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In Reply to: RE: Damping the Foating CDP Laser-Track Tray posted by fastcat on February 21, 2015 at 10:48:12
bought mine off ebay; no data. use very little!!1
Follow Ups:
Unclestu:
I find you work with the ferro fluid on the laser to be quite interesting!
Is it possible that you could start a thread where you would have 1 or 2
very close up pictures of the coils, and where exactly you are putting the
ferro fluid? A few arrows would also be good. It sounds like you are applying the fluid to the copper wound coils - is this between the coils and the magnets, or just on the coils (as in soaking into them)? Also, what do you use to apply the ferro fluid to the coils?
It sounds like the fluid you use is just something you found on e-bay... would you say that it is a typical ferro fluid as far as viscosity?
Many thanks for all you great tweak posts and in-sightes! I have worked
in the area of lab vibration analysis for decades, and an quite attuned to the concepts of damping movement, resonances, and vibration.
Dan
might take a while for photos. if you're patient I will eventually post.
I only soak the COIL assemblies. Since the correction motors move and can move a lot allowing too much ferro fluid to the point where it bridges the gap between the coils and the magnets or pole piece greatly increases the risk of splashing the fluid onto the optics. BIG NO NO!!! It is impossible to clean the mineral oil off(don't ask, but I've tried)
IF you place too much ferro fluid and you form a bridge, a piece of kleenex can absorb excess. I use a #5 stainless forceps to control the tissue, although you can fold it into into a triangle and apply.
Before placing ferro fluid, always analyze the motor assemblies. All laser assemblies have some kind of shield, usually plastic clip on.Remove to see the coil assemblies.Remember the lens has to move in two planes, so you may find four or even six coils. Each has to be loaded with about approximately equal amounts of ferro fluid (I've never been really critical because my mechanical dexterity is not so great these days.
If the laser motor coils are not overflowing but don't track well, I simply add more till I can see the ferro fluid build up in the coils themselves. The static magnetic fields will tend to hold the ferro fluid in place. Be careful as the magnets will draw the fluid straight to the pole pieces and magnets themselves. If that occurs I wipe the magnets and pole pieces clean to avoid bits flying off.
I used to use a diabetic insulin needle to apply the ferro fluid. Thin and it doesn't need much, but I do find it difficult to control the syringe itself. I use a toothpick these days and I actually have better control leaving a tiny droplet of ferro fluid on the very tip. As you approach the coils you can literally see the magnetic field "pull" the ferro fluid into the coils (power should NOT be on). HINT: move very slowly and carefully observe the tip and the destination...
Top photo is the common Sony KSM 2xx series.
Motor coils are large and easily accessible. Notice the larger square box is color coded copper and the two ring coils on each outboard side are coded gold. These represent the vertical and horizontal coils. All need to be soaked.
You can easily pull the motor coils to one side for greater ease of application. Even though applying from one side the ferro fluid will flow and usually equal out after a few seconds of playing (don't be surprised if sound is slightly distorted in the first few seconds.
Remember you want roughly equal amounts of ferrofluid on both sides,
Second photo is the ubiquitous Philips design CDM -12.
Motor coils are sandwiched between the magnet structure in a very tight position, Application is tricky as you need to approach from the front or rear accordingly (90 degrees to coil structure). Fluid will bleed to magnet so be prepared to wick away access
Great pics! Stu.
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