pic: Gerrish Gearbox MK-III #2

[Paul Copioli]

O.K. Mr Beatty (and Tytus),

Let's break down a differential in planetery gearset lingo:

1. The input from the engine (transmission) is the equivalent of a ring gear in a traditional planetary (team 217 drives this gear also.

2. The ring gear in a differential (the big gear that houses the differential gears) is really the carrier in a planetary set and it is being driven ONLY by #1 and is not the output. The 217 CCT carrier is the output and is driven by the sun gear (see below) and the ring gear.

3. The little differential gears are the planets in a planetary set and they are free to spin. Same as 217 CCT.

4. (The biggest difference) The side gears in a differential that drive the wheels are free to spin and are both outputs for the system. They would equate to the sun gear in a planetary set. Equal torque is applied to each wheel no matter what.
The 217 CCT uses this as another input (the main driver), so it is a true planetary, not a differential.

The main difference between the differential and the planetary, in general) is the differential has 2 sun gears (the output to the wheels) that are being used as outputs. The planetary gearset has only one output. The CCT, in addition to the differences above, also uses the carrier as the output and the ring gear and sun gear are inputs.

While I agree that a differential is a relative of the planetary gearset, the 217 CCT is NOT a differential.

-Paul

BTW - I agree with Mr. Beatty that a differential can easily be used with spur gears instead of bevels.