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Re: Hovercraft B/C

Posted: January 26th, 2017, 11:34 am
by Unome
lumosityfan wrote:
Unome wrote:
peter_ni wrote: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.
That's what I'm talking about. It was ~2 minutes for 2 teams (though a lot more got 2 teams, I figure a lot of schools dropped) and ~40 minutes until they closed registration.

Re: Hovercraft B/C

Posted: January 26th, 2017, 4:03 pm
by H3LL0
What battery pack and brand r u using? I was using a dynamite speedpack 8.4 v nimh pack that had a voltage capacity of 11 volts on day 1 (which easily powered our fan), but on day 2, that capacity dropped to 9v, which was for some reason not pushing our craft forward.

Re: Hovercraft B/C

Posted: January 26th, 2017, 4:09 pm
by antoine_ego
H3LL0 wrote:What battery pack and brand r u using? I was using a dynamite speedpack 8.4 v nimh pack that had a voltage capacity of 11 volts on day 1 (which easily powered our fan), but on day 2, that capacity dropped to 9v, which was for some reason not pushing our craft forward.
You need to charge the battery. The voltage curve of a NiMH starts off high and then levels out. Charging it should bring it back up. If you charge it and the performance still isn't up to par, you may have too much internal resistance. Simply cycle the battery by discharging to 7V and then fully charging it back up. Be careful not to fully discharge it, as you may reverse the polarity which can permanently damage the battery.

Re: Hovercraft B/C

Posted: January 26th, 2017, 5:27 pm
by andrewwski
11 V is a lot for a 7-cell NiMH. Fully charged cells are typically 1.4-1.45 V. 11V puts it at ~1.57 V/cell. Be careful, that could be dangerous.

Re: Hovercraft B/C

Posted: January 26th, 2017, 5:39 pm
by H3LL0
I did charge after use, but it only went to 9 volts. Also, my charger stops when the battery's been fully charged, and I charged it right out of the box. After charging it went to 11v, and it didn't heat up too much during use either, so I'm pretty sure I didn't damage it. It could be that my voltmeter just sucks, but I'm pretty sure it's something else...

Re: Hovercraft B/C

Posted: January 27th, 2017, 4:04 am
by Luo
Unome wrote:That's what I'm talking about. It was ~2 minutes for 2 teams (though a lot more got 2 teams, I figure a lot of schools dropped) and ~40 minutes until they closed registration.
It is not the case that a lot of schools dropped - we (by which I mean Science Olympiad at MIT) "close" confirmed registration after fewer teams have registered (say, 50) than there are spots in the tournament (see 7th bullet point at http://scioly.mit.edu/tournament-inform ... ies-rules/). We do this because at the time registration opens we do not yet have a complete list of the MIT classrooms we'll be able to use, so we initially accept teams conservatively to avoid overcrowding in case we are allocated fewer classrooms than we want. This year there ended up being 20 schools that brought 2 teams to the tournament, and there were a handful of teams whose registrations we were unfortunately not able to accept because we hit a hard limit on space.

Re: Hovercraft B/C

Posted: January 28th, 2017, 1:17 pm
by geniusjohn5
Will something like this work Hovercraft LIFT and Hovercraft PROPULSION (pushing the hovercraft forward)?
http://www.mouser.com/ProductDetail/Ada ... oCp6fw_wcB

Re: Hovercraft B/C

Posted: January 29th, 2017, 8:22 am
by Ashernoel
At wright state yesterday hovercraft became a trial event. I heard this happened at Cornell as well, but does anybody know why?

Re: Hovercraft B/C

Posted: January 29th, 2017, 8:43 am
by Skink
Some tournaments are having difficulty getting anyone's devices (which have been tested and do work) to move on the surfaces allocated for the activity. The finer points of this are beyond me, but I could see tournaments with team awards throwing it out if this happened there.

Re: Hovercraft B/C

Posted: January 29th, 2017, 10:59 am
by windu34
Ashernoel wrote:At wright state yesterday hovercraft became a trial event. I heard this happened at Cornell as well, but does anybody know why?
The test at cornell was ridiculously hard and did not follow the rules so I think a lot of teams arbitrated