I've seen three of these el-cheapo 12v impact wrenches.  Each of them
work the same way, and they don't require an inverter.  They use 12v
DC to spin a flywheel that engages the socket after they have spun-up
to whatever the manufacturer determines is full speed.  This has a
hammering effect that breaks the lug nut loose, sometimes with enough
force to remove it completely from the stud.  The first time I used
it, I thought it was broken :)

--
Michael Snow
1982 Westfalia 1.9TD
http://slowmachine82.blogspot.com/

On Sun, Nov 2, 2008 at 12:42 PM, neil N <musomuso@gmail.com> wrote:
> Hey neat. Didn't know they existed. Thanks for the tip.
>
> In light of what Courtenay is asking (120VAC have more power?) I'd be
> tempted to get one of those given I have an inverter in the Westy.
> (though I have no idea how much power a 120VAC unit would draw)
>
> Neil.
>
>
>
> On Sun, Nov 2, 2008 at 9:47 AM, Jim Cochran <mxsailor@gmail.com> wrote:
>> One of the most helpful items I keep in my cars is a 12 volt "emergency"
>> impact wrench. They sell for about $40 complete with sockets and extension.
>> If I get a flat, the wheel is off and on in no time. Also nice for removing
>> nuts from alternators & such.
>> Jim C
>>
>> On Nov 2, 2008, at 10:38 AM, neil N wrote:
>>
>>> I recall chewing up a lug nut REAL good a while back....
> ......
>>>
>>> If a socket still fits, might be worth taking it to someone with an air
>>> gun.
>