Dave Nelson dave.nelson@............... Subject: New Seismo ok got around to taking a pic of the new Lehman ttp://www.sydneystormcity.com/IMGP2023a.jpg still waiting for the first decent quake M6+ to see its response ill then I am guessing at the amount of dampening I need for it. Hi Dave, It looks nice! What period have you set it to, please? I suggest that you aim for 25 seconds. I can't quite see how you have attached the mass plates to=20 the arm. Are they crimped / punched in place?=20 How does the variable damping work ? I can't see that either!=20 See http://www.jclahr.com/science/psn/chapman/lehman/index.html=20 I stick a label with a vertical line on it onto the mass and=20 view the line with a magnifying glass through a transparent=20 plastic ruler. I deflect the mass 10 mm and release it. The=20 mass moves back toward the balance point and usually past it.=20 I observe how far it moves past the balance point. I increase=20 / decrease the damping until the mass goes 1/2 mm past the=20 balance point and then moves slowly back to zero without any=20 oscillations. The arm is then set to 0.7 critical damping.=20 The amount of damping needed decreases as the set period is=20 increased. I hope that this helps. Regards, Chris Chapman= Dave Nelson dave.nelson@optu= snet.com.au
Subject: New Seismo
ok got= around to taking a pic of the new Lehman ht= tp://www.sydneystormcity.com/IMGP2023a.jpg still waiting for the first decent quake M6+ to see its response Till then I am guessing at the amount of dampening I need for it. Hi Dave,= It looks nice! What period have you set it to, please?= FONT>I suggest = that you aim for 25 seconds.I can't quite see how you have attached the mass plates= tothe = arm. Are they crimped / punched in place?How does the variable damping work ? I ca= n't see that either!See http://www.jclahr.com/science/psn/chapman/lehman/index.html= A> I sti= ck a label with a vertical line on it onto the mass and<= PRE style=3D"FONT-SIZE: 9pt">view the line with a magnif= ying glass through a transparentplastic ruler. I deflect the mass 10 mm and releas= e it. Themass moves back toward the balance point and usually past it.I observe how far i= t moves past the balance point. I increase/ decrease the damping until the mass go= es 1/2 mm past thebalance point and then m= oves slowly back to zero without anyoscillations. The arm is then set to = 0.7 critical damping.<= FONT size=3D3>The amount of damping needed decreases as the set period is <= /FONT>increased= ..I h= ope that this helps.Regards, Chris Chapman