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Who's got the formula? centrifugal force applied - 9/30/2012 9:56 PM   
frets24


 

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From: charlotte, NC, USA
Status: offline 		Anyone know the formula to figure how much force in lbs or ounces is acting on a 1.5gram wieght spinning at 7k rpm in a 1.5"(4cm)radius? What I'm really trying to determine is; how much does this part think it weighs at speed. I have found some calculators but the answers are outside my scope of interpretation or understanding...what the heck is kip?

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RE: Who's got the formula? centrifugal force applied - 9/30/2012 10:53 PM   
allans


 

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Status: offline 		((The Mass times the Tangential velocity (squared) )divided by the radius.

This is the force acting on the mass .

You are going to have to change the rpm into tangential velocity. Watch the units in enter calculation . Make sure they are all the same.

Also remember that weigth is mass of the object times the force ( g) of gravity.

Good luck.

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RE: Who's got the formula? centrifugal force applied - 10/1/2012 12:19 AM   
frets24


 

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Status: offline 		Thanks allans,

I know this probably wasn't the right place to pose this question but it is the BEST place I know to find the people who know about these things.

The basis of the query is a problem in the ASP 5 cyl RC engine. It uses e-clips internally to hold the rods to the crankshaft and they seem to have a bad habit of coming loose. My theory is that the clips are rotating to an orientation that causes them to fly free due to the cent. force overcoming their ability to retain their hold on the pin.

If I have figured this correctly they are trying to resist a 7.24lb "pull" at 7k...much more than is required to pop them off the pin.

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RE: Who's got the formula? centrifugal force applied - 10/1/2012 12:32 AM   
Bozarth


 

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Status: offline 		7000 rpms around a circle with a 1.5" radius = 92 ft/sec

As stated above: a=velocity squared / radius

a = 67712 ft/sec2

divide gravity out of the equation to get g's (so we have a feel for what we are talking about)

Answer: your little 1.5 gram weight is pulling 2085 g's.

Your 1.5 gram weight feels like 3.127 kgs.

1 kg = 2.2 lbs

So, your 1.5 gram weight feels like 6.9 lbs.

But then again, I have been out of school for a long time.

Kurt



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RE: Who's got the formula? centrifugal force applied - 10/1/2012 12:54 AM   
frets24


 

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Status: offline 		Bozarth,

You are the MAN!!! Thank you so much.

I had come up with @7.23lbs so it's nice to know I wasn't too far off in all of my cross converting weights and measures.

Link to current discussion about the clips

http://www.rcuniverse.com/forum/m_6767296/anchors_11246305/mpage_47/key_/anchor/tm.htm#11246305

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