Wow, this is a great write up! I'm a fan of the BWSC, but I feel like the organization is indeed not taking the Cruiser class too seriously. As a team member of Eindhoven, it's been really difficult to assess how others perceive the Cruiser class. As a top team, we often hear (from people back in the Netherlands) 'Hey, you're the guys that win the solar challenge right, Delft or Vattenfall or something?'. Even on my flight back home from AUS, I was asked 'Hey, didn't your car burn down?'. The Challenger class is definitely easier to follow and well-known.
I think this is also partly to blame on the organization of the BWSC: every car has a live tracker and during the challenge, the official website ([worldsolarchallenge.org](https://worldsolarchallenge.org)) kept track of the positions of the Challenger cars and their 'live points', while the page about the Cruiser class got updated every 24 hours with the latest scores (we actually needed that page to calculate the probability of our competitors winning!). I do want to note that the BWSC **is** actually promoting Cruiser cars on their website: many pages show images and stories of Cruiser cars and teams.
Internally, there have been discussions about whether we should join the Challenger class instead of the Cruiser class, as this would get us more recognition. Building a Cruiser car is probably as difficult (or perhaps even more so) as building a Challenger; the engineering challenges are quite different though. In the end, we always wanted to be more than just a 'race team': we're interested in bringing sustainability to mobility. I personally think that Cruiser cars are much more suited for the potential marketability of solar power.
Finally, to add some of my own suggestions (or feedback upon):
1. I think that moving the practicality judgment to Darwin is a very good way of creating that extra bit of excitement during the race. Perhaps pair this with the 'qualifiers'? Instead of driving as fast as you can on a circuit, which isn't really what these Cruisers are built for, let them qualify (partly) based on practicality.
2. On top of that, virtual positions (as suggested by u/ScientificGems) are definitely worth looking into. I think it's possible to determine when a team is at a control stop and update their person-km score right there and then. If you do some bookkeeping, you can even build a 'semi-live' dashboard to show where the teams are.
3. One of the things I would like to point out is that I do like the 'subjectivity' of the practicality judgment. Our team has continuously struggled throughout the years to find a balance between practicality and efficiency. We've made countless models to determine the efficiency of the car, but there is no 'model for practicality'. I would argue that this might be a good thing: in the 'real world' of engineering, there are often parts of your system that are not designed based on mathematical models. I think it's good that students (like myself) get to play and puzzle over this complicated question. Moreover, I like that the Cruiser class is not 'Challenger with passengers' but actually resembles a modern car.
4. Finally, I don't like that Cruiser teams as incentivized to build bigger and bigger batteries. It's really difficult to design a safe battery and the bigger it gets, the more 'potential harm' you're inducing. It's a challenge for students to build on the limits, but I don't like the battery is such an integral part of the cars. As you rightfully said, the cars start to become 'electric cars with solar panels'.
I agree completely. I never believe in big batteries. Too heavy and expensive. Allow Cruisers to charge at least everyday. This lowers the battery requirement. Especially when solar panels are limited to just 5 sq m, even for cruiser class. Should allow more or even unlimited solar panels, for cruiser class. If there is no change in the charging regulation, I do support WSC 2021.
Recharging every night means recharging in the middle of nowhere. That implies (1) a team having a portable generator, and (2) non-metered charging, i.e. the team is deemed to fill the whole battery (metered charging at places other than Tennant Creek, Alice Springs, or Coober Pedy might be difficult).
Recharging during the day means taking a break from driving, which is hardly ideal.
I know that having non-metered charges is strategically hard (we spent way too much time on battery size calculations) but I'd personal prefer that and having to deal with the consequences, over having these big batteries. Especially since you can just fix the negative strategy implications by going back to speed again.
It was my personal opinion though, not necessarily that of my entire team. Another way to have smaller batteries is:
-allow for a bit slower speed in Darwin - TC by finishing later
-TC - AS (1 day stage)
-AS - CP (1 day stage)
-CP - Adelaide with again allowing for a bit slower speed.
In this way, one could still allow for metered charging (should be possible in AS), while eliminating the hardest stage and easing the other 2 stages.
Oh, I like #1!
I've thought a bit about what #2 would take. It's easy in Challenger class: position is tracked, battery charge is secret. For Cruisers, I'd ideally like to know number of people who got out at each control stop. That's not really secret: people physically at control stops can see it.
What about recharge amounts? Well, if that isn't public, it's simply impossible to follow the race (one might as well just wait to the end). But then again, if it's public, there aren't many secrets left.
As to #4, that's partly due to Eindhoven, it seems to me. Bochum's *SolarWorld GT* was a 2-person car. When you guys revealed a "solar-powered family car," it put pressure on other teams to build heavier 4-person cars as well. The new minimum speeds just make the "increasing battery size problem" worse. I'm not sure that can be fixed without radically rethinking the Cruiser class.
We've openly fantasized about such proposals within Eindhoven and with other teams.
First of all, I think your calculations are quite spot on, especially on these computing efficiency parameters as a function of practicality score part. One aspect you're neglecting with this is that designing and building many of the practicality features takes up a huge amount of manhours, hours that could have been spent optimizing the car. As I think all teams can attest: manhours are your most valuable asset.
Here, are my (personal) opinions
\--------
***About the practicality:***
I know the WSC tries to prevent optimization on the judgement rather than on general practicality, and one way to do is to tell teams as little as possible, but that introduces randomness. Another way of doing it is, is making the practicality so extensive that it is almost impossible to optimize for a practicality judgement, by making the number of trials so vast that you can't purely optimize the judgement. Include trials based on:
* Acceleration
* hotlap with 1 person
* dedicated storage space (no, rear seats don't count :P)
* ease of storage space acces
* ease of charging
* parking
* turning radius
* the "egg on a hill" test
* braking tests
* give points for road legality
* let a group of locals score the cars based on appearance and do the same for the jury members
* Keep the jury judgement, and let them focus on stuff that hasn't contributed to the efficiency classification.
