Hovercraft B/C

Crtomir
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Re: Hovercraft B/C

Postby Crtomir » October 1st, 2017, 1:05 pm


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.

THANKS!!!

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Re: Hovercraft B/C

Postby cuber » October 1st, 2017, 6:04 pm

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.
hmm. I don't notice anything baring a spring based timer. Perhaps you could rig an egg timer device to flip the propulsion switch?

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Re: Hovercraft B/C

Postby antoine_ego » October 2nd, 2017, 2:47 am

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.
hmm. I don't notice anything baring a spring based timer. Perhaps you could rig an egg timer device to flip the propulsion switch?
The problem is that it stores potential energy, and all energy must come from the batteries. You'd need to figure out some way to wind it up as you go down the track.
Rest in Peace Len Joeris
[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 cheese » October 2nd, 2017, 2:10 pm

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.

THANKS!!!
Yeah my heart just dropped.
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Re: Hovercraft B/C

Postby glmohan2002 » October 5th, 2017, 7:23 pm

I am new here, first time coaching Hovercraft for Event B.
Recently I purchased a video of Hovercraft 2018 from Soinc store. I observed that some teams are using two batteries. Though I am not sure about the voltage label of those batteries in the video but I got some questions that I want to get it clarified.

Below text as described in the construction rule
"Commercial batteries, including rechargeables, not exceeding 9.0 V as labeled, may be used to energize the motors on the vehicle. Multiple batteries may be connected together as long as the expected voltage across any points does not exceed 9.0 V as calculated by their labels. "

My question is:
- Is it allowed to use two 9V batteries in parallel connection to power the motors ? Here voltage across the circuit would be still 9.0v
- Is it allowed to use separate 9V batteries one for lift and one for thrust motor ? Here there will be two separate circuits.

Thank you !!!

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Re: Hovercraft B/C

Postby Adi1008 » October 5th, 2017, 7:50 pm

I am new here, first time coaching Hovercraft for Event B.
Recently I purchased a video of Hovercraft 2018 from Soinc store. I observed that some teams are using two batteries. Though I am not sure about the voltage label of those batteries in the video but I got some questions that I want to get it clarified.

Below text as described in the construction rule
"Commercial batteries, including rechargeables, not exceeding 9.0 V as labeled, may be used to energize the motors on the vehicle. Multiple batteries may be connected together as long as the expected voltage across any points does not exceed 9.0 V as calculated by their labels. "

My question is:
- Is it allowed to use two 9V batteries in parallel connection to power the motors ? Here voltage across the circuit would be still 9.0v
- Is it allowed to use separate 9V batteries one for lift and one for thrust motor ? Here there will be two separate circuits.

Thank you !!!
I think both are fine
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Re: Hovercraft B/C

Postby DrDaveV » October 8th, 2017, 7:45 pm

Another new coach here.

What are typical final masses of peoples vehicles?

David

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Re: Hovercraft B/C

Postby chalker » October 9th, 2017, 8:30 pm

Another new coach here.

What are typical final masses of peoples vehicles?

David
That really depends on the level of competition. At Nationals last year there were lots of vehicles with max mass (2kg). At a typical regional, few had max mass. Note however that the rules this year don't care about the mass of the vehicle itself.

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Re: Hovercraft B/C

Postby black » October 11th, 2017, 1:36 pm


hmm. I don't notice anything baring a spring based timer. Perhaps you could rig an egg timer device to flip the propulsion switch?
The problem is that it stores potential energy, and all energy must come from the batteries.
All the rules say is that "The vehicle must not have any other energy sources [aside from batteries]". But what exactly qualifies as an energy source?

If the energy isn't being used to propel or levitate the vehicle (like with an egg timer), does it still count? If so, couldn't you argue that any mass counts as an energy source?

Seems like this warrants a clarification, since the exact definition of "energy source" determines whether or not any sort of spring-based mechanical components are allowed.

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Re: Hovercraft B/C

Postby antoine_ego » October 11th, 2017, 1:58 pm


hmm. I don't notice anything baring a spring based timer. Perhaps you could rig an egg timer device to flip the propulsion switch?
The problem is that it stores potential energy, and all energy must come from the batteries.
All the rules say is that "The vehicle must not have any other energy sources [aside from batteries]". But what exactly qualifies as an energy source?

If the energy isn't being used to propel or levitate the vehicle (like with an egg timer), does it still count? If so, couldn't you argue that any mass counts as an energy source?

Seems like this warrants a clarification, since the exact definition of "energy source" determines whether or not any sort of spring-based mechanical components are allowed.
As usual, my opinion, but if you wind up a spring beforehand, you are giving the vehicle additional potential energy before the run that doesn't come from the batteries. I'm not sure how mass is an energy source, because you aren't extracting energy from the mass itself.

The real question is, when it says batteries, could you use gravitational potential energy from the battery? ;)
Rest in Peace Len Joeris
[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]
Acton-Boxborough Regional High School Captain 17-19


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