I was thinking about building a head shell which would act as an energy sink. The jist of the idea is to have an open rectangular metal frame with a horizontal cross member about 3/16-1/4 inch wide (front) and the other 1/8 inch wide at the back, the side pieces would be about 1/8 of an inch wide. So the centre section is hollow (for the moment). The two cartridge fixing holes would be in the front section. The mounting points would have a washer hard fixed to this frame one at each hole and a third in the centre on the rear cross section so the cartridge makes contact at three points when screwed down. Now comes the interesting part. The open central section would be fitted with five flat prongs about 1/16 of an inch wide and spaced apart, three attached to the front cross piece and two attached to the rear cross piece. These three prongs hard mount to the front cross piece and extend back toward the rear cross piece but stop short and do not touch the rear cross piece. The other two similar prongs attach to the back cross piece and extend toward the front cross piece but again do not make contact at the front. So we have five rectangular prongs three from the front and two from the back all parallel to each other. Then the space between the prongs is filled with a damping compound.
The idea is that energy from the cartridge makes the prongs vibrate and the damping compound eats the vibration up. There may even be a little out of phase cancellation between the front mounted prongs and the rear mounted prongs but I can't be sure about that.
Any comments or suggestions would be most welcome. I hope that I have described this well enough for readers to understand so please ask questions if you are not clear on the design. I look forward to any and all comments. Regards Moray James.
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The idea is that energy from the cartridge makes the prongs vibrate and the damping compound eats the vibration up. There may even be a little out of phase cancellation between the front mounted prongs and the rear mounted prongs but I can't be sure about that.
Any comments or suggestions would be most welcome. I hope that I have described this well enough for readers to understand so please ask questions if you are not clear on the design. I look forward to any and all comments. Regards Moray James.
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Bit of a dilemma.
The only energy coming from the cart is what sneaks through the suspension into the body and then on into the headshell.
The only point of the headshell is to hold the cart in a geometrically stable position with reference to the tonearm pivot and stop any energy from the tonearm getting to the cart.
So there's a compromise between stability and absorption, made more difficult because any energy will find the path of least resistance.
I'd be interested to see what you can do with it. Some careful accelerometer measurement is in order.
I'd go for maximizing the surface contact area between the damping compound and the stiff support structure for the cart, that should maximize the chance of it working.
Here's a sketch. Good luck with it.
http://media.bestkiteboarding.com/mm/damper.jpg
The only energy coming from the cart is what sneaks through the suspension into the body and then on into the headshell.
The only point of the headshell is to hold the cart in a geometrically stable position with reference to the tonearm pivot and stop any energy from the tonearm getting to the cart.
So there's a compromise between stability and absorption, made more difficult because any energy will find the path of least resistance.
I'd be interested to see what you can do with it. Some careful accelerometer measurement is in order.
I'd go for maximizing the surface contact area between the damping compound and the stiff support structure for the cart, that should maximize the chance of it working.
Here's a sketch. Good luck with it.
http://media.bestkiteboarding.com/mm/damper.jpg
Moray, What an innovative design approach. I love it. Naturally there will be some fabrication problems to work out but not insurmountable. Going to give it some thought and perhaps a test piece a bit later. Busy right now. I've long felt that the right approach is to keep the energy off the arm wand by absorbing it as close to the source as possible. I do not recall any threads dealing with having an absorbing element (felt pad, silicone damping bar, whatever) between the cartridge body and the headshell. That would achieve some of what your proposed mount is intended to do. in a far less elegant way, but could indicate whether there is any chance of significant improvement in arm performance.
BillG
Hi,
Least resistance is what it is all about. Well put. 😎
Question is, how is this best achieved?
Cheers, 😉
Least resistance is what it is all about. Well put. 😎
Question is, how is this best achieved?
Cheers, 😉
I wonder if The Music Man isolator is similar in concept. I am skeptical of such product but some say it works for their systems.
.
testing concept
My Schroeder clone has had a couple resonances that I've not dealt with much at all and have been plaguing me for a long time. So last night I replaced the mounting crossbar on my Schroeder clone with a 1" square of cork about 3/16" thick. Held it to the arm with the single mounting screw driven into but not all the way through the cork piece. fastened the cartridge to the cork with double sided sticky tape and put the kluge on to play. With the record not turning but the stylus resting on the record virtually all trace of resonances were inaudible even at very high volume settings. Previously, no matter what I did for anti skate settings and alignment of the arm and cartridge there were some tracking error distortions audible in the playback. With very little care in setup of the corkmod several records played from beginning to end with nothing evident. Stayed very consistent for the whole disk. There was some change in the overall character of the sound. Best described as a midrange dulling. Lows and highs were excellent.
