Penny-pinching car geek's guide to racing, track days, and car build. DIY projects, product reviews, and interviews.

Tuesday, March 30, 2010

Gainesville Test Track Day Repost - 03/27/10 - Importance of Data Logging

I call the Gainesville Track a test track, but I think its official name is "Gainesville Road Course." Road Course to distinguish it from the more famous drag strip.

Yesterday was supposed to be my girlfriend's first track day, but one of her legal assignment due dates was recently announced to be during the track session. So I went by myself.
Track conditions: No rain. Min 44 Max 77 Fahrenheit. Not much dust or rubber on track (Glad not a lot of people run R-comps here)

I love the morning silence before the first car goes out. This particular morning I arrived at the track to find the gates closed. And I saw a bunch of cop cars on part of the course. Uh-oh. Is the event canceled? A white GTI pulled up behind me driven by a kid in his mid-teens with his father next to him. Cool! When I was sixteen, I never even dreamed of going on track. In fact, driving was something very foreign to me. I think its very good that he is getting track experience at an early age. Lucky to have such a cool father.

My worries proved me wrong and people arrived to open up the gates. I always arrive nice and early to the track. I used to spend this time to socialize with other drivers and make new friends, but in the past year I decided to spend that time by myself. Driving is not a team activity, and I believe that pre-session times are best spent alone. Now I spend that hour or two before the driver's meeting focusing on what I am going to be working on that day. This time I was going to work on hitting all of my apexes, looking ahead and learning the new setup.

I mounted a camera to my right fender to see how close I get to the track edge. Turns out this isn't needed since I should be getting right onto the edge of the track and hanging off a part of my right wheel. Thats when I knew I was getting close enough. Sorry track owners for wearing out the tarmac edge.

First session out. It took me this whole session to get used to the grip levels. Car understeers a bit less, but the on throttle oversteer is gone. I would still like the car to handle a bit more edgy. This is because my low horsepower and my viscous LSD (which by the way, is like not having one) isn't able to overcome the increased rear traction. With more front end grip I should be able to balance the grip levels and drive a more edgy and faster car.

Second session out. I'm used to the grip levels. In this session the temperatures were probably 50 degrees. I did my fastest lap in this session, even though I was no doubt driving better in the later sessions. Still missing apexes on the right side. Fastest time of the day, no doubt because of the air temperatures. I forgot to do a cool down lap and my brakes were smoking! Always remember to do a cool down lap. Fast time is 1:02.7

Third session out. Figured out points of the track I'm leaving time on and added more throttle in those sections. I'm consistently hitting my apexes. Fast time is 1:02.9. Here is a video.

Fourth session out. Grant drives it for a 6 lap stint, sets benchmark time. Had trouble turning the streering wheel because his knees touched the steering wheel. His fast time is 1:01.8, consistently. 

I'm glad Grant is there to drive my car. Someone at the track asked me "he must be a really good friend that you let him burn you tires up." But to me setting a goal is much more important than tires. Track days are not competitive and this is the only way I can push myself to get better.

Fifth session out. I got caught up into doing a fast lap and forgot what I was supposed to be working on. Missed some apexes but I'm consistently going over the curbs I want to go over, driving on the edge of the road when I want to. Discovered that going over the outer curb setting up for turn 5-6 unsettles the car and results in oversteer.

Importance of Datalogging
I went home and watched the video-overlay. I've found that watching these videos is different than looking at my GPS log. Something about seeing my speed and accelleration with an actual visual of the track makes things click. Seeing how much past a certain visual reference mark on the track helps me rememember the sensations and the car behavior that I cannot see from the data. For example, trun 2 and 3 are the same radius, but turn 3 is more off-camber. Why am I going a few mph slower in the first one? I figured out while driving on the course that I can go full throttle in turn 2 entry, but it took me looking at the overlay to realize I should be getting on the gas much sooner.

This time I failed to record Grant's stint in my datalogger, so I compared the P-box data of our prospective runs.
As usual, he is braking much harder for a full half a second shorter in the major braking zones of turn 1 and turn 4. I can't brake that hard yet. Another thing I could not ascertain without datalogging.

Car changes since last event
-Spec miata exhaust installed
-Front ride height increased to 13"
-Bilstein 1994 R-package shocks installed
-New RT-615 tires 

-205mm wide tires on 15x7 wheels
-Track width increased by 16mm

Car Handling
-Still some understeer
-Less on-throttle oversteer

Setup Notes
-More front camber needed
-Ascertain affect of higher front ride height and lower front ride height at the same camber level
-Ascertain whether or not it is faster to let the V-LSD do the work, or just wait a bit to get on the gas. Hypothesis is that accelerating early enough to have a  couple of seconds of inside wheel spin until the LSD kicks in is faster, since it doesn't result in any oversteer and scrub off speed.

