balancing a fan

[lahcen]

I want to know the formula to calculate the two masses in position 72° and 144° (they found 1.5gr and 1gr by the calculator)
please see the file (page 11) to understand my meaning

 

[GregLocock]

It says on the page. A vector diagram. So you can use geometry or complex maths.

Cheers

Greg Locock


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[GregLocock]

So, you need to create two vectors of unknown magnitude, one at 72 degrees and one at 144 degrees, that add to give a mag 2 vector at 100 degrees. It's fairly basic geometry, cos and sin will get you there.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[lahcen]

Thanks GregLocock for your answer,
But I don't find the same result( 1.5gr at 72° and 1gr at 144°).

 

[GregLocock]

Show your working

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[lahcen]

Thanks GregLocock.

 

[electricpete]

There are loads of spreadsheets and calculators to solve this exact problem (which as you no doubt know comes up in balancing).

Rather than posting a link to a calculator, I'd rather post my notes about the trigonometry to figure it out yourself. Actually that's my own preference when possible (that way I don't get fooled by someone else's spreadsheet that has an error or doesn't make the assumptions/conventions / notations clear).

As Greg says there are other ways to solve it if you prefer. I think most other ways involve solving 2 equations in 2 unknowns each, this approach has 2 equations in one unknown each, so m1 and m2 can be solved separately (easier algebra).

 

[lahcen]

Thanks electricpete, I catch the idea