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Rotary Racer - Car Performance
Goodwood Heat 2009-07-12
Results
This was the first race with RR8. The car had very little testing prior to the race and we had planned to make this a testing day. The car had other ideas though and we managed to come in second place!
Car Computer Log
This shows the main items measured by the Rotary Racers car computer. They are:
| Item | Description |
|---|---|
| Throttle | The position of the twist grip throttle from 0 to 100% |
| MotorCtl | The motor power output setting. The Car computer sets the motor power based on the drivers throttle position, the speed of the car and the current being used. There is a software algorithm to implement this "drive by wire" system. The Car computer drives the PWM (Pulse Width Modulation) Motor Speed controller with a duty cycle proportional to this value. 0 - 100% |
| Speed | The speed of the car in Km/H calculated from the magnetic read switch pulse generator by the Car Computer. |
| Voltage | The batteries voltage under load. |
| Current | The current being taken from the batteries. |
| Charge0 | The charge left in the battery pack 0. This is calculated by the car computer using an algorithm that has been honed to match the battery discharge curves for the Yuasa batteries. It currently bases its results on the current being used from the battery. |
| Charge1 | The charge left in the battery pack 1. This is calculated by the car computer using an algorithm that has been honed to match the battery discharge curves for the Yuasa batteries. It currently bases its results on the current being used from the battery. |
| BatPack | The battery pack in use (0 or 1). We have changed the driver with each battery pack change. |
| Temp | The Temperature of the motors casing in degrees C. |
The graphs show the overall data, the actual ASCII data log files are also available, from the links below, for detailed analysis.
Practice Laps Data
Battery Voltages
These are the battery voltages measured with a multimeter at the end of each change. The readings were taken as soon as possible after the batteries were taken out of the cae and placed back in the battery area.
| Battery Pack | BatA | BatB |
|---|---|---|
| 0 (RR7,RR8) | 12.30 | 12.38 |
| 1 (RR9, RR10) | 12.37 | 12.36 |
| 0 | 12.00 | 12.07 |
| 1 | 12.09 | 12.08 |
| 0 | 11.66 | 11.70 |
| 1 | 11.70 | 11.77 |
Notes
- The Car was RR8a. This was the first race for the new car. Due to time limitations, it had next to no testing and the paint was still wet !
- After practice lap testing with a 17:49 (2.88) ratio, in the race we used a 18:49 (2.72) ratio on the chain drive. We also added a small fairing in front of the driver.
- The Goodwood circuit is 3.862Km long and is fairly flat with sweeping corners. There was a quite a wind on the day (30Km/H ?).
- The Car Computers "Average Current" setting was at first 23.00 Amps, the Control Speed was 33 Km/Hour by accident. The current setting and Control Speed parameters were changed during the race to 25/52 effectively turning of the current limit as the car was averaging 25 Amps without it. We could have geared lower. We reduced the current setting later in the race when our motor was overheating. The software was car14.
- Drivers were: Gareth Barnaby, Dan Isles, Dan Dando, Tom Alington, Ben Millar, James Alington.
- The drivers behaved and drove excellently again, especially as this was a new car. The pit stops were a bit long as we had had no practice at all with the new car and lap time could be improved. But, we had started this race with the idea of just testing the car and getting to know it and fix any issues we had on the day.
- The car ran very well for its first outing and completed the race. Although we had started the race as a testing day, the car was going so well the compitition urge took over after the first drivers stint and pitstop :)
- The CarComputer and MotorSpeed controller worked very well although the telemetry link cut out for a few minuties during the race for some reason.
- The main problem we had on the day was that the main motor cooling fan jammed. This was noticed on the telemetry logs first as the motor temperature rose up to 70 degrees. (In actual fact the drivers did see the warning flashes on the dashboard but did not mention it ...). Luckly the computer raised the speed of the seconday fan and this managed to keep the temperature at 70 degrees. Gareth managed to un-jamm the main fan during a pitstop and it ran for the center part of the race, although with quite a clattering ! The motor cooled down to about 50 degrees after this. The jamming was probably caused by the fan comming into contact with its mounting plates for some reason. This occurred half way through the first drivers stint looking at the temperature log. Need to sort this out.
- The new isolation switch had broken at the end of the race, possibly caused by being hit. It was quite a flimsy switch compared with the one on the old car ...
- Seating was a bit more difficult to arrange now that the car can accomondate larger drivers. We had a belt, neck cushion and foam pad which worked, but we need to look at this. The seat itself ripped later in the race so probably needs a bit of strengthening at its top.
- Pit changes were a bit sloppy (compared to our normally high standard). We did'nt have any practice with the new car due to spending the time getting the car finished.
- The current average over the race was 25.4 Amps. The charge calculations stated we had 3% and 1.1% left in the battery pairs. The terminal voltage was about 10.5 volts per battery under load. Off load they were about 11.7 Volts. We had taken the full amount of battery power we could based on limiting to 10.5 volts to reduce battery damage. There was actually a little bit left in battery pack 0 otherwise the batterys were very well matched druing this race.
- The new Pit Stop warning light and message worked well, there were no missed pit stops.
- The average speed was 47Km/H and the peak 64.8Km/H (40.5 MPH). The fastest drivers were lapping at about 4:20, this is about 7% faster than at the Corporate challenge with the old car and it was more windy. This equates to about 9% improvement in speed over the old car which would have come from about a 25% improvement in aerodynamic drag over RR7e. This matched the VWT testing quite well.
- An excellent result for the new car on its first race.