1/12 Apollo Command Module

micahrogers

micahrogers

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ennder said:
Most of the design work I did required a tolerance of +or - of .005. There was a few things that the customer required +- of .0025
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1/2" medical gas tubing, made from anhydrous copper, once you break the seal on a 50' roll, you have 48 hours to use it, or scrap it, because the water vapor in the air starts to degrade it. 1/2" nominal OD, minimum wall thickness of .062, max wall thickness of .065. talk about easy to crush...

but my caliper only needed .001 scale, not .0001 or better.
 
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micahrogers said:
1/2" medical gas tubing, made from anhydrous copper, once you break the seal on a 50' roll, you have 48 hours to use it, or scrap it, because the water vapor in the air starts to degrade it. 1/2" nominal OD, minimum wall thickness of .062, max wall thickness of .065. talk about easy to crush...

but my caliper only needed .001 scale, not .0001 or better.
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I know guys who used to pump that stuff full or Argon gas, leaving one end with a pinhole, and then solder the both ends closed with solder, to get more life out of the tubing roll. don't know if that was Kosher. I never got into fixing Medical Grade electronics, as some of the requirements were a bit over done, but then again, a person's life may depend on it, or may not, sometimes I wondered if copper degraded that quickly, then use something that doesn't. Many of the Med Techs I talked too said it was to jack up the prices and service, planned obsolescence. I'm not an engineer, so I don't really know.

My recumbent Trike has a wall thickness of .050" but it's 2" inches on the O.D.. The larger O.D. gives the strength. I knew a guy who made world class hand made racing bicycles out of Chrome Moly tubing is they are only .010" of an inch thick!! Frank Strnad was his name. His passed Set. 2019, an true gentleman. I truly could not say enough good things about him. He was selling his miller Econotig Tig Welder for $1000 bucks, but when he found out I wanted it, he gave it to me for $300 bucks, with wand and foot pedal!! I was shocked. He wanted me to have it. It is so new, he built only 60 bicycle frames one i but needed something that could go lower than .015" of inch thinner. Every bike he made was measured to the person buying it, and made to order. People came from all over the world. His bikes et a pretty penny but you never see them for sale. Of the 2 pics below, the blue one is the last bike he made, and the Carbon Fiber one is one of his also. He used the finest components and laced all his rims. All frames, as I wrote earlier, were built to spec, and you had to come in to be measured on a jig he built.:)

Last Strnad.jpg

Strnad.jpg
 
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micahrogers

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The primary concern with med gas is a clean environment to start with. I never used argon, but I flushed with purged all my jobs with helium, and vacuumed it off before sealing for final delivery. The way the concern was explained to me by a chemical engineer, is that certain compounds, which can be in normal air, combust spontaneously in the presence of pressurized oxygen. Hydrogen being one, thus anhydrous copper. some pipe sealants contain chemicals which explode in contact with oxygen, some soldering and brazing fluxes contain these as well. I always silver soldered or 25% silver brazed med gas.
 
Kolokolnikov

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mijob said:
Woe this is looking fantastic. Smart move to solder the wires. :Drinks:
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In this case, I glue the back side with glue so that the wire does not fall inward, since I had to make 0.45 mm holes, due to the fact that it is very difficult to get into the 0.3 mm hole fitted to the diameter of the wire during weaving.
 
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