In a message dated 2008/02/14, shammon1@............. writes:

>        Put the coil on the arm and the magnet on the base. If you put a=20
> magnet on the arm, you will pick up a lot of magnetic noise from the house=
=20
> wiring, passing trains and lorries etc.
> Update 2/14/08: Thanks Chris, I=E2=80=99ll try mounting the coil on the bo=
om in the=20
> next revision. I never wanted to deal with the lead wires off the rear of=20=
the=20
> boom. Do you have any tips for frictionless lead wires?=20

Hi Steve,

       I mount two 2 mm banana sockets on the end of the arm and two nearby=20
on the frame. I use a ~4" loop of 38 AWG polyurethane insulated copper wire=20
soldered between two 2 mm banana plugs. You can solder the insulated wire=20
directly with a hot iron - the insulation just melts. I coat the plugs with=20=
Vaseline=20
after soldering and before insertion. The wires are bent to form a vertical=20
'hairpin' V. This has very little effect on the mechanical balance and a low=
=20
electrical resistance. I use twin core braid screened microphone cable to co=
nnect=20
up. You can use gold plated D twin plastic connectors. You can also mount=20
insulated pins on the arm and frame and solder wires directly, but dismounti=
ng=20
and adjusting the arm is easier if you can just unplug the connectors.

       The biggest improvement that you could make would be to replace the=20
point in a cup lower support with a 1/4" SS ball bearing on the end of the=20
mounting bolt and stick a SS blade flat or a WC triangle on the end of the a=
rm.=20
This would enable you to extend the period to at least 20 seconds.=20
       An alternative would be to buy a 1/8" tungsten carbide drill bit and=20
cut the shank in two. This would give you two cylinders for a crossed cylind=
er=20
rolling suspension. The vertical goes on the frame. Both systems work well.
       I don't know where point in a cup or knife edge 'bearings' originated=
,=20
but they automatically fail in use as you overload the tip / edge and they=20
then limit the performance. The 'knife edge' bearings used in chemical balan=
ces=20
don't actually have a knife edge! The 60 degree triangle is lapped to a tiny=
=20
radius cylinder rolling on a flat.

       I did a rough comparison with the output of a coil using a U Alnico=20
magnet and a Quad of NdFeB bar magnets on 1/4" backing plates. The improveme=
nt=20
was > x10. My original coil was about 6,000 turns, but I have reduced this t=
o=20
2,000 to keep the output from overloading my amplifier on the lowest gain=20
setting. See drawings on http://jclahr.com/science/psn/chapman/lehman/index.=
html

       I hope that this helps.

       Regards,

       Chris Chapman  =20
In a me=
ssage dated 2008/02/14, shammon1@............. writes:



     &=
nbsp; Put the coil on the arm and the magnet on the base. If you put a magne=
t on the arm, you will pick up a lot of magnetic noise from the house wiring=
, passing trains and lorries etc.

Update 2/14/08: Thanks Chris, I=E2=80=99ll try mounting the coil on the boo=
m in the next revision. I never wanted to deal with the lead wires off the r=
ear of the boom. Do you have any tips for frictionless lead wires? 



Hi Steve,



       I mount two 2 mm banana sockets on the=20=
end of the arm and two nearby on the frame. I use a ~4" loop of 38 AWG polyu=
rethane insulated copper wire soldered between two 2 mm banana plugs. You ca=
n solder the insulated wire directly with a hot iron - the insulation just m=
elts. I coat the plugs with Vaseline after soldering and before insertion. T=
he wires are bent to form a vertical 'hairpin' V. This has very little effec=
t on the mechanical balance and a low electrical resistance. I use twin core=
 braid screened microphone cable to connect up. You can use gold plated D tw=
in plastic connectors. You can also mount insulated pins on the arm and fram=
e and solder wires directly, but dismounting and adjusting the arm is easier=
 if you can just unplug the connectors.



       The biggest improvement that you could=20=
make would be to replace the point in a cup lower support with a 1/4" SS bal=
l bearing on the end of the mounting bolt and stick a SS blade flat or a WC=20=
triangle on the end of the arm. This would enable you to extend the period t=
o at least 20 seconds. 

       An alternative would be to buy a 1/8" t=
ungsten carbide drill bit and cut the shank in two. This would give you two=20=
cylinders for a crossed cylinder rolling suspension. The vertical goes on th=
e frame. Both systems work well.

       I don't know where point in a cup or kn=
ife edge 'bearings' originated, but they automatically fail in use as you ov=
erload the tip / edge and they then limit the performance. The 'knife edge'=20=
bearings used in chemical balances don't actually have a knife edge! The 60=20=
degree triangle is lapped to a tiny radius cylinder rolling on a flat.



       I did a rough comparison with the outpu=
t of a coil using a U Alnico magnet and a Quad of NdFeB bar magnets on 1/4"=20=
backing plates. The improvement was > x10. My original coil was about 6,0=
00 turns, but I have reduced this to 2,000 to keep the output from overloadi=
ng my amplifier on the lowest gain setting. See drawings on http://jclahr.co=
m/science/psn/chapman/lehman/index.html



       I hope that this helps.



       Regards,



       Chris Chapman