Sunday, September 24, 2017

Peterbilt Air Trac

In 1972 I worked for Pacific Provisions in South San Francisco driving a Peterbilt truck hauling produce to the mid-west and meat back to the west coast. The truck had what Peterbilt called an Air Leaf suspension on the drive axles. This consisted of an quarter elliptic spring for each wheel with one end anchored to the frame and an air bag mounted on the other end attached to the axle.

I noticed while watching the suspension in my mirrors that every time I turned, the drive axles would get quite a bit out of alignment with the frame. I also noticed that the springs would wind up when accelerating or braking. I was not in the habit of driving in such a way that I would break springs, but on this truck I was breaking them fairly often.

I was in the San Francisco Eng Peterbilt dealership getting another broken spring replaced when I wandered into the office of one of the salesmen. I told him I had broken another spring and explained to him why I thought it was happening. The axle alignment issue along with the springs winding up was what I thought was the cause.

I said what the suspension needed was a panhard bar going from each axle to the frame to keep it in alignment along with a torque arm parallel to the spring to keep it from winding up. I drew the whole thing out on a piece of paper for him. This wasn't any kind of radical insight on my part. This was a very basic way of controlling a rear axle used in many race cars.

A few months later at a big truck show, Peterbilt introduced their new air ride suspension called Air Trac. This was exactly the design I had drawn out in the salesman's office.

The next time I was in the Eng Peterbilt dealership for service, I went to the salesman and asked him how Peterbilt happened to introduce the same suspension I had drawn for him.

He said, "I took your drawing along with your explanation of what was happening down to the factory in Newark, CA. They liked the idea and wanted to know if you had any other suggestions."

I never received any money for my idea, I gained something even better. I gained the satisfaction of seeing my design widely used in Peterbilts all over the country for the last 45 years.

 

1 comment:

  1. I'm glad they were open to new ideas! Sounds like a great engineering fix. I once told Nutella that a chunky hazelnut/cocoa spread would be delicious (like chunky peanut butter).

    Their response: "As a result, and because of the risks associated with accepting unsolicited ideas, Ferrero U.S.A., Inc. does not, as a matter of policy, generally accept such suggestions relating to our products. Accordingly, we cannot pursue your idea at this time."

    I guess they didn't want the risk of me suing them!

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