Variable Transmission on cars


Variable Transmission on cars

In: 0

What? You forgot to ask the actual question.

Describe the ask in more detail.

It’s an interesting combination of the input and output drives and the linkage. My brother in law has such a vehicle, but instead of utilizing the CVT, there is an electrical setting that emulates, or mimics a geared transmission.

See the image in the link below. The input system forms a wedge; the linkage is wedge-shaped; the output is similarly a wedge. By controlling where the linkage rides on the input wedge, and on the output wedge, you have the balance between Power vs Speed.

The equivalent of 1st gear, you want the output RPM to be greatly reduced from the input. This might be a ratio of 5:1, for every 5 rotations of the engine, the drive shaft rotates once. This helps get all of the mass moving.

Second gear might have a ratio of 3.5:1. Third gear maybe 2:1. Fourth gear might be 1:1. Fifth gear might be 1:3 (over drive). At each increment, you’re trading power for speed.

A CVT car skips those increments and simply progresses smoothly between power and speed.

BTW: Consider the M-1 Abrams tank. It uses a jet engine to move. I can only imagine that the initial gearing needed to get those 55 tons moving (110,000 lbs!!) Is something like 20:1–4.3:1. I’m sure an Abrams technician can correct me.

Assuming you’re talking about CVTs and already understand the mechanical advantage that gears can provide:

There are 2 sets of “plates” on each side of a belt, but the plates are slightly conical (like a very wide, short party hat). If you pinch the plates closer together, it forces the belt out to a bigger diameter which acts like a “big gear”. If you don’t pinch the plates as much, the belt slides between the plates even deeper at a smaller diameter which acts like a “small gear”.

Using this, you can have a “continuously variable” range of gearing simply by squeezing less or more on the belt.

To visualize more, think of two party hats with the tips facing towards each other and a rod connecting them. If you take a big enough piece of paper and wrap it around the big ends of the cones, this is again representing your “big gear”. By moving the party hats away from each other, eventually the paper will be able to wrap around just the stick connecting them which is the “small gear”.