Just so you know it takes about 20-25lbs of sand to do a partial frame fill for a normal size S3. Speed tested to 1000ipm and 1500 accels on steel belts.
Hoping to dampen the higher frequency vibrations. I’ll be machining quite a bit the next few days. Let’s see how it works. Also if I’m not dumb i’ll pick up the right sized rubber plugs. No leakage from side plates.
Find any change in harmony?
I was gonna do this same thing in tandem with the linear rails. Though my plan was to fill from extrusion ends and use a 3D printed inner cap to help apply some pressure and compression to the sand when remounting the steel framing.
quick thought;
drill and tap the end plate for a fine threaded bolt.
(if not enough meat/suspect of plate you can have a flange mount add-on which provides some added depth for threads of larger ‘fill’ bolt)
fill through here then use the bolt length to compress sand as you continue to tighten.
trial and error so you don’t have a long bolt sticking out.
seal off the extrusion around the plate with some caulk/adhesive for added safety.
I only have an hour or so of machining so no real data yet but seat of the pants indicates better. A way to record and measure vibration realtime would be the ticket.
Not really sure if compressing the sand will have any positive effect. I was planning on doing an epoxy/sand mix if there weren’t any bad trade offs. Grease the bolts and end plates, bolt together machine and pour.
Any fill will increase mass, reducing the amplitude of any oscillations by the simple fact of Newton’s second law. A solid fill (e.g. epoxy/sand) will also increase rigidity, which may or may not be of value given the other components in play. On the other hand, a solid fill may not be the best choice for actual vibration dampening.
A “loose” sand fill not only increases mass, but the friction of the individual sand grains moving against each other dampens vibration (the energy of the vibration being turned into heat). Consider, for example, a heavy ball peen hammer versus a dead-blow hammer of similar mass. The loose fill in the dead-blow hammer does a much better job at dampening the vibrations.
If the additional mass and rigidity of a solid fill mean that you no longer have anything that is in tune to resonate with the vibrations from cutting, et cetera, that may be a desirable approach. (Solid fill is immune from leaking, I imagine.) On the other hand, a loose sand (or whatever) fill should actually damp out vibrations. Just my thoughts.
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