Rotary Racer Car Data

Rotary Racer - Car Performance

Dunsfold 2010-09-26

Results

A great and exciting race for us. We again used the old, half dead batteries with the one whose cell collapsed in the last race replaced by a better one lent to us by TPM (thanks for that). We knew still wouldn't have much energy to race but thought we could probably average about 17.5 amps. Dunsfold is a tight track and there were quite a few entrants so it would be relatively slow, drivers were also re-gaining confidence. We decided to go with 6 drivers and a single battery change to try this method with the colder day.

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
Misc
Other itmes 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

Car Data Log

The full race

Car Data Log

Battery Pack BatA BatB
0 (RR7,TPM's)

1 (RR9, RR10)

Notes

  • The Car was RR8f. This was the cars ninth race. The only changes from the previous race were different rear tyres and some small defectors near the mirrors.
  • The car was running with a 18:49 (2.72) ratio on the chain drive, with the smaller wheels.
  • The Dunsfold circuit is 1.255Km long and has a slight hills with three tightish corners. It is a bit bumpy in places. There was a reasonable wind on the day (30Km/H ?).
  • The software was car19 which included average speed computation and GPS data and lap timing measurements. The Car electronics worked well.
  • Dawn and Steff, some newer team members had a practice lap each ate the start and drove fine.
  • The drivers reported that the car felt fine drving, including in the wet conditions later in the race. The brakes worked well and were a bit smoother. The joystick steering may need moving forward again as the drivers are still growing ! The drivers we going reasonably steady and kepy well out of the way of the other cars leading to a safe race on the crowded track. The drivers were: Ben, Liam, Tom, Dan, Gareth and James. Pit-stops were excellent. We did get two black flags for passing cars in yellow flag conditions, but this was difficult to avoid with the large number of yellow flags and quite slow cars.
  • The car was fine in the rain. Very little water got into the car, including around the rear wheels and the electronics were dry. The drivers kept quite dry except for their visors. There was no sliding even in the wet conditions later in the race.
  • We started off near the front using around 17Amps and on the limit for the speed limit for this race. We then reduced the power levels to about 15 Amps but the large numbers of slowing up and brakes effecitively increased the average to about 15Amps. During Liams and Toms drives another battery cell colapsed, probably in RR7, you can see the 2Volt jumps in the voltage levels. As this is the last race for these batteries (we thought that a year ago :) ) we decided to just run them into the ground. The motor speed controller upped the power to keep our average speed relatively high while the battery was drained. We left Tom as for as long as we dared to allow us to have more energy for the second battery stint. We got about 40 Amp hours out of this set (probably mainly TPM's battery) at about 17.6 Amps.
  • The second batterys ran fine, no collapsed cells, but just did not have the energy being old. They produced about 33 Amp Hours at about 19 Amps. The higher average current was probably mainly due to the drivers braking for the Yellow flags after our earlier Black flag issues. With just a touch more energy or one less yellow flag slowing down we would have won.
  • We managed to average 18.5 Amps (70%of  normal), a little higher than the 17.5 Amps we were expecting.
  • This was an excellent race, with lots of action, yellow flags, black flags, being in 12th place and then climbing to first place only to lose that in the last lap by 4 seconds, but a second place for us !