Wednesday, March 31, 2010

G/C Setup tips

One of the keys to properly setting up any suspension is the ability to accurately reproduce settings. The Bump adjustment of the Advanced Design shock is based on a reference location -- turning the knob until one of the printed numbers point at a specific point. The problem is that there is no indication of that location on the shock.

Making some kind of mark on the chassis to represent this point makes setting up Bump much easier. I made 4 small triangles and put a pair on the front strut-towers and the other pair on the rear shock mounts.

Friday, March 19, 2010

Suspension setup

Car-related forums are littered with the same n00b question: What coilover should I get for my Blah-Blah-Blah car. Most of the time the poster is only concerned about lowering the car for looks and will never use any of the adjustments available with a coil-over suspension. If, however, you want to really use these adjustments, you've got to learn the fundamentals. You need to know how camber and caster interact as the car turns in. You need to know how ride height changes at one end of the chassis effects mid-corner balance. There are a number of books on chassis engineering and a number of great web-sites that cover everything you would need. Now you may know what each adjustment does, but you won't make proper use of your new knowledge until you learn to think like a test driver and a race engineer. You have to measure and record everything. You have to take copious notes and be organized, methodical and work to a plan. Every session has to be on the clock and all performance measured. Now are you can start to use suspension adjustments to "tune" the suspension and gain real performance results.

What I'm going to describe here is setting up a Ground Control suspension system with Advanced Design Double Adjustable (D/A) shocks. With this system I can adjust nearly everything front and rear: Caster, Camber, Ride-height and Toe.
The shocks are called double adjustable because it provides for two separate resistance adjustments, one changes the shocks resistance to being compressed (Bump) and the other changes the shocks resistance to being extended (Rebound). Single Adjustable shock have a single adjustment the usually only changes Bump resistance. The ability to adjust Bump and Rebound separately is tool that is use to change chassis balance on corner-entry and on corner-exit. Springs and Bars are use to change steady state chassis balance and shocks are used to adjust dynamic chassis balance.

I'm using Bump and Rebound because the first letter corresponds the the color of the knob used to make that adjustment. Red is for Rebound and blue is for Bump. These knobs stick out of the top of the
shock so all adjustments are made under the hood or in the trunk and not from the bottom of the car.

The Advanced Design shocks described here have very different methods for setting Bump and Rebound. The blue knob (Bump adjustment) has three positions and a small detent to indicate the correct position. The red Rebound knob has three full turns of adjustment limited by small stops at full stiff and full soft. Clockwise is always stiffer on these shocks.

Baselining:

This is where you develop a repeatable basic setup for the car. All subsequent adjustments are made from from the baseline. My initial baseline came from Ground-Control and is basically an alignment/ride height guide. I have that on the car now. Once the ride heights are determined all the other adjustments won't alter the corner weights so
I want to get it set before I corner-weight the car.

I want to understand the performance envelope of the shocks so I plan to do a number of short sessions while testing full-soft through full stiff for both Bump and Rebound
.

F-ing weather

For the second year in a row all pre-season testing has been lost to a series of spirng storms. Tomowwow is the last test day and Denver is now expecting 8-12 inches of snow today and tonight.

This means that the first few races will be a thrash trying to get tire temps, alignment, corner weight and balance sorted out instead of trying to drive for the win.

This is why we are going to move back to California, life is too short to have a few days of weather dictate the success of the entire racing season. Fuck this place.

Thursday, March 11, 2010

Continental Divide Raceways, Castle Rock, CO

For years I've heard the rumor that there was once a "real racetrack" in Castle Rock but that it had closed many years ago.

Recently I learned the racetrack was called Continental Divide Raceways and was located just 4 miles south of downtown Castle Rock. It was a 2.8 paved mile road course, 0.5 mile oval and 1/4 mile drag strip that opened in 1959. Racing continued until 1979 and reopened in briefly in 1981. The land was sold for development and although little has been developed even now, the asphalt surface was plowed up to ensure cars would not return.

Using Google Earth I was able to find the location of the track. Although the pavement is long gone, the location had a distinctive grandstand cut into the hillside which is still visible. Finding the grandstand showed where the drag-strip was and it too is still visible.

Events held at the track include USAC Road Racing Championships, USAC Stock Car and Indy Car events, and SCCA Trans Am.

