Information on this blog is raw and sometimes unverified reporting straight from the road by teams. The event will issue a media release for any events requiring an official notification.

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Tuesday, September 20, 2005

Leeming Sungroper: Tuesday 20th: track testing, track training.

Morning. Breakfast. Weetbix. Check email. Onno, from the WSC website, lets me know that he's putting my email missives up on the web:


At the appointed 8am gathering time, we have far less students than we did at the same time yesterday -- John knew that they would be full of energy and stay up late the first night or two, and now they have evidently burned through that initial energy burst. We get a couple of radio calls from other rooms, letting us know they'll be a couple of minutes late.

We gather, and the plan is announced. Some people go shopping for food, some people go shopping for electronics, some people go to the track. I, as usual, am with the track group.

I replace the non-conducting wire in the cable leading to our go-switch-and-speed-knob panel. This does not fix the problem. Dag-nabit.

Andrew turns up, and plays around with his voltage-and-alarms board. He wants to glue temperature sensors (the rather technically marvellous LM35's) to the batteries, but there's no suitable glue. So it goes on the shopping list.

More teams continue to arrive at Hidden Valley through the day, including Kormilda, Southern Taiwan and Annersley.

We hook the array up to the car, to push some photons into the battery. Telemetry shows that we're pushing in 0 Amps, which doesn't sound like a good number. We figure that there must be a problem with the current shunts. (In this modern world, it's much easier to measure voltage than current. So when we want to measure a current, we put a very very small resistance in the wire, and measure the voltage drop across it. We call it a "shunt" for historical reasons totally unrelated to the way they work today.) We pull out the centre battery string and poke around at the shunts, and eventually become convinced of their goodness.

We spread our search, and eventually figure out that the trackers (the four magic boxes that optimally accept power from the solar array, and optimally push that power out into our batteries), are seeing the array just fine, and are seeing the batteries just fine, but are failing to push any power from A to B. Between us, we're sure that the trackers worked back in Perth, and between us we're sure that none of us have rearranged any of their configuration switches. It's lunch time, so rather than getting the rest of the team to deliver lunch to us, we elect to return to Alatai and talk about it.

Lunch is toasted cheese sandwiches, also featuring sliced tomato and sliced meat of your choice. A few students burn their first efforts, by turning the frying pan up too hot.

We make some phone calls. Several back to key people in Perth, to check data sheets for us, to fish replacement parts out of Sungroper 1, to generally hedge our bets. And one to Stuart at AERL, the manufacturer, to ask about the problem. We describe the current state of the switches on the trackers. They've each got an OFF switch, which is in the ON position. Oh yes, says Stuart, if the OFF switch is in the ON position, then they're off, and they won't pump any power.

Back to Hidden Valley. As we drive in at about 70km/h, parallel to part of the race track, we get passed by a solar car. In the pit, we flip the OFF switches to the OFF position, and power up again. The car comes up smoothly, and the trackers pump power in just the way that they are supposed to. Applause.

We still have no idea how the OFF switches got to the ON position. An Aurora team member wanders by and suggests it was the switch fairies. Apparently Aurora have had some experiences with switch fairies in the past.

Steve and crew work on aligning the steering. Andrew and I work on bringing the Extra Sensor board up. It resolutely refuses to cooperate. Even though everything on it looks perfect, its little brain gives no sign of life. Luckily, after our earlier experience with the trackers, we've asked our friends in Perth to ship some key Sungroper 1 boards to us, including the original Extra Sensor board. They will arrive tomorrow. We'll drop the known working board in and either trouble-shoot some more, or just write off the new board, and replace it after the race.

This leads Andrew and I to the realisation that there will be a fair amount of work back in Perth getting the original Sungroper back to near-original condition. And I figure it'll be a little while after the race before we have the enthusiasm for that.

We roll the car out, and do some testing. We haven't driven yet on the newly fixed brakes, nor have we seriously driven on the present motor.

I drive first, on the basis that I'm the most technically experienced driver. I do a few low-speed bunny-hops in the pit lane, as a means of testing the brakes. Then it's out on the track for a lap, hotly pursued by a follow car. There are one or two other cars on the track, so we have a student up on on the viewing platform calling some perspective to us, so as we don't get in anyone's way. I take the car for a bit of a flog. The steering is a bit different from Sungroper 1, as it's 3 turns lock-to-lock, as opposed to Sungroper 1's 0.9 turns, but otherwise it's a very similar experience. Leeming Sungroper presently has an identical motor and controller to Sungroper 1, is of very similar geometry, and identical electronics, except for the bits we haven't finished yet.

I return to the pit and pronounce it good. Steve Morgan goes out for a couple of laps, partly to check the car for mechanical soundness, and partly because since he's put so much time into this car, he's damn well going to have a bit of a play.

Then, with sufficient happiness as to the state of the car, we put students in. We have three of our four drivers here, and they each get some laps. We get some idea of the car's present efficiency, too: at 9 Amps (a touch over the amount we can sustainably spend during the race) it goes at about 37 km/h. This is not enough to finish the race without trailering. So we need some efficiency improvements in the days ahead.

Nevertheless, the day is a success: we've got some mechanical and electrical stuff sorted, and we've got some driver practice in. Another team has arrived at the hotel: Apollo Solar, a Japanese team. We return to the Alatai. Dinner is curry (your choice of chicken or beef), and rice, with a piquant smoky flavour caused by the fact that the bottom couple of centimetres worth of the rice is burned black. Radio chatter is quieter this evening.

More tomorrow.

-- Doug Burbidge