The Myth Of Motor Ratings

The Myth Of Motor Ratings
Is bigger always better? It turns out that no, well, at least in the world of treadmills. The motor rating is one of the worst indicators you can use to determine the quality of a treadmill. Don't believe me? Let's take a look.

The LifeFitness 91Ti has a 3.0 HP rating for its monitor. It retails for $5000+. Life Fitness is a well known brand and a popular choice for many commercial settings such as your local gym.

Let's contrast this to the Proform 650e Treadmill, which retails for about $700. Its specs say it has a 2.8THP Motor rating. You start to think, WOW! I'm getting a motor rated only 0.2HP less than the 3.0 Horse Power found in the LifeFitness treadmill at one seventh the price. A steal you say!

I'm afraid that if you fall for this type of reasoning, the only thing that's going to be stolen is the $700 dollars from your bank account. When things sound too good to be true, they usually are.

THE MOTOR RATING LIES ONCE

If you read carefully, the 2.8THP has a "T" in it. The T stands for total which means the max or the peak horsepower at which it can run at. In other words, the motor cannot run at this high of a horsepower for long (if at all!).

This is analogous to our own personal peak when we run. Let's say that you do an all out sprint. How long can you maintain the speed of your sprint? 1 minute, 2 minutes? Now what if you were walking? If you really had to, you could probably walk the entire day.

If we go back to our motor analogy, you want the motor to be rated in such a way so that it can maintain itself forever and ever such as when we walk. After all, if the motor stops running, you stop running.

THE MOTOR RATING LIES AGAIN

Knowing that the total horse power rating given to treadmills was not an accurate indicator, the continuous horse power rating (CHP) was developed. The CHP was meant to show just how much actual horse power is contained within a motor. The CHP was supposed to represent the walking speed in our analogy. The CHP was supposed to tell you the truth!

Nope.

THE TRUTH

The CHP does not tell you the whole picture.

Horsepower is a value computed by multiplying and dividing several values using a formula. One of these values is known as the RPM or rotations per minute. Basically, a motor can be tweaked to have a higher horsepower than it deserves by increasing the number of rotations per minutes.

So what’s the problem? By the formula’s definition, if you increase the RPM, the horsepower is increased. How does that constitute a lie?

Well, let's extend our previous walking analogy.

As an example, let's say that I was able to previously walk at a speed of 3.0 miles per hour and I'm able to maintain this speed for the entire day. This is the maximum speed that my body can maintain without any negative effects. No negative effects meaning I can wake up the next day feeling fine. If I force myself at 4.0 miles per hour for an entire day, I might be able to do it if my life depended on it but then I might be in the hospital recovering for a month hence the negative effects.

Let’s extend the above analogy a little further. Suppose a friend constantly supplies me a Red Bull sugar drink during my walk. Now with all this new energy that this (sugar) energy drink provides me, I'm able to walk at 4.0 miles per hour for the entire day without needing to go to the hospital afterwards.

A motor that runs on a high RPM to achieve its horsepower is analogous to me being supplied with a sugar drink during my walk. The Red Bull was a stimulant that allowed me to walk faster than what my body could usually support. If I wanted to maintain a speed of 4.0 miles per hour, I would have to continue to take my daily doses of red bull. What would happen to my long term health if I had six Red Bulls a day, every day? What would happen to your motor in the long run if it was juiced up to run faster than it was meant to support?

A small motor running at a higher RPM than it was meant to be is like a small person lifting heavier weights than its body can handle. It’s like a person taking a sugar drink to purposely jack up and maintain its walking speed. It might be OK in the short run but in the long run, something is bound to go wrong!

So in the end, the paper specs that lists the motor rating is not nearly as useful as we would like. The total horse power (sometimes disguised as just horse power) is not of much use. The continuous horse power rating is more useful but doesn’t tell the revolutions per minute story.

In theory, a truly high quality motor has ALL of the following:

1. A high CHP rating (We recommend 2.0+ for walking, 2.5+ for jogging, 3.0+ for running)
2. The motor itself is large in size
3. The motor is tuned at a low RPM.