The Mechanical Principles of Engineering and ArchitectureLongman, Brown, Green and Longmans, 1843 - 627 من الصفحات |
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طبعات أخرى - عرض جميع المقتطفات
عبارات ومصطلحات مألوفة
a₁ angle of resistance angular velocity arch axis beam body bordering upon motion capstan centre of gravity circumference co-efficient compression cord corresponding crank crank arm cubic foot curve cylinder deflexion determined dimensions distance ditto driving element elongation epicycloidal equal equation equilibrium evident exceedingly small extrados formula friction given horizontal hypocycloidal inclination inertia intersect involute lamina length limiting angle line of centres line of resistance load machine modulus moment of inertia neutral line observing obtain P₂ parallel passing perpendicular pitch circle plane point of application point of contact portion position pressure P₁ pressures applied pulley radius repre respect resultant revolution revolve rupture S₁ screw space stability supposed surfaces of contact taken to represent tension tion tooth U₁ U₂ unguent vertical vis viva voussoirs wall weight whence it follows whilst whole
مقاطع مشهورة
الصفحة 138 - When no unguent is interposed, the friction of any two surfaces (whether of quiescence or of motion) is directly proportional to the force with which they are pressed perpendicularly together ; so that for any two given surfaces of contact there is a constant ratio of the friction to the perpendicular pressure of the one surface upon the other. Whilst this ratio is thus the same for the same surfaces of contact, it is different for different surfaces of contact. The particular value of it in respect...
الصفحة 85 - The moment of inertia of a cylinder about an axis passing through its centre of gravity, and perpendicular to its axis of symmetry.
الصفحة 140 - The coefficient for the unguent tallow is the same, except in that of metals upon metals. This unguent appears to be less suited for metallic surfaces than the others, and gives for the mean value of its coefficient under the same circumstances -10.
الصفحة 142 - ... motion is exempt. This variation does not appear to depend upon the extent of the surface of contact; for, with different pressures, the ratio of the friction to the pressure varied greatly, although the surfaces of contact were the same. The slightest jar or shock, producing the most...
الصفحة 10 - ... must be equal to the sum of the moments of those which tend to turn it in the opposite direction about the same axis.
الصفحة 8 - The sum of the moments of a number of coplanar forces round any point is equal to the moment of their resultant about that point.
الصفحة 551 - Thus it follows, from the preceding condition and this, that the strongest form of section in a cast-iron beam is that by which the material is collected into two unequal flanges joined by a rib, the greater flange being on the extended side, and the proportion of this inequality of the flanges being just such as to make up for the inequality of the resistances of the material to rupture by extension and compression respectively. Mr. Hodgkinson, to whom this suggestion is due, has directed a series...
الصفحة 140 - VIII, leads to the following remarkable conclusion, easily fixing itself in the memory, that with the unguents, hogs* lard and olive oil interposed in a continuous stratum between them, surfaces of wood on metal, wood on wood, metal on wood, and metal on metal, when in motion, have all of them very nearly the same co-efficient of friction, the value of that co-efficient being in all cases included between 0,07 and 0,08, and the limiting angle of resistance therefore between 4° and 4° 35'.
الصفحة 607 - Upon hard macadamized, and upon paved roads, the traction increases with the velocity: the increments of traction being directly proportional to the increments of velocity above the velocity 3-28 feet per second, or about 2J miles per hour.
الصفحة 266 - B, are generated by a circle whose diameter is equal to the radius of the pitch circle of B. The hypocycloidal flanks of the teeth on B thus become straight lines (Art.