PSN-L Email List Message

Subject: RE: Lehman modification
From: "Steve Hammond" shammon1@.............
Date: Wed, 27 Jun 2001 13:21:49 -0700


Hi Dan,  I use a high voltage test probe (Very sharp point) screwed into a
tapped hole in the end of the boom, resting agents a cup drilled in the
business end of an allan screw. I then use a #10 machine wire with
turnbuckle for the upper pivot point. You can see it at:
http://pw2.netcom.com/~shammon1/equip.htm

To eliminate any rocking side to side, there is a Y shaped bridle in the
upper wire. To adjust the period you use the allan screw. To level the boom
you use the turnbuckle. While this design works well, I think the double
wire design mentioned some time ago by John Lahr is more sensitive. Both the
double wire and point in cup design eliminate the issue with the knife edge
walking down the backstop due to gravity. However there are negative points
in every design. In the point in cup design, you have to replace the point
about every six months to keep up the performance. Both the double wire and
point in cup design cannot withstand any type of strong handling and will be
damaged if bumped hard enough.

Regards, Steve Hammond  PSN Aptos, California

  -----Original Message-----
  From: psn-l-request@.............. [mailto:psn-l-request@.................
Behalf Of dan stevens
  Sent: Wednesday, June 27, 2001 5:57 PM[Steve Hammond]
  To: psn-l@..............
  Subject: Re: Lehman modification


  My idea was to remove the lower cross-beam from between my two vertical
posts.  Replace it with a thin guitar string, tightly strung horizontally
between the two posts.  Then have the guitar string seated in a slot in the
end of the boom. Since suggesting this though, I've realized this would be
difficult to keep constant over time without dickering with it.  What about
replacing the string with say a bicycle spoke? It's just an idea, I'm fairly
new at this and you guys are the pros. I think I'm going to turn this one
into the ball-bearing design, and then make something different for a second
one. I'd be interested in seeing plans for a vertical sensor if anyone knows
where some are. -dan


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Hi=20 Dan,  I use a high voltage test probe (Very sharp point) screwed = into a=20 tapped hole in the end of the boom, resting agents a cup drilled in the = business=20 end of an allan screw. I then use a #10 machine wire with turnbuckle for = the=20 upper pivot point. You can see it at: http://pw2.netcom.com/= ~shammon1/equip.htm 
 
To=20 eliminate any rocking side to side, there is a Y shaped = bridle in=20 the upper wire. To adjust the period you use the allan screw. To level = the boom=20 you use the turnbuckle. While this design works well, I think the double = wire=20 design mentioned some time ago by John Lahr is more sensitive. Both the = double=20 wire and point in cup design eliminate the issue with the knife edge = walking=20 down the backstop due to gravity. However there are negative points=20 in every design. In the point in cup design, you have to = replace the=20 point about every six months to keep up the performance. Both the double = wire=20 and point in cup design cannot withstand any type of strong handling and = will be=20 damaged if bumped hard enough.
 
Regards, Steve Hammond  PSN Aptos, = California
 
-----Original Message-----
From: = psn-l-request@................. [mailto:psn-l-request@...............On Behalf Of dan=20 stevens
Sent: Wednesday, June 27, 2001 5:57 PM[Steve=20 Hammond]   
To:=20 psn-l@..............
Subject: Re: Lehman=20 modification

My idea was to remove the lower cross-beam from between my two = vertical=20 posts.  Replace it with a thin guitar string, tightly=20 strung horizontally between the two posts.  Then have the = guitar=20 string seated in a slot in the end of the boom. Since suggesting this = though,=20 I've realized this would be difficult to keep constant over time = without=20 dickering with it.  What about replacing the string with say a = bicycle=20 spoke? It's just an idea, I'm fairly new at this and you guys are the = pros. I=20 think I'm going to turn this one into the ball-bearing design, and = then make=20 something different for a second one. I'd be interested in seeing = plans for a=20 vertical sensor if anyone knows where some are. -dan


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Larry Cochrane <cochrane@..............>