超深數學提. 計時速 - RC EVOLUTION - 遙控工房 - 香港RC遙控車討論區

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2011-5-17 02:31 上傳

預先輸入車轆直徑為 63mm,
再輸入 Pinion:22T / Spur: 80T , 齒比為 6.91
計到摩打轉一圈可行走 28.65mm

現在要計皮帶行 1300rpm, 時速幾多:
皮帶 522T(174T), 皮帶牙 20T (174T / 20T = 8.7)
皮帶牙轉速 = 1300rpm x 8.7 =11310rpm
皮帶牙轉速=大減齒轉速,
大減齒 / 摩打齒 = 80T / 22T = 3.63
摩打轉速 = 11310rpm x 3.63 = 41055rpm
摩打轉一圈行 28.65mm
28.65mm x 41055rpm = 1,176,225mm per min = 1.17Km per min = 70.2km/h

唔知有冇計錯, 有錯請指正, 謝!

作者: OzAndy 時間: 2011-5-17 03:20
回復 smallwhite1234 的帖子

I think you are right

we have same answer

作者: fatchickterian 時間: 2011-5-17 07:45
回復 smallwhite1234 的帖子

woh, this is a very cool app, I need to download it, thanks c-hing!!

作者: chiupolini 時間: 2011-5-17 10:08
smallwhite 1234 Ching,

我明白你第一部份的計算，但不是很明白為什麼在第二部份要用一個假設 "現在要計皮帶行 1300rpm, 時速幾多:"
皮帶有多少T，是在乎Spur pulley 和相對的 axle pulley 距離有多遠。和速度應該是沒有關係的。就像單車一樣，前後齒牙有多遠，單車鏈就要有多長，但卻不會影響速度一樣。
會影響速度的，應該是 spur gear, pinion gear, belt transmission pulley gear 及axle spur pulley gear. 你在第一部份程式中，後兩者的比應該是1.90025. 所以齒比是 6.91。
所有的motor都有kv rating記於說明書內。比如kv 是7,900，motor的最高轉數便是乘7.2 volt (assuming 2 x lipo). 即是 56,880 rpm. 為什麼要用一個「皮帶行 1300rpm」的假設去找出馬達的轉數呢？請賜教！

作者: fatchickterian 時間: 2011-5-17 11:11
回復 chiupolini 的帖子

C-Hing chiupolini, I think you better read the question before you read somebody's answer.

the belt speed was given as 1300rpm.

The question was: if belt speed was 1300rpm, what is the equivalent wheel speed (car speed)??

作者: hinwong 時間: 2011-5-17 11:19
回復 fatchickterian 的帖子

個apps 叫 Ratio Calc, 我都有裝, 哈哈

作者: fatchickterian 時間: 2011-5-17 11:20
回復 hinwong 的帖子

thanks C-Hing!!

作者: chiupolini 時間: 2011-5-17 11:35
回復 fatchickterian 的帖子

C-Hing fatchikterian,

Thank you. I did read the question. But if you read carefully what my question, which was why ask this question in the place? Normally when we want to find out how fast a car can run, we refer to the maximum speed, which will depend on the motor and the battery one uses. Why ask a question "How fast the car can run IF the leather belt is running at 1,300 rpm?". Why not "1,000 rpm, 1,400 rpm, but 1,300 rpm". What is the significance of this? Is that the maximum tolerance of the belt or what? Can one effectively measure the belt's revive rate? And why we need to do it? That is why I asked my own question.

作者: fatchickterian 時間: 2011-5-17 11:42
well that only the 樓主 knows

Maybe he's got a sensor to measure the belt speed or something!!

作者: keithlaw 時間: 2011-5-17 11:48
本帖最後由 keithlaw 於 2011-5-17 11:49 編輯

Chill out guys. Let's take this question as a math problem with limited known variables.

Just relax and play with the numbers.....

