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Rotary Racer - Car Performance
Dunsfold 2009-09-28
Results
This was the third race with RR8. We had an excelent race and managed to win the race, which was very suprisng considering our batteries condition, we averaged only 17.4 Amps !
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 car and placed back in the battery area. (the 2nd, 3nd and last readings were taken a bit later).
| Battery Pack | BatA | BatB |
|---|---|---|
| 0 (RR7,RR8) | 12.47 | 12.58 |
| 1 (RR9, RR10) | 12.50 | 12.51 |
| 0 | 12.28 | 12.32 |
| 1 | 12.18 | 12.19 |
| 0 | 11.94 | 11.89 |
| 1 | 12.10 | 12.12 |
Notes
- The Car was RR8b. This was the cars third race. No major modifications. The rollbar had a leading edge fitted, the seating had a better anti-submarining system and we had put back on the old continental tyres. We had warmed one of the battery packs and stored it in an insulated box that we had just finished.
- We had done some battery discharge tests on RR7/RR8 and had found that these batteries had lost 25% of the charge holding capability since the last race. As the other pack had been nearly identical and used in the same way we assumed that these were in the same condition. From this we determined that we could only expect to use 18 Amps on average through this race. A really low figure. So we intended this to be more of a driver training and fun day. We had a new driver, Liam, who had hist first drive.
- After practice with a 17:49 ratio, in the race we used a 16:49 (3.0625) ratio on the chain drive to assist in keeping our current low.
- The Dunsfold circuit is 0.78 miles long, is relatively flat and has quite tight corners. Due to the track length and lost of cars competing there was a large amount of passing to do and quite a few yellow flag incidents. There was very little wind on the day (8 Km/H ?).
- The Car Computers "Average Current" setting was at first 25.00 Amps, the Control Speed was 38 Km/Hour, this was soon reduced substantially through the race. The software was car15.
- Drivers were: Ben Millar, Gareth Barnaby, Liam, James Alington, Dan Dando, and Tom Alington,.
- The drivers drove excellently again, the drivers performance was well matched. Liam drove very well for hist first drive, especially on this tight, car infested circuit. The pit stops were good. We did get black flaged for overtaking in a yellow flag condition. Not sure where this actually happened as there were yellow flags all over the circuit. We were also brought in incorrectly once and sent out straight away.
- The car ran excellently, there were no problems during the race. The motors temperature kept below 36 degrees.
- The CarComputer and MotorSpeed controller worked very well with no issues on the day. The telemetry link worked over the whole of the circuit.
- The current average over the race was 17.4 Amps. The batteries were at about 10.8 Volts at the end of the race so we were very close with our estimate of 18 Amps. This was a very low figure, the batteries are shot. In a normal race we could expect to use about 25 Amps. In this race we used only 70% of the energy we would normally use and we still won ! The warmed RR7/RR8 (30 degrees) battery pack had about 8% more energy than the RR9/RR10 (20 degrees) battery pack proving the battery info and temperature tests again.
- The electronic speed control was used extensively during this race. We used a high current during the early stages, which earned us a fastest lap award and then cut it down for the rest of the race. Nearer the end of the race we lowered it even more to a point where we were only averaging 9 to 10 Amps so we could be sure of finishing while traveling at a reasonable speed. At 10 Amps we will still traveling at about 35 Km/hour. This was based on the seconday votage/current battery monitoring system which was suggesting that the battery capacity was slightly lower than we needed. We upped the power for the last two laps once we knew the end was in reach :) The telemetry and electronic speed management were instrumental in winning this race.
- The average speed was 41.4Km/H and the peak 58.32Km/H. The fastest drivers (where the power level was at full) were lapping at about 1:33.
- We managed 100.62 a bit more than with the old car on the same circuit last year.
- Another excellent result for the team and its new car.