topic Re: Is there anything wrong with calculation of key in Design Accelerator? in Inventor Forum

Is there anything wrong with calculation of key in Design Accelerator?

Anonymous — Thu, 01 Mar 2018 19:02:14 GMT

Does anybody know if there is something missing in calculation of dmin for keys in Design accelerator?

According to formula in Engineering manual, the conversion factor feet to inches is missed,

In the example, torsion is given in lbf·ft and shear stress is given in psi (lbf/in2)...with Ka=Kf=1 and Sv=3.If I replace these values in proposed formula, dmin is not 0,754 in...

Thank you very much

Re: Is there anything wrong with calculation of key in Design Accelerator?

Pavel_Holecek — Mon, 05 Mar 2018 10:39:21 GMT

Hello,

sorry you are having problems with Key Generator. I checked the formulas and there is an issue with units conversion 'ft' to 'in'. I add a new issue to our tracking system.

Thank you for pointing that out

Re: Is there anything wrong with calculation of key in Design Accelerator?

Anonymous — Mon, 05 Mar 2018 10:52:43 GMT

Thank you for the quick answer. I was becoming crazy.
I suppose that this error does not affect the calculation of key length. Could you please confirm this point??
Thanks again

Re: Is there anything wrong with calculation of key in Design Accelerator?

Pavel_Holecek — Mon, 05 Mar 2018 13:54:22 GMT

Unfortunately it has impact on minimal Length as well. The formula for Lmin is calculated based on a Force and the Force is calculated from the Torque.

I tried a small workaround in this calculation and when you increase Torque = 350*12 then you can see right result. I hope that we will fix it soon.

Re: Is there anything wrong with calculation of key in Design Accelerator?

Pavel_Holecek — Mon, 05 Mar 2018 14:44:22 GMT

It has been logged as INVGEN-13818 to our internal tracking system.

Re: Is there anything wrong with calculation of key in Design Accelerator?

Anonymous — Mon, 05 Mar 2018 16:10:43 GMT

OK, thank you very much. I will advise my colleagues about the mistake.
I use to compare Design Accelerator results with theoretical ones (using traditional formulae) and in that case, neither dmin nor Lmin fitted with theory.
I will try what you propose, increasing x12 the torque in order to get the right dmin and Lmin. (If I introduced Powerx12 should be the same...)
Best regards,
Cristina