Hovercraft B/C

[meierfra]

Note we've posted an official scoring sheet (per rule 6) on the website, which per general rule #3 (https://www.soinc.org/ethics_rules) should be treated as if they are part of the rules. You can play around with it to see how the scoring works.

Although the scoring spreadsheet doesn't help with what mass is used. It merely asks the Event Supervisor to input the mass. At that point, the ES must have already made a decision on what mass to use.

[chalker]

Teams aren't adjusting their timing for different masses though, they will be testing their crafts with a low mass and ensuring their craft can move with a large mass so that they can score the mass score. This "superscoring loophole" does not force students to learn how to adapt to different situations and it does not make the scores at higher levels of competition less differentiated, it does the opposite. The biggest challenge of this event is figuring out how to minimize pressure losses so a large mass can be moved at relatively high speeds. Once you eliminate that challenge, the event becomes very simple and all the top teams will have full mass score regardless of if they actually figure out how to levitate a large mass and the entire build portion of the event will come down to who can get tenths of a second closer to the target time.

I disagree with you about the 'biggest challenge'. Perhaps that's true for the elite teams, but for the majority of the teams it's just getting a design that works at all.

Last year during the trial event phase of this event we saw 4 general types of vehicles:
1. Ones that didn't move at all or so slowly they couldn't complete the course in a reasonable time
2. Ones that moved pretty slowly, essentially weren't adjustable at all and completed the course in a reasonable time
3. Ones that moved pretty well, and had some sort of adjustable speed setting (some via mass changes), and completed the course
4. Ones that had max mass, adjustable speed setting and completed the course very close to target time

We know there will be lots of type #4 at Nationals (which is what you have described) and they will fundamentally come down to tenths of a second and grams of weight. But keep in mind there is a wide variation in the possible times, so there is a significant challenge in figuring out how to adjust speed for such a range.

But as I've said numerous times before, we can't just write the rules for the best teams in the country. We're trying to encourage the #2 and #3 types to experiment more and try to maximize their score via both time and mass adjustment. Most of the vehicles will still have quite a bit of friction and uncertainty in their design and performance.

[chalker]

Note we've posted an official scoring sheet (per rule 6) on the website, which per general rule #3 (https://www.soinc.org/ethics_rules) should be treated as if they are part of the rules. You can play around with it to see how the scoring works.

Although the scoring spreadsheet doesn't help with what mass is used. It merely asks the Event Supervisor to input the mass. At that point, the ES must have already made a decision on what mass to use.

I think that reinforces my point. It doesn't ask for multiple mass numbers because the assumption is that the supervisor will only input 1 number. I think most people would see that and when presented with a situation where the team increased the mass during the run would realize they should put in the final max mass.

[windu34]

I disagree with you about the 'biggest challenge'. Perhaps that's true for the elite teams, but for the majority of the teams it's just getting a design that works at all.

Last year during the trial event phase of this event we saw 4 general types of vehicles:
1. Ones that didn't move at all or so slowly they couldn't complete the course in a reasonable time
2. Ones that moved pretty slowly, essentially weren't adjustable at all and completed the course in a reasonable time
3. Ones that moved pretty well, and had some sort of adjustable speed setting (some via mass changes), and completed the course
4. Ones that had max mass, adjustable speed setting and completed the course very close to target time

We know there will be lots of type #4 at Nationals (which is what you have described) and they will fundamentally come down to tenths of a second and grams of weight. But keep in mind there is a wide variation in the possible times, so there is a significant challenge in figuring out how to adjust speed for such a range.

But as I've said numerous times before, we can't just write the rules for the best teams in the country. We're trying to encourage the #2 and #3 types to experiment more and try to maximize their score via both time and mass adjustment. Most of the vehicles will still have quite a bit of friction and uncertainty in their design and performance.

But is adjusting speed really a challenge? It is quite simple and well known to most that current and motor torque have a direct correlation and that is all you really need to know to be able to get within tenths of a second (some data collection involved). Assuming you keep your craft consistent as far as the frame and mass, the results are relatively repeatable.
Can you provide some insight into the similarities with maglev? Did maglev have this concept as well? How were the builds at nationals (seeing as how it is essentially the same event, a lot of the patterns should apply)

[SPP SciO]

Wow - I hadn't even realized that the mass/time scores could be from different runs until now. Chalker, I understood your rationale, but I would say that this seems to break from the traditional build event challenges, which may have two components to a score that are trade-offs, and the challenge is finding the optimum point. Balsa events try to build light and strong simultaneously, a Scrambler vehicle needs to be fast and accurate simultaneously, Mission Possible is complex and reliable, etc. I would have thought that Hovercraft would have been designed to push students towards building heavy and fast, at the same time. Realizing how it's scored now, it seems like the challenge remains the same but there's certainly room for more gamesmanship with scoring.

[chalker]

But is adjusting speed really a challenge? It is quite simple and well known to most that current and motor torque have a direct correlation and that is all you really need to know to be able to get within tenths of a second (some data collection involved). Assuming you keep your craft consistent as far as the frame and mass, the results are relatively repeatable.
Can you provide some insight into the similarities with maglev? Did maglev have this concept as well? How were the builds at nationals (seeing as how it is essentially the same event, a lot of the patterns should apply)

I just checked, and the official scoresheet for MagLev had the same calculations behind the scenes (i.e. MS and TS were independent). The wording in Maglev's scoring section of the rules was almost identical. There is a bit of a difference though in that we allowed for 2 vehicles to be used, so we had to record 2 different masses and indicate which vehicle had a successful run.

I think you are underestimating the challenge in adjusting speed to meet a set time on an unknown track in a limited amount of time. There are lots of parameters involved such as battery voltage, friction on the track, and acceleration curves.

The last time it was run at Nationals in 2014, there was a 6 point (~10% difference) in the final scores between first place and sixth place. That's pretty significant and clearly not down to 'tenths of a second'. I know there were several max mass vehicles as well.

[55555]

So are you guys going to use computer fans for the thrust fan too b/c I'm having trouble finding brushed motors that can fit propellers/ come with propellers.

[rschmitz]

Is a potentiometer considered an integrated circuit?
Oh and FYI i get a lot of my motors for Hovercraft and Electric Vehicle by buying toys from the local thrift stores. The students have a blast pulling them apart.

[windu34]

So are you guys going to use computer fans for the thrust fan too b/c I'm having trouble finding brushed motors that can fit propellers/ come with propellers.

There are adapters available for that

[windu34]

Is a potentiometer considered an integrated circuit?
Oh and FYI i get a lot of my motors for Hovercraft and Electric Vehicle by buying toys from the local thrift stores. The students have a blast pulling them apart.

No potentiometers contain only resistive elements