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Another English/Metric "Spacecraft" Problem

Posted by Hemos on from the oh-the-joys-of-system-management dept.

SuperDry writes "There's been another spacecraft failure that's been attributed to an English/Metric units problem, this time at Tokyo Disneyland's Space Mountain. An axle broke on a "spacecraft" (a.k.a. roller coaster train) mid-ride, causing it to derail (nobody was hurt). The final investigation report has been released, and the root cause has been determined to be a part being the wrong size due to a conversion of the master plans in 1995 from English units to Metric units. In 2002, new axles were mistakenly ordered using the pre-1995 English specifications instead of the current Metric specifications. Apparently size does matter, even if it's only a 0.86mm difference."

4 of 748 comments (clear)

  1. Miscommunication by Anonymous Coward · · Score: 5, Informative

    From the Article:

    In September 1995, the design specifications for the size of the axle bearing for Space Mountain vehicles was changed from inches to the metric scale. Accordingly, the axle diameter was also changed, in this case from 44.14 mm to 45.00 mm. However, appropriate action to revise and maintain the design drawings was neglected. Consequently, two different drawings existed within our company after the changes were made and the old drawing showing the 44.14 mm diameter was used to order (in August 2002) the axles that were delivered in October 2002.

    They actually changed the specs. The conversions were all done correctly but they failed to update everyone.

  2. 0.86mm? That's a HUGE difference! by cnelzie · · Score: 5, Informative

    In the automotive industry being off by that 'gigantic' mile of a discrepancy can be the difference between an entirely safe system or a potentially dangerous event just waiting to happen.

    Anything from rubbing away the lining of important wires or hoses, different stress locations resulting in tear apart pieces that shouldn't be tear apart can happen by being off by that much...

    0.86mm might at well be 3 feet off. A part that comes out that far off is nothing but scrap material. (Well at least in our area of automotive work.)

    --
    If you ignore the other uses of a tool, does that make the tool less useful, or you less useful?
  3. It had nothing to do with the conversion directly. by bluprint · · Score: 5, Informative

    If you had read the article, you would know that the problem was, while converting to metric, they also changed the specification of the axle size, but didn't record the new axle size correctly. So, the problem really had nothing to do with any mathematical error, just an error in incorrect documentation.

    --
    A modern day witchhunt.
  4. The Japanese did the conversion. by mookoz · · Score: 5, Informative
    Bob Gurr (ex-Disney Imagineer) tells the story of the Tokyo Disneyland conversion here:

    http://www.laughingplace.com/News-ID108300.asp

    Great set of columns, by the way. I've always been a fan of how some of the disney technology was invented and implemented.