I have some of the gear simulator working.

Video of Simple Gears

The simple gears are self explanatory. This was the first working test. The gear size ratio is set in the coordinate/length/angle text box in the tool bar, or by pressing the Gear Ratio button below that. The Gear Ratio button also allows the type of connection, gears or chain/belt, to be set.

The gear size ration is not a gear ratio per se; It is the ratio of the gear sizes. The only real difference is that setting a ratio is done by specifying how much the output gear turns for how much the input gear turns. A 2:1 ratio would mean that the output turns once for two turns of the input gear. For the Linkage program, you select two gears and simply specify the relative sizes of the gears. 2:1 means that the first selected gear is 2 units in size and the second selected gear is one unit. of course, this could mean that the first gear is 8.5 inches in diameter and the second is 17 inches. This is just a ratio of the sizes. If the same gears are selected in a different order, the Linkage program will show them as 1:2 instead of the original 2:1 value that was specified.

So it’s not a ratio of input to output. it’s just the relative sizes of the gears being specified.

Video of Complex Gears and Chain

Chains added a minimal bit of work to handle the drawing of the chain. This link describes a simple yet effective way to determine where to draw the chain. Gears of the same radius require a slightly different construct to determine the chain position.

I draw the sprockets for the chain at 1/2 the size that I would draw gears of the same size ratio.

Video of a Fastened Gear Rocker

The gear rocker is the first truly interesting mechanism that I got working. The big gear if fastened to the rocking link. It also drives the small gear, thus multiplying the rocking motion and letting it work over more than 180°. With just the crank and the rocking link, the rocking link can never go more than 180° in one complete cycle.

In all of these tests, the gears rotate on anchors. I have not tested moving gears yet because there are some parts of the UI that I haven’t finished yet; I haven’t even decided on how everything will work yet.

Some remaining issues and challenges are:

How can I let users fasten links to the ground. Anchors are connectors that are essentially attached to the ground, but gears are allowed to rotate freely on an anchor just like any link. It should not be necessary to fasten a gear to a link that has two or more anchors just to keep the gear from rotating.
How do I display the fastening of one element to another? It’s clumsy to make users remember what they fastened together, especially for gears and links. Drawing elements never matters quite this much.
Will it be difficult to understand a mechanism if there are two anchors in the exact same location to accomplish interesting gear mechanisms? Perhaps a gear fastened to the ground at the same location as a rotating input anchor would make for an interesting machine.