This is an automatic synchronous transmission with Drive, Neutral and Reverse. It also features a switched light to indicate the selected gear. When Drive is selected, the light glows constantly, when Neutral is selected, the light is off and when Reverse is selected, the light flashes. It has realistic gearing so that the wheels turn more slowly and in the opposite direction for Reverse gear.
It is similar to MOCpages member Ape Fight's gearbox, but I added a few bells and whistles! Thanks to Ape Fight for paving the way! I highly recommend looking at his creations :-)
About this creation
I built a separate automatic transmisssion with white beams for easier viewing. Its mechanism is identical to the one built into my LS400 shown below.
Note the coloured plates - I used colours to clearly show the mounting heights for each axle and moving part.
I left the top covering plates off for a good view of the insides!
The axle with the wheel is the output shaft, which goes to the rear wheels. The axle with the 3-blade rotor is the input shaft, and is connected to the engine.
Power is connected, Drive is engaged and the light glows constantly.
A view of the underside. Everything is very tightly packed.
The light has just enough room to fit in without rubbing against any moving parts, in particular the driving ring.
The light looks very nice, but let's remove it for a second and have a look inside at the workings!
Remember, real cars' engines turn the input shaft (3-blade rotor end of gearbox), the gearbox selects the gear, then the output shaft (wheel end of gearbox) turns and rotates the rear wheels.
But, in the Lego world, the reverse occurs - the rear wheels are turned, power comes into the gearbox via its output shaft, the gearbox selects the gear, power is then transmitted from the gearbox's input shaft to rotate the engine.
I have geared this transmission in the same way as a real car, assuming that the engine turns the rear wheels. However, when I push the LS400 along, so the rear wheels are driving the motor, changing gears only alters the speed and rotational direction of the engine. In drive, the engine rotates slowly. In reverse, the engine rotates more rapidly and in the opposite direction. When neutral is selected, the engine does not rotate at all, but the rear wheels can still freely rotate.
Assuming the car is being pushed along;
When Reverse is selected, incoming motion rotates the dark grey 16-tooth clutch gear on the left, then the pair of 16-tooth gears under it, then the 8-tooth gear and the 24-tooth gear on the same axle, finally rotating the 16-tooth gear on the right which is on the input shaft (3-blade rotor end that connects to the engine). The dark grey 16-tooth clutch gear on the right will also rotate, but its motion is disconnected from the axle passing through it because selecting Reverse automatically disengages the dark grey 16-tooth clutch gear on the right. Only one clutch gear can be engaged at a time; never both at once. The engine will turn rapidly. If the engine was driving the rear wheels, even rapid clockwise rotation of the engine would result in the wheels slowly rotating in an anti-clockwise direction. From the engine to the rear wheels, Reverse gear reduces the speed by a factor of 3 - ie 33% of engine speed and the direction of rotation is reversed.
When Drive is selected, incoming motion rotates the dark grey 16-tooth clutch gear on the right, then the 16-tooth gear on the right which is on the input shaft (3-blade rotor end that connects to the engine). The other five gears will rotate too, but by the time motion reaches the dark grey 16-tooth clutch gear, the motion goes nowhere. Selecting Drive automatically disengages the dark grey 16-tooth clutch gear on the right.
When the vehicle is pushed along with Drive selected, the engine will turn slowly and in the opposite direction of Reverse gear. If the engine was driving the rear wheels, the wheels would rotate as rapidly and in the same direction as the engine was rotating. Drive has a simple train: a 16 tooth clutch gear driving a 16-tooth gear, so Drive gear is direct and does not apply any gear reductions.
When Neutral is selected, both dark grey 16-tooth clutch gears are disengaged, so incoming motion from the rear wheels goes nowhere and the engine will not rotate at all.
If the engine was driving the rear wheels, rotating the engine would not have any effect on the rear wheels.
You can see the heights of the gears by counting the coloured plates between mountings.
Note the two mirror-image changeover catches. They are both the same distance from the driving ring and on the same centre. The upper changeover catch is connected to the gear selection lever (pole reverser handle part) and the lower changeover catch is connected horizontally (with an axle) to the electric switch that selects the gear indicator light's mode of operation. The switch must be aligned properly, so that when Reverse is selected it flashes, when Drive is selected it is constantly on and when Neutral is selected it is off. Rotating the switch's inner barrel 90 degrees each time will soon align it properly to the correct gear.
Here is the automatic transmission installed in my Lexus LS400.
I hope this gives you a few ideas! Thanks for looking. Please comment and rate :-)
Quoting lachie master
this is one of the best creations i have seen i really like you saloon car it looks like it bust be a pretty big scale hope you can tell me?
cheers keep the good work up!!!!!
It works out at about 1 to 8.5 scale. My main focus was on making the length, width, height and wheelbase all in proportion to each other and using trial and error until it looked right. Thanks for your kind comments ;-)