Working on a ratchet system to allow the measuring cylinder to reset

I last posted a devlog aaaageeess ago (~3 months). Here’s a refresh:

I am making a mechanical tape dispenser that fits in 2 tiles of a gridfinity base. If attached properly, it will allow the user to dispense tape with one hand. The main selling point, however, is that it measures the length of the piece of tape as you’re pulling it out. I haven’t yet tested this system, as it kind of requires having all of the design finished, so fingers crossed my ~18 hrs of work thus far won’t be wasted. See img 1 for initial sketch

I did manage to test one part of the system though. This was what I talked about in my first devlog: I made a test rig to test my custom chain and sprocket design which is integral to the overall mechanics. The result was quite satisfying and I ended up posting it on mkw and printables

But that’s all in the past. More recently….

I’ve been focusing on how the measuring system will work on the user interface end. This included making a number cylinder/prism which increases by 1 when its rotated 1cm.

The rest of the time has been spent trying (and mostly failing) to figure out how to reset the number cylinder to 0 when the user breaks the tape.

I started with an overcomplex design which involved a linear screw, telescoping axle, and more, and after a while realised it would be very inefficient and unreliable.

Ratchet design

I’ve now pivoted to a design involving a ratchet, however it’s still very much in the early stages, so it’s difficult to tell if it’ll be the right solution.
Since I’ve never designed a ratchet before, I’m going to do a very similar thing to what I did with the chain: I’m going to isolate the ratchet and make a temporary test rig for it so that I can test it properly.

My main concern for the ratchet is that it is very space-constrained. I.e. I’ve had to make walls thin and dimensions small wherever possible to even fit the mechanism inside the space. This has meant that it’ll be difficult to implement a spring into the ratchet, or at least difficult to use a 3D-printed screw. Once I can test the design, I’ll have a better idea of this.