X3 Testing today - 79 mph

stainless steel pinion gear teeth wearing out

Today went well. Since my last testing day I had changed the suspension to get the chassis so the front was lower than the rear to try to resist blow over. I also attached a splitter to the front end to help create down force. This did help as I was able to go faster without blow over. But, I was able to see blow over about to happen at around 79mph. I had to back off the throttle to make sure the X3 didn't take flight. It looks as though the X3 still wants to blow over even with the front splitter and the suspension changes. I want to modify the front end some more to apply more down force and change the rear end to reduce down force and drag.

The data recorder didn't work. It was unfortunate that I wasn't able to get data from my Eagle Tree recorder.

I have some aerodynamic changes to make to keep the X3 from blowing over and I will be out testing again.

Blow over in slow motion

X3 Testing today

The weather was much better today and I got a chance to test. Max speed today was 73mph at about half throttle. After the 73mph pass I made another pass with more throttle than the previous runs. At about 75mph the X3 blew over.

Video of 73 mph pass

Data from 73mph pass


Video of blow over pass at about 75mph

Data from blow over pass

Damage to the X3 from the blow over

The rear springs are much too soft for the extra weight of the massive motor and batteries. Stiffer springs are necessary to maintain a good rear ride height. Under acceleration the back end would squat and the positive angle of the chassis would direct all the airflow underneath the car. This caused lift and I had a blow over. I tried to minimize the up-travel of the rear shocks with spacers, but then the rear shocks would rest on the spacers and that rendered the suspension useless since there was no upward suspension travel. I also need to decrease downforce on the rear of the car. I need to trim or get rid of the rear wing. As far as I can tell the damage to the X3 is superficial. The body and front right wheel seemed to absorb most of the impact.

Overall, I am very happy with how testing went today (except for the blow over). The X3 felt very stable and very easy to drive. Acceleration was excellent. I didn't push the X3 to its limits because the spur and pinion gears are wearing themselves out very fast. I need to get a new set after the next couple runs.

I will make a couple of changes and I will be back testing soon.

Rained out

Well, today was rained out, but it looks like the weather should be better tomorrow. I'm hoping we'll have nice weather to get a go at some good speed runs. In the meantime, I have taken some pics of the current iteration of the X3:














Some changes since the last pictures I posted are that I added some Lexan side body supports to help stabilize the body at high speeds. I installed the gyro up front in the foam bumper. I also cut the rear section out of the body to help any air flow through and out the back. I also installed large vertical stabilizers to keep the X3 from fishtailing at high speeds.

The X3 is ready to go for tomorrow.

Update

Quick update. I have everything installed and the body is mounted. The "X3" is ready to go for testing this Saturday weather permitting. I will be running:

Batteries: Thunder Power 3300mah 8s (4s+4s)
Gearing: 32p gears-64 tooth pinion, 36 tooth spur (chart below says 32).
Futaba GY401 Gyro installed
ESC: Castle Creations HV-110

This is a quick video of the X3 doing some slow passes in the street.



Here is the data from the Eagle Tree during that run:

Second run (more aggresive on the throttle than first run):
The biggest amp draw on that run was about 90 amps at 50% throttle. I was able to hit about 50mph without a sweat.

The X3 felt good and stable. The 4wd drive is a definite bonus over the FWD of the X2. The acceleration is explosive and I can still break the tires loose even with this car geared at 64 tooth pinion and a 36 tooth spur! The NEU 2215/3Y is a monster. My plan is to get around 100mph on 8s:

The only thing I am worrying about is the pinion gear keeping a tight fit on the motor shaft. The pinion has already rotated about the motor shaft and the set screw is no longer on the flat part of the motor shaft, but it has not come loose with all of the driving I have done so far.

I am looking forward to posting some good speeds. Its about time to make some serious progress with all of the power I have available. The X3 can deliver all this power to the ground.