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back to Shotpuck Intro

Introducing ShotPuck Two.  (SP2) A 3-D printed, lead-shot-loaded record weight.

Price is $47.50 usd plus shipping and supplies; usps priority mail medium flat rate box: $15.50 -- conus, will ship to Canada

Paypal, Money order, cash (if local pickup)

Available finishes: Textured Black Enamel..

Note: It takes 3 days to completely finish one shotpuck.  When I have inventory I can ship right away.  Otherwise the purchase is treated as a custom order and some communication with the buyer via email or by phone is desired.

email: webmaster@theanalogdept.com

Caution: contains lead shot

Left: ShotPuck Two, (SP2) the 3D CAD model.

Left: The 3D printed SP2 . Finish: vapor black 

Left: SP2 in Vapor Black finish.

Left: Another SP2 in textured black enamel and at work.

DSC_3244.jpg (115037 bytes) Two finished SP2s.  One in black, the other left natural gray.

DSC_3245.jpg (224455 bytes) DSC_3246.jpg (215347 bytes) Left: Looking at the top and then the bottom.

What is the purpose of this record puck? (also known as a record weight)

Q: We might just as well ask the question; what is the point of any record weight?*

A: to dampen vibrations running through the record as it is being played.

Q: why lead shot chambers?

A: Very much like a sand box, the individual lead shot vibrate against one another when stimulated by an external source of vibration.  This implies that the individual shot act as a conduit through which vibrations travel.  However, because the individual shot are in intimate contact with a large mass of shot, there is not enough energy coming from the source stimulant to force the vibrations to pass completely through the chamber.  Ergo vibrations go in, they are dissipated and die within the shot chamber.  When this theory is executed properly within a record puck, the end effect is that the reduction in record vibrations result in a cleaner sounding playback.  This should also result in a measurable improvement in the s/n ratio.

*(Record weights are often nick-named a 'puck'. because the size and shape often resembles a hockey puck)

The ShotPuck Two (SP2) is a record weight that features 5 chambers loaded with #9 lead shot.  In fact 85% of ShotPuck Two's total mass is #9 lead shot.  Each chamber contains precisely 65.2 grams of the shot.  Total weight of the assembled record weight is 382.7grams (.84 lbs).  For other measurements including height and diameter please see the dimensioned drawing further down this page.

Left: each chamber is filled with precisely 65.2grams of #9 lead shot. Times 5 this makes a total of 326.0 grams of shot over the record.  

After assembly, the lead shot composes 85% of the total mass of SP2.  When it comes to ShotPucks, it really is all about the shot, because it is this mass of shot within each chamber that works to dampen the vibes running through the record as it is being played.  It also helps that the puck material, ABS, has an acoustic impedance slightly lesser than that of vinyl which allows easy penetration of the vibes coming from the Lp into the puck.  ShotPuck Two does not use foot pads.  In this design the ABS material is coupled closely with the Lp.

About the process: 

The Virtual: It starts as a 3D CAD model

A CAD model is drawn in 3D using the CAD software of the author's choice.  Then the 3D CAD model is exported to special 'slicing' software that prepares the G-code that operates the 3D printer. The export format is ".stl"  (stereolithography). The printer prints.  After printing, the printed part receives several post process operations and then.....

sp2_2f.jpg (86311 bytes) sp2_2g.jpg (91031 bytes) sp2_2h.jpg (84883 bytes) hint: click on thumbnail to view image full size

2dash2explode 5.jpg (96477 bytes) exploded assembly view

The Reality: From the CAD model to the printed part


DSC_3221.jpg (325496 bytes) DSC_3222.jpg (318236 bytes) The finished SP2 - bare.

The plan

The Goal:

  1. The record weight couples tightly to the record label so that it may dampen vibration energy that travels through the record while it is played.
  2. The record weight by means of its added weight presses the record into the platter mat upon which it rests while being played.  This assists the mat to dampen vibration energy traveling through the record as it is being played.
  3. The mass of lead shot, directly over the record label acts as a dampening medium. 


