Tonearm pod design?

[S Clark]

I need to build a couple of tonearm pods.  I've picked up 12-15 pounds of wheel weights from my local tire dealer, and will use green bean cans to mold a couple of bases.  The top 2 inches will be made out of mesquite from the front pasture.  The question is: should I bolt the mesquite directly to the lead, or put a layer of cork/silicone/rubber in the middle?  Or are bolts a bad idea, and simply use caulking to connect them?
Or should I be looking in a different direction altogether?

[Nick B]

My conjecture would be to use a layer in between, bolt them together and use a layer of the same damping material at the top and bottom of the bolt. Any vibration specialists here??

[S Clark]

Well Nick, your suggestion is pretty much what I was thinking. The lead supplies deadening and mass, the wood offers a layer that can be milled easily, and a layer of something in between.   I'm hoping that Dave E or some of the other more technical guys will add their 2 cents. 

[BobM]

I'm no expert but I would say that the tonearm would need to be as rigidly attached to the mass as possible. Any amount of sway in it could cause micro vibrations that you don't want. Though the mesquite will look pretty, I still question whether you even want that? Maybe just make a ring of it on the outside and bolt the tonearm to the heavy metal in the middle.

[S Clark]

I want a wood top surface since it's easy to get it milled and perfectly flat, and mesquite is dense, and available.  I guess they could mill the lead just as well- might look into that.  Attachment is not a problem with wood, perhaps could be a problem with lead.

[rollo]

   Mass from the lead base is a VG idea. So we have a dead solid lead base and need to attach a wood plinth for securing arm. To take advantage of base I would suggest gluing the wood to lead or add a piece of cork or rubber in between.


charles

[S Clark]

Charles, there has been lots of arguments on line about the merits of an independent pod vs. attaching an arm to a plinth.  I was planning on a naked Victor TT81 table without plinth for this pod.  Is there a particular reason you advise attaching the pod to a plinth?  I sorta like the ability to move a pod from table to table.  Any suggestions for adjustable feet?  It's now resting on 3" of maple cutting board, with the TT on three wine corks, and a temporary mesquite pod on trimmed to height and upright cork.  Had to drink a lot of wine, but we all make sacrifices for our hobby. 

[P.I.]

Heresy at foot. Read on >>>>>>>

Silicon is a high hysteresis material that stores energy.  Case in point; a million years ago when the world was young I used to fly control line racing model airplanes.  One of the events was called Fast Rat Race.  Tim Gilott from CA designed an airplane ( the Shark Rat:https://www.airagestore.com/planes/plans/control-line/gillot-shark.html) that was way out of the box for that period.  These were model airplanes that were capable of 140+mph flown on 2 - 60' music wires and 3 pilots to a circle.  Scary event, but way fun!  I didn't fly them.  I built them and was the pit guy.  My pilot told me that those speed were f*****g evil, so we went to FAI Tem Race.  Yet another story for people that flew control line model airplanes.

Tim's designs were bleeding edge and so the local contingent built 4 of them.  2 guys went with Tim's advice of using Mortite caulk to bed the fuel tank into the Harter speed magnesium pan the motor was mounted in.  These airplanes were scary fast.  A couple of builders decided Tim was stupid and used silicone to bed the tanks into the speed pans.  They would accelerate from the pit stop, make a half a lap, foam the fuel and the motors would quit.  These guys bitched about how bad the design was to no end.  When we finally convinced them to use Mortite, the engine runs became consistent from launch to the pit stops.  Tim, being the ultimate competitor listed silicon. He admitted to us later that he didn't use silicon, but Mortite, too.  Yes, he was a 'rat', but a great guy.  He just wanted to win!

It was then that I determined that silicon was vibration's friend.

I do not use silicone for anything except for sealing glass.

YMMV...

[rollo]

Charles, there has been lots of arguments on line about the merits of an independent pod vs. attaching an arm to a plinth.  I was planning on a naked Victor TT81 table without plinth for this pod.  Is there a particular reason you advise attaching the pod to a plinth?  I sorta like the ability to move a pod from table to table.  Any suggestions for adjustable feet?  It's now resting on 3" of maple cutting board, with the TT on three wine corks, and a temporary mesquite pod on trimmed to height and upright cork.  Had to drink a lot of wine, but we all make sacrifices for our hobby.

