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VPI TNT Bladder replacement

Hoping for a little guidance on this because the bladders in my VPI TNT 3 legs are toast.  I've read that good substitutes are a squash ball, racquetball or paddle ball, the Gingko ball, or perhaps the Herbie's ball as well.  But, it's not at all clear how this replacement is actually installed - so hopefully someone out there can share their solution.  

Here's the background to my question:
  • yes, the bladders are easily removed
  • leg cavity holding the bladders is approx 2" diameter measured parallel to the plinth - and this diameter is reduced 1/4" or so by the two bolt heads (which intrude into the leg cavity) that connect the leg to the plinth 
  • leg cavity height (vertical) is about 2-1/4"
  • Squash ball diameter is 1.6" and seems too small
  • Herbie's ball diameter is 1-7/8" and might be a tad small and too hard to squeeze past the bolt heads
  • Racquetball diameter is 2-1/4" and might be too large to squeeze past the bolt heads.  And if it does squeeze past the bolts, it might not stick out far enough below the leg cavity to provide support
Sure, all this is easy enough to test out, but I'm hoping someone out there has solved this problem - Thanks for the help!
poonbean
dlcockrum's avatar
dlcockrum
2,190 posts
 
They are a pain, poon. Harry once stated that they ultimately work better than VPI’s handball upgrade, but at a high cost of convenience IME. I am considering a Symposium Ultra shelf with solid coupling to bypass the feet all together...

Good suggestion to invoke the VPI forum, maybe also the ET-2 Tonearm Owners forum. Several experienced TNT owners on there...

I am looking forward to reading what you come up with.

Best to you poonbean,
Dave
wntrmute2's avatar
wntrmute2
188 posts
 
I converted mine to the ball suspension.  I placed a cork/plastic disc cork side against the ball into the cavity first so an allen head set-screw could be run down to adjust height.  Then I used squash balls which while too small works fine once modded.  The mod was I wrapped a piece of thin weatherstripping with adhesive side all the way around except where the bolt heads were.  Sort of a "C" shape.  Works fine.  Floats as nicely as before with a better grounded sound.  
poonbean OP
42 posts
 
Thanks - you just confirmed my suspicion that it's clearly not a plug and play repair ball install.  The tops of the VPI legs on my TNT are not threaded, so I don't see how your clever allen screw would work...?

Looking more at ball diameters, turns out tennis balls are 2.75" diameter, which means the leg cavity (with ID of 2") could sit right on top of the tennis ball and not roll around - height could be adjusted with shims under the ball.  Seems too easy, so I'll give that a shot this weekend.  

I'll also ask the VPI forum and will report back...
dlcockrum's avatar
dlcockrum
2,190 posts
 
I think the "stock" apparatus was removed when the air bladders were installed by VPI, thus no threads. Same boat here.

I recall speaking directly to Harry many years ago about my air bladders and he remarked that they needed to be adjusted to <3psi in order to take the resonance frequency below the audible range. You may want to try drilling holes in the tennis balls to try to do the same.

Look forward to reading what you discover, poonbean.

Dave
wntrmute2's avatar
wntrmute2
188 posts
 
I guess I forgot the use of a simple tap to cut new threads.  Seems the tennis balls are way to big to fit into the cavity.  You want the towers to sit ON the tennis balls?
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