This event, I felt like I extracted much more out of the track; found some more of the hidden speeds. I think from now on its going to be all about consistency, smoothness, and car setup. I understood the importance of looking ahead couple of corners much more. I hope all of these things move over into my driving when at other circuits.

Sunday, March 28, 2010

Last Minute Ride Height Adjustment - using Coil Spring Spacer

I did this Friday, a day before my track event. Track day report will be posted soon!

You may remember from my previous entries that my left front tire is rubbing when given a good amount of steering input. A little bit of rubbing is fine, but I was rubbing pretty bad in right hand turns. I found out that the outside edge was rubbing on the fender, when I mounted my camera on the fender. Before, I tried sticking my hand out with the camera but the angle wasn't right. Don't try that at home!

I spent a few hours rolling and pulling my fender with a PVC pipe. I didn't have much time because I was trying to solve my problem a couple of days before the track day. My car already kind of looks like crap so I didn't mind my bad fender pulling job. It wasn't going to work. Time to raise the ride height. But Doh! I don't have an adjustable spring perch.

I went to Advance Auto Parts and picked up a coil spring spacer. These spacers are supposed to fit between the coils of a spring and effectively remove that spring. I wasn't going to do that, but place it on the bottom or top spring perch. I sliced them in half, cut them down to the appropriate circumference (if you forgot everything you learned in middle school like I do sometimes, that is Pi*2r). I drilled holes into them to secure the ring with zip ties. 

Installation procedures: 1. Remove shock shaft nut on top of the suspension 2. disconnect sway bars (to save time, jack up the entire front end and disconnect on both ends so re-installation will be easier) 3. pry the upper control arm down 4. move spring up and slip in spacer on the bottom shock perch. 5. secure zip tie. You will need three limbs to do the last three steps, so a friend can help a lot.

They don't sit flush on the perch. Make sure the holes are drilled far inside so they don't rip, and that you tighten the pretty well. But not so that the zip tie will fail. On testing, the tires stopped rubbing at mild speeds, and didn't slip off. They held up fine at the track day as well. I don't recommend this though, but it sure beats getting a ring machined for 50 bucks. Do this at your own risk!

Final ride height: Front 13" Rear 13"  (front was raised about 0.5 inches)

Wednesday, March 24, 2010

Roll Bar Camera Mount - Don't be a Sucka!

In preparation of my track event, I decided to make a roll-bar mount. If you've ever shopped for roll bar mounts, you know how expensive they can be. They can range from 30 to 85 dollars. Last year, I played around with an idea for a hobbyist level motorsports video service business. The idea got nowhere and I really cannot say I know anything, but I did realize camera mounts have a very high profit margin. For example, I am currently looking at a brand-name collar mount for a small, lipstick camera on a vendor's website. Price is about 70 dollars (!) The collar can be bought at McMaster-Carr or your local Grainger store, and the swivel mount can be found online. Even at consumer prices, the two components can be ordered individually for less than half the list price of this particular mount. So, I encourage you to try and be resourceful. Many products out there are merely a combination of off-the-shelf parts with a crazy markup.

Some of the more expensive stuff allow a bit more flexibility in the angles than the instant design. However, when mounting things on a tube you should keep in mind that the mounting surface itself is a pivot axis means. Therefore, you only need one other axis to do cover almost all angles. For most of us, we only need an angle that shows some of the interior and the track outside the windshield. I am no exception. Additionally, if I wanted to run another camera at an angle that the roll bar mount cannot do, I can run my lipstick-type camera with my suction mount. Regardless, any shortcomings of this design is overcome by the sheer simplicity of this mount and more importantly, by its low cost.

Things you need
#5 Conduit Hanger - (a.k.a. pipe hanger, pipe clamp)
Targus 6" Table-Top Tripod
M4x.70x16 machine screw
Optional but recommended: 
Small piece of pipe insulation or strips of rubber (1 inch thick donut)
Two small rubber/neoprene washers

First, unscrew the sigle screw on the bottom of the swivel where the tripod legs meet. Two plates and a small o-ring will pop out, along with all of the legs. Save these items.
Optional step: Remove the adjustment bolt and nut in your clamp and paint it to your favorite color. It will see heavy use so I recommend using something really tough like rustoleum black primer. I painted mine red for that ricer look.

