Chapter 1: Building an Engine Flashcards
What is an engine?
An engine is a group of related parts assembled in a specific order. In operation, it is designed to convert the energy released by burning fuel into a useful form.
Define internal combustion engine.
Internal combustion means burning within. Engine refers to the device in which the fuel is burned. Fuel is the substance that is being burned. The engine converts the heat of burning fuel into useful energy.
Gasoline is made by refining _____.
(A) coal
(B) crude oil
(C) oxygen
(D) limestone
(B) crude oil (petroleum)
Since gasoline is a mixture of carbon and hydrogen, it is often termed a(n) _____.
hydrocarbon
To burn, gasoline must be mixed with _____.
(A) oxygen
(B) nitrogen
(C) argon
(D) hydrocarbons
(A) Oxygen
Define octane rating.
The octane rating indicates how well the gasoline will resist detonation (too rapid burning) in the cylinders.
Name the three grades of gasoline and their octane rating.
Regular (87), plus or extra (about 89), and premium (92-94)
Define unleaded gasoline and state why it is used in all modern cars.
Unleaded gasoline contains no tetraethyl lead.
Unleaded gasoline must be used in late-model cars because the tetraethyl lead in leaded gasoline would quickly destroy certain parts, such as the catylytic converter, that help to reduce exhast emissions.
Define tetraethyl lead.
Tetraethyl lead was a chemical fuel additive used to raise octane.
What factors affect the quality of any gasoline? How is this determined?
Many factors affect the quality of gasoline. It must pass exhaustive tests, both in the laboratory and in actual use. Basically, gasoline must burn cleanly, ignite readily, and resist freeazing or boiling. It should contain a minimum number of harmful ingredients and prevent detonation.
Where does the basic force of an engine come from?
If you break up gasoline into very tiny particles, burning is fierce. Rapid burning produces a tremendous amount of heat, which in turn causes a rapid and powerful expansion. The burning gasoline gives off energy in teh form of heat.
What is a simplified way of explaining how an engine traps the expansion of burning gasoline and converts it into motion?
If you were to spray a mixture of gasoline and air into a sturdy metal container, place a lid over the top of the container, and then light the mixture, the resulting rapid expansion would blow the lid high into the air.
This is an example of using gasoline to do work. In this case, the work is blowing the lid into the air. Obviously, a flying lid will not push a car, but the flying lid does suggest a way to convert the energy of burning fuel into useful motion.
What example does the book give of a way to convert the work done by an explosion of burning gasoline in a metal container, blowing the lid off, into rotary motion?
Imagine the setup with the container and the lid again, but this time use a rod to hook the lid to a shaft that is shaped like the one shown in Figure 1-7 below. Support each end of the shaft in bearings. Then, place a wheel on one end of the crankshaft.
Now, when the burning mixture expands and the lid is blown into the air, the shaft will be given a sharp upward push, causing the wheel to spin. You have built a very simple engine. Although this engine is not practical, it is pointing the way.
What is wrong with the simple engine and crankshaft shown in Figure 1-7 in a previous flashcard?
Many things. Let us discuss them one at a time. The lid will fly up as the burnign mixture expands. As the wheel spins, the lid will be forced down again. The lid can come back down in any position, but if the engine is to work, it must come down over the container.
Instead of putting the lid over the container, cut it so that it just slips inside. Make the container longer so that the lid can push the shaft to the top of its travel and still not fly out of the container, shown below Figure 1-8.
If you were to bolt the container and the shaft bearings so that they could not change position, you would have an engine that would spin the wheel every time yo ufired a fuel mixture.
In order to cause the wheel to spin in the proper direction, you would have to fire the mixture with the crank in a position similar to the one shown in Figure 1-8A. If the crank is in the position shown in Figure 1-8B, the lid could not fly up without pushing the crank bearing up or the container down. If it were fired with the crank in the position shown in Figure 1-8C, the wheel would spin backwards.
The mixture must be fired when the shaft is in the proper position. By studying Figure 1-8, you can see that the crankshaft changes the reciprocating motion (up and down) of the lid into rotary motion (round and round).
Name the parts you’ve developed so far in the simple engine.
block: the container
cylinder: the hole in the container, or block
piston: the lid
crankshaft: the shaft with a section bent in the shape of a crank
connecting rod: the rod that connects the crankshaft to the piston
main bearings: the bearings that support the crankshaft
connecting rod bearing: the lower bearing (the one on the crankshaft) on the connecting rod
flywheel: the wheel
Describe the process of conceptualizing fastening the parts of the engine.
Since you are going to fasten the parts so the main bearing and cylinder cannot move, it would be wise to invert your engine and place the cylinder on top. Just why this is done will soon be obvious
Make the block heavy to give it strength to withstand the pressure exerted on it by the expansion of the burning fuel. Bring it down to support the main bearings, Figure 1-9A By bringing the block out and down around the main bearings, you now have a strong unit. In Figure 1-9B, the lower block end forms a case around the crankshaft. It allows you to have two main bearings. This lower bock end is calld the crankcase.
Name the parts in the figure below.
A: Shaft
B: Bearing
C: Wheel
D: Journal
E: Rod
F: Container
G: Burning air fuel mixture
H: Lid
Descibe the reasoning behind lengthening the piston, making the connecting rod able to move, and putting a pin through a hole in the connecting rod and the piston.
Making the piston longer stops it from tipping sideways in the cylinder. In order to avoid a piston that is too heavy, make it hollow. See Figures 1-10 and 1-11.
If the piston is to travel straight up and down and the connecting rod is to swing back and forth in order to follow the crank, it is obvious that the connecting rod must be able to move at the point where it is connected to the piston, Figure 1-12.
Now, drill a hole through the upper end of the connecting rod. Also drill a hole through the piston. Line up the two holes and pass a pin through them. This pin is called a piston pin, or wrist pin. It is secured in various ways. See Figure 1-13.
Expain redesigning the cylinder head to be removeable.
Redesign your cylinder block and make the top removeable. You will call this removeable top a cylinder head. It will be fastened in place with bolts or studs and nuts, Figure 1-14.
Explain making fuel intake and exaust passages, in addition to making the cylinder head removable.
Making your clinder head removeable has not yet solved all of the problems. You cannot take the head off and put it on each time the engine fires. Now, make the head of much thcker metal and make two passages, like those shown in Figure 1-15. This will give you one passage to take in the fuel mixture and another passage to exhaust it. These passages are called valve ports, Figure 1-16.
Explain the design process for the valves.
The next logical step is to provide a device to open and close the ports. If the ports are left open and teh burning fuel mixture expands in teh combustion chamber, teh expanding, burning gases will blow out through the openings and fail to push the piston down.
This port controle device, or valve, will have to be arranged so that it can be opened and closed when desired. Place a valve in each opening. This can be done as shown in Figure 1-17. When the valve sits on its valve seat, it seals the opening. The valvese are held in position by a hole bored through the cylinder head. This hole is called a valve guide because it guides the valve stem up and down in a straight line.
You will also install a spring, spring washer, and keeper. The spring is necessary to keep the valve tightly closed against its seat. When the valve is opened, the spring will close it again. Arrange your spring, washer, and keepers as showin in Figure 1-18. The valves now provide a satisfactory method of opening and closing the ports.
