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Re: De-potting and re-potting a pole pig: Insulation concerns.



Original poster: "Thomas Coyle" <zxcasd@xxxxxxxxx>

Like Dave, I also use a Harbor Freight unit for all of my heavy lifting. I use their foldable 2-ton crane:

<http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=46766>http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=46766

This thing rocks. It's built like a tank, and I've used it to transport my own 25kVA pig, along with a milling machine and countless other doohickeys between trucks, U-Hauls, and the like. The $200 it costs is basically the cost of the steel in scrap. Of course, it's better if you live in California so you can just pick it up without having to pay shipping, and if you get on HF's mailing list you'll regularly get 10% off coupons and the like. I think I paid about $150 for mine on some super-duper deal about a year ago. Since it folds, it takes up almost no space in the garage when you aren't using it.

The next thing is just to run down to Home Depot or the like and get some heavy-duty chain, and then run down to REI or another place that serves rock-climbers and pick up some heavy-duty carabiners. (For example, go to <http://www.rei.com>www.rei.com and lookup item 722353, which is what we use.)

For lifting large or oddly-shaped stuff, we just use some super-duty nylon straps like this:

<http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=36612>http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=36612

We used the crane plus one of those straps to lift the base for the big coil I bought last year which encloses the SRSG, caps, etc (weighs about 500 pounds all told and is a cube about three feet on a side). It was child's play.

The last thing you might want for those odd loads (big and much more heavy on one side than the other) is a load-leveller:

<http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=42356>http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=42356

This was key in moving the big radio-station-type RF filter that came with the coil I bought (it's about 4 feet long, 2 wide, 1 deep, and weighs 300 pounds, 250 of which is on one side).

Harbor Freight is just dangerous for people with hobbies like ours. :)

Tom




On 3/14/06, Tesla list <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx> wrote:
Original poster: "David Rieben" <<mailto:drieben@xxxxxxxxxxxxxxx>drieben@xxxxxxxxxxxxxxx >

Hi Aaron, Dave,

For lifting heavy piggies or x-ray trannies around in my shop,
I finally broke down and bought me a cheap, Chinese made
2-ton hydraulic engine hoist. It can handle ANY lifting that
I need to do that my muscular strength can't ;^) It really comes
in handy for hefting a pole pig into the back of my truck. I've also
handled x-ray tranformers that tipped the scales around 1000
lbs with it without a hitch.

I also use a ratchet cable "come-along" hoist to assist in the
heavy moving task if the engine hoist can't quiet reach the
load.

Not too sure about lifting a 350 lb tranny core assemble with a 1/16"
metal bracket though, Aaron? That does sound a little "whimpy" for
supporting that kind of weight.?

David Rieben


----- Original Message ----- From: "Tesla list" <<mailto:tesla@xxxxxxxxxx> tesla@xxxxxxxxxx>
To: <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx>
Sent: Tuesday, March 14, 2006 7:59 PM
Subject: Re: De-potting and re-potting a pole pig: Insulation concerns.