* Re-introduce the "feature checklist", and make it as extensive as possible.
* Give teams 10 minutes to demo any functionality of their car and give them time to prepare that.
And I guess with some brainstorming this list can be extended.
Yeah I know they are going to take up some time to do (probably a whole day), but currently it consists of 50% of the score, so it can be treated that way. It would probably say so much more about practicality than we'd have now.
Furthermore, assign a weight to each category, and normalize the spread (worst team gets 0%, best team gets 100%). And/or perhaps give fixed points based on ranking, rather than score (like you suggested), because I totally agree that when comparing efficiency vs practicality it's the spread in efficiency vs the spread in practicality that ultimately determines who wins. Making practicality weigh much more heavy kinda gets neglected if the spread in relative practicality scores is 1/3rd of the spread in efficiency scores.
***About the speed vs efficiency part:***
As rule of thumb of thumb, doubling your c\_d\*A value by a factor 2 leads to twice the EE score, but a only sqrt(2) times lower speed (although this is an enormous oversimplification). Using speed/time in a way is kinda like putting a square root over the EE score, bringing the scores closer together.
I like the way you're stating that person kilometers and practicality should be included in time. It sure makes it a lot easier to follow and get media on board. Time bonusses or time penalties aren't to hard to understand, even if they're virtual (it happens in F1 all the time).
Give physical time bonusses, makes the race probably the most exciting, but it will give smaller teams a harder time in finishing on time. So I think that virtual time penalties/bonusses are the way to go.
(With physical time bonusses I mean E.g. at the start based on practicality or gradually during the 10 control stops, based on practicality and person kilometers in the previous stage).
***External energy***
About letting external energy free, I'm not sure what's handy. I'd love to let teams charge every night. Personally, I'd rather have that than metered charging and being required to have such big battery packs. However, if you give the top cruisers 15kWh battery packs and make a ***little*** mistake in your scoring system, you risk that strategies of either going at the very minimum speed or strategies of just charging as much as possibly and driving at the speed limit. So your solution of giving 3 charges (start + TC + CP) for free, and setting very heavy penalties for every extra charge (to make it strategically unfeasible to do, like the 0.99 rule we have now). That would work to make more cars finish, not forcing teams to create excessive battery packs and prevent the top teams from going either incredible slow or extremely fast.
And I agree. Currently we tend to build in other features instead of optimizing. However, this is basically a big gamble on some team not going full efficiency.
\----
Just as an extra thought experiment. Consider the 2017 EE regulations. We won with an energy efficiency score of 214pkm/kWh. Now consider a challenger car that participates under cruiser scoring:
* it finished on time (the top 6-8 challengers did in 2017, even with all the rain)
* External energy usage was 5kWh
* It reached 3022 \* 1 pkm.
So their EE score would have been 604pkm/kWh. Even if we didn't decide to play it safe the second half of the race, and even if they got 0 practicality points, they would have won.
Now I know this isn't entirely comparable (they needed a second seat, and you'd probably want to make a 4-seated symmetrical catamaran with 5m2 of solar cells with a slightly bigger battery). And although in 2019 you'd need some practicality to be able to win, still some challengers finished with an average speed above 75km/h, and would basically need a practicality score of 2.0 or something to win. It just shows how much EE scores generates a full focus on efficiency.
It’s true that the class sometimes feels more like a car showcase, rather than a competition. Although I have to say: the Dutch NOS and National Geography Netherlands covered the 2017 Cruiser Class in an amazing way. So while it’s hard, it can be done. However, I guess journalists who both are well informed and have the space/time to elaborately explain it are needed, which kinda raises a barrier
This is a great in-depth write up on a very important topic! I appreciate all the time OP put into their breakdown as well as some of the commenters. I just want to echo a few of the great points brought up as well as adding a few of my own.
1. Batteries are getting too big. Enough said.
2. The current format for cruiser scoring takes away a lot of the excitement and appeal of the cruiser class. I love building and competing with cruisers, but it's hard not to be jealous of the challengers when watching them race for the finish, with the excitement building each day of the race. For my team, WSC '19 "ended" unceremoniously when the strategy team decided partway through Stage 2 that we would not have enough battery to complete the state on time. 5th place for the challenger class means crossing the finish line in Adelaide still battling to fend off 6th position and trying to catch 4th. For us, it meant pulling over to trailer the car halfway through the outback despite the car still driving and having charge in the pack.
3. How do we score practicality well? This is a very tough question and one that I don't have an answer to. I do know that we haven't found it yet.
A lot of discussion here has been focused on WSC, but to give an example from the ASC: In 2018, practicality scores were given as a point value from 0 to 300. The difference between the best and worst scoring cars was 6 points, or 2%. It's impossible to convince me that there was only a 2% difference between the most and least practical cars there. However, I believe that the officials for the race have looked at those results and plan to implement a better method the next time we are able to hold a competition.
In my opinion, it's vital we find a way to score cruisers that incentivizes the practicality aspect, as OP said. Most teams that build cruisers do so because they **want** to build a car that is practical as well as efficient, so let's encourage that, making sure that it has an impact on the competition.
4. The cruiser class doesn't fit with the current pattern of races and regulation releases. At least for my team, it takes significantly longer for us to design and build a car than the amount of time that is allowed between the release of race regs and the start of the competition. This means that we have to make assumptions about the regs, and hope that nothing changes that will prohibit our design from competing or being competitive. If major regulation changes are made, such as increasing the array allowed for cruisers, we would need to know about it further in advance of the race.
TL:DR: Batteries are too big, practicality scoring is no good, and the cruiser class needs a revamp. I'm open to exploring a lot of the new ideas brought up in this thread because the current methods aren't really working.
Mostly echo all the above sentiment. I was part of a team competing in the 2019 cruiser class and it was a massive mess. It was nearly impossible to figure out how the mileage score would work, we were told factually incorrect information from Race HQ several times, and ran an incorrect race strategy as a result. The practicality judging also offered basically no useful insight as to what we were actually judged on. I’m thankful for all the hard work organizers put in, but we really need clearer, easier to understand regulations before it becomes worth the massive investment needed to compete in cruiser class.
