List:
Most of you don't know me very well. Just this once I'd like to tell you "where
I'm coming from", hoping that you'll give some credibility to these ideas on a
subject that I think is critical to the safety of our racers. I am a mechanical
engineer-- semi-retired now-- and I spent about half my career in automotive
research (Southwest Research Institute, San Antonio). Among my other
assignments, I conducted guardrail car crash tests, and I tested automobile
tires
on a tire dyno. (Most of the rest of my career was spent in test and
measurement
in the petrochemical industry.) I'm a former AMA motocross racer who has had
some minor involvement in circle track racing and NHRA Federal Mogul Funny Cars.
I am a volunteer worker in the CART racing series. I am currently dusting-off
my
driving/riding skills, and I hope to build my own LSR machine. This year I
crewed for Skip Higginbotham and Bill Smith on the "Yellow Rose of Texas"
record-setting AA Lakester.
Now for the subject:
During the summer we had one thread going about the difficulty of getting
reliable high speed tires, and another about whether or not SCTA should make
traction control (TC) legal. I've been thinking a lot about both issues since
then, and I'd like to re-open the discussions. I hope some of you will jump
back
in.
In my two trips to Bonneville this summer, I heard-- and personally observed--
that many of the most powerful cars were plagued with drive-tire blisters,
throwing tread, circumferential growth (plastic strain) and even blowouts. (At
the end of this letter, you'll find Joe Timney's previous letter to the list
that
cites the scariest example of this problem.) The problem was not just with Earl
Wooden's car-- it actually seems to be very widespread among the cars over
300mph.
There was an earlier suggestion on the list that we try to get the tire
providers
to produce a better product for us. Having watched dozens of salt
"roostertails"
(lasting almost 5 miles, in some cases), I don't believe that there is very much
that the tire manufacturers can do for our high speed tire failures. As Joe
Timney suggests below, technology probably doesn't presently exist to produce
tires that will maintain a safety margin for a 5-mile burnout (finishing over
300mph). The most powerful machines are capable of literally abrading the best
pair of tires to death in much less than 5 miles!
The other way to address the problem is to limit the amount of drive-tire spin.
Our racers have used several techniques to try to accomplish this. Other than
suspension/ chassis setup, reducing aerodynamic drag, or having the driver use
less than full throttle-- most everything we do (reducing tire pressure, adding
ballast, aero downforce, etc.) stresses the tires just that much more. I don't
believe that we can hope to reduce tire failures by reducing tire pressure,
adding ballast, or increasing downforce beyond the values that our fastest cars
are currently using.
Most racers have already done everything within their power to reduce
aerodynamic
drag-- so I think most would not find that a productive area to work on (unless
you want to invest in some expensive wind-tunnel time). Many of our cars could
probably benefit from better suspension / chassis setup (see Bill Hoddinott's
interview with Chuck Salmen-- published on this list in 1999). However, we can
probably only gain a little with these improvements; many machines would likely
still retain the ability to shred their tires in one pass.
The obvious answer is in the throttle-- as we keep hearing at the starting line,
"it works both ways". One difficulty in that concept is that some machines seem
not to give the driver sufficient feedback so that we know how much spin we're
getting. And most of us probably can't judge how much spin is too much--
especially if the car is tracking straight and not otherwise acting too scary.
And many LSR drivers are dominated by the thrill of speed, and only want to hold
the pedal on the floor, even if the car is "wagging its tail"! I think that
there is only one way to allow the drivers to go "all-out", and still minimize
the risk of tire failure. I think that the only way to accomplish this reliably
is to compute the optimum power delivery values, "on the fly", real-time-- and
to
automatically make the needed adjustments to the power delivery.
I'm talking about Traction Control.
I'm asking you to consider TC as a safety issue-- in terms of the potential for
preventing the injury or death of some of our fastest drivers, due to high speed
tire failures. Yeah, Earl Wooden came out of that bad wreck pretty good. The
safety rulemakers deserve their pat on the back-- as do the inspection folks--
as
does the builder-- as does Earl, for keeping himself in such good shape. But
let's not forget that Earl was damned lucky, too! Look at the Speedvision film
a
few times ...see the chaos of a 300mph crash? We can't build anything that will
assure that the driver will survive these. We can't predict all the things that
can happen, all the places that the kinetic energy will be expended. As much as
possible, WE HAVE TO PREVENT THESE HIGH SPEED CRASHES. I think that TC is the
most powerful crash prevention tool at our disposal for reducing the potential
for high-speed tire failures in Land Speed Racing.
I have been discussing this proposal "off-list" with Bill Hoddinott
("Ardunbill"). Bill points-out that many LSR people are afraid that legalizing
TC will guarantee that many of the top landspeed records will go to the
big-money
people. I am not convinced of that. A big percentage of the (not rich) hot
rodders already on the salt have already mastered harder (and more expensive)
technical problems. I know several people who could design, build, and program
a
system in a couple of months, from scratch. I estimate the cost to be from $5k
to $15k.
Better yet, if we could get SpeedPro, MSI or Edelbrock to make an inexpensive
mod
to computerized systems that many competitors already have aboard, we would only
need to spend from $100 - $300 for sensors and a servo... plug it up.. and go
nail the throttle! In fact, I would not be surprised if one or two competitors
have already accomplished this. The claim that only the rich guys cars (or
factory sponsored cars) could compete for records in TC-legal classes has no
basis in fact. It is, as they say ... "bogus".
Bill also pointed-out that many competitors feel that this computer-based
technology has no place in the vintage classes. On that point I agree-- vintage
class needs vintage technology, if we are to maintain the value of those
classes. I have no solution to propose for the roadsters, etc. (and the fastest
ones have the same tire problem). But surely we can allow this safety feature
for those very fast "special construction" vehicles, modified sports, bike
streamliners, etc.--?? If TC can keep even one of our drivers from a 300mph
crash, I think it is worth the effort.
I invite comments from any and all. My hope is to build a little "grass roots"
momentum toward proposing legalization.
Best Regards,
Russ Mack
Joe Timney wrote:
> List,
> John Beckett and I got to look over Earl's car with Jim Miller and a
> couple of things stood out. The drive train is off-set to the right and
> he blistered a right rear tire the day before. The car had a lot on lead
> mounted in front of the rear. He was running Goodyear Landspeed
> tires...brand new!!! There were chunks off the center. Earl was
> traveling at 288 out of the four mile...obviously that tire was loaded
> and probably spinning...I'd like to see a data acquisition readout on
> that run. One can not expect to see any tire take that kind of abuse. I
> have seen drag slicks spin in the lights and get a slight
> blister...guess what...they either fail soon after that or they change
> circumference, then fail!
>
> I wonder out loud if Keith's tire circumference issue was also a
> heat/spin/load relationship???
>
> I'd also like to publicly thank Jim Miller for the opportunity to "learn
> for the remains". Looking at how the structure held up and bent, taught
> me a couple of "must do's" when designing future projects.
>
> joe
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