超深數學提. 計時速

回復 keithlaw 的帖子

That's why I give C-Hing OzAndy 99.9 marks!!

iPhone 有個 Apps 叫 "Ratio Calc" , 對應時下大部份車種,
輸入 Pinion/Spur , 可計算到齒比同摩打轉一圈可行走長度

登錄/註冊後可看大圖

回復 smallwhite1234 的帖子

I think you are right
we have same answer

回復 smallwhite1234 的帖子

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

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！

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)??

回復 fatchickterian 的帖子

個apps 叫 Ratio Calc, 我都有裝, 哈哈

回復 hinwong 的帖子

thanks C-Hing!!

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.

well that only the 樓主 knows

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

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.

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.

回復 keithlaw 的帖子

ha ha yeah!!

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

回復 OzAndy 的帖子

Yes, the different result due to different wheel diameter

回復 fatchickterian 的帖子

Agree. It's very useful !

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

回復 hinwong 的帖子

  Is it an optical sensor?

明白！謝謝！去諗諗，也是一種娛樂！

回復 hinwong 的帖子

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