[TheForge] Air hammer return stroke

Sat Feb 1 13:05:02 2003

Morning Steve:

I'm hoping this will take my mind off the smoking contrails of Columbia's
wreckage on TV. Perhaps this will ease the numbness.

As already mentioned, an air cushion at either end of the ram cylinder's
stroke is what I'm going to use. It's easier and "safer" than a mechanical
stop.

How I'm going to do it is make the stroke of the compressor piston shorter
than the ram piston so the compressor piston reverses stroke before the ram
piston tops/bottoms out.

I would NOT use a spring. Fatigue could cause it to fail without warning and
while I seriously doubt anybody would get hurt, the damage to the hammer
could be catastrophic.

A rubber cushion would be safer but taking the kind of impacts it will,
would probably degrade and fail pretty quickly.

I've looked through half a dozen drawings of hammers on the patent servers
and have not seen a mechanical ram stop on one. They all appear to be air or
hydraulic fluid cushioned/reversed. So far, the simplest hammer design I've
seen is the Bates Hammer.

Something to consider as has been mentioned is excess air. Short stroking
the compressor piston is going to spike the air pressure. Overpressuring the
thing is easy to handle with a set of pressure relief valves. Looking at the
drawings you see them in every one, usually in the valves. Putting relief
valves in the spool valves I'm playing with was problematical on paper. They
were causing me to include a bunch more ports and lines so I moved them to
the source. On paper anyway.

I've sketched in two relief valves through the compressor piston itself. No
extra lines. Don't know if it'll work though. <grin>

I will post sketches as soon as I get a scanner operating, I was going to
use my wife's but her computer's dead. We're taking it in to our favorite
computer geek today. <sigh>

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

Meadow Lakes, AK.

----- Original Message -----
From: "Steve Smith" <[email protected]>
To: "theforge" <[email protected]>
Sent: Friday, January 31, 2003 5:08 PM
Subject: [TheForge] Air hammer return stroke

> So I'm still working on a self contained air hammer, although my
> question applies to other hammers as well.
>
> When the ram is on the return, headed upward, it reaches a hard stop so
> that the air cylinder doesn't bung itself up. I'm trying to figure how
> to cushion the hard stop.
>
> A spring seems like a good idea. Unfortunately, there is quite a bit of
> energy to absorb. If I did it right, I could do it with a stack of
> Belleville spring discs. This would run about $50 buying them from MSC.
> I sized them based on stopping the hammer in less than 1" travel (which
> makes for a lot of spring washers). The rod on the cylinder that the
> discs would go around is 1 1/8" diameter. A large coil spring would also
> work, but I don't have a source for one.
>
> Any other suggestions out there?
>
> Thanks,
> Steve Smith
>
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