[GreenKeys] 32/33 print hammer
Bob Camp
Bob Camp <[email protected]>
Sun, 24 Aug 2003 21:47:25 -0400
Hi
So it sounds like we need a solution that's a little more complex than a
simple disk.
Here's a question - what did they make the original parts out of? I have
never seen neoprene do what these hammers do over time. The rubber on the
hammers started dying pretty fast as I recall. They were one of the things
that got changed out on a regular basis when the machines were new.
Did they use something that was extra soft to protect the print heads or
something that damped vibration to take care of double hits on impact. Most
of the vibration damping stuff is kind of sponge like. I can see how it
would die fairly fast.
Take Care!
Bob Camp
KB8TQ
----- Original Message -----
From: "gil smith" <[email protected]>
To: <[email protected]>
Sent: Sunday, August 24, 2003 5:21 PM
Subject: Re: [GreenKeys] 32/33 print hammer
> Folks:
>
> A correction to my earlier post. I just dug out a bag of 33 parts, and
> found an NOS hammer. It is very soft now. The diameter is pretty darn
> close to 0.5", and the outside edge measures about 0.18". However, it
> designed to snap around a disc for retention, so the center is only about
> 0.085" thick. Well, that is the best I can tell, according to my
> micrometer sloppily oozing into goo that was once useful rubber.
>
> Unless we find someone with an end mill to burrow a hole into the rubber
> (if rubber can be milled at all), we are left with applying a flat sheet
> for hammer replacements. Which, as best I can tell, should be about
0.085"
> thick.
>
> So I went to pull off the old hammer on the 33, which I thought had
> hardened, judging by the cracks around the edge. It was actually soft goo
> as well. But I could see, well, feel, the raised disc that the hammer
> snaps over, for retention. It is flat on top, so the hammer would glue
> onto it directly. I suppose if the glue oozed around the mounting disc,
it
> would add a bit of lateral retention as well.
>
> Robert Downs seems to know the materials science end of this elastomeric
> mystery. If you guys find an appropriate sheet rubber source and
adhesive,
> I'd be happy to punch them out.
>
> gil
>
>
> At 01:08 pm 8/24/03, Bob Camp wrote:
> >Hi
> >
> >Half inch diameter sounds easy to hit with fairly simple stuff. I suspect
> >that something near 0.2 inch thick is a standard sheet thickness.
> >
> >Is the original part flat on both sides or is there a retaining bump on
the
> >back of the part?
> >
> >My recollection of the original rubber used was that it came fairly close
to
> >an eraser on the end of a pencil. It was a little softer, but not by a
lot.
> >Of course that's based on a quick observation 20+ years ago. I may be way
> >off ....
> >
> >The main idea about the punch was to make it quick to run off a bunch of
> >them. One person could probably wack out a lifetime supply for everybody
on
> >the list in a few hours. Postage to distribute them would cost more than
the
> >material and the time.
> >
> > Enjoy!
> >
> > Bob Camp
> > KB8TQ
> >
> >
> >----- Original Message -----
> >From: "gil smith" <[email protected]>
> >To: "Bob Camp" <[email protected]>
> >Cc: <[email protected]>
> >Sent: Sunday, August 24, 2003 3:47 PM
> >Subject: Re: [GreenKeys] 32/33 print hammer
> >
> >
> > > Hi folks:
> > >
> > > My quick measurement of a 33 hammer shows it to be about 0.5" dia by
0.2"
> > > thick.
> > >
> > > I like Don's idea of using the peel-n-stick bumpers -- I have some 3M
> > > bumpers from DigiKey (#SJ5012-0), that measure about 0.5" dia by 0.15"
> > > thick. Dunno if slightly thinner is a problem or not. The rubber
seems
> > > kinda soft -- anyone know what the original rubber was like? The
original
> > > one in my machine is rather hard with age. Bet this bumper would work
> > > though, even if it needs a small shim to make it thicker. The big
> >question
> > > would be the bumper's adhesive.
> > >
> > > If someone finds a rubber sheet that is appropriate, you probably
don't
> > > need to punch it into a nice circle. I'd bet that hacking it to an
> >octagon
> > > with an xacto knife would suffice. Though I do have a bench punch
with a
> > > 0.5" die set if anyone wants a bunch made. I have some 3M 467 sheet
> > > adhesive that could be applied before punching; then you just peel
off
> >the
> > > paper backing and apply the new hammer pad. 467 is a pretty good
> >adhesive,
> > > but, as mentioned previously, how it stands up in heat and oil is a
good
> > > question.
> > >
> > > Before mounting the bumper, you would want to clean the hammer
mounting
> > > plate with something like lacquer thinner, to remove all oil.
> > >
> > > gil
> > >
> > >
> > > At 11:12 am 8/24/03, Bob Camp wrote:
> > > >Hi,
> > > >
> > > >One fairly simple thought:
> > > >
> > > >Sheet rubber is a common item. You can get all sorts of compositions
and
> > > >thicknesses fairly easily. Last time I went shopping there were
several
> > > >local suppliers. They would sell you a couple of square yards of
stuff
> > > >without any real hassle. The question always is which rubber to use.
> >Again
> > > >there are zillions of different compositions.
> > > >
> > > >Once you have the raw material you need a punch to blast out the
print
> > > >hammers. Last time I looked at one (gulp .... *several* years ago)
they
> > > >looked like a round disk without any real fancy stuff associated with
it.
> > > >Don't remember if they had a little nubbin on the back side of them
or
> >not.
> > > >
> > > >Even if it's a punch you can't buy at the leather working counter
down at
> > > >Hobby Lobby a rubber punch is not to hard to make.
> > > >
> > > >Given the punch and the raw material making a couple hundred
imitation
> >print
> > > >hammer pads shouldn't take more than an hour or two.
> > > >
> > > >The questions:
> > > >
> > > >What are the dimensions of a "real" print hammer pad?
> > > >
> > > >What's the right material to use (need one that's soft enough and
holds
> >up
> > > >to heat and oil) ?
> > > >
> > > >Given that information the rest *should* be fairly easy.
> > > >
> > > > Enjoy!
> > > >
> > > > Bob Camp
> > > > KB8TQ
> > > >
> > > >
> > > >
> > > >----- Original Message -----
> > > >From: <[email protected]>
> > > >To: <[email protected]>
> > > >Sent: Saturday, August 23, 2003 6:53 PM
> > > >Subject: [GreenKeys] print hammer
> > > >
> > > >
> > > > > What i need are suggestions as to what material to use and what
type
> >glue
> > > >to use to make a print hammer for my Model 32. It is my understanding
> >that
> > > >print hammers are not availiable as they all turned to mush.I no
longer
> >like
> > > >the idea of my model 32 just sitting here idle because of a little
round
> > > >peice of rubber.Shurly someone out there has solved this problem and
got
> > > >their machine back into service.Wayne WB0CTE
> > > > >
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