PSN-L Email List Message

Subject: Re: Real time traces
From: Barry Lotz barry_lotz@.............
Date: Sun, 16 Aug 2009 04:18:19 -0700 (PDT)


Dave
I'm interested in finding out more and impressed also. I reduced the size o=
f the STM style vertical 12" but like your design. Didn't you try a hacksaw=
 blade(s)=A0 before? I don't remember the thickness but would the taping bl=
ade material STM mentioned work? I'm not sure about my heat treating abilit=
ies (proper annealing etc). I have read Bretts excellent documentation in t=
he past.
Regards
Barry


--- On Sat, 8/15/09, Dave Nelson  wrote:

From: Dave Nelson 
Subject: Re: Real time traces
To: psn-l@..............
Date: Saturday, August 15, 2009, 6:43 PM

=0A=0A =0A =0A=0AHi Meredith.=0A=A0=0AThe spring is cut to width on my pers=
onal shear and =0Aheat treated in the home oven in the automatic cleaning m=
ode.=A0 The heat =0Atreat significantly increases the yield strength. The t=
emperature is just right =0Aas measured with a thermocouple. The width for =
the instrument pictured is 16 mm =0Aand thickness is 12 mils.=A0 (Sorry for=
 the mixed units -- our European =0Afriends will think we can't=A0 make up =
our minds )=A0=0A=A0=0A=A0I have a large quantity of the raw material =0Afo=
r the springs -- enough for any conceivable quantity of instruments. I am =
=0Aworking on the =A0repeatability in the shearing process. Right now I can=
 do =0A+- ~.15mm.=0A=A0=0AAs you suggest the period is=A0 a function of =0A=
the spring length and adjusted at the clamp. It sometimes takes a few tries=
 but =0Athe process is quite easy.=A0 The period and rough centering are do=
ne with =0Athe=A0 center capacitor plate PC board =A0removed to allow for a=
 motion =0Aover large angle for convenience. The final mass centering is do=
ne by adjusting =0Athe moveable mass =A0either by eye or using the LED's on=
 the electronics =0Aboard with the loop open. The integrator is designed to=
 hold center over a wide =0Atemperature range so reentering is probably not=
 necessary under all but the most =0Asevere climatic temperature changes. W=
e estimate +- 30C=A0 but that is not =0Afully confirmed.=0A=A0=0A=A0=0AActu=
ator is homebrew based in a Neodymium magnet =0Apurchased on Ebay. The coil=
 is wound on a modified PAC plumbing part=A0 (1 =0A1/4 Schedule 40 plug fro=
m Lowes).=A0=A0It takes a few minutes of lathe =0Awork to make it=A0. The c=
oil is 770 turns=A0of # 32 for about 50 ohms and =0A15 N/A. I fabricate the=
 magnet assembly also but it does take some minor=A0 =0AMIG tack welds. The=
 materials are available=A0=A0from Online Metals. =0A=0A=A0=0AThere is anot=
her small mass at he coil attach point =0Aof=A0~ 10 grams.=A0 =0A=A0=0AThe =
overall size of the basic mechanism exclusive =0Aof the case is 4.5 x 9.5 i=
nches. I have a new (untried) design which will be 4.5 =0Ax  5 inches in a =
somewhat different configuration which may=A0allow for=A0 =0Abuoyancy compe=
nsation. =A0The new design is also easier to build or at least =0Athat is t=
he goal. =0A=A0=0A=A0=0ARegards, Dave =0A=A0=0A=A0=0A=A0=0A=A0=0A----- Orig=
inal Message ----- =0A=0A  From: =0A  meredith lamb =0A  To: psn-l@webtroni=
cs.com =0A  Sent: Sunday, August 16, 2009 00:18=0A  Subject: Re: Real time =
traces=0A =20
=0A  Hi Dave,=0A  =A0=0A  Thanks for the info.=A0 Was wondering about the m=
ain spring =0A  width...its hard to judge from the photo; and where you got=
 such=0A  and the ~ cost?=A0 The photo spring looks to be a original coil s=
trip =0A  or a good home shear.=A0 I understand (via the web) its=0A  magne=
tic; but apparently it works fine regardless of the boom end =0A  coil/magn=
et actuator feedback influence.=A0=0A  =A0=0A  Midway atop your vertical me=
chanism there appears to be a screw =0A  adjustable mass balance or centeri=
ng=A0counterweight.=0A  =A0=0A  I presume....that the main spring period is=
 adjusted via the back clamp =0A  alone.=A0 =0A  =A0=0A  The very small siz=
e=A0of the vertical is rather=A0startling for the =0A  ~ giant ~ mechanisms=
 we're used too seeing on PSN.=0A  I can't really tell if their is more add=
ed mass to the boom via =0A  the=A0photo's besides the ~ frame, coil,=A0cap=
acitance plate.=0A  =A0=0A  What did you use for the coil?=A0 Homebrew woun=
d or otherwise a =0A  commerical coil?=0A  =A0=0A  What is the magnet, ring=
 ceramic or neodymium?=0A  =A0=0A  Take care, Meredith Lamb=0A  =A0=0A  =A0=
=0A  On Fri, Aug 14, 2009 at 12:12 PM, Dave Nelson  wr=
ote:
=0A  =0A    =0A    Hi Meredith,=0A    =A0=0A    The spring is 17-7=A0 stain=
less condition C =0A    heat treated to condition CH900. Thickness is 12 mi=
ls. =A0The pivots are =0A    2 mil stainless single axis=A0.=A0 Pivot lengt=
h is only about 12 mils. =0A    They are held=A0 tension by the=A0C spring.=
 A two axis pivot is not =0A    necessary.=0A    =A0=0A    =A0=0A    Dave =
Dave
I'm interested in finding out more an= d impressed also. I reduced the size of the STM style vertical 12" but like= your design. Didn't you try a hacksaw blade(s)  before? I don't remem= ber the thickness but would the taping blade material STM mentioned work? I= 'm not sure about my heat treating abilities (proper annealing etc). I have= read Bretts excellent documentation in the past.
Regards
Barry

