thread507-327848
I wonder why there is no follow-up on this discussion.
I have been reading the same book by Arya, O'Neil and Pincus. Same question as Egnorant had came up. Nobody seemed to have addressed it. At least not any that I can find.
In Example 2 of Chapter 6, which addresses the design of the concrete block foundation of a centrifugal machine, in Table 6-3, the calculations of Magnification facor M and Tranmissibility factor Tr used formulae for "constant force excitation" from Table 1-4. Shouldn't the formulae for "rotating mass-type excitation" be used instead? More confusingly, even though the Ms were calculated using formulae for "constant force excitation" from Table 1-4, the results for vibration amplitude Z and X came up to be matching the results of using Ms calculated through the formulae for "rotating mass-type excitation".
Another important point to be noted is that, using the numbers of Example 2 and the formulae of Table 1-4 for "rotating mass-type excitation", the Transmissibility factors are much larger than 1.0 as r = w/wn becomes much larger than 1. For example, r = w/wnv = 6949/1041 = 6.7, which gets the Trv = 11.4. That is a transmissibility factor much larger than 1.0! Does that mean the formulae for calculating the transmissibility factor of "rotating mass-type excitation" per Table 1-4 is wrong? That the formula should be the same as that for "constant force excitation"?
Some clarification would be greatly appreciated.
I wonder why there is no follow-up on this discussion.
I have been reading the same book by Arya, O'Neil and Pincus. Same question as Egnorant had came up. Nobody seemed to have addressed it. At least not any that I can find.
In Example 2 of Chapter 6, which addresses the design of the concrete block foundation of a centrifugal machine, in Table 6-3, the calculations of Magnification facor M and Tranmissibility factor Tr used formulae for "constant force excitation" from Table 1-4. Shouldn't the formulae for "rotating mass-type excitation" be used instead? More confusingly, even though the Ms were calculated using formulae for "constant force excitation" from Table 1-4, the results for vibration amplitude Z and X came up to be matching the results of using Ms calculated through the formulae for "rotating mass-type excitation".
Another important point to be noted is that, using the numbers of Example 2 and the formulae of Table 1-4 for "rotating mass-type excitation", the Transmissibility factors are much larger than 1.0 as r = w/wn becomes much larger than 1. For example, r = w/wnv = 6949/1041 = 6.7, which gets the Trv = 11.4. That is a transmissibility factor much larger than 1.0! Does that mean the formulae for calculating the transmissibility factor of "rotating mass-type excitation" per Table 1-4 is wrong? That the formula should be the same as that for "constant force excitation"?
Some clarification would be greatly appreciated.
