How to position vibration isolators for a generator set?

[mfadzil]

Hi all,

I have questions, is there any guideline on positioning vibration isolators beneath a generator set skid?

Lets say the generator package weight is 65mT, so I place 10 points of vibration spring. How to positioning the vibration isolator?

Can anyone guide me the formula to calculate the reaction of the isolator point?

"As the generator has 10 points of isolator, so I did divided it to 4 portion to get Ra, Rb, Rc, Rd and Re. For example;
Ra = P1b1/L1 -----1
Rb1 = P1a/L1 ------2
--------------------
Rb2 = P2c1/L2 -----3
Rc1 = P2b2/L2 -----4
--------------------
Rc2 = P3d1/L3 -----5
Rd1 = P3c2/L3 -----6
--------------------
Rd2 = P4e/L4 ------7
Re = P4d2/L4 -----8
--------------------

Ra + (Rb1+Rb2) + (Rc1+Rc2) + (Rd1+Rd2) + Re = 0

Ra, Rb1, Rb2.. is the reaction, P1, P2, P3.. is the forces.
a,b1,b2.. is the position of P1,P2,P3.. from Ra,Rb2,Rc2..
L1,L2.. is the length of Ra to Rb1, Rb2 to Rc1.."

After completing the calculation, I've divide each reaction to two to get all 10 points of reaction.

See attachment for the load and reaction.

If I'm wrong, please correct me and if you have any better idea, please share it with me. All the forces, P in the diagram are pre-calculated and is cumulative as the c.o.g shall be between each reaction, R.

Thank you.

 

[mfadzil]

Correction;

Ra + (Rb1+Rb2) + (Rc1+Rc2) + (Rd1+Rd2) + Re = P1 + P2 + P3 + P4

 

[rb1957]

depending on how precise yo want to be, i think your answer would be close but you're assuming that each load is reacted by the closest two reaction points. more accurate would be to consider the generator as a beam (possibly infinitely stiff) on redundant supports. look into the method for redundnat beams called "unit load"; to solve you'll need an "I" for the beam, substitute a value, make it larger to see the effect.

 

[mfadzil]

Thanks for your reply.
I've search for "unit load", however i didn't get how it works.
It will be very kind of you if you could write some example for me for my reference.
Thanks again.

 

[rb1957]

bruhn , or similar "old" structures texts, describes it; my "old" university text describes it.

a quick yahoo "unit load method", found an article in wiki "unit dummy force method" ...

seek, and ye shall find ...