At lunar takeoff, this tanker would mass tons, but since it is taking off in lunar gravity, it would effectively weigh only about 62 tons. The composite propellant tanks, similar to what will be used for the BFR, would probably mass only 20 tons, leaving 2 tons for the engines, 2 tons for the landing legs, and 6 tons for the rest of the structure, including the cryo-coolers, sunshade and power system. This provides a structural mass fraction of 8. At this point, we do not know the actual cost of the lunar propellants as delivered to the tanker at the lunar base, including the vehicle development costs, but finally we can compare the relative mass of the delivery propellants.
Roman technology and List of Roman watermills Roman crank handle from Augusta Rauricadated to the 2nd century. The crank-operated Roman mill is dated to the late 2nd century. The accompanying inscription is in Greek. One of the drawings of the Anonymous of the Hussite Wars shows a boat with a pair of paddle-wheels at each end turned by men operating compound cranks see above.
The concept was much improved by the Italian engineer and writer Roberto Valturio inwho devised a boat with five sets, where the parallel cranks are all joined to a single power source by one connecting-rod, an idea also taken up by his compatriot Italian painter Francesco di Giorgio.
Cranks mounted on push-carts first appear in a German engraving of Corneliszoon was granted a patent for his crankshaft in Modern Europe[ edit ] From the 16th century onwards, evidence of cranks and connecting rods integrated into machine design becomes abundant in the technological treatises of the period: Reciprocating piston engines use cranks to convert the linear piston motion into rotational motion.
Internal combustion engines of early 20th century automobiles were usually started with hand cranks known as starting handles in the UKbefore electric starters came into general use.
Make sure the gear shifting lever is in neutral position. The clutch pedal is unlatched and the clutch engaged. The brake pedal is pushed forward as far as possible setting brakes on the rear wheel.
See that spark control lever, which is the short lever located on top of the steering wheel on the right side, is back as far as possible toward the driver and the long lever, on top of the steering column controlling the carburetor, is pushed forward about one inch from its retarded position.
Turn ignition switch to point marked "B" or "M" Fifth: Test for this by pressing down on the small pin projecting from the front of the bowl until the carburetor floods. If it fails to flood it shows that the fuel is not being delivered to the carburetor properly and the motor cannot be expected to start.
See instructions on page 56 for filling the vacuum tank.
When it is certain the carburetor has a supply of fuel, grasp the handle of starting crank, push in endwise to engage ratchet with crank shaft pin and turn over the motor by giving a quick upward pull.
Never push down, because if for any reason the motor should kick back, it would endanger the operator. Note locomotive on left for size reference Large engines are usually multicylinder to reduce pulsations from individual firing strokeswith more than one piston attached to a complex crankshaft.
Many small enginessuch as those found in mopeds or garden machinery, are single cylinder and use only a single piston, simplifying crankshaft design. A crankshaft is subjected to enormous stresses, potentially equivalent of several tonnes of force.
The crankshaft is connected to the fly-wheel used to smooth out shock and convert energy to torquethe engine block, using bearings on the main journals, and to the pistons via their respective con-rods. Bearings[ edit ] The crankshaft has a linear axis about which it rotates, typically with several bearing journals riding on replaceable bearings the main bearings held in the engine block.
As the crankshaft undergoes a great deal of sideways load from each cylinder in a multicylinder engine, it must be supported by several such bearings, not just one at each end. This was a factor in the rise of V8 engineswith their shorter crankshafts, in preference to straight-8 engines.
The long crankshafts of the latter suffered from an unacceptable amount of flex when engine designers began using higher compression ratios and higher rotational speeds. High performance engines often have more main bearings than their lower performance cousins for this reason.
Piston stroke[ edit ] The distance the axis of the crank throws from the axis of the crankshaft determines the piston stroke measurement, and thus engine displacement. A common way to increase the low-speed torque of an engine is to increase the stroke, sometimes known as "shaft-stroking.
In compensation, it improves the low speed operation of the engine, as the longer intake stroke through smaller valve s results in greater turbulence and mixing of the intake charge.
Most modern high speed production engines are classified as "over square" or short-stroke, wherein the stroke is less than the diameter of the cylinder bore. As such, finding the proper balance between shaft-stroking speed and length leads to better results. Engine configuration[ edit ] The configurationmeaning the number of pistons and their placement in relation to each other leads to straightV or flat engines.
The same basic engine block can sometimes be used with different crankshafts, however, to alter the firing order. This type of crankshaft was also used on early types of V8 engines.
See the main article on crossplane crankshafts. Engine balance[ edit ] For some engines it is necessary to provide counterweights for the reciprocating mass of each piston and connecting rod to improve engine balance.
These are typically cast as part of the crankshaft but, occasionally, are bolt-on pieces. While counter weights add a considerable amount of weight to the crankshaft, it provides a smoother running engine and allows higher RPM levels to be reached.
Flying arms[ edit ] Crankshaft with flying arms the boomerang-shaped link between the visible crank pins In some engine configurationsthe crankshaft contains direct links between adjacent crank pins, without the usual intermediate main bearing. These links are called flying arms.Unlike most editing & proofreading services, we edit for everything: grammar, spelling, punctuation, idea flow, sentence structure, & more.
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In its primitive form, a wheel is a circular block of a hard and durable material at whose center has been bored a circular hole through which is placed an axle bearing about which the wheel rotates when a moment is applied by gravity or torque to the wheel about its axis, wheel and axle thereby making together one of the six simple iridis-photo-restoration.com placed vertically under a load-bearing platform.
Ford Speak: Acronyms, Definitions, and Terms. This booklet contains the Acronyms and Terms available on-line as part of the Information Management databases on the Ford Intranet. PREFACE to first edition.
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