>Original poster: "J. Aaron Holmes" <<mailto:jaholmes@xxxxxxxxxxxxxxxxxx>jaholmes@xxxxxxxxxxxxxxxxxx>
>There you are, Dave! :-)  Well, that is encouraging.
>I have lifted a 15kVA unit from its can before, but
>this 25kVA unit is just plain scary.  I'm not worried
>about the lifting power of my hoist, but rather how to
>attach my hoist to it.  It does have a metal bracket
>strapped to the top of the core, but shockingly, it
>appears to only be about 1/16" thick!  I forget the
>exact figure, but I think the nameplate says the
>core+coil assembly weighs 350lbs.  I look at that,
>then at the wimpy metal bracket on top, and I think,
>"no WAY!"  ...but I could be wrong.  Perhaps I should
>take a picture and see what people think.
>I too have used nylon load binders to lift pole
>transformers.  I need to take another close look, but
>perhaps I can feed the nylon straps between the core
>and coils near the top of the transformer.  The core
>is two giant donuts side by side with a single large
>coil assembly the runs through the middle of each
>donut.  Kind of the opposite of the configuration of
>your transformer.  More like a big E-I core.
>Regards,
>Aaron, N7OE
>--- Tesla list <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx > wrote:
> > Original poster: Dave Leddon <<mailto:leddon1@xxxxxxxx>leddon1@xxxxxxxx>
> >
> > At 08:54 AM 3/14/2006, you wrote:
> > >Original poster: "J. Aaron Holmes"
> > <<mailto:jaholmes@xxxxxxxxxxxxxxxxxx>jaholmes@xxxxxxxxxxxxxxxxxx>
> > >
> > >I had long ago dreamed of creating my own version
> > of
> > >Dave Leddon's "Visible Pig" (don't know where those
> > >pictures of it are...Dave?), but the 15kVA unit I
> > >dragged from its can ended up being stripped down
> > and
> > >its core donated to ballast science :)  I now have
> > an
> > >old beater of a 15kVA unit (my workhorse) and a
> > newer
> > >25kVA unit.  The 25kVA unit has, I'm sad to say,
> > been
> > >unemployed since I acquired it a year ago, and only
> > >just this last weekend did I finally pop the lid to
> > >see what a modern 25kVA unit looked like inside.
> > It
> > >was really quite handsome, and got me re-interested
> > in
> > >the "Visible Pig" idea.
> >
> > Here's a picture
> > <http://nick_tesla.home.comcast.net/TheVisiblePig.jpg>http://nick_tesla.home.comcast.net/TheVisiblePig.jpg
> >
> >
> > >However I've managed to get myself a bit paranoid
> > now:
> > >  If I lift the thing out of oil (a big *if*
> > >considering I don't see any viable attach points on
> > >the thing), am I seriously compromising its
> > insulation
> > >by letting the oil drain away from the windings?
> >
> > I used a cheepo electric hoist purchased from Harbor
> > Freight that has
> > a 600-pound capacity
> > and a nylon motorcycle tie-down strap to lift the
> > transformer from
> > the can.  I just hooked the
> > two metal hooks on the strap under the edge of the
> > metal plate
> > attached to the top of the transformer
> > core and hoisted the thing out of the can.  The core
> > of a 10kva unit
> > only weighs about 160 pounds
> > so two people could probably accomplish the same
> > thing with a metal
> > bar slipped through the
> > strap.
> >
> > >What
> > >about the inevitable air bubbles what will become
> > >trapped under the thing when I lower it into its
> > new
> > >home?  Will they be problematic?  My gut tells me
> > that
> > >a few tiny air bubbles are probably no big deal
> > given
> > >the dimensions of the windings, but I have no
> > >experience to base this on.  I know that air
> > bubbles
> > >are "the end" for oil-filled capacitors...  What do
> > >you all think?  What do the transformer rebuild
> > places
> > >do?  Are the cans momentarily evacuated to get the
> > air
> > >bubbles out, or what?  Hmmm...
> >
> > On my first attempt to re-case the pig I pumped
> > compressed air into
> > the vent hole in the lid
> > and then released the pressure.  Each time I did
> > this a storm of
> > bubbles would stream out
> > of the transformer.  About the fourth time I did
> > this one of the
> > sides blew right out of the case,
> > releasing about 2 gallons of oil on to the floor.
> > On my second
> > attempt I decided to forgo any
> > use of positive or negative air pressure and just
> > let the transformer
> > set in the oil for several
> > days before applying full power.  I heated the oil
> > during this
> > soaking period to reduce its
> > viscosity by shorting the high-voltage terminals and
> > applying about
> > 200 watts of power to
> > the primary.
> >
> > There's probably still some air in there but I don't
> > think that this
> > is really an issue since the
> > oil-impregnated paper is the insulating medium.
> > I'll bet that Dr.
> > Resonance can offer
> > some insight on this topic since he has re-cased
> > dozens of transformers.
> >
> > Dave
> > Pleasanton, Ca
> >
> >
> >
> > >Best Regards,
> > >Aaron, N7OE
> >