Spinning Levers (1936)

[Music] [Applause] [Music] [Applause] [Music] meet Mr Archimedes of ancient Greece long ago Aris said give me a lever long enough and I can move the world what Archimedes meant was that the power of a lever is practically unlimited today almost everyone uses some form of lever in his daily work the familiar can opener is a lever with a sharp Cutting Edge the playground seesaw is just a simple lever too it takes a lot of force to start a freight car moving yet The Railroad Man can start the heaviest Freight cars easily with a pinch bar a power lever which turns the wheel tough luck old boy here's a place where a lever comes in mighty handy let's take the simplest kind of lever a rigid bar working on a fixed Support called a fulcrum one end of this lever is twice as long as the other let's put a 10 lb weight on this end and now we'll put half as much weight on this end 5 lb balance 10 if we have 25 lb to lift we just use a longer lever the 5 lbs will now balance five times as much let's raise the lever in the air change its shape a little and we have a crank or we can add a second lever and have a double crank now the short arm moves 1/4 the distance but we get four times the force if we want continuous motion we need more arms now we have lever the turn the larger Paddle Wheel makes fewer turns but it delivers more force a Paddle Wheel is nothing but a NeverEnding series of levers we can make the wheel stronger and lessen friction where the wheels touch each other by rounding off the edges and shaping them into teeth that will slide in and out smoothly now the power flows smoothly and continuously through spinning leverage of gear Gear wheels gears are made in many kinds and many sizes little gears big gears worm gears bevel gears and even lopsided gears over a 100 million gears are spinning over the roads in the Transmissions of our automobiles the transmission is located right at the bottom of the gearshift lever let's start from scratch and put together a model of the gears that we shift in our motorc car the shaft on the left comes from the engine the shaft on the right carries the power back to the rear wheels to connect these two with gears we'll need another shaft known as a counter shaft these two gears carry the power from the engine shaft to the counter shaft and are always connected or in mesh this gear on the drive shaft going to the wheels is free to turn around the shaft we'll put it in mesh with another gear on the counter shaft these gears are always in mesh and keep turning while the engine is running to switch from one set of Gears to another our transmission needs a short shaft like this known as a touch sleeve it cannot turn on the drive shaft but it is free to slide back and forth on the sleeve we'll mount a large gear which we can shift back and forth to mesh with the small gear in the middle of the counter shaft we are now in neutral the the gears that are always in mesh are turning over with the engine but the shaft to the rear wheels is standing still a 3,000lb automobile takes a lot of force to start so in low speed we get the greatest leverage by letting the smallest gear on the counter shaft turn the largest gear on the drive shaft the engine on this model is running at a constant speed of9 0 Revolutions a minute with low gears in mesh the rear wheel is turning at 30 Revolutions a minute about a third the speed of the engine but with three times the force the power is going through these gears in the transmission after we've started the car rolling we want fast pickup so we shift into second by sliding the sleeve backward to mesh with this gear on the shaft to the rear wheels the wheel is now turning at 60 Revolutions a minute and the power flows through these gears for higher speeds we let the power go directly to the rear wheels we shift the sleeve forward so that it meshes with the shaft from the engine the power travels straight from the engine to the drive shaft now the shaft to the wheels is turning at 90 Revolutions a minute the same speed as the engine but here's a problem an automobile must be able to go backward as well as forward so we add one more set of gears to reverse the shaft to the rear wheels with the gears shifted into reverse the power travels through the transmission in a path like this we now have three sets of spinning levers for going forward and one for reverse with a gearshift lever we can shift to any set of Gears we wish but with all these spinning levers in the transmission came noise and wear experts could shift gears quietly by careful timing of the gear shift and the engine speeds but most of us made plenty of noise until New engineering developments made possible the long series of improvements that followed when we shifted gears we got a clash because the gears were not running at the same speed in other words not synchronized so Engineers set to work to develop a synchronizer the synchronizer works like a cork Twisted into the top of a bottle the cork will turn until it is so tight that the bottle turns with it Synchro mesh works the same way when we shift into second or high the synchronizer brings the gears to the same speed before they come together the drums won't let the gears shift unless they are turning at the same speed when the gears come together there is no clash and the ship is made quietly and easily in the transmission of the up-to-date automobile we have a powerful low gear to give us a strong spinning leverage in starting a fast turning motor must set the weight of the car in Motion in second speed we can change leverage to get going fast at the same engine speed with a leverage of third gear power goes directly to the rear wheels and we can go as fast as we want now every driver can shift gears at any time regardless of speed here is a hill that will give us a real chance to see how smoothly and reliably our spinning Levers work in our automobile transmission this driver is going to let her car gain a speed of 60 M hour down the hill [Music] then she will shift into second speed and bring her car easily and safely under control before it reaches the bottom of the hill [Music] the [Music]