Homebrew PCBs

I have made some boards using the toner transfer method with fairly
good results. Something closely related is the matter of getting
cables connected to a printed circuit board. I would very much like to
hear of good ways to build nice cables and connectors that are "clean"
and approach the looks and durability of commecial cables.

I work with amateur (ham) radio and many of the new radios use RJ45
plugs for the microphone. I do have a good crimp tool for RJ45 use and
make my own cables for home networking. I have constructed a couple
cables to connect to such radios, ending up with a short stub of cat 5
wire coming from the RJ45 plug then converting to some shielded wire
for audio and flexible cable for the other signals. I end up with
something that works, but is nowhere near as nice as the commercial
cable.

I suspect that there must be some injecting molding machine (at a cost
of a few million, no doubt) that creates all these nice cables that
come with commercial equipment. My current solder and heat-shrink
methods don't approach the quality of my PC boards and seem the "weak
link" in the homwbrew process.

What solutions have others found for nice cables & connectors?

Can you find PCB mount connectors for all the connector types you use?
 If so make a little PCB with the two or more connector types on it
and the correct wiring in between.  Fisrt, though, find a box that
will fit the board and connectors, nibble out holes and you've got a
professional looking adaptor.  Basically, an adaptor box.  Easy as
pie.  Or for stationary equipment, you can build a connector panel. 
Lots of options.

Of course, there is no substitute for having the right connector on
the main PCB in the first place.

 --- In Homebrew_PCBs@yahoogroups.com, "Dale Mosby" <dale@a...> wrote:

> 
> I have made some boards using the toner transfer method with fairly
> good results. Something closely related is the matter of getting
> cables connected to a printed circuit board. I would very much like to
> hear of good ways to build nice cables and connectors that are "clean"
> and approach the looks and durability of commecial cables.
> 
> I work with amateur (ham) radio and many of the new radios use RJ45
> plugs for the microphone. I do have a good crimp tool for RJ45 use and
> make my own cables for home networking. I have constructed a couple
> cables to connect to such radios, ending up with a short stub of cat 5
> wire coming from the RJ45 plug then converting to some shielded wire
> for audio and flexible cable for the other signals. I end up with
> something that works, but is nowhere near as nice as the commercial
> cable.
> 
> I suspect that there must be some injecting molding machine (at a cost
> of a few million, no doubt) that creates all these nice cables that
> come with commercial equipment. My current solder and heat-shrink
> methods don't approach the quality of my PC boards and seem the "weak
> link" in the homwbrew process.
> 
> What solutions have others found for nice cables & connectors?

I think you missed the OP's point.

He's asking "how to make commercial quality cables". 

 - jim

On Wed, 19 Jan 2005 17:59:25 -0000
"Phil" <phil1960us@...> wrote:

> 
> Can you find PCB mount connectors for all the connector types you use?
> If so make a little PCB with the two or more connector types on it
> and the correct wiring in between.  Fisrt, though, find a box that
> will fit the board and connectors, nibble out holes and you've got a
> professional looking adaptor.  Basically, an adaptor box.  Easy as
> pie.  Or for stationary equipment, you can build a connector panel.
> Lots of options.
> 
> Of course, there is no substitute for having the right connector on
> the main PCB in the first place.
> 
> --- In Homebrew_PCBs@yahoogroups.com, "Dale Mosby" <dale@a...> wrote:
> >
> > I have made some boards using the toner transfer method with fairly
> > good results. Something closely related is the matter of getting
> > cables connected to a printed circuit board. I would very much like to
> > hear of good ways to build nice cables and connectors that are "clean"
> > and approach the looks and durability of commecial cables.
> >
> > I work with amateur (ham) radio and many of the new radios use RJ45
> > plugs for the microphone. I do have a good crimp tool for RJ45 use and
> > make my own cables for home networking. I have constructed a couple
> > cables to connect to such radios, ending up with a short stub of cat 5
> > wire coming from the RJ45 plug then converting to some shielded wire
> > for audio and flexible cable for the other signals. I end up with
> > something that works, but is nowhere near as nice as the commercial
> > cable.
> >
> > I suspect that there must be some injecting molding machine (at a cost
> > of a few million, no doubt) that creates all these nice cables that
> > come with commercial equipment. My current solder and heat-shrink
> > methods don't approach the quality of my PC boards and seem the "weak
> > link" in the homwbrew process.
> >
> > What solutions have others found for nice cables & connectors?
> 
> 
> 
> 
> 
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
> 
> 
> ------------------------------------------------
> Yahoo! Groups Links
> To visit your group on the web, go to:
> http://groups.yahoo.com/group/Homebrew_PCBs/
>  
> To unsubscribe from this group, send an email to:
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>  
> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

----- Original Message ----- 

From: "Dale Mosby" <dale@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, January 19, 2005 5:05 PM
Subject: [Homebrew_PCBs] Cables and connectors


>
>
> I have made some boards using the toner transfer method with fairly
> good results. Something closely related is the matter of getting
> cables connected to a printed circuit board. I would very much like to
> hear of good ways to build nice cables and connectors that are "clean"
> and approach the looks and durability of commecial cables.
>
> I work with amateur (ham) radio and many of the new radios use RJ45
> plugs for the microphone. I do have a good crimp tool for RJ45 use and
> make my own cables for home networking. I have constructed a couple
> cables to connect to such radios, ending up with a short stub of cat 5
> wire coming from the RJ45 plug then converting to some shielded wire
> for audio and flexible cable for the other signals. I end up with
> something that works, but is nowhere near as nice as the commercial
> cable.
>
> I suspect that there must be some injecting molding machine (at a cost
> of a few million, no doubt) that creates all these nice cables that
> come with commercial equipment. My current solder and heat-shrink
> methods don't approach the quality of my PC boards and seem the "weak
> link" in the homwbrew process.
>
> What solutions have others found for nice cables & connectors?

