Rack and pinion gears are accustomed to convert rotation into linear movement. A perfect example of this is the steering system on many cars. The tyre rotates a equipment which engages the rack. As the apparatus turns, it slides the rack either to the right or left, depending on which way you turn the wheel.

Rack and pinion gears are also found in some scales to turn the dial that displays your weight.

Planetary Gearsets & Gear Ratios

Any planetary gearset has three main components:

The sun gear
The earth gears and the planet gears’ carrier
The ring gear
Each of these three components can be the insight, the output or can be held stationary. Choosing which piece has which function determines the gear ratio for the gearset. Let’s have a look at a single planetary gearset.

Among the planetary gearsets from our transmission includes a ring gear with 72 teeth and a sun gear with 30 teeth. We can get lots of different gear ratios out of this gearset.

Input
Output
Stationary
Calculation
Gear Ratio
A
Sun (S)
Planet Carrier (C)
Ring (R)
1 + R/S
3.4:1
B
Planet Carrier (C)
Ring (R)
Sun (S)
1 / (1 + S/R)
0.71:1
C
Sun (S)
Ring (R)
Planet Carrier (C)
-R/S
-2.4:1

Also, locking any kind of two of the three components together will secure the complete device at a 1:1 gear reduction. Observe that the first equipment ratio listed above is a Vacuum Pump reduction — the output swiftness is slower compared to the input swiftness. The second is an overdrive — the output speed is faster compared to the input swiftness. The last is usually a reduction again, however the output path is normally reversed. There are many other ratios that can be gotten out of the planetary equipment set, but they are the types that are relevant to our automatic transmission.

So this one set of gears can produce most of these different gear ratios without having to engage or disengage any other gears. With two of the gearsets in a row, we are able to get the four ahead gears and one invert gear our transmission needs. We’ll put both sets of gears collectively in the next section.

On an involute profile equipment tooth, the contact point starts closer to one equipment, and as the apparatus spins, the contact point moves from that gear and toward the other. In the event that you were to check out the contact stage, it would describe a straight range that begins near one equipment and ends up close to the other. This means that the radius of the get in touch with point gets larger as one’s teeth engage.

The pitch diameter is the effective contact size. Since the contact diameter isn’t constant, the pitch size is really the common contact distance. As one’s teeth first begin to engage, the top gear tooth contacts the bottom gear tooth in the pitch size. But observe that the part of the top gear tooth that contacts the bottom gear tooth is quite skinny at this stage. As the gears switch, the contact stage slides up onto the thicker part of the top gear tooth. This pushes the top gear ahead, so that it compensates for the somewhat smaller contact size. As the teeth continue steadily to rotate, the get in touch with point moves even further away, going outside the pitch diameter — however the profile of underneath tooth compensates for this movement. The contact point begins to slide onto the skinny area of the bottom level tooth, subtracting a little bit of velocity from the very best gear to pay for the increased diameter of contact. The end result is that despite the fact that the contact point diameter changes continually, the quickness remains the same. Therefore an involute profile equipment tooth produces a continuous ratio of rotational quickness.