Chris,

Thank you very much for the information.

You mentioned an instability issue that I have experienced with the razor
blade hinge point.

If I slightly jar the boom, in a sideways motion, the razor blade end will
rock back and forth a few cycles until it reaches equilibrium. I can see how
your twin wire design would eliminate this issue. I am building another AS-1
and will incorporate your hinge modification.

Please let me know what you think about the following to eliminate this
lateral instability.

I have an idea (using my current razor blade design) that involves placing a
small magnet on the sensor end of the boom. The magnet would be mounted at a
right angle referenced to the long length of the boom. Two magnets would
then be mounted (on pedestal's) on each side of the boom.

The force from these two magnets would repel the force of the boom magnet
and hopefully add some dynamic stability and eliminate any horizontal
rocking motion of the boom.

It would also appear that this arrangement would add some damping effect,
and if constructed and adjusted correctly, may allow the elimination of the
current damping system.

Changing the subject here...

Regarding your advice on gluing the spring ends is well taken. I will do
this.

Also, your newly designed magnet block and coil, I will incorporate in my
new AS-1 build.
I do have quite a bit of noise, electrostatic, and I like the idea of
shielding the coil using this design.

Again Chris, thank you for all the support you give us!

Richard









On Sat, Jan 29, 2011 at 7:37 AM, Christopher Chapman wrote:

>        Subject: AS-1 Type Sensor
>
>
>
>  I would appreciate any comments regarding my AS-1 type sensor. It's close
> to the original design. I did not like the knife edge aluminum boom attached
> to a score mark in the aluminum mast, so I modified the boom to mast
> attachment. I am using two razor blades. One on the boom and one on the
> mast. Hardened steel on steel. Friction is much less. Free running
> oscillations have a much longer duration. Does anyone have a better
> suggestion? I would like to hear from you.
>
> See my pic's here:  http://picasaweb.google.com/cfi2fly/MyPictures#
>
> Also, Chris, if you read this, if I reversed the coil and magnet, would the
> effort be worth the results?
>
> Hi Richard,
>
>     I agree about the original design, The arm needs to be held fairly
> rigidly to prevent it from rotating about it's long axis, or swinging from
> side to side. You can use a twin wire suspension in tension as shown on
> http://www.oregonshakes.com/temp/DesignDrawings4.pdf or an old type double
> edged safety razor blade, in compression. This involves clamping one blade
> to the beam and the other to the vertical post. I blunt the blades on an
> emery stone first to avoid handling accidents. The two loop ends of the
> blade do the flexing. I have broken the ends of blades. The edges are fairly
> sharp, but I have never observed a section 'flying off'. You can only use
> this suspension for a vertical sensor.
>
>     The horizontal arm on the AS-1 is a very hard non magnetic alloy, nol
> an Aluminum alloy.
>
>     The ends of the spring should ideally be straightened and clamped. Loop
> ends fixed by an eyelet tend to be noisy. You could also try gluing the loop
> ends in position? Two component Acrylic glues are much better structural
> glues than Epoxies. They set strong and tough and have a short setting time,
> rather than strong but brittle with a long setting time.
>
>      The benefits of reversing the coil and the magnet depend on how much
> noise you are picking up. The Alnico U magnets do not have a very strong
> field, the coil is a bit bulky and the output is not very high. You would do
> much better to use a quad NdFeB magnet block. See the designs at
> www.jclahr.com/science/psn/chapman/lehman/index.html You can get 10x the
> voltage output this way without any difficulty. Also, the 1/4" mild steel
> backing plates provide an effective electrostatic and magnetic screen for
> the pickup coil. I suggest that you use a brass mass. There is also a design
> for an AS-1 magnetic damper on the website.
>
>      I hope that these comments are helpful.
>
>      Regards,
>
>     Chris Chapman
>
Chris,
=A0
Thank you very much for the information. 
=A0
You mentioned an instability issue that I have experienced with the ra=
zor blade hinge point.
=A0
If I slightly jar the boom, in a sideways motion, the razor blade end =
will rock back and forth a few cycles until it reaches equilibrium. I can s=
ee how your twin wire design would eliminate this issue. I am building anot=
her AS-1 and will incorporate your hinge modification.

