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Unread 16-02-2016, 11:56
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Re: Legality of third party fans

Quote:
Originally Posted by Jon Stratis View Post
<snip>
That said, when inspecting the robot, I'm not going to be closely examining every fan that's attached to a speed controller.
<snip>
Limiting the discussion just to Victor fans for the moment, the way I read the rules you don't have to have these fans attached to a speed controller at all, they just have to have been attached to speed controller that was in a FRC KOP in some year (i.e. they have to be Victor Fans).

The really attractive thing about this rule (IF I AM CORRECT about not having to use them for their original purpose) is that they can be used in unlimited numbers and they can be powered directly via a 20A breaker per Table 4-2 in R48. That is, you don't have to be able to turn them off when you are disabled. Turn on the main breaker and your fans go on.

The way I read this, you could make a hovercraft with hundreds of these guys if you wanted to as long as you powered them all via the 20A breaker.

Am I wrong?

Dr. Joe J.
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Last edited by Joe Johnson : 16-02-2016 at 11:58.
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Unread 16-02-2016, 12:56
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Re: Legality of third party fans

Joe, until you run out of amps, and barring the other physics limitations of making hovercrafts that are FRC legal, I agree with your rule interpretation here.

Also, in terms of Q&A, Q844 is useful to this discussion.
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Unread 16-02-2016, 17:42
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Re: Legality of third party fans

Quote:
Originally Posted by Joe Johnson View Post
Limiting the discussion just to Victor fans for the moment, the way I read the rules you don't have to have these fans attached to a speed controller at all, they just have to have been attached to speed controller that was in a FRC KOP in some year (i.e. they have to be Victor Fans).

The really attractive thing about this rule (IF I AM CORRECT about not having to use them for their original purpose) is that they can be used in unlimited numbers and they can be powered directly via a 20A breaker per Table 4-2 in R48. That is, you don't have to be able to turn them off when you are disabled. Turn on the main breaker and your fans go on.

The way I read this, you could make a hovercraft with hundreds of these guys if you wanted to as long as you powered them all via the 20A breaker.

Am I wrong?

Dr. Joe J.
Physics says no, since one fan (@ 12VDC) can't lift its own weight, any number together won't be able to lift their own weight, let alone the rest of the bot.

Rules wise, if you spliced it correctly and took care to avoid potential pinch points, it would *probably* be legal, although as propulsion devices, one might need to hook them to some sort of motor control (spike, victor, talon, etc.) to meet the intent of the rules (meaning the GDC would be likely to change the rules to bar such if one tried it).

(I know you were probably joking...)
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Last edited by ratdude747 : 16-02-2016 at 17:46.
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Unread 17-02-2016, 00:55
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Re: Legality of third party fans

Quote:
Originally Posted by Joe Johnson View Post
The way I read this, you could make a hovercraft with hundreds of these guys if you wanted to as long as you powered them all via the 20A breaker.
Quote:
Originally Posted by ratdude747 View Post
Physics says no, since one fan (@ 12VDC) can't lift its own weight, any number together won't be able to lift their own weight, let alone the rest of the bot.
A hovercraft doesn't lift its weight using thrust from the fan(s). It creates a confined air cushion on which it floats. A vacuum cleaner can't lift itself with the reaction force from its exhaust, but people regularly make hovercraft using them.
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Unread 17-02-2016, 05:26
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Re: Legality of third party fans

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Originally Posted by Alan Anderson View Post
A hovercraft doesn't lift its weight using thrust from the fan(s). It creates a confined air cushion on which it floats. A vacuum cleaner can't lift itself with the reaction force from its exhaust, but people regularly make hovercraft using them.
Yes, but the issue still stands. Even with a proper skirt, I don't think these fans could generate enough air pressure to sustain a cushion under their own weight. All they are meant to do is provide some cooling breeze... the fan shrouds are too loose and the motors too wimpy. Vacuum cleaners are meant to flow a lot more air; they're more or less hovercrafts in reverse. Hence why they can be made into hovercrafts.
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Unread 17-02-2016, 09:49
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Re: Legality of third party fans

Quote:
Originally Posted by ratdude747 View Post
Yes, but the issue still stands. Even with a proper skirt, I don't think these fans could generate enough air pressure to sustain a cushion under their own weight. All they are meant to do is provide some cooling breeze... the fan shrouds are too loose and the motors too wimpy. Vacuum cleaners are meant to flow a lot more air; they're more or less hovercrafts in reverse. Hence why they can be made into hovercrafts.
So maybe you have to put these fans in series to get enough pressure to provide the air cushion you'd need to be a hovercraft... ...at some point someone is going to say, "challenge accepted" and actually try to build this thing just because...

...don't make me do this...

Dr. Joe J.
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Unread 17-02-2016, 12:23
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Re: Legality of third party fans

Quote:
Originally Posted by ratdude747 View Post
Even with a proper skirt, I don't think these fans could generate enough air pressure to sustain a cushion under their own weight.
A couple of TechnoKats students did it about five years ago. They used a piece of styrofoam (from a modem box) as a rigid skirt with four tall Victor fans embedded in the flat top. It floated across the concrete floor just fine. It couldn't carry a battery, though.
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Unread 17-02-2016, 11:13
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Re: Legality of third party fans

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Originally Posted by Joe Johnson View Post
....

Am I wrong?

Dr. Joe J.
I would say from a power distribution perspective (R48) you are correct. If the fans caused any significant robot movement, then R9 Robot safety could be applied.
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Unread 15-02-2016, 08:04
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Re: Legality of third party fans

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Originally Posted by cantdecide View Post
just as replacements for Talon SR fans
If it looks like a duck, and quacks like a duck, it must be a duck.

If it doesn't look like a duck, then you've got some 'splainin to do.

That said, your RI may not look closely enough to see if it looks like a duck vs a goose.

Last edited by rich2202 : 15-02-2016 at 08:06.
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