Toshiba TV29C90 problem; Image fades to black...

On Mar 21, 1:07�am, "Bob F" <bobnos...@gmail.com> wrote:
"Donna Ohl" <donna....@sbcglobal.net> wrote in message news:4FhDj.65364
- How to unclog the bathtub where I can't figure out WHERE the filter is!
http://www.flickr.com/photos/donnaohl/2279157295/

Ther's probably a passage in the valve plugged. Shut off all water to the
shower, and disassemble the valve, them flush it out by briefly turning the
water back on, with appropriate precautions.
Click to expand...
if you try this dont use the main houses valve, i did once it wouldnt
shut off and flooded the basement by the time the water company got
things turned off.......
 
"Esther & Fester Bestertester" <not@me.really> wrote in message
news:0001HW.C408B6B10029D013B01AD9AF@news.sf.sbcglobal.net...
If you have been letting it cure at room temperature, try about 15
minutes
at 160 F or so. It will get a lot harder.

Tam

Does it matter when the heat is applied? Right away? Or after it seems to
have cured as much as it is going to at room temp?

I have been waiting a few minutes until the epoxy is no longer runny. I turn
Click to expand...
the oven on to 200, but turn it off before it reaches temperature. Have also
used a heat gun on something that was part of a large stationary object
(toilet). I haven't bothered, but this information should be available from
the manufacturer.

Tam
 
On Mar 20, 1:09 pm, Esther & Fester Bestertester <n...@me.really>
wrote:
See no n.g. for adhesives & epoxies, so if there's a better forum for this,
just point me to it.

I need an epoxy that is strong to the point of brittle. I want no flex; it
has to transmit vibration as close to 100% as possible.

Am I looking for a high Shore Hardness value? That's what Devcon uses in its
data sheets to specify hardness.

Is this something that I can achieve by changing the mix of the 2 parts? If
so, what do I lose if I use more hardener?

Any personal experiences with epoxies that you found to be harder than
others?

Thanks.
FBt
Click to expand...
Rubinno cement made by Singer Kearfott in the 70's was used on
guidance systems for the Sram missile, PC3, and A7 navey fighter
jets. It is the best there is.
 
On Fri, 21 Mar 2008 18:36:53 GMT, Esther & Fester Bestertester
<not@me.really> wrote:

Rubinno cement

Google turns up zero hits. Is the correct spelling? Any web references you
can give?

Thanks,
FBt
Click to expand...

It is probably $50 a quart. Minimum.
 
On Sat, 22 Mar 2008 03:54:02 GMT, Esther & Fester Bestertester
<not@me.really> wrote:

It is probably $50 a quart. Minimum.

But that doesn't help me know *where*.

FBt
Click to expand...

Try this one:

EPOTEK

http://www.epotek.com/categories.asp?ID=1

There are several that would easily fit your needs, and some that are
sold at small qty tube level.
 
Esther & Fester Bestertester wrote:
See no n.g. for adhesives & epoxies, so if there's a better forum for this,
just point me to it.

I need an epoxy that is strong to the point of brittle. I want no flex; it
has to transmit vibration as close to 100% as possible.

Am I looking for a high Shore Hardness value? That's what Devcon uses in its
data sheets to specify hardness.
Click to expand...
I believe that (Shore) is a measure of resistance to indentation. In
other words, pressure. You might need something else, depending on which
direction the vibration is acting with respect to the surface. A
pressure wave will result in both pressure and tensile stresses on the
adhesive. A shear wave will result in (duh) shear stresses.

In addition, you need to define what you mean by 'transmit vibration'.
I'm not a mechanical guy, but I'd be willing to bet that the problem of
maximizing mechanical energy transmission is analogous to that of
maximizing electromagnetic energy transmission. That is: It is optimal
when the impedance (modulus of elasticity?) is closely matched and
energy reflection is minimized.

The strength of the adhesive only becomes important if the amplitude of
the vibration approaches the strength limit of the bond.

This appears to be the sort of problems that people designing sonar
transducers have to deal with.

--
Paul Hovnanian mailto:paul@Hovnanian.com
------------------------------------------------------------------
What if no one ever asked a hypothetical question?
 
