Loose Screw Sends Power Wagon Racing

I bought a DR Power Wagon a few years ago -- an expensive piece of gas-powered yard equipment with a spring-loaded throttle grip. When I uncrated the wagon and started it up, the engine immediately raced. The centrifugal clutch engaged, and the thing took off. Fortunately, I was able to grab the brake and stop it safely.

It took all of 45 seconds to find the culprit. Where the throttle cable attaches to the carburetor, there is a return spring on a bracket. The bracket is held to the engine by one screw. If this screw comes loose, the spring tension rotates the bracket until the spring is loose. Voila: no throttle return spring tension.

The fix was easy. It took longer to find the right wrench than it did to rotate the bracket into position and tighten the screw.

So, a simple quality issue, right? The screw was left loose, or it came loose in shipping. In my industry (automotive), we would never leave something as critical as a throttle spring with such an easy failure mode. The bracket needs two screws so it can't rotate, or a notch or tab or something, even a self-locking fastener. Or the design engineers could have put the spring someplace where the support can't come loose. There are a number of easy ways to solve the problem.

This entry was submitted by Erik Kauppi and edited by Rob Spiegel.

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