What's Your Favorite Worm?

It's that time of the month where I take some industrial product, make comparisons to another unrelated object or pretend to be confused by the name, and then ask you to visit one of GlobalSpec's ever-increasing database of industrial product selection guides.

Yes, you're welcome. Let's get started. For the rest of this post you can call me Dr. Worm. I'm not a real doctor, but I am a real worm.

Speaking invertebratically, worms-are the generic term for non-arthropods that function without a backbone. This generally includes earthworms, tape worms, hook worms, round worms, inch worms, arrow worms, and an otherwise endless list of creepy-crawlies that I'm too kind to depict.

So, we'll go with the standard nightcrawler as our mascot, since it's the cuddliest worm of them all.

...via How Stuff Works

There is a particular type of gear that is cuddly as well! I'm talking about the worm gear family!

Worms and worm gears are gear sets that offer high gear reduction and torque multiplication with a small footprint. A worm drive is a cylindrical gear with a shallow spiral thread that engages the worm gear in a non-intersecting, perpendicular axes configuration.

...via U of Memphis

Perhaps part of the reason worm drives got their name is because the side profile of a worm drive looks like the segmented body of an earthworm.

Efficiency of a worm drive is determined by the lead angle and the number of threads in contact with the worm gear. A high lead angle on the drive reduces frictional losses and heat. A low lead angle reduces gear speed while proportionally increasing torque. Friction is an issue with all worm sets; the worm gear cannot transfer motion back to the worm drive in most instances. Lubrication and ground teeth both contribute to the sets' overall silence while minimizing friction. Worm gear sets are usually produced in pairs due to their precision.

Earthworms, similarly, can only have forward locomotion, since they move by a process called peristalsis. They're also incredibly slow-moving, like a worm drive. Perhaps worms and worm drives have more in common than anticipated.

The mounting of worm gears is critical to their implementation. Multiple points of contact are necessary between the drive and gear so high workloads do not overwork the same lead angle, which could lead to gear failure. Enveloped worm gear sets are normally assembled in the same housing, to ensure proper mating and due to the sets' small footprint.

...via I Secretly Love That Song

Consider the gear center, bore diameter and shaft diameter. The gear center can be a bored hole or an integral shaft. The bore diameter is the diameter of the center hole. The shaft diameter is the diameter of the shaft for gears with an integral shaft. Worms and worm gears can be mounted on a hub or shaft. A hub is a cylindrical projection on one or both sides of a worm or worm gear, often for the provision of a screw or other shaft attachment mechanism. Hubless gears are typically attached via press fit, adhesive or internal keyway.

There is more to worm gears than what I've decided to copy and paste from the selection guide. (Seriously readers. YOU know ME. What do you expect?)

So, for a complete reference, as well as links to other types of gear sets, I encourage you to visit GlobalSpec's Worm and Worm Gears Selection Guide. There you can learn all about how to bait fishing hooks, treat your dog for tape worms, and select replacements for your engineering needs.

...via Desura