This is a humorously-titled reflection after ASC 2018, aimed at figuring out why our car seemingly does worse compared to the competition. Hopefully we can identify areas of improvement, knowing that these are obtainable baselines that other teams are able to meet.

I. Range

According to App State's blog post from Day 3, they indicate that they traveled 210 miles, with roughly 40% SOC left.

Today has finally been proof that our car is capable of much more than we’ve been getting out of it so far. We have not had any major issues on any fronts. It’s now 2 o’clock and we have already traveled 210 miles but here’s the best part: we still have ~40% state of charge left, and the sun was generous enough to show itself today. Not only have we already broken our record for distance traveled on a single charge, we aren’t even close to being out of batteries. Team Sunergy is tearing through Wyoming -- we’re now only a few miles away from Casper, WY where the next checkpoint awaits. Rough estimates gauge that we could go up to 300 miles in conditions like these, even more with better sun & roads.

210 miles / total = (100% - 40%)

therefore, we have that

total = 210 miles / 60%
      = 350 miles

Let's use the 300 mile estimate that they give to be conservative.

For reference, our best day had us travel almost 390 km, which is a total of 242 miles.

300 miles - 242 miles = 58 miles

Where are the other 58 miles going?

In order to be competitive with teams that are racing at WSC, we drastically need to improve our energy consumption.

WSC = 3020 km 
WSC duration = 6 days

3020 km / 6 days = 503.333333 km / day

If we assume we were able to maintain 390 km every day, we would still be short 113 km of range. Either our aero is really bad, or there are losses being incurred somewhere (say via damaged tyres, friction of tires rubbing against fairings, etc.) that we didn't account for.

Note: We were targeting a cruise speed of 60 km/h (37 mph), but App State averaged a minimum of 42 mph assuming they started at 9 am and travelled 210 miles by 2 pm. We found that going 6 mph faster significantly increased our current draw so it would be unlikely that we would make 242 miles with 40+ mph.

II. Array

The best output we ever got from our array was -7.2 A (Note that this was measured by our BMS Current Sense, so this was 7.2 A going into the battery. The DC-DC probably drew 0.5 - 1 A, and was fed directly from the array in the PJB.)

Onda Solare was able to go the entire race (carrying 4 passengers for a majority of the time) without resorting to external charging. They also had a slightly larger pack than ours,

I think Minnesota would have been able to as well (carrying 2 passengers), had they not encountered their High V short to their chassis.

III. Motors

According to App State's blog from Day 5,

This morning we face the steepest hill climb of the entire race, just outside of Lander. We will be climbing up to an altitude of 8500, gaining over 3200 feet of elevation in the process before beginning our descent back down. We had no trouble getting up the hill with our twin Mitsuba motors handling the steep grades with ease.

App State uses two Mitsuba 2096 D-III motors (with the default Mitsuba motor controllers), which have a 95%+ efficiency

Our NGM SC-M150 motors struggled a bit climbing the hill on our hill-start.

IV. Motor Controllers

We were running into a lot of issues with our Motor Controllers overheating. Supposedly a lot of teams either run with the WaveSculptor 20 setup that we have, or the WaveSculptor 22. This resulted in us having to frequently stop and allow them to cool down.

V. Regen & Brakes

I was talking to App State after the stage stop on Day 6, and their driver was saying how he was regen-braking the whole way down the hill.

To be fair, I think regen braking helps more in keeping your speed low so that you don't incur the aerodynamic losses due to drag when zipping down hills. That way, you can maintain a speed that is optimal for your aerobody, and retain the excess energy in your pack with minimal losses. Our drivers tried their best to avoid using the mechanical brake.

We ran the entire race without any regen braking. 🎤

VI. Weight

I think the official published stats for the Cruiser cars speak for themselves

Team	Weight (kg)
App State	362
Bologna	300
Minnesota	380
Waterloo	475
PrISUm	520

Considering PrISUm didn't qualify, this really does make you think 🤔

I don't think we need to go full-on carbon fiber like Bologna (nor do we have the expertise), but we can definitely identify areas where there are potential weight-savings.

We had initially projected 506.9 kg as the upper bound our weight in our weight budget (which included 2 drivers and their ballast). Our weight without the dropout and fairings (probably 10-20 kg in total) was 632.5 kg.

Even if we ignore the dropout and fairings, this a pretty big difference (~20%). It would be good to understand where the additional weight is coming from, and what the actual breakdown is, so we know what to optimize.

632.5 kg - 506.87 kg = 125.63 kg

There might be value in revisiting the original weight budget and comparing to see whether we were off in our projections (and if so, where?), or if there were items that were missed.

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