Modifying a 40 year old bicycle to support sequential shifting

I have a 1970s vintage Raleigh Grand Prix, which I used to use to commute between my apartment and classes/work. It’s served me well, but after being stored for a few months in a humid basement, it was really  hurting. I avoided taking any pictures of the bike at this point, but believe me, it was in desperate need of some TLC.

I took chose this moment to also add something I had wanted on the bike for a long time: proper Drop Bar shifters. The original bike had friction shifters on the down tube of the frame, like all biked at the time. These were difficult to reach when on a busy road, and even tougher to get in the right gear. It was time to upgrade.

IMG_20141026_113603672-2.jpgI  decided to switch to an 8 speed setup, as that was the largest number of sprockets that I could fit on to my narrow bike frame. Locating and ordering the components was time-consuming, but not all that difficult. The mystery part of the conversion was actually a very small component: the front cable housing clamp.  Drop bar shifters use a housing to transfer the spring tension from the Derailleur to the Shift lever. These housings must be fixed to the bike frame, in order for the shifter to work. Most modern bikes have these built in, but mine doesn’t (for obvious reasons), so I have to come up with my own method of holding the housing in place. Off to the printers!

There are off the shelf options for these holders, but they are designed for BMX bike frames, and cost more than I’m willing to spend on a silly piece of metal. So, in my typical fashion, I modeled a housing holder in Inventor, and threw the model onto my 3D printer.

Image
Rendering of the proposed Cable Housing Holder

The first version of the holder failed very spectacularly on the first attempt at using it. The tension exceeded the material strength of the plastic, and the print was torn apart and thrown halfway across the room (fortunately, it was away from me!). After thickening the model a little, and modifying some printing parameters (AKA: increase the density), the second version held fast. I’m excited to take my new wheels out on some roads and try her out! If only it wasn’t 40 degrees with freezing rain outside…

IMG_20160323_164416977.jpg IMG_20160323_163957622.jpg

 

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