Understanding Horsepower Ratings on Hoists

2 comments

by  on November 12, 2015

Q & A chatChris, an ETCP certified rigger and recent safety webinar attendee, asks the following question about horsepower ratings on hoists:

“I don’t see Columbus McKinnon hoists rated with horsepower, however they are sometimes referred to by that rating. Does that relate to the FPM capability? I am guessing that a faster FPM hoist would have to have a ‘stronger’ electric motor. Looking forward to your comments.”

Dave Carmack, Columbus McKinnon Entertainment Trainer, ETCP Recognized Trainer and recent safety webinar presenter, responds:

To answer this question, let’s take a look at the history of horsepower. When steam engines were invented, the designers wanted to know how much work the steam engines could do in comparison to a horse of that day. This is where the term horsepower originated.

Horsepower is a measurement of power at the rate at which work is done. When we measure the power of a horse, we see that one horse can do 33,000 foot pounds of work per minute.

Now, the question of horsepower is: I want to move an object from one place to another in a specific amount of time. How much effort (or power) will this take?

Looking at the Lodestar, this hoist can have a variety of different horsepower ratings, depending on the capacities and speeds. For example, take a look at the 1/2-ton Lodestar below:

1. ½ ton unit with a lifting speed of 8 fpm is a ¼ hp
2. ½ ton unit with a lifting speed of 16 fpm is ½ hp
3. ½ ton unit with a lifting speed of 32 fpm is 1 hp
4. ½ ton unit with a lifting speed of 64 fpm is 2 hp

We also need to consider the gear ratio and the type or size stator we use in the motor to accomplish how much weight and at what speed the hoist needs to work.

Want to learn more? View our Safety Webinar on: Frequently Asked Questions During our CM ET Motor Schools.

{ 2 comments… read them below or add one }

Dave Carmack Dave Carmack November 13, 2015 at 4:38 pm

Hello Mike,
Thank you for your comment. You are correct. It does take less torque to move something sideways than it does to lift something. Great addition!
Dave

Michael Bongner November 13, 2015 at 10:15 am

“Torque” is the most important part of this calculation. As a general thumb-rule, it takes 1HP to lift 1 Ton, 16 FPM with a motor running at 1800 RPM. The torque required to perform this task is about 3 lb-ft. If you try to lift 2 tons with the same motor, it will stall because there isn’t enough torque.

Your topic question mentions MOVING “an object from one place to another”. Traversing motions require similar calculations but less torque is needed to move the same load on a horizontal plane.

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