# Making torque calculation from spring specifications

• pete
In summary, the conversation discusses the use of a counterbalance weight and the specifications of a constant torque motor. The speaker is attempting to calculate the force needed for the counterbalance using the diameter of the torque output drum and the torque value provided. They also mention using a barrel with a cable wound around it to achieve the desired counterbalance weight. However, they are unsure if their calculations are correct and seek further assistance on a physics forum.
pete
I was thinking about making a kind of counterbalance weight. So I was looking this spring to make a constant torque motor.

https://www.ondrives.com/sr119

They come in many sizes but to take this one as an example it's listed as 6.18N (63kg) at the top of the page. At a glance considering the size of the spring, this seems like a very small number in N and a very large one in Kg.

My maths is not too good so I spent some time looking up how to get this from the specifications and this is my attempt.

This is the bit I’m hoping someone can look at and tell me if I’m doing this right. I took the diameter of the Torque output drum-D3 and divided it to get R - 87mm so 8.7cm. Changed it to meters so .087m then divided by the Torque 6.18 to get 71 N force.

So a barrel with a cable wound around it of the same diameter as D3 will give me roughly 7Kg counterbalance over the specified range of the spring (Dimension L) 12.8 meters.

This still seems low but then I have calculated for a barrel of 17cm diameter. Once you get down to an output shaft of around 15-20mm diameter it would be around the 63kg point.

How did I do?

I moved this question over to the Physics forum. "Trying to do the equations for a spring"

## 1. How do you calculate torque from spring specifications?

To calculate torque from spring specifications, you will need to know the spring constant (k) and the distance from the center of the spring to the point where the torque is being applied (r). The formula for torque is T = k * r. Simply plug in the values for k and r and you will have your torque calculation.

## 2. What units are used for torque and spring specifications?

Torque is typically measured in Newton-meters (N*m) or foot-pounds (ft-lb), while spring specifications are usually given in units of force per distance, such as Newtons per meter (N/m) or pounds per inch (lb/in).

## 3. Can torque be calculated for any type of spring?

Yes, torque can be calculated for any type of spring as long as you have the necessary specifications, such as the spring constant and distance from the center of the spring to the point where the torque is being applied.

## 4. What factors can affect torque calculations from spring specifications?

The main factors that can affect torque calculations from spring specifications include the material and shape of the spring, the amount of compression or extension of the spring, and any external forces or loads acting on the spring.

## 5. How accurate are torque calculations from spring specifications?

The accuracy of torque calculations from spring specifications will depend on the accuracy of the given specifications and the assumptions made in the calculation. It is important to use precise measurements and take into account any external factors that may affect the torque calculation.

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