Chainring guard

prusaprinters

<p>Use case: I use a regular (not narrow-wide) chainring in the middle position of a triple crankset; a poor man's 1x drivetrain.</p> <p>I currently use a front derailleur as a measure of chain retention, but I still get rubbing when in either extreme.</p> <p>I'd get a narrow-wide chainring, but they are expensive or not available in the tooth count I want (40-46T) &amp; BCD combination (96 mm).</p> <p>This chainring guard replaces the largest &amp; smallest chainrings to keep the chain from derailing off the middle ring.</p> <p>This was<em>not</em> designed for preventing chain derailment off the largest ring (essentially a high limit screw replacement).</p> <p>I have STLs for my own use in 96 &amp; 64 mm BCDs (4-bolt) as a well as a test STL in 110 mm BCD (5-bolt).</p> <p>Has countersinks for standard M8 x 0.75 chainring bolts.</p> <h3>Customization</h3> <p>The SLDPRT file is parametric to an extent, but there are certainly many combinations that will fail to render.</p> <p>Here are the parameters I currently have:</p> <ul> <li>TotDia: diameter enclosing the outermost part of the teeth. The smallest diameter that will fully enclose your chainring.</li> <li>BCD: bolt circle diameter</li> <li>CrankDia: outer diameter of the interface between your crankarm &amp; the chainring itself. Needed to ensure a good fit. Assumed to be circular (you can probably get a very close fit on most chainrings).</li> <li>ArmWidth: width of the crankarm where it meets the chainring. For aesthetic reasons.</li> <li>GuardWidth: thickness of the guard itself.</li> <li>BoltCount: number of bolts (4 or 5 in 99% of cases). CAD file is untested for other BoltCounts.</li> </ul> Category: Replacement Parts