I use Molex KK connectors, which are widely available. Suitable tools for 
crimping the terminals aren't expensive.

Leon 



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No virus found in this outgoing message.
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> I have made some boards using the toner transfer
> method with fairly
> good results. Something closely related is the
> matter of getting
> cables connected to a printed circuit board. I would
> very much like to
> hear of good ways to build nice cables and
> connectors that are "clean"
> and approach the looks and durability of commecial
> cables.
> 
> I work with amateur (ham) radio and many of the new
> radios use RJ45
> plugs for the microphone. I do have a good crimp
> tool for RJ45 use and
> make my own cables for home networking. I have
> constructed a couple
> cables to connect to such radios, ending up with a
> short stub of cat 5
> wire coming from the RJ45 plug then converting to
> some shielded wire
> for audio and flexible cable for the other signals.
> I end up with
> something that works, but is nowhere near as nice as
> the commercial
> cable.
> 
> I suspect that there must be some injecting molding
> machine (at a cost
> of a few million, no doubt) that creates all these
> nice cables that
> come with commercial equipment. My current solder
> and heat-shrink
> methods don't approach the quality of my PC boards
> and seem the "weak
> link" in the homwbrew process.
Vertical insert molding machines and molds are
actually not that spendy. $100K for a used machine,
and a mold would set you up real well, up to a few
hundred thousand/year.

Book molds are yet another way to go, figure on under
$10K tooling. But the piece part cost is higher, and
you are limited to the upper ten thousands/year. A
friend had his molds made for $3K, but its a really
simple connector.

As far as DIY, its time consuming.... but cheap

1. create a nice looking master (wood, clay, or wax)
2. create a silicon rubber mold from the master
3. create a clamping arrangement to hold the silicon
rubber mold onto the cable and connector
4. cast the connector/cable assmebly

Your biggest expense will be a vacuum system to degas
the casting material. If you don't mind a few bubbles
here and there, some materials are more forgiving and
work find without degassing. Silicon rubber molds are
good for 5 pieces if you are not careful, and you
might even be able to make 30 or 40 if you are
careful.

If you need more than 30 or 40, it pay be cost
effective to have a casting mold machined from
aluminum. I've got thousands of products in the field,
some of which were medical using aluminum casting
molds for the connectors. However for prototypes and
proof of concept, the silicon rubber works fine. Much
of the time, we installed small circuit boards right
within the connector assembly (the first few of course
were home brew).

Do not however try to use hardware store silicon. Its
not for casting, and does not work very well.

Ron

__________________________________________________
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Ron,

thanks for providing this... but can you provide a bit more info?

Any "name brand" silicon I should buy?

I have a vacuum pump... but I cannot figure out how I would attach it to a rubber mold.. would that just collapse the mold?

Do you have any pictures?

 - jim


On Thu, 20 Jan 2005 01:06:56 -0800 (PST)
ron amundson <mnphysicist@...> wrote:

> 
> As far as DIY, its time consuming.... but cheap
> 
> 1. create a nice looking master (wood, clay, or wax)
> 2. create a silicon rubber mold from the master
> 3. create a clamping arrangement to hold the silicon
> rubber mold onto the cable and connector
> 4. cast the connector/cable assmebly
> 
> Your biggest expense will be a vacuum system to degas
> the casting material. If you don't mind a few bubbles
> here and there, some materials are more forgiving and
> work find without degassing. Silicon rubber molds are
> good for 5 pieces if you are not careful, and you
> might even be able to make 30 or 40 if you are
> careful.
> 
> If you need more than 30 or 40, it pay be cost
> effective to have a casting mold machined from
> aluminum. I've got thousands of products in the field,
> some of which were medical using aluminum casting
> molds for the connectors. However for prototypes and
> proof of concept, the silicon rubber works fine. Much
> of the time, we installed small circuit boards right
> within the connector assembly (the first few of course
> were home brew).
> 
> Do not however try to use hardware store silicon. Its
> not for casting, and does not work very well.
> 
> Ron
> 
> __________________________________________________
> Do You Yahoo!?
> Tired of spam?  Yahoo! Mail has the best spam protection around
> http://mail.yahoo.com
> 
> 
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
> 
> 
> ------------------------------------------------
> Yahoo! Groups Links
> To visit your group on the web, go to:
> http://groups.yahoo.com/group/Homebrew_PCBs/
>  
> To unsubscribe from this group, send an email to:
> Homebrew_PCBs-unsubscribe@yahoogroups.com
>  
> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

On Thu, 20 Jan 2005 10:55:18 -0800, James Washer <washer@...> wrote:

>
> Ron,
> thanks for providing this... but can you provide a bit more info?
> Any "name brand" silicon I should buy?
> I have a vacuum pump... but I cannot figure out how I would attach it to  
> a rubber mold.. would that just collapse the
> mold?
> Do you have any pictures?
> - jim


you don't vacuum the mold, you need a small vacuum chamber in which you  
put the container of silicone or whatever you want to use to cast. the  
vacuum makes the bubbles HUGH and causes them to rise to the surface,  
effectively de-gassing the liquid. then you take the liquid out and cast  
with it.
Of course you can also vacuum the un-cured mold and pattern just after  
casting if it fits into the chamber.

You can join <http://groups.yahoo.com/group/casting/> for more information.
I was looking into it a short while back, but decided it is too expensive  
and i have enough stuff to do right now. But it opens a lot of  
possibilities...

ST

Ron - Thanks for the pointer to casting group. I joined that, see a 
huge number of posted messages and I will look through some of those 
for information.

I was defnitely looking for something quite inexpensive - on the 
order of my investment in toner transfer PBC process. I would not 
mind the expense of a vacuum chamber to remove bubbles from rubber.