Questions in Exam are the same thing. Teachers always design questions which are totally meaningless or ask in a opposite way. This is in fact trying to test students their way of thinking (their logic). So, don't take it too serious.

作者: chiupolini 時間: 2011-5-17 11:48
回復 fatchickterian 的帖子

May be. But if 樓主 was just asking the question for fun, then my apology for being superfluous in my comments. I was just being curious.

作者: fatchickterian 時間: 2011-5-17 11:56
回復 keithlaw 的帖子

ha ha yeah!!

作者: hinwong 時間: 2011-5-17 12:15
回復 chiupolini 的帖子

因為我用緊mt4支控, 個rpm sensor 又勁難裝, 我只係裝到起條belt 上面...佢check出黎, 係1300rpm...所以咪咁law...哈哈

作者: smallwhite1234 時間: 2011-5-17 12:17
回復 OzAndy 的帖子

Yes, the different result due to different wheel diameter

作者: smallwhite1234 時間: 2011-5-17 12:17
回復 fatchickterian 的帖子

Agree. It's very useful !

作者: smallwhite1234 時間: 2011-5-17 12:22
回復 chiupolini 的帖子

正常要計車速, 係應該用你既算式去計,
因為純粹係樓主提出黎既問題.
Just for fun 而已

作者: smallwhite1234 時間: 2011-5-17 12:28
本帖最後由 smallwhite1234 於 2011-5-17 12:28 編輯

回復 hinwong 的帖子

Is it an optical sensor?

作者: chiupolini 時間: 2011-5-17 12:28
明白！謝謝！去諗諗，也是一種娛樂！

作者: fatchickterian 時間: 2011-5-17 12:31
回復 hinwong 的帖子

oic, so which part is the sensor suppose to be sensing? the spur or the pinion gear??

作者: smallwhite1234 時間: 2011-5-17 12:35

作者: hinwong 時間: 2011-5-17 12:41

fatchickterian 發表於 2011-5-17 12:31

登錄/註冊後可看大圖

回復 hinwong 的帖子

oic, so which part is the sensor suppose to be sensing? the spur or the pinion ...

應該係, 不過要裝到果塊野, 企起度,真係超難....

作者: singlau714 時間: 2011-5-17 13:17
本帖最後由 singlau714 於 2011-5-17 13:18 編輯

回復 fatchickterian 的帖子

All these factors are reflected in the measured revolutionary speed of belt (1300 rpm).
Yes, the power supplied by the motor are lost due to all the factors you mentioned. And this will reduce the final speed of the car. But these are all reflected in the measured speed, whether in the car or in the belt.
They are discussing a speed conversion question here (more or less a unit conversion), not really an Energy conversion question that you learnt in yr high school physics.

作者: singlau714 時間: 2011-5-17 13:24
回復 buzzybee82 的帖子

No need. Because friction helps to turn the wheels and keep the car moving forward. Without friction, the wheels will slip... and all the calculations will be useless.
Air resistance will reduce the speed. However, this factor is reflected in the measured speed of belt already. Power supply from motor is lost, and it reduces the final speed of the whole transmission chain as a result.

作者: singlau714 時間: 2011-5-17 13:32
本帖最後由 singlau714 於 2011-5-17 13:35 編輯

回復 hinwong 的帖子

This may help. Let's define a few variables first:

G = Gear teeth on yr Diff (e.g. 38T)
B = Belt teeth on yr belt (e.g. 522T)
D = diameter of yr wheel with tyre on ( in mm)
Pi = 3.1416
W = measured revolutionary speed of belt (in rpm)
V = speed of car (in km/h)

V = Pi x D x W x (B/G) x (60/1000000)

The final gear ratio plays no role in yr question. That's related to the conversion between motor's rotation and wheels' rotations.

p.s. Measured speed of wheels = Actual speed of car (unless the tyre slips)

作者: fatchickterian 時間: 2011-5-17 13:46
回復 singlau714 的帖子

Sorry no dis-respect, but could you please explain it again in chinese!!

