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-   -   For those who are skeptical about propellers - Team 2526 (http://www.chiefdelphi.com/forums/showthread.php?t=73374)

MrForbes 02-02-2009 15:15

Re: For those who are skeptical about propellers - Team 2526
 
There's a rule about the wheels being perpendicular to the floor...I don't know about any rule saying they can't steer.

Cyberphil 02-02-2009 16:09

Re: For those who are skeptical about propellers - Team 2526
 
ok, thank you. I was just a little confused.

JGecko146 02-02-2009 16:13

Re: For those who are skeptical about propellers - Team 2526
 
Zrop,

It's not your design we're bashing. The design is really cool. It's that you seem to blow people off with a flippant comment every time someone mentions safety. Everyone wants to have a blast at FIRST but we also want to go home to our families intact. Therefore safety is huge. It especially concerns those of us who know things can go wrong even when you are being safe. That's why "trusting a robot" is a scary thing. I've been in and around FIRST for 13 years now and I still wouldn't "trust a robot" when it comes to my own personal safety. Just think about it.

Woodworker88 02-02-2009 17:41

Re: For those who are skeptical about propellers - Team 2526
 
Quote:

Originally Posted by Wayne Doenges (Post 812715)
Have you ever been to a competition? After each match you will see various parts from the robots on the floor. What if a bolt or nut was to be flipped into your props.Even if they didn't damage your props where does the part go after hitting the props.

On military aircraft carriers, twice a day or more all members of the crew stop all operations to perform a FOD (Foreign Object Disposal) walk, in which they walk shoulder to shoulder across the flight deck looking for any foreign object as small as 1/8" in diameter. This is to prevent the disasterous consequences that could result if one of these objects were sucked into a jet intake or blown around by jet exhaust or prop wash. Keep this in mind as you work on your systems.

Robert103 02-02-2009 17:51

Re: For those who are skeptical about propellers - Team 2526
 
I think this is a good idea, but i have one question, won't using propellers make stopping harder?

zrop 02-02-2009 18:41

Re: For those who are skeptical about propellers - Team 2526
 
Quote:

Originally Posted by Robert103 (Post 812964)
I think this is a good idea, but i have one question, won't using propellers make stopping harder?

Not if they quickly pivot 360 degrees ;D

Robert103 02-02-2009 18:45

Re: For those who are skeptical about propellers - Team 2526
 
Nice :D

Cyberphil 02-02-2009 19:42

Re: For those who are skeptical about propellers - Team 2526
 
But how will they rotate quickly if they move with the steering of the wheels?

Molten 02-02-2009 22:32

Re: For those who are skeptical about propellers - Team 2526
 
Quote:

Originally Posted by zrop (Post 812994)
Not if they quickly pivot 360 degrees ;D

Look up rotational inertia. It would seem the laws of physics do not agree with you on this stopping method. Good luck on trying to find a different way of stopping.

Andy L 02-02-2009 22:41

Re: For those who are skeptical about propellers - Team 2526
 
Quote:

Originally Posted by zrop (Post 812994)
Not if they quickly pivot 360 degrees ;D

Rotational inertia. As said before the props aren't intended for anything more than spinning and moving an R/C plane. The vibration from the robot is already more forces than intended, let alone the sudden accelerations from crashes, and now rotational inertia. You should really start rethinking some of these issues. You're making it seem like this is all a joke and you're just shrugging off every suggestion. I think most people reading this thread have the same mindset that that's what you're doing with every single one of our posts.

Woody1458 02-02-2009 22:48

Re: For those who are skeptical about propellers - Team 2526
 
Quote:

Originally Posted by Andy L (Post 813143)
Rotational inertia.

If you have no experience with this force (i didn't until last year) spin a wheel on a rod then try to rotate it like you would the props. You get very interesting results

zrop 03-02-2009 12:22

Re: For those who are skeptical about propellers - Team 2526
 
Yeah I'm really concerned about the gyroscopical effects of the props. But hey, I've seen videos of hovercrafts using rotating prop bases, so i think it's feasable. We're going to figure out controlling this stuff this week, so we'll get back on the results. XD

zrop 03-02-2009 12:24

Re: For those who are skeptical about propellers - Team 2526
 
Quote:

Originally Posted by Andy L (Post 813143)
Rotational inertia. As said before the props aren't intended for anything more than spinning and moving an R/C plane. The vibration from the robot is already more forces than intended, let alone the sudden accelerations from crashes, and now rotational inertia. You should really start rethinking some of these issues. You're making it seem like this is all a joke and you're just shrugging off every suggestion. I think most people reading this thread have the same mindset that that's what you're doing with every single one of our posts.

Alternatively, the motors could be thrown in reverse. The problem with that though is that the leading edge of the props would become on the wrong side, greatly decreasing thrust.

Al Skierkiewicz 03-02-2009 12:54

Re: For those who are skeptical about propellers - Team 2526
 
Quote:

Originally Posted by zrop (Post 813396)
Alternatively, the motors could be thrown in reverse. The problem with that though is that the leading edge of the props would become on the wrong side, greatly decreasing thrust.

If you are using the Jaguar I would recommend you use the limit switch function to prevent a change in direction. If using a Victor, install a line in software to prevent counter rotation.

David Brinza 03-02-2009 12:57

Re: For those who are skeptical about propellers - Team 2526
 
I hope you appreciate that the comments and concerns about the safety of your propellers is HELP from the CD community. I know several teams have given this approach serious consideration (including our team).

Team 980 chose an alternative drive concept, not because of safety concerns with fans, but for performance needs to support our game strategy. We felt we could contain a failed propeller and avoid having debris getting sucked in and becoming a dangerous projectile by using a "ducted fan" approach with steel mesh over the ends. I don't think your robot can detect a problem with your props and react fast enough to insure no shrapnel will be produced. It's better to have a design which is not going to allow anything dangerous to escape. With the ducted fan, you'll get better thrust performance as well.

I look forward to seeing videos of your robot on the move!


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