Mechanical engineering question – Rotating masses

[BertVK]

Let's drop the subject please

Hey, I just did a quick calculation using Q's formula and then fed the same data into Heli Calc, and guess what?? The results match! Incidentally, the raptors blades exert a force of 112.2Kg on the blade grips, that's quite a bit more than I weigh! And it's all held back by a little M4 bolt [img]/ubbthreads/images/graemlins/crazy.gif[/img]

[BertVK]

Hmmmm, I did the calculation with 80gr GF blades at 1300 rpm and got 400N, that's about 40kg.
Are you sure your are not mixing N, kg and kgF (kilogram force, another notification for Newton)?

I used 116g (stock wooden blades) and an rpm of 1550 (as recommended for normal flying in the manual) and got a force of 1100N. My conversion table says 1N = 0.1019716Kg force. What's the difference between Kg and KgF?

[BertVK]

Using the apple's law, euh excuse me, Newton's law
F = m * a
you can see that
m = F / a

a = 9.8067 m/s²(accelleration on earth)

My memory is lapsing at the moment on how they go to kgF, but the relation between the numbers you stated is a! 1 / 9.8067 = 0.1019716
So I guess they liked to express a force using kilogram is a measure, but had to take accelleration into account.

Anybody of the old school with a better explanation?

One day when I have time (like that will ever happen) I will pull out my great book of physics and do some revision, but for now your explanation makes sense.

[BertVK]

[ QUOTE ]
One day when I have time (like that will ever happen) I will pull out my great book of physics

[/ QUOTE ]

You have a copy of Newtons work??????

[gonper]

The diference betwing Newtons and Kilograms is that Newtons are a force mesuarement and kilogrames are a mass mesurement.
So the force it will be always in newtons.
And the mass in Kg.

But, Weight is the force that a certain mass is atracted by the earth.
then it easier to understand KgF that is the force that a Kg mass is atracted by the earth, thats why some times to make the things easier and understandable we express it in Kg the force...
For example when you talk about servos...
Or blade forces in blade holders...

About the screws that hold the blades don't worry, in the way they are mounted they can resist over 100 kg if you want I can make you the exact calculations... [img]/ubbthreads/images/graemlins/tongue.gif[/img]