Chain keeper

Parametric chain keeper design, for use with 1x drivetrains.

Customize to your liking.

I haven't tested the parameter space.

Untested/never printed.

Designed for two M4 x 20 socket head cap bolts & two M4 locknuts (7 mm width by 5 mm height).

Print both halves after adjusting the file for your frame.

The STLs are for my frame, a Fuji Jari, with the following geometry:

- BBDrop: 69 mm

- ChainStayLength: 435 mm

- SeatTubeAngle: 74.5 deg

- SeatTubeDia: 34.9 mm

- 42T ring

Sample Bike.sldasm provided for seeing it in context. The chainring is 43T in this example. The DiaTotoothRatio is found by 178 mm/43 teeth. The chainline is adjusted to my chainline of 50 mm.

Parts for the assembly (crankset & frame) are found in the Reference folder, which I hope are successfully uploaded.

Credit goes to Plamen Cherkezov for creating the frame model & Morar Adrian for the SR Apex crankset model, over on GrabCAD.

Parameters

See the equations picture above; there are comments there to explain all the variables.

You should be able to tweak everything within reason.

I wanted to design this to eliminate the superfluous concessions found on other chain keepers (see Paul Components') to allow the chain keeper to adapt to different frames. With 3D printing, why not just make it for your frame & no one else's?

You can capture the geometry of your bike by editing

- BBDrop

- ChainStayLength

- SeatTubeAngle

- SeatTubeDia

The drivetrain elements are largely driven by

- Chainline

- TotRingDia

- LargestCogToothCount

- ChainWidth

By finding the product LargestCogToothCount*DiaToToothRatio, you can find the rough diameter of the largest rear cog. This is important when determining the lowest height you can mount the chain keeper relative to the chainring. Any lower, & when you shift to the largest rear cog, you may find the chain rubbing on the keeper.

However, this method only accounts for the angle of the chain, projected onto the midplane of the bike frame; not the angle made by the chain projected onto the ground, if that makes any sense.

I use an outward draft angle to try & account for this instead.

Category: Replacement Parts