Wildcard Week: Designing a gearbox
When designing a system with moving parts, I sometimes find that I don't get enough torque and the mechanism stalls, or the movement can be too slow or too fast, one way to get around this problem is to employ a gearbox. gears are a method of power transmission that operates like a continuously working lever.
The moment (Force X distance) on both sides is equal but the distance and force applied is different, so like how we can use a lever and a little effort to nudge a heavy load, with a gearbox we can move the heavy load continuously but slowly using a small motor. an example for this is starting a car you put it into the first gear which have a big reduction in the wheels rpm in exchange for an increase in torque.
Here the bigger gear is being driven by the smaller gear, the bigger gear spins slower than the small gear meaning that it's experiencing a reduction so it's generating more torque.
This website let's you test out different arrangements of gears and provide a great visualization, in the link you will find an example I made of a series of gears where the output gear is spinning at 1/8th the speed of the input gear, meaning it's a 1:8 reduction gearbox. to read more about types of gears and mathematical calculations check the Wikipedia page on gears.
Designing a gearbox in Fusion 360:
Fusion 360 comes bundled with a script to generate regular spur gears, you can find it in Utilities> Add-ons> Scripts and Add-ons> Spur Gear C++ or Spur Gear Py
It will prompt you to insert your desired parameters, note that for two or more gears to mesh properly they should have the same module, introduce a little more backlash if you're planing to 3d print the gear, if you're planing to CNC mill the gear don't add backlash.
for designing more varieties of gears I used the Helical Gear addon for Fusion 360, it follows the same steps in the spur gear script but also allows the creation of helical and herringbone style gears. I used what I learned about designing in Fusion 360 to make a planetary gear box, in which the driving gear would be the sun gear (middle gear), the driven gears are the planet gears and the outer ring gear is fixed in place in an arrangement similar to this image.
The advantage of a planetary gear system is its compactness while its main drawback is increased complexity. depending on which gear is driven and which gear is fixed in place the planetary gearbox can switch between reduction and a reverse gear, to get into the math of a planetary system check this link here, I find it easy to plan my design off the interactive simulation of this site. I used what I learned and designed the following 8:1 planetary gearbox with fixed outer ring.
the design is suitable for 3d printing without supports and requires no assembly thanks to the herringbone style gear used.
When I move the inner gear 8 times, the planet carrier turns only once.