Excel and Math gurus formula help

geek_dino7, Sep 5, 8:59 pm
I am hoping to create an excel formula (well not me as it way beyond my capabilities but hoping someone can do it for me :) ) to be able to work out the distance between two shaft's with different sized pulleys (which could change) on each shaft along with a known belt length which could change.
i.e. pulley 330mm
pulley 120mm
belt length 1499mm
= 380mm centres between shafts

Currently i have found a formula that if i know both pulley sizes and the centres between shafts it will give me the belt length as below:

lb = (dm ?

geek_king1, Sep 5, 10:18 pm
literally, stick each of these values into a seperate cell - df, dm, ?


geek_ross1970, Sep 5, 10:32 pm
For a start, simplify your notation:
L = length of belt
D = diameter of large pulley
d = diameter of small pulley
c = centers

geek_ross1970, Sep 5, 10:53 pm
L = (pi/2)(D+d) + 2c + ( 2(D-d) / (4c) )

. is to me, more "readable".

geek_emmerson1, Sep 6, 12:01 am
Did you know that if you select a cell range (even a single cell), you can give it a meaningful name?

Select your cell, and put the name 'D' for instance, in the drop-down box just above column 'A'. Now you can type your nice formula.

geek_dino7, Sep 6, 10:07 pm
Thanks everyone, I'm going to have a go at the weekend by following your help - I'm barely intermediate on excel infact i'm bordering on beginner ;)

geek_ross1970, Sep 6, 10:59 pm
Would be a simple function in javascript you could run in your browser console if you wanted to flag using excel.

geek_dino7, Sep 7, 6:50 am
thats not simple for me Ross - yes it would be handy to have it on my phone in either excel or on a browser

geek_ross1970, Sep 7, 9:14 am
There's any number of webpages that calculate v-belt length for you. Bookmark one you like.

geek_wotz_it_2_ya, Sep 7, 5:04 pm
But now change it to solve for c, which is the question. Too hard for Friday afternoon

geek_ross1970, Sep 7, 7:04 pm
C = [??? { (L - R ?

geek_ross1970, Sep 7, 7:53 pm
Not really. Visualize 2 triangles, top and bottom ( bottom inverted ), where the hypotenuse of each, is the belt running between the pulleys,
and the bases of the triangles are parallel to C, and obviously equal to C.
Subtract from L, the belt that curls around the outside of the pulleys .
( L - R ?

geek_dino7, Sep 7, 10:58 pm
Although as above i would prefer the centres knowing both pulley/flywheel diameters and the belt size - not found a site that does that.

geek_ross1970, Sep 9, 7:05 pm
Yip well there's the eq in #11. Go for it .

Regarding using the v-belt length calculators online. Altho they are calculating belt length, you can still simply put in the 2 pulley sizes, put in a random center length to generate a starting belt length, then you just adjust the centers value up or down until the belt length shown matches the belt length you have. And you there u have the center value you wanted.

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