So what is this all saying? I think that some form of headshell isolator can make a huge difference in a tone arm. Moray's fingers and absorbers may be the way to go. If I'm looking at it correctly Moray, your rectangular frame is solid all the way around. The fingers are integral with the front and rear cross members of the frame and together with the damping goop suck up the vibrations. This solid frame may kill the midrange dulling I hear with the cork pad. The absorber is key to the idea really working. And finding the right absorber will be the trick. The Ortofon cartridge has a removable weight to provide two selections of cartridge mass. So an Ortofon (OM series) can be adjusted to compensate for the added mass of the Moray Isolator. I wonder if we can come up with the automotive material the MusicMan Isolator uses. Think you guys! Then too, I wonder if it would be better to provide a break in the side rails of the Moray isolator and let the absorber hold the two parts together.
BillG
Checked out the musicman isolator link. That is what I've had in mind for a while but done nothing about it for lots of good reasons, mostly lack of a good isolation material. But I think I've seen felt or other semi absorbing pads applied between cartridges and arms before.
My Schroeder clone has had a couple resonances that I've not dealt with much at all and have been plaguing me for a long time. So last night I replaced the mounting crossbar on my Schroeder clone with a 1" square of cork about 3/16" thick. Held it to the arm with the single mounting screw driven into but not all the way through the cork piece. fastened the cartridge to the cork with double sided sticky tape and put the kluge on to play. With the record not turning but the stylus resting on the record virtually all trace of resonances were inaudible even at very high volume settings. Previously, no matter what I did for anti skate settings and alignment of the arm and cartridge there were some tracking error distortions audible in the playback. With very little care in setup of the corkmod several records played from beginning to end with nothing evident. Stayed very consistent for the whole disk. There was some change in the overall character of the sound. Best described as a midrange dulling. Lows and highs were excellent.
So what is this all saying? I think that some form of headshell isolator can make a huge difference in a tone arm. Moray's fingers and absorbers may be the way to go. If I'm looking at it correctly Moray, your rectangular frame is solid all the way around. The fingers are integral with the front and rear cross members of the frame and together with the damping goop suck up the vibrations. This solid frame may kill the midrange dulling I hear with the cork pad. The absorber is key to the idea really working. And finding the right absorber will be the trick. The Ortofon cartridge has a removable weight to provide two selections of cartridge mass. So an Ortofon (OM series) can be adjusted to compensate for the added mass of the Moray Isolator. I wonder if we can come up with the automotive material the MusicMan Isolator uses. Think you guys! Then too, I wonder if it would be better to provide a break in the side rails of the Moray isolator and let the absorber hold the two parts together.
BillG
Just for the sake of sharing I have had excellent results with using PVC electrical tape as an interface in all sorts of situations. The thickness is what works for you. Top quality PVC tape is usually 5 mill (that's 5 thousandths of an inch) thick and the cheaper versions are normally about 3 mill thick. The 3 mill thick tape is the one to use. It is thin and soft enough to cold flow out and sticks down under pressure like a suction cup. Due to the thinness it does not add much compliance and adds just enough damping over a very wide band to make it a useful tool to have.
Bill: the prongs or tines should be rectangular in shape so that they will only be able to vibrate up and down not sideways. This is important as any side to side motion will impact the cartridge tracking where up and down is pretty much a non issue. For a damping compound I was thinking that a good starting place would be Duct Seal used in outdoor electrical and HVAC work. Both softer and thicker materials could be tried. You will not be using much so I don't expect added mass to be a problem. I would not break both side rails as you need the strength and a solid coupling to the tonearm. I do think that the head shell could be made in a "C" shaped three sided rectangle then more tines could be incorporated.
Bill: the prongs or tines should be rectangular in shape so that they will only be able to vibrate up and down not sideways. This is important as any side to side motion will impact the cartridge tracking where up and down is pretty much a non issue. For a damping compound I was thinking that a good starting place would be Duct Seal used in outdoor electrical and HVAC work. Both softer and thicker materials could be tried. You will not be using much so I don't expect added mass to be a problem. I would not break both side rails as you need the strength and a solid coupling to the tonearm. I do think that the head shell could be made in a "C" shaped three sided rectangle then more tines could be incorporated.
