Data from the 83 mph run.
Video of the 83 mph runs.
This post is a little late since Blogger was down for a while. This is from Sunday's test session. I was able to hit 83 mph. This was a bit of a disappointment. I was hoping to get at least 90 mph. I believe the next test session I will have to remove all the data logging equipment that can be a source of a lot of resistance in the power system. Another problem is that we are running out of room to get the cars up to speed and to slow down. I think a new spot has been found in the parking lot of a mall outside of Houston.
Possible new location for testing. At least 1500' of test space.
Test location we have been using for the past couple months. Only about 700' of running space.
Sunday, June 22, 2008
Tuesday, June 17, 2008
Sunday, June 15, 2008
Today's testing went very well. I was able to get my Eagle Tree eLogger V3 working with the 5Hz GPS module. I wanted to be able to get data on amps, volts, watts, speed and motor rpm. There are a couple interesting things to point out about the data. If you take a look at the detail of the 81mph run data, you can see that the GPS measured a max of 77.7 mph. The radar measured 81 mph. As far as I know the GPS is more accurate in speed (.1 knot) compared to the radar. But since just about every one who is doing these r/c speed runs is using the same type of radar, and I have been using the same radar since I started I will say 81 mph is the max speed reached in this testing session.
I also tried some belted rubber tires instead of the foam tires I have been using since I got this car. They worked very well and they felt like they had more traction than the foams. The problem is that they are slightly smaller in diameter than the foams. This means with the same gear ratio, I will go slower with the rubber tires than the foams because of this smaller diameter.
Since the accident with Greg's leg last week, I reinstalled the vertical stabalizers. These are a huge help at high speeds. The importance cannot be stressed enough. The car feels like its on ice without the vertical stabalizers. They make driving the car much easier and controllable. There was no evidence that blowover was going to happen at these speeds so higher speeds can be tried next session. We are going to have to increase our space were we use to test. The run up area has plenty of room, but the slowdown part of the testing track is getting too short with these higher speeds. We're going to have to move down the track into the "prepared" surface of the drag racing track. This will cause some problems during the runs when the driving surface transitions from the prepared surface to the bare concrete of the shutown area. Hopefully it wont become an issue. We will find out during our next session.
The "X3" should be able to reach into the 90's with this setup on 8s. As soon as I can reach the limits of this 8s setup, I will upgrade to 12s and push the limits of that setup. Since this last weekend of testing, the car feels nice and stable and I will be able to punch it 100%. Check back soon for details.
Sunday, June 8, 2008
I went testing today and made some changes from my last 79 mph run from last week. I needed to get more downforce on the front end to keep the X3 from blowing over. The lexan splitter I added underneath the front bumper definitely helped out but I could still see the car about to blowover around 80mph. I added winglets on the sides of the front to add extra downforce. I also wanted to reduce drag so I removed the spoiler from the rear. I felt like I was getting enough traction so I didn't need the downforce created by the spoiler. But removing the spoiler also reduced stability of the rear vertical stabilizers. I had done some test runs with this new configuration and I encountered significant flutter from the vertical stabilizers at high speed so I removed them. But as you can tell from the changes that I made I would create more front traction and loose lateral stability. This is exactly what happened on this run. The front end was too twitchy and the rear end was very loose. But on the positive side, the car was much faster with the same amount of throttle input as the 79mph run.
You can see in the video that the X3 had changed directions a couple times during the run, but was too close to the center of the track where Greg was filming and the radar gun was setup. I tried to correct but it wasn't quick enough to get out of the way of Greg and the radar gun. At the point in the video where you cant see the X3 is when Greg attempted to get out of the way. The X3's front left side took out the radar gun tripod at 76 mph, caught air, hit Greg's leg and flipped before landing on its wheels 20 feet away. The pictures above are after the accident. I checked over the X3 and I had to tighten some set-screws and she seems Ok.
The importance of the vertical stabalizers can been seen in the slow motion of the video. My next step is to modify the body so I can reduce some drag and add larger vertical stabilizers. Other than that, the car is setup very well. It feels and handles great besides the aerodynamic characteristics. With the X3 on 8s geared 64 pinion 36 spur the calculated top speed is around 95 mph. This is target speed for the X3 with this setup. After I reach around 90 mph I want to change to 12s and really push the envelope of that setup.