Gerald Newton wrote:
On Mar 20, 1:09 pm, Esther & Fester Bestertester <n...@me.really
wrote:
See no n.g. for adhesives & epoxies, so if there's a better forum for this,
just point me to it.

I need an epoxy that is strong to the point of brittle. I want no flex; it
has to transmit vibration as close to 100% as possible.

Am I looking for a high Shore Hardness value? That's what Devcon uses in its
data sheets to specify hardness.

Is this something that I can achieve by changing the mix of the 2 parts? If
so, what do I lose if I use more hardener?

Any personal experiences with epoxies that you found to be harder than
others?

Thanks.
FBt

Rubinno cement made by Singer Kearfott in the 70's was used on
guidance systems for the Sram missile, PC3, and A7 navey fighter
jets. It is the best there is.
Click to expand...
What exactly was it used for? For securing components in a high
vibration environment, that might damp the vibrations that the OP wants
to transmit.

--
Paul Hovnanian mailto:paul@Hovnanian.com
------------------------------------------------------------------
During the next two hours, the system will be going up and down several
times, often with lin~po_~{po ~poz~ppo\~{ o n~po_~{o[po ~y oodsou>#w4ko
 
Paul Hovnanian P.E. wrote:
The strength of the adhesive only becomes important if
the amplitude of the vibration approaches the strength limit of the bond.

This appears to be the sort of problems
that people designing sonar transducers have to deal with.
Click to expand...
I saw something on Blue Whales the other day
that mentioned they are the loudest creature.
I looked it up and the figure is 188dB (like being next to a rocket)
....and there is great controversy about SONAR use
because it is thought (due to weird behavior
like healthy-appearing specimens beaching themselves)
that it is so loud that it damages the hearing of whales.
 
Look on the web for, Aluma Lead.I used to use Aluma Lead for doing auto
body repair work.Also, J B Weld might work for you. www.jbweld.com
cuhulin
 
"Paul Hovnanian P.E." <paul@hovnanian.com> wrote in message
news:47E49147.3898C236@hovnanian.com...
Esther & Fester Bestertester wrote:

See no n.g. for adhesives & epoxies, so if there's a better forum for
this,
just point me to it.

I need an epoxy that is strong to the point of brittle. I want no flex;
it
has to transmit vibration as close to 100% as possible.

Am I looking for a high Shore Hardness value? That's what Devcon uses in
its
data sheets to specify hardness.

I believe that (Shore) is a measure of resistance to indentation. In
other words, pressure. You might need something else, depending on which
direction the vibration is acting with respect to the surface. A
pressure wave will result in both pressure and tensile stresses on the
adhesive. A shear wave will result in (duh) shear stresses.

In addition, you need to define what you mean by 'transmit vibration'.
I'm not a mechanical guy, but I'd be willing to bet that the problem of
maximizing mechanical energy transmission is analogous to that of
maximizing electromagnetic energy transmission. That is: It is optimal
when the impedance (modulus of elasticity?) is closely matched and
energy reflection is minimized.

The strength of the adhesive only becomes important if the amplitude of
the vibration approaches the strength limit of the bond.

This appears to be the sort of problems that people designing sonar
transducers have to deal with.
Click to expand...
Well, we used an epoxy (simple two part) to 'glue' mounts for vibration
monitoring equipment. The accelerator was in a magnetic housing and we
epoxied steel rings (not much more than washers really) to rotating
equipment at key points of bearings etc...). The mounts/washers provided a
nice flat, properly oriented surface for the vibration pickup so we could do
'sound cuts'.

Two fold, 1) we wanted to know how much noise our equipment was making
(submarines live / die by sound levels transmitted into the water) and 2) we
could predict some equipment maintenance like simple balance, pump-motor
alignment, bearing problems.

Maybe that's what the OP is after. But as I said, we used a simple, two
part epoxy with quite good results.

daestrom
 
daestrom wrote:
"Paul Hovnanian P.E." <paul@hovnanian.com> wrote in message
news:47E49147.3898C236@hovnanian.com...
Esther & Fester Bestertester wrote:

See no n.g. for adhesives & epoxies, so if there's a better forum for
this,
just point me to it.