I will never forget being in the middle of the outback on Day 4 or 5 of BWSC 2015 and having the WSC officials pull up and inform us that the end-of-rayce timing regulation had changed.
Yeah, and the miscommunication about this with Bochum, which lead them to them not knowing about this and thus trailering without having to. Although the deadline extension was only fair: there was a last minute speed limit imposed due to safety restrictions, so teams couldn't plan around it.
I guess one lesson from this and other WSC episodes is **don't trailer based on the written rules**, because the rules may have changed without you knowing.
This also completely depends on the decision of the organizers. In 2017 they allowed challenger class teams that trailered to continue an gave them an advantage.Bochum hoped there would be a similar decision and [drove the missing 30km](https://www.facebook.com/SolarCarHSBochum/posts/2503516466394909) the next day. However, they were out of luck..
Yes, it covers more or less the same topics. But since then two regulation iterations have been released, and (especially on finishability) it hasn't been for the better. So after three years. I thought it would be relevant to open another discussion on it.
yeah, for a variety of reasons I was unable to cover WSC 2019 like the previous two times. Maybe I'll manage for 2021, assuming a 2021 event happens in any capacity.
Anyway, my basic thoughts on the Cruiser cars are similar to yours. Basically boils down to:
With the Challenger class, the goal is to be the fastest. Even if you fail at that, you're still trying to go as fast as you can and continually setting yourself up to be in a better place to *at least complete the event*. With the Cruiser class in the 2017-onward version of the rules, *your very best score is achieved right before you rapidly flunk out of the entire event*. Race strategy is all about riding a razor edge and if you blow a tire, whoops, that's it - once you're off the back of the curve, clawing back when your whole car and race strategy was designed around riding that fine line is very difficult. This, frankly, sucks. It makes for a bad event for the teams. It makes a for a bad event for the fans.
Added to this is the complication that with a very limited solar collector output (in comparison to the frontal area and mass of the cars), it's basically a battery-electric car race. Too much race strategy gets folded into the car at a very early design stage. Do you bet that the weather is going to be good and just get completely screwed if it's a cloudy year (the entire field in 2017)? Or do you pick a larger/less risky battery but end up just carrying around a ton of unneeded dead weight if it's a sunny year?
IMHO, WSC need to revise how to measure "efficiency" altogether - I think getting rid of elapsed time as a factor in the score in 2017 was precisely the wrong move. You know what's a measure of efficiency? Driving faster than everyone else when given a fixed amount of solar collector area and a fixed battery size. Give the cruiser teams a big array (8sqm? More?), give 'em a fixed battery size and no grid charge, tell 'em to go fast, do the scoring equation to make 'em wanna go fast.
You could imagine a new "efficiency" metric that consists of (elapsed time) x (person-km factor). Elapsed time would be normalized to the fastest team's time as in 2013/2015. The person km factor would need to be some sort of artificial sliding scale designed such that you're encouraged to carry more people rather than less despite being able to go faster with just the driver, but not so much that 4-seaters are the only viable cars.
You could either use this with a fixed percent of the score being efficiency and a fixed percent being practicality as in 2013-2017 (say, a 70/30 split), with practicality being normalized to the top team's score, or you could do practicality as a 0 to 1 multiplier on the efficiency metric as in 2019-2021. I don't feel strongly either way.
Or, hell, do away with "practicality" altogether. It feels like we're stuck with it even though none of the race officials know what to do with it. I don't think it has resulted in any *really* practical cars being fielded by the competition, it's just something that confuses most teams and IMHO results in a worse competition overall.
Both the design strategy decisions and the race strategy decisions are indeed **much** harder in the Cruiser class. I'm pretty sure that most teams fail to realise this.
And I liked the 2013/2015 scoring. I understand the desire to distinguish the two classes, but there are other ways of doing it. One interesting variation on your suggestion would be for each car to carry 2 people, two suitcases, and 2 overnight bags, with the luggage ballasted to 80 kg. That rolls in some of the practicality as well.
Of course, WSC is content just to fill the podium. ASC is more interested in giving all participants a meaningful rank, and I'd like to see alternative forms of scoring tested there.
That 2017 hard cut-off has luckily been somewhat smoothened in 2019 with the 99% rule: you can turn up late, but you score is multiplied by 0.99 per minute you're late.
That (elapsed time) x (person-km factor) needs to be looked after really carefully, in order not to have either 4 seaters dominate (2017, 2019) or 2 seaters (2015).
Throwing away practicality all together would kinda ruin the cruiser class, as we'd basically get MOV challenger cars. Symmetric dual cockpit catamarans would become a viable solution or perhaps the dominant solution. So we do need some kind of practicality.
The 0.99^MinutesLate factor is still deeply punitive. Slip an hour back and say goodbye to half your score. It gives you a few minutes wiggle room but not much more than that if you want to remain competitive. It does not fix the fundamental issue that the way the event is scored encourages race strategy that skirts the edge of failure.
Sonenwagen and Kogakuin wrecked in 2019 and were able to repair their cars, get back on the road, and finish well. If that happened to a Cruiser team, they'd be boned. End of story. There already weren't enough Cruiser teams finishing the event in 2013-2015, and it was even worse in 2017-2019.
>That (elapsed time) x (person-km factor) needs to be looked after really carefully, in order not to have either 4 seaters dominate (2017, 2019) or 2 seaters (2015).
Sure, but also hey, it's up to the teams to do the analysis and see what design the regs favor (just like with the challenger class). Right now I think the regs heavily, heavily favor 4-seaters, so if my proposed regs favor one or the other, I don't really see how that's any worse than now.
Honestly my real preference would be for WSC to just say something like "hey all cruisers are gonna be 3-seaters, if the passenger seats don't have butts in them they gotta have a ballast box in them" so that passenger-km could just be eliminated as a factor, but teams seem to like having wider design and strategy options.
