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Pitstop practice
Rotary Racer - Car Performance
Corporate Challenge Goodwood 2010-04-25
Results
This was the Greenpower Corporate challenge event at Goodwood with Rotary Racer RR8. The drivers decided to use 6 drivers in the race entailing 5 pit stops rather than the minimum allowed of 2. We experimented with gearing the car slightly lower. We had an excellent race, and managed to come in third 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), the turbo button (2) and the Pitstop warning (4) . We generally change the battery pack with each driver 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 batteries are very well balanced and we used each pack equally.
| Battery Pack | BatA | BatB |
|---|---|---|
| 0 (RR12,RR15) | 12.37 | 12.36 |
| 1 (RR13, RR14) | 12.41 | 12.41 |
| 0 | 12.13 | 12.12 |
| 1 | 12.20 | 12.20 |
| 0 | 11.74 | 11.75 |
| 1 | 11.74 | 11.74 |
Notes
- The Car was RR8c. This was the cars fifth race. No major modifications had been done since the final. The minor changes included: painting the internal steelwork, replacing the wheel coverings, a motor change needed because of new rules (no cooling holes in the motor) and balancing the weight on the front wheels. We used the Schwalbe Durano tyres on the front and rear. The batteries were kept in insulated and warmed (about 35 degrees C) battery boxes. A new fishing pole based aerial for the telemetry was used.
- After practice with a 18:49 ratio, in the race we decided to experiment with a 19:49 (2.58) ratio on the chain drive giving more control range for the speed controller at the expense of a degree of efficiency.
- The Goodwood circuit is 3.862Km long and is fairly flat with sweeping corners. There was a reasonable wind on the day (25 Km/H ?).
- The Car Computers "Average Current" setting was at first 25.00 Amps, the Control Speed was 38 Km/Hour, this was tweaked during the race to keep our average current at about 26 Amps. The software was car16 which included average speed computation.
- There was a problem with the battery number sensor. Probably a dodgy connection after the rebuild. The data has been massarged to remove the error. This messed up the, current based, battery charge calculations leading to a few drivers worring about a charge level of 0% ! At the pits we used the voltage based charge calculations instead, these worked well.
- Drivers were: Ben Millar, Gareth Barnaby , Tom Allington, Dan Dando, Liam Towills, and James Allington. The drivers drove excellently and the drivers performance was well matched. Pit stops were good but slightly variable in time. A few minor issues and some practice is called for.
- The car ran very well and the software performed well. The motors temperature was generally around 50 degrees. This was about 9 degrees higher than at the final. This is probably due to the lack of cooling holes and the slightly increased current used. We could increase the fan speed a little or look at adding some fins.
- We had a excellent stable race and came third.