=A0
Please let me know what you think about the following to eliminate thi=
s lateral instability.
=A0
I have an idea (using my current=A0razor blade design) that involves p=
lacing a small magnet on the sensor end of the boom. The magnet would be mo=
unted at a right angle referenced to the long length of the boom. Two magne=
ts would then be=A0mounted (on pedestal's)=A0on each side of the boom.<=
/div>

=A0
The force from these two magnets would repel the force of the boom mag=
net and hopefully add some dynamic stability and eliminate any=A0horizontal=
 rocking motion of the boom.
=A0
It would also appear that this arrangement would add some damping effe=
ct, and if constructed and adjusted correctly, may allow the elimination of=
 the current damping system.
=A0
Changing the subject here...
=A0
Regarding your advice on gluing the spring ends is well taken. I will =
do this.
=A0
Also, your newly designed magnet block and coil, I will incorporate in=
 my new AS-1 build.
I do have quite a bit of noise, electrostatic, and I like the idea of =
shielding the coil using this design.
=A0
Again Chris, thank you for all the support you give us!
=A0
Richard
=A0
=A0
=A0
=A0
=A0
=A0
=A0

=A0
On Sat, Jan 29, 2011 at 7:37 AM, Christopher Cha=
pman <chrisatupw=
@.......> wrote:
















=
Subject: AS-1 Type Sensor
=

=A0

=A0

I would appreciate any comments regarding my AS-1 type sensor. It'=
s close to the original design. I did not like the=A0knife edge=A0aluminum =
boom=A0attached to a score mark in the aluminum mast, so I=A0modified the b=
oom=A0to mast attachment. I am using two razor blades. One on the boom and =
one on the mast. Hardened steel on steel. Friction is much less. Free runni=
ng oscillations have a much longer duration. Does anyone have a better sugg=
estion? I would like to hear from you.

=A0
See my pic's here:=A0 http://picasaweb.google.com/cfi2fly/MyPict=
ures#
=A0
Also, Chris, if you read this,=A0if I reversed the coil and magnet, wo=
uld the effort be worth the results?
=A0
Hi Richard,
=A0
=A0=A0=A0 I agree about the original design, The arm needs to be held =
fairly rigidly to prevent it from rotating about it's long axis, or swi=
nging from side to side.=A0You can use a twin wire suspension in tension as=
 shown=A0on=A0http://www.oregonshakes.com/temp=
/DesignDrawings4.pdf or an old type=A0double edged safety=A0razo=
r blade, in compression. This involves clamping one blade to the beam and t=
he other to the vertical post. I blunt the blades on an emery stone first t=
o avoid handling accidents. The two=A0loop ends of the blade do the=A0flexi=
ng. I have broken the ends of blades. The edges are fairly sharp, but I hav=
e never observed a section 'flying off'. You can only use this susp=
ension for a vertical sensor.

=A0
=A0=A0=A0 The horizontal arm on the AS-1 is a very hard non magnetic a=
lloy, nol an Aluminum alloy.
=A0
=A0=A0=A0 The ends of the spring should ideally be straightened and cl=
amped. Loop ends fixed by an eyelet tend to be noisy. You could also try gl=
uing=A0the loop ends in position? Two component Acrylic glues are much bett=
er structural glues=A0than Epoxies. They set strong and tough and have a sh=
ort setting time, rather than strong but brittle with a long setting time.<=
/div>

=A0
=A0=A0=A0=A0 The benefits of reversing the coil and the magnet depend =
on how much noise you are picking up. The Alnico U magnets do not have a ve=
ry strong field, the coil is a bit bulky and the=A0output is not very high.=
 You would do much better to use a quad NdFeB magnet block. See the designs=
 at www.jclahr.com/science/psn/chapman/lehman/index.html=
=A0You can get 10x the voltage output this way without any difficulty. Also=
, the 1/4" mild steel backing plates provide an effective electrostati=
c and magnetic screen for the pickup coil. I suggest that you use a brass m=
ass. There is also=A0a design for an AS-1 magnetic damper on the website.

=A0
=A0=A0=A0=A0 I hope that these comments are helpful.
=A0
=A0=A0=A0=A0 Regards,
=A0
=A0=A0=A0 Chris Chapman