作者: singlau714 時間: 2011-5-17 13:52
回復 fatchickterian 的帖子

http://translate.google.com/

作者: fatchickterian 時間: 2011-5-17 14:17
回復 singlau714 的帖子

ok the goole translator was useless!!

After reading your comment a couple of times (Sorry on dis-respect again!!), I think what you're trying say is that, the measurement of the speed (on the belt) has already included lost(s), so the final result should have already included all the lost(s).

And sorry, I must have missed out my unit conversions during high shool!! (did'nt pay attention until uni ha ha)

作者: singlau714 時間: 2011-5-17 14:33
回復 fatchickterian 的帖子

Yes that's what I mean. btw, u can use the word "loss" to replace yr "lost(s)".
Modified from google translator:

所有你所提到的因素都反映在皮帶的測量速度（1300轉）。
是的，由 Motor 的能量轉換將有能量丟失, 這將減少最終車的速度。但這些均反映在測量速度，無論是在汽車速度或在皮帶速度。
他們正在有討論一個速度轉換問題（或多或少是單位轉換），而不是一個真正的能量轉換問題，和你高中物理學到的不同。

作者: fatchickterian 時間: 2011-5-17 14:43
回復 singlau714 的帖子

oooh, thank you for the conversion and the grammar lecture!!

作者: fatchickterian 時間: 2011-5-17 16:21
回復 singlau714 的帖子

Just because I love my energy and your knowledge is beyond my high school physics, it leads to my next question (sorry!). So you saying to measurement of speed on the belt has already content lost factors. How about anything after the belt? like the diff pulleys, is there any sound on the pulleys, is there any heat as well?? if there are sound and heat, does it mean there are "losses" as well?? I know these questions can go on and on. That's why I said earlier on "the factors are never clear"

作者: OzAndy 時間: 2011-5-17 17:28
回復 fatchickterian 的帖子

it can be anything that you can think of. Limitation is that the sensor and the object to be tested must be within 1 mm.
I prefer to check the RPM of the spur gear.

作者: OzAndy 時間: 2011-5-17 17:39
回復 fatchickterian 的帖子

let us put it this way.
if there are no energy lost, the belt would have spin faster > 1300 RPM
Because of the energy lost that you have mentioned, the belt turned at 1300 RPM only

Energy input into the car = mechanical energy of car (belt spin at 1300 RPM) + energy lost ( sound, vibration , heat , etc)

作者: tt01E 時間: 2011-5-17 17:50
本帖最後由 tt01E 於 2011-5-17 17:51 編輯

hinwong 發表於 2011-5-15 23:25

登錄/註冊後可看大圖

sakura s
22t + 80t 大減, 齒比等於6.91
皮帶牙 20t (原裝)

Diff pulley teeth number/center pulley teeth number=a
spur gear teeth number/motor gear teeth number=b
motor rotation speed=c (in rpm)
Wheel circumference=d (in metre)
c/b=e
e/a=f
f*d=g
g/60=speed (m/s)

作者: fatchickterian 時間: 2011-5-17 19:17
回復 OzAndy 的帖子

Ha ha ha 99.99 marks because there is no 100 markd for this type of answer ha ha

Sorry if I have offended anyone, just my area of interest, and can help putting my 5 cents worth in!! Thanks for your discussions!!

作者: OzAndy 時間: 2011-5-17 19:28
回復 fatchickterian 的帖子

never mind la.
anyone contribute a little bit, so that everyone can learn something from it

作者: chiyuen 時間: 2011-5-17 23:47
用雷槍測試最為準確,???

作者: hinwong 時間: 2011-5-17 23:53
回復 chiyuen 的帖子

要問差人借....

作者: yiuli2003 時間: 2011-5-18 16:58
是不是行車轉數（1300轉）

作者: hinwong 時間: 2011-5-18 17:04
回復 yiuli2003 的帖子

皮帶轉數..

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