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At the Peru tour on Sunday there was a long, walled slalom.  It elicited a lot of discussion on site and now in various forum threads.  I want to try to get a focused discussion here.  Per Larry Hart's dimensions the slalom was like this:

X  X  X          X  X  X          X  X  X          X  X  X          X  X  X

<-40'->

         <------95'------>

You entered on the left (top here).  I believe the cones also had a beneficial offset, about 1/2 cone base worth.

My approach was to drive it like I paced it, a 31 pace (~93 feet) slalom, only paying attention to the last cone in each wall.  I thought it drove just like a slalom; dove in hot, broke before the 2nd wall, constant speed at the end of the 2nd wall and 3rd wall, and on the gas on the way out.  I was happy with the result.  I've heard others talk about unwinding the wheel between walls and gassing it a little. 

Do the cones, other than the last one in each wall matter?  I say no. 

The thing that sparked me to start this discussion is using Byron Short's slalom formula.  I've used it extensively in the past for course design and to get an idea of the speed of a slalom I'll be driving if there are offset cones.  It is usually within 3 mph, maybe 4 tops.  In this case, the predicted speed for my Z06 was 71.5 mph.  Actual speed on data logs (DL1) was 58-59 mph.  That's a huge error. 

So, does the slalom formula fail for really long slaloms (due to its assumptions?), is this really not a constant slalom, or did I just drive it 10+ mph too slow?

-Steve

I know it drove alot faster than it walked. I was shocked that I was able to carry so much speed through it. I noticed Arron Miller was on the 2nd gear rev limiter in his car going through it.

 The last cone in the first wall of cones was a target for alot of people's right rear tire. Seemed like everyone hit that cone atleast once. It looked like there where two ways of attacking it also. looked like about 25% of the drivers would drive right down the wall coming into the slalom, and 75% would take more of a sweeping radius approach to it. I'm not sure which way was faster.

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2005 Neon SRT-4 ACR White. #6 SM
Fresh of the dealer lot 2008 Solstice GXP #6 AS

I haven't studied Byron's formula in years, but I would think that with the walls the amplitude would be more significant than a classic slalom, thus accounting for some of the discrepancy.

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Al Chan

their was no offset at all , they were all lined up straight unless someone moved them after i layed them out,, for me i don't think this thing drives much like what a regular  slalom does  with the 55 ft gap it seems like it would be slow but then you got 40 feet to gather the car back up before the next 55ft gap,  this is a very interesting feature that i have not seen before and was a lot of fun, and something different that was not  painfull to drive ,, all the measurements were from center line to center line of each cone and were with an inch of each other

I didn't look at my DL1 from Sunday yet.  But since I didn't see anything over 65mph on Saturday, so I really didn't think that salom would be anywhere near 71 mph or so.

 Now that you put the 58-59 out there, I am now pretty curious what I hit and constant speed in that salom.  I didn't want to push the envelope there which was probably a mistake------take it at 95 % clean run----take it at 103 % = coned run.

 Your formula might be more applicable to a standard salom, as I believe the addtional two cones had a significant impact on the geometric line through the salom.

 

PS---yeah what Al said

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Trying to get faster

OT:  Did Lehman really write that, or was it his non-evil twin?

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Mark Valera
2001 Chevrolet Camaro Z/28 "1NE"
FS #93

acrace:

I haven't studied Byron's formula in years, but I would think that with the walls the amplitude would be more significant than a classic slalom, thus accounting for some of the discrepancy.

That was my thought as well, the amplitude of the curve could be different because of the first 2 cones of each wall shortening the exit.  Whether this is a perceived change that the driver thinks is needed or an actual change is hard to quantify but I would bet that the height of the curve is higher than a standard slalom.

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-- Drew
AS S2000

put a 95 ft slalom in the formula starting with a 4 ft offset and keep changeing the offset untill you come up with 59 mph , that should be perty close to what it drives like

MaxQ Data shows 58-59 on most runs for John and I, with a peak of 59.9 mph for John R.  Entry speed was similar to exit speed with a 2-3 MPH dip near the 3rd wall.

 We saw our biggest run to run variance in the second slalom, over doing the entry speed hurt all the way to the finish.
 

 

Chris H 

B-stock

RX8 

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Trent@TireRack.com
aka Chris Harvey

I was 59 mph as well an my MaxQ and also expected to be faster.  Andy Hollis clocked us ESers at 62 with a radar gun, but I trust my MaxQ.  I was actually fastest staying in 2nd gear and riding the limiter.  There was no good place to shift to 3rd and 3rd is hard enough to hit in my car without having to concentrate on turning as well.  I ended up coasting for a while on my first run trying to find 3rd before settling on 4th just to maintain acceleration.  My second run I short shifted at around 6200 rpms and could only attain 58 mph so I left it on 2nd for the final run knowing I could not have any screw ups since I had almost blown my lead with a dirty 2nd run and was 1.4 mph faster and nearly a 1/2 second quicker to the end of that slalom.  This was all full throttle and could have been faster with more gear and/or power but such is life with 114 whp.

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Brian Johns
ES 97
'95 Miata R

My datalogs indicate 63-64mph peaks in that slalom, limited only by the car's inability to accelerate with a drive wheel in the air.  The car would slow a little on turn-in from the wheelspin, then accelerate across the diagonal (when I straigtened the wheel out some).  Lateral accelerations in that slalom were around 1.7g, which is right where I achieve 100% weight transfer anyway.  I was not driving it like a slalom because of the way the car was slowing down on turn-in.  I was driving more of a saw tooth, trying to get some speed back between turns.  I'm not sure that would be the right answer in another car, but it seemed to work ok for me.  I would have liked a few more runs at it to try some different techniques.

