Hi Dave, I'am totally impressed with all that has been done.....its been rather amazing to hear of the extent to which you guys have pursued to derive the materials for the parts of the seismometer; and of course the patience and determination to bring such about! It will certainly be most interesting to hear about the even smaller (potential) vertical seismometer in time. That kind of time delayed anticipation torture (ha) is good for us. Take care, Meredith On Sat, Aug 15, 2009 at 7:43 PM, Dave Nelsonwrote: > Hi Meredith. > > The spring is cut to width on my personal shear and heat treated in the > home oven in the automatic cleaning mode. The heat treat significantly > increases the yield strength. The temperature is just right as measured with > a thermocouple. The width for the instrument pictured is 16 mm and thickness > is 12 mils. (Sorry for the mixed units -- our European friends will think > we can't make up our minds ) > > I have a large quantity of the raw material for the springs -- enough for > any conceivable quantity of instruments. I am working on the repeatability > in the shearing process. Right now I can do +- ~.15mm. > > As you suggest the period is a function of the spring length and adjusted > at the clamp. It sometimes takes a few tries but the process is quite easy. > The period and rough centering are done with the center capacitor plate PC > board removed to allow for a motion over large angle for convenience. The > final mass centering is done by adjusting the moveable mass either by eye > or using the LED's on the electronics board with the loop open. The > integrator is designed to hold center over a wide temperature range so > reentering is probably not necessary under all but the most severe climatic > temperature changes. We estimate +- 30C but that is not fully confirmed. > > > Actuator is homebrew based in a Neodymium magnet purchased on Ebay. The > coil is wound on a modified PAC plumbing part (1 1/4 Schedule 40 plug from > Lowes). It takes a few minutes of lathe work to make it . The coil is 770 > turns of # 32 for about 50 ohms and 15 N/A. I fabricate the magnet assembly > also but it does take some minor MIG tack welds. The materials are > available from Online Metals. > > There is another small mass at he coil attach point of ~ 10 grams. > > The overall size of the basic mechanism exclusive of the case is 4.5 x 9.5 > inches. I have a new (untried) design which will be 4.5 x 5 inches in a > somewhat different configuration which may allow for buoyancy compensation. > The new design is also easier to build or at least that is the goal. > > > Regards, Dave > > > > > Hi Dave,=A0I'am totally impressed with all that has been done.....its been ra= ther amazing to hear of the extent to whichyou guys have pursued to derive the materials for the parts of the sei= smometer; and of course the patienceand determination to=A0bring such about!=A0It will certainly be most interesting to hear about the even smaller (= potential) vertical seismometer in time.That kind of time delayed anticipation torture (ha) is good for us.=A0Take care, Meredith=A0
=A0On Sat, Aug 15, 2009 at 7:43 PM, Dave Nelson<davefnelson@.......> wrote:
Hi Meredith.=A0The spring is cut to width on my perso= nal shear and heat treated in the home oven in the automatic cleaning mode.= =A0 The heat treat significantly increases the yield strength. The temperat= ure is just right as measured with a thermocouple. The width for the instru= ment pictured is 16 mm and thickness is 12 mils.=A0 (Sorry for the mixed un= its -- our European friends will think we can't=A0 make up our minds )= =A0=A0=A0I have a large quantity of the raw = material for the springs -- enough for any conceivable quantity of instrume= nts. I am working on the =A0repeatability in the shearing process. Right no= w I can do +- ~.15mm.=A0As you suggest the period is=A0 a func= tion of the spring length and adjusted at the clamp. It sometimes takes a f= ew tries but the process is quite easy.=A0 The period and rough centering a= re done with the=A0 center capacitor plate PC board =A0removed to allow for= a motion over large angle for convenience. The final mass centering is don= e by adjusting the moveable mass =A0either by eye or using the LED's on= the electronics board with the loop open. The integrator is designed to ho= ld center over a wide temperature range so reentering is probably not neces= sary under all but the most severe climatic temperature changes. We estimat= e +- 30C=A0 but that is not fully confirmed.=A0=A0Actuator is homebrew based in a Neodym= ium magnet purchased on Ebay. The coil is wound on a modified PAC plumbing = part=A0 (1 1/4 Schedule 40 plug from Lowes).=A0=A0It takes a few minutes of= lathe work to make it=A0. The coil is 770 turns=A0of # 32 for about 50 ohm= s and 15 N/A. I fabricate the magnet assembly also but it does take some mi= nor=A0 MIG tack welds. The materials are available=A0=A0from Online Metals.==A0There is another small mass at he coil= attach point of=A0~ 10 grams.=A0=A0The overall size of the basic mechanis= m exclusive of the case is 4.5 x 9.5 inches. I have a new (untried) design = which will be 4.5 x 5 inches in a somewhat different configuration which ma= y=A0allow for=A0 buoyancy compensation. =A0The new design is also easier to= build or at least that is the goal.=A0=A0Regards, Dave=A0=A0=A0=A0[ Top ] [ Back ] [ Home Page ]