I need an epoxy that is strong to the point of brittle. I want no flex;
it
has to transmit vibration as close to 100% as possible.

Am I looking for a high Shore Hardness value? That's what Devcon uses in
its
data sheets to specify hardness.

I believe that (Shore) is a measure of resistance to indentation. In
other words, pressure. You might need something else, depending on which
direction the vibration is acting with respect to the surface. A
pressure wave will result in both pressure and tensile stresses on the
adhesive. A shear wave will result in (duh) shear stresses.

In addition, you need to define what you mean by 'transmit vibration'.
I'm not a mechanical guy, but I'd be willing to bet that the problem of
maximizing mechanical energy transmission is analogous to that of
maximizing electromagnetic energy transmission. That is: It is optimal
when the impedance (modulus of elasticity?) is closely matched and
energy reflection is minimized.

The strength of the adhesive only becomes important if the amplitude of
the vibration approaches the strength limit of the bond.

This appears to be the sort of problems that people designing sonar
transducers have to deal with.


Well, we used an epoxy (simple two part) to 'glue' mounts for vibration
monitoring equipment. The accelerator was in a magnetic housing and we
epoxied steel rings (not much more than washers really) to rotating
equipment at key points of bearings etc...). The mounts/washers provided a
nice flat, properly oriented surface for the vibration pickup so we could do
'sound cuts'.

Two fold, 1) we wanted to know how much noise our equipment was making
(submarines live / die by sound levels transmitted into the water) and 2) we
could predict some equipment maintenance like simple balance, pump-motor
alignment, bearing problems.

Maybe that's what the OP is after. But as I said, we used a simple, two
part epoxy with quite good results.
Click to expand...
The selection of a suitable adhesive depends on how much energy one can
afford to lose in a sub-optimally coupled system. In your case, the
signal level of vibrating mechanical equipment is probably high enough
that some attenuation is tolerable.

The other thing to consider is the mass of the sensor, the flexibility
of the adhesive and the resulting natural frequency of the sensor
assembly. A massive sensor and/or flexible coupling will result in a
lower frequency and result in attenuation of signals above that point.

daestrom
Click to expand...
--
Paul Hovnanian mailto:paul@Hovnanian.com
------------------------------------------------------------------
You can discover what your enemy fears most by observing the
means he uses to frighten you. -- Eric Hoffer
 
On Sat, 22 Mar 2008 20:12:13 -0800, "Paul Hovnanian P.E."
<paul@hovnanian.com> wrote:

daestrom wrote:

"Paul Hovnanian P.E." <paul@hovnanian.com> wrote in message
news:47E49147.3898C236@hovnanian.com...
Esther & Fester Bestertester wrote:

See no n.g. for adhesives & epoxies, so if there's a better forum for
this,
just point me to it.

I need an epoxy that is strong to the point of brittle. I want no flex;
it
has to transmit vibration as close to 100% as possible.

Am I looking for a high Shore Hardness value? That's what Devcon uses in
its
data sheets to specify hardness.

I believe that (Shore) is a measure of resistance to indentation. In
other words, pressure. You might need something else, depending on which
direction the vibration is acting with respect to the surface. A
pressure wave will result in both pressure and tensile stresses on the
adhesive. A shear wave will result in (duh) shear stresses.

In addition, you need to define what you mean by 'transmit vibration'.
I'm not a mechanical guy, but I'd be willing to bet that the problem of
maximizing mechanical energy transmission is analogous to that of
maximizing electromagnetic energy transmission. That is: It is optimal
when the impedance (modulus of elasticity?) is closely matched and
energy reflection is minimized.

The strength of the adhesive only becomes important if the amplitude of
the vibration approaches the strength limit of the bond.

This appears to be the sort of problems that people designing sonar
transducers have to deal with.


Well, we used an epoxy (simple two part) to 'glue' mounts for vibration
monitoring equipment. The accelerator was in a magnetic housing and we
epoxied steel rings (not much more than washers really) to rotating
equipment at key points of bearings etc...). The mounts/washers provided a
nice flat, properly oriented surface for the vibration pickup so we could do
'sound cuts'.

Two fold, 1) we wanted to know how much noise our equipment was making
(submarines live / die by sound levels transmitted into the water) and 2) we
could predict some equipment maintenance like simple balance, pump-motor
alignment, bearing problems.

Maybe that's what the OP is after. But as I said, we used a simple, two
part epoxy with quite good results.

The selection of a suitable adhesive depends on how much energy one can
afford to lose in a sub-optimally coupled system. In your case, the
signal level of vibrating mechanical equipment is probably high enough
that some attenuation is tolerable.

The other thing to consider is the mass of the sensor, the flexibility
of the adhesive and the resulting natural frequency of the sensor
assembly. A massive sensor and/or flexible coupling will result in a
lower frequency and result in attenuation of signals above that point.

daestrom
Click to expand...

Metal filled epoxies pass thermal as well as vibration quite well.

http://www.epotek.com/SSCDocs/datasheets/H20E.PDF
 
The other thing to consider is the mass of the sensor, the flexibility
of the adhesive and the resulting natural frequency of the sensor
assembly. A massive sensor and/or flexible coupling will result in a
lower frequency and result in attenuation of signals above that point.
Click to expand...
The "flexible coupling" provided by the epoxies I've tried is causing issues.


It's been suggested that I try silver-filled epoxy and potting compound.
Dental cement was also a suggestion. I'm looking at all of these.

FBt
 
On Sat, 22 Mar 2008 22:49:16 -0700, Esther & Fester Bestertester
<not@me.really> wrote:

The other thing to consider is the mass of the sensor, the flexibility
of the adhesive and the resulting natural frequency of the sensor
assembly. A massive sensor and/or flexible coupling will result in a
lower frequency and result in attenuation of signals above that point.

The "flexible coupling" provided by the epoxies I've tried is causing issues.


It's been suggested that I try silver-filled epoxy and potting compound.
Dental cement was also a suggestion. I'm looking at all of these.

FBt
Click to expand...

The silver filled is used to attach IC chip dies to their heat sinks
inside the chip package.

It is quite firm... brittle even, and is also conductive.

Requires 4 hr 80 C cure, however.

There are cooler, longer schedules.
 
hand held hair dryers work fine

let epxy cure to near solid, then heat

else it will reliquify and run with gravity, messy!!

my work once required magnets to be epoxied to core pieces in meter
movements, they went thru ovens after primary cure for abt 15 minutes at 200
deg F

that was before engneering started using cryanoacrylite type adhesives, they
seemed much better and harder with less work time, never had a release
either.

preparation is key to good results

cryo is avail in gel or near gooy form

Loctite corporation has tons of alternatives available


"Tam" <t-tammaru@comcast.net> wrote in message
news:5eednSppS42jR37anZ2dnUVZ_oSunZ2d@comcast.com...
"Esther & Fester Bestertester" <not@me.really> wrote in message
news:0001HW.C408B6B10029D013B01AD9AF@news.sf.sbcglobal.net...
If you have been letting it cure at room temperature, try about 15
minutes
at 160 F or so. It will get a lot harder.

Tam

Does it matter when the heat is applied? Right away? Or after it seems
to
have cured as much as it is going to at room temp?

I have been waiting a few minutes until the epoxy is no longer runny. I
turn
the oven on to 200, but turn it off before it reaches temperature. Have
also
used a heat gun on something that was part of a large stationary object
(toilet). I haven't bothered, but this information should be available
from
the manufacturer.

Tam
Click to expand...
 
On Sun, 23 Mar 2008 20:15:46 GMT, "HapticZ" <hapticz@sbcglobal.net>
wrote:

else it will reliquify and run with gravity, messy!!
Click to expand...

Wrong. There are plenty of epoxies that stay right where they are put.

Not only that, but capillary attraction will hold most in place.

Also, the extremely high temp a hair dryer or heat gun puts out is too
much. It needs to be in an oven at a known temperature to cure correctly.
 
CA has high "pulling" strength, but is easily cracked by lateral forces.
 
On Sun, 23 Mar 2008 18:33:00 -0700, Esther & Fester Bestertester
<not@me.really> wrote:

How does CA (cyanoacrylate) stack up against epoxy?
Click to expand...

Poor thermal, poor vibration. Not epoxy.
 
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