Hovercraft B/C

[Ashernoel]

Pots are heavy (150g+), and with a goal of low weight so that it can lift with the pennies, using lighter methods of speed control can help achieve a reliable lift and maximum weight. Idk, though, as I have not yet started building any prototypes or anything for this year .

Side question: What do you guys think is the likelihood of a gym floor being used as the track?

[cheese]

Side question: What do you guys think is the likelihood of a gym floor being used as the track?

It depends on the gym obviously, but if its a waxed (classic basketball court), It may not be the smoothest. I think most competitors would prefer a smooth table.

[cheese]

I wonder though, will people stick to the potentiometer method this year or try to find some other mechanism. I know this is not the place for official clarifications, but could it be possible to power both a fan and something else off a motor?

I don't see why you wouldn't be able to, I think you're talking about some gear system off of it, but as ashernoel said, it could possibly be heavier, and as far as I can tell, the best strategy is to have your batteries, motors, and base all be as light as possible so you can hold the max pennies.

[chalker]

Side question: What do you guys think is the likelihood of a gym floor being used as the track?

Just wanted to let you all know this is HIGHLY likely. We revised the rules this year regarding the tracks with exactly this in mind. When i get around to posting the track document on the event page it will explicitly mention this as a possibility.

[Crtomir]

I understand the lithium battery ban from a safety point of view, but this is super inconveniencing for me. The only way I was able to get our hovercraft running last year was with lithium batteries, anything else did not have enough power to lift it's own weight. I ended up buying quite a few, as well as a decent balance charger, and now the team has no use for them this year. Any ideas on good batteries that fit the requirements?

I am a personal fan of NiMH batteries. They are substantially heavier than the LiPOs, but are probably the best option. I use Racer's Edge batteries, but I've heard good things about Traxxas batteries as well. It's definitely a good idea to get a smart charger, meaning it'll automatically shut off once the battery is full if you plan to reuse batteries.

The nice thing about NiMH is that you can overcharge them legally, because they must be <9.0V by labels. So you can have a 9.5V - 10.0V battery and still be within the rules. The issue there is that you risk damaging the battery, so I'd cycle them every once in a while. You seem to be worried about it lifting its own weight. Note that you have 33% more surface to work with, and with the added voltage of the NiMH, you ought to easily be able to hold everything

Going to use this opportunity to chime in on the battery changes a bit. The rules committee had EXTENSIVE debate about lithium batteries. I personally was on the side of allowing them, however the group opinion decided to prohibit them for at least this year. While I will support that, I'll also continue to advocate for allowing them in the future. There are a LOT of factors that come into play with something like this. We've posted a policy document explaining some of them on soinc.org (https://www.soinc.org/sites/default/fil ... cy18_0.pdf ) and I'd like to point out it explicitly only talks about THIS season for this very reason.

By the way, I just looked up the Materials Safety Data sheet for NiMH batteries and guess what? They contain Lithium!!!! Agghhh! I just spent $150+ on a new recharger and NiMH batteries (because our old expensive LiPo batteries and charger will not work for this season) and it's wasted. Find out for yourself. https://system.na3.netsuite.com/core/me ... c&_xt=.pdf Just to repeat: NiMH batteries DO CONTAIN LITHIUM. So they are not allowed according to this year's rules. Darn!

[Crtomir]

I am a personal fan of NiMH batteries. They are substantially heavier than the LiPOs, but are probably the best option. I use Racer's Edge batteries, but I've heard good things about Traxxas batteries as well. It's definitely a good idea to get a smart charger, meaning it'll automatically shut off once the battery is full if you plan to reuse batteries.

The nice thing about NiMH is that you can overcharge them legally, because they must be <9.0V by labels. So you can have a 9.5V - 10.0V battery and still be within the rules. The issue there is that you risk damaging the battery, so I'd cycle them every once in a while. You seem to be worried about it lifting its own weight. Note that you have 33% more surface to work with, and with the added voltage of the NiMH, you ought to easily be able to hold everything

Going to use this opportunity to chime in on the battery changes a bit. The rules committee had EXTENSIVE debate about lithium batteries. I personally was on the side of allowing them, however the group opinion decided to prohibit them for at least this year. While I will support that, I'll also continue to advocate for allowing them in the future. There are a LOT of factors that come into play with something like this. We've posted a policy document explaining some of them on soinc.org (https://www.soinc.org/sites/default/fil ... cy18_0.pdf ) and I'd like to point out it explicitly only talks about THIS season for this very reason.

By the way, I just looked up the Materials Safety Data sheet for NiMH batteries and guess what? They contain Lithium!!!! Agghhh! I just spent $150+ on a new recharger and NiMH batteries (because our old expensive LiPo batteries and charger will not work for this season) and it's wasted. Find out for yourself. https://system.na3.netsuite.com/core/me ... c&_xt=.pdf Just to repeat: NiMH batteries DO CONTAIN LITHIUM. So they are not allowed according to this year's rules. Darn!

More evidence that NiMH batteries have lithium: https://www.batterystore.com/content/MS ... e_MSDS.pdf and https://www.batteriesplus.com/image/sds-Empire-NiMH.pdf

[chalker]

Going to use this opportunity to chime in on the battery changes a bit. The rules committee had EXTENSIVE debate about lithium batteries. I personally was on the side of allowing them, however the group opinion decided to prohibit them for at least this year. While I will support that, I'll also continue to advocate for allowing them in the future. There are a LOT of factors that come into play with something like this. We've posted a policy document explaining some of them on soinc.org (https://www.soinc.org/sites/default/fil ... cy18_0.pdf ) and I'd like to point out it explicitly only talks about THIS season for this very reason.

By the way, I just looked up the Materials Safety Data sheet for NiMH batteries and guess what? They contain Lithium!!!! Agghhh! I just spent $150+ on a new recharger and NiMH batteries (because our old expensive LiPo batteries and charger will not work for this season) and it's wasted. Find out for yourself. https://system.na3.netsuite.com/core/me ... c&_xt=.pdf Just to repeat: NiMH batteries DO CONTAIN LITHIUM. So they are not allowed according to this year's rules. Darn!

More evidence that NiMH batteries have lithium: https://www.batterystore.com/content/MS ... e_MSDS.pdf and https://www.batteriesplus.com/image/sds-Empire-NiMH.pdf

Interesting. As usual, this is not the place for official statements or clarifications. That said, I can assure you that we did NOT intend to prohibit NiMH batteries. I'll work on getting the policy updated ASAP to explicitly allow NiMH batteries.

[StormTJ]

Is there any reason to have a timing mechanism on the hovercraft this year?

[antoine_ego]

Is there any reason to have a timing mechanism on the hovercraft this year?

To account for the varying distance. The theory is that you drift slowly for a certain amount of time, then go to full power and speed to the end. Annoyingly, this is extremely difficult to do without transistors or diodes.

[retired1]

I am not sure that I agree with your time control theory. You can control the propulsion speed with a pot or by blocking part of the prop blast or by diverting part of it.