"Compressed Air" vs. "High Pressure Blower"

[Aur0r4]

DAN! Yes it was....sorry I forgot your number.

Saw your bot zip around with those blowers, seemed to work pretty well.

[Jeff Pahl]

I inspected a large number of fan/blower robots during Lunacy, and I agree that the use of a fan or blower in those applications was not "pneumatics". The air was free flowing in those applications.

The deciding point for me is when the air becomes contained somewhere in the system at an increased pressure, be it in an accumulator, shooter barrel, etc. Does the ball just fall into a free-flowing air stream, or is it constrained in a barrel with the blower building pressure behind it? There's a difference between the two. Just too many questions at this point.

I love the idea, and would be very impressed to see it well implemented on a robot. I don't think I could make a call on "legality" without actually seeing a specific implementation.....

[Tristan Lall]

As long as FIRST doesn't pretend that a ducted fan is a traction device,¹ I'm happy. (In all seriousness, the distinction between accumulating pressure and blowing air seems to be a good, practical one.)

¹ I'm not making that up. In 2009, a fan thrusting the robot downward was allegedly a traction device. That was ridiculous.

[DavisDad]

Originally Posted by Jeff Pahl

... I don't think I could make a call on "legality" without actually seeing a specific implementation.....

The concept is simple (implementation not). I can't imagine that this would be considered constrained compressed air. The only constraint is the inertia of the ball when fan creates pressure to move air and ball.

1. The ball is loaded into the barrel and rolls to stops
2. Fan motor is energized to a variable voltage (volts determine exit velocity)
3. After ball leaves cannon, fan motor is de-energized

[Bob Steele]

Originally Posted by Tristan Lall

As long as FIRST doesn't pretend that a ducted fan is a traction device,¹ I'm happy. (In all seriousness, the distinction between accumulating pressure and blowing air seems to be a good, practical one.)

¹ I'm not making that up. In 2009, a fan thrusting the robot downward was allegedly a traction device. That was ridiculous.

Tristan this is an interesting comment... why did you use the fan?

My guess is that it was used to increase the "apparent weight" of the robot which would increase the normal force on the wheels which would increase the friction of the wheels with the surface. Therefore this would increase traction..
hence a traction device.

That being said.. .the battery and every other part on the robot are also traction devices by this definition ..

interesting

[Daniel_LaFleur]

Originally Posted by Bob Steele

Tristan this is an interesting comment... why did you use the fan?

My guess is that it was used to increase the "apparent weight" of the robot which would increase the normal force on the wheels which would increase the friction of the wheels with the surface. Therefore this would increase traction..
hence a traction device.

That being said.. .the battery and every other part on the robot are also traction devices by this definition ..

interesting

Increasing the nominal downward force was, indeed, the reasoning of the rule. Fans / props were allowed that year as long as they did not increase the nominal downward force of the robot (I know, we used propellers horizontally for additional thrust).

As far as 'every other part' on the robot ... all those needed to be within the 120LB max weight (plus battery and bumpers) and thus were already accounted for in the maximum traction attainable.

[Tristan Lall]

Originally Posted by Bob Steele

Tristan this is an interesting comment... why did you use the fan?

My guess is that it was used to increase the "apparent weight" of the robot which would increase the normal force on the wheels which would increase the friction of the wheels with the surface. Therefore this would increase traction..
hence a traction device.

That being said.. .the battery and every other part on the robot are also traction devices by this definition ..

interesting

The fan wasn't mine. Other teams wanted to increase their traction on the slick fibreglass surface. The Q&A ruled against it.

But like you said, if that was a traction device, why wasn't everything with weight or downward momentum also a traction device? (They contribute to the normal force, which determines the traction.) And if the weight limit was considered "accounted for", why couldn't underweight robots use a fan to bring themselves to an equivalent normal force? Note that there was no theoretical limit on momentum (though admittedly there were practical ones).

And from an enforcement point of view, how is a referee supposed to know when a ducted, vectoring fan is exerting a downward force, and when it's just thrusting horizontally or off? Failing that, under what authority would FIRST have asked inspectors to disapprove of that mechanism? It was completely unworkable.

Let's hope it's never an issue again....

[Jeff Pahl]

Originally Posted by Tristan Lall

And from an enforcement point of view, how is a referee supposed to know when a ducted, vectoring fan is exerting a downward force, and when it's just thrusting horizontally or off? Failing that, under what authority would FIRST have asked inspectors to disapprove of that mechanism? It was completely unworkable.

Let's hope it's never an issue again....

Amen to that!!