Saturday, August 18, 2007

Matt Shumaker testing updates: capped tires are awesome!

Here are some modifications Matt is working on:

I have the body off the car and I am going to lengthen it by 1.5 inches, increase the chin spoiler leading edge length, and increase the height and length of the side air dams. The side air dams will be Lexan instead of CF because of their size (for esthetic reasons).

With the body off, I decided to do some gyro programming and overall drive train torture testing. In my testing (60 to 65 mph on the street in front of my house), I learned more about the car. #1 This is actually a great drifting car as long as I stay under 25% throttle. #2 The cap tires grip phenominally when they are very hot. #3 Cap tires have a higher chance of failure when hot.

I blew out my right rear cap doing some drag car launches. I was trying to get a better feel for the car under accelleration. My wife was watching when I told her "See that accelleration a crazy wheel spin?"-----"That was less than 50% throttle." Then I gave it about 75% throttle in a good solid launch. That heated up the tires (and layed some big black marks). On the next run, I gave it 50% for 1/2 second or so, then ramped it up to about 75% throttle and promptly blew the right rear cap. The tires were crazy hot and gummy. That is what blew it out.

At any rate, I have a spare pair of caps. Plus I am ordering 4 more.

I have been learning quite a bit about this car. Once I get the body modded, it will be ready for testing at a better strip.


Matt did some more testing today:

I went out and did some more testing. I decided to run the car on 4S and do some bashing around with it. What I found is interesting.

First of all, the car accellerates with very similar characteristics on 4S as 12S. That is, the traction never changed even though the voltage did. The car still accellerated at a peak of over 2Gs and an average of 1.5 to 1.8 Gs throughout the run. Also, the car handled the power in a very similar manor to running 12S. Therefore, I can safely assume that 12S is not too much for the chassis to handle. On 12S, the power system draws over 3800 watts on 12S and 1000 watts on 4S.

Now for some more numbers;

The car wound out at an indicated 57mph on 4S. That is probably closer to 60mph because I have a slight fudge factor of about 3% to 4% to allow for wheel spin. So, that 57mph is a very conservative number. I was quite surprised. I thought it wouldn't break 40mph with the motor KV and gearing I have on such a low S count. Very encouraging! Tomorrow I will do some more testing on 6S2P to see how the car does. What I am trying to do with this is get a better baseline on what the chassis is doing without having 4.5HP to deal with. In case you are wondering, driving a super powerful car is not a matter of simply having good throttle control with your trigger finger. It is extremely hard to hang onto that much power. AJlovering will have this same problem. Of course, too much power is a fun problem to have!

Well, I think that is about it for now.


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