Hovercraft B/C

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Re: Hovercraft B/C

Postby 0ddrenaline » January 24th, 2017, 3:39 am

Any idea if any ESs (besides the MIT one) used steel tracks? The steel was so frictionless, it destroyed our time score (9/25 sad life), so we got 8th.
He's talking about the base being metal (in addition to the side rails). FYI, the person who ran Hovercraft at MIT is also going to be running it in Div C at Nationals.
That's interesting. At Northridge the track had too much friction, so very few hovercrafts could move. It looks like successful teams should prepare for several track surfaces.

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Re: Hovercraft B/C

Postby chalker » January 24th, 2017, 5:13 am

Any idea if any ESs (besides the MIT one) used steel tracks? The steel was so frictionless, it destroyed our time score (9/25 sad life), so we got 8th.
He's talking about the base being metal (in addition to the side rails). FYI, the person who ran Hovercraft at MIT is also going to be running it in Div C at Nationals.
I assume the track will be similar if not the same for Division B as well?
Not necessarily. There is a different person running Div B. They may or may not decide to share tracks.

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Re: Hovercraft B/C

Postby RJohnson » January 24th, 2017, 5:29 am

Any idea if any ESs (besides the MIT one) used steel tracks? The steel was so frictionless, it destroyed our time score (9/25 sad life), so we got 8th.
He's talking about the base being metal (in addition to the side rails). FYI, the person who ran Hovercraft at MIT is also going to be running it in Div C at Nationals.
That's interesting. At Northridge the track had too much friction, so very few hovercrafts could move. It looks like successful teams should prepare for several track surfaces.
Has anyone seen surfaces other than plywood (sanded and unsanded) or sheet metal? Just curious... Maybe a plastic or linoleum surfaced table? Trying to brainstorm ideas for generating robust data.

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Re: Hovercraft B/C

Postby antoine_ego » January 24th, 2017, 11:40 am


He's talking about the base being metal (in addition to the side rails). FYI, the person who ran Hovercraft at MIT is also going to be running it in Div C at Nationals.
That's interesting. At Northridge the track had too much friction, so very few hovercrafts could move. It looks like successful teams should prepare for several track surfaces.
Has anyone seen surfaces other than plywood (sanded and unsanded) or sheet metal? Just curious... Maybe a plastic or linoleum surfaced table? Trying to brainstorm ideas for generating robust data.
I've seen a linoleum table (school lunch table be used), as well as a lab table. Those offer reasonably little friction.
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Re: Hovercraft B/C

Postby HCCoach » January 24th, 2017, 12:52 pm

Hello,
We are stuck on type of battery to use. Our craft is at 500 gms. The blower fan we got hovers little with 9 V alkaline battery (blower capacity is ~ 900pa). Debating whether to buy Li-Po cells or Nimh battery pack. In either case does anyone have experience wiring it together with a switch or is there a battery holder I should buy? Are these batteries safe for 6th graders to handle?

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Re: Hovercraft B/C

Postby antoine_ego » January 24th, 2017, 1:03 pm

Hello,
We are stuck on type of battery to use. Our craft is at 500 gms. The blower fan we got hovers little with 9 V alkaline battery (blower capacity is ~ 900pa). Debating whether to buy Li-Po cells or Nimh battery pack. In either case does anyone have experience wiring it together with a switch or is there a battery holder I should buy? Are these batteries safe for 6th graders to handle?
Here are what I feel are the pros and cons.

A LiPo battery is significantly lighter than a NiMH. The tradeoff is that you can have a maximum of 7.4V according to the rules, as per the voltage per LiPo cell. The biggest problem however, is that if you handle them incorrectly, they have a tendency to catch on fire. Since you are using them with 6th graders, this may not be a good idea.

A NiMH (what I'm using) is extremely heavy. The one I'm using weighs about the mass of your craft. You can probably find a less heavy one though. The good thing is that they are significantly more durable than LiPos, and you don't run the risk of them catching on fire. I suppose they could, but not sure how that would happen. You also can get a greater maximum voltage, going up to 8.4V. Since you are running big fans, that extra 0.8V might be useful.

As for chargers, if you are planning on buying a big pack, I would recommend a smart charger, which cuts off the current when you reach the desired capacity. You can adjust the amperage depending on whether you need it to charge quickly (which might damage the battery), or slowly and safely. A nice perk is that you can leave the battery to charge overnight and it'll be ready the next morning. The charger I have is this, which works lovely.
Rest in Peace Len Joeris
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[b]2016 Air Trajectory Nationals - 3rd 2018 Hovercraft Nationals - 6th 2018 Mousetrap Nationals - 6th 2018 Nationals - Team 9th Place! 2019 Astronomy Nationals - 3rd! 2019 Nationals - Team 9th Place! [/b]
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Re: Hovercraft B/C

Postby HandsFreeCookieDunk » January 24th, 2017, 2:53 pm

So far, I have been unable to create a device that hovers to my satisfaction after several attempts :? . How do you know when you've reached that point of zero friction? I've dedicated a significant amount of time to putting holes in the skirt, but it still seems like the static friction isn't negligible. Is the solution just more holes or is there something else I'm missing? I'm starting to stress about this event because I'm blowing through batteries really fast trying to get this thing to hover right.

