Page 212 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

190 Making Things Move

he guts of a mechanism are everything that happens between the input and
Toutput. The input is your energy source, which can range from a hand crank to an
electric motor. The output is what you want to happen—does your mechanism
crawl, spin, point, or shake? Maybe you need to attach a gear to your motor shaft or
figure out how to make something spin with lower friction.
The components we’ll cover in this chapter are integral to being able to work through
your ideas and make them into reality. The majority of them can be found through a
quick search on McMaster and other suppliers I’ll point out along the way.

Bearings and Bushings

Bearings are components that are used between moving parts and stationary parts
for support and reduction of friction. A bearing can be as simple as a drilled hole in a
block of wood, or it can be an actual steel ball bearing, as in inline skates or skateboard
wheels. You can also find bearings inside motors, where they help to support the
motor shaft and keep it running smoothly.

Bearings are categorized by the kind of load they support:

•A radial bearing, like the type in your inline skates, supports radial loads.
(Recall the illustration of radial and axial loads in Figure 1-26 in Chapter 1.)
•A thrust bearing handles the axial loads. You can find this kind of bearing in
rotating bar stools and chairs that support your weight but still spin.
• A linear bearing, or slide, reduces friction in sliding components that don’t
necessarily spin. You can find this type of bearing on the sides of filing
cabinets and dresser drawers.
• A bushing (also known as a sleeve, plain, plane, or journal bearing) is a type of
bearing that doesn’t have rolling elements, but still reduces friction for radial,
thrust, or sliding loads. Think of a bushing as a “female” bearing—one
without, um, rollers. You can find linear bushings inside machines like
MakerBot’s CupCake CNC (see Figure 7-1).

The following sections cover these types of bearings in more detail and go over when
and how to use each one.