Hi Moray,
Did some crude sketches tonight to just about scale to get a better idea of what we are trying to do. Used your 1/16 - 1/8 - 1/4 dimensions for starters and an overall frame size of about 1" square. This fits 5 tines into it nicely. The one thing that I questioned was how thick to make the tines and the frame member(s). To keep a rectangular cross section of the tines, to restrict them to up and down motion, looks like they should be on the order of .015" to .020". The frame itself could be anything from 1/16" to 1/8" thick. Basically we are looking at a sheet metal structure. Am I interpreting this as you intended it to be?
(Leave the damping compound out, and mount it on an air bearing arm and the escaping air will play the thing like a harmonica.)
Whilst playing around with the concept, pencil in hand, the thought occurred to me that thin tines might not provide as much energy sink as we are needing. If the energy flows along the paths of least resistance, we may achieve greater transfer/damping if instead of tines we use a thicker one piece frame perforated by many holes of various sizes and filled with the damping material.
Hey Bill: that sounds right. If a three sided frame structure were used there is no reason why longer tines could not be used to get additional resonant action going and so increase the amount of energy sinking. Further there is no reason why the arm could not be "T" shaped with the solid "T" section having the cartridge mounting holes. Then you could have tines protruding horizontally along each side of the main shaft for even more resonant action. The tines could be adjusted for length to cover a wide bandwidth. If the tines were long at the tip end of the assembly you could also get some added stability along the lines of the Frank Van Alstine's out rigger weights. Two birds with one stone.
leave no Tern unstoned
Hi Moray, Seems to me we are getting far afield from the goals of your original post. Longer tines, more resonant action etc. when what we were trying to do was kill the coupled energy from the cartridge body from getting onto the arm wand. My first take on the tines was what a neat way to get more of this unwanted energy absorbed. Put more of it in contact with the damping medium. By the time we have the tines packed with absorber, there is no way they will resonate.
So I tried a simple test with a cork mounting piece and observed some good results, and some not so good. To further this approach, still not getting into the complexities of fabrication for the "tines approach", I made a damped version of the "T" bar cartridge mount piece used on my magnetically suspended tone arm. Made a new T bar from the same wood as the arm wand (mahogany). Same dimensions as the aluminum piece. Then I drilled a center hole for the screw which holds it to the arm wand. then added 4 more holes, 2 on either side of the center hole. These 4 were about as large in diameter as could be gotten into T bar. Filled these holes with modeling clay (plasticine) , attached the cartridge with double sided sticky tape, mounted it on the arm and listened. Here was a major improvement. Clear, clean, unmuddied midrange, super sound stage etc. At full volume setting, there was but the slightest trace of arm wand resonance. So again I am convinced that stopping the energy as close to the source is the way to go. Keep it out of the rest of the arm and TT assembly. The damping material will absorb the energy and dissipate it as heat (not much) rather than trying to lead it off unattenuated and un-reflected (impedance matching the transmission line) to be absorbed later on down the chain. Need to do a bit more work on a slightly bigger piece and a better way of attaching the cartridge than a bit of sticky tape a quarter of an inch wide. Got some ideas for a better shape and size. Just got to do it.
Hi Moray, Seems to me we are getting far afield from the goals of your original post. Longer tines, more resonant action etc. when what we were trying to do was kill the coupled energy from the cartridge body from getting onto the arm wand. My first take on the tines was what a neat way to get more of this unwanted energy absorbed. Put more of it in contact with the damping medium. By the time we have the tines packed with absorber, there is no way they will resonate.
So I tried a simple test with a cork mounting piece and observed some good results, and some not so good. To further this approach, still not getting into the complexities of fabrication for the "tines approach", I made a damped version of the "T" bar cartridge mount piece used on my magnetically suspended tone arm. Made a new T bar from the same wood as the arm wand (mahogany). Same dimensions as the aluminum piece. Then I drilled a center hole for the screw which holds it to the arm wand. then added 4 more holes, 2 on either side of the center hole. These 4 were about as large in diameter as could be gotten into T bar. Filled these holes with modeling clay (plasticine) , attached the cartridge with double sided sticky tape, mounted it on the arm and listened. Here was a major improvement. Clear, clean, unmuddied midrange, super sound stage etc. At full volume setting, there was but the slightest trace of arm wand resonance. So again I am convinced that stopping the energy as close to the source is the way to go. Keep it out of the rest of the arm and TT assembly. The damping material will absorb the energy and dissipate it as heat (not much) rather than trying to lead it off unattenuated and un-reflected (impedance matching the transmission line) to be absorbed later on down the chain. Need to do a bit more work on a slightly bigger piece and a better way of attaching the cartridge than a bit of sticky tape a quarter of an inch wide. Got some ideas for a better shape and size. Just got to do it.
