Waxed Chain Break-In Setup

First, credit to the ChainBed Pro by Rotation Engineering for the overall idea, and to user dac_201215 for the general idea of how to do the cogs, though I ended up making completely new models for my needs. ;)

Parts needed:
5 - Ender3 jockey wheels (recommended for the bearings and middle spacer)***
2 - 608 bearings (found in fidget spinners and skate wheels)
5 - M5x40mm screws
1 - M8x50mm screw
5 - M5 nylon locknuts
1 - M8 nylon locknut -OR- M8 female threaded knob
50 - M5 standard washers
10 - 3/16"/M5 fender washers
2 - 5/16"/M8 fender washers
1 - 36mm socket to run drive cog
1 - 1/2" plywood board (at least 18" x 8")

*** = Can substitute general 625 bearings and M5 1mm thick metal spacer/washers, preferring smallest outside diameter possible, 10mm or less.

Prepare the Board:

1. From a 2'x2' or 2'x4' plywood sheet from the Big Box hardware store, simply cut a piece 8" wide which gives plenty of overhang on the sides and bottom.

2. Scribe lines lengthwise at 2", 4" and 6" from one side, and mark one short side as "TOP"

3. On the 2" and 6" lines, mark points at 3"  and 15" from the "top". These will be the corner cogs.

4. On the 4" line, mark a point at 5.5" from the top for the center jockey.

5. Drill 3/16" (5mm) holes at the 5 marked points.

6. On the 4" line mark points at 8.5" and 12.5" from the "top".

7. Drill 5/16" (8mm) holes at these two points.  These mark the extreme of the drive cog adjustment slot and its up to you to hog out the slot to the best of your abilities.  I drill several holes along the center line and then chewed the remnants out with a jigsaw. The idea is to maintain the same width for the whole length of the slot, but as long as the M8 slides along fine, the fender washers to account for much of the slop in your cut.

Assembly

1. Press the 625 bearings into the jockey cog halves from the non-flat side.

2. Press the 608 bearings into the drive cog halves from non-flat sides.

3. Take M5 screw, in order, slide on: standard M5 washer, one cog half, M5 spacer/washer, one cog half, 4x standard M5 washers, 3/16"/M5 fender washer. Repeat 4 times.  Insert each assembly into the 5 jockey holes in the board and secure from the rear with a fender washer and M5 locknut until snug and cog still spins smoothly.

4. Take M8 screw, in order, slide on: M8 washer, front drive cog half, M8 spacer, back drive cog half, M8 standard washer, 5/16"/M8 fender washer. Insert through center slot in board and add 5/16"/M8 fender washer and knob/locknut.

5. Slide drive cog to bottom of slot and check the chainline with the lower jockeys by eye. Add or remove washers from drive or jockey cogs as needed. As long as it is within 1-2mm it should track fine.

Use

1. Fish the chain through so that the chain engages the teeth properly on all cogs.

2. Apply upward force on the drive gear while tightening its bolt to maintain good tension on the chain.  A little slop in the chain is perfectly fine.

3. Run primarily at low speed.  Brief high speed turns are fine, but avoid too much as the chain will warm up and that is probably not good for the system and will likely shorten useful life of the wax.

4. You can optionally set a stiff plastic bristled brush along the outside of the chain to help loosen any wax hardened on the outside of the links or loose bits getting worked out from the crevices.  Don't press too hard so as to not add too much tension, and be aware of the bristles direction so to not get it jammed up in the chain.

Notes

• The cogs have lips on the inside so that they cannot work themselves off the bearings over time. This is why the spacers are required between the cog halves and allows the bolt to be tightened without binding the bearings. You may have to trial and error different washers to get the thickness right, or you can adjust the Z-scale of the cog slightly to encourage another layer or two to match the washer thickness.  This is why the Ender3 jockeys are encouraged as donors because the spacers are just about perfect.

• Use an old quicklink/master link to connect chain and use only for this device.  The link doesn't need to be particularly secure since the tension on the chain is consistent and there is no chance of backlash, and no sense unnecessarily wearing a quicklink you will be using on the bike.

• Drill two 9/64"/3.5mm holes near the edge and you can press the quicklinks into the board for storage.

• No need to glue the halves of the cogs, as the bolt tension will hold them pretty well, and the chain will keep them aligned.

• I printed on a plain steel bed with gluestick, but smooth PEI would also be ideal.  Can't vouch for a textured print surface allowing everything to mesh well together.

• My layout focused on a full 114-link 10-spd chain, but I believe it should accommodate most common lengths. If you need longer or shorter just drill new holes along the 2" and 6" lines above or below the bottom jockeys as needed. The spacing isn't critical except to ensure enough room so the chain won't collide when the drive cog is tensioned.

• If it's not obvious, always stand in front of the device while using it. If something does fail, it will tend to fail outward from the top, bottom or sides, which could be hazardous for anything along the perimeter.