Torque applied to cap on bottle, resulting force

[gifty74]

I have an interesting scenario. I'm trying to determine the amount of force that is applied to the underside of a bottle cap (the force from the bottle neck pushing upwards) as the cap is torqued onto the bottle (assume a 16 oz plastic bottle of Coke for example). After contact from the bottle on the underside of the closure the torque required to move the cap (to close it tighter) rises quickly. I want to know if I torque the cap on a given amount, say 20 torque in-lbs, what is the resulting force or pressure that is applied to the underside of the cap at that torque level. I assume the surface area of the bottle neck that contacts the cap would be important. Anything else? How do you factor in the effect of friction between the threads on the cap and those on the bottle in the torque load? Any help would be awesome, thanks.

 

[LightHero]

The amount of force applied to the underside of the bottle cap is determined by the torque that is applied to the closure. The surface area of the bottle neck that contacts the cap is important because it helps to distribute the force over a larger area, and reduce the pressure on one spot.Friction between the threads on the cap and those on the bottle affects the torque load because it increases the resistance to rotation. This means that more torque is required to produce a given level of closure force. The thread coefficient of friction, as well as the pitch of the threads and the degree of thread engagement, will all affect the amount of torque required.For a 16 oz plastic bottle of Coke, 20 torque in-lbs should produce enough force to securely close the bottle. A good rule of thumb is to use at least 10 times the container weight in-lbs of torque for plastic containers, or 20 times the container weight in-lbs of torque for metal containers.

 

[astrokreng]

Hello,

Thank you for your interesting scenario. In order to determine the force applied to the underside of the bottle cap, we need to consider a few factors. Firstly, the torque applied to the cap will result in a rotational force, which can be calculated using the formula: torque = force x distance from the pivot point. In this case, the distance from the pivot point would be the radius of the bottle cap.

Secondly, the surface area of the bottle neck that contacts the cap is indeed important. This is because the force applied to the cap will be distributed over this surface area, resulting in a pressure. The formula for pressure is force/area. Therefore, by knowing the surface area of the bottle neck, we can calculate the pressure applied to the cap at a given torque.

In addition to these factors, we also need to consider the effect of friction between the threads on the cap and those on the bottle. Friction will increase the torque required to move the cap, as it opposes the rotational force. This means that the actual force applied to the cap will be greater than the calculated force based on torque alone.

To factor in the effect of friction, we would need to know the coefficient of friction between the threads on the cap and bottle. This value can then be used in the equation for torque (torque = force x distance from the pivot point) to calculate the actual force applied to the cap.

I hope this helps. Please let me know if you require any further clarification or assistance.

Best regards,