In a message dated 2006/10/12, tchannel@.............. writes:

> Hi Chris, 
> Q   By V HAIRPINS, do you mean a piece of wire which forms a single "V" 
> shape?  One for each wire, with no twist or turns?

Hi Ted,

       One ~straight piece of wire bent into a V / U shape with ~straight 2" 
sides and soldered to the pins at the ends, for each connection (like a hair 
pin). This works fine with the 36 AWG Cu wire that I use.

> Q  Just curious, about the magnet layout. Why are they arranged N,S on the 
> top and S,N on the bottom?
> If one used a horseshoe magnet it would be Just N,S

       With a horse shoe magnet, you have to offset the position of the coil 
away from the poles, so that it experiences about 1/2 the maximum field. If 
the coil moves one way, the field increases, if it moves the other way the field 
decreases. But you are starting from the half field position and the field 
strength is ~S shaped - not very linear when the Lehman mass drifts in position!

       In my arrangement one winding of the coil moves in gap directly 
between a N pole on one face and a S pole on the other, carrying the full maximum 
field. You have opposite field directions for the two halves of the coil, so 
that the induced voltages add. This increases both the linearity and the output 
very considerably. The field strength is nearly constant anywhere over one 
pole. 

       The return path from the back of the bar magnets is through the mild 
steel backing plates. Magnetically, this is a 'short circuit'. The N+S magnets 
only have to drive the external field across the central gap. You should get 
over 5x the field of an Alnico magnet. This allows the coil to be smaller while 
still giving an increased output.

       Another way of viewing the system is to consider the net field through 
the coil when it is centralised. You have two strong constant fields in 
opposite directions over the two halves, which balance out. Any movement applies a 
strong net field through the coil. Using the flat square NdFeB magnets makes 
this highly effective layout easy and inexpensive to achieve.      

       Regards,

       Chris Chapman
In a me=
ssage dated 2006/10/12, tchannel@.............. writes:



Hi Chris, 

Q   By V HAIRPINS, do you mean a piece of wire which forms a sing=
le "V" shape?  One for each wire, with no twist or turns?



Hi Ted,



       One ~straight piece of wire bent into a=
 V / U shape with ~straight 2" sides and soldered to the pins at the ends, f=
or each connection (like a hair pin). This works fine with the 36 AWG Cu wir=
e that I use.



Q  Just curious, about th=
e magnet layout. Why are they arranged N,S on the top and S,N on the bottom?=


If one used a horseshoe magnet it would be Just N,S




       With a horse shoe magnet, you have to o=
ffset the position of the coil away from the poles, so that it experiences a=
bout 1/2 the maximum field. If the coil moves one way, the field increases,=20=
if it moves the other way the field decreases. But you are starting from the=
 half field position and the field strength is ~S shaped - not very linear w=
hen the Lehman mass drifts in position!



       In my arrangement one winding of the co=
il moves in gap directly between a N pole on one face and a S pole on the ot=
her, carrying the full maximum field. You have opposite field directions for=
 the two halves of the coil, so that the induced voltages add. This increase=
s both the linearity and the output very considerably. The field strength is=
 nearly constant anywhere over one pole. 



       The return path from the back of the ba=
r magnets is through the mild steel backing plates. Magnetically, this is a=20=
'short circuit'. The N+S magnets only have to drive the external field acros=
s the central gap. You should get over 5x the field of an Alnico magnet. Thi=
s allows the coil to be smaller while still giving an increased output.



       Another way of viewing the system is to=
 consider the net field through the coil when it is centralised. You have tw=
o strong constant fields in opposite directions over the two halves, which b=
alance out. Any movement applies a strong net field through the coil. Using=20=
the flat square NdFeB magnets makes this highly effective layout easy and in=
expensive to achieve.      



       Regards,



       Chris Chapman