Turnable Rack Vibration

Hi Hdm!

Hdm -> "Kenny: When you say the Target Pro shelf "flexed under the load" are you saying that the rack itself flexed or the shelf material (MDF shelf)."

Yes, the shelf itself flexed and I was within the maximum weight load. It's possible that the shelf was defective but I did not get a response from Target. If you email me I can send you pictures.

Previously, I had used an older Target shelf with a SOTA table but I needed the Pro shelf to accomodate my new table. The old Target shelf never flexed but it was designed differently.

The flexing scared the "%@#!" out of me and I didn't care for the sound. I could not adjust the front leveling screws to bring the table up to level. The pictures are very revealing.

I earlier in this thread recommended the Target wall shelf, only bcause it works, and it's cheap (relatively). To level the top shelf, I placed a 3/16" thick! steel bar behind it, with a backing of sorbothane. It pissed me off, I thought the damned thing was made in England, maybe it is, but whoever built it did a piss-poor job if it.

Dan

Kenny: That's too bad. That would move me very quickly away from the wall mount as well! I have an older Target wall mount, the one which Nsgarch described with triangular bracing. It is solid as a rock. Too bad that Target has cheapened the product.

Previously, I had used an older Target shelf with a SOTA table but I needed the Pro shelf to accomodate my new table. The old Target shelf never flexed but it was designed differently.

Kenny, that's exactly what I was referring to 6 posts ago ;--) The original version IS BETTER

As for leveling the shelf surface itself, before installing the wall shelf against the wall, put a 3 foot or longer carpenter's level against the wall (vertically) and check to make sure the wall isn't leaning in or out!! It's a lot easier to shim the whole shelf (frame) at the wall than it is to try and level the (horizontal) shelf surface later on.

Dan, for what it's worth (and I've been using Target wall shelves since 1990 ;--) one of the best (and easiest) mods one can make to the MDF shelf that comes with the unit is to make a "constrained layer" damped shelf out of it. Start with a second sheet of denser material the same size as the MDF shelf. I use 1/4" glass, but you can use Corian, acrylic, granite, aluminum -- whatever, as long as it's a harder than the MDF. Then get a sheet of 1/8" - 3/16" thick (maximum) dense foam or sheet sorbothane. Spray the bottom surface of the MDF and one surface of the second material with 3M 88 Spray Adhesive and press the sandwich together, place it on a flat surface and set a couple of cinder blocks, side-by-side on top for 8 hours (you want the adhesive to dry out under pressure!) You now have one of the best constrained layer damping systems in the world! If you can use spikes under your TT, that will increase performance even further.

How it works, is that the vibes drained off the bottom of the TT (by the spikes or feet) travel more or less straight through the MDF (and are just partly absorbed by it) but the MDF itself can't vibrate because it's sitting on something hard and unyielding. When the vibrations exit the MDF and hit the constrained (i.e. mostly squished) layer, they are forced to travel horizontally through the foam or sorbathane until they dissapate. You can pay more but you can't get a better shelf. All by itself, the MDF shelf will bounce (too little for us to see or feel) but it won't absorb! It will transmit the vibes to the metal structure and possibly refelect some back to the TT. That is NOT what you want ;--)
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"Unfortunately, the tie-back solution is mostly effective against F/B movement. Much less L/R movement, and not at all for vertical movement."

When I've screwed fasteners from the bracket into the shelf and into the wall, and done so at either end of the shelf, f/b or l/r simply didn't occur. Might as well have been on the wall.

Also helps to mitigate vertical vibrations, but not entirely.

Total expense for this "fix" is under $10.