging light after launch, simultaneously starting the e.t.
clock. Point "D" is where the front of the forward-most
front wheel trips the finish line photocell, stopping the e.t.
clock. Point "B" to point "E" is 1320 feet,
but because the e.t. clocks start off the back of the wheel and
stop off the front of it, we are really measuring e.t. over a
shorter distance, and that distance is identical to the point
"A" to point "C" measurement. I took this
to be one foot (12") in my analysis. This will vary car
to car depending on wheel offset, tire diameter, etc., but I
think it reasonable if not conservative.
For the nominal run of comparison,
I assumed the car was staged directly of the starting line, exactly
midway between it's deepest and shallowest possible staging.
I assumed it launched at a 5G rate, ran a reported 4.60 e.t at
320mph with a reported driver RT of .525. Again, figures I think
represent a reasonable yardstick.
These figures are sufficient
to define the "run" that I then carefully refigured
assuming a starting position six inches either way, or in other
words, as shallow-staged and as deep staged as possible in accordance
with the the above assumptions about point A, B and C. This meant
accounting for the change in distance the car actually runs in
each scenario (1318.5, 1319 or 1319.5 feet) and the amount of
acceleration time that doesn't appear on the e.t. clock since
it occurs while the wheels are still blocking the starting line
photocell. The latter is the far more significant. On a 5G launch,
it takes 0.079 seconds from when the car first perceptibly moves
to cover 6 inches, and 0.111 seconds to move 12 inches. In other
words, the on the "nominal" 4.60 run, the car was actually
under power 4.679 seconds before it tripped the finish line clocks,
but the first 0.079 seconds didn't show up as e.t. because the
clock hadn't started yet. On the "deep stage" run,
0.111 seconds is an uncounted freebie. However, at the other
end of the track, moving at 320 mph, six inches is covered in
only 0.001 and a foot in 0.002 seconds, so "adjustments"
for a shorter or longer actual run are minimal.
With "reaction time"
being everything that transpires from the millisecond that amber
comes on till the front wheel starts the e.t. clock, time actually
spent accelerating out of the staging beam is included. The "nominal"
0.525 RT of the baseline includes the 0.079 seconds of acceleration
from point B till the front wheel clears point C. While the biggest
component of RT is always the driver, it is and always has been
a "driver + car + timing system" composite.
In case there's still any unclarity
about the above, the numbers I crunched are exactly the same
as if there were three sets of starting line lights for the same
run, each six inches apart, and each reporting their own set
of e.t. and RT numbers, and with the outboard extremes representing
the deepest and shallowest stagings.
The results: 6" Spread Point
A to B and B to C
Indicated
e.t Indicated RT "Package"
(RT + e.t.)
Mid-staged: 4.60
0.525
5.125
Shallow staged: 4.567
0.557
5.124
Deep staged: 4.677
0.446
5.123
This doesn't change the "conventional
wisdom" one bit (i.e. shallow stage for best e.t. and deep
stage for better RT numbers). Assuming no foul, it is always
the "best package" that trips the win light, regardless
of reported e.t, and note that the "package" times
vary only by a couple thousandths.
Another way of looking at the
results is to note that there's a direct rob Peter to pay Paul
connection between e.t. and RT, in that enhancing one hurts the
other an equal amount. The only "real" advantage to
deep staging (other than psychological distraction of the opponent)is
the potential for a couple thousandths at the top end due to
a 6 or 12 inch "shorter" run....and the penalty for
this in the e.t. that counts for for lane choice is pretty severe!
Although I just ran these for
my own amusement, thought you might be interested in what kind
of numbers are involved. Hard to believe that a 4.57 and 4.67
are "identical" results depending on where the front
wheel is parked on the starting line!
Vic's hardcore analysis was
prompted in part by the following commentaries done by two of
the most respected men in the sport. The core of the discussion
was the question, "Why did dragsters in the 60s and 70s
run "wheel discs" on the wire front wheels. It went
from there to deep staging, small front tires and other "tricks"
tried over the years.
Wheel Discs
"The purpose of the wheel
disc was to prevent the photocells from shining through the wheel
spokes before the complete wheel had rolled through the lights.
Thus giving the car more roll out before the clocks started.
This did two things...It helped
to decrease your e.t., and it also help to reduce the possibility
of a red light. Many tracks in the early days of drag racing
had excessive crowns built into them for drainage purposes. The
track operators would have to raise the photo cells to clear
the crown in the lane. If you staged near the centerline or near
the edge of the track, there was a very good chance or red lighting
without the aid of the disc.
Now, back to your question...
Front wheel stagger is to give the car additional rollout before
the beams detect that the car has moved. Because torque has a
tendency to lift the left wheel first, it is normally the leading
wheel. You want the wheel disc on the wheel that is going to
stay in the lights the longest." Gary "Mr.
C" Cochran
Small Front Wheels
"The "monkey see, monkey
do" syndrome was never more in evidence than it was with
the small dragster front wheel episode. This ties in to the discussion
regarding wheel discs, reaction times, etc.
The Garlits' influence, as usual,
was overwhelming, as his idea was jumped on by almost everyone
after he scored a couple of wins. The irony of the whole deal,
was that the only reason he first used the small wheels was to
have something that would fit underneath his "spoon nose"
design...which soon proved to be a failure. He tried some home
built rims with "rubber bands" as tires, but they failed...so
he then used the small airplane tires/wheels. It was touted as
a revolutionary advance at the time, but it was simply a by-product.
After abandoning the "spoon nose" experiment, we were
left with those silly looking things on the front end, and almost
everyone else had joined in. I recall Frank Bradley being one
of the few who rejected the idea. Personally, I hated the things
from day one.
The small wheels had quite a
bit less "roll-out", so reaction times got better...but
e.t.'s went the other way. Dick LaHaie was one of the first to
start questioning this factor, and soon proved that it was worth
a "swing" of approximately .04 seconds. That's a bunch,
when it comes to qualifying, lane choice, etc., so he promptly
changed back to the larger diameter wheels. It took a while for
the others to "get it", as many of the drivers simply
couldn't bear the thought of giving up their artificially enhanced
reaction times. Kenny Bernstein actually wanted to qualify with
the big wheels, and run eliminations with the small wheels...just
so his reaction times would look better in competition. Armstrong
finally shot that idea down. Eventually, the small wheels went
away.
It was really goofy to see some
of these racers using a car with staggered front end, with the
little wheels, and then deep staging. Talk about opposing forces....
Steve Gibbs |