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Rotary Racer - Car Performance
Goodwood Corporate Challenge 2009-04-26
Results
The corporate challenge and we came fourth and won the "Best Engineered Car" award
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 we placed back in the battery area.
| Battery Pack | BatA | BatB |
|---|---|---|
| 0 | 12.45 | 12.45 |
| 1 | 12.42 | 12.42 |
| 0 | 12.14 | 12.14 |
| 1 | 12.16 | 12.17 |
| 0 | 11.75 | 11.79 |
| 1 | 11.84 | 11.85 |
Notes
- The Car was RR7e. This had been modified to the new 2009 rules with a lower screen and battery box. We also had to move the steering back 12cm and increase the roll bar height to accomondate the growing drivers. We had also modified the rollbar supports and nose cone to hopefully improve aerodynamics a little.
- The Car Computers "Average Current" setting was 24.00 Amps, the Control Speed was 35 Km/Hour. The current setting and Control Speed parameters were changed during the race to increase speed matching the battery charge state. The software was car14.
- After practice lap testing with a 20:55 (2.75) ratio, in the race we used a 20:57 (2.85) ratio on the chain drive.
- The Goodwood circuit is 3.862Km long and is fairly flat with sweeping corners. There was a slight wind on the day (20Km/H ?).
- Drivers were: Gareth Barnaby, Dan Isles, Tom Alington, Ben Millar, James Alington, Dan Dando .
- The CarComputer and MotorSpeed controller worked very well although there was a glitch causing the average current calculations to go adrift. We need to look at this. Otherwise it did its job and managed our battery usage excellently.
- The telemetry system worked well as before. We still have not done any real testing with the telemetry system or really thought about how best to use it yet. However, it proved its worth. We now need to think about what we want from it and develop the software to improve information available.
- The Motor cooling system worked fine. The temperature graph shows the motor slowly heating up through the race and reaching a top temperature of about 38 degrees C. The Car computer would have been running the fans at 60%. We could run the motor slightly cooler by modifying the Car Computers fan control algorithm to increase cooling fan speed a bit.
- The drivers behaved and drove excellently again.
- Pit changes were a bit sloppy (compared to our normally high standard). We need to tighten up the pulling in and out of our slot in the pit lane and practice battery changes.
- Dan had a spectacular spin at 50 Km/H in the later stages of the race due to being cut up by another car. The car did not roll at all which was good. The motor current surged to 66Amps as the wheel was pushed into reverse. The Motor speed controller survived ... Luckly Dan got moving again and finished the race to keep our 4th place.
- The average over the race was 24.2 Amps. The charge calculations stated we had 4% and 1.5% left in the battery pairs. The terminal voltage was about 10.5 volts per battery. 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 2. The batterys where much better matched during this race, so the charging method worked well.
- The new Pit Stop warning light and message worked well, there were no missed pit stops.
- The average speed was 46.34Km/H and the peak 59.4Km/H. We managed about 115.2 miles which bettered our last goodwood race by 2.6 miles which was good. Without the spin we would probably made 117.6 miles which is an improvement of about 3.8%.
- Another excellent race with a good result.