Second, screw in the clamp to the swivel using M4 screw and the plates. You can toss the o-ring and not use any rubber washers, but I used them in hopes of some vibration isolation. Loc-tite is an option, but to keep the screw in place while being subject to heavy vibration, I recommend using the o-ring and neoprene washers. Although the bulk of the vibration absorption should happen at the clamp, I think the use of these rubber parts may even help improve picture quality.

Here is the order I used: Swivel | O-ring | Plate | Neoprane Washer | Clamp | Neoprane Washer | Screw head

This order made the most sense to me. But whatever you do, keep the o-ring. It compresses as you tighten the screw, which makes the operation of the tightening knob which you use to secure the swivel much easier.

Third, install the roll bar mount. For a more complete product, you could glue in rubber strips to the inside of the clamp. I am just going to cut a piece of pipe insulation and mount the mount over it. NOTE: I will upload a picture of the roll bar mount installed shortly.

Simple! Best part is all of this only costs $12 after tax.

Credit: I did an internet search to find this design. It is not my idea; I'd like to credit user "tabasco" from forums for this idea. I almost always ask permission to post any information or picture regardless of existing copyright, but this time I haven't. Also, thanks Matt for setting my head straight..

PS: Bonilla interview is still pending, confirmed by him!

Update: I recommend using a better ball head/pan head. This ball head is a bit too particular. The ball head housing is made of aluminum, and the screw is made of steel. So if you tighten it too much, it will strip. If it is too loose, the ball head doesn't secure itself. Keep this in mind when tightening the screw so you will not strip the threads of the housing! I recommend using another ball head. 

Here are some recommendations: Walk-mart sells the Targus Digital Camera Accessory kit which includes a similar tabletop tripod, camera pouch, camera cleaning kit and LCD protectors for ten dollars.. The tripod isn't as high quality as this one, but the ball head looks more solid. I haven't tried it yet. Or you can just buy a good one from your local camera supply store.

Also, I recommend using rubber for the mount's vibration isolators. The pipe insulation is not grippy enough.

Thursday, March 18, 2010

St. Patrick's day post

A day late I know. Chris Cullen linked me this video last year, and he had a funny idea to post it for St. Patty's day. Warning: harsh language

Wednesday, March 17, 2010

Spring Break

So I was in California for the past week. I had two purposes. First was to get a bit of vacation time. But most of my trip I was thinking about a job interview at a small but successful law firm. My Formula SAE teammate Jerome, who had done a bit of work for them hooked it up. Thanks Jerome! As non-engineers at FSAE, we used to do a lot of work together. Sitting there in the conference room during the interview with Jerome reminded me of those times at SAE. Jerome is a co-owner of Autodolce, specialty performance parts company. They have a line of premium brands for European, American and other import cars.

I learned a lot about the firm's practice; trial lawyering straight out of a movie. The office is located right on the waterline in Southern California. Beautiful. The firm focused on automotive litigation as plaintiffs against large auto manufacturers. The lead attorney, who basically does everything in the firm, is a car enthusiast and does track days regularly. His company is renting button willow for the six people who work there. Very cool! He said he is going to be hiring pro drivers to coach the group. Anyways, I did not get a job offer but I was told to contact them at the end of the school year; so lets keep the fingers crossed. I did learn a lot about the field though.

I took my girlfriend to indoor karting for her first time out. I hadn't been to Miramar Speed Circuit since mid 2008. They changed the course layout. I was about half a second behind the fastest guy in my session, who worked there. I could see where I was missing out on speed; and sadly, I couldn't clean up those parts because I literally needed more kart control to tidy up my lines. Sliding around the seat didn't help either. Need more seat time.

Good news is that my girlfriend, on her first time out was only a second behind me. She was fast enough that she gave me somewhat of a race through a couple of sections! I know a lot of that is her light weight but someone on their first time out is usually over four seconds slower than me per lap. I'm going to have her drive with me in my next track day, as soon as I solve my tire rubbing problem.

I also got to have dinner with my friend Matt Wilson. Matt is a brilliant engineering senior at UC Irvine. He is well on his way to MIT. He is the guy in the background of my hobby who have done modeling and simulations for me when there were ambiguities I needed to resolve. For instance, he ran a simulation and figured out my seat mount is barely aequate in side impact situations. The holes deform too much. It was very nice to see him.

Thanks to my friends that came with me and all the friends that I got to see again. Special thanks to Gary, Grace, Jarrod, James for their hospitality.