After doing some high speed runs. The motor endbell has slid off.
This post is a week late since I've been pretty busy lately. But I wasn't able to get any faster than 83mph. I made some changes since the last testing session. I removed all the data logging equipment, I modified the body and I removed the heavy stainless steel gear and replaced it with a lightweight delrin gear.
After doing the last pass of the test session, I noticed the power of the motor decreasing. I removed the body and I took a look at the motor and I noticed the end of the can was sliding off. It came loose during the runs. You can see this in the second picture of the motor. It has come off about 5mm from where it should be. Neu Motors has addressed this problem with their newer motors and has secured the endbell with screws like the motor below (the pic is a Neu 1515 but I will need this on my 2215):
I am going to have to send the motor back to Neu to get it repaired. I think this is the problem with not being able to get a higher speed. I should be able to reach at least 90 mph on 8s.
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.
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.
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.
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.
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.
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.
Well, if you guys have been following my progress you have seen that I have been having some bad luck with my car. I have been disappointed with myself that I haven't reached the speeds that I wanted. The heavy motor in the suspension system doesn't allow the shocks to compensate fast enough for the rough surface. I believe that is why my wheels would keep blowing. Too much sprung weight. I have been thinking of a new car to use. I have decided on an OFNA Ultra GTP. It is a 4wd shaft drive 1/8 scale gas buggy. I am going to convert it to fit the Neu 2215. This car is much heavier, but much beefier. It should be able to handle the 7hp (5000 Watt) Neu 2215. I already have the car and I started to layout the electronics. I am calling it "X3". I have designed the motor mount and it is being fabricated now.
"X3" This is the initial layout of the components. It is messy because its not permanent. I want to be able to move the electronics around until I find the best placement.
"X3"
"X2" on top, "X3" on the bottom
"X2" is on the back burner...for now.
"X2" in its last testing interation
I am not completely abandoning the "X2" design. I know it has a lot of potential but for now it requires too much tweaking to attain the speeds I would like in the time frame given. I am putting it on the back burner for now and I will return to it in the future.
What the motor should look like
After doing some high speed runs. The motor endbell has slid off.