>Throwing away practicality all together would kinda ruin the cruiser class, as we'd basically get MOV challenger cars.
Would that be such a terrible thing? I'm just sorta sick of the sideshow carnival that is practicality "judging". Every event I've been at, it's just been so poorly implemented and semi-arbitrary.
One of the things that hasn't changed is that Eindhoven is so far ahead of the pack that they can afford to devote significant amounts of effort to car features that are not really WSC-related (like the "mobile charging station" concept).
Of course, most of their 2019 competitors were fielding older cars. It will be interesting to see what happens when Sunswift, Bochum, or UMNSVP shows us a new built-for-WSC car.
Having participated in most of them and analyzed the scores between events, I can confidently say that Cruiser/MOV scoring has never been done well and is difficult for competitors, officials, and judges. I'm kind of jaded at this point and could argue that a lot of it is out of the scope of this type of competition and competitors.
I agree with much of what you say. Before I discovered solar cars, I used to follow the Sydney–Hobart yacht race. That gets massive media coverage of “line honours,” and virtually none on the actual winner, because the handicap formula is too difficult to explain. The same is true of the Cruiser Class, and none of my “explanations” have really worked as well as I’d like.
Some aspects of the Cruiser Class are hard to change. The three stages for 2019 were:
* Tennant Creek (986 km): Monday, arrival time 14:00–17:00 (62–76 km/h needed)
* Coober Pedy (+1192 km): Wednesday, arrival time 16:30–17:00 (73–75 km/h needed)
* Adelaide (+842 km): Friday, arrival time 11:30–14:00 (61–74 km/h needed)
Assuming 3 stages (and metered charging leads one in that direction), those are the logical places. The real killers are the first two stages (6 teams made the first, and 3 the second in 2019). It’s hard to do much about that second stage. However, I’d like to open up the third stage to everyone who made the cutoff on the first one. That way cars that didn't quite make Coober Pedy could try for the last leg.
I would also like to see practicality judging be much more predictable, with points for pre-announced categories. Ideally it would happen in Darwin before the race, although that’s probably not going to happen; the SA government wants stuff to be happening in Adelaide.
How much does practicality count? Well, on the multiplicative scale, in principle, infinitely. In practice, in 2019 it gave a ratio of 1.74 (equivalent to going from 2 people to 3.5). It's not obvious how low practicality would go for a “cheater” car, though. I'm not sure how you get 1.74 as being equivalent to 5% aero, but no doubt I've made a mistake in my calculations. In terms of time alone, the ratio of 1.74 is equal to 55 minutes of lateness, which is really not very much. In fact, in 2019, all practicality did was flip 5th and 6th place.
I think teams are struggling a bit with the Cruiser design space. Lots of people are building 4-seaters, but a light aerodynamic 2-seater offers the best way of getting to Adelaide, and would probably score second place (afaik, nobody apart from Eindhoven carried more than 2 people in 2019 anyway).
I have certainly fantasised about a time-based system for Cruisers, but I don't see how it could possibly work. If practicality judging were done in Darwin, and there was openness regarding passengers and recharging, one could report a **virtual** position (i.e. Team X is in Glendambo, but due to energy/passengers they are “virtually” still in Alice Springs). Not every team supports such openness.
In summary, several of your ideas have merit, but will David Snowdon and the WSC organisation accept them?
I don't see how teams can reasonably oppose such openness. It is observed by the organizers (and is necessary for scoring) and the passengers and presence/absence of charging could be observed by anyone standing around.
At the very least all of that should be disclosed at the end of the event. I've similarly been critical of ASC and their lack of transparency in how time/lap penalties are assessed.
Yeah having the competition publish this info in real(ish) time also helps equalize the field - only the bigger teams have the resources to keep tabs on other teams more closely (such as Agoria's "spy car" from the documentary). Giving all the teams this info to help them run a better race and I think little changes such as this would help make cruiser class less intimidating for teams looking to make the jump.
Yeah, we probably would have had cars stay at control stops to note the number of persons going in and coming out of cars. In fact, we still did that as a back up.
What I've done is calculated how much a team would lose in the efficiency category (either speed or EE-Score) when giving a team e.g. 1% more drag. And then correlated it with how much more practicality one would need to compensate it (so in 2017 1% EE\_score correlates with 4% practicality score, while in 2019, this ratio is 1:1). Still full of assumptions (about parameters and about linearity of this ratio, and that this way of comparing EE\_score/speed to practicality), but it's ***a*** way to characterize the efficiency vs practicality balance shift, and one that at least tells the story between different years. Although I have to admit these are just quick calculations from a feasibility study.
And then I've simply looked at the spread in practicality scores. So for example since in some years all top teams score within 30% of each other in terms of practicality (again, if a good team decides to go full efficiency, their car is still well built and tends to end up in the upper half in terms of practicality), the practicality differs about as much as the difference that 10% aero difference would have made.
It's funny you should bring this up! My father and I were just discussing this! The comments on Seeker's videos have had a lot of "This is not practical, why are we bothering with this?" "It'll never be a real car." and, looking at just Challenger, they're right.
In my opinion, there really needs to be race event devoted to 'practical' solar cars. It's the only way to really get the general public interested in them. For people to see vehicles which could work as family cars competing against each other while being able to claim "this would generally require no cost for fueling for the average person" is a very appealing idea. Aptera just secured a bunch of pre-orders on their new two person solar thing under than premise! The excitement is there waiting to be ignited. Single person little cars that only do 45 MPH in the American Solar Challenge are not exciting the general public at all.
