[sdiy] Found good vacuum pump for desoldering iron, but request pointers...

[Roy J. Tellason]

On Monday 07 July 2008 14:58, anthony wrote:
> Hello all,
>
> I remembr a thread a while back about using a small pump, like one salvaged
> from a small air conditioner. Kind of a messy idea - I've done it before.
> They do make great vacuum pumps, but they're hard to cool if used
> constantly... and they're HEAVY if  they're not from a really small A/C or
> a dehumidifier (which is the best way to go in this regard). Well anyway,
> enough of THAT bother...

Heavy doesn't mean squat if the unit's sitting on the floor,  which is where 
mine usually sits...

> When I was taking my trash to the local dump/recycling center, I checked
> out the "Tradin' Post" as I always do and I found a Salter AIRE Plus.
> Looked like a medical air compressor (it was) AND one that I could asilly
> turn into a nice vacuum pump (unlike the cigar lighter powered air
> compressor I found last week - which was actually SMALLER!).

I just salvaged one of those,  "didn't work" and here the tubing was split 
right at the pump.

> Anyway, I got it home and opened it up and since it needs a filter there is
> a nice little hose fitting for the end that would be the point I would use
> for a vacuum pump. It's a really nice piston-style pump, air-cooled with
> its own little fan (well the fan-blade is just on the rotor of the pump
> motor, which is pretty stout for such a compact unit.

Mine uses a dual diaphragm pump,  with both sections teed together.  For a 
filter I use a glass-bowl setup that was originally a fuel filter for 
something.  I'm not sure what,  but apparently filter cartridges are still 
easily available,  AC Delco brand.  I would *not* try to use a disposable 
filter.

> OK, so getting it to be a vacuum pump is the easy part. I'm just wondering
> what the best way would be to use it to replace the hand-pump bulb on my
> radio shack desoldering iron. I thought about making the bulb rigid a
> little bit somehow by glueing tubing around it and then cutting a little
> hole to connect a nib to then connect it to the vacuum pump.

I've not had one of those irons,  they didn't look too terrific in the store.  
I've had the bulb-type sucker (ridiculous!) and the Soldapullit brand 
pump-type sucker.  The first tip I used was off one of those,  surrounded by 
blue plastic that I cut away.  Later I found that the teflon tip itself was 
available by itself.  That's coupled to a hunk of 5/8" or so hose,  maybe 5 
or 6 feet long,  by way of a brass fitting.

I should probably take some pics one of these days.

> My concern is that the solder has to go SOMEWHERE.

In my unit it almost all ends up in the hose,  excepting some fine powder that 
ends up in the filter.

> Should I just try to find some silicone (or other high temp.) tubing and run
> that to a little jelly jar with two holes in the lids: one for the
> desoldering iron end and the other to connect to the pump?

You don't need to worry about high-temp,  that solder will be cooled off quite 
well by the time it gets an inch or so away from the joint you're pulling it 
out of.

> Also does it not work as well to have the pump on all the time? I have a
> footswitch ready, but I tought having it try to pull a harder vacuum
> constantly and then releasing tis vacuum when need with a pin valve migh
> work well. I guess it might be tricky to activate a pin valve with a foot
> pedal. And would it really need to be a pin valve I wonder? But the pump
> really seems to pull a good hard vacuum right at start up, so the
> foot-switch might be the best way to go.

I used a footswitch with mine until the switch burned up.  I've been meaning 
to replace that with a circuit I ran across someplace that uses two buttons 
to turn it on and off.  Pretty nifty circuit,  actually,  it uses a triac and 
a capacitor.  I just haven't gotten around to building it yet.

> I was just wondering mostly about the plumbing and what to do with the
> flying molten solder.

The plumbing isn't an issue,  really.  I started out using some steel brake 
line and rubber "vacuum line" (like you used to find all over in cars before 
they went to the thinner stuff) but that didn't give sufficient airflow,  so 
I switched to half inch or so copper tubing since I had a bit of it around 
and that 5/8" or so clear stuff.  It's too bad I ended up having to buy all 
new fittings to do that...

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
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