Go to Post a Victor is a Victor is a Victor. - Billfred [more]
Home
Go Back   Chief Delphi > ChiefDelphi.com Website > Extra Discussion
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
Reply
 
Thread Tools Rate Thread Display Modes
  #1   Spotlight this post!  
Unread 10-01-2013, 11:52
John's Avatar
John John is offline
Registered User
AKA: John Gillespie
FRC #1153 (Roborebels)
Team Role: Mechanical
 
Join Date: Sep 2011
Rookie Year: 2009
Location: Walpole MA
Posts: 71
John is just really niceJohn is just really niceJohn is just really niceJohn is just really niceJohn is just really nice
Re: pic: The Cow that Jumped over the moon!

Using the method from that website:

Area = #rotors * diameter^2 * pi/4
Area = 4 * 14in^2 * pi/4 = 616 in^2 = 4.28 ft^2

Power will be limited by the battery and main breaker, with a maximum continuous power of:

Power = voltage* current = 12 V * 120 A = 1440 W = 1.93 HP

PL = Power/Area = .452 HP/ft^2

TL = 8.6859 * PL^(-.3107) = 11.12 lb/HP

Thrust = Power * TL = 11.12 lb/HP * 1.93 HP = 21.5 lb

The battery alone is 12 lb. Each CIM is 2.8 lb. If I did the math correctly, I don't think you can fly.
Reply With Quote
  #2   Spotlight this post!  
Unread 10-01-2013, 12:37
JamesCH95's Avatar
JamesCH95 JamesCH95 is offline
Hardcore Dork
AKA: JCH
FRC #0095 (The Grasshoppers)
Team Role: Engineer
 
Join Date: Dec 2004
Rookie Year: 2001
Location: Enfield, NH
Posts: 1,819
JamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond repute
Re: pic: The Cow that Jumped over the moon!

Quote:
Originally Posted by Jim Wilks View Post
6 CIM's all working near full power? You'd trip the main 120A breaker in a few seconds.
Bingo.

Quote:
Originally Posted by nighterfighter View Post
Each CIM wouldn't be experiencing very heavy loads though. The stall current is 133 Amps, and the free current is 2.7 Amps.

While they wouldn't be at free current, they wouldn't be drawing massive amounts of current if they are powering a light-weight rotor, would they?
If the CIM is operating at full power (337W) with, let's assume 0.65 efficiency (max efficiency, anti-conservative, but I'm only making a point) draws about 43A, which can pop each CIM's breaker, and with just 3 (let alone 6) you're running the risk of blowing the main breaker too.

Quote:
Originally Posted by John View Post
Using the method from that website:

Area = #rotors * diameter^2 * pi/4
Area = 4 * 14in^2 * pi/4 = 616 in^2 = 4.28 ft^2

Power will be limited by the battery and main breaker, with a maximum continuous power of:

Power = voltage* current = 12 V * 120 A = 1440 W = 1.93 HP

PL = Power/Area = .452 HP/ft^2

TL = 8.6859 * PL^(-.3107) = 11.12 lb/HP

Thrust = Power * TL = 11.12 lb/HP * 1.93 HP = 21.5 lb

The battery alone is 12 lb. Each CIM is 2.8 lb. If I did the math correctly, I don't think you can fly.
This too.
__________________
Theory is a nice place, I'd like to go there one day, I hear everything works there.

Maturity is knowing you were an idiot, common sense is trying to not be an idiot, wisdom is knowing that you will still be an idiot.
Reply With Quote
  #3   Spotlight this post!  
Unread 10-01-2013, 12:37
artdutra04's Avatar
artdutra04 artdutra04 is offline
VEX Robotics Engineer
AKA: Arthur Dutra IV; NERD #18
FRC #0148 (Robowranglers)
Team Role: Engineer
 
Join Date: Mar 2005
Rookie Year: 2002
Location: Greenville, TX
Posts: 3,078
artdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond repute
Re: pic: The Cow that Jumped over the moon!

Quote:
Originally Posted by JesseK View Post
There's a fundamental design flaw with this, if you continue to use the sheet.

http://dsc.discovery.com/tv-shows/my...p-lift-off.htm

They demonstrated this with miniature helicopters -- the helos could lift themselves in unison when all connected to the same wooden lattice. Yet once they mounted a sheet underneath the lattice, the helos couldn't get off the ground.
Technically, if the surface underneath the bees/mini-helicopters was curvedl, they could use the Coanda Effect for lift.

Quote:
Originally Posted by nighterfighter View Post
Each CIM wouldn't be experiencing very heavy loads though. The stall current is 133 Amps, and the free current is 2.7 Amps.

While they wouldn't be at free current, they wouldn't be drawing massive amounts of current if they are powering a light-weight rotor, would they?
Nope. The mechanical power output is found by multiplying the torque times the rotational speed. For a DC brushed motor, torque and speed are inversely related, thus the output power forms a parabola with a maximum value at the mid-point. A CIM Motor at peak output power will be drawing 67.9 amps.
__________________
Art Dutra IV
Robotics Engineer, VEX Robotics, Inc., a subsidiary of Innovation First International (IFI)
Robowranglers Team 148 | GUS Robotics Team 228 (Alumni) | Rho Beta Epsilon (Alumni) | @arthurdutra

世上无难事,只怕有心人.
Reply With Quote
  #4   Spotlight this post!  
Unread 12-01-2013, 09:38
Camren's Avatar
Camren Camren is offline
Mentor
FRC #3081 (RoBoEaGleS)
Team Role: Mentor
 
Join Date: Mar 2011
Rookie Year: 2011
Location: Minnesota
Posts: 219
Camren is a jewel in the roughCamren is a jewel in the roughCamren is a jewel in the rough
Re: pic: The Cow that Jumped over the moon!

I am fairly sure this is illegal because you blocking the sight of a drivers station and it is not safe at all. plus with disks flying and hitting the wall you better hope that is a stable system or everyone would get to see a cliche ladder tipping scene.
Reply With Quote
Reply


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 19:50.

The Chief Delphi Forums are sponsored by Innovation First International, Inc.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi