[TheForge] Air hammer

[Jerry Frost]

----- Original Message -----
From: "A. Vida" <osan@netlabs.net>
To: <theforge@mailman.qth.net>
Sent: Saturday, July 26, 2003 8:40 AM
Subject: Re: [TheForge] Air hammer


>
>
> Jerry Frost wrote:
> >
> > At first I was going to make it a down draw design like the Kickass. It
was
> > so compact and clean looking, about 5' tall and about 3 1/2' long. Then
a
> > list member I was bouncing ideas off of gave me a review of using a
Kickass.
> > He liked it fine except dirt, scale, etc. kept contaminating the rams
and
> > greatly slowed it down. I can also see increased wear to the seals and
> > piston rods.
>
> Reverse the cylinders, making it a MyAss hammer:
>
>
> Kick ass...                                 MyAss:
>
>

Kick My Ass Hammer? I already have a bunch of those, that's why I want a
power hammer. Wait! Being self contained, wouldn't it be a Kick it's Own Ass
Hammer? I'm startin to get dizzy Bro. <grin>

The main objection I have to reversing the cylinders is the plumbing. If the
cylinders are moving you have to use hose and allow enough excess length for
travel. I have three objections to this:

First is the extra volume of the hoses requiring a larger compressor piston
to make up for.

Second, hoses being flexible are less efficient.

Last but but my biggest objection is having several feet of hose flopping
around behind the ram just asking to be kissed by hot metal. I'd have to use
steal wrapped hose and it'd still take a beating from the work.

As I drew it up, the plumbing was only about 12" of 1 1/4" steel pipe per
side, not counting the bypass line which is about 10". The air would have a
short, smooth, rigid path in every direction, similar to a commercial self
contained hammer.

>
> Use a larger cylinder if you're concerned about the rods supporting the
> little bit of extra weight and of course, spread them out a bit more
> to provide sufficient clearance.
>

There wouldn't be any EXTRA weight, I'd just subtract it from the ram if I
thought it might be a problem. Besides the return (lift) stroke is the least
stressful. All in all if I could figure an easy way around the hose thing
the piston rods being under tension during impact would be preferable. In
fact the piston rods would be effectively isolated from the impact by the
air in the cylinder and take much less beating.

> Or shield the rods... perhaps something telescopic?
>

This thought is what's keeping the downdraw hammer on my drawing board. I
think a corrugated boot would be the easiest shield though contact with hot
work would still be a problem, though not nearly as inevitable as it would
be with flopping hoses.

> How about an oil bath, e.g.:
>

From 19 years experience on a drill rig I can attest to the fact that oil
attracts dirt, sticks it to sensitive parts and no kind of wiper will remove
it completely. The oil will effectively hydroplane the wiper out of contact
with the rod allowing the grit to pass where it will grind the seals away.

Instead I was considering a combination of boot and piston rod air vent
(flats machined in the piston rods near the top of the piston as in the
balance/makeup air valves on the compressor piston). The boot would keep the
worst of the debris away and the piston rod vent would keep the boot under
positive pressure, making sure even the finest grit didn't get through.

> --
> -Andy V.
>

Good thoughts Andy.

Thanks

Frosty
------------------------
If it ain't forged
it ain't real.
Wrought iron is.
The FrostWorks

Meadow Lakes, AK.