--- On Sat, 8/15/09, Dave Nelson <davefnelson@.......> wrote:

From: Dave Nelson <davefnel= son@.......>
Subject: Re: Real time traces
To: psn-l@.............. m
Date: Saturday, August 15, 2009, 6:43 PM

=0A=0A =0A =0A=0A
Hi M= eredith.
=0A
 <= /div>=0A
The spring is cut to width on = my personal shear and =0Aheat treated in the home oven in the automatic cle= aning mode.  The heat =0Atreat significantly increases the yield stren= gth. The temperature is just right =0Aas measured with a thermocouple. The = width for the instrument pictured is 16 mm =0Aand thickness is 12 mils.&nbs= p; (Sorry for the mixed units -- our European =0Afriends will think we can'= t  make up our minds ) 
=0A
 
=0A
 = ;I have a large quantity of the raw material =0Afor the springs -- enough f= or any conceivable quantity of instruments. I am =0Aworking on the  re= peatability in the shearing process. Right now I can do =0A+- ~.15mm.
=0A
 
=0A
<= font size=3D"2" face=3D"Arial">As you suggest the period is  a functio= n of =0Athe spring length and adjusted at the clamp. It sometimes takes a f= ew tries but =0Athe process is quite easy.  The period and rough cente= ring are done with =0Athe  center capacitor plate PC board  remov= ed to allow for a motion =0Aover large angle for convenience. The final mas= s centering is done by adjusting =0Athe moveable mass  either by eye o= r using the LED's on the electronics =0Aboard with the loop open. The integ= rator is designed to hold center over a wide =0Atemperature range so reente= ring is probably not necessary under all but the most =0Asevere climatic te= mperature changes. We estimate +- 30C  but that is not =0Afully confir= med.
=0A
 =0A
 
=0A
Actuator is homebrew based in a Neodymium magnet = =0Apurchased on Ebay. The coil is wound on a modified PAC plumbing part&nbs= p; (1 =0A1/4 Schedule 40 plug from Lowes).  It takes a few minute= s of lathe =0Awork to make it . The coil is 770 turns of # 32 for= about 50 ohms and =0A15 N/A. I fabricate the magnet assembly also but it d= oes take some minor  =0AMIG tack welds. The materials are available&nb= sp; from Online Metals. =0A
=0A
 
=0A
There= is another small mass at he coil attach point =0Aof ~ 10 grams. =
=0A
 
= =0A
The overall size of the basic mecha= nism exclusive =0Aof the case is 4.5 x 9.5 inches. I have a new (untried) d= esign which will be 4.5 =0Ax 5 inches in a somewhat different configuratio= n which may allow for  =0Abuoyancy compensation.  The new de= sign is also easier to build or at least =0Athat is the goal.
= =0A
 
=0A
 
=0A
Regards, Dave
=0A
=  
=0A
 =0A
 
=0A
 
=0A
----- Original Messag= e -----
=0A
=0A
From: =0A meredith lamb =
=0A =0A
Sent: Sunday, August 16, 2009 00:18
=0A =
Subject: Re: R= eal time traces
=0A

=0A
Hi Dave,
=0A
=  
=0A
Thanks for the info.  Was wondering about the ma= in spring =0A width...its hard to judge from the photo; and where you got = such
=0A
and the ~ cost?  The photo spring looks to be a or= iginal coil strip =0A or a good home shear.  I understand (via the we= b) its
=0A
magnetic; but apparently it works fine regardless of = the boom end =0A coil/magnet actuator feedback influence. 
=0A =
 
=0A
Midway atop your vertical mechanism there appear= s to be a screw =0A adjustable mass balance or centering counterweigh= t.
=0A
 
=0A
I presume....that the main spring p= eriod is adjusted via the back clamp =0A alone. 
=0A
&nbs= p;
=0A
The very small size of the vertical is rather s= tartling for the =0A ~ giant ~ mechanisms we're used too seeing on PSN.=0A
I can't really tell if their is more added mass to the boom vi= a =0A the photo's besides the ~ frame, coil, capacitance plate.<= /div>=0A
 
=0A
What did you use for the coil?  H= omebrew wound or otherwise a =0A commerical coil?
=0A
 =0A
What is the magnet, ring ceramic or neodymium?
=0A
=  
=0A
Take care, Meredith Lamb
=0A
 
= =0A
 
=0A
On Fri, Aug 14, 2009 = at 12:12 PM, Dave Nelson <davefnelson@.......> wrote:
=0A =0A
=0A Hi Meredith,
=0A
 
=0A
The spring is 17-7  stainless condition C =0A heat= treated to condition CH900. Thickness is 12 mils.  The pivots are =0A= 2 mil stainless single axis .  Pivot length is only about 12 = mils. =0A They are held  tension by the C spring. A two axis p= ivot is not =0A necessary.
=0A
 
=0A
 
=0A
Dave
=0A
 
=0A
 <= /div>=0A
=0A
 
<=
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