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.

X3 body

X3 Update

Its been a while since I updated. Here is the status of the X3 so far. Everything is installed. The motor mount looks and works well. My father made the prototype mount for the Neu 2215/3Y. You can see the gearing looks very radical. This is because the low KV of the motor. Its only 480 Kv. So I need a large ratio to get as close to a final ratio of 1:1 as I can. Right now it is a 32 pitch 64 tooth pinion and a 36 tooth spur.

I've done a couple low speed passes on the street in front of my house and the only problem I see is that the pinion gear is not locking into place like it should with the setscrew. It comes loose after only a few passes. I removed the pinion and I noticed that the metal on the shaft of the motor where the setscrew would tighten down is dented. I think the steel on the motor shaft is too soft. It isn't hardened steel. If this is the case I will need to take it back to Neu to get a hardened steel shaft. This will make sure the pinion gear doesn't come loose. But this will also set back my testing schedule a couple weeks. I am going to file down the flat in the motor shaft a little more to see if I can fix the problem.

I made a quick video of the X3 doing some low speed testing in front of my house. The X3 sounds loud. I didn't expect it to be that loud. I am using stainless steel gears after all. I apologize for the angle of the video. I got a new camera and it wasn't setup to record properly.