本帖最后由 動靜之機(jī) 于 2014-7-4 00:22 編輯 1 q. E- r) o) L) p$ O
caucsaa 發(fā)表于 2014-7-3 21:33 ![]()
G: ^: e" _, b1 p$ y嗯，我們討論的問題就是需要多大拉力，算出一個值容易，但是不知道真實情況。誰有真實測量數(shù)據(jù)？
* F$ ] K4 J1 d- a! q* e俺模糊了滾動摩擦系數(shù)和滾阻系數(shù)概念，抱歉。2 `- m1 x4 Q( p
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找了一圈，還真沒有找到有文字提到拉飛機(jī)究竟要多大勁的 ，
2 h- G# w7 [7 j0 s0 l9 _+ o" I9 t倒是有幾個關(guān)于汽車輪胎阻力數(shù)據(jù)的。好在從用輪子的角度看是- O' b; ^; j0 z' D. ]0 ^
一回事，不妨認(rèn)為是"小尺寸模型"吧。( q" W" L0 D$ H) N$ t
5 {# Z; }. |6 P [1 D2 L% rhttp://auto.howstuffworks.com/tire4.htm 這里面提到：
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+ |8 g2 l, s" y& j$ a| Tire Type | Coefficient of Rolling Friction | | Low rolling resistance car tire | 0.006 - 0.01 | | Ordinary car tire | 0.015 | | Truck tire | 0.006 - 0.01 | | Train wheel | 0.001 |
該文還舉例說一個4000磅（1.814噸）的汽車，采用滾阻系數(shù)0.015的輪胎，滾阻60磅（27.215公斤）。; j) _2 `6 x, ]/ O
車速75碼（每秒33.528米）時，所需損耗功率12馬力，這些能量，大部分作用在輪胎（變形發(fā)熱唄），其余在路面。0 I' I" J6 P6 Y/ D6 O+ u
! J) x3 z) m( s0 z& X8 o/ nhttp://hpwizard.com/tire-friction-coefficient.html 這里面有個自動表格。6 i$ X" w3 \- x5 D5 K
通過手動選擇輪胎種類和路面類型，自動給出靜摩擦系數(shù)和滾阻系數(shù)。6 C" {2 d7 X1 K9 J. N- T' `, q7 l
可見在混凝土路面上，滾阻系數(shù)：# g' T% g5 | q) _- q0 I* h2 ]6 m
自行車胎可低達(dá)0.004
& @5 ^5 I6 q% P4 a: j" p牽引胎也不過才0.03 （其靜摩擦系數(shù)高達(dá)4.0，說明就是來抓地的）, A( ^# ~( o6 `
0 Q+ \, Z- d+ J2 g+ ohttp://hyperphysics.phy-astr.gsu.edu/hbase/frict2.html#plo 這里面有段話：
9 ~4 q+ s4 d5 NRolling FrictionA rolling wheel requires a certain amount of friction so that the point of contact of the wheel with the surface will not slip. The amount of traction which can be obtained for an auto tire is determined by the coefficient of static friction between the tire and the road. If the wheel is locked and sliding, the force of friction is determined by the coefficient of kinetic friction and is usually significantly less. Assuming that a wheel is rolling without slipping, the surface friction does no work against the motion of the wheel and no energy is lost at that point. However, there is some loss of energy and some deceleration from friction for any real wheel, and this is sometimes referred to as rolling friction. It is partly friction at the axle and can be partly due to flexing of the wheel which will dissipate some energy. Figures of 0.02 to 0.06 have been reported as effective coefficients of rolling friction for automobile tires, compared to about 0.8 for the maximum static friction coefficient between the tire and the road. 。。。輪胎在路面的最大靜摩擦系數(shù)0.8，（相應(yīng)的）滾阻系數(shù)一般在0.02-0.06之間。; f; b( B: w2 A, U/ y5 v
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這三組數(shù)據(jù)，和俺在6樓（0.02）和18樓（0.06）的的數(shù)據(jù)基本相近。
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因此，拉動飛機(jī)的所需的水平力約等于0.02-0.06倍的飛機(jī)重量。 2 P Q5 Y) j, h3 b1 ?7 K
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