  The plinth I meant is a piece of wood atop the lead. I would isolate lead mass with brass cones [ Mapleshade ,small ]. Wine is good.


charles

[BobM]

Even very small micro vibrations, or micro movements, are bad for a tonearm mount. Having a separate pod sounds like a good idea initially since you can adjust easier, but it better be damned heavy so it will not move, not an iota. That's why so many designers attach the tonearm directly to the plinth, it eliminates any idea of separate movement between the tonearm and the record surface.

Same idea against putting any kind of squishy material between the tonearm itself and its mount. Keep the squishy stuff for below the turntable, between it and the stand it sits on.

Now putting something vibration absorbing under the motor pod, if it sits in a separate pod, is probably a better idea. That might take some of the vibration it produces and isolate it from the table top everything sits on.

[toobluvr]

Not attached to the plinth, but attached to the same butcher block that my heavy table sits on means nothing moves inadvertently and spindle-to-pivot distance is locked in.  (Two different versions shown below)

Construction includes none of the usual tweaky or snake oil thingies that audiophiles incessantly hand-wring over.   My goal was rock solid and rigid with locked in mount distance, and simple arm platforms I could easily fabricate myself for different arm mount schemes.  I discern no sonic difference -- DIY pod vs. stock mount -- when the same arm is mounted in both places.  Matter of fact, the Fremer test of placing stylus in groove and tapping shelf and arm platforms produces less thump thru speakers with the DIY pod than with the table's stock arm platform. 

Table is Eurolab / Scheu Premier Mk2.

[S Clark]

Thanks for the photos, Toobluvr.  I've looked at how you've set up your rig before as it looks like it should be a very nice sounding solution.  I was talking to Dave yesterday about pods and vibration.  But it all may be put on hold as the Victor TT-81 table just crapped out... no power.  I've got to do a bit of trouble shooting, or send it off, or both. 

[Nick B]

Not attached to the plinth, but attached to the same butcher block that my heavy table sits on means nothing moves inadvertently and spindle-to-pivot distance is locked in.  (Two different versions shown below)

Construction includes none of the usual tweaky or snake oil thingies that audiophiles incessantly hand-wring over.   My goal was rock solid and rigid with locked in mount distance, and simple arm platforms I could easily fabricate myself for different arm mount schemes.  I discern no sonic difference -- DIY pod vs. stock mount -- when the same arm is mounted in both places.  Matter of fact, the Fremer test of placing stylus in groove and tapping shelf and arm platforms produces less thump thru speakers with the DIY pod than with the table's stock arm platform. 

Table is Eurolab / Scheu Premier Mk2.

Great idea...great workmanship 👍

[toobluvr]

Great idea...great workmanship 👍

You are too kind, thanks.

Just something I initially cobbled together real quick with scrap pieces to make sure it works and doesn't hurt the sonics.  Never got around to prettifying -- easily done w/ some sanding, stain, paint, etc.

I'd really like to lose the clamps -- they are the main ugly factor.  Problem is it's not heavy enough on its own, so would need bolting or glueing to the BB.   But I don't wanna lose flexibility and the ability to move it around as desired.

My brother is an engineer with a high tech machine shop (CNC lathe), maybe I'll have him make me one of these:

https://www.acoustand.co.uk/collections/turntable-parts/products/tonearm-pods-for-all-applications-premium-product

[Nick B]

Great idea...great workmanship 👍

You are too kind, thanks.

Just something I initially cobbled together real quick with scrap pieces to make sure it works and doesn't hurt the sonics.  Never got around to prettifying -- easily done w/ a il sanding, stain, paint, etc.

I'd really like to lose the clamps -- they are the main ugly factor.  Problem is it's not heavy enough on its own, so would need bolting or glueing to the BB.   But I don't wanna lose flexibility and the ability to move it around as desired.

My brother is an engineer with a high tech machine shop (CNC lathe), maybe I'll have him make me one of these:

https://www.acoustand.co.uk/collections/turntable-parts/products/tonearm-pods-for-all-applications-premium-product

Nice website. Yes, I'd persuade him to make one of those