Bill it is the resonant action of the tines combined with a damping compound which dissipates energy. The longer tines will resonate at lower frequencies than the shorter ones so a variety of lengths will result in a broad spectrum of energy absorption. The tines have to resonate in order to generate friction in the damping compound or the system does not work so a soft compound is required. I think that your idea of damping the structure is a good one and adds to energy absorption in the assembly.
Hi Moray, Think of how sound waves travel in steel railroad tracks, molecule after molecule bumping each other along till they finally get to your ear pressed tightly against the rail several miles away from the engine rolling ever closer to you. IMHO that is the mechanism at work here. No wave motion, no resonating beams. and while the undamped tine may well resonate at some frequency in the audio band, what happens to the Q of the circuit when the damping material is in contact with the tine? Another way to think of it is: a tine with a layer of goop followed by another tine on the other side of the goop N times on. Looks to me like constrained layer damping. Perhaps someone with better feel for the mathematical analysis could look at this and reconcile the two views, my head is too old for that now.
Best regards and thanks for initiating a rather fascinating discussion which has already improved the performance of my pivoted tone arm.
BillG
Thanks Bill: let me cogitate on your comments for a bit they make sense and this is exactly what I was looking for, some thought provoking discussion. So don't take what I say as having any kind of authority and if I disagree it may only be to see if you can convince me with a better argument and twist my brain to a different point of view. Different ideas help to provide perspective. Lets keep kicking the can till the stuffing all falls out and see what we are left with.
Moray, my friend (a little long and a rant...)
I've pondered your idea for some time since you emailed me this, and we had a talk on the phone or Skype ...
Unless a reduction in density occurs, it hardly matters what design of a head shell is implemented.[/INDENT]
I've pondered your idea for some time since you emailed me this, and we had a talk on the phone or Skype ...
Now that I can visualize your idea, I think I can tear it to shreds. After all, that's what I'm good at. And you know that my intent is to never hurt any egos, but rather present solutions. I think that's why we can discuss things without either getting offended. So for any that may think I have an axe to grind with Moray (or anybody really), nothing can be farther from the truth.
The Cartridge Man isolator or similar seems like a good idea. Your "tines" approach presents a few problems, the most obvious one being the caveat regarding engineering a solution to a problem rather than designing around a problem in the simplest form possible.
So what is the goal here? To isolate the cartridge from the tone arm as I see it. Which is basically the same kind of thing a turntable suspension is supposed to do (isolate the platter from its environment). Arguments can be made that the suspension is suppose to help extraneous energy from the playback system to dissipate, and to some extent it may, but the primary reason is to isolate the turntable from the environment.
Okay, back to cartridge isolator concept vs. energy dissipation concept. Any compliant material can provide a dampening action to vibration (and hence energy). One issue though can be the concept of material impedance and mismatching. It can be easily demonstrated that sound (and all vibrations) travel through denser materials much faster than air. If we can agree on that point the rest of the argument is relatively easy.
If we can force the vibrational energy to travel only one path, and that path is made up of a material that has a density well below that of metal or plastic (as most cartridge bodies are metal and/or plastic, mounting screws are usually metal, as are head shells) then the vibrational energy should be greatly reduced as it is dissipated or attenuated as it travels through this unknown medium. The unknown medium must be lighter (as in less dense) than the cartridge body, and any plastic or metal used between the cartridge body and the headshell. 3 point "isolation" as used on some Grado cartridges is certainly a pretty reasonable solution. But their is one solution (okay maybe two😉 ), that kinda jumps out at me. Air! As in nothing between the cartridge body and the head shell, but at some "thickness". Of course this unobtainable. Is their anything else that is mostly air, but that is rigid and has some physical dimension? One that stands out is Oasis Florists Foam. It can be very messy, but literally is as light as a feather. Traditionally made of urea formaldehyde, newer versions contain none. And of course the density of the headshell needs to be considered as well: less than plastic or the typical metal used (aluminium being the most common). So wood. A wooden headshell, less dense than plastic or metals (except perhaps Titanium), with three small wooden contact areas, and a small spacer made of "Oasis".That's where my vote lies
Unless a reduction in density occurs, it hardly matters what design of a head shell is implemented.[/INDENT]
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quote: So what is the goal here? To isolate the cartridge from the tone arm as I see it.
