# Calculating Torque for Ball Screws to Lift 12,000lb Transformer

• SevenToFive
In summary, the conversation discusses the use of four ball screws to lift a 12,000lb transformer, with each screw having a torque of 1800in-lbs. The person asking for help is unsure about this value and wants to confirm its accuracy. The expert explains that the torque is based on the load, pitch, and radius of the ball screw, and that the calculation is similar to that of acme threads. The expert also provides a link to a ball screw design calculator for further assistance.
SevenToFive
I have a set of 4 ball screws, 2 inch diameter by 0.50", one in each corner to lift up a 12,000lb transformer. Each side will have one motor driving a right angle worm gearbox in the center that will power the two other right angle gearboxes that turn the ball screws.
I was given that the torque for each ball screw will be 1800in-lbs. But I am curious on how they came up with that value. I don't have much experience working with ball screws usually we do all Acme threads, or is the calculation similar?

Any help in double checking their calculated torque would be greatly appreciated, as I feel it is a bit low.

The torque is based upon your load and the pitch and radius of the ball screw. If they supplied an attached right angle gear drive then the gear ratio of that unit will also be a part of that calculation.

bsheikho
The computation is the same as for acme threads, but there is much less friction in ball screws.

I assume the ball screw has an outside diameter of 2” and a single-start thread with a pitch of 0.5”.
The screw circumference is 2 * Pi = 6.28”.
The ball is in effect, on a ramp with a slope of 0.5” in 6.28”. That ratio is 12.57
The load weighs 12,000 lbs. That is 3000 lbs carried by each screw.
Divide by the ratio of 12.57 and you get 239. lbs, acting at the screw circumference contact with the ball nut.
The radius to the circumference of the screw is 1 inch, so the minimum torque to hold the load in place is 239 inch lbs.
Does that seem to be a more reasonable value ?

SevenToFive

## 1. What is the formula for calculating torque for a ball screw?

The formula for calculating torque for a ball screw is: Torque = Force x Distance.

## 2. How do I determine the force needed to lift a 12,000lb transformer using a ball screw?

To determine the force needed, you will need to know the weight of the transformer (12,000lbs) and the angle of the screw. Then, you can use the formula: Force = Weight / Sin(Angle).

## 3. Can I use a standard ball screw to lift a 12,000lb transformer?

It is important to consult the manufacturer's specifications to determine if a standard ball screw can handle the weight of a 12,000lb transformer. If the ball screw is not strong enough, it could result in failure and potential safety hazards.

## 4. How does the angle of the screw affect the torque required?

The angle of the screw has a direct impact on the torque required. A steeper angle will require more torque to lift the same weight compared to a shallower angle. This is because the force needed to lift the weight is distributed over a smaller distance at a steeper angle.

## 5. Are there any other factors to consider when calculating torque for a ball screw to lift a 12,000lb transformer?

In addition to the weight and angle of the screw, other factors such as friction, efficiency of the ball screw, and the load distribution along the screw should also be taken into account when calculating torque. It is important to consult an engineer or the manufacturer for accurate and safe calculations.

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