Hovercraft B/C

[Adi1008]

For the speed changing is it posible to use a potentiometer

Yes, using a potentiometer is okay, as handsfreecookiedunk said.

[retired1]

You need to make sure that it is a properly sized "pot" Also beware of DC voltage controllers as everyone that I saw had a tiny "IC" in it.

[bhavjain]

Hey Guys,

Just wondering which specific fan (a link would help!) would be sufficient to be used on a 2kg hovercraft. Not able to find one... Looking at past threads, I've come across these options:

1. http://www.digikey.com/product-search/e ... 70-1126-ND
2. http://www.digikey.com/product-detail/e ... ND/2560506
3. http://www.digikey.com/product-detail/e ... ND/4840565

Also, aren't these are brushless? If so, which of these is allowed?

Thanks.

These fans do have brushless motors. There was a rule clarification that says you are allowed to use brushless motors if they are in a computer fan, https://www.soinc.org/official_rules_clarif . The first fan you linked would not hover. 2 kg * 9.8 m/s^2 / (0.15 m * 0.25 m) = 522.666667 pascals, and that times 4/3 equals 696.888889 pascals (The fan is 12v, but you can only use 9v batteries or less.) If you had a perfect design, you would need a 12v fan with 697 pascals of static pressure. The second fan probably wouldn't hover, as it would have an output of about 764.25 pascals of static pressure with a 9v battery, which is pretty close to 697 pascals with a perfect design. The third fan probably would hover, as it would output about 975 pascals of static pressure with a 9v battery.

Just to clarify, is the 3rd fan legal, and are there much better options for a fan with a goal of lifting 2kg?

Also, which fan is recommended as a propeller fan to propel a 2kg hovercraft?

[55555]

So are lead acid batteries allowed? I didn't see anything in the hovercraft rules about it, although they're not allowed in other build events. Apparently these batteries are lead acid and I want to use them. https://www.amazon.com/EBL%C2%AE-Batter ... nt-20?th=1

[retired1]

The adv clearly states that hey are lithium ion. so they are legal.
I will question the claim of 9 volts as lithium batteries are 3.7v per cell, 2 cells would be 7.4 V. They can be overcharged, so the seller is taking certain liberties in my opinion. It will not maintain the over voltage very long. Probably no big deal for your lift motor, but a problem for the push motor as V = speed (RPM)

[bhavjain]

The adv clearly states that hey are lithium ion. so they are legal.
I will question the claim of 9 volts as lithium batteries are 3.7v per cell, 2 cells would be 7.4 V. They can be overcharged, so the seller is taking certain liberties in my opinion. It will not maintain the over voltage very long. Probably no big deal for your lift motor, but a problem for the push motor as V = speed (RPM)

What push motor do you recommend for a 2kg hovercraft? I'm using http://www.digikey.com/product-search/e ... ageSize=25 for a lift motor, but no idea what to use for a push motor...

[55555]

Seems I was mislead by another website that said they used some kind of gel electrolyte that was considered lead acid :/ Yea, reviews say it starts out at about 8.4V and goes down to 7V. Are Li-ion and Li-polymer the same thing? I was thinking about using Lipos but I don't really feel like spending too much money and having to buy a charger too. Also, a question about fans, is voltage(rpm) directly related to static pressure of a fan? So if I give half of the fan's rated voltage, will it generate half the pressure?

[retired1]

Lithium ion and Lithium poly are fairly similar. Purists would know the difference. I think that it has to do with how fast that they can give up their electrical current. That should not be a problem here.
Yes, half of the fan rated voltage would give the fan half of the rpm and thus the static pressure. It is NOT exact, but it is close enough if you add a tiny bit to the rating to be safe if you are calling it close.
The hovercraft leaking air in several places will destroy the fan's capability. I am not talking about the designed air flow out of the bottom of the craft.
A well placed piece of duct tape took an poor craft to a fairly nice one.

[bhavjain]

Still need help with a propeller motor for a 2kg hovercraft...

[Sean_Sylvester1]

It's not neccesarily the fan, the skirt makes a huge difference. I went from .8kg to 1.5 kg with my redesigned skirt