Erickson Gizzmo

thingiverse

Kind of an obscure part. This device plugs into front/left double Shimano brifters, with externally routed cables (i.e. older). It allows double brifters to use triple cranksets. Check out Sheldon Brown's entry here: http://www.sheldonbrown.com/gloss_e-f.html. As far as I know, this device is no longer in production. I personally have wanted to use something like this, so I thought I'd try it out. How I Designed This I guessed based on pictures here: http://www.sheldonbrown.com/gloss_e-f.html. I pulled measurements off a Shimano RD-M786 for the ferrule insertion point, and a shift ferrule I had lying around. Check my profile to get dimensions for the latter. The difference between the OD of the carrier and the ID of the brifter mount is 0.5 mm because I didn't want this thing to rattle. As a result, it could be too close. If you don't understand how this works, read the Sheldon Brown entry, and the procedure in the assembly & materials section. Note that the axial difference in the carrier's position relative to the brifter mount doesn't actually matter, as long as it's sufficient. If it's too slack, then the FD will just slam to the lower limit, which is okay. It'll only be a problem if it slackens the cable too much and the cable catches on something, which I doubt. Because of the way this works, I guessed how long the cutout needed to be axially, and just wrapped it to half of the circumference of the brifter mount large OD. As you can see in the wireframe assembly view in the double/triple mode images above, the carrier always has a sufficient insertion depth that it should be hopefully secure. Updates December 21, 2016: The current problem is that I need to increase the barrel depth on the brifter mount so the carrier is well supported. The Solidworks assembly is extremely sensitive to changes right now. If you even spin the parts relative to each other, you will break the brifter mount SLDPRT. I'm not sure why. December 22, 2016: I fixed all the parts now. Check the double mode and triple mode images. Now the design should be a lot more robust. I also realized that flipping the switch may not do anything. If the cable tension is high enough, then the carrier will be pressed too hard against the brifter mount and they'll rotate together. Unless you use both hands to force them to turn relative to each other, it won't actually work. However, there's no way to find out if this will be a real issue until it's tested. As of now, I don't have any immediate plans for trying this on any of my bikes. If you do test this, let me know how it goes. As such, this project will be listed as "work-in-progress" indefinitely until someone tests it, or I do, whoever does it first and gets back to me. I'm also concerned about the 4 mm diameter of the switch. The bigger it is, the stronger it is, but it also enlarges the cutout necessary to engage the triple mode. Assembly & Materials Installation is simple: 1) Insert carrier into brifter mount. 2) Insert this assembly into the brifter ferrule port. 3) Set the carrier to be into the "double" position on the brifter mount (see image above). 4) Install shifter cable and housing, and adjust as necessary. You should now be able to use only the middle and large ring. 5) Flip the switch to sink the carrier into the brifter mount, thereby releasing tension and allowing the FD to access the small ring. 6) Adjust lower limit as necessary. Filing may be required for these interfaces: * OD of carrier & ID of brifter mount: Clearance is 0.5 mm right now * Small OD of brifter mount & ID of brifter ferrule port * Brifter mount length that inserts into the brifter (could be too long) * The transition between the slide and the "double" position: only if that notch is too deeply set in for your taste. Too undefined, and the slide will slip/engage frequently. Too defined, and it'll be difficult to engage the triple mode.