Part 1: Camera Placement
Video can be a valuable tool if it is used appropriately. Search the internet and you will quickly find many videos of your favorite track — some more useful than others. The good ones can help you learn the line before you drive the track for the first time. Others are intended merely to show the world that you drove on the track. If that’s all you want out of video, then stop reading, this article isn’t for you. This article is about learning from your videos. So let’s build up to it, starting with camera placement and then talk about data analysis.
Before you place a camera on your car, think about what you want to get out of it and what restrictions there might be that limit your options. Do you just want to show your friends the track? Do you want to learn the line? Do you want to see how close your wheels really are to the apex on certain corners? Do you want to record what happens in front of you? Or do you want to see your inputs as you drive around the track? Those decisions will help guide camera placement.
Compare the views from the two videos below. The first one is mounted inside on the front windshield (old, non-HD camera) and the second (iPod 4G) is positioned behind the driver. Driving through some fluid, understeer quickly becomes oversteer (and oversteer again). How did the driver? You cannot tell from this view.
In this second video, we see the driver quickly catch the over-steer and accelerate out of the corner, showing the importance of quick hands.
Camera Position and Live Timing. Most High Performance Driver Education (HPDE) events run by car clubs have rules against live timing. You will need to position any recording or timing device in the car in such a way that it does not give live feedback to the driver. For external cameras, many clubs restrict the use of suction mounts, requiring a hard mount. Check with your club before you buy. Even if suction mounts are allowed, be sure it can withstand the wind and vibration of being driven at speed. Position the camera so it does not impede the driver’s vision and locate it in a place that it is visible to the driver directly or in a mirror. Never consider externally mounting a camera you aren’t willing to sacrifice to the Goddess of Speed. Low positions such on tow hooks are visually interesting, but not very helpful for learning. Better is mounting on the roof along the center-line of the vehicle, above the interior mirror with a view of the front hood and fenders. This will show car placement on the track and traffic directly ahead. This placement creates a video that is a good tool to show general car placement, learn a track, and to film following a car directly in front of you. Because it does not capture driver inputs, it is not our preferred placement. If your camera is light and small enough (Replay XD 1080 Mini for example) consider using a suction mount to place it on the windshield inside of the car and tether it to the mount for the passenger visor. For cars without rollbars, this is often your best option. It offers a similar view as on the roof and the camera is protected from the elements. It can easily be controlled by the instructor from the passenger seat. We’ll start out on the Summit Point Main Circuit.
Windshield Mounted View. Positioned behind the interior mirror, this is the view you get of the track. This view is useful for general track orientation. But you really can’t learn that much about the driver’s inputs from it. [Note: I’m using an old camera that is not HD. The new cameras integrate with the data overlay much better.]
Same Lap with Data Overlay.
By adding telemetry data from Harry’s LapTimer and data from PLXdevices Kiwi 2, now we start to get a feel for use of throttle, corner speed, lateral forces, and gear selection.
Same Lap with Camera Behind Driver. In this video, we’re using an iPhone 5S in an Optrix XD5 Case mounted to our rollbar. By mounting the camera behind the driver, now we start to get a feel for driver input. Is the driver struggling to maintain position because the seats are not supportive. Is the driver looking into the corners? How are the driver’s hands on the wheel? If you don’t have a rollbar or harness bar, you can get a similar view using a head-rest mount such as the CruiseCam Mount.
Same Lap with Picture in Picture Finally we can put it all together and see both the driver and the road ahead. Harry’s LapTimer (HLT) has the ability to control certain secondary cameras via Bluetooth, such as a second iPhone, an iPod G4, or GoPro Hero3. In this case, we imported and synced the video from our Replay XD camera within the HLT application
That second camera could be showing a view back toward the driver from the front, it could be showing feet on the pedals, or it could be a reference lap to compare one lap (or driver) to another. You are really only limited by your imagination (and equipment).
Part 2: Apex and Entry Speed Analysis
In Part 1, we discussed camera placement and capturing data. In this post we’ll explore what we can learn from the data we’ve captured. The track this time is the Shenandoah Circuit at Summit Point Motorsports Park. This is a challenging 2.2 mile, 22 corner road-course used primarily for driver’s education events that features a dimensional replica of the Nürburgring-Nordschleife’s banked Karussell turn complete with 20 degrees of banking (but without the Graffiti).
The configuration in use this day omitted the three chicanes and used the short Range Straight between turns 9 and 11. (I’ve driven more than 40 days on this course and I’ve never seen cars use the chicanes.) It is not a very high-speed course and the walls do seem very close at times, but I really enjoy it, especially in the MINI. This lap at 2:06.75 is about average for me on this weekend. The fastest of the weekend was a 2:04.67. (My best ever in this car was a 2:01.78 but that was on R-comp tires; I was on street tires this weekend.)
Video was captured on a Replay XD MINI 1080 mounted on my rollbar; data was provided by a PLX Devices Kiwi WIFI; positioning was provided by a Dual AV XGPS; and timing came from Harry’s Laptimer (HLT) on my iPhone. The video was edited in Quicktime and later added to the HLT dataset on my iPad.
In this post, we’re going to focus on an examination of cornering speeds. This post isn’t about outright best lap times, rather improving driver smoothness and carrying as much speed as possible through the corners. Lap time is just one of many ways to measure performance. Using data from HLT that was exported to Google Earth, we can plot cornering speeds and lateral G-forces over the track-map. We’ll compare the two laps of this weekend to the reference lap of 2:01 (fastest lap last year in R-comp tires in this car). The color bars are supposed to represent the direction and intensity of the G-forces: Green is 0.4 – 1.0 G; Yellow is 1.0 – 1.25 G and Red is greater than 1.25 G. Our goal for the weekend was to see how close we could come to this level of performance using street tires.