It should be noted that this "record weight" (puck) is not of a design that is meant to flatten warped, or slightly warped, records against the mat.  The shape of the mat itself plays a part in whether a record weight, or a record clamp** will have any success at flattening warped records.  There will be times when it does have the effect of flattening slightly warped records, but I do not mean to say that it is guaranteed to function this way with every record and on every platter mat.  The design intention for ShotPuck 2 (SP2) is to create an intimate coupling between the weight and the record so that it may dampen vibrations happening within the record.  

* needle talk; the acoustic version of the signal being electrically generated within the phono cartridge. 

** a record clamp: clamps the spindle either by a compression joint, or by means of screw threads and thus exerts a downward force against the record to press it against the platter mat. A record weight simply uses the weight of the clamp to impose a downward force against the record to press it against the mat.

While similar in design to SP1, SP2 contains 65.2 grams of shot in each chamber compared to SP1 which contains 36.7grams per chamber.  Due to the chamber shape at the label end, SP2 makes greater surface area contact on the Lp label area. SP2 takes advantage of the structural material in use for its low acoustic impedance qualities, which are slightly less than the acoustic impedance of the vinyl record itself.  Therefore vibrating energy traveling through the record as it is being played is encouraged by the lower impedance of the ABS material, to flow into the structure of the SP2 record weight....where this energy encounters a large mass of #9 lead shot.  The mass of lead shot serves two purposes.  One is to firmly plant the record weight into its position with maximum contact between the bottom surfaces of the record weight and the record label area. Like a shot bag, if anyone reading this has ever made the use of one.  Ever use a dead-blow mallet?  Notice how the dead-blow mallet never bounces when it strikes?  The mass of shot within that mallet absorbs the energy which would otherwise cause the mallet to bounce after its initial impact.  And so the lead shot loaded record weight maintains its solid grip against the record label as it soaks up vibrations traveling through the record.  The end result: cleaner and clearer sonic quality of record playback.  

The proof is in the listening.  The proof is in just handling and holding this record weight.  At slightly over 3/4 of a pound, you can feel its potential.  


Material Properties: ABS

Acrylonitrile butadiene styrene

Density: .9 g/cc to 1.53 g/cc  (grams per cubic centimeter)

For mechanical use, operating temperature range: -20 to 80C (-4 to 176 F.)

Impact Strength: 5.7 to 6.2 ft-lb/inch

Compressive Strength: 1100 to 7100 Peak Stress in PSI

Tensile Strength: 4936 to 5532 Peak Stress in PSI

Flexural Strength: 5344 to 8646 Peak Stress in PSI

acoustic impedance ( Z ) : 2.31 to 2.36

for reference: Z of PVC (vinyl)  is 2.99 to 3.27


Total weight Shot Puck Two: 13.5 ozs (382.7grams) (.84 lbs)

Lead shot weight: 326grams (.72 lbs) (11.5 oz)

85% of the total wt is #9 Lead Shot


Process detail photos:

SP2-1_print.jpg (317254 bytes) SP2 fresh off the printer

SP2-1_print_raft.jpg (373110 bytes) Bottom side shows the adhesion layer.  ( the layer that maintains intimate contact with the heated bed of the 3D printer) This particular adhesion layer type is known as a 'raft'. It serves to prevent the part itself from shrink warping as the lower areas cool while the upper areas remain hot from the ongoing printing.

SP2-1_print_trim 1.jpg (318615 bytes) After removal of the adhesion layer (raft) and deburr.

SP2-1_print_trim 2.jpg (329952 bytes) Bottom side after deburr, prior to machining for the bushing.

SP2-1_print_bush 1.jpg (245700 bytes) From the top.  After machining and bushing press-in.

SP2-1_print_bush 2.jpg (281164 bytes) From bottom.  After machining and bushing press-in.

DSC_3220.jpg (316092 bytes) Loading the shot as part of the assembly process.  Each chamber gets 65.2 grams of #9 lead shot.

Thanks for looking!