The term “derby cover” comes from an old design for clutch access covers that Harley-Davidson used decades ago. That design had a strong resemblance to a derby hat. Since bikers are always the same, they gave it a name, and the name that stuck was “derby cover”.
This is a photo I took a few years ago at the Harley-Davidson Museum in Milwaukee, showing the shape of the derby cover that they used at the time:
You can clearly see the resemblance to this hat:
Those old derby covers were made of pressed steel. Because the metal was so thin, they needed a large number of mounting bolts to secure it to the outer primary and prevent leaking. (They used cork gaskets back then.)
Fun Facts
Back in the day, Harley didn’t use the term “derby cover”. That came later. In fact, most of the commonly used lingo in the Harley enthusiast world was generated by bikers themselves, not the company. Terms like “Knucklehead”, “Panhead” and “Shovelhead” came from individual bikers. It wasn’t until the Evolution motor came along that Harley even gave a name to it’s current motor. We’re accustomed now to “Evo” and “Twin Cam” and “Milwaukee 8”, but back in the day Harley didn’t use names.
There was some effort to call the Evo motor the “blockhead”, but that one never caught on, so it stayed “Evo”.
Horse Racing Has Nothing To Do With It
Contrary to some claims out there, the term “derby cover” has nothing to do with horse racing, or the Kentucky Derby, or any of that. Derby covers are called derby covers because in their original form, the Harley-Davidson clutch access cover looked like a hat. That’s it. Nothing more.
