Trouble making a circular ratchet type shape with a hole in the middle

jaedon_leech

As a first little project to learn how to use the software I decided to do my best to remake a revolver cylinder from a colt single action army (I think guns are very cool from a mechanical point of view) and I'm like 1 or 2 steps away from finishing it but on the bottom of the cylinder is supposed to be 6 teeth that are shaped like curved ramps (Reference photos below, first is an image off of google the other two are the physical part I have) and I'm really struggling to recreate that shape. I have tried using the loft tool but it either ends up trying to make it go over the edge of the hole or makes the outer edge curve in too much towards the bottom. Is there something I'm missing or is this just an impossible shape to make cleanly.

Link to my current part: https://cad.onshape.com/documents/7173d0187578090432e23ba9/w/5ee65da55319d2cd310ba62a/e/a1d6a51f0ce91668dda20a95

Evan_Reese

Here's one way that I think should be pretty good. I'm using the wrap tool to make one of the teeth, and patterning the rest. Be sure to click into some of the dimensions to see some of the equations I'm using to find some distances (like the length of the pre-wrapped tooth). Wrap is going to be better than something projected since the ramped parts really should be helical.

Also, not what you're asking about, but that print looks like a good candidate for adaptive layer height, so you can print the ramps with a much finer layer height than the rest and get a smoother sliding action.

https://cad.onshape.com/documents/7fe36b1b5c99aef1e332a691/w/60587a507a05d3b7c6f77e28/e/c81af24d486ff3fd00cbff59

Evan_Reese

Here's one way that I think should be pretty good. I'm using the wrap tool to make one of the teeth, and patterning the rest. Be sure to click into some of the dimensions to see some of the equations I'm using to find some distances (like the length of the pre-wrapped tooth). Wrap is going to be better than something projected since the ramped parts really should be helical.

Also, not what you're asking about, but that print looks like a good candidate for adaptive layer height, so you can print the ramps with a much finer layer height than the rest and get a smoother sliding action.

https://cad.onshape.com/documents/7fe36b1b5c99aef1e332a691/w/60587a507a05d3b7c6f77e28/e/c81af24d486ff3fd00cbff59

jaedon_leech

I see how you've done that and it should be exactly what I am looking for, thank you so much.

About the actual part though, I had printed that part very early on in my 3D printing hobby career and so did not know about adaptive layer height but you're absolutely correct that it would be the perfect place to use it.

nick_papageorge073

Are the tops of the teeth really curved on the real example? I'm just wondering how they did that from a machining standpoint. I'd imagine it would be much easier to make the tops of the teeth flat, using the bottom of an endmill. Especially if we are talking abut over 100 years ago.

Also the acute angle between the top of one gear and the vertical wall of the next.