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Rotary Racer - Car Performance
Goodwood 2010-06-20
Results
This
was the first F24 Greenpower event of the season for us with Rotary
Racer RR8d. The drivers decided to use 6 drivers in the race. With the
higher than expected speed limits set by Greenpower in the Coorporate
Challenge we decided to look at improving the aerodynamics of the car
to increase the cars efficiency so we could go for a Platinum mileage award.. We measured and experimented with
reducing the cars rolling resistance, but could only find a slight
improvement from this. Gareth and Dan measured the car and Gareth
entered a more accurate CAD model in Pro/Engineer. We then tried this
model in the VWT and played around with a few ideas. One idea was to
pull in the rear end more after Gareth had talks with Bloodhounds
aerodynamisist. The VWT indicated that the two best improvements would
give us about a 10% reduction in drag, equivelent to about a 5%
improvement in speed. The team implemented these relatively minor
changes to the car for this race. We had a plan
to try and achieve a platinum millage award at this race. It worked !
We went about 4.2% faster in slightly higher wind conditions and at
about the same current as we used in the CC a couple of monts ago. We
managed
to win the race and achieve 127.2 miles in 4 hours giving us our first
platinum 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), 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. |
GPS
|
GPS position, speed and time together with lap position information
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Misc
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Other itmes describing the operation of the control system
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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 revalively equally.
| Battery Pack |
BatA |
BatB |
| 0 (RR12,RR15) |
12.51 |
12.51 |
| 1 (RR13, RR14) |
12.43 |
12.43 |
| 0 |
12.17 |
12.20 |
| 1 |
12.14 |
12.13 |
| 0 |
11.80
|
11.82 |
| 1 |
11.86
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11.85
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Notes
- The
Car was RR8d. This was the cars sixth race. Aerodynamic modifications
to the rear end, screen, and driver cockpit sides had been done. A
second hand GPS module had been added and the software updated to log
the information and record timing line crossings. The batteries were
kept in insulated and
warmed (about 42 degrees C) battery boxes.
- After practice with a 19:49 ratio, the car was going so well we
decided to experiment with a 20:49 (2.45) ratio on the chain drive
giving the ability for more speed with increased 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
software was car17 which included average speed computation and GPS data and lap timing measurements. The
Car electronics worked well and the software changes worked well. The
speed measurement was a bit variable and needs a look at. The current
control was bouncing up and down a bit because of this.
- The
Car Computers "Average Current" setting was at first 25.00 Amps, the
Control Speed was 48 Km/Hour, this was tweaked during the race to keep our race speed below the limits for this race.
- In general the new GPS timing system worked well giving us a
second set of lap timing figures to make sure we were near but under
the speed limits for this race. Unfortunately the GPS dropped out for
about 25% of the time. We suspect the aerial position, being close to
the steel rollbar, caused this. We will try moving the aerial. The GPS
lap position and timing system worked well, but the data was not stored
to the SDCARD. We need to add this.
- Drivers
were: Ben Millar, Liam
Towills, Dan Dando, Tom Allington, Gareth Barnaby and James Allington. The drivers drove excellently and the
drivers performance was well matched. Pit stops were good.
- The car ran very well and the software performed
well. The motors temperature was generally around 50 degrees but did go
up to 60 degrees. We could look at the motor cooling.
- The batteries performance was a little disapointing considering the warming. They may be degrading faster than expected.
- We had a excellent stable race, came first and achieved our goal of getting a Platinum mileage award :)
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