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Mold Your Own Anti-Vibration Pads

Posted by scott mathews   09/08/2004 12:00AM

Principal Engineer
Steward Observatory/University of Arizona
Tucson, AZ 85750

If you’ve ever wondered if those $50 a set, rubber anti-vibration pads really work, the answer is an unequivocal, “that depends.” From an engineering standpoint, the “anti-vibration” pad is not actually “eliminating” vibration, but is acting as either a damper by nulling out the natural vibration of a system shocked by the user, or as an isolator by preventing ground motions from transmitting into the system being supported. Without getting into a gutsy explanation of the dynamics of elastic systems, the effectiveness of anti-vibration pads depends highly upon the mass and stiffness of the system being supported. For the most part, rubber anti-vibration pads sold for telescope mounts do the trick for light to medium weight mounts and their attached payloads, but getting the best performance from a commercially available set of pads may be hit or miss. What follows is an astonishingly simple way to fabricate your own anti-vibration pads that you can customize to meet your vibration control needs.

Mold your own. To do this you will need little more than some silicone caulk, and one or more disposable plastic food containers, or something similar. The containers I used at one time held margarine, and taper to approximately 5” inside diameter at the bottom. Most importantly, the bottoms are domed slightly.

It then is a simple matter of filling the container with a suitable amount of liquid caulk, allowing it to cure, and voila, rubber anti-vibration pad! But there is so much more that can be done for a little extra effort. By casting various thicknesses of silicone rubber discs and stacking two or more together, better trade-offs between support stability and damping/isolation can be achieved.

To make a casting, a $3 to $5 tube of bathtub caulk for use in a caulking gun will provide all that is needed for most applications. For the mold, keep in mind that some plastics will be better adherends (stick better) to the silicone, so it is a good idea to coat them with a “mold release agent” first (note: do not use WD-40 or other silicone based lubricants, since they may integrate with the rubber, allowing it to bond to the mold). A very thin layer of cooking oil applied to the inside of the mold with your fingertip works well. Squirt or pour in the liquid silicone, and let it cure a few days. The molded disc of rubber should pop right out.

Try making a few different thicknesses, .5”, .75”, and 1” are good round numbers. Measure and mark fill lines on the molds so that the thicknesses are consistent, disc to disc. Once you have a set of discs molded, try stacking them in various combinations, making sure that there is a gap between each where the concave depression (formed by the domed bottom of the mold) of the upper disc rests upon the flat top of the disc below. What you are aiming for is a combination that is sturdy yet allows for a small gap to exist between discs while supporting the load of the mount and telescope. When you find a combination that works well, bond the layers together using a small amount of silicone.

As a really nifty feature, you can mold red LEDs into clear silicone discs, and wire them up as warning lights marking the footprint of your setup at night. Without a doubt, this will get you some attention at your next star party. Have fun, and while you’re at it re-caulk the tub too; it’s probably way past due.

Clear Skies
Scott Mathews