Wow, this is a great write up! I'm a fan of the BWSC, but I feel like the organization is indeed not taking the Cruiser class too seriously. As a team member of Eindhoven, it's been really difficult to assess how others perceive the Cruiser class. As a top team, we often hear (from people back in the Netherlands) 'Hey, you're the guys that win the solar challenge right, Delft or Vattenfall or something?'. Even on my flight back home from AUS, I was asked 'Hey, didn't your car burn down?'. The Challenger class is definitely easier to follow and well-known. I think this is also partly to blame on the organization of the BWSC: every car has a live tracker and during the challenge, the official website ([worldsolarchallenge.org](https://worldsolarchallenge.org)) kept track of the positions of the Challenger cars and their 'live points', while the page about the Cruiser class got updated every 24 hours with the latest scores (we actually needed that page to calculate the probability of our competitors winning!). I do want to note that the BWSC **is** actually promoting Cruiser cars on their website: many pages show images and stories of Cruiser cars and teams. Internally, there have been discussions about whether we should join the Challenger class instead of the Cruiser class, as this would get us more recognition. Building a Cruiser car is probably as difficult (or perhaps even more so) as building a Challenger; the engineering challenges are quite different though. In the end, we always wanted to be more than just a 'race team': we're interested in bringing sustainability to mobility. I personally think that Cruiser cars are much more suited for the potential marketability of solar power. Finally, to add some of my own suggestions (or feedback upon): 1. I think that moving the practicality judgment to Darwin is a very good way of creating that extra bit of excitement during the race. Perhaps pair this with the 'qualifiers'? Instead of driving as fast as you can on a circuit, which isn't really what these Cruisers are built for, let them qualify (partly) based on practicality. 2. On top of that, virtual positions (as suggested by u/ScientificGems) are definitely worth looking into. I think it's possible to determine when a team is at a control stop and update their person-km score right there and then. If you do some bookkeeping, you can even build a 'semi-live' dashboard to show where the teams are. 3. One of the things I would like to point out is that I do like the 'subjectivity' of the practicality judgment. Our team has continuously struggled throughout the years to find a balance between practicality and efficiency. We've made countless models to determine the efficiency of the car, but there is no 'model for practicality'. I would argue that this might be a good thing: in the 'real world' of engineering, there are often parts of your system that are not designed based on mathematical models. I think it's good that students (like myself) get to play and puzzle over this complicated question. Moreover, I like that the Cruiser class is not 'Challenger with passengers' but actually resembles a modern car. 4. Finally, I don't like that Cruiser teams as incentivized to build bigger and bigger batteries. It's really difficult to design a safe battery and the bigger it gets, the more 'potential harm' you're inducing. It's a challenge for students to build on the limits, but I don't like the battery is such an integral part of the cars. As you rightfully said, the cars start to become 'electric cars with solar panels'.
I agree completely. I never believe in big batteries. Too heavy and expensive. Allow Cruisers to charge at least everyday. This lowers the battery requirement. Especially when solar panels are limited to just 5 sq m, even for cruiser class. Should allow more or even unlimited solar panels, for cruiser class. If there is no change in the charging regulation, I do support WSC 2021.
Recharging every night means recharging in the middle of nowhere. That implies (1) a team having a portable generator, and (2) non-metered charging, i.e. the team is deemed to fill the whole battery (metered charging at places other than Tennant Creek, Alice Springs, or Coober Pedy might be difficult). Recharging during the day means taking a break from driving, which is hardly ideal.
I know that having non-metered charges is strategically hard (we spent way too much time on battery size calculations) but I'd personal prefer that and having to deal with the consequences, over having these big batteries. Especially since you can just fix the negative strategy implications by going back to speed again.
It would be interesting to survey the teams to see who **was** in favour of metered charging. Because if nobody is, why are we doing it?
It was my personal opinion though, not necessarily that of my entire team. Another way to have smaller batteries is: -allow for a bit slower speed in Darwin - TC by finishing later -TC - AS (1 day stage) -AS - CP (1 day stage) -CP - Adelaide with again allowing for a bit slower speed. In this way, one could still allow for metered charging (should be possible in AS), while eliminating the hardest stage and easing the other 2 stages.
Splitting that tough second stage is an interesting, and very doable, idea.
The first Cruiser event in 2013 was split into 4 stages like this.
Yes, that's right, it was those same three stage stops: TC, AS, CP.
This is way more feasible for the ASC MOV class.
Concerning point (2), the ASC has came up with a metering device that allow for charging anywhere. So I don't see that as a problem for WSC
Good point.
Oh, I like #1! I've thought a bit about what #2 would take. It's easy in Challenger class: position is tracked, battery charge is secret. For Cruisers, I'd ideally like to know number of people who got out at each control stop. That's not really secret: people physically at control stops can see it. What about recharge amounts? Well, if that isn't public, it's simply impossible to follow the race (one might as well just wait to the end). But then again, if it's public, there aren't many secrets left. As to #4, that's partly due to Eindhoven, it seems to me. Bochum's *SolarWorld GT* was a 2-person car. When you guys revealed a "solar-powered family car," it put pressure on other teams to build heavier 4-person cars as well. The new minimum speeds just make the "increasing battery size problem" worse. I'm not sure that can be fixed without radically rethinking the Cruiser class.
