I seem to remember that someone created a 3d printed part that would make it easy to tell when the sprocket is pointing straight up. I don’t remember the details and am not finding it in a search.
something that clips on the top of the sprocket and has a long, straight edge would help by itself, and be more useful with a level, but if it included a place to attach a weighted string so you can easily see the difference between vertical and where the line is, it would be very accurate
This doesn’t even need to be made specifically for one size sprocket. If it has two pins that straddle one sprocket point it could work with multiple sizes (although you would have to be sure it was really seated well)
another approach would be to make something that has a horizontal flat on it that you would use with an existing angle that you have (or make with the 3/4/5 right angle approach)
The problem is that one encoder step is so tiny, over a 1m length, an error of one encoder step is 0.77mm. We don’t need to try and be that accurate, but the closer we get, the more accurate we will be.
If we could make things precise enough, this is where a vernier scale would be ideal, but I don’t think we would have with a precise enough bearing to be able to make one
It was me who posted the original idea. This is the post Alignment guide
Thinking about what @dlang is saying I have revised the design to have two pin positions so you can hang two ‘plumb bobs’ off a short center pin and a longer top pin, thus when the string’s align you have top tooth vertical. The pin can be anything you have to hand (cocktail sticks or matchsticks?) drill holes to fit them.
Here is one I have just printed to test the fit, I needed to adjust the size of the cog hole to fit tightly on the supplied cog. I have updated the thingiverse model.
