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10979Re: [rootsradicals] Re: Kickback chain interference revisited...

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  • Pete B
    Feb 14, 2010

    It from the photo's it would appear you have quite a bit of chain clearance over the top of the front Horizontal Tube of the FreeRad but inadequate clearance underneath. 

    Also looking at the photo of the bike in mock-up http://www.booboodog.net/images/bikes/xtra/xtra-os-1.jpg it would appear that the front tongue of the FreeRad may be sitting a little too low (see the attached pic). Possibly due to the unique geometry of the donor frame.

    Taking a look at the dimensions Surly settled on for the BD  http://surlybikes.com/frames/big_dummy_frame/ they appear to have designed it to have the front dropouts, rear dropouts and (theoretical) FreeRad Mount points in a flat plane. Whereas it appears your's drop by around 1 inch where the FreeRad attaches to the donor frame dropouts.

    Also they spec their Bottom Bracket centre at 1.6 inches below the plane from front to rear dropouts. Your setup appears to be around 4 inches.
    You could try changing the geometry by raising the height of the Front attachment point of the FreeRad, You could do this by stacking washers between the tongue and the chainstay bridge plate or by sitting it on top of a FAP resting on top of the chainstays.

    Every bit you raise the front tongue will trade chain clearance above the bar for extra chain clearance under the Kickback stand.

    Just my 2 cents.


    'Newspapers are unable, seemingly, to discriminate between a bicycle accident and the collapse of civilization' : George Bernard Shaw

    On 10 February 2010 09:06, speedub_nate <speedub.nate@...> wrote:

    --- In rootsradicals@yahoogroups.com, "Rich" <astronut1001@...> wrote:
    > BTW with an eccentric bottom bracket is there any chance that the eccentric assembly can be rotated 180 degrees so that the chain run from the front chainring is moved enough to minimize or eliminate the interference with the Kickback?


    Yes, the EBB can hold the bottom bracket in either a "high" and a "low" position. Neither one offers the chain a straight shot in past the Kickback (basically, the "lowest" straight line the chain can run is limited by the forward bridge; the deployed Kickback impinges on this imaginary line.

    I'm going to take this to a local frame builder and ask if he can crimp the offending Kickback tube, then re-weld it to the plate that joins the two halves. I think that ought to do the trick.

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