No that is not the intention. The idea is to take as much of the energy which the cartridge transfers into the head shell and dissipate it at the head shell so it does not contribute to resonances (unwanted ones) in the rest of the arm (especially the bearings). In my suggestion the intended resonance of the tines (vertical plane) is converted into heat in the damping compound. So it is a mechanical shunt which turns cartridge vibration into heat as close to the source as possible. There is not any magic action going on here. The tines would still dissipate mechanical energy into heat at their bending point even if there were no camping compound but the compound is an easy addition to obtain additional energy transfer. The cartridge needs to be firmly connected to the arm so that the arm can do its job and hold the cartridge in the correct orientation to the record. The forces involved will wiggle the cartridge if given a chance.
I have in the past mentioned foams of different sorts such as organic foam made of wheat or wood powder or glass foams. Any absorption of energy in a less dense structure such as wood will dissipate energy through adiabatic dissipation in the wood cells flexing the cell walls and so generating heat. My suggestion was to build a transfer system which was very efficient in exchanging mechanical energy into heat. So I don't see density of the structural parts as the important factor here. The tonearm still needs to be rigid to dissipate what ever energy is left over into the bearings and from there to the glass tube and from there to the plinth. The goal is make this path a continuous path and to prevent overload at any one point, overload resulting in feedback to the source.
Give a rip Stew and lets see if we can work this out.
Bill the side by side tines do not make up a normal constrained damping mechanism. The tines all move in the same direction (up and down) not toward one another.
No that is not the intention. The idea is to take as much of the energy which the cartridge transfers into the head shell and dissipate it at the head shell so it does not contribute to resonances (unwanted ones) in the rest of the arm (especially the bearings). In my suggestion the intended resonance of the tines (vertical plane) is converted into heat in the damping compound. So it is a mechanical shunt which turns cartridge vibration into heat as close to the source as possible. There is not any magic action going on here. The tines would still dissipate mechanical energy into heat at their bending point even if there were no camping compound but the compound is an easy addition to obtain additional energy transfer. The cartridge needs to be firmly connected to the arm so that the arm can do its job and hold the cartridge in the correct orientation to the record. The forces involved will wiggle the cartridge if given a chance.
I have in the past mentioned foams of different sorts such as organic foam made of wheat or wood powder or glass foams. Any absorption of energy in a less dense structure such as wood will dissipate energy through adiabatic dissipation in the wood cells flexing the cell walls and so generating heat. My suggestion was to build a transfer system which was very efficient in exchanging mechanical energy into heat. So I don't see density of the structural parts as the important factor here. The tonearm still needs to be rigid to dissipate what ever energy is left over into the bearings and from there to the glass tube and from there to the plinth. The goal is make this path a continuous path and to prevent overload at any one point, overload resulting in feedback to the source.
Give a rip Stew and lets see if we can work this out.
Bill the side by side tines do not make up a normal constrained damping mechanism. The tines all move in the same direction (up and down) not toward one another.
mechanical shunt...
my friend,
both the Oasis and your idea should work. The Oasis will try to shift, and disipate vibrational energy as heat, just as some sort of tine/dampening material/fluid system will. Simpler in terms of designing a solution is often the best (but not always😉 )
my friend,
both the Oasis and your idea should work. The Oasis will try to shift, and disipate vibrational energy as heat, just as some sort of tine/dampening material/fluid system will. Simpler in terms of designing a solution is often the best (but not always😉 )
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Stew: my best guess is that while I agree there is internal loss in open cell foam such as the Oasis I don't think that it will provide as much loss as the idea suggested. I think an arm structure based on a foam would be a good way to go so there is no disagreement there. Who is right? I guess that we have to build something and find out.
Do you really think it is the resonance that the cart generates that is the issue? Or vibration transmitted from the rest of the deck into the cart.
What you ideally require is that no extraneous vibration is superimposed onto the stylus/record transcription process. If you isolate the cart, it is isolated from putting resonance into the arm and receiving resonance from the arm.
Try this, measure your bearing rumble via the cart, now measure the vibration in your armbase with the stylus not on the record. Which is larger? Is it the same for all decks?
What you ideally require is that no extraneous vibration is superimposed onto the stylus/record transcription process. If you isolate the cart, it is isolated from putting resonance into the arm and receiving resonance from the arm.
