Rotary Racer Car Data

Rotary Racer - Car Performance

Goodwood 2010-10-17

Results

This was the 2010 National final and a great 3rd place result. The car was RR8f with the post roll modifications, smaller wheels and lower to the ground. We had also improved the behind the head fairing and had a new CNC produced roll-bar aerofoil. We did not have high expectations as we had not been able to race the car at speed after its major mods and re-tune it. Also our batteries, although good, were not the best (one pack 2 years old and the other a year old with about 4 races under there belt plus testing). The Greenpower new battery change and our new wheel costs precluded us from buying a new set of two for this final as we would have normally done.

During practice we tested with a 22:49 and a 19:49 ratio gearing. The results were not encouraging on the cars performance, but we gambled with the 22:49 to allow us to at least use every last once of energy from the batteries (especially if a cell failed as had happened in the previous two races with very old batteries). In actual fact during the race the cars performance was better than expected and we managed to be able to hold the race speed limit in the early stages. With heating we expected our batteries to be able to just about put out 26Amps on average for the race. We were using a touch over that and so had to power back a touch early on.

All was going very well and we were well up into second place with one last driver change to go when the throttle system failed. The Curse of having the "1" ! (Actually bad maintenance ...). Luckely this happened on the chicane and Ben managed to coast the car to a stop close to the track exit point saving the use of a recovery wagon (thanks to the marshal for pushing us in). The two cable holding bolts had come loose and the cable had pulled through (a bit of a maintainance failure and one more for the check list !). Unfortunately we could not get the cable back in due to the frayed end (should have soldered it ...). We had a spare button on the joystick intended to operate a solenoid in case of total electronics failure, so we connected this in place of the throttle potentiometer. Alas the switch didn't work (contacts dirty ??). Gareth had the idea to use the secondary car horn switch and so this was wired in instead (losing the lads designed, built and programmed "tunefull" car horn). We were off again, 19 or so minutes later, but had moved down to 4th place, behind SC07. James drove excelently using his left hand's thumb on the car horns button. With energy now in reserve, we took the car right up to the speed limit and managed to reclaim 3rd place (sorry SC07/Brian).
Suberb weather and a great fun race for us, although the throttle cable problem was disapointing, the podiums 3rd place snatched back after our problems was a great end to the day and season. It will be good to have the new style batteries after the issues with the old ones this year.

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.

Car Data Log

Practice Laps Data

good7prNUqYACar Data

Notes

  • The Car was RR8f. This was the cars tenth race. Aerodynamic modifications to the behind the roll-bar fairing and a new CNC produced roll-bar aerofoil had been implemented. The batteries were kept in insulated and warmed (about 50 degrees C) battery boxes.
  • The joystick had been moved forward 20mm to cater for the lengthening drivers ! We did not organise the foam packing and behind helmit foam for the shorter drivers before the race well though.
  • Because of the cars unknown performance after the wheel size change, we tested it with a 22:49 amd 21:49 ratio during practice. We decided to go with the 22:49 to allow us to use the full amount of energy from the batteries and  be able to continue well with any faulty cells even though it looked like the 21:49 might suit the car and conditions better.
  • The Goodwood circuit is 3.862Km long and is fairly flat with sweeping corners. There was a light wind on the day (10Km/H ?).
  • The software was car19. The Car electronics worked well with no issues.
  • The Car Computers "Average Current" setting was at first 25.00 Amps, the Control Speed was 51 Km/Hour, this was tweaked during the race to initially keep our race speed below the limits for this race and later to keep our average current low enough for the batteries we had.
  • Drivers were: Gareth Barnaby, Tom Allington, Dan Dando, Ben Millar and James Allington. The drivers drove excellently in the crowded conditions of the final, went fast and kept out of trouble. Pit stops were good.
  • The motors temperature kept below 50 degrees so the improved motor cooling probably worked but it was a colder day.
  • The new wheels we built are fine and are still perfectly true.
  • The batteries performance was ok for 4 race batteries but not as good as new considering the warming. We ended up averaging about 26 Amps for the race. At least no cells collapsed. Roll on the new batteries.
  • In the throttle graph you can see poor Jame's thumb getting crap in the later stages of the race :)
  • A little more maintenance/checking of things before races is called for although this is the first time we have been off the track in 3 years of racing.
  • The team worked well in handling the issue. There was no panic and the whole team pulled together and helped fix the car and get it back on the road.
  • Apart from the throttle cable issue, we had a excellent stable race and managed to come third.