Castle Combe – Sunday 27^th June

Race Report

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Technical View Point

Authors: - Bob Carter

F24+ Race

The F24+ Results: -

General

At this race meeting we used last year’s batteries, in order that that our new ones had plenty of time to recover from the race 5 days ago, and to save them for the final in October. This meant that our batteries were variable and unpredictable; making it a very interesting day’s racing!

Usage Statistics

The above graph shows the Amps drawn as Zebedee went round the circuit. The Drivers should be able to identify the uphill sections where high power is drawn, and the downhill sections where the current drops. Note the circuit is just under 1 mile, downhill for half of it and uphill for the other half.

Progress Chart – Speed, Volts and Laps

Brian’s chart is shown; Zebedee had to stop after 10 minutes with a flat battery – our worst of the day!

Initially the cars set off unlimited on power setting 5 to pull out a lead. (Note that with new batteries we can run throughout a F24+ race on 5 with ½ hour on 6) After a few laps the speed limit was brought down to 36mph, then lowered again at 20 minutes, essentially holding at 33 until it was clear we were losing volts at around 53 minutes. From here on we were on a holding pattern trying to keep the car going while we progressively slowed it. Note that at 60minutes the power setting was reduced, so the car slows more on uphill sections, but the battery volts fluctuate less. After 75 minutes the power was pulled right down and the car completed the last few laps at less than 20mph. We could have kept going at that speed for another 6 or 7 minutes.

Looking back at the data we could potentially have got another lap if we had run slower from the start; but of course at the time we had no way of knowing how the batteries would last and hence what speed to set.

F24 race
 

Time	Speed Limit
240 minutes	16 laps per 30 minutes Average speed 32mph

The F24+ Results: -

Pos.	Car	Laps
1st	Fireblade	103
2nd	Zebedee	102
3rd	Khale cc	101

Once again we set off with mystery batteries, with low expectations of the results this time.

Zebedee Progress Chart – Speed, Laps, Volts, Temperature: -

No high speed heroics in this race: it was about nursing the batteries home to the chequered flag. The “laps in 30 minutes” chart shows we were never near the limit, and slowing drastically at the end! After an unregulated couple of laps we controlled the car at 29mph, as this was taking a steady 25A. Unfortunately this was too much for the first set of batteries and after 1.5hrs they were showing signs of going flat. So the batteries were changed 20 minutes early, and the race continued; only for the 2^nd set to go flat just before the 3^rd hour. Faced with empty batteries, an hour still to run, and the surprising fact that we were 3 laps clear in the lead at this stage!!! We gradually slowed the car to 22mph and turned the power down until the batteries were utterly exhausted at 3.6hrs, at which time the first set were put back in. This kept us going for another 15 minutes until with a last desperate throw of the dice, the lowest voltage battery in the car was swapped with the highest voltage battery in the pits (a trick we’d played earlier with Brian). This allowed us to keep going at well over 20mph to the end of the race.

Brian Progress Chart/span> - Speed, Laps, Volts, Temperature: -

Brian, like Zebedee was speed controlled to have an average current draw of 25 amps. This was at a speed limit of 24mph. However Brian’s first set of batteries was really good and as 2 hrs approached the limit was increased a little. However, reality bit back with a vengeance in the form of a second set of batteries with very poor capacity; going flat after about 3hr 10mins. So the first set were put back in, but these were pretty empty and after 20 minutes, even running at only 18mph, the car had to pit again. This time we replaced the lowest voltage battery on the car with the highest voltage battery in the pits, then went out with a very low power setting (2) and low speed limit to creep round quite a lot more laps during the last half hour, coming in a respectable 9^th place in a field of 35.

Summary 

This was actually a very good race for the team. We were on the ball, calm, focused, and available when needed. The Bluetooth headsets works exceedingly well, letting us keep the drivers in the picture as the end game of eking out battery charge unfolded. Beth did a great job in race control; and the last 2 drivers, Zoe and Charlotte stayed calm as their cars died around them, nursing them home to quite outrageous success. Strangely this felt much more satisfying than the double 1-2 finish at Castle Coombe last weekend.

The battery charge delivered was as follows:

Zebedee

1st set       44Ah

2^nd set      42Ah

Brian 

1st set       57Ah

2^nd set      34Ah

I hope we’ll be able to identify Brian’s 1^st set for re-use.