Dan DWRoboticsWell, I spent an entire day designing a pseudo bevel gear - and it works.
Quite a boring update, but the implications of what I can do with it are quite great. I've been toying with the idea for a while but since my main design tool is sketchup, there are no inbuilt tools for designing gears and so when I do it, I do it by manually designing and drawing out the teeth in sketchup and then rotating and copying them to make a full gear. There is a certain amount of intuition involved and it is by far not the best way to create mechanisms, but this one is working really well. What it does is gives me a really nice way to have a 'Yaw' inbetween the shoulder and elbow of my humanoid robot, but keeping the form factor within humanoid proportions.
I have been putting this off for quite some time because I knew how long it would take me to get a working design.
What this also does, is gives me a really nice mechanism to use on a gripper, for a different project I have been working on in my head. A super cheap, but highly functional table top robot arm. The gear above is not really a 'bevel' since the gears are not angled and so don't truly mesh in the way a bevel does, but it does give me a really nice smooth motion between my cheap hobby motors and any Yaw joint that I want to make.
Discussions
Become a Hackaday.io Member
Create an account to leave a comment. Already have an account? Log In.
Great stuff! I knew it must have a name because I have seen them in old tools (hand drill). I will definitely check out Wavefront, need to take some of the guesswork out of the process.
Are you sure? yes | no
Ta :-)
WF files are this simple:
A text file containing at least three vertices normalised on Z - that is, with the polygon facing up on the bed, the vertices are described clockwise. This instructs WF which direction they are pointing in - if the order is reversed you are looking at the inside face ;-) They are just listed as three numbers preceded by the letter v:
v -10 10 0 is the top left coordinate on a rect centred on 0,0,0
Following this the edge data, which gives the actual sequence of the coordinates preceded by the letter f:
f 1 2 3 describes the triangle forming the upper left of this rect, beginning with the top left, then the top right and then bottom left, so it faces up. Thats important, if you want a solid plane triangle that can be seen from both sides you have to define v once and f twice:
v -10 10 0
v 10 10 0
v -10 -10 0
f 1 2 3
f 1 3 2
That's basically it, you can build meshes by listing multiple edges pointing into the vertex array which begins with 1 and not 0 incidentally. Might want to watch that one working with arrays ;-)
I've uploaded GString to #MillBits Engine files. You'll need to compile Gina and Cheeks for Linux, I dont know if it will all run under Windows ;-) There's also a test object built by it, and a PDF with the format in it for reference, WF files are human-readable anyway. ;-)
Sorry my code is a bit dense, I havent had time to comment it. Bad Toad :-)
Are you sure? yes | no
Thats a Crown Gear, if you want its proper name ;-)
Nice technique, and you are right about intuition with gear geometry. Thats a lot of hard work to get one gear tho. If your coding is up to it, WaveFront files import into anything and are stupid-simple to write out, all you need is a bit of geometry and you can have all the gears you like.
There's some functional maths in https://hackaday.io/project/19281-millbits-engine. :-)
Are you sure? yes | no