## PSN-L Email List Message

From: ChrisAtUpw@.......
Date: Thu, 13 Mar 2008 12:42:19 EDT

```In a message dated 2008/03/13, gpayton880@....... writes:

> In our standard garden-gate configuration:   Consider a traditional right
> triangle with side A (vertical) & B (base) with hypotenuse C.  If a mass is
> attached to the BC end, I assume that there is an applied force to keep point
> AB against the pivot, whichever method is used there.
>
> My question is, "Does it matter what the angle of the hypotenuse is?  Would,
> say a 30 degree angle work as well as a 45 degrees, or is there a cutoff
> angle to maintain the horizontal force against the pivot?"
>
> This could directly affect the height of A when constructing a Lehman.

Hi Gerry,

The angle should preferably be between 30 and 45 degrees. The load on
the bottom bearing is mass / tan(angle). The load on the wire suspension is
mass / sin(angle).
I use and 18" vertical on a 30" lower support. The length from the
bearing to the CENTRE of the mass is min about 22" to give a 1.5 second pendulum.
I use ~24". The bottom bearing is maybe 1/2" out from the frame. The mass
sticks out a bit over 1.5" and you need ~3" for the sensor magnet frame and
clearance and 1" minimum for the levelling screw. The suspension maybe 1/2" down
from the top and the boom 2.5" to 3" up depending on the mass shape / clearance
and the damper blade height. This has to be chosen to fit to the centre of the
mass and fit in the damper magnet fitting which slides on the lower frame.
Hope that this helps.

Regards,

Chris
In a me=
ssage dated 2008/03/13, gpayton880@....... writes:

In our standard garden-gate con=
figuration:   Consider a traditional right triangle with side A (v=
ertical) & B (base) with hypotenuse C.  If a mass is attached to th=
e BC end, I assume that there is an applied force to keep point AB against t=
he pivot, whichever method is used there.

My question is, "Does it matter what the angle of the hypotenuse is?  W=
ould, say a 30 degree angle work as well as a 45 degrees, or is there a cuto=
ff angle to maintain the horizontal force against the pivot?"

This could directly affect the height of A when constructing a Lehman.

Hi Gerry,

The angle should preferably be between=20=
30 and 45 degrees. The load on the bottom bearing is mass / tan(angle). The=20=
load on the wire suspension is mass / sin(angle).
I use and 18" vertical on a 30" lower s=
upport. The length from the bearing to the CENTRE of the mass is min about 2=
2" to give a 1.5 second pendulum. I use ~24". The bottom bearing is maybe 1/=
2" out from the frame. The mass sticks out a bit over 1.5" and you need ~3"=20=
for the sensor magnet frame and clearance and 1" minimum for the levelling s=
crew. The suspension maybe 1/2" down from the top and the boom 2.5" to 3" up=
depending on the mass shape / clearance and the damper blade height. This h=
as to be chosen to fit to the centre of the mass and fit in the damper magne=
t fitting which slides on the lower frame.
Hope that this helps.

Regards,

Chris
```