Pictures of the X2 progress in chronological order

Saturday, June 23, 2007

Video: Ground test #2

Here are some more test runs of my project "X2" speed run car. You can see that I am still having stability issues and oversteer problems. At the end of this video I almost run into John who was filming the run.
This is a test prototype of the body and wing. The body is made from fiberglass. The body attaches to the chassis with button head screws on the sides. The wing is a NACA 9509 airfoil section. I made this wing in college for wind tunnel testing.

The weather held out for John and I to do some testing. There are a couple changes I made since the first ground test. I made a longer chassis out of carbon fiber instead of G10. The G10 chassis was my prototype chassis. I used it to place my components and see if the layout was correct. I found that the car has too much over steer. I have been trying to remedy this problem with much stiffer springs in front. This did help a bit, but I found that carbon fiber has a much better resistance to a torsional load than G10. This means that the chassis bends less and the suspension can do its job more effectively.

The tests didn't prove as promising as I would have liked. I still cannot get my speed up above 30 mph. The steering is way too sensitive and it makes the car spin out. It feels like significant over steer. You can see this in the video. Right at the end my car wanders towards John and I almost hit him.

My new Futaba 3PM 2.4GHZ radio does not have nearly as much range as my very old Futaba 3PK PCM system. The 3PM gave me only about 400' of range. Very disappointing. I was hoping for much more.

After my disappointing testing on Saturday, I also didn't have a very good day today (Sunday). I was testing different front camber/caster settings to help remedy the over steer problem. I go and test a camber change, stop the car, make another camber adjustment, then I go to turn the car on and now my speed control wont arm my motor. I am not sure what the problem is at all. I tried to recalibrate the radio, I tried my old radio and I still cant get it to arm the motor. So at this point I am out of commission until I fix the speed control.

Design Update

Here is the new stretched carbon fiber chassis next to the old G10 chassis. The new one is 50mm longer in the wheelbase.

During my first couple of test runs, I had a lot of difficulty getting the car to track straight. It was tough to get on the throttle and get the car up to speed without the car getting very squirrelly. I decided to lengthen the chassis and make it out of carbon fiber instead of G10. The carbon fiber has much stiffer properties than the G10 and it seems like the chassis doesn't want to warp as it did with the G10. This lets the suspension do its job

Tuesday, June 19, 2007

Testing rained out this past weekend.

This is what it looked like 5 min before it started to pour
Here is John's car doing some high speed runs to check out the running surface.

This past weekend was pretty much rained out. John and I did get to go out to the testing area (Best Buy parking lot). We got a couple runs in but after 5 min it started to pour. This weekend looks promising. Much better for testing.

I got my new Futaba 3PM 2.4ghz transmitter installed. I plugged everything in but now I am having problems with the throttle again. It doesn't sense neutral. I have to hold the brake to keep the car from rolling. I am trying to set it up so it doesn't do this. I also installed much stiffer side springs on the suspension. I was using the silver 8lb/in springs before, now I am using the copper 16lb/in springs. This drastically improved the way the car handles. With the added weight of the extra battery, the car would want to keep swaying back and forth and never go in a straight line. With the stiffer springs, this has almost disappeared.

Update: I was able to adjust the throttle trims and subtrims to get my new Futaba 3PM to work with my awesome Castle Creations HV-110.

Saturday, June 9, 2007

Video: First low speed test run of "X2"

This is the first low speed ground test of my project "X2" Insane Speed Run car. This test was to mainly check for radio range, ESC setup and testing area. I didn't even have the body on for these tests. In this video I wasn't driving the car, John Stranahan was driving so I could record the video of the car in action(You can see him doing some donuts in the early part of the video). This was the fastest he or I let the car go. We didn't want to go too fast for our initial tests. He helped me a great deal this morning with the final preparations to get the car running. A couple things to note; The car is completely silent. Since there are no gears the only sound the car makes is when it scraped some rocks on the ground or the chassis scrapes from bottoming out. The biggest problem is setting up the HV-110 for the car. Now there is nothing wrong with the controller. The Castle Creations HV-110 works perfectly, its just that its been designed for planes and not for cars. Its difficult, but Nic Case has been helping me set-up this controller. The problem is that I have to hold the brakes or the car will take off. Basically, full brakes is neutral and anything less than full brakes is throttle. Nic Case has offered a solution:
I just read your post.
If you need a little help tuning your radio with the 110----- here is what I know............

(the HV is for planes, so it naturally wants to go from 0% to 100%-- like a stick. But a pistol radio goes from -100% to neutral to + 100%------------) you will not be able to actually get it to "coast" , it will go from 1% forward to brake--- no neutral.
The trick is to try to the trigger to fell like a "car"

First, in your Castle Link, set it up like the attached.

On the radio it self, turn the throttle end points down to 75%.
From here turn you car on (4s- no tires) and play with the sub trim to try to find neutral.

If you can not adjust the radio to find neutral at your trigger---- you may have to hook a rubber band round the trigger to pull it to full brake.

Hope this helps
Good luck
With these 8s Thunder Power cells and this HUGE Neu 2215 motor, the car will break the tires loose at just 1% throttle. In this video, John and I never got more than 5% throttle out of this car in fear of spinning out due to the massive power.
The black tire marks are from the traction compound that we applied to the tires earlier. You can see it coming off the tire and absorbing into the asphalt surface.
This is the testing area. Its a newly paved parking lot. This area in the picture is about 100 yards. You can see John in the distance testing radio range of our transmitters.

The first low speed ground test of my project "X2" went really well. Master Mechanic John Stranahan helped me out this morning. We didn't test for high speed but we tested the electronics, the range and checked out the testing area.

I think this first test was a success. The car was moving great and I didn't break anything! The next order of business is to fix the throttle issue. Also, I have to complete the rear fairing and vertical stabilizers. The next test will include the aero package and higher speeds. Hopefully next weekend the weather will be just as good as today.

Ready for road testing

Well, its about 12:45 am CST Saturday morning. I am going to go testing this morning at around 8am. The electronics are all together and at this point the body still needs a little trim work so I didn't include it in the pic. I intend to run Thunder Power 3300s in 8s and do some low speed testing to get the transmitter dialed in and the speed control calibrated. Keep in mind that this Castle Creations HV-110 is designed for use in planes. So setting up this thing in a car is a task. I hope to get some pictures and video of the testing and I will post the results here. My friend John Stranahan will help me out with some chassis tweaking, electronics set-up and timing. We will use a quick and dirty way of measuring speed. We will measure out a set distance and time how long it takes to go that distance. Hopefully everything goes well. Wish me luck!