As early as 1960, USAC held a Road Racing Championship event at the track. Carrol Shelby in a Scarab Mk II held off 35-40 other drivers for 36 laps to take home $900 in the Continental Divide 100. Attendance was recorded as 8,500. Here is an interview with Carrol Shelby discussing the 1960 race at CDR

Though lightly attended compared with the Riverside and Laguna Seca events, the 1961 even still attracted Ken Miles and Bob Holbert and their Porsche 718 RSs and collection of other including Ferrari 500TR, Maserati Tipo 61 and something called a Devin Volkswagen.

By the mid '60s attendance had climbed to over 10k for major road racing events.

The Rocky Mountain 150 held July 7th 1968 attracted Al Unser, AJ Foyt, Lloyd Ruby and Mario Andrett. Ronny Bucknam lead from pole until a half-shaft failure on lap 23 gave the lead to A.J Foyt who held it to the end.

An entry list for the first of two SCCA Tran-Am races held August 26th, 1967, is a Who's Who of American Motorsports:

Mark Donohue, Peter Revson, Dan Gurney George Follmer, Jerry Titus and Milton Minter were all there. Titus took the win in 1967 and Donohue won in 1968

Evel Knievel performed at CDR July 30th 17972.

The last recorded race I find is a Winston West event August 15th, 1982 won by Rick McCray

According to the Chicago Herald-Tribune Driver Jim Mulhall of Littleton was killed on June 8th 1969 at the 1969 Formula A Grand Prix, in a accident that later took the life of mechanic Michael DesJardins.

According to witness Paul Bredenberg;

"I was also at that race. We went to the '69 and '70 Indy car races and the '69 First (and only) Annual Denver Post Grand Prix for SCCA Formula A cars. The Post GP was the eventual demise of the track. The dragstrip was used as the front straight ("The Andretti Straight") and the return road was the pit road. They were separated by a row of 55 gallon rain barrels that were to be filled with water and cabled together. Jim Mulhall was a small-time local Corvette racer who had a chance to drive one of the Indy cars that day. It was a Halibrand Shrike chassis and was offset for oval track racing. It was a yellow #77.

During the race, an absolute DELUGE hit the track in the form of a typical spring storm. Cars tried to stay out on their dry tires but it was senseless to do so. Mulhall's crew signaled him next for rain tires on the next lap. He took one hand off the wheel to signal that he got the message off the board, hit a puddle and aquaplaned 270 degrees, so that the back of the car headed towards the barrels at about a 30 degree angle.
Mulhall's car hit the barrels at about 155 mph.

Guess what? Somebody forgot to fill all of the barrels with water! Barrels went flying into the pit area and the cable snapped and hit Mulhall's helmet, breaking it into several pieces. The car went across the return road, hit the Armco barrier and slid to a stop almost at turn 1 ("Foyt's Corner") with a smashed barrel underneath it. Mulhall died on the way to Swedish Hospital without regaining consciousness and three people in the pits were hurt.


After the lawsuits flew and damages were paid, Sid Langsam lost his heart for the track, and then later was diagnosed with cancer; I think it was prostate cancer, but I'm not sure on that."


Today, the Colorado Region of the SCCA give an award for outstanding contribution to racing in Colorado called the Sid Langsam Award.

Here is a video by the Castle Rock Historical Society showing some great period racing at CDR

Here is video of a sprint car race on the CDR oval in 1960

Wednesday, March 10, 2010

Curbs?!?! on Sunday?

It looks like HPR is going to be closed on Sunday to install curbing. Really on a Sunday? Seems a weird day for construction on a racetrack.

HPR Shakedown

On Sunday I'll be taking the car to High Plains Raceway for a shakedown/test session. I hope the weather holds. Beyond making sure the thing works on the track, I'm focused on getting the alignment and overall balance sorted. The main tools will be my new (to me) Longacre tire temp gauge, stopwatch and driver feel.

Tire temperatures will be used to make sure the front and rear camber settings are optimized. Since I've been running Nitto NT-01 for almost a full season I have a handle on the optimum pressure, but I'll be open to making small changes. The primary tuning tool is the driver. I'm going to focus on setting up the car to be comfortable -- aiming for a little oversteer in entry and a little understeer on exit.

This is why double-adjustable shocks are so important, the ability to change how the car behaves before and after the apex. Triple and quad adjustable can also change the behavior at high and low speed both before and after the apex.