revolving force

[lakemen]

if I have 1700 lbs. of perfectly balanced weight and apply a force of 20 ft.lbs. in torque for 5 sec. whats the ammont of counter torque and time needed to cause the weight to stop spinning. looking at storing energy in a revolving mass based on the yo-yo theory?

thanks

 

[GregLocock]

Um, how about -20 lb.ft for 5 seconds?

Cheers

Greg Locock

 

[lakemen]

tried. broke the torque wrench when it wraped around and locked against the mounts and floor

 

[RobWard]

You just need to counteract the KE that you have imparted to the flywheel. So -20 lb ft for 5 sec, or - 100 lb ft for 1 sec or -1lb ft for 100 seconds etc. (Ignoring friction of course).
I'd personally don't recommend trying to stop rotating masses with hand held tools. If something catches you could be waving goodbye to one hand. (Waving with the other hand, obviously....!) "I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams

 

[prex]

What you need is a brake.
Your rotating mass has stored energy in it and you need to consume it: this is exactly the purpose of brakes. prex

http://www.xcalcs.com

Online tools for structural design

 

[RobWard]

The problem with using a brake is it will dissipate the energy (as heat) not store it, but it all depends on your application as to which route you want to take. "I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams

 

[lakemen]

the force i have stored i want to use at a slow pace like the 1ft.lb. for a hundred sec. I dont need the motor generator for any thing else but a mass to store revolving energy I want to know if i bring this up to 1700 rpm what would be the benifit what could I drive , what could this app. be applyed to. I would like to bring it up to speed with a small gass engine and tap the torque produced by the mass.

 

[desertfox]

Hi lakeman

To calculate the stored energy in your mass, you need to know the "moment of inertia" of that mass about its rotational axis and also the angular velocity of the mass after 5 seconds at this point the stored energy of the flywheel would be :-


K.E=1/2 x I x w^2


where K.E is the kinetic energy
I is the moment of inertia
w is the angular velocity



Further to this to find out how much torque required to stop it you need to consider the change in angular momentum

therefore T x t = I x (w1-w2)

where t = time required to stop the mass

T = Torque

I = moment of inertia

w1 and w2 are the initial and final angular velocities
of the mass (for stopping completely w2 = 0)

so you need to decide in what time you wish to stop the rotation and transpose the formulae to find T ie:-

T = I x (w1-w2)/(t)


hope this helps