I have heard the warnings against using hardware store 
Silicon "calking" for electrical wire potting.  I have tried potting 
connectors using some automotive gasket compound. While that had a 
nice "rubber" feel to it, it did not seem to really "glue" itself to 
the wires well. I have dripped some 5 min epoxy into things like the 
RJ45 plugs to help anchor wires. That seems useful in limited 
situations.

Any pointers to what to ask for as a molding compound that would dry 
reasonably hard are stick well to insulated wires. Is "silicon 
rubber" a well known description when looking for this material?

If we stray too far from PCBs or the discussion gets too long I'm 
happy to take this away from the newsgroup. But making high quality 
cables seems pretty closly related to making boards, as most of my 
electrical projects have cables/connectors with them.

Thanks for the data so far. - dale

On Thu, 20 Jan 2005 20:09:18 -0000, Dale Mosby <dale@...> wrote:

>
> I was defnitely looking for something quite inexpensive - on the
> order of my investment in toner transfer PBC process. I would not
> mind the expense of a vacuum chamber to remove bubbles from rubber.
> I have heard the warnings against using hardware store
> Silicon "calking" for electrical wire potting.  I have tried potting
> connectors using some automotive gasket compound. While that had a
> nice "rubber" feel to it, it did not seem to really "glue" itself to
> the wires well. I have dripped some 5 min epoxy into things like the
> RJ45 plugs to help anchor wires. That seems useful in limited
> situations.

The hardware shop stuff doesn't lend itself to casting i fear. On another  
note, never try to use acrylic sealant. i didn't have anything else at  
hand and tried to isolate a 240V connection on a relais with it. I didn't  
wait for it to cure and switched on, it does conduct electricity quite  
well. Not sure if the cured stuff does too.

> Any pointers to what to ask for as a molding compound that would dry
> reasonably hard are stick well to insulated wires. Is "silicon
> rubber" a well known description when looking for this material?
> If we stray too far from PCBs or the discussion gets too long I'm
> happy to take this away from the newsgroup. But making high quality
> cables seems pretty closly related to making boards, as most of my
> electrical projects have cables/connectors with them.
> Thanks for the data so far. - dale

I'm not sure if silicone can be used for the plug housing too, it seems to  
me it is meant for making the mold only. it does not stick to anything but  
silicone (good for releasing the pattern from the mold).
But there are various flexible and inflexible casting materials you can  
try.
As i have no experience with it i suggest you ask in the casting group.


ST

The big problem with the hardware store silicone (and this 
goes for the industrial grades too) is that the inexpensive 
ones  release acetic acid in the curing process.  This 
attacks copper - wires, circuit boards, etc.  Find a 
silicone that doesn't have a vinegar smell to it as it cures.

Norm
Stefan Trethan wrote:
> On Thu, 20 Jan 2005 20:09:18 -0000, Dale Mosby <dale@...> wrote:
> 
> 
>>I was defnitely looking for something quite inexpensive - on the
>>order of my investment in toner transfer PBC process. I would not
>>mind the expense of a vacuum chamber to remove bubbles from rubber.
>>I have heard the warnings against using hardware store
>>Silicon "calking" for electrical wire potting.  I have tried potting
>>connectors using some automotive gasket compound. While that had a


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Version: 7.0.300 / Virus Database: 265.6.13 - Release Date: 1/16/2005

--- In Homebrew_PCBs@yahoogroups.com, James Washer <washer@t...> wrote:
> 
> Ron,
> 
> thanks for providing this... but can you provide a bit more info?
> 
> Any "name brand" silicon I should buy?
> 
> I have a vacuum pump... but I cannot figure out how I would attach
it to a rubber mold.. would that just collapse the mold?
> 
> Do you have any pictures?

You can learn more at the NW Propmasters Yahoogroup, take a look in
the Links there. I'm listowner of that group, too.

http://groups.yahoo.com/nwpropmasters

You don't vacuum it while it is in the mold; you put the resin under
vacuum to pull the air out, then pour it into the mold.

I buy most of my silicone and plastic casting from Smooth-On.

Steve Greenfield

--- In Homebrew_PCBs@yahoogroups.com, Norman Stewart
<normstewart@a...> wrote:
> 
> The big problem with the hardware store silicone (and this 
> goes for the industrial grades too) is that the inexpensive 
> ones  release acetic acid in the curing process.  This 
> attacks copper - wires, circuit boards, etc.  Find a 
> silicone that doesn't have a vinegar smell to it as it cures.

Or use polyurethane rubber. You can get it in many different grades of
flexibility, from hard as a rock to so soft it is sticky. I think
those sticky lint rollers are made from a grade of polyurethane rubber.

Steve Greenfield

Dale Mosby wrote:
> 
> I was defnitely looking for something quite inexpensive - on the 
> order of my investment in toner transfer PBC process. I would not 
> mind the expense of a vacuum chamber to remove bubbles from rubber.


   If you do this part, get a Foodsaver.  Good for food and pulls an ok vacuum
in one of the cannisters.


> Any pointers to what to ask for as a molding compound that would dry 
> reasonably hard are stick well to insulated wires. Is "silicon 
> rubber" a well known description when looking for this material?
> 

   Try putting a loop or Z bend into the wire, and embedding it into expoxy or 
other compound.  Most cables are either fully molded as a single piece, or have 
the cable jacked pushed back and reformed into a plug and the connector shell is 
made around that.  Take apart a few and you'll see that most aren't made like 
you're talking about in the first place, so it's probably a bad way to go..  The 
ones that are are the same material and solvent welded, you're not likely to 
accomplish that with random wire jackets and potting material.  Most wires have 
release agents and/or a thin oil film from machine handling, you'd need a very 
good strip and roughen before even trying to glue.  Simply not worth the effort 
vs more normal mechanical methods.

Alan

Hi,

I'm fabricating my own vacuum chamber right now.  I'm using a 
pressure cooker and 2 venturi pumps (PneuAire) connected to a 
ordinary shop air compressor.  I'm waiting for a reply from Maesco 
for prices on their vacuum dial indicators.

The 9L. pressure cooker was on sale at Canadian Tire for $55, about 
the same price on EBay for a used unit.  Once I perfect the process, 
I'm buying a 2nd pressure cooker, cutting the bottom on the 1st unit 
and having it welded on top of the 2nd one.

That way I can expand my capacity and retain the existing plumbing.  
The pumps and dial indicator are mounted on the existing holes in the 
lid.

The nice feature of the pressure cooker is the quick release 
mechanism.  I was considering cutting & welding 2 barbecue tanks 
together, but I'd have to fabricate a sealing section.

About degassing liquid plastics, unless I read wrong you have 2 
alternatives (I'm not sure if this applies to other liquids):

1. place the unpoured mix in a vacuum chamber.
2. place the cast along with the poured mix in a high-pressure 
chamber.

Robert
:)

(sorry if this info was already discussed, I haven't read the entire 
thread and I'm searching for Silkscreen information, this topic just 
caught my eye)

Note: www.SmoothOn.com is an excellent source is materials for 
casting.  I use liquid plastic #326 for my casings.


> you don't vacuum the mold, you need a small vacuum chamber in which 
you  
> put the container of silicone or whatever you want to use to cast. 
the  
> vacuum makes the bubbles HUGH and causes them to rise to the 
surface,  
> effectively de-gassing the liquid. then you take the liquid out and 
cast  
> with it.
> Of course you can also vacuum the un-cured mold and pattern just 
after  
> casting if it fits into the chamber.
> 
> You can join <http://groups.yahoo.com/group/casting/> for more 
information.
> I was looking into it a short while back, but decided it is too 
expensive  

> and i have enough stuff to do right now. But it opens a lot of  
> possibilities...
> 
> ST

On Thu, 05 May 2005 19:57:19 -0000, Robert Hedan  
<robert.hedan@...> wrote:

> About degassing liquid plastics, unless I read wrong you have 2
> alternatives (I'm not sure if this applies to other liquids):
> 1. place the unpoured mix in a vacuum chamber.
> 2. place the cast along with the poured mix in a high-pressure
> chamber.
> Robert
>


there is a good group on casting (casting@...).
Go there!

You can basically degass both, the moulding material and the stuff you use  
to make the part.
You do not _need_ to degass anything, if you don't run into problems.

Vacuum makes the gas huge, causing it to rise to the surface and be  
removed.
Pressure compresses the bubbles, they are still there, just compressed.

vacuuming removes the gas, it basically can't be bad. (tho make sure you  
don't "cook" the material beyond the point where all gass is gone, at  
enough reduced pressure everything will cook at room temperature). But if  
you don't run into trouble don't bother to do it.

Pressuring is what i have read only useful in very limited applications,  
for example casting clear parts where the gas is shrunk so tiny you can no  
longer see it. (The casting must be put in the chamber, with the mould,  
and stay pressurized until cured).

remember that if you pressurize a mould with bubbles, it will form small  
hollows where the bubbles are close to the surface.

And most importantly: remember vacuum chanber failures are REALLY BAD!!  
And pressure chamber failures are REALLY BAD!!. Even something like a seal  
blowout can seriously damage your hearing. a 1 liter container opening  
rapidly at only 1 or 2 athmospheres is really loud, you would not expect  
it.
And also remember i did only lurk around the casting group for a few days,  
deciding it is to complicated and expensive for me to get involved with at  
this point, so i know nothing about it, at all.

But this is the wrong group for this anyway.

ST

I didn't get the start of this thread so I'm getting in late.  I take it 
that the object is to make some custom connectors.  I do this routinely to 
make connectors that will fit into the recesses of my models.  I also use 
vacuum equipment to make castings and laminates (and on occasion a spy 
satellite) so I have some experience with that process as well.

First, as far as safety is concerned, a pressurized vessel is far more 
dangerous than a vacuum vessel.  I was the safety officer for our autoclave. 
To make me more attentive to the safety concerns, my office was in a direct 
line with the autoclave door.  If the thing blew, I'd go right along with it 
across I-95.  I made sure it wouldn't blow.  Everyone probably has several 
dozen vacuum chambers in their homes in the form of light bulbs.  Failure of 
a vacuum chamber results in things being drawn into the chamber, away from 
the operator.  As long as the structure doesn't shatter (like a light bulb) 
not much harm can come of it.  A pressure vessel failure can cause major 
distruction even at relatively low pressures.

For potting connectors, there is probably no need for either vacuum or 
pressure pots.  There are epoxy formulations which will degas with little or 
no assistance.  The biggest problem is keeping the uncured epoxy in place 
while not contaminating the electrical contacts.  I've used Epon 814 and 
Versamid 104 mixed at a @:1 ratio to pot circuit boards.  This is not the 
recommended mix ratio, but cured at 105\ufffdF overnight it produces a bubble 
free solid matrix.  If you can construct a 2 part mold and figure out how to 
keep the resin from leaking out the bottom, it should be fairly easy to 
produce your custom connectors.

For my purposes, since each connector is unique, I just plug headers and 
sockets together (I use perf board to position the parts and major cutting 
and fitting is usually required) then I use a brush to coat them with a 
thixotropic epoxy paste.  I then stick the whole mess into the spot where 
they will have to fit (mold released of course) and let them cure.  Do this 
once for the male side and once for the female side and I have a connector 
fitted to the particular installation.

Grant.
Light bulbs contain inert gas at atmospheric pressure.

Vacuum tubes (thermionic valves) contain? a vacuum. 

This is why the glass is so much thicker than a light bulb. 

The most dangerous example of the devices is the large TV picture tube. 

If you have a look the faceplate glass is quite thick, especially on the
super flat screens.

