DIY Isolation Platform

Hi Jahaira and Psychicanimal,

Whenever a compliant mount is used under a component, the amount of compliance (how springy the mount is) must be optimized for load weight. A mount designed for a very heavy device like a large transformer or motor will be significantly less effective for a much lighter load weight such as a turntable or other audio component.

In physics it is called Mass Over Spring where the compliance of the spring must be optimized for the mass and weight placed on top of it. If the mass and weight of the load is significantly under or over the optimum range for the particular spring employed the ability to reject displacement (vibration) will be significantly reduced. The term Spring as it is used here does not mean just a coil of metal but refers to any compliant material that is placed under the mass.

Best Regards,

Barry Kohan

Hi to all.
On this subject I like to add a similar project I got on the go right now.I constructed my own Aluminum audio rack a little while ago.In fact I started a thread under "Misc Audio" describing the fabrication details.Currently I am working on a device that will isolate the entire rack components and everything on it from floor vibrations.Here is the details.First I have to say that I am an experienced commercial aluminum fabricator/installer (curtain wall type of windows in high-rise buildings),worked with glass and aluminum for years and I am a Union Glazier/Metal mechanic by trade.Making projects like this require skills ,tools,workshop and working with metal can be dangerous.Safety comes first as we all know.Basically I made four boxes(cases) out of 1/2" thick heavy gauge industrial grade aluminum .What they are really is two 4" by 6" by 1/2" "L" shaped aluminum angles that are fastened facing each other,so that they form a box of 4"x6"x 4" deep.I made a bottom piece and a top piece.The top piece is freely moving inside the box because it's cut a touch smaller (about 1/16" perimeter clearance)The bottom piece is tapped and secured on the underside with 8 screws.All connections are made with 1/4" x 20 Flat head medium thread stainless steel machine screws in order to keep the entire assembly non ferrous non magnetic.All four boxes are braced together with aluminum tubing of 1" by 2"@ 3/16" wall thickness size.The bracing looks like the letter "H" only with a double middle horizontal bars for additional strength and stability.All these four boxes connected together will be placed under my rack's four feet.Every foot corresponds with a box.The boxes will be filled with lead shot or double squash balls.The free moving undersized 1/2" aluminum cover will rest on top of the lead shot or double side by side squash balls,and the rack's feet will rest on top of these floating covers.As an extra safety precaution I will machine a "dimple" on the center of the floating cover that will accept the disk footing of the foot of the audio rack.Under the center of the disk footing I will fasten a 5/16"carriage bolt that comes with a smooth spherical head,that spherical head will protrude under the disk footing and will fit in the dimple that I will machine on the surface of the cover.It won't slide out of position!Will experiment with what works best for filling the boxes....As an option I will drill and tap the underside of the boxes with 1/2" hole to receive a brass 1/2" threaded cone.
Barry Kohan.You got an amazing line of products ,would you care to comment on my project and any critical estimates and recommendations are welcome.
Regards
George

Hi Yioryos,

Thank you for your question and your comment.

I don't consult on DIY projects but I will say that squash balls, racquet balls or tennis balls are not nearly compliant enough to achieve the low resonant frequency your project will require. They also contain a very small amount of air which significantly compromises their ability to decouple. Lead shot is massive and damped but is also not very compliant so it too is not going to achieve significant decoupling. I would suggest that you assess how much vibration is being transmitted into each component from the structure of the main rack itself due to BOTH floor-borne and air-borne vibration. It is probably more effective to have the vibration control device under each component individually. Decoupling the entire rack at only the bottom or the top still leaves the components subject to a number of forms and sources of vibration.

Properly controlling vibration requires that one address all three main sources of vibration: floor-borne, air-borne and internally-generated vibration.


Best Regards,

Barry Kohan

Hi Barry
Thanks for your input.
I agree with everything you said and was aware of all your points.Today I experimented with one of the boxes that I made .I had it filled with No. 6 lead shot and then put the cover on with a full of water glass resting on top.I pounded hard on the floor and observed for any waves on the surface of the water.There were waves with the glass sitting on the plain floor AND when resting on the isolation box.BUT I believe that the glass of water is extremely light weight for that particular box.At this point I need to do my homework and find a suitable material to fill the boxes with.Perhaps fine silica sand,but I got to take the weight of my rack WITH the components on it into account.My rack alone is very heavy once the components are placed on top it becomes ONE VERY HEAVY rack.
I do believe that my assembly WILL help to at least a degree in eliminating floor-borne vibrations.Also I plan to further isolate every component individually.
Regards
George