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Rotary Racer - Car Performance
Silverstone 2011-05-01
Results
This
was the 2011 Corporate Challenge and a great 3rd place result. The car
was RR8g. Since the final the car had been modified to take the new
smaller batteries, the driver side flaps had been cutdown and screwed
into place and the rear of the car had been extended and streamlined to
take advantage of the new 2.8 meter car length.
The software had been changed to match the new batteries and a simpler laptop display added to allow easier pupil operation.
Althoug we had performed tests with the batteries over the Winter, this
was the first race with them. So we planned to race with around the
expected average current for the first session and pull the car in when
the batteries looked like they were finished and based on that alter
the average current for the rest of the race.
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. |
| Charge2 |
The charge left in the battery pack 2. 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, 1 or 2), the turbo button (4) and the Pitstop
warning (8) . We generally change the battery pack with each driver
change. |
| Temp |
The Temperature of the motors casing in degrees C. |
| GPS |
GPS position, speed and time together with lap position information |
| Misc |
Other items describing the operation of the control system |
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
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Notes
- The
Car was RR8g. This was the cars eleventh race. The car had been
modified to take the new smaller batteries, the driver side flaps had
been cutdown and screwed into place and the rear of the car had been
extended and streamlined to take advantage of the new 2.8 meter car
length. The batteries were kept in insulated and warmed battery boxes.
- We used a 18:49 gear ratio after testing during practice sessions.
- The
Silversone circuit is 2.637Km long and is fairly flat with sweeping
corners. There was quite a wind on the day (35Km/H ?) and it was into
wind on the long uphill pit straight.
- The
software was car21. The Car electronics worked well, but telemetry
range was severely limited within the grandstand. This showed up a
fault with setting the current limit that could cause the computer to
watchdog reset if a communications packet was only half recieved. This
led to loss of last lap average current data sometimes.
- The
battery charge calculations need to be revised now we have actual race
data. The Voltage based measurement was particularly well off.
- The new laptop display worked well, but there could be improvements. Some were noted on the day.
- The Car Computers "Average Current" setting was 16.00
Amps, the Control Speed was 44 Km/Hour, this was tweaked during the
race based on actual average lap current keeping it to around 18Amps.
- Drivers
were: Gareth Barnaby, Dan Dando, Tom Allington and Ben Millar. The
drivers drove excellently, went fast and kept out of trouble. Ben
certainly took to the bulls horns having full throttle for most of his
session aided and abetted by Dan increasing the power during a dice
with Simple Trug :). The
drivers chose to drive with 4 drivers although we only needed three on
the day. Pit
stops
were reasonably good but could do with quite a bit more practice.
Average pitstop time was: 1.48 minutes compared with 1.06 minutes at
Goodwood last June.
- The motors temperature kept below 42 degrees, the reduced average current has reduced this.
- The
batteries performance matched our winter battery tests quite well and
worked well. They were well matched. The voltage curves are quite flat
and drop off steeply when nearing 0% charge.
- We used the first two sets of batteries to their full coming in
when battery voltage levels indicated. This left quite a lot in reserve
for the last set of batteries. We used extra current during this stage
but still had about 15% of this batteries power in reserve at the end
of the race.
- An excellent first race with the new batteries and a great 3rd place result.
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