7 Mar
2014
7 Mar
'14
2:47 p.m.
I went down this path a few years ago and actually built a couple
prototype RL02 filters using the plastic frame of an old one and new
HEPA material from a few different selections of filters for home air
cleaners and automotive air filters. In the end, I found NOS DEC filters
in stock at one of the DEC parts suppliers and stocked up with enough
of them to last the rest of my life ;-)
I guess the concern with the homebrew ones was whether or not they
would allow the same air flow and pressure out at the media and head.
I didn't have any way to measure this although I started brainstorming
some kind of fixture to do so.
So, I think if I were going to try again, I would first build a test
rig that would allow comparing the air flow through an OEM filter to
a homebrew one so that you know you are not impeding the flow in any
seriously negative way. Once you have that, you can play with lots of
different media and find out what works and what doesn't.
I did also identify one firm that would custom build new filters into
the old frames at a pretty high cost but that might be palatable with
enough interested parties getting on board.
Chris
On Thursday (03/06/2014 at 10:11AM -0800), Mark J. Blair wrote:
I have a few DEC RL02 drives, and a Data General drive that uses a pack that appears
physically identical to the RL02 packs other than a different sector pulse ring. I
haven't begun the process of bringing any of them up yet, but I've removed the air
filter from the Data General drive to look at it. It looks like a standard style of HEPA
filter, with filter media zigzagged around wavy aluminum spacer plates and then mounted in
a plastic box. It looks quite gray on the input side, and he label suggests it was last
replaced in the mid to late 1980s. I assume that NOS filters for these drives aren't
just laying about in piles, and even if they are, a time will come when there aren't
any spares to be found. Thus, I'm interested in what it would take to overhaul
existing filters and/or fabricate new ones from scratch.
First of all, I assume that it's not practical to clean the existing filter media
very thoroughly. If I'm mistaken, then I'd like to know that.
It seems to me that I should be able to rebuild a filter like the one in my DG drive
assuming that A) I can get it apart without breaking the housing (may not be possible if
the edges of the media is strongly glued to the housing?), and B) I can obtain suitable
bulk HEPA filter cloth to use. Even if the housing can't be disassembled
nondestructively, I might be able to reuse the aluminum spacer plates at least.
By the same token, it should be possible to construct new filters from scratch as long as
the bulk HEPA filter cloth is available.
So, what have other folks already done in this area? Are there suppliers of bulk HEPA
filter cloth who would sell in the small quantities that a hobbyist would need? Maybe
suitable filter media can be harvested from off-the-shelf items like automotive air
filters?
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/
--
Chris Elmquist