<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">
<font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">Hi All,</span></font><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">On behalf of Mitch Withers, Greg Steiner, and myself, here is an exchange of the shake table available at CERI in Memphis:</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">----------------------------------------------------------------------------------------------------</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: 12.0px Helvetica">John,</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: 12.0px Helvetica">Thanks for the posting on accelerometer testing.</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: 12.0px Helvetica">FYI, CERI has an MTS hydraulic shaker that operates from DC to about 100 Hz (accurate to about 50 Hz). This shaker has no seals around the piston to reduce hysteresis in the table motion (scavenger pumps suck the oil out of the end caps). The table rides on high pressure oil bearings and is pretty smooth. Vertical and horizontal motions are possible, but rotation around the horizontal axis is uncontrolled [when vertical?].</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: 12.0px Helvetica">While I can't speak for Mitch anymore, I'm sure he would make it available to you, if you need some high amplitude shaking.</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: 12.0px Helvetica">It has a peak acceleration of 7G at about 10 Hz and a maximum stroke of 2" p-p. The main problem is the background noise of all the HVAC units in the building. We routinely did our cals in the middle of the night to get about a 12-18 db improvement in background noise. [Table] calibration was checked occasionally using a micrometer and a recently calibrated LVDT. Accuracies of 1-2 % were possible using an FFT to single out the motion of interest and averaging over 10 to 100 cycles (pretty damn slow at 10 seconds period!).</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: 12.0px Helvetica">Greg</font></div></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">----------------------------------------------------------------------------------------------------</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: normal normal normal 12px/normal Helvetica; ">Hi Greg,</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: normal normal normal 12px/normal Helvetica; ">Thanks for the info. Sounds like a very interesting instrument, particularly at high frequencies.</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: normal normal normal 12px/normal Helvetica; ">On the Anorads we can push 5 kg to 4 g at 32 Hz, but I smoked one of the linear motors by running it at 64 Hz for an extended period -- one can get only 5-10 s safely at that frequency.</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: normal normal normal 12px/normal Helvetica; ">I think air or oil bearings will be essential to creating any shaker that is quiet enough for definitive cross-axis work and that long baselines between bearings will be needed to constrain rotations tightly enough, so I was gratified to hear of your oil bearings -- how much trouble are they to maintain?</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: normal normal normal 12px/normal Helvetica; ">Cheers,</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: normal normal normal 12px/normal Helvetica; ">John</font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div></div><div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">----------------------------------------------------------------------------------------------------</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: 14.0px Helvetica"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">John,</span></font></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: 14.0px Helvetica"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">The table actuator can be mounted in either vertical or horizontal position. It can shake up to about 150 lbs. They have a an overhead crane with a chain winch that picks up the weight of the actuator, then you can tilt it and reinstall the mounting bolts in the other plane. The table sits on a concrete reaction mass and there is a gussetted right angle plate with 2 sets of mounting holes mounted to the reaction mass.</span></font></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: 14.0px Helvetica"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">The oil bearings do not require any maintenance other than every 10 years or so replacing the hydraulic fluid. They are a standard design feature in all hydraulic shakers -- the custom part was the removal of the o-ring dydnamic seals. The only problem i had was once forgetting to turn the scavenger pumps on, in about a minute you have a big puddle of oil around the base of the table!</span></font></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: 14.0px Helvetica"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">I hesitated to post it to the blog, since I retired from CERI and didn't want to volunteer Mitch or the CERI folks for something . I just thought it might come in handy if you neede it for some testing. feel free to pass it on to interested parties.</span></font></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 14px/normal Helvetica; min-height: 17px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">Greg</span></font></div></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">----------------------------------------------------------------------------------------------------</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">The shake table is certainly open to anyone at ASL who wants to use it but as Greg said, you have to do it in the middle of the night. We're located in the middle of a 1M+ population metro area on top of a kilometer of sediments that shake like jello during the day. And then there's the railway within about 300 meters or so with about 40 trains per day.</span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">It hasn't been tested let alone NIST traceable calibrated in several years. I guess we "trust" the notion that today's sensors have fewer moving parts and are more predictable (when they're working) than in years past. Besides, it would take ten years to swap out all the sensors in the network for recal.</span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">Mitch</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div></div></div></div><div><span class="Apple-style-span" style="border-collapse: separate; font-variant: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-variant: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-variant: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-variant: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">----------------------------------------------------------------------------------------------------</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">Cheers,</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">John</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">John R Evans</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><a href="mailto:jrevans@usgs.gov">jrevans@usgs.gov</a></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">Usually in Menlo Park:</span></font></div><div><div class="MsoPlainText"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">U.S. Geological Survey</span></font></div><div class="MsoPlainText"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">345 Middlefield Rd, MS-977</span></font></div><div class="MsoPlainText"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">Menlo Park CA 94025-3591</span></font></div></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">650-329-4753</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">Intermittently in Albuquerque:</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">Albuquerque Seismological Laboratory</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">U.S. Geological Survey</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">P.O. Box 82010</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">Albuquerque NM 87198-2010</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">505-846-1793</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div></span></span></span><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div></span><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br class="Apple-interchange-newline"></span></font><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br class="Apple-interchange-newline"><br class="Apple-interchange-newline"></span> </font></div><br></div></body></html>