[GreenKeys] Model 15 Noise Suppression

[John Nagle]

On 8/13/2011 2:47 PM, greenkeys-request at mailman.qth.net wrote:
> Hi All:
>
> This server seems to be very picky on what titles are
> passed along to the list. Once again, I am having to re-
> post a message to the list because it appears not to like a
> title. (It was: Sound Deadening Blanket or foam...) I will
> be this title gets posted immediately...
>
> Still doing a bit of work on my model 15....
>
> The sound deadenting blanket inside the cover is coming
> apart, a result of the 80 years since it was made...
>
> I am wondering if anyone knows of a source for either new
> blanket material, or a black high density foam which could
> be used to replace it?
>
> Dave

     You can get both acoustic mat that's close to the original,
or adhesive sound deadening material as used in cars.

     I had to address this issue for the Model 15 I use at
steampunk conventions. We'd had complaints about the noise
level, and I had to take steps to deal with it.

     I've built my own brass and glass case, of course,
which you can see at

     http://www.aetherltd.com/deployment.html

I'm exposing more of the machinery than the standard case
does, so I have to take extra effort to get the noise down.

     The first step was to get the machine up on rubber
Lord mounts, as on a standard Teletype table.  The
bolts that attach the Teletype to the Lord mounts are
3/8-28, which is not a modern standard bolt.  So I purchased
the appropriate die, cut and threaded a longer bolt, and
mounted the machine to a newly built base.  See

http://mailman.qth.net/pipermail/greenkeys/2009-December/015685.html

for details on the die required.

     Proper lubrication is important.  If anything is louder than
the typebars hitting the paper, something is wrong.  Idling,
the machine should be almost silent.  Properly
adjusted and lubricated, a Model 15 should just purr.
Following those six pages of lubrication directions in the Adjustments
manual works.

     The carriage return dashpot may need adjustment.  If there's a
noticeable "bang" on carriage return, that can be fixed.  This is
covered in the adjustments manual.

     As with the standard case, my case touches the frame only at
the rubber bumpers on the side of the Model 15.  The usual
Model 15 setup has a felt pad under the machine.  I'm not using
that.  My case touches the base only on cork pads at the corners.
This keeps the case from amplifying vibration.  The inside of the
new case was lined with automotive noise isolating foam.

     I turned down the typebar impact force to the lowest level.
The standard setting seems to be designed for multipart carbons.
If dashes are punching through the paper or ribbon, the typebar
impact force is too high.

     Finally, at shows, we set down a layer of indoor-outdoor
carpet on the table, then put a green table drape over it.
The machine goes on top of that.   The carpeting helps
to absorb the carriage return energy, keeping the table
from creaking.

     The end result can be seen in the video at the end of

	http://www.aetherltd.com/refurbishing15.html

Note that the noise level from the machine, at six feet,
is below the ambient conversation level in a busy room.

     This seems like a lot of work, but we've run two machines
for three days in a busy room without complaints.

				John Nagle