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Re: Hovercraft B/C

Postby HCCoach » January 24th, 2017, 3:15 pm

Hello,
We are stuck on type of battery to use. Our craft is at 500 gms. The blower fan we got hovers little with 9 V alkaline battery (blower capacity is ~ 900pa). Debating whether to buy Li-Po cells or Nimh battery pack. In either case does anyone have experience wiring it together with a switch or is there a battery holder I should buy? Are these batteries safe for 6th graders to handle?
Here are what I feel are the pros and cons.

A LiPo battery is significantly lighter than a NiMH. The tradeoff is that you can have a maximum of 7.4V according to the rules, as per the voltage per LiPo cell. The biggest problem however, is that if you handle them incorrectly, they have a tendency to catch on fire. Since you are using them with 6th graders, this may not be a good idea.

A NiMH (what I'm using) is extremely heavy. The one I'm using weighs about the mass of your craft. You can probably find a less heavy one though. The good thing is that they are significantly more durable than LiPos, and you don't run the risk of them catching on fire. I suppose they could, but not sure how that would happen. You also can get a greater maximum voltage, going up to 8.4V. Since you are running big fans, that extra 0.8V might be useful.

As for chargers, if you are planning on buying a big pack, I would recommend a smart charger, which cuts off the current when you reach the desired capacity. You can adjust the amperage depending on whether you need it to charge quickly (which might damage the battery), or slowly and safely. A nice perk is that you can leave the battery to charge overnight and it'll be ready the next morning. The charger I have is this, which works lovely.
Thanks for the info. Have you wired yours with a switch, in which case wouldnt it need separate leads? I am hesitant to cut off the plastic retainer that typically comes on packs.

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Re: Hovercraft B/C

Postby antoine_ego » January 24th, 2017, 3:26 pm


Thanks for the info. Have you wired yours with a switch, in which case wouldnt it need separate leads? I am hesitant to cut off the plastic retainer that typically comes on packs.
I'm a little confused as to what you are asking. You should never need to cut the plastic retainer. Suppose you had this pack. All you'd need to do is connect the plugs to a switch, which is a simple thing to do.
Rest in Peace Len Joeris
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[b]2016 Air Trajectory Nationals - 3rd 2018 Hovercraft Nationals - 6th 2018 Mousetrap Nationals - 6th 2018 Nationals - Team 9th Place! 2019 Astronomy Nationals - 3rd! 2019 Nationals - Team 9th Place! [/b]
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Re: Hovercraft B/C

Postby Flavorflav » January 25th, 2017, 8:58 am

Thanks for the info. Have you wired yours with a switch, in which case wouldnt it need separate leads? I am hesitant to cut off the plastic retainer that typically comes on packs.
The first time my team did maglev they cut the connectors off, but it isn't a good idea. You can buy unwired Tamiya connectors. I got some on Amazon for about $9 for ten pairs, male and female. This way you can wire the motors and switches to a male and plug it in to the connector that comes on the battery.

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Re: Hovercraft B/C

Postby antoine_ego » January 25th, 2017, 11:26 am

So far, I have been unable to create a device that hovers to my satisfaction after several attempts :? . How do you know when you've reached that point of zero friction? I've dedicated a significant amount of time to putting holes in the skirt, but it still seems like the static friction isn't negligible. Is the solution just more holes or is there something else I'm missing? I'm starting to stress about this event because I'm blowing through batteries really fast trying to get this thing to hover right.
You'll always have friction, it's get a matter of minimizing it. You know when you have a good skirt when you can slide it across a hardwood floor and it glides for a few feet before stopping.
Rest in Peace Len Joeris
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[b]2016 Air Trajectory Nationals - 3rd 2018 Hovercraft Nationals - 6th 2018 Mousetrap Nationals - 6th 2018 Nationals - Team 9th Place! 2019 Astronomy Nationals - 3rd! 2019 Nationals - Team 9th Place! [/b]
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Re: Hovercraft B/C

Postby peter_ni » January 25th, 2017, 9:26 pm

Question about the testing portion; do you think the written exam will be difficult? So far the regional and invitational tests (in NJ at least) have been obscenely easy...

Also, since we couldn't sign up in the 3 minutes that MIT registration was open, was the test anything special?

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Re: Hovercraft B/C

Postby antoine_ego » January 26th, 2017, 4:30 am

Question about the testing portion; do you think the written exam will be difficult? So far the regional and invitational tests (in NJ at least) have been obscenely easy...

Also, since we couldn't sign up in the 3 minutes that MIT registration was open, was the test anything special?
It was more difficult that most tests I've seen. They did a lot of fluid mechanics which I think tripped people up.
Rest in Peace Len Joeris
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[b]2016 Air Trajectory Nationals - 3rd 2018 Hovercraft Nationals - 6th 2018 Mousetrap Nationals - 6th 2018 Nationals - Team 9th Place! 2019 Astronomy Nationals - 3rd! 2019 Nationals - Team 9th Place! [/b]
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Re: Hovercraft B/C

Postby Unome » January 26th, 2017, 5:12 am

Also, since we couldn't sign up in the 3 minutes that MIT registration was open
What do you mean? Registration was open for ~40 minutes.
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Re: Hovercraft B/C

Postby lumosityfan » January 26th, 2017, 11:08 am

Also, since we couldn't sign up in the 3 minutes that MIT registration was open
What do you mean? Registration was open for ~40 minutes.
I think he's talking about overall registration for schools, since it took a very short time for all the slots to be filled up.
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