Hovercraft

[dtengineering]

Originally Posted by smartkid

I personally also brought that idea to the table, before the idea of a hovercraft. But after reading R06 a few times a vacuum under the bot would be considered a "traction device" would it not?

I'd tend to think of it as a "normal force increasing device". Technically the vacuum would not provide any traction... it would merely increase the force acting on the wheels allowing them to provide enhanced traction.

I believe the Q&A needs to answer this one, though,

Jason

[bduddy]

F1 buffs will get this one.





EDIT: Hmm, where did the picture go? Err, anyway...
en.wikipedia.org/wiki/Brabham_BT46B

[gregscott]

Originally Posted by bduddy

F1 buffs will get this one.





EDIT: Hmm, where did the picture go? Err, anyway...
en.wikipedia.org/wiki/Brabham_BT46B

Actually, the first to use the fan concept was Jim Hall with his Chaparral 2J in 1970. Jim was a great innovator and most of the aerodynamic ideas used in racing today originate with him. His most successful from a winning standpoint was the 2E which used a moveable wing to provide downforce in corners but which could be leveled on the straights to provide minimal drag.

As usually happens, his ideas were proved so effective that they were outlawed after 1 or 2 seasons.

One of the things that happens in racing is that if you come up with a really brilliant idea, someone will try to ban it in the name of "level competition". As you write the rules tighter and tighter, there becomes less and less possibility for really great leaps of creativity...just think of NASCAR.

I worry that FIRST is going in that direction.

[smartkid]

Originally Posted by dtengineering

I'd tend to think of it as a "normal force increasing device". Technically the vacuum would not provide any traction... it would merely increase the force acting on the wheels allowing them to provide enhanced traction.

I like that logic. Let me ask, to get a good vacuum would you need to touch the surface of the playing field or would you be able to make a duct that comes very close to the surface but does not touch?

[Racer26]

I would think touching the surface would be required to gain significant benefit from it, however, it might just be a use for all those banebots/FP motors my team never finds a use for, if the Q/A determines its allowed (which i think is unlikely)

[smartkid]

When does the Q&A open anyway?

[Bongle]

To finalize my discussion with myself about fans to augment your own acceleration, I found one designed for a maximum of 300 watts, which is in the range that a FRC robot can legally put out. It puts out 4 newtons while spinning at some mind-boggling RPMs. It would sound really cool spooling up.

So you'd have a drive motor running continuously at near-maximum output for 4 newtons of forward force. Maybe I'm not looking in the right places (after all, R/C fans are designed for applications where they are moving through air quickly), but that seems like it'd be too little force for a hovercraft to be effective.

You could build very light if you wanted maximum acceleration, but you're still hauling a big trailer behind you and you'd lose pushing matches because your absolute pushing power would be lower (you'd lose your wheel traction in proportion to your weight loss).

A maximum-weight robot would get a 15% acceleration boost by using this little fan, assuming it would be a legal thing to do, you could rig a motor and gearbox to the fan, and the constant 300 watt drain wouldn't greatly impair other robot actions.

Here is the fan: http://www.modelflight.com.au/rc_mod..._micro_fan.htm

[Beakerone]

Definitely an interesting idea, but i was wondering how you were going to get past (R18) which defines the height that the trailer must be attached to the robot - 2 and 13/16ths to the center of the Trailer Hitch from the floor., doesn't sound like it can be "floating" at different heights... which I think would occur, also they mention that it has to be rigidly attached to a fixed locations.

[cj.reeves]

is the coeficient of friction independent of surface area under the present conditions

[n_ambrogi013]

i think that someone already discussed earlier in this thread using a fan to generate downforce, effectively increasing the normal force on the wheels.

my question is, how would you calculate the amount of suction force that a fan can generate against a solid surface like the playing field? using drive motors to power a fan is really only worth it if there is a significant traction increase.

also, is it legal to generate downforce with a fan?

[scirobotics]

it is illigal to genarate downforce with a fan

[DonRotolo]

Originally Posted by Prontopwnage

hey you guys, your thinking to hard...
You could do the opposite and get more grip... Like that model car that can go on the ceiling! I don't know if that would work... What do you guys think?

I think you're not thinking hard enough, since you asked.

Originally Posted by cj.reeves

is the coeficient of friction independent of surface area under the present conditions

Yes, as coefficient of friction is a property of the interaction of two surfaces. But I think you want to know about pushing power, which theoretically remains the same because a larger area means a smaller force per unit area, but in reality a larger surface contact area means a very slightly increased pushing power.

Originally Posted by scirobotics

it is illigal to genarate downforce with a fan

Can you quote a rule please? Or is this speculation?

[Mike Betts]

Originally Posted by scirobotics

it is illigal to genarate downforce with a fan

Would you mind quoting the specific rule?

[OScubed]

It's pretty clear that anything that provides additional traction is ruled out by R06:

<R06>
ROBOTs must use ROVER WHEELS (as supplied in the 2009 Kit Of Parts and/or their equivalent as provided by the supplying vendor) to provide traction between the ROBOT and the ARENA. Any number of ROVER WHEELS may be used. The ROVER WHEELS must be used in a “normal” orientation (i.e. with the tread of the wheel in contact with the ground, with the axis of rotation parallel to the ground and penetrating the wheel hub). No other forms of traction devices (wheels, tracks, legs, or other devices intended to provide traction) are permitted.
The surface tread of the ROVER WHEELS may not be modified except through normal wear-and-tear. Specifically, the addition of cleats, studs, carved treads, alterations to the wheel profile, high-traction surface treatments, adhesive coatings, abrasive materials, and/or other attachments are prohibited. The intent of this rule is that the ROVER WHEELS be used in as close to their “out of the box” condition as possible, to provide the intended low-friction dynamic performance during the game

Note the OR OTHER DEVICES INTENDED TO PROVIDE TRACTION.

[T3H_K3YM45T3R]

I don't think that a downward force would be "creating traction" but be closer to "increasing" traction, which I guess depending on how you look at it could "create" traction.