How exactly is a "measured mile" measured?

[typo41]

Stan, you are correct about the curve and a straight line shot being different,,,

But at El Mirage, the Rod Riders layout the course, with the assistance of the Board. And the measured mile plus is done by calibrated machines inside three vehicles to make sure of the distance. The machines are checked against a know distance of 1000 feet.

So as the vehicles move down the lake bed they are traveling with the curve of the earth and are traveling on the surface there by getting the correct 'measured mile +" for El Mirage.

As they have done for over 20 years.

[tortoise]

Obviously going straight is the optimum method.

The question was about Bonneville and "other" LSR sites. For the pavement flying miles, some entrants might benefit from lengthening the runup by zigzagging a bit.

[dw230]

Wouldn't the zigzag be counter productive by introducing friction(loss of speed) in the attempt to increase top end? In road racing they tell us to straighten the turn, use as little steering input possible.

DW

[jacksoni]

Ya know, it may be a mile on the surface between the markers, but with the earth's curvature, it's a little less in a real straight line (but hard to take that course).

If my math is correct the difference is .065" more or less if the surface follows the curve of the earth rather than being flat. Not a whole bunch. (that's for a mile, longer course the difference is more)

[Stan Back]

Thanx!

I thought it would be a little more than that -- but not significant.

Years ago at a Pomona meet, Frank Cannon was running the Torquemaster(?) automatic(?) AA/F dragster and, to me, apparently weaving around down the strip.  The car wouldn't ET, but it put up some significant MPH.  It supposedly ran the first two 200 MPH runs on the same day.

Who knows?
(The Shadow do.)

[tortoise]

Wouldn't the zigzag be counter productive by introducing friction(loss of speed) in the attempt to increase top end? In road racing they tell us to straighten the turn, use as little steering input possible.

DW

Going straight is a good method.   However, a vehicle with a very low power/weight ratio but good aero might benefit from accelerating for a longer time before the trap.

[RansomT]

I use to run a Parabola path until I took out 7 cones.  About the time I was closest to the left side of the track my spray went to 100% lifting the front end slightly.  Big crosswind gust came along and pushed me into the cones.  From now on, it's a straight path for me.

[jacksoni]

Wouldn't the zigzag be counter productive by introducing friction(loss of speed) in the attempt to increase top end? In road racing they tell us to straighten the turn, use as little steering input possible.

DW

Going straight is a good method.   However, a vehicle with a very low power/weight ratio but good aero might benefit from accelerating for a longer time before the trap.

some zig zag has been discussed earlier, at least in theory. Pretty much all you get is a few feet unless really going back and forth a lot that that clearly would not be conducive to speed. YMMV so to speak pun intended

[Avanti Kid]

I would think that by doing a zig zag while going down the race course could make the opportunity more likely that you will spin out, thus ending you run. 

[GH]

I did enough zig zaging in 2009 between the 4 and 5 mile, I didn't like that at all.

[fastman614]

In my early days on big industrial construction, we laid out mile long tracts at times, using what is called a surveyors chain. which, for as long as I have been involved, is not a real chain at all. It is a 100 foot long piece of precision steel tape that is stretched to a certain tension using a precision tensioning weight scale that has a clamp attachment for holding the tape. The ambient temperature was also factored in based on the expansion co-efficient of the steel alloy of the chain. It was actually quite accurate but a rather time consuming process as the course was measured literally 100 feet at a time. Maybe that is why there was such resistance on the part of the executives of SCTA/BNI to multiple courses as recently as the very early 1990s.

In the 70s, I believe that Elmo Gillette, who was a representative of Kueffel & Esser (makers of high quality surveyor equipment), used to do this ..... Later on, I know he had optical devices that were quite accurate in double checking (I guess, it was nice to be able to borrow this stuff on an as needed basis)

Now, I cannot state with certainty that the courses of 100 or so years ago were measured as I described but the process for doing so had been developed back then....

[Stan Back]

Here's an excerpt from Bret Kepner's 4-page article in the 2014 SpeedWeek Program about the first "timed" event at Bonneville . . .


"Many of the drivers limbered up their mounts by racing the trains, much to the astonishment of passengers.  Initially, electric timers were to be used to conform to new AAA guidelines.  Unfortunately, voltage fluctuations in the telegraph lines made the clocks useless.  It was discovered heat waves and the blinding glare from the salt made the waving of the officials’ flags at the start and finish of the flying mile attempts impossible to see.  This led to a decision which would dramatically affect the event’s place in history.  Rishel and Moross decided to use stopwatches to time the runs over a half-mile course."

Don't remember how it was measured, but with the stopwatches, who cares.

[wobblywalrus]

We used to take that steel tape out and "chain" distances.  A mile would take twenty six chains with a 200 foot plus a little one at the end.  It was hard work.  Fortunately the highway department allowed us to have a beer or two during lunch.  (This was in the good old days.)  Almost always, we would foul up the calculations after lunch and spend an hour or two mixing them up even more while we tried to straighten them out.  Now we used electronic distance meters and a couple of educated chimps can do twice as much with more accuracy than a crew of four did thirty years ago. 

[Buickguy3]

   Which brings us to today. GPS? What is the opinion on this?
   Doug 

[wobblywalrus]

It is more accurate than us after our lunchtime beers.