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Thread: The OT thread V1

  1. #2851
    Insider PBSteve's Avatar
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    Edit: Just reread the paper, I was wrong. It's Rrms (rms?).

    Precise machining of the 0.5 ± 0.05-mm wall thickness and the requirements for flatness within 50 microns over the 3.4m length required the development of special fixtures and technology to produce 40 of these chambers.

    A special cleaning procedure after the abrasive flow polishing was developed to achieve minimal residual outgassing. Welding of the end bi-metal flanges, the baking procedure, and quality assurance tests to ensure proper chamber quality will be presented as well.

    The Linac Coherent Light Source (LCLS) extruded vacuum chamber is a transport pipe for an electron beam and its induced synchrotron radiation. Physics specifications required a vertical beam aperture of nominally 5 mm with a maximum allowable overall chamber height of 6 mm thus a very thin 0.5 mm wall. The internal surface finish requirement was between 200-150 nm (RMS) along the extrusion direction to minimize interactions with the particle beam. Taking into account that the pole gap for the LCLS undulator is 6.8 mm, the chamber external surface should be machined to a flatness better then 50 microns along the entire chamber length of 3.4 meters. The major challenges to produce an extruded vacuum chamber meeting these requirements were: 1. One has to be positive that an extrusion machined to a wall thickness 0.5 mm or even slightly less (due to manufacturing tolerances), will be vacuum tight. 2. From previous experience, the aperture surface finish inside the extrusion would be 800-1000 nm along the extrusion direction. It was necessary to find a way to improve surface the finish dramatically. 3. Wall thickness tolerance and vacuum chamber flatness has to be much better than previously achieved.
    LCLS EXTRUDED ALUMINUM VACUUM CHAMBER - NEW APPROACHES (PDF Download Available). Available from: https://www.researchgate.net/publica...NEW_APPROACHES [accessed Dec 21 2017].

    Keep in mind that 0.5mm wall thickness is under ultra-high vacuum.
    Last edited by PBSteve; 12-22-2017 at 12:41 AM.
    Ever so many citizens of this republic think they ought to believe that the Universe is a monarchy, and therefore they are always at odds with the republic. -Alan Watts

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  2. #2852
    I dislike the term "rms" because you can have all sorts of things Vrms, Arms, RMS is simply a mathematical transformation, not necessarily a surface finish measurement.
    social conservatism: the mortal fear that someone, somewhere, might be having fun.

  3. #2853
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    The RMS value for roughness is reported as Rq (At least from our in house lab) maybe that's your preference? Idk what metrologists do. I think we're all aware of "root mean square" mathematically.

    https://en.wikipedia.org/wiki/Surface_roughness

    What's interesting is they don't have "Swedish height" which is the 10%-90% histogram interval on height. For some reason our Zygo interferometer reports that and for my undisclosable purposes it has a better correlation than Rq to fitness for use (probably the inherent noise reduction in taking only the middle range samples?)

    - - - Updated - - -

    LCLS looks pretty goddamn cool
    "So you've done this before?"
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  4. #2854
    in the continuing saga of why street cars make poor race cars: http://www.vtec.net/news/news-item?news_item_id=1329332
    social conservatism: the mortal fear that someone, somewhere, might be having fun.

  5. #2855
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    Funny, I just had this discussion about the Focus RS elsewhere. There's zero chance I'd ever recommend someone come into my dealership and buy a Focus RS specifically to go race bone stock. They're just not designed for it, and we've gone over that here, too. They look the part, and they're closer to a track car than a Focus SE/SEL/Titanium, but they're not a race car. If they're used within the limits they're designed for, then they're pretty stout.

    I did just have a chat with a coworker that we'd love to see NASCAR have to meet street car templates. Not saying take the Fusion off our showroom floor and run it at Daytona, but the race car should match the street car.

  6. #2856
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    No, no it shouldn't. They can't even efficiently market enthusiast cars with broader appeal than that. There's very very little incentive to couple the design tensions of a production car and that of a dedicated race car.

    "Chase 2 rabbits, and both escape."
    "So you've done this before?"
    "Oh, hell no. But I think it's gonna work."

  7. #2857
    the marketing of the type R is distinctively more track focused than the RS. its far closer to the marketing supporting the z06, another "track car for the street" (hint: it isn't)


    as far as production based racing, thats what GTE/3/4 is.

    ford has a good presence in both GTE (with the ford GT-E) and in GT4, with the mustang:



    these cars and this type of production based racing exists .... just everyone thinks racing is indy car, nascar or f1 ....

    GT4 cars are legal for Pirrelli world challenege GTS class, and the now Michelin sponsored IMSA GS class. both series provide some EXCELLENT multi-make, production based racing: https://www.youtube.com/watch?v=lyw_eLcRV38&t=7114s
    Last edited by cockerpunk; 12-27-2017 at 10:52 AM.
    social conservatism: the mortal fear that someone, somewhere, might be having fun.

  8. #2858
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    http://www.daniclodedesign.com/thethirdthumb

    This, with some of Ed Boyden's research could be awesome in a few years.

  9. #2859
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    Gattaca did it better.

    Edit:

    https://www.youtube.com/watch?v=rUOlnvGpcbs
    Last edited by Lurker27; 12-28-2017 at 12:19 PM.
    "So you've done this before?"
    "Oh, hell no. But I think it's gonna work."

  10. #2860
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