How Does Torque Affect a Heavy-Duty Lid Support Hinge?

When trying to include an innovative or safety-minded motion control design in your product, there’s a sneaky-confusing word you should know: torque. 

Torque is very important. That’s why you hear so many Ford F-150 truck commercials bragging about “torque ratings.” It’s a critical aspect of counterbalance hinges too, as they generate torque to counter gravity’s force.

Below you’ll find an easy-to-follow guide to understanding torque and its role in a heavy-duty lid support hinge. In no time, your lid will boast a safe, smooth open and close.

The Heavy-Duty Lid Support Hinge and the Importance of Torque.

By knowing the torque of your lid, the counterbalance hinge your manufacturer designs will provide your desired action and balance. If the calculation is wrong, you’re at risk of selling a product that:

• Crashes on heads and fingers
• Doesn’t lift and close smoothly, giving off an aura of cheapness
• Floats in a half-up position, leaving it susceptible to wind or bumps from nearby folks
• Doesn’t provide a good seal
  
  

What Is Lid Torque?

Torque depends on the weight and size of your lid, door, or cover. Torque is defined as the lid’s weight multiplied by the distance from its center of gravity to the hinge axis.

Consider an industrial toolbox lid. Gravity induces a torque at the hinge axis that slams the lid closed or, at some angles, causes the lid to open further.

Let’s pretend we have a solid aluminum lid that’s:

• 32” wide
• 24” deep
• 1” thick
• 75 pounds

The lid’s center of gravity would be in its geometric center, 0.5” up from the bottom surface and 12” away from the back edge. Remember, the pivot axis is an additional 0.75” beyond the back edge and on the same plane as the bottom of the lid.

When this lid is closed (0° open), the center of gravity is a horizontal distance of 12.75” from the hinge pivot axis and a vertical distance of +0.5” from the axis. This means the lid torque in the closed position will be 12.75 in. x 75 lbs., which comes out to 956.25 in.-lbs.

This will be the largest torque for this lid design. The torque will decrease as the lid is opened, as you’ll see below in the diagram.

Note that in this example, the center of balance is above the hinge pivot axis, so the vertical distance is positive. If the center were below the axis, the vertical distance would be negative.

Other Numbers That Matter

Once the design engineers get all the data they need, they can develop the perfect counterbalance. The more information they get, the quicker the design process can go.

Start by finding these measurements. If you don’t know how to find them, your counterbalance hinge manufacturer should be able to help:

• Center of gravity
• Balance angle
• Balance point
• Lid weight

You can learn more about these measurements here. With the right numbers, you’ll get a lid that’s smooth and safe rather than floaty or crashy!

To see more about lid torque and counterbalancing, check out the Vectis DYO App, which allows engineers to design their own counterbalance right in their web browser. Once you provide your data, the Vectis App plots the lid torque at all angles -- a handy reference for defining the counterbalance hinge you want. With the lid torque defined, you can adjust the app’s other parameters as needed.

There are other design factors you should relay your motion control design team to ensure a successful project. To get a better understanding of those factors, ask an engineer directly by clicking below: