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SRAM Deraileur for MCR

by Alan Milligan — last modified Oct 13, 2022 04:14 AM

Our journey to CAD design and metal CNC/3D print a custom front deraileur for SRAM on the mighty Giant MCR

The Problem

The Giant MCR was produced from 1997-2000; a short production run as the UCI banned monocoque and other non-parallelogram frames in 1998; essentially destroying frame innovation to this day.

This project is aimed at taking this 1998 MCR Two frame and updating it with the best modern cycle engineering of today. The bicycle industry is inundated with marketing over engineering - so this is no easy task.

What does appear to be a genuine innovation is SRAM's yaw-angle front deraileur. Rather than simply tracking in-and-out, this also pivots - creating a fan-angle tracking the chain across the cassette.

We are sold on this; and thus have ditched the Shimano for SRAM. The SRAM derailer; unfortunately; has a much longer mount/pivot quite quite different to the Shimano - necessitating a custom hanger. The deraileur must fit within the recess in the frame; and whereas with a tube frame where you could simply bend a hanger and/or adjust the mechanism to fit; that is not possible within the limitations of the monocoque.

The Solution

We started with the open source CAD site, GrabCAD and found a Deraileur Hanger. Unfortunately, this design uses Solidworks, a properietry solution; and incompatible with FreeCAD.

A bunch of iterations later; printed and tested with filament; we're confident we're ready for a production run. Interestingly, none of our prototypes have proven strong enough to actually work in the field - the small amount of flex induced when attempting to shift to the top chainring means we've not actually been able to confirm with static testing.

If you're an industry participant we've reached out to for CNC/3D printing; you may download our STL.



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Alan Milligan

Alan Milligan

Alan Milligan

Location: Sydney, Australia
Alan Milligan
Alan is the principal technical architect of Last Bastion Network solutions in Australia. Alan's background is in application development with a number of global titans of retail and investment banking. Alan also has a history of CIO roles for a number of start ups where he delivers business value with open source solutions. Talk to Alan about how you can deliver critical infrastructure while mitigating risk and managing your existing vendor relationships.