[TheForge] Re: Air hammer score

[Mike Spencer]

Yow!  Advice by overnight express! :-)

From Ralph:

> I have one suggestion is that you have to use a larger engine HP
> than the electric one on it.

Yeah.  I knew there was some kind of thing like that but don't know
any of the engineering or even rules of thumb.  The ex works machine
has a 15 HP, 60 Hz motor made in Canada for the Brit hammer.  The
motor has a small gear on it that drives a big gear wheel on the
hammer's integral compressor.  Pretty efficient drive.  The hammer I'm
trading away is flat-belt and tensioner pulley (instead of a clutch) so
I know from experience it's not a very efficient way to go.  The idea
of using the 10HP make 'n break is just because I happen to have it.
It's got lots of torque and runs at about the right speed so's not to
need intermediate line-shafting.

> If you have a 1HP elect.......I believe it is only 2/3 of a
> mechanical HP in power supplied.

Do you mean that an electric motor rated for 1HP only delivers 2/3 HP
as measured by, say, a brake HP measuring thingy?  That should mean
that 10HP delivered to the shaft would be adequate.  My (very vague)
recollection is that electric motor HP is rated by the electric power
delivered *to* the motor so that what's output by the motor, as
measured by something like torque X RPM is less.  Could you go into
more detail on that?


Since I'm building a new shop at home, I'm going to pour the pad for
the hammer outside at the same time.  It'll be easy enough to move the
gas engine to a temporary mount and try it.  I talked to the manager
of Acadia Gas back before they were borged by a more modern company
and were still making these has engines.  He said they actually
delivered 11+ HP.

(Putting the hammer outside initially is just caution.  If I were to
build the shop around it, I wouldn't have head room to lift the ram out
if that proves necessary.  Worse, if I can't get it going at all, I'd
almost have to tear the building down to get it out again.  If I can
get it working outside, I'll just stick a shed on the side of the
shop.  I'm framing a 10' piece of the wall ahead of time specially to
make a 10' opening there easy later if needed.)

And  Shannel said:

> What about a rotary phase converter and a cheap, second hand 3 phase
> motor, you can build your own phase converter for not a lot of
> dough.

Well, I guess that's a possibility.  The original motor and its very
heavy mount bolt directly to the hammer base, a very (!) sturdy
assembly, presumably because of the stresses on the ca. 6" -> 24" gear
drive.  The motor shaft and castings are okay and I think I could get
it rewound by a friend whose little backyard electric biz has grown up
to be a major player in the local industrial park.  Sometime later
this year I may be back, asking for pointers to how to do home-made
converters.  I want to try the funky alternatives first and, if that
doesn't work, I'll have to look through all the posts to TheForge that
I've saved.  I know this 3ph converter stuff has gone by before.


All very exciting but rather intimidating.

- Mike

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Michael Spencer                  Nova Scotia, Canada 
                                 
http://home.tallships.ca/mspencer/