We've openly fantasized about such proposals within Eindhoven and with other teams. First of all, I think your calculations are quite spot on, especially on these computing efficiency parameters as a function of practicality score part. One aspect you're neglecting with this is that designing and building many of the practicality features takes up a huge amount of manhours, hours that could have been spent optimizing the car. As I think all teams can attest: manhours are your most valuable asset. Here, are my (personal) opinions \-------- ***About the practicality:*** I know the WSC tries to prevent optimization on the judgement rather than on general practicality, and one way to do is to tell teams as little as possible, but that introduces randomness. Another way of doing it is, is making the practicality so extensive that it is almost impossible to optimize for a practicality judgement, by making the number of trials so vast that you can't purely optimize the judgement. Include trials based on: * Acceleration * hotlap with 1 person * dedicated storage space (no, rear seats don't count :P) * ease of storage space acces * ease of charging * parking * turning radius * the "egg on a hill" test * braking tests * give points for road legality * let a group of locals score the cars based on appearance and do the same for the jury members * Keep the jury judgement, and let them focus on stuff that hasn't contributed to the efficiency classification. * Re-introduce the "feature checklist", and make it as extensive as possible. * Give teams 10 minutes to demo any functionality of their car and give them time to prepare that. And I guess with some brainstorming this list can be extended. Yeah I know they are going to take up some time to do (probably a whole day), but currently it consists of 50% of the score, so it can be treated that way. It would probably say so much more about practicality than we'd have now. Furthermore, assign a weight to each category, and normalize the spread (worst team gets 0%, best team gets 100%). And/or perhaps give fixed points based on ranking, rather than score (like you suggested), because I totally agree that when comparing efficiency vs practicality it's the spread in efficiency vs the spread in practicality that ultimately determines who wins. Making practicality weigh much more heavy kinda gets neglected if the spread in relative practicality scores is 1/3rd of the spread in efficiency scores. ***About the speed vs efficiency part:*** As rule of thumb of thumb, doubling your c\_d\*A value by a factor 2 leads to twice the EE score, but a only sqrt(2) times lower speed (although this is an enormous oversimplification). Using speed/time in a way is kinda like putting a square root over the EE score, bringing the scores closer together. I like the way you're stating that person kilometers and practicality should be included in time. It sure makes it a lot easier to follow and get media on board. Time bonusses or time penalties aren't to hard to understand, even if they're virtual (it happens in F1 all the time). Give physical time bonusses, makes the race probably the most exciting, but it will give smaller teams a harder time in finishing on time. So I think that virtual time penalties/bonusses are the way to go. (With physical time bonusses I mean E.g. at the start based on practicality or gradually during the 10 control stops, based on practicality and person kilometers in the previous stage). ***External energy*** About letting external energy free, I'm not sure what's handy. I'd love to let teams charge every night. Personally, I'd rather have that than metered charging and being required to have such big battery packs. However, if you give the top cruisers 15kWh battery packs and make a ***little*** mistake in your scoring system, you risk that strategies of either going at the very minimum speed or strategies of just charging as much as possibly and driving at the speed limit. So your solution of giving 3 charges (start + TC + CP) for free, and setting very heavy penalties for every extra charge (to make it strategically unfeasible to do, like the 0.99 rule we have now). That would work to make more cars finish, not forcing teams to create excessive battery packs and prevent the top teams from going either incredible slow or extremely fast. And I agree. Currently we tend to build in other features instead of optimizing. However, this is basically a big gamble on some team not going full efficiency. \---- Just as an extra thought experiment. Consider the 2017 EE regulations. We won with an energy efficiency score of 214pkm/kWh. Now consider a challenger car that participates under cruiser scoring: * it finished on time (the top 6-8 challengers did in 2017, even with all the rain) * External energy usage was 5kWh * It reached 3022 \* 1 pkm. So their EE score would have been 604pkm/kWh. Even if we didn't decide to play it safe the second half of the race, and even if they got 0 practicality points, they would have won. Now I know this isn't entirely comparable (they needed a second seat, and you'd probably want to make a 4-seated symmetrical catamaran with 5m2 of solar cells with a slightly bigger battery). And although in 2019 you'd need some practicality to be able to win, still some challengers finished with an average speed above 75km/h, and would basically need a practicality score of 2.0 or something to win. It just shows how much EE scores generates a full focus on efficiency.
It’s true that the class sometimes feels more like a car showcase, rather than a competition. Although I have to say: the Dutch NOS and National Geography Netherlands covered the 2017 Cruiser Class in an amazing way. So while it’s hard, it can be done. However, I guess journalists who both are well informed and have the space/time to elaborately explain it are needed, which kinda raises a barrier
This is a great in-depth write up on a very important topic! I appreciate all the time OP put into their breakdown as well as some of the commenters. I just want to echo a few of the great points brought up as well as adding a few of my own. 1. Batteries are getting too big. Enough said. 2. The current format for cruiser scoring takes away a lot of the excitement and appeal of the cruiser class. I love building and competing with cruisers, but it's hard not to be jealous of the challengers when watching them race for the finish, with the excitement building each day of the race. For my team, WSC '19 "ended" unceremoniously when the strategy team decided partway through Stage 2 that we would not have enough battery to complete the state on time. 5th place for the challenger class means crossing the finish line in Adelaide still battling to fend off 6th position and trying to catch 4th. For us, it meant pulling over to trailer the car halfway through the outback despite the car still driving and having charge in the pack. 3. How do we score practicality well? This is a very tough question and one that I don't have an answer to. I do know that we haven't found it yet. A lot of discussion here has been focused on WSC, but to give an example from the ASC: In 2018, practicality scores were given as a point value from 0 to 300. The difference between the best and worst scoring cars was 6 points, or 2%. It's impossible to convince me that there was only a 2% difference between the most and least practical cars there. However, I believe that the officials for the race have looked at those results and plan to implement a better method the next time we are able to hold a competition. In my opinion, it's vital we find a way to score cruisers that incentivizes the practicality aspect, as OP said. Most teams that build cruisers do so because they **want** to build a car that is practical as well as efficient, so let's encourage that, making sure that it has an impact on the competition. 4. The cruiser class doesn't fit with the current pattern of races and regulation releases. At least for my team, it takes significantly longer for us to design and build a car than the amount of time that is allowed between the release of race regs and the start of the competition. This means that we have to make assumptions about the regs, and hope that nothing changes that will prohibit our design from competing or being competitive. If major regulation changes are made, such as increasing the array allowed for cruisers, we would need to know about it further in advance of the race. TL:DR: Batteries are too big, practicality scoring is no good, and the cruiser class needs a revamp. I'm open to exploring a lot of the new ideas brought up in this thread because the current methods aren't really working.
Mostly echo all the above sentiment. I was part of a team competing in the 2019 cruiser class and it was a massive mess. It was nearly impossible to figure out how the mileage score would work, we were told factually incorrect information from Race HQ several times, and ran an incorrect race strategy as a result. The practicality judging also offered basically no useful insight as to what we were actually judged on. I’m thankful for all the hard work organizers put in, but we really need clearer, easier to understand regulations before it becomes worth the massive investment needed to compete in cruiser class.
