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Offline harry bee  
#1 Posted : 22 February 2020 14:30:47(UTC)
harry bee

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I've read some issues with the use of revolutions in the past, and saw it got modified.

I have however a problem using it in a formula syntax.

The outcome of the calculation is not right in my case.
I can't see where I'm going wrong.
Answer should be 35.03Nm.


powercalcwrong.sm (5kb) downloaded 48 time(s).

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Offline Jean Giraud  
#2 Posted : 22 February 2020 15:49:22(UTC)
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Sorry, my understanding stops here.

RPM.PNG
Offline mkraska  
#3 Posted : 22 February 2020 17:56:57(UTC)
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This is a very common problem for beginners with SMath Studio. Searching for "frequency angular velocity" in the forum shows a lot of entries.

You expect rpm being a unit of frequency (count of events per time). rpm means full rotations (the event) per minute (the time). Angular velocity, in contrast to this, is angle per time. The common factor 2pi comes from a full revolution being 2pi radians.

In SMath Studio, rpm is understood as angular velocity. The bug is that you find this unit in the category "frequency". Should be "Angular velocity". Another bug is that if you display the value of something being given in rpm or rad/s, you get the unit Hz by default, which is wrong for whatever rate of dimensionless quantities except for counting events.

The default should be 1/s, then it is left to the user to think of what 1 stands for.

As rpm is defined as angular velocity in SMath Studio, you can directly use n.m for calculating the torque

powercalcwrong.png
Martin Kraska

Pre-configured portable distribution of SMath Studio: https://smath.com/wiki/SMath_with_Plugins.ashx
Offline harry bee  
#4 Posted : 23 February 2020 05:53:42(UTC)
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Thanks
This is what I kind of suspected because the error was in the 60/2*pi factor.
Just couldn't get my head around it.

Now it's clear.
It probably is the effect of 30 years of engineering with rpm as revolution per minute chiseled in my brain.
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