Hi, is the 15 to 20 second free swing dampened? Or does 'free' mean 
undampener? Please remember i am new to all this. Thanks, geofff<><
----- Original Message ----- 
From: "Connie and Jim Lehman" 
To: 
Sent: Saturday, October 22, 2005 10:43 AM
Subject: Re: Horizontal Pendulum]


> Geoffery--Thanks for your interest in seismology and the "Lehman 
> horizontal"
> design.  I am puzzled a bit by your use of "shims"-- my idea of shims has
> been only in work demanding small changes in distance--like leveling a
> table, or a piece of scientific apparatus.  The usual shims in precision
> work are sheets of metal with so many l/1000ths of an inch in
> thickness--otherwise known as mills} Since the seismo base is a tripod--
> (for stability)  shim material can be used to balance and level the 
> system.
>  I am not sure what version of sensor plans you are following, but I
> suggest that you keep construction simple with a wire hinge at the top, 
> and
> a knife edge on the boom end.  After you get that working with a 15-20 sec
> free swing, properly damped, you can refine and modify your design as you
> like.  To get a good "garden gate" swing the upper wire hinge (tensional)
> should be about 1/4th inch off the vertical with the compressional knife
> edge.
>   Best wishes,   Jim
>
> ----- Original Message -----
> From: "Larry Cochrane" 
> To: 
> Sent: Saturday, October 22, 2005 2:36 AM
> Subject: [Fwd: Horizontal Pendulum]
>
>
>>
>> -------- Original Message --------
>> Subject: Horizontal Pendulum
>> Date: Fri, 21 Oct 2005 20:33:15 -0400
>> From: KATHRYN ROBERTS 
>> To: Larry Cochrane 
>>
>> Larry, thank you for your reply. The PSN-L@............... did not work.
> (i don't
>> have good computer skills.) Would you post this on the list? i'm new to
> the list and
>> seismology. i've enjoying reading the posts and have been thinking about 
>> a
> horizontal
>> pendulum Lehman type seismo using metal shims (what is the best material
> for shims
>> and best thickness?)    Anyway, the horizontal pendulum would be 
>> supported
> by shims
>> above and below the pendulum that are ninety degrees perpendicular to the
> horizontal
>> axis of the pendulum.  The upper shim would be attached to the 'mast' 
>> and
> then to a
>> tube or rod that is attached to the pendulum, again with the linear axis
> will be
>> perpendicular to the pendulum's horizontal plane.  This would place the
> upper shim in
>> tension. The lower shim is also placed in tension by attaching the end
> away from the
>> coil to the above mentioned tube or pipe that is attached to the 
>> pendulum.
> The lower
>> shim will run away from the mast towards the coil. One thing that will
> have to be
>> determined is the position were the upper and lower tubes join the
> pendulum. The
>> tubes' positions would determine the flex positon of the shims, hopefully
> to be able
>> to find the point of greatest flexion of the shims with the lowest torque
> needed to
>> cause the flex or bending of the shim. Have many people tried this? How
> did it work?
>> Thanks, geofffrey roberts, Crystal River, Florida
>>
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>
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