Cheers
Brian

-------Original Message-------
 
From: Homebrew_PCBs@yahoogroups.com
Date: 05/06/05 09:08:10
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Re: Cables and connectors - vacuum chamber
 
Snip>
  Everyone probably has several
dozen vacuum chambers in their homes in the form of light bulbs.  Failure of
a vacuum chamber results in things being drawn into the chamber, away from
the operator.  As long as the structure doesn't shatter (like a light bulb)
not much harm can come of it.   
< Snip
 

[Non-text portions of this message have been removed]

In a message dated 5/5/2005 4:07:58 P.M. Eastern Daylight Time,  
robert.hedan@... writes:

Hi,

I'm fabricating my own vacuum chamber right now.  I'm  using a 
pressure cooker and 2 venturi pumps (PneuAire) connected to a  
ordinary shop air compressor.  I'm waiting for a reply from Maesco  
for prices on their vacuum dial indicators.



Gang,
One word of caution here! Tanks and such designed for PREASURE  don't 
necessarily make good vacuum chambers! Catastrophic implosion can be just  as deadly 
as explosion! Please be careful! The best vacuum chambers I have seen  are 
just big enough to handle your need and made out of heavy lexan or  plexiglass
Just be safe out there! 
 
Ray Russell
NMRA-40609
General Contractor
Norfolk &  Western Railroad
Pocahontas Division
Circa 1958
Visit The "NEW"  Pocahontas Website at:_ Click here: N  & W Pocahontas  
Division_ (http://members.aol.com/rruss45826/public_html/index.html) 
http://members.aol.com/rruss45826/public_html/index.html

OR_ Click here:  Pocahontas Home_ 
(http://milliron.home.sprynet.com/Pocahontas/Pocahontas1.htm)  
For the old website!  
http://milliron.home.sprynet.com/Pocahontas/Pocahontas1.htm


[Non-text portions of this message have been removed]

In a message dated 5/5/2005 4:32:33 P.M. Eastern Daylight Time,  
stefan_trethan@... writes:

And most  importantly: remember vacuum chanber failures are REALLY BAD!!  
And  pressure chamber failures are REALLY BAD!!. Even something like a seal   
blowout can seriously damage your hearing. a 1 liter container  opening  
rapidly at only 1 or 2 athmospheres is really loud, you  would not expect  
it.



Wow! Talk about Karma! I just wrote the same thing before I  read yours.
So to all of you attempting this out there! Do this in a safe  zone and don't 
be anywhere near it while it is functioning!
 
 
Ray Russell
NMRA-40609
General Contractor
Norfolk &  Western Railroad
Pocahontas Division
Circa 1958
Visit The "NEW"  Pocahontas Website at:_ Click here: N  & W Pocahontas  
Division_ (http://members.aol.com/rruss45826/public_html/index.html) 
http://members.aol.com/rruss45826/public_html/index.html

OR_ Click here:  Pocahontas Home_ 
(http://milliron.home.sprynet.com/Pocahontas/Pocahontas1.htm)  
For the old website!  
http://milliron.home.sprynet.com/Pocahontas/Pocahontas1.htm


[Non-text portions of this message have been removed]

Are there other dangers besides sound waves?  I can easily protect against
that, I have high-quality ear protectors used at the firing range.

If a chamber implodes, can debris be projected outwards...?

Or is the contained liquid a source of danger?  If so, I could easily drape
the unit with several layers of thick cloth.  If there are no metallic
projectiles, that should be enough.

If I could afford a new vacuum chamber, I'd buy one.  But the realities of
family life and trying to set up a lab is not compatible.  I have to cut
corners, but I'm also trying to cut them as safely as I can.

Robert
:)



-----Message d'origine-----
De : Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com] De
la part de rruss45826@...
Envoyé : mai 6 2005 00:17
À : Homebrew_PCBs@yahoogroups.com
Objet : Re: [Homebrew_PCBs] Re: Cables and connectors - vacuum chamber


 
In a message dated 5/5/2005 4:32:33 P.M. Eastern Daylight Time,  
stefan_trethan@... writes:

And most  importantly: remember vacuum chanber failures are REALLY BAD!!  
And  pressure chamber failures are REALLY BAD!!. Even something like a seal

blowout can seriously damage your hearing. a 1 liter container  opening  
rapidly at only 1 or 2 athmospheres is really loud, you  would not expect  
it.



Wow! Talk about Karma! I just wrote the same thing before I  read yours. So
to all of you attempting this out there! Do this in a safe  zone and don't 
be anywhere near it while it is functioning!
 
 
Ray Russell




Be sure to visit the group home and check for new Bookmarks and files:
http://groups.yahoo.com/group/Homebrew_PCBs 
Yahoo! Groups Links

In a message dated 5/6/2005 12:41:53 A.M. Eastern Daylight Time,  
robert.hedan@... writes:

Are  there other dangers besides sound waves?  I can easily protect  against
that, I have high-quality ear protectors used at the firing  range.

If a chamber implodes, can debris be projected  outwards...?

Or is the contained liquid a source of danger?  If  so, I could easily drape
the unit with several layers of thick cloth.   If there are no metallic
projectiles, that should be enough.

If I  could afford a new vacuum chamber, I'd buy one.  But the realities  of
family life and trying to set up a lab is not compatible.  I have  to cut
corners, but I'm also trying to cut them as safely as I  can.

Robert
:)




Sound waves can shatter your ear drums. Your heavy layers of  cloth will 
probably not help much here but your ear protectors are a good bet.  While it is 
true that explosion is worse, implosion carries some of the same  issues. Stuff 
can fly. Here a heavy blanket is best. The other thing that most  people 
don't think about is shock factor. What are you doing when it blows (Or  sucks in 
this case! 8>)) LOL If you are cutting out a previous mold you could  
seriously cut yourself or others.
PLEASE! I am not trying to scare you! Just be prudent and be  careful! Keep 
the kids out of the way! ALWAYS ALWAYS test out a new device of  this type 
OUTSIDE for the first couple of times! If your going to pull it down 2  
atmospheres normally pull it down to 3 several times as a safety check!  A  failure 
outside is a whole lot safer then inside!
In closing just be safe! I have 3rd degree burns over 33% of  my body from a 
stupid mistake 20 years ago that to this day remind me to be  careful!
 
