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Two bike designers ahead of their times

Concept 9 992

I first saw the news on Bike Biz that engineer and inventor Dr. Alex Moulton passed away this week at the age of 92. For any of you who aren’t familiar with his work, Dr. Moulton pioneered the small wheel bicycle in the early 1960s with the launch of his first full suspension bicycles.  He was a true innovator who chose to look beyond the way things were traditionally done in order to create what he considered a better bike. As the Bike Biz article points out, “In the late 1950s, Dr Moulton’s design ideas were at odds with the accepted norms of the cycle industry. His development activities extended to construction methods and, whilst many of these are commonplace nowadays, the large section tube, extensive use of pressings and lugless construction of the original Moulton bicycles were revolutionary in 1962.”

In addition to the Bike Biz piece, I noticed nice tributes to Dr. Moulton at Dezeen, TreeHugger, and many other places on the web. He may be gone, but he definitely left his mark.

The Invincible by J.S. Smith. Image credit: Carlton Reid

About seventy years before Moulton debuted his first bike, J. S. Smith, proprietor of the Surrey Machinist Co. in London, created the Invincible, a clean looking bike which featured monoblades front and rear. Carlton Reid has a great piece on his “Roads Were Not Built for Cars“ blog about Smith’s late 19th century bike, which inspired later designs like the Mike Burrows designed Lotus Type 108 pursuit bike that was ridden by Chris Boardman in the 1992 Olympics (one of my personal favorite bike designs of all time).  See additional pictures of the Invincible at Carlton’s post and in his Flickr stream. Like the original Moultons, it was a beautiful bike that influenced many of the designs that we are familiar with today.

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  1. Androo December 11, 2012 at 4:11 pm -  Reply

    I love that Invincible. Hadn’t seen it before.

    I really do think that mono-stays are an idea that deserve their day in the sun on bicycles once again. Stiffer, lighter, more aerodynamic, and much easier to change tires as an added practical benefit.

    • art December 12, 2012 at 11:58 am -  Reply

      I get the aerodynamics and ease of tire changes, but I can’t see how a monostay can increase stiffness without a significant weight penalty.

      • Androo December 12, 2012 at 5:29 pm -  Reply

        The bending stress in a tube is proportional to its diameter and its area moment of inertia (really just a way of describing the distribution of material in its cross-section). That moment of inertia (I) involves the 4th power, so a round 1.0″ x 0.035″ wall tube will have an I of 0.0123, while a 1.5″ x 0.035″ tube will have an I of 0.0432 (nearly 4 times larger).

        At the same time, that 1.0″ tube will have a cross-sectional area of 0.1061 in^2, whereas the 1.5″ tube is just 0.1611 in^2.

        So while the 1.5″ tube will be much stiffer – 2.33x less bending stress – in this example, it is only 1.52x heavier, so the stiffness/weight is 1.54x higher. This effect gets more pronounced if you decrease the wall thickness of the tube as you get larger (within limits, eventually you get into buckling issues when your diameter/wall thickness ratio is greater than about 50).

        Obviously you need to do other stress analysis, like torsional stiffness, but it’s pretty undeniable that with proper engineering a monoleg will have better performance.

        • art December 12, 2012 at 9:09 pm -  Reply

          It’s so cute when undergrads try to use math. Take a step back, close the textbook, and think for a second. A traditional rear sub-frame on a bike is a tetrahedral truss. Pretty much all tension and compression, while a monostay is is a twisted cantilever. Now, you don’t even need to bother with the math to know that long, slender tubes are great at supporting tension, mediocre in compression, and utter rubish in bending and torsion. I highly recommend working out the full analysis over your semester break. A lot of the world, from bridges to bike frames, is going to make much more sense when you figure out for yourself that cantilevered really are a terribly inefficient way to support load.

          • Androo December 12, 2012 at 10:14 pm -  Reply

            No need for the snark.

            You must be right, though. That’s why all cars and airplanes use monoleg wheel carriers – oh wait…

  2. Erik December 12, 2012 at 6:36 pm -  Reply

    I too think the monolegs are nice and practical. Good to see more of it, and of its history.
    That is an clear and concise explanation there Androo, lik it. im also fond of monolegs and constructed the no-fork, discussion here:

    • Androo December 12, 2012 at 8:44 pm -  Reply

      Ooh, I really like the look of that! Very elegant lines. Nicely done, sir. One of these days I’ll build myself a monoleg fork…but I work in composites, and forks are a little bit beyond my comfort zone at this point!

  3. Cycle Shop December 13, 2012 at 7:38 am -  Reply

    Crazy to think how far the bike has come since then !!!

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