Can anyone please point me in the right direction to calculate force in this situation?

[jmonica]

Hi, I'm working on a project and well, given my limited mental capacity, I'm not sure how to calculate the specifications of one of the parts I need and I am hoping that someone can at least give me a hint as to how I am going to figure this out.I promise I will try to be as brief as possible as I'm fairly sure this will be elementary to a lot of the smart people on this board.

I need to calculate the amount of force it will take to open a valve on a bottle so that I can calculate the torque rating of the electric motor I will need. It's a 360 degree valve similar to turning on a water spigot outside a house.

I do not know how to calculate the amount of force or torque it will take to turn the valve or open and close it. In fact I am not even sure if I am at the math phase of this problem yet as I do not know if there's perhaps a measurement tool that can be used to measure something like this or not much less what it would be called, so as you can see, I am lost. Which only makes my desire and motivation to figure this out and complete this "make" even more. Thank You in advance for your time. Stay Healthy everyone!

 

[topsquark]

The wheel and axle have a certain friction force between them, just like any other two surfaces. You will need to find out what these are.

As for the rest [math]\vec{ \tau } = \vec{F} \times \vec{r}[/math]. (See diagram below.) In this case the force and moment arm are at right angles so [math]\tau = Fr[/math].

In order to make the wheel turn you have to overcome static friction, so [math]\tau _s = f_s r[/math]. To keep it moving with a constant angular acceleration you need to apply a torque of [math]\tau _k = f_k r[/math], where [math]f_{s,k}[/math] are the static and kinetic friction forces.

-Dan

 

[LCKurtz]

This sounds to me like a "hands on" problem. Put a torque wrench on it and measure it.