Hovercraft B/C

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Re: Hovercraft B/C

Postby SPP SciO » October 10th, 2016, 11:38 am

Unome wrote: Expanding on the point about "propellers must be shielded;" this rules presumably comes from MagLev. Not sure how long you've been around, but MagLev was basically scrapped due to safety issues. I believe chalker mentioned somewhere that Hovercraft is basically MagLev with the dangerous parts removed.


Oh yeah, for sure, it's a good rule. Even the computer fans with plastic blades are pretty dangerous. If you reach for one in a clumsy manner, you'll nick a finger. I do recall reading a story of gnarly MagLev incident; bleeding students can't make for "good optics" in the world of competitive science.
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Re: Hovercraft B/C

Postby Wen » October 10th, 2016, 12:29 pm

SPP SciO wrote:
Wen wrote: 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.


The motor is just a typical DC motor; the little metal cylinder with a shaft and two leads or wire tabs. Radio Shack sells them individually for $2-3 but if you ask the technology/science teachers at your school, they may just have a whole bin of them sitting around. The plastic propeller is literally nothing more than a twisted piece of plastic; you can buy multi packs online if you want to test out a variety, but they're also not hard to make - cut a strip of some thin rigid plastic, punch a hole through the middle with a hot nail, and if you warm it up over a flame for a few seconds you can twist it into a propeller shape. I believe the axial fan that comes with the kit is a small computer cooling fan. If you have no idea where to salvage one, check the links to DigiKey a few pages back in this thread. We wound up testing a few, and were able to find one that can lift the max weight for under $30 - but a smaller one, for much less than that, will do just fine. Mesh squares are for compliance with rule 4.e - the propellers must be shielded. Keep your eyes peeled and you'll find something lying around suitable for that (a pair of scissors may be needed). The dowel is for compliance with 4.g - 1/4" or more, for triggering the photogates. 1/4" is pretty standard "dowel size" so again, just look around for one, or pop in to the nearest dollar store.

As for how to put it altogether, you could probably reverse engineer it from the Ward's kit picture. Or, better yet, check out some of the videos on YouTube (there were links either in this thread or the Hovercraft thread in General Chat) and you'll see a hovercraft assembled from start to finish.


Thanks for the explanations/suggestions. Thanks to others for input too. I'm ready to get parts myself. It's a shame that I haven't built any of these. Will definitely have fun building them with kids:).

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Re: Hovercraft B/C

Postby chalker » October 10th, 2016, 4:02 pm

retired1 wrote:Does not look exactly like the picture that you posted. The kit contains an axial fan. Note it is not plural. It says nothing about anything else for propulsion, but the picture has a large boxed in area at the rear which probably contains a motor driven prop but is not listed in the kit. Why is there the tall mesh over the axial fan which is only a fraction of that height based on what I think I see in the picture.
For the original post, note that this is a get started "also ran" kit. It will not be seriously competitive at any state level competition. That said, the test is 50% of the final score and the craft is the other half.


Not sure what you mean about not looking like what I posted. It's just another one they built in house using the same parts and appears virtually identical to what I previously posted except for the colors of the zip ties.

Note the parts list says motor and plastic propeller in addition to axial fan. The mesh over the axial fan is to provide shielding for it and the reason it's so tall is that's the easiest way to make the shielding work right.

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Re: Hovercraft B/C

Postby chalker » October 10th, 2016, 4:13 pm

SPP SciO wrote:That's what you'll get for $107*. You pay the premium to have it all packaged together (and presumably get some sort of instruction sheet) but there's a good chance that between school and home, you have a lot of these items anyway, and a trip to a dollar store or hardware store can fill in the rest. As previously stated, this is a great starting point, and students will be able to build a functional, competition-ready hovercraft. Hopefully they'll find ways to improve on it the more they test it.

*Chalker, can you explain how this price point is set? I assume there's some partnership between Ward's and SO Inc., and this is good business for all parties, but, $107?! Frankly it seems like it's $7 worth of stuff and a $100 packaging fee. If you're contractually obligated not to discuss this, I get it, but all of the online kits seem dramatically overpriced.


I'm not involved in the pricing in any way, but I can share some thoughts on this:

1. Nobody should ever pay the list price for a Ward's Sci kit (or really any science / educational material). All the big companies that do things like this set high list prices then provide lots of various discount codes. There's a code printed in the front of the Rules Manual for 12% off. I know there are other codes floating around for larger discounts as well.

2. Wards does have to recoup labor costs and there is also a certain amount of funding returned for Science Olympiad as well.

3. You're significantly underestimating the cost of the materials. The axial fan, which I've given details on before, costs ~$10 alone. The 9V batteries cost ~$2. Altogether there are something like ~60 different pieces that are included in this kit, which includes extras of things like the foam plate and zip ties so you can build different versions of the hovercraft.

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Re: Hovercraft B/C

Postby chalker » October 10th, 2016, 4:43 pm

Wen wrote: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)!

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Re: Hovercraft B/C

Postby retired1 » October 10th, 2016, 5:21 pm

I can not find the previous posts for hovercraft.(before the current threads) Anybody have a link. I may owe Chalker an apology.
OK, so it is not a total of $135, it is with a 12% discount on the kit plus fees = $122.++ It is still a starter kit that will require a lot bigger fan to be competitive with the follow on craft. That plus it is on back order--WEN said 54 days.
I have not seen the SO CD for this. If anybody has one, is it a significant help?? For beginners or experienced builders)

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Re: Hovercraft B/C

Postby chalker » October 11th, 2016, 5:13 am

retired1 wrote:I can not find the previous posts for hovercraft.(before the current threads) Anybody have a link.


Here you go: viewtopic.php?f=4&t=9204&hilit=hovercraft&start=75#p297165

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Re: Hovercraft B/C

Postby retired1 » October 11th, 2016, 5:51 am

chalker wrote:
retired1 wrote:Does not look exactly like the picture that you posted. The kit contains an axial fan. Note it is not plural. It says nothing about anything else for propulsion, but the picture has a large boxed in area at the rear which probably contains a motor driven prop but is not listed in the kit. Why is there the tall mesh over the axial fan which is only a fraction of that height based on what I think I see in the picture.
For the original post, note that this is a get started "also ran" kit. It will not be seriously competitive at any state level competition. That said, the test is 50% of the final score and the craft is the other half.


Not sure what you mean about not looking like what I posted. It's just another one they built in house using the same parts and appears virtually identical to what I previously posted except for the colors of the zip ties.

OK, A formal apology. Poor memory. Can I blame it on a different angle?

What are the "boxes" that the push motor is setting on?

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Re: Hovercraft B/C

Postby Wen » October 11th, 2016, 2:31 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.

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Re: Hovercraft B/C

Postby SPP SciO » October 11th, 2016, 2:39 pm

Wen wrote: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.
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Re: Hovercraft B/C

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

SPP SciO wrote:
Wen wrote: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

retired1 wrote: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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Re: Hovercraft B/C

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

chalker wrote:
Wen wrote: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

sciencekid7 wrote: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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