Ray Russell
NMRA-40609
General Contractor
Norfolk &  Western Railroad
Pocahontas Division
Circa 1958
Visit The "NEW"  Pocahontas Website at:_ Click here: N  & W Pocahontas  
Division_ (http://members.aol.com/rruss45826/public_html/index.html) 
http://members.aol.com/rruss45826/public_html/index.html

OR_ Click here:  Pocahontas Home_ 
(http://milliron.home.sprynet.com/Pocahontas/Pocahontas1.htm)  
For the old website!  
http://milliron.home.sprynet.com/Pocahontas/Pocahontas1.htm


[Non-text portions of this message have been removed]

Ok, so an exterior testing session is warranted and no dangerous operations
must be done while the contraption is on.  I can find a sand pit and put the
contraption in there for failure testing.  I have a van, so transporting my
5500W generator for the electric air compressor is not a problem either.

How can you pull the vacuum down 2 atmospheres?  Assuming I am at 1
atmosphere, isn't 0 a vacuum?  Or did I miss something and you can a bigger
vacuum?  Huh?  How can you go to negative atmosphere?  I thought atmospheres
were mostly used for pressure chambers.

I often see reference to 0-30Hg for vacuum chambers, something about mercury
level.  I figure I'll see where the vacuum dial sits at rest, and where it
goes as air is pumped out is the vacuum side.

Robert
:)




Sound waves can shatter your ear drums. Your heavy layers of  cloth will 
probably not help much here but your ear protectors are a good bet.  While
it is 
true that explosion is worse, implosion carries some of the same  issues.
Stuff 
can fly. Here a heavy blanket is best. The other thing that most  people 
don't think about is shock factor. What are you doing when it blows (Or
sucks in 
this case! 8>)) LOL If you are cutting out a previous mold you could  
seriously cut yourself or others.
PLEASE! I am not trying to scare you! Just be prudent and be  careful! Keep 
the kids out of the way! ALWAYS ALWAYS test out a new device of  this type 
OUTSIDE for the first couple of times! If your going to pull it down 2  
atmospheres normally pull it down to 3 several times as a safety check!  A
failure 
outside is a whole lot safer then inside!
In closing just be safe! I have 3rd degree burns over 33% of  my body from a

stupid mistake 20 years ago that to this day remind me to be  careful!
 
Ray Russell


Be sure to visit the group home and check for new Bookmarks and files:
http://groups.yahoo.com/group/Homebrew_PCBs 
Yahoo! Groups Links

In a message dated 5/6/2005 1:21:48 A.M. Eastern Daylight Time,  
robert.hedan@... writes:

How can  you pull the vacuum down 2 atmospheres?  Assuming I am at  1
atmosphere, isn't 0 a vacuum?  Or did I miss something and you can a  bigger
vacuum?  Huh?  How can you go to negative  atmosphere?  I thought atmospheres
were mostly used for pressure  chambers.

I often see reference to 0-30Hg for vacuum chambers,  something about mercury
level.  I figure I'll see where the vacuum  dial sits at rest, and where it
goes as air is pumped out is the vacuum  side.

Robert
:)



Most vacuum is measured in HG which is mercury. being so heavy  you can use a 
much smaller scale! Now if I remember my old school books normal  atmosphere 
at sea level is about 15lb's per sq inch. Now 2 Ats. would be 30lbs  per sq 
inch. No go to vacuum and the same applies but in the opposite. So 30HG  vacuum 
would be 2 Ats. When I do A/C work this is the standard test we do. Draw  down 
to as close to -30 hg and cap it off. wait 1 hour and see if we have any  
leaks then charge the system.
If I did not get any of the math right I am sure someone will  jump in and 
correct it! High school was a long time ago! LOL
Just putting the mold under 1 At or -15lbs  of vacuum  will do the job you 
need to do!
 
Ray Russell
NMRA-40609
General Contractor
Norfolk &  Western Railroad
Pocahontas Division
Circa 1958
Visit The "NEW"  Pocahontas Website at:_ Click here: N  & W Pocahontas  
Division_ (http://members.aol.com/rruss45826/public_html/index.html) 
http://members.aol.com/rruss45826/public_html/index.html

OR_ Click here:  Pocahontas Home_ 
(http://milliron.home.sprynet.com/Pocahontas/Pocahontas1.htm)  
For the old website!  
http://milliron.home.sprynet.com/Pocahontas/Pocahontas1.htm


[Non-text portions of this message have been removed]

On Fri, 6 May 2005 00:57:41 EDT, <rruss45826@...> wrote:

>
> PLEASE! I am not trying to scare you! Just be prudent and be  careful!  
> Keep
> the kids out of the way! ALWAYS ALWAYS test out a new device of  this  
> type
> OUTSIDE for the first couple of times! If your going to pull it down 2
> atmospheres normally pull it down to 3 several times as a safety check!   
> A  failure
> outside is a whole lot safer then inside!


I did not know one could pull a vacuum of more than one athmosphere ;-)
On which planet (or under how much water) do you need to be to do this?

Implosions are generally just as dangerous. while the pressure differences  
are smaller than with pressure tanks my personal theory is the lack of air  
inside is the reason why flying debris is not decelerated on it's way to  
the center. It does not stop there of course.

Testing a pressure tank is done with water, maybe a simliar approach is  
good with vacuum. I could imagine filling it with old clothes for the  
first try would help with the risk. (Using a liquid could be a problem  
with the pump and boiling..)

That said, i think with a stainless steel tank such as a pressure cooker  
the risk is acceptable.
Go to casting@yahoogroups, when i was there this very topic was discussed  
to exhaustion.

ST

The 30 Hg is the height in inches of a column of mercury supported by 
the vacuum (980 millimeters, for you metric buffs, , IIRC) -   NOT the 
weight in pounds. That corresponds to 14.7 lbs per square inch (sea 
level, normal temperature).  You can't do better than 1 atmosphere of 
vacuum, even in outer space!

On the other hand, for outgassing resin, you don't need near perfect 
vacuum; even a 5 pound vacuum will draw out lots of bubbles.  Just use a 
less viscous resin mix, or pump longer.  Also, periodically relieving 
the vacuum and then pumping some more seems to help.

Norm

rruss45826@... wrote:

> 
>In a message dated 5/6/2005 1:21:48 A.M. Eastern Daylight Time,  
>robert.hedan@... writes:
>
>How can  you pull the vacuum down 2 atmospheres?  Assuming I am at  1
>atmosphere, isn't 0 a vacuum?  Or did I miss something and you can a  bigger
>vacuum?  Huh?  How can you go to negative  atmosphere?  I thought atmospheres
>were mostly used for pressure  chambers.
>
>I often see reference to 0-30Hg for vacuum chambers,  something about mercury
>level.  I figure I'll see where the vacuum  dial sits at rest, and where it
>goes as air is pumped out is the vacuum  side.
>
>Robert
>:)
>
>
>
>Most vacuum is measured in HG which is mercury. being so heavy  you can use a 
>much smaller scale! Now if I remember my old school books normal  atmosphere 
>at sea level is about 15lb's per sq inch. Now 2 Ats. would be 30lbs  per sq 
>inch. No go to vacuum and the same applies but in the opposite. So 30HG  vacuum 
>would be 2 Ats. When I do A/C work this is the standard test we do. Draw  down 
>to as close to -30 hg and cap it off. wait 1 hour and see if we have any  
>leaks then charge the system.
>If I did not get any of the math right I am sure someone will  jump in and 
>correct it! High school was a long time ago! LOL
>Just putting the mold under 1 At or -15lbs  of vacuum  will do the job you 
>need to do!
> 
>Ray Russell
>NMRA-40609
>General Contractor
>Norfolk &  Western Railroad
>Pocahontas Division
>Circa 1958
>Visit The "NEW"  Pocahontas Website at:_ Click here: N  & W Pocahontas  
>Division_ (http://members.aol.com/rruss45826/public_html/index.html) 
>http://members.aol.com/rruss45826/public_html/index.html
>
>OR_ Click here:  Pocahontas Home_ 
>(http://milliron.home.sprynet.com/Pocahontas/Pocahontas1.htm)  
>For the old website!  
>http://milliron.home.sprynet.com/Pocahontas/Pocahontas1.htm
>
>
>[Non-text portions of this message have been removed]
>
>
>
>
>Be sure to visit the group home and check for new Bookmarks and files:
>http://groups.yahoo.com/group/Homebrew_PCBs 
>Yahoo! Groups Links
>
>
>
> 
>
>
>
>
>  
>



-- 
Internal Virus Database is out-of-date.
Checked by AVG Anti-Virus.
Version: 7.0.308 / Virus Database: 266.11.0 - Release Date: 4/29/2005

Norm Stewart wrote:
> The 30 Hg is the height in inches of a column of mercury supported by 
> the vacuum (980 millimeters, for you metric buffs, , IIRC)

More like 760mm. 1 Torr = 1mm Hg.

On Thursday 05 May 2005 09:07 pm, Brian Clancy wrote:
>  Grant.
> Light bulbs contain inert gas at atmospheric pressure.

I was of the impression that it was at somewhat lower than atmospheric 
pressure,  otherwise you wouldn't get that "pop" when they break.

> Vacuum tubes (thermionic valves) contain? a vacuum.

As close as they could get to it,  yeah.

> This is why the glass is so much thicker than a light bulb.

Not that much thicker,  overall.  I sure broke enough of them when I first 
started messing around with this stuff.around with it,  about 40 years or so 
ago.  Maybe more so if you're talking large transmitting tubes,  but those 
aren't exactly common.

> The most dangerous example of the devices is the large TV picture tube.

Those are rather dangerous,  yeah.

> If you have a look the faceplate glass is quite thick, especially on the
> super flat screens.

The reason for that is two things --  that the outer layer of it isn't glass, 
but instead is a rather thick plastic that won't shatter.  Early sets had a 
separate safety glass and the face of the tube was much thinner.  The other 
reason it's that thick is because of lead in the glass to absorb x-rays,  at 
least for color tubes,  which is what makes TV sets and monitors a bit 
"hazmat" rather than just being able to put 'em in the trash.  Monochrome 
monitors and old B&W tv sets don't have that issue.

On Fri, 6 May 2005 14:57:54 -0400, Roy J. Tellason  
<rtellason@...> wrote:

>
>> Light bulbs contain inert gas at atmospheric pressure.
> I was of the impression that it was at somewhat lower than atmospheric
> pressure,  otherwise you wouldn't get that "pop" when they break.
>

It is lower than athm., put a propane torch against it and the softening  
glass will be pulled in.
(yes i am aware that experiment could have resulted in shattering hot  
shards and be beeing blind...)
There's Argon in there.

> The other
> reason it's that thick is because of lead in the glass to absorb  
> x-rays,  at
> least for color tubes,  which is what makes TV sets and monitors a bit
> "hazmat" rather than just being able to put 'em in the trash.  Monochrome
> monitors and old B&W tv sets don't have that issue.


Why is x-rays created, and why is it not beeing created in BW TVs?
Always wondered..

Hell this is getting OT.. maybe we should take it to E_101.

ST

On Friday 06 May 2005 03:13 pm, Stefan Trethan wrote:
> On Fri, 6 May 2005 14:57:54 -0400, Roy J. Tellason
>
> <rtellason@...> wrote:
> >> Light bulbs contain inert gas at atmospheric pressure.
> >
> > I was of the impression that it was at somewhat lower than atmospheric
> > pressure,  otherwise you wouldn't get that "pop" when they break.
>
> It is lower than athm., put a propane torch against it and the softening
> glass will be pulled in.
> (yes i am aware that experiment could have resulted in shattering hot
> shards and be beeing blind...)

It takes a certain technique to work with glass and have it not shatter.  I 
found that out the hard way back when I was into messing around with 
chemistry sets and such stuff.

> There's Argon in there.

What I thought.

> > The other reason it's that thick is because of lead in the glass to absorb
> > x-rays,  at least for color tubes,  which is what makes TV sets and
> > monitors a bit "hazmat" rather than just being able to put 'em in the
> > trash.  Monochrome monitors and old B&W tv sets don't have that issue.
>
> Why is x-rays created, and why is it not beeing created in BW TVs?
> Always wondered..

Higher voltage.  Typical monocrhome tube uses no more than 12-15KV for an 
acceleratign potential,  color tubes use 25-30KV.  Apparently that's enough 
to make a difference.

I can still remember the old tube-type color sets where the HV rectifier and 
regulator tube were enclosed in metal,  and if they'd been in service for a 
while the glass would be a dark brown color from xray bombardment.

Stefan Trethan wrote:

>On Fri, 6 May 2005 14:57:54 -0400, Roy J. Tellason  
><rtellason@...> wrote:
>
>  
>
>>>Light bulbs contain inert gas at atmospheric pressure.
>>>      
>>>
>>I was of the impression that it was at somewhat lower than atmospheric
>>pressure,  otherwise you wouldn't get that "pop" when they break.
>>
>>    
>>
>
>It is lower than athm., put a propane torch against it and the softening  
>glass will be pulled in.
>(yes i am aware that experiment could have resulted in shattering hot  
>shards and be beeing blind...)
>There's Argon in there.
>
>  
>
>>The other
>>reason it's that thick is because of lead in the glass to absorb  
>>x-rays,  at
>>least for color tubes,  which is what makes TV sets and monitors a bit
>>"hazmat" rather than just being able to put 'em in the trash.  Monochrome
>>monitors and old B&W tv sets don't have that issue.
>>    
>>
>
>
>Why is x-rays created, and why is it not beeing created in BW TVs?
>Always wondered..
>
>Hell this is getting OT.. maybe we should take it to E_101.
>
>ST
>
>  
>
B/W tv's used 15Kv or so accelerating voltage - created soft x-rays.  
Color sets needed more energetic electrons for the color phosphors, so 
used  ~23Kv, IIRC, and generated harder x-rays. The x-rays are only 
generated while the HV is on - they are not residual.  Any hazmat must 
be in the toxicity of the phosphors used to generate the colors.

Norm


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No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.308 / Virus Database: 266.11.5 - Release Date: 5/4/2005

On Friday 06 May 2005 06:01 pm, Norm Stewart wrote:

> >>The other reason it's that thick is because of lead in the glass to absorb
> >>x-rays,  at least for color tubes,  which is what makes TV sets and
> >>monitors a bit "hazmat" rather than just being able to put 'em in the
> >>trash.  Monochrome monitors and old B&W tv sets don't have that issue.
> >
> >Why is x-rays created, and why is it not beeing created in BW TVs?
> >Always wondered..
> >
> >Hell this is getting OT.. maybe we should take it to E_101.
> >
> >ST
>
> B/W tv's used 15Kv or so accelerating voltage - created soft x-rays.

Even that's a little high,  12KV was more common.

> Color sets needed more energetic electrons for the color phosphors, so
> used  ~23Kv, IIRC, 

25KV was more common,  and in the earlier tube stuff the shunt-type regulator 
tube would age,  and the voltage would climb somewhat,  except of course that 
the tube-type HV rectifier was also aging.  Then there was the occasional 
fault,  like the infamous "4-legged capacitor" that Zenith had a problem 
with.  It seems that the cap maker substituted materials or similar and these 
failed rapidly,  and drastically,  allowing the HV to go up over 40KV.  
Sometimes it was so bad it'd arc right through the glass and crack the tube.  
All of those failures were covered under warranty by Zenith,  which was also 
a matter in a lawsuit with the cap maker.

> and generated harder x-rays. The x-rays are only generated while the HV is
> on - they are not residual.  Any hazmat must be in the toxicity of the
> phosphors used to generate the colors.

It's the lead in the faceplate glass -- read what I wrote up there.

In a message dated 5/6/2005 2:16:34 A.M. Central Daylight Time,  
rjshaw@... writes:

(980  millimeters, for you metric buffs, , IIRC)



WYB 760 mm!


[Non-text portions of this message have been removed]

I should have been more specific - we use fluorescent lights.

As for vacuum chambers, I just measured mine.  It's a commmercial unit made 
of an acrylic type plastic, 1/8" thick,  12" in diameter, 12" high with a 
flat top.

----- Original Message ----- 

From: "Stefan Trethan" <stefan_trethan@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, May 06, 2005 3:13 PM
Subject: Re: [Homebrew_PCBs] Re: Cables and connectors - vacuum chamber


> On Fri, 6 May 2005 14:57:54 -0400, Roy J. Tellason
> <rtellason@...> wrote:
>
>>
>>> Light bulbs contain inert gas at atmospheric pressure.

On Sat, 7 May 2005 06:27:46 -0400, Earl T. Hackett, Jr.  
<hacketet@...> wrote:

> I should have been more specific - we use fluorescent lights.


well, there's a gas in there too..

ST