Legality of third party fans

[Taylor]

A rookie member and I had a similar discussion just this past weekend.
We came to the conclusion that big, important companies donate lots of gizmos and money to FIRST, and (partially) in return, they get to be the exclusive gizmo of FIRST Robotics.

Yes, the companies are donating their goods and services to a very good cause - they're also very intelligently building a customer base for years to come.

Think of all the collegiate senior projects that use IFI or CTRE or PTC or NI products (for example) we've seen recently that may have otherwise used other components. This means FIRST students have been acclimated to prefer the FIRST suppliers' products, which means that when these young ladies and gentlemen start their own companies, they'll be predisposed to use FIRST suppliers' products, which means the initial donations will have been very worthwhile.

Next time you listen to the radio or watch television, pay attention to the types of commercials played. Dollars to doughnuts, in a single break, you'll only hear/see one commercial from any given type of local business (law firm, auto dealership, florist, etc.). Exclusivity is a huge negotiating tool.

[Joe Johnson]

Originally Posted by Jon Stratis

<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.

[engunneer]

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.

[ratdude747]

Originally Posted by Joe Johnson

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...)

[Alan Anderson]

Originally Posted by Joe Johnson

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.

Originally Posted by ratdude747

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.

[ratdude747]

Originally Posted by Alan Anderson

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.

[Joe Johnson]

Originally Posted by ratdude747

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.

[Jon Stratis]

Originally Posted by Joe Johnson

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.

That would be a good way to clean out the parts closets for a hundred teams or so! And if you build it, maybe you can get your local MC to ride it around during competition!

[FrankJ]

Originally Posted by Joe Johnson

....

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.

[Alan Anderson]

Originally Posted by ratdude747

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.

[SamM]

Could someone with fans from old kits share model/part numbers?

My rookie team would like to buy some larger fans for cooling, but we don't know which ones are legal. We're hoping that 80mm fans were included at some point and are still available somewhere.

[marshall]

This rule is now anachronistic and silly. It should be changed to allow all 12v fan motors provided they meet some reasonable CFM spec. Come on Frank/FRC/GDC people... do the right thing.

Over the years I think we've given away or thrown out 90% of the simple box fans included in the kit so I couldn't give you a part number if I wanted to. I honestly don't think most inspectors could tell you if one came from the kit or not for that matter and I'm reasonably certain there are enough parts from old kits that I could pull out that an inspector would now tell me are illegal...

This is a silly rule.

[ratdude747]

Originally Posted by Alan Anderson

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.

I stand corrected. Didn't think they had enough push.

[FrankJ]

Originally Posted by ratdude747

I stand corrected. Didn't think they had enough push.

According to Archimedes

Give me a place to stand and with a lever I will move the whole world.

So this should be legal on at least one field at worlds.