Hovercraft B/C

Wen
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Re: Hovercraft B/C

Postby Wen » October 11th, 2016, 2:59 pm

Good to see more discussions. Thanks for the large picture, Chalker. It's a little hard to see what are inside the mesh squares.

Could someone comment on this one?
http://www.pitsco.com/Hover-Craft_I?SKU=59661&
Is it useful (or are the parts useful) for SciOly competition? The Props need to be shielded? It's out of stock so not sure how long it will take to get it.
Do you have a copy of the rules in hand? I'm not trying to be condescending, at all, but you'll definitely want them in hand before making any purchases.

All of the language about battery-powered motors uses the words "may" or "up to," which don't disallow hovercrafts like that one, or some balloon-style ones you may have seen. So, feel free to experiment - it's certainly less complicated (which can lead to more actual testing and experimenting - the whole point of this competition). But, you'll likely want to have them work on some battery powered craft at some point in the season, and leave the rubber fiddling to the Wright Stuff kids :D

Edit: Rule 4.k - "Vehicles must have an electric switch to permit safe starting." I feel like the intent of the rule was obviously meant for battery powered motors and not to outlaw non-electric vehicles, but, unless that's clarified, play it safe and stick with one of the battery powered models instead.
We do intend to change to battery powered motors. I'm curious about the wooden tray instead of styroform tray. Is wood better or worse?

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Re: Hovercraft B/C

Postby chalker » October 11th, 2016, 3:28 pm

What are the "boxes" that the push motor is setting on?
They are circular clips with an adhesive backing kinda like this: http://www.alliedelec.com/images/produc ... 209028.jpg

If you nest them together the right way, it forms a nice tower that is very secure but allows for a bit of rotational adjustment along various axes to provide for some adjustment on the direction the vehicle will go.

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Wen
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Re: Hovercraft B/C

Postby Wen » October 11th, 2016, 3:46 pm

Oh, it's more than that. They charge another $18+ shipping and $10+ tax. That is why I have been hesitating in ordering it. I also looked over the list. What I'm not sure about are Motor, Plastic Propeller, Axial Fan: what kind should I buy if I go buy them myself? Also Mesh Squares, what are they for? Wooden Dowels: Balsa wood? How thick? A design that shows what goes where will be helpful.
Note that the kit comes with a 10 page document that gives step by step instructions on how to build the device (with pictures of each step)!
That is a big plus. When will the kit be available? It says 'ship within 54 days'. I called yesterday and was told that by end of this month (which I suppose is ship-out date). I wish there is something we can get the kids practice on earlier than that. But end of the month is not too bad.

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Re: Hovercraft B/C

Postby sciencekid7 » October 11th, 2016, 10:11 pm

In the rule 4h, it says,"...as long as the expected voltage across any points does not exceed 9.0 V as calculated by [the batteries'] labels." Does this mean that the proctor will look at the battery, and then decide if the circuit is legal, or will the proctor actually take a voltmeter and measure? Also, does the "points" referenced in the rules refer to the terminals of the battery, or can they just be any two points? We are concerned about voltage spikes, so if some were to occur, will the proctor give us violations?

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Re: Hovercraft B/C

Postby windu34 » October 11th, 2016, 10:26 pm

In the rule 4h, it says,"...as long as the expected voltage across any points does not exceed 9.0 V as calculated by [the batteries'] labels." Does this mean that the proctor will look at the battery, and then decide if the circuit is legal, or will the proctor actually take a voltmeter and measure? Also, does the "points" referenced in the rules refer to the terminals of the battery, or can they just be any two points? We are concerned about voltage spikes, so if some were to occur, will the proctor give us violations?
"Across any two points" means that ANYWHERE in the circuit, the voltage MUST be less than 9V. I assume you are thinking about connecting batteries in series to raise the voltage. A good ES will look for that and catch it. You could likely get away with it at some competitions, but why risk it.
"Points" refers to any two points, not necessarily the terminals
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Re: Hovercraft B/C

Postby sciencekid7 » October 11th, 2016, 10:44 pm

I assume you are thinking about connecting batteries in series to raise the voltage. A good ES will look for that and catch it.
No, we are not looking into doing that. As of now, we want to do 7xEneloop or 6xAlkaline. The rule seems to imply that as long as commercial batteries connected in series do not exceed 9V, it should be okay. We are concerned that if the voltage anywhere exceeds 9V even though our batteries are less than 9V, we will be dinged. Alkaline batteries are typically 1.6V when fresh and with no load, but they are labeled 1.5V - so can we use 6x alkaline?

There is a prohibition against integrated circuits, but nothing against other electronic components such as individual potentiometers, diodes, transistors etc. We are looking for confirmation that the latter are okay.

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Re: Hovercraft B/C

Postby LIPX3 » October 12th, 2016, 10:35 am

Can you use two 9v batteries, one for each motor? I've been doing this so far, but reading the rules again, I'm not as sure.

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Re: Hovercraft B/C

Postby windu34 » October 12th, 2016, 10:40 am

Can you use two 9v batteries, one for each motor? I've been doing this so far, but reading the rules again, I'm not as sure.
Yes
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Re: Hovercraft B/C

Postby RJohnson » October 12th, 2016, 11:38 am

I assume you are thinking about connecting batteries in series to raise the voltage. A good ES will look for that and catch it.
No, we are not looking into doing that. As of now, we want to do 7xEneloop or 6xAlkaline. The rule seems to imply that as long as commercial batteries connected in series do not exceed 9V, it should be okay. We are concerned that if the voltage anywhere exceeds 9V even though our batteries are less than 9V, we will be dinged. Alkaline batteries are typically 1.6V when fresh and with no load, but they are labeled 1.5V - so can we use 6x alkaline?

There is a prohibition against integrated circuits, but nothing against other electronic components such as individual potentiometers, diodes, transistors etc. We are looking for confirmation that the latter are okay.
The terminology in the rules is "as labeled." This means that, as far as the rules concern, 6 Alkaline cells in series that are labeled 1.5V but running at 1.6V are still considered only 9V. The rules are designed to protect you against this and the event supervisor from having to check everyone's device with a multimeter.

Good luck!

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Re: Hovercraft B/C

Postby meierfra » October 12th, 2016, 1:50 pm

How is Hovercraft, as an event, supposed to be run? When I saw that it was online scheduled, I first thought you would sign up for a time to run your vehicle and then take the test immediately following, like our State did MagLev last time. But now I just saw the Event Logistics Chart and they recommend signing up for time periods. Is it supposed to be run more like Wind Power, only that you can sign up for a testing period? So, there are no spectators allowed?


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