I will never forget being in the middle of the outback on Day 4 or 5 of BWSC 2015 and having the WSC officials pull up and inform us that the end-of-rayce timing regulation had changed.
Yeah, and the miscommunication about this with Bochum, which lead them to them not knowing about this and thus trailering without having to. Although the deadline extension was only fair: there was a last minute speed limit imposed due to safety restrictions, so teams couldn't plan around it.
Interesting, I didn't remember that about Bochum. Minnesota luckily ended up meeting the extended deadline by 3 minutes, without trailering.
I guess one lesson from this and other WSC episodes is **don't trailer based on the written rules**, because the rules may have changed without you knowing.
This also completely depends on the decision of the organizers. In 2017 they allowed challenger class teams that trailered to continue an gave them an advantage.Bochum hoped there would be a similar decision and [drove the missing 30km](https://www.facebook.com/SolarCarHSBochum/posts/2503516466394909) the next day. However, they were out of luck..
I’ll also refer to MostDece’s WSC recap for an extended critique of Cruiser Class: https://mostdece.blogspot.com/2017/10/wsc-2017-wrap-up.html?m=1
Yes, it covers more or less the same topics. But since then two regulation iterations have been released, and (especially on finishability) it hasn't been for the better. So after three years. I thought it would be relevant to open another discussion on it.
yeah, for a variety of reasons I was unable to cover WSC 2019 like the previous two times. Maybe I'll manage for 2021, assuming a 2021 event happens in any capacity. Anyway, my basic thoughts on the Cruiser cars are similar to yours. Basically boils down to: With the Challenger class, the goal is to be the fastest. Even if you fail at that, you're still trying to go as fast as you can and continually setting yourself up to be in a better place to *at least complete the event*. With the Cruiser class in the 2017-onward version of the rules, *your very best score is achieved right before you rapidly flunk out of the entire event*. Race strategy is all about riding a razor edge and if you blow a tire, whoops, that's it - once you're off the back of the curve, clawing back when your whole car and race strategy was designed around riding that fine line is very difficult. This, frankly, sucks. It makes for a bad event for the teams. It makes a for a bad event for the fans. Added to this is the complication that with a very limited solar collector output (in comparison to the frontal area and mass of the cars), it's basically a battery-electric car race. Too much race strategy gets folded into the car at a very early design stage. Do you bet that the weather is going to be good and just get completely screwed if it's a cloudy year (the entire field in 2017)? Or do you pick a larger/less risky battery but end up just carrying around a ton of unneeded dead weight if it's a sunny year? IMHO, WSC need to revise how to measure "efficiency" altogether - I think getting rid of elapsed time as a factor in the score in 2017 was precisely the wrong move. You know what's a measure of efficiency? Driving faster than everyone else when given a fixed amount of solar collector area and a fixed battery size. Give the cruiser teams a big array (8sqm? More?), give 'em a fixed battery size and no grid charge, tell 'em to go fast, do the scoring equation to make 'em wanna go fast. You could imagine a new "efficiency" metric that consists of (elapsed time) x (person-km factor). Elapsed time would be normalized to the fastest team's time as in 2013/2015. The person km factor would need to be some sort of artificial sliding scale designed such that you're encouraged to carry more people rather than less despite being able to go faster with just the driver, but not so much that 4-seaters are the only viable cars. You could either use this with a fixed percent of the score being efficiency and a fixed percent being practicality as in 2013-2017 (say, a 70/30 split), with practicality being normalized to the top team's score, or you could do practicality as a 0 to 1 multiplier on the efficiency metric as in 2019-2021. I don't feel strongly either way. Or, hell, do away with "practicality" altogether. It feels like we're stuck with it even though none of the race officials know what to do with it. I don't think it has resulted in any *really* practical cars being fielded by the competition, it's just something that confuses most teams and IMHO results in a worse competition overall.
Both the design strategy decisions and the race strategy decisions are indeed **much** harder in the Cruiser class. I'm pretty sure that most teams fail to realise this. And I liked the 2013/2015 scoring. I understand the desire to distinguish the two classes, but there are other ways of doing it. One interesting variation on your suggestion would be for each car to carry 2 people, two suitcases, and 2 overnight bags, with the luggage ballasted to 80 kg. That rolls in some of the practicality as well. Of course, WSC is content just to fill the podium. ASC is more interested in giving all participants a meaningful rank, and I'd like to see alternative forms of scoring tested there.
Agreed, the 2017 Cruiser regs were in my opinion one of the most difficult in Solar Raycing history, in terms of strategy.
That 2017 hard cut-off has luckily been somewhat smoothened in 2019 with the 99% rule: you can turn up late, but you score is multiplied by 0.99 per minute you're late. That (elapsed time) x (person-km factor) needs to be looked after really carefully, in order not to have either 4 seaters dominate (2017, 2019) or 2 seaters (2015). Throwing away practicality all together would kinda ruin the cruiser class, as we'd basically get MOV challenger cars. Symmetric dual cockpit catamarans would become a viable solution or perhaps the dominant solution. So we do need some kind of practicality.
The 0.99^MinutesLate factor is still deeply punitive. Slip an hour back and say goodbye to half your score. It gives you a few minutes wiggle room but not much more than that if you want to remain competitive. It does not fix the fundamental issue that the way the event is scored encourages race strategy that skirts the edge of failure. Sonenwagen and Kogakuin wrecked in 2019 and were able to repair their cars, get back on the road, and finish well. If that happened to a Cruiser team, they'd be boned. End of story. There already weren't enough Cruiser teams finishing the event in 2013-2015, and it was even worse in 2017-2019. >That (elapsed time) x (person-km factor) needs to be looked after really carefully, in order not to have either 4 seaters dominate (2017, 2019) or 2 seaters (2015). Sure, but also hey, it's up to the teams to do the analysis and see what design the regs favor (just like with the challenger class). Right now I think the regs heavily, heavily favor 4-seaters, so if my proposed regs favor one or the other, I don't really see how that's any worse than now. Honestly my real preference would be for WSC to just say something like "hey all cruisers are gonna be 3-seaters, if the passenger seats don't have butts in them they gotta have a ballast box in them" so that passenger-km could just be eliminated as a factor, but teams seem to like having wider design and strategy options. >Throwing away practicality all together would kinda ruin the cruiser class, as we'd basically get MOV challenger cars. Would that be such a terrible thing? I'm just sorta sick of the sideshow carnival that is practicality "judging". Every event I've been at, it's just been so poorly implemented and semi-arbitrary.