The best lap of the weekend on street tires was a 2:04.67. (The spikes in the data show how much less composed the car was on street tires at these speeds than on the R-comps the previous year.)
Here’s the lap we’re trying to analyze, 2:06.75. Let’s try to find where we’re losing almost two seconds. Lower apex speeds mean lower exit speeds, leading to lower top speed at the end of the next straight. We know that we can’t expect the same level of grip from these street tires that we got with the R-Comps, so let’s look where we might make up some speed.
We can then overlay the 2:06 lap on the 2:04 lap to help see where we’re losing time. The data suggests our theoretical best time is closer to 1:59, even on street tires. In HLT, the image is dynamic so you can drag your finger around the course and see the plots in the data, you can get a similar result using the HLT data export and looking at your laps in Google Earth.
- Start with Point A, The Loop. Both the reference lap and the 2:06 lap show an apex speed of 42 MPH which is interesting considering that the reference lap was on R-comps. This shows that there’s a lot of grip on corner entry because of the crown on the road. Use it to your advantage. (This was actually the one spot where the 2:06 lap was better than the 2:04 lap indicating I could have done better than 2:04 had I carried more speed into the corner.)
- At Point B, the Stone House Straight, I carried a lot more speed into the Hook on the 2:04 lap. As the weekend progressed I gained confidence in braking later, resulting in the same apex speed, but the line exiting Turn 8 was much better in the 2:04 lap, resulting in higher apex speed at Turn 11 (Point C).
- That extra speed carried all the way to the entry of the Karussel, Point D. Through the Karussel and into the Karussel Esses, however, I actually had better speed on the 2:06 lap since I had a better exit from the banking. (You can see the slight movement to the inside of the Karuessel on the exit where I lost speed heading up the hill — red spike in the wrong direction).
So what’s the take-away from this analysis? I can brake a little later and carry more speed into the apex of the Loop (A). Likewise, I can carry a bit more speed and brake later into the Hook (B), concentrating on getting a good launch out of Turn 9 (avoiding the curb on the inside) to carry more speed into Turn 11, carrying more speed at the exit (C) which will result in more speed at the end of the Bridge Straight leading to the entry of the Karussel (D). In other words: Brake later, brake less. Words to live by.
Part 3: Traction, G-loading, and Getting the Power Down
For the final installment in this series, we’re going to look at what the data is telling us about how hard we’re trying. To minimize time on the track, the drive should spend as much time at full throttle as possible; brake as little as is necessary to turn; and be trying to get back to full throttle as soon as possible. There is no coasting involved, yet we all know we coast from time to time. Now with data acquisition, we can start to see where we are doing it, or more appropriately, where we’re trying to put the power down but it isn’t working. For this analysis, we’re going to look at the third track at Summit Point, the newly expanded Jefferson Circuit. (For a detailed analysis of the new Jefferson Circuit, click here.)
As we mentioned in the post analyzing this track, the color on the path of the car shows acceleration (green) or deceleration (red). Note that deceleration might just be lifting as in between 2 and 3 or the apex of 4 or 8. Green speed readings on the track show max speed before deceleration and red shows apex speed. The bars in each corner show relative lateral G load. Green bars are .4 to .8 Gs. Yellow bars are .8 to 1.1 Gs. But there are a couple of other charts in Harry’s Laptimer that inform us about traction events. First, here’s what that lap looks like:
When we look at the overall picture of traction on this course, we see our max performance summer tires are performing pretty well. We are pulling a maximum lateral load of 1.22 Gs in the tightest corner, Turn 7. The first chart shows our overall traction circle which is a little better than expected for a street tire.
The second chart shows the maximum lateral loads on the corners. It’s also showing us the areas of the track that are unsettling the car. This is similar to the Speed chart that shows where we’re having trouble putting the power down.
When we start looking at the Speed Chart we start to see areas where we’re having trouble making a clean transition back to full throttle at the apex of certain corners. When the peaks of the lines look like Vs, then it’s a smooth transition. Where you see Ws, then there’s a problem.
Compare the areas with the arrow to the circle and the square areas. The arrow shows the apex of Turn 1 and a very clean transition from deceleration to acceleration. The orange squares show the effect of the rough road surface before the apex to Turn 6. Not much I can do about that. But take a look at the green circles. This is the trick Turn 7. It’s a decreasing radius corner where the entry is a bit off-camber, there’s very little grip at the apex and a tricky transition immediately into Turn 8. I’m not making that transition very smoothly and am not able to steadily accelerate through that corner. There’s a corner I can work on. Here’s another way to use the tool:
This chart is showing a comparison of two laps. The faster reference lap is in orange. The lap being studied is in gray. Until Turn 7 this lap was ahead of the reference lap. You can see the difference in speed at point A and the difference in time at Point B. But I over-cooked Turn 7 and by the time I was in the braking zone for Turn 11, was already behind. By the time I got to the end of the back straight (Point D), I had to lift and let another car pass. This just goes to reinforce the old adage of “slow in, fast out.” By being “fast in, slow out” of Turn 7, the rest of the lap was compromised.
“Like” us on Facebook (and remember to check the box to follow our posts.)