 

-Chris  

sbrian2:

I was 59 mph as well an my MaxQ and also expected to be faster.  Andy Hollis clocked us ESers at 62 with a radar gun, but I trust my MaxQ.  I was actually fastest staying in 2nd gear and riding the limiter.  There was no good place to shift to 3rd and 3rd is hard enough to hit in my car without having to concentrate on turning as well.  I ended up coasting for a while on my first run trying to find 3rd before settling on 4th just to maintain acceleration.  My second run I short shifted at around 6200 rpms and could only attain 58 mph so I left it on 2nd for the final run knowing I could not have any screw ups since I had almost blown my lead with a dirty 2nd run and was 1.4 mph faster and nearly a 1/2 second quicker to the end of that slalom.  This was all full throttle and could have been faster with more gear and/or power but such is life with 114 whp.

Greg tried shifting our Miata on the first run and said it would not take 3rd. I also attempted shifting it at a regional a few weeks ago and either got 5th or had to gingerly put it in 3rd and wasted a lot of time coasting with the clutch in. Therefore, I never even attempted a shift to 3rd. I just tried to concentrate on catching the raws that Chris, Brian and Nick were putting up without doing it. I got close enough considering Kumho's transition like truck tires.

I was certainly playing with the limiter going into the manuever and also coming out of it. The last gates required a breath off of WOT, but it was right back in the limiter. I have not been able to retrieve our DL1 data to make sure out max speed was the same, but I believe Brians claim of 59-60mph is correct (I think Andy said his gun was 2-3 mph fast).

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~Sam Karp~
1994 Mazda Miata R, ES
SCCA-Milwaukee

alvanderp:

[That was my thought as well, the amplitude of the curve could be different because of the first 2 cones of each wall shortening the exit.  Whether this is a perceived change that the driver thinks is needed or an actual change is hard to quantify but I would bet that the height of the curve is higher than a standard slalom.

Doesn;t seem like they should interfere with your line at all if your on the backsides of the last cone in each group.  Maybe a perception thing?  Mayeb the curve starts to fall off the longer the slalom gets?

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Patrick Washburn
STU Evo - SOLD!
<----- 2009 - Regain the coveted Tri Pod Trophy for the Hiedi's

FWIW, on my best run thru that slalom in the DP Spyder, eeerrrr....EM and DM Spyder, I was pretty much on the rev limiter.   I had to lift a smidge for the last wall, but immediately hit the limiter a bunch going into the right hander.   I also tried going to third on my first run, and was actually slower as I tried a short shift next to the first wall...  Rev limiter is 64 I believe on my car...

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Tracy Ramsey
Team Blenderblaster
2000 MR2 DP Spyder

I can semi convince myself that the layout discussed could be wheelbase/track width dependant more than a regular slalom and the waveform having a sawtooth component.

Caveats: School was a long time ago and I don't do much math/trig critical thinking any more being Mr. Mom.

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Andy Hohl

Thanks Kyle for the drive in the Shelby GT this year

FWIW, here's my 2nd run (best) from Sunday.  The slalom in question is about 17 sec into the movie.  Warning, 10 MB download, and please right click and save as:

http://www.wynveen.org/movies/Peru_Tour_2008_Sunday_Run2.wmv

Have a look, but I sure don't think the walls came into play for me.

-Steve
 

edit: ack, looks like the forum software link thru won't let you save as, at least not with Firefox, so stream away! 

You guys need to get some street tires so you can go faster...or a narrower car. 

My MaxQData says: 61 MPH entry/exit speed for me, dip to 58 in the middle (gut check).  I only did it this fast once.

I wanna know what Matthew's speed was in the Lotus.

From a theoretical point of view, I agree with Larry that the actual line driven is more like an offset slalom, where the "turn around me" cone is about 1-2 feet off the centerline, and spaced midway along each wall.  In fact, you could probably simulate that by taking the middle cone of each wall and moving it out by a foot or two.  Would not change the effective line at all.  In fact, it would probably make it easier to drive.

Have I mentioned how much I love concrete?  Oh, how I miss the grip of Forbes (but not the bumps).

--Andy

PS: Out west, they call this element a "wallom". 

 

Of course, narrowness is the real answer, Mr. Wisecracker! 

Actually, I'm starting to feel better about my slalom speed in the Queen Mary based on the reported speeds here.  I'm also starting to see the light in how the walls (leading cones) force a wider, slower line.  In the slalom formula I have to plug in an offset of 34" to bring the speeds down to those observed, so it is like the center cone in each wall is moved 17" toward the outside.

I guess someone needs to develop a wallom formula.  

-Steve 

I remember we were at the top of 2nd with tire temps in the 90 degree range in AS.  Its hard to hear the revs due to the wind noise but heres my video to give a another look from a different car. I know the rev limiter was hit during all 3 of my runs making the wallom speeds around 56-58.

 

Clicky

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'08 Honda S2000 CR (#94 AS)

mpfannen:

I remember we were at the top of 2nd with tire temps in the 90 degree range in AS.  Its hard to hear the revs due to the wind noise but heres my video to give a another look from a different car. I know the rev limiter was hit during all 3 of my runs making the wallom speeds around 56-58.

 

Clicky

If you are running 275/40-17 A6's in the back, its more like 61mph on the limiter in 2nd, at least thats what mine does according to the DL1, and the CR has the same gearing as the other AP2's as far as I know.  The indicated speed is of course 58mph, but the 275/40-17's are alot taller than the OE tire.

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-- Drew
AS S2000