Collisions and Clearances

The Rambler has a great deal of subtlety in the design that may go unnoticed at first glance.  From time to time I will call these details out to better explain some of the thought and detail that went into making these frame-sets as good as they could possibly be.

In the previous post I mentioned the added benefit of using dual crown rack mounting points for added stiffness and safety.  This design feature adds a secondary challenge learned from previous attempts at this design by other makers.  As the front rack swings through its arc of rotation around the steering axis there is the potential for a collision between the rack and frame tubes.  With some designs this can occur both at the mounting bolts as well as at the down tube below the shifters.  A collision at these points often leads to a dent in this highly stressed region of the bike, and dents here often lead to fracture or buckling of the tubes, not good at all.  There is a clear analogy to this and standing on an empty soda can.  The can is quite strong until you make a small dent in the side, at which point the can generally collapses under the load.

The Rambler design addresses this at both locations.  The angle and spacing of the head and down tubes is such that there is a generous margin for the rack mounting bolts to clear, without degrading the aesthetic of the bike.

10.19 crown details-1140727We addressed the second collision point, the rack and down tube with the position of the shift lever boss and tube butt location.  By moving the boss down from its traditional location a little more than a cm, the rack will hit the boss before it hits the tube.  While any hard collision here is not great, the boss will distribute the point load of the rack tube over a greater area and reduce the chance of a dent.

10.19 crown details-1140723 10.19 crown details-1140728Details like this are part of what sets the Rambler apart,  building in safety and longevity for the frame.  Our pointing them out will help you to be a more educated consumer in the market place.  Adding integrated features like rack mounts, lighting wire guides and fender mounting points all come together to help build a better complete bike, a bicycle that can act as real transportation and not just a hanger for a bunch of clip on accessories.   The trick is in getting the details right, and we did with the Rambler.

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One Response to Collisions and Clearances

  1. joe b. says:

    Excellent touches! One of my worst wrenching mistakes came retrofitting a fork with crown mounts to my trusty old Cross Check. I didn’t know to check the downtube clearance and one unlucky swing with grocery load crumpled the tube.

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