[TheForge] Re: Air hammer valves

[Mike Spencer]

darrell> If I am seeing it right, both reed valves are in a common
darrell> chamber to double the air flow capacity. With one missing,
darrell> the air can go both ways instead of
darrell> being a one way flow.

Summary: The two reeds permit air flow in opposite directions.

You're not seeing it right -- my fault because I didn't label
photo adequately or describe the parts fully.  Worse, part of what I
wrote here on the list was false!

If you look again at the detail photo showing the reed valve, (is that
the right term?) there are two hex bolts holding the spring (which
retains the reed) and the reed itself.  There are also 4 larger hex
bolt heads.  Those larger bolts hold an approx. 1" thick plate to the
main valve body.  One reed spring you can see (labeled "Flap valve
spring") attached to the visible side of that plate.  The other reed
is missing but CONTRARY TO WHAT I WROTE earlier, the bowed spring and
bolts are there, on the OPPOSITE SIDE of the 1" plate.  That's where
it was and that's where the wear marks indicate it always was.  The
missing reed covered the two rectangular ports that you can see in the
photo just under the visible (and labeled) spring but on the opposite
side of the plate from the spring visible in the photo.

So the two reeds permit air flow in opposite directions through the 1"
plate. 

Only the thin reed is missing from the other side of the plate, but
all of it is missing, i.e. there was no broken-off stub under the
bolts indicating that a piece had come off in operation and been
sucked into the works somewhere.  

On the other hand, one of the bolts for the missing reed is
mismatched.  That suggests to me that the reed and its spring *may*
have come off in service and that one of the bolts (and maybe the reed
itself) got sucked into the works somewhere.  Or maybe they just
dropped that bolt in the mud while removing the reed for some purpose.
Who knows?  (What do you call this kind of thing? Forensic
millwrighting?  Industrial archaeology? :-)


And yes, one end of the reed is held by the bolts but the other is
free, retained only by the pressure of the relatively heavy, bowed
spring.


- Mike

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