Confused How Does The Engine And Transmission System Work Together How Does The Transmission System Work
Posted in Internal Engine Parts | Asked on May 25, 2010
I have a 49cc, air-cooled, 4 stroke, single cylinder scooter. I’m trying to learn the basics of how the engine and transmission systems work. I didn’t want to take the scooter apart just to learn and I wanted to know what the hell I’m doing first and how everything works together as one unit before attempting to do anything with it.
I’ve been learning about the various sub-systems online, in bits and pieces, and I’m learning how it all works together in unison as I go along. From what little I’ve learned so far, I understand the jobs of the carburetor, camshaft, crankshaft, piston, spark plug, intake/outtake valves, fuel line, fuel filter, air box, motor oil system and the exhaust system. Although it took me while to figure some parts of it out, I pretty much understand how all these items work together as one now.
But for whatever reason, I cannot figure out how the engine connects to the transmission system. I’m also having difficulty in understanding the full concept of how the transmission system works exactly. I know that the variator and the clutch are combined with a drive belt to produce the drive system. I guess they produce higher and lower rpms through the use of some kind of self-regulating gearing system that seems to be similar to that of a 10 speed bike gear system. I believe that the clutch connects to the transmission gears which connects the power from the clutch to the rear tire. Although I could be wrong, it seems to fit.
So how does the transmission system work? Am I missing anything or is that it?
How and where does the engine system connect to the transmission system? Is the connection point between the crankshaft and variator? Is it a belt system or gear system?
There are 3 Answers
These links should be very helpful, they use moving animations to help understand.
http://www.howstuffworks.com/clutch.htm
http://www.howstuffworks.com/engine.htm
http://auto.howstuffworks.com/transmission.htm
If it is a conventional transmission, then it is likely that the crank shaft has a sprocket on one end that drives a sprocket on a multi-disc clutch with a chain. The clutch is mounted to the input shaft of the transmission. It could also be a v-belt drive with an expanding pulley.
A conventional manual transmission has an input shaft with a cluster of different diameters of gears which engages an output shaft with another cluster of gears. The output shaft has a sprocket that drives the chain that turns the rear wheel. The output shaft slides back and forth when you change gears, to engage gears of different ratios to change the speed of the engine relative to the speed of the rear wheel.
You should be able to remove a side cover to look at the primary chain between the crank shaft sprocket and the clutch assuming your scooter has this arrangement.
The link at the bottom has a video which explains the manual transmission.
For a scooter, unlike many other transmissions, you need to know how Continuously Variable Transmission (CVT) works.
http://auto.howstuffworks.com/cvt.htm
There are a number of final drive systems but for scooters the majority is the cheap and light belt pulley system. These work by running the engine at the optimum revs per minute (something that traditional gearbox and engine combinations do not allow). By keeping the revs stable the output of the engine is stable, the drive belt turns the rear wheel, in order to accelerate the rear wheel has to turn faster, rather than achieving this by increasing the number of times the belt rotates, the “sprocket” at the rear wheel gets smaller (meaning the rear wheel turns more frequently for every rotation of the belt). It achieves this by having two cones facing in opposite directions (points closer together) mounted, but free to travel laterally, on an axle with the belt driving them and held together by a spring (I am oversimplifying here) centrifugal force (of the spinning wheel) forces the cones apart, as the cones are forced apart the belt drives a smaller “sprocket”, turning the wheel more frequently. However some systems also use the cone system on the drive “sprocket”.
Look at the pulley drive system for a better illustration.
http://auto.howstuffworks.com/cvt2.htm