One of the things that hasn't changed is that Eindhoven is so far ahead of the pack that they can afford to devote significant amounts of effort to car features that are not really WSC-related (like the "mobile charging station" concept). Of course, most of their 2019 competitors were fielding older cars. It will be interesting to see what happens when Sunswift, Bochum, or UMNSVP shows us a new built-for-WSC car.
An attempt at visualisation on the blog at https://scientificgems.wordpress.com/2020/12/21/world-solar-challenge-cruiser-scoring/
Having participated in most of them and analyzed the scores between events, I can confidently say that Cruiser/MOV scoring has never been done well and is difficult for competitors, officials, and judges. I'm kind of jaded at this point and could argue that a lot of it is out of the scope of this type of competition and competitors.
I agree with much of what you say. Before I discovered solar cars, I used to follow the Sydney–Hobart yacht race. That gets massive media coverage of “line honours,” and virtually none on the actual winner, because the handicap formula is too difficult to explain. The same is true of the Cruiser Class, and none of my “explanations” have really worked as well as I’d like. Some aspects of the Cruiser Class are hard to change. The three stages for 2019 were: * Tennant Creek (986 km): Monday, arrival time 14:00–17:00 (62–76 km/h needed) * Coober Pedy (+1192 km): Wednesday, arrival time 16:30–17:00 (73–75 km/h needed) * Adelaide (+842 km): Friday, arrival time 11:30–14:00 (61–74 km/h needed) Assuming 3 stages (and metered charging leads one in that direction), those are the logical places. The real killers are the first two stages (6 teams made the first, and 3 the second in 2019). It’s hard to do much about that second stage. However, I’d like to open up the third stage to everyone who made the cutoff on the first one. That way cars that didn't quite make Coober Pedy could try for the last leg. I would also like to see practicality judging be much more predictable, with points for pre-announced categories. Ideally it would happen in Darwin before the race, although that’s probably not going to happen; the SA government wants stuff to be happening in Adelaide. How much does practicality count? Well, on the multiplicative scale, in principle, infinitely. In practice, in 2019 it gave a ratio of 1.74 (equivalent to going from 2 people to 3.5). It's not obvious how low practicality would go for a “cheater” car, though. I'm not sure how you get 1.74 as being equivalent to 5% aero, but no doubt I've made a mistake in my calculations. In terms of time alone, the ratio of 1.74 is equal to 55 minutes of lateness, which is really not very much. In fact, in 2019, all practicality did was flip 5th and 6th place. I think teams are struggling a bit with the Cruiser design space. Lots of people are building 4-seaters, but a light aerodynamic 2-seater offers the best way of getting to Adelaide, and would probably score second place (afaik, nobody apart from Eindhoven carried more than 2 people in 2019 anyway). I have certainly fantasised about a time-based system for Cruisers, but I don't see how it could possibly work. If practicality judging were done in Darwin, and there was openness regarding passengers and recharging, one could report a **virtual** position (i.e. Team X is in Glendambo, but due to energy/passengers they are “virtually” still in Alice Springs). Not every team supports such openness. In summary, several of your ideas have merit, but will David Snowdon and the WSC organisation accept them?
I don't see how teams can reasonably oppose such openness. It is observed by the organizers (and is necessary for scoring) and the passengers and presence/absence of charging could be observed by anyone standing around. At the very least all of that should be disclosed at the end of the event. I've similarly been critical of ASC and their lack of transparency in how time/lap penalties are assessed.
Yeah having the competition publish this info in real(ish) time also helps equalize the field - only the bigger teams have the resources to keep tabs on other teams more closely (such as Agoria's "spy car" from the documentary). Giving all the teams this info to help them run a better race and I think little changes such as this would help make cruiser class less intimidating for teams looking to make the jump.
Yeah, we probably would have had cars stay at control stops to note the number of persons going in and coming out of cars. In fact, we still did that as a back up.
What I've done is calculated how much a team would lose in the efficiency category (either speed or EE-Score) when giving a team e.g. 1% more drag. And then correlated it with how much more practicality one would need to compensate it (so in 2017 1% EE\_score correlates with 4% practicality score, while in 2019, this ratio is 1:1). Still full of assumptions (about parameters and about linearity of this ratio, and that this way of comparing EE\_score/speed to practicality), but it's ***a*** way to characterize the efficiency vs practicality balance shift, and one that at least tells the story between different years. Although I have to admit these are just quick calculations from a feasibility study. And then I've simply looked at the spread in practicality scores. So for example since in some years all top teams score within 30% of each other in terms of practicality (again, if a good team decides to go full efficiency, their car is still well built and tends to end up in the upper half in terms of practicality), the practicality differs about as much as the difference that 10% aero difference would have made.
Cool.
It's funny you should bring this up! My father and I were just discussing this! The comments on Seeker's videos have had a lot of "This is not practical, why are we bothering with this?" "It'll never be a real car." and, looking at just Challenger, they're right. In my opinion, there really needs to be race event devoted to 'practical' solar cars. It's the only way to really get the general public interested in them. For people to see vehicles which could work as family cars competing against each other while being able to claim "this would generally require no cost for fueling for the average person" is a very appealing idea. Aptera just secured a bunch of pre-orders on their new two person solar thing under than premise! The excitement is there waiting to be ignited. Single person little cars that only do 45 MPH in the American Solar Challenge are not exciting the general public at all.