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Re: Hovercraft B/C

Posted: January 26th, 2017, 11:34 am
by Unome
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
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
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
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

Re: Hovercraft B/C

Posted: January 29th, 2017, 12:48 pm
by mwilsoncrist
Apparently there was an appeal at Wright State, largely due to rules violation of the track(s).

The track for the B event was shortened to less than the 130 cm requirement in the rules, and there was an apparent uphill portion. near the finish line. This after the original tables on which they mounted the rails had a dip, and the first craft that ran got stuck between one of the rails and the table. Due to the issue with the B track, the ES apparently decided to change the C track as well. All of this took place during the first test block. Many of the competitors also had to catch their craft at the end of the track so the craft didn't hit the floor due to the table length. That certainly made for some nervous hovercraft coaches.

When we ran a hovercraft event for an invitational, we used a 15.5-inch-wide by 8-foot-long piece of melamine shelving board (purchased at Lowes) and screwed the metal studs to that. That removed the potential for crafts getting stuck under the rails, and dips in any tables that we laid the track across, particularly since we did not know the layout of the room before the event.

I certainly hope they get the bugs worked out before Nationals. It cost us a higher overall ranking since both our hovercraft teams were in the top 10.

Re: Hovercraft B/C

Posted: January 29th, 2017, 2:17 pm
by sciolycoach
Hello,

I'll share a bit more here, but you are pretty much spot on. I helped with Hovercraft yesterday and the tables we requested were warped (they were plastic banquet tables) in the middle causing cars to go down hill and then uphill and get stuck. Realizing this, during the first time block we *quickly* tried to move the tracks over to the only other tables that were available in the room, and these tables were not long enough for the Div B length OR the Div C length that had been announced. As we were, by this time, *veryquickly* trying to move the tracks over to the new tables and put tables together to adjust we realized the tables, despite looking very similar, were not the same heights due to adjustable legs. It was getting near the end of the first time block by this time so a decision was made to go with a shorter track. Remember, this was an invitational tournament and much was learned for nationals. As my team was coming from such a long ways away it was not feasible to bring a nice homemade setup like others have described for an invitational but I am sure some type of design will be constructed for nationals...in fact discussions were already taking place Saturday afternoon.

I want to give a huge thank you to the team of volunteers who worked hard in a tough situation to try to get everything through and help everyone learn through the process. They did an OUTSTANDING job even when thrown several curve balls that I am sure will get addressed for nationals. Better to happen now than in May!

Re: Hovercraft B/C

Posted: January 29th, 2017, 6:15 pm
by chalker
Hello,

I'll share a bit more here, but you are pretty much spot on. I helped with Hovercraft yesterday and the tables we requested were warped (they were plastic banquet tables) in the middle causing cars to go down hill and then uphill and get stuck. Realizing this, during the first time block we *quickly* tried to move the tracks over to the only other tables that were available in the room, and these tables were not long enough for the Div B length OR the Div C length that had been announced. As we were, by this time, *veryquickly* trying to move the tracks over to the new tables and put tables together to adjust we realized the tables, despite looking very similar, were not the same heights due to adjustable legs. It was getting near the end of the first time block by this time so a decision was made to go with a shorter track. Remember, this was an invitational tournament and much was learned for nationals. As my team was coming from such a long ways away it was not feasible to bring a nice homemade setup like others have described for an invitational but I am sure some type of design will be constructed for nationals...in fact discussions were already taking place Saturday afternoon.

I want to give a huge thank you to the team of volunteers who worked hard in a tough situation to try to get everything through and help everyone learn through the process. They did an OUTSTANDING job even when thrown several curve balls that I am sure will get addressed for nationals. Better to happen now than in May!
Yes, we mostly definitely will have tracks with solid, flat, level bases and the 2x4 side rails pre-affixed to them moving forward for the Ohio State Tournament and WSU National Tournament.

Re: Hovercraft B/C

Posted: January 31st, 2017, 3:53 pm
by giyu123
Hey, guys. Me and my partner built a hovercraft, and it works great, except when we put the shield on (which unfortunately is a requirement). Any ideas on how to reduce shield weight?

Re: Hovercraft B/C

Posted: January 31st, 2017, 7:00 pm
by Elastaro
Hey, guys. Me and my partner built a hovercraft, and it works great, except when we put the shield on (which unfortunately is a requirement). Any ideas on how to reduce shield weight?
For me, fan grills worked out very well (about $5 on Amazon). They do reduce the fan output, but not significantly. I've seen other teams use plastic screen/mesh material, but personally I think fan grills are easier to deal with.