View Single Post
  Spotlight this post!  
Unread 08-01-2012, 19:12
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 7,995
Ether has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond repute
Re: Official 2012 Motors Models and Specs Thread

Quote:
Originally Posted by Andy Baker View Post
Tested at 12.8 volts
23 ft-lbf max torque at stall
28.6 amps pulled at stall
Estimated 350 watts of power
The numbers don't seem to add up. Using the 84 rpm free speed from the AM web site:

At 12 volts:
stall torque = (12/12.8)*23 = 21.56 ft-lbf

Assuming max output power occurs at half stall torque and half free speed:

half stall torque = 21.56/2 = 10.78 ft-lbf

half free speed = 84/2 = 42 rpm

max watts = 42*10.78*0.142 = 64.3 watts
At 12.8 volts:
free speed = (12.8/12)*84 = 89.6 rpm

Assuming max output power occurs at half stall torque and half free speed:

half free speed = 89.6/2 = 44.8 rpm

half stall torque = 23/2 = 11.5 ft-lbf

max watts = 44.8*11.5*0.142 = 73.2 watts



Last edited by Ether : 08-01-2012 at 22:08. Reason: edited for clarity