belt - how to recognise the tight side?

[Lily]

In general, how would you recognize which side of a pulley has Fmax or which has Fmin.

NCEES 2001 problem 516, I got the wrong answer because I considered the F=100 lb as Fmax.

Any quick way to avoid this kind of mistake?

Thanks!

Lily

 

[Capt Worley PE]

Hmmm...No real world experience with a drive belt?

I'm not really sure how to expain it...

 

[Rafa]

I think the problem should state the way the belt is to operate. One problem in the morning session smaple exam (NCESS) ask to calculate the force to hold the weigth at the other end of the rope. Friction force acts between the polley and the belt so in this case, the friction force "helps" to hold the weigth, that means the force nescesary will be less than the weigth. On another similar problem they ask for the force to raise the weigth, in this case you will need a large force to hold the weigth and overcome the friction force. Hope this help. R.

 

[Capt Worley PE]

The drive pulley pulls the belt toward it...that's the tight side.

 

[Sschell]

^just remember... belts can't push...

 

[Rafa]

Hi, how I can get a copy of NCEES 2001 sample exam???, I completed the 2008 sample exam and need to work faster on the afternoon MD problems. Thanks.

 

[Lily]

I got the NCEES 2001 from Amazon,

Thanks for your answers, I will have to see how they apply to this exercise.

Lily

 

[Lily]

ok, so the tight side is not always the side where the belt is moving toward... this means that in the 516 MD NCEES 2001, the friction is helping the band brake...makes sens...

Thanks!

@Rafa: very clear and helpful