PSN-L Email List Message

Subject: Re: Different types of Pendulums
From: tchannel1@............
Date: Sat, 27 Oct 2007 17:20:04 -0600

Hi Folks,   I found the wed site again.  The two I mentioned are 
called "Balanced-Like" and "Nearly Balanced"
Just wondering if anyone has worked with them.  As I said I made a mock up, 
with no luck.  But maybe my mock up was not done correctly.

----- Original Message ----- 
From: "John Lahr" 
Sent: Saturday, October 27, 2007 4:04 PM
Subject: Re: Different types of Pendulums

> The "airplane-type" design is basically a "solid pendulum."  Although the 
> period can be made
> very long, the sensitivity becomes correspondingly low.  I don't recommend 
> this design.
> Cheers,
> John
> At 02:44 PM 10/27/2007, you wrote:
>>In a message dated 27/10/2007 22:23:56 GMT Daylight Time, 
>>tchannel1@............ writes:
>>Hi Folks, Sometime in the past I saw a web site describing different types 
>>of pendulums used in sensors.  I don't remember their names, but
>>1.  one was a long vertical rod, with a center pivot, it contained a mass 
>>at the top of the rod and a mass at the bottom of the rod.
>>My question has to do with 1.  I thought this pendulum (positioned like an 
>>airplane propeller) was able to adjust it's period by moving the top and 
>>or bottom mass, up or down the rod?
>>I made a simply mock up of this illustration, but was not successful in 
>>any way. Can one adjust this arrangement to result in an extended period? 
>>Does anyone know of this web site or one similar?
>>Hi Ted,
>>     There are several possible systems, but you need to suspend the 
>> pendulum near the middle, a small height above the centre of gravity. 
>> This gives a high moment of inertia due to the masses at the ends and the 
>> small restoring force due to 2x mass operating just below the suspension 
>> axis. It should work fine. You can also vary the position of one of the 
>> masses.
>>     Regards,
>>     Chris Chapman
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