Harmonic Gearbox with planetary inside

Exploring the concept of a Planetary inside of a Harmonic. This is the first draft Print. Learned quite a bit. Will make the flexor a bit large so its less oval - a little thinner maybe (it will get a cup for the output in the final version. And of course this is missing all the brackets etc that hold the motor and the ring and keep the sun in place etc. It was just a test to work out the procedures and math involved to design one of those for 3d printing and explore assembly options. Before I teach it to the kids I need to know what I am doing. Interested to see if the planetary inside can take the place of an elliptic bearing. So far its looking pretty good. This one is about a 40:1 with the less elliptical flexor the next version will probably come in somewhere between an 80:1 and a 100:1 Not too worried about the ratio at the moment just the procedures and protocols needed to be followed to make one. And for now The yellow is HIPS and white bridge Nylon Production versions if we ever get to that will be all Nylon and probably something better than Bridge


The real question is, can you do this for a drive train :eyes: ?


Probably Not but for a climber maybe. For a drive train you probably want something in the neighborhood of 6:1 to 12:1 the smallest reasonable setup like this is probably 30:1 For the drive train I am working on 3d printing a Hypo Cycloidic and I got one of my kids working on a planetary inside of a wheel with the motor mounted on a 90 to save room. I guess I give summer work too

next thing we know, you are going to be printing a whole robot! Can’t wait to see what you do next!

That is in the works The project is further along now but this is a pic from “wheel down” day which for us is when the wheels are mounted and all 4 (or how ever many) actually touch the ground at the same time

And that is the 400:1 coming along its a pain to assemble and align and we learned a lot from that

And Smokey bot is almost done - it would be if someone did not burn the PI that drives it to a crisp (arms and helmet off in this pic to make trouble shooting the electrical/electronics easier)

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Harmonic Gearboxes are so cool! Do you know of any robots that have used non-conventional gearboxes (ie not spur gears and planetary gears that most teams use)?

No I don’t only thin “unconventional” we did so far is that we 3d print them and all of our gears are double helical involute gears and we used double rack and pinion gears here are parts of our updated version

And we also print bevel gears

Amd working on sticking a planetary into a wheel

With a mechanum mount slipped on as “tire” Actually tomorrow I am meeting the lead engineer (a soon to be sophomore) on that to see what progress she and her team made (There are some sizing and ration problems and printing problems to be worked out)

What tool do you use to generate all of these gears?

Inventor Even made a youtube video on it

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And some basic gear knowledge required like what is an involute gear shape or a herring bone gear and what is addendum an pitch and modulus and pressure angle etc and how does it impact performance etc. Members who want to be “gearmasters” Will have to learn all that first

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THIS is what I love most about FIRST and CD! These are things I never would have known about or considered otherwise. Now I’m getting all kinds of ideas about how to deploy this line of thinking to our team.

A few general questions: What material(s) are best for 3D printed gearboxes? How durable are they? Clearly there’s immense educational value in designing and building them. Seeing them in an operational setting (especially a competition robot) would take the motivation and inspiration to a whole different level.

Materials is and It depends. For gears its Nