Scrims.....

Genesis · 9th September 2006, 03:45

Getting into the guts of the cannister now.... having made up the button bosses and buttons for my handsets with the lathe and awaiting only the proper springs and magnets from McMaster, its time to deal with the scrim issues and connections.

It appears that I am going to need to use stainless - or something similar - for the scrims to hold the rocks in top and bottom. If I'm reading the specs on 6-12 mesh right, the particle size is anywhere from .0661 to .132.

So - it appears I have two basic approaches here:

1. Use a fairly open mesh for the "hard bottom" and "hard top" (the boundary of the cannister that actually holds in the rocks) and then use what amounts to a screen (e.g. fiberglass, polypropylene, etc) sheet material to retain the rocks UNDER that. In otherwords, the structural component is the heavy (and big-meshed) material, while the screen provides the holding but is not structural in its content.

2. Find something with a small enough mesh size in heavy enough gauge to do the job DIRECTLY.

The latter sounds harder; McNichols, for example, has SS mesh but the smallest hole size they have is .045 (which would work), and that only in 24 gauge, which is going to be too light for a structural material with the span that will be involved. If I go up to 1/16th holes (.0625) that's awfully close to being able to drop through and that's available only up to 20 gauge.

How have others solved this problem - or am I reading the specs on the kitty litter wrong?

DepthCharge · 9th September 2006, 04:53

Quote: (Originally Posted by Genesis)

Getting into the guts of the cannister now.... having made up the button bosses and buttons for my handsets with the lathe and awaiting only the proper springs and magnets from McMaster, its time to deal with the scrim issues and connections.

It appears that I am going to need to use stainless - or something similar - for the scrims to hold the rocks in top and bottom. If I'm reading the specs on 6-12 mesh right, the particle size is anywhere from .0661 to .132.

So - it appears I have two basic approaches here:

1. Use a fairly open mesh for the "hard bottom" and "hard top" (the boundary of the cannister that actually holds in the rocks) and then use what amounts to a screen (e.g. fiberglass, polypropylene, etc) sheet material to retain the rocks UNDER that. In otherwords, the structural component is the heavy (and big-meshed) material, while the screen provides the holding but is not structural in its content.

2. Find something with a small enough mesh size in heavy enough gauge to do the job DIRECTLY.

The latter sounds harder; McNichols, for example, has SS mesh but the smallest hole size they have is .045 (which would work), and that only in 24 gauge, which is going to be too light for a structural material with the span that will be involved. If I go up to 1/16th holes (.0625) that's awfully close to being able to drop through and that's available only up to 20 gauge.

How have others solved this problem - or am I reading the specs on the kitty litter wrong?

I would think that #1 is the easiest and most cost effective for an axial scrubber. The "hard" bottom/top can be just a thick sheet waterjetted into a pattern ala Inspiration "spider web".

Genesis · 9th September 2006, 05:21

Actually you don't need to waterjet it - you can drill it on a drill press pretty easily, or if you have a small mill, mill it out of sheet stock.

I think that's the easiest too, but was wondering if anyone had approached it differently.....

The can I'm building is coaxial.... (center "dip tube" for inbound gas)

DepthCharge · 9th September 2006, 07:57

Quote: (Originally Posted by Genesis)

Actually you don't need to waterjet it - you can drill it on a drill press pretty easily, or if you have a small mill, mill it out of sheet stock.

I think that's the easiest too, but was wondering if anyone had approached it differently.....

The can I'm building is coaxial.... (center "dip tube" for inbound gas)

I like the waterjet because:
1. I do have limited access to one

and most imoprtantly
2. I don't have to do it, some else runs the thing

Simon A · 10th September 2006, 01:49

genesis,
there are many ways to do this, but if the OD is large enough, the easiest way for you, may well be to machine up a couple of "spiders" and just buy some inspo scrims and cut them for the dip tube, the inspo scrims are about $8 a pair.
HTH
Simon A

Genesis · 12th September 2006, 13:47

Does anyone have the specs are on the Inspo scrims?

I found this site out there and it looks interesting.....

Polypropylene Mesh | Cloth Screening | Polymesh

That'll definitely do the job..... the only issue would be retaining the edges (epoxy might work, or I could try thermally bonding it to the substrate)

9th September 2006, 03:45	#1 (permalink)
Genesis Bubbless Box of Death Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Oct 2005 Location: Sunny Florida Posts: 1,453	Scrims..... Getting into the guts of the cannister now.... having made up the button bosses and buttons for my handsets with the lathe and awaiting only the proper springs and magnets from McMaster, its time to deal with the scrim issues and connections. It appears that I am going to need to use stainless - or something similar - for the scrims to hold the rocks in top and bottom. If I'm reading the specs on 6-12 mesh right, the particle size is anywhere from .0661 to .132. So - it appears I have two basic approaches here: 1. Use a fairly open mesh for the "hard bottom" and "hard top" (the boundary of the cannister that actually holds in the rocks) and then use what amounts to a screen (e.g. fiberglass, polypropylene, etc) sheet material to retain the rocks UNDER that. In otherwords, the structural component is the heavy (and big-meshed) material, while the screen provides the holding but is not structural in its content. 2. Find something with a small enough mesh size in heavy enough gauge to do the job DIRECTLY. The latter sounds harder; McNichols, for example, has SS mesh but the smallest hole size they have is .045 (which would work), and that only in 24 gauge, which is going to be too light for a structural material with the span that will be involved. If I go up to 1/16th holes (.0625) that's awfully close to being able to drop through and that's available only up to 20 gauge. How have others solved this problem - or am I reading the specs on the kitty litter wrong? __________________ "A venturesome minority will always be eager to get off on their own, and no obstacles should be placed in their path; let them take risks for Godsake, let them get lost, sunburnt, stranded, drowned, eaten by bears, buried alive under avalanches - that is the right and privilege of any free American." http://www.denninger.net http://www.diversunion.org/liability.htm - Fix the Diving Cert racket Last edited by Genesis : 9th September 2006 at 03:50.
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9th September 2006, 04:53	#2 (permalink)
DepthCharge New Member Current Rebreather/s: Inspiration Classic Home Build Other Rebreather/s: Home Build Join Date: Mar 2005 Location: upstate NY Posts: 234	Re: Scrims..... Quote: (Originally Posted by Genesis) Getting into the guts of the cannister now.... having made up the button bosses and buttons for my handsets with the lathe and awaiting only the proper springs and magnets from McMaster, its time to deal with the scrim issues and connections. It appears that I am going to need to use stainless - or something similar - for the scrims to hold the rocks in top and bottom. If I'm reading the specs on 6-12 mesh right, the particle size is anywhere from .0661 to .132. So - it appears I have two basic approaches here: 1. Use a fairly open mesh for the "hard bottom" and "hard top" (the boundary of the cannister that actually holds in the rocks) and then use what amounts to a screen (e.g. fiberglass, polypropylene, etc) sheet material to retain the rocks UNDER that. In otherwords, the structural component is the heavy (and big-meshed) material, while the screen provides the holding but is not structural in its content. 2. Find something with a small enough mesh size in heavy enough gauge to do the job DIRECTLY. The latter sounds harder; McNichols, for example, has SS mesh but the smallest hole size they have is .045 (which would work), and that only in 24 gauge, which is going to be too light for a structural material with the span that will be involved. If I go up to 1/16th holes (.0625) that's awfully close to being able to drop through and that's available only up to 20 gauge. How have others solved this problem - or am I reading the specs on the kitty litter wrong? I would think that #1 is the easiest and most cost effective for an axial scrubber. The "hard" bottom/top can be just a thick sheet waterjetted into a pattern ala Inspiration "spider web". __________________ Later, John It's better to beg forgiveness than ask permission
(Offline)

9th September 2006, 05:21	#3 (permalink)
Genesis Bubbless Box of Death Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Oct 2005 Location: Sunny Florida Posts: 1,453	Re: Scrims..... Actually you don't need to waterjet it - you can drill it on a drill press pretty easily, or if you have a small mill, mill it out of sheet stock. I think that's the easiest too, but was wondering if anyone had approached it differently..... The can I'm building is coaxial.... (center "dip tube" for inbound gas) __________________ "A venturesome minority will always be eager to get off on their own, and no obstacles should be placed in their path; let them take risks for Godsake, let them get lost, sunburnt, stranded, drowned, eaten by bears, buried alive under avalanches - that is the right and privilege of any free American." http://www.denninger.net http://www.diversunion.org/liability.htm - Fix the Diving Cert racket
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9th September 2006, 07:57	#4 (permalink)
DepthCharge New Member Current Rebreather/s: Inspiration Classic Home Build Other Rebreather/s: Home Build Join Date: Mar 2005 Location: upstate NY Posts: 234	Re: Scrims..... Quote: (Originally Posted by Genesis) Actually you don't need to waterjet it - you can drill it on a drill press pretty easily, or if you have a small mill, mill it out of sheet stock. I think that's the easiest too, but was wondering if anyone had approached it differently..... The can I'm building is coaxial.... (center "dip tube" for inbound gas) I like the waterjet because: 1. I do have limited access to one and most imoprtantly 2. I don't have to do it, some else runs the thing __________________ Later, John It's better to beg forgiveness than ask permission
(Offline)

10th September 2006, 01:49	#5 (permalink)
Simon A Escapee from DIY Rebreather's Current Rebreather/s: Inspiration Classic Other Rebreather/s: Not Bought Yet Join Date: Feb 2005 Location: Reading, UK Posts: 345	Re: Scrims..... genesis, there are many ways to do this, but if the OD is large enough, the easiest way for you, may well be to machine up a couple of "spiders" and just buy some inspo scrims and cut them for the dip tube, the inspo scrims are about $8 a pair. HTH Simon A Last edited by Simon A : 10th September 2006 at 01:52.
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12th September 2006, 13:47	#6 (permalink)
Genesis Bubbless Box of Death Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Oct 2005 Location: Sunny Florida Posts: 1,453	Re: Scrims..... Does anyone have the specs are on the Inspo scrims? I found this site out there and it looks interesting..... Polypropylene Mesh \| Cloth Screening \| Polymesh That'll definitely do the job..... the only issue would be retaining the edges (epoxy might work, or I could try thermally bonding it to the substrate) __________________ "A venturesome minority will always be eager to get off on their own, and no obstacles should be placed in their path; let them take risks for Godsake, let them get lost, sunburnt, stranded, drowned, eaten by bears, buried alive under avalanches - that is the right and privilege of any free American." http://www.denninger.net http://www.diversunion.org/liability.htm - Fix the Diving Cert racket
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