Rayce Day 6: The Little Solar Car that Could

G’day world,

This is Ryan, currently distracted from operating telemetry in the chase car to write a blog post.  This is my first day operating telemetry from the chase vehicle, and unfortunately also the last day too.  Impulse is currently in the final stretch driving towards Port Agusta to hit the end of timing checkpoint, and with the weather that we’re getting, the race strategy team has decided that we want to drain our battery pack to log as many solar kilometers as possible, and then trailer to the finish line from there.  We drove 25-40kph earlier in the day but as we squeeze out the last of the charge now this means we’re averaging about 11 Kph on the Stuart highway.

For a small solar car, every hill is a challenge.  By hill, I actually mean a slight 1% incline.  Every incline we see makes Impulse and telemetry shudder in horror, because we never know if that hill will be the one to drain the batteries so much that the car will shut off.  The chase car was basically biting our nails at every hill, while watching our energy consumption jump from 8W / Kph to 24 W / Kph (I’m not actually sure what those units mean, but they seem to be tied to efficiency) when we started going uphill.  Our instruction to the drive is “Speed up by 1kph every 3 seconds, until you hear low voltage warning noises, in which case slow down by 1kph per 3 seconds until the warning noise goes away”.  It was the slowest yet most nerve-wrecking race I have ever seen.

On a side note, I added a rudimentary web dashboard to telemetry this morning sometime between 6am-8am (while trailering our car from the caravan park to the checkpoint) so that we can see numbers and some power usage statistics. (Eg. Watts used per Kph, whatever that means)

So I then connected all of my devices to a mobile hotspot on my phone, and I can now see telemetry from my iPod while I walk around outside.

Kudos to Devan Lai for making the telemetry code clean and readable so that adding this in was a piece of cake.

So far I have been in most cars in the caravan, and here’s what each of them are like:

Recon: Unanimously voted as the least stressful car in the pack.  Recon is generally the frontmost car in the caravan, and drives far in front of the pack to scout out the environment far off in the distance, book caravan parks before the pack arrives, and also take pictures as the car drives by.  Because recon can be anywhere, recon is also generally in charge of gathering supplies.  Its just nice going ahead of the solar car and finding a nice location to take pictures and videos.

Scout: This car is a part of the caravan and drives about a kilometer in front of the lead vehicle to spot for hazards and oncoming traffic.  When the situation arises, if Impulse needs to pull of scout also drives forward to find a suitable location for the caravan to pull off.  Since these situations don’t happen that often, the scout car is generally pretty uneventful.

Lead: The leader of the caravan.  Lead tries to maintain a 300 m distance in front of Impulse when driving (which is sometimes harder than it sounds, since you’re looking into your mirror more than the road in front of you), and with the help of chase and the other support vehicles decide where to go.  Lead is also in charge of talking to other teams on CB when we want to pass them, but that doesn’t happen all too often.

Chase: The centerpiece of the caravan, and the most important support vehicle of them all.  Chase runs telemetry with Impulse, crunches numbers into the race strategy, communicates with the Impulse driver, and keeps the observer entertained.  Its been voted as the most stressful vehicle of them all, but I think its the most fun.

5PM update:

The car has gone from excessive low voltage warning beeps to actually shutting off.  We’ve made good progress today and we’re going to trailer halfway to Port Agusta tonight and hopefully drive a little tomorrow, finishing in Adelaide.