Try this, measure your bearing rumble via the cart, now measure the vibration in your armbase with the stylus not on the record. Which is larger? Is it the same for all decks?
sq225917: thanks for the input. Vibration at the cartridge from what ever source needs to be dealt with. The cartridge has to be firmly held in place/position so what options do you see for doing so and isolating at the same time? Seems to me that a rigid structure that is well damped and which has high internal loss is a reasonable approach. With foam or other compliant cartridge mounting methods how do you insure the cartridge is held in position and does not shift during play?
I don't have the ability to measure rumble but I can listen with a stethoscope. I would ask you to answer for me your last two questions since it would appear that you have measured the results. Main bearing noise will be substantial in a deck. Depending upon style and build I am sure that main bearing noise varies greatly. I would think that solid plinth decks are good at transmitting main bearing noise to the arm. Properly designed and well built suspension decks are probably better at isolating main bearing noise. I would think that decks with separate pods for the main bearing arm and motor on a suitable base structure would most likely provide the least amount of noise coupling between the main bearing and the arm and motor. I would expect that there are well executed versions of solid plinth and suspended decks but that in general that most commercial decks would follow the above stated order. That at least would be my expectation. If you have found otherwise I would be most interested to hear of your findings. Looking forward to more interesting discussion.
I don't have the ability to measure rumble but I can listen with a stethoscope. I would ask you to answer for me your last two questions since it would appear that you have measured the results. Main bearing noise will be substantial in a deck. Depending upon style and build I am sure that main bearing noise varies greatly. I would think that solid plinth decks are good at transmitting main bearing noise to the arm. Properly designed and well built suspension decks are probably better at isolating main bearing noise. I would think that decks with separate pods for the main bearing arm and motor on a suitable base structure would most likely provide the least amount of noise coupling between the main bearing and the arm and motor. I would expect that there are well executed versions of solid plinth and suspended decks but that in general that most commercial decks would follow the above stated order. That at least would be my expectation. If you have found otherwise I would be most interested to hear of your findings. Looking forward to more interesting discussion.
Oasis
Nanook, Your suggestion of Oasis as an isolating material seemed to be a good one, so I tried replacing the mounting crossbar on my arm with a 3 layer sandwich of two outer layers birch and an inner layer of Oasis. All three layers held together with CA for the butter. The top layer had a single tapped hole for the mounting screw which didn't contact the inner and bottom layer. The cartridge is fastened to the bottom layer with CA (cyanoacrylate). All three layers are about 1/16" thick. I didn't get any further with the Oasis sandwich as it promptly disintegrated. I doubt that it is possible to use that stuff in a cartridge isolator. If one can get it to hold together it will probably work as intended , but? As Moray points out it has to be rigid enough to hold the cartridge in the right orientation and stay there without self destructing. Rather that trying to figure out how to deal with Oasis I set to thinking about something stronger for the middle layer. As I have some thin sheets of balsa, decided to give it a try for the isolator layer. Rebuilt the mounting piece with a 1/16" thick piece of balsa in the middle. Mechanically this does the job. While balsa is far less dense than aluminum it still has a lot of air and as far as I can see makes a functional isolator. I'll write some more after using the gadget for a while. Meanwhile there are other things to try. Perhaps three little buttons and a whole lot of air will be better than the balsa. Will have to try them.
BillG
Nanook, Your suggestion of Oasis as an isolating material seemed to be a good one, so I tried replacing the mounting crossbar on my arm with a 3 layer sandwich of two outer layers birch and an inner layer of Oasis. All three layers held together with CA for the butter. The top layer had a single tapped hole for the mounting screw which didn't contact the inner and bottom layer. The cartridge is fastened to the bottom layer with CA (cyanoacrylate). All three layers are about 1/16" thick. I didn't get any further with the Oasis sandwich as it promptly disintegrated. I doubt that it is possible to use that stuff in a cartridge isolator. If one can get it to hold together it will probably work as intended , but? As Moray points out it has to be rigid enough to hold the cartridge in the right orientation and stay there without self destructing. Rather that trying to figure out how to deal with Oasis I set to thinking about something stronger for the middle layer. As I have some thin sheets of balsa, decided to give it a try for the isolator layer. Rebuilt the mounting piece with a 1/16" thick piece of balsa in the middle. Mechanically this does the job. While balsa is far less dense than aluminum it still has a lot of air and as far as I can see makes a functional isolator. I'll write some more after using the gadget for a while. Meanwhile there are other things to try. Perhaps three little buttons and a whole lot of air will be better than the balsa. Will have to try them.
BillG
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