Text 22032, 147 rader
Skriven 2012-03-04 17:26:22 av HAP NEWSOM (1:123/140)
     Kommentar till en text av GLEN JAMIESON
Ärende: SILENT SERVICE 20304
============================
Gidday Glen!
-> 
->  ->  -> camera was made of fibreglass, took 75 mm film, weighed 1/3 lb 
and
->  ->  -> took high quality pictures (one at a loading) from an altitude
of
-> 
->  ->  -> carried in a nylon dart that was launched, almost silently, from 
a
->  ->  -> foot-pumped compressed air gun.  My job was designing the gun, 
the
->  ->  -> dart, timer and camera actuator.  Others did the camera, which 
was
->  ->  -> designed to take launch and landing accelerations of 1000g.
->  ->  ->
->  -> The camera was loaded in a light-proof box by feel.  A pre-cut film
->  -> 125mm x 75mm was slipped into the curved detachable back, which was
->  -> clipped onto the camera body, and the lens swung to the "ready"
->  -> position.  One of the most difficult problems was light-proofing the
->  -> fibreglass body.
->  -> 
->  HN> Would be very interesting to see
->  HN> photos of the contraption! And
->  HN> it sounds like it was fun to use!!
-> 
-> I don't have any photos, as we were not allowed to take cameras to
-> work.  (Only allowed to make them at work!)
->
Yeah, I know how that goes...you could
make a newer version of it and sell it
to photographers!

-> Picture a spherical aluminium pressure tank (using Imperial units,
-> which is what we had at that time, long ago) about 10" diameter, with
-> a yard long, 4 1/2" diameter nylon tube (made by spirally wrapping
-> strips of nylon sheet around a former, glued with a resorcinol solvent
-> glue).  The base of the pressure tank sat in a base similar to that
-> used on modern computer monitors so that the launch angle could be
-> adjusted.  The foot operated air pump, also of aluminium, was hinged
-> to the base so it could be folded up for easy carrying.  The dart,
-> also made of nylon, comprised a cylinder into which the camera was
-> placed, above it a conical pressure tank charged by the launch air
-> through a rubber flap valve, and above that, the telescopic shock
-> absorber.  The launch trigger was a small button on the side of the
-> tank.  No electrical stuff anywhere in the system.
->  
->  ->  HN> Sounds interesting too! I would have liked
->  ->  HN> to have seen the launching system and 
->  ->  HN> design for the "projectile"...would be
->  ->  HN> fun to do even today!
-> 
-> The original idea came from an old man who made his own wooden camera,
-> stuck it on a wooden dart launched by big rubber bands, and took
-> aerial photos of his neighbours' back yards.  He used a string to spin
-> up his gyro stabiliser before launch.  We greatly refined the idea.
->
Hmmm was he looking for lady sunbathers??
 
->  -> My launcher used foot-pumped compressed air stored at 120 psi in a
->  -> spherical aluminium tank surrounding the quick-opening valve 
mechanism
->  -> which allowed the pressure to be instantly dumped under the nylon
->  -> dart, about 120mm diameter, which fired it out of the metre-long
->  -> nylon barrel.  As the propelling air was expanded almost down to
->  -> atmospheric pressure by the time the dart left the barrel, there was
->  -> practically no noise, which was one of the design requirements.
->  ->
->  HN> How long did it take for you to 
->  HN> pump it up to 120psi? and how
->  HN> much volume are we talking about
->  HN> with the tank??
-> 
-> I think it was only about 2 minutes to pump up the tank.  Enough
-> volume to expand it almost down to atmospheric pressure by the time
-> the dart left the barrel.  Not much.  I was particularly proud of the
-> very light quick-opening valve that dumped the whole of the compressed
-> air store into the space beneath the dart in about a millisecond.
->
Two minutes is not bad at all!
  
->  -> A portion of that high pressure air was stored in a space within the
->  -> dart, and slowly leaked out through an adjustable needle valve.  At
a
->  -> pre-set pressure, the remaining air was dumped into an actuator
which
->  -> released the camera "shutter".  This was usually set to occur just
->  -> before apogee, while the dart was still rising vertically.
->  ->
->  HN> Sounds quite complicated!!
-> 
-> Not really.  We had one of the best tool-making workshops in
-> Australia, with very skilled tradesmen.  They spun the spherical tank
-> from aluminium sheet, then aluminium brazed the barrel supporting
-> components into it. I did the original designs, assembly and testing.
->
->  -> To prevent the dart from rolling during its upward flight, I used a
->  -> vane with a tiny gyroscope, similar to that used by the US
Sidewinder
->  -> missile. The gyro was spun up by a swinging weight during launch.
->  -> Amazingly, everything worked!
-> 
->  HN> Very interesting...I'm 
->  HN> surprised you did not use
->  HN> some sort of accelerometer
->  HN> and gyro combo!
-> 
-> The engineers working on the project were both mechanical, so all
-> components were simple mechanical.  :) To measure launch and landing
-> accelerations I used bits of resin-cored solder of different lengths,
-> which bent or didn't bend.
->
Now you could do it with miniature
electronics and a small battery.
 
-> For a pressure gauge I used a spring-loaded plunger type, similar to a
-> tyre gauge, but calibrated in feet to give the height at which the
-> photo would be taken.  For lower height, lower pressure, and that
-> automatically set the shutter release timer earlier.
->  
->  -> After that, my next project was a super-efficient air-launched
->  -> submarine detection sonar buoy...  Nothing like variety!
->  -> 
->  HN> Ok...now that's just WRONG!!!(grin)
-> 
-> That entailed going down in a one-man capsule towed by a work boat,
-> with its depth controlled by paravanes worked by 2 handwheels inside.
-> Once I got the hang of it, control was easy, and I could skate along,
-> just clear of the seabed, banking to one side or another.
-> After work the boat master/owner sometimes dived down and caught
-> scallops for us to eat.  They were delicious, with a little white
-> wine, which I often happened to have with me.
->
Now why am I not surprised at that?
(grin)...I like scallops!
 
-> And so the defence of Australia was kept in good hands.
-> 
->  HN> BTW I have a new friend in Oz..she's
->  HN> a medic on a collins class sub out of HN> Sydney!
-> 
-> I sympathise with her.  Those subs have been notorious for faults.
->
Boy are they ever! 
chat with you soon!
ha
--- Platinum Xpress/Win/WINServer v3.0pr5
 * Origin: Since 1991 And Were Still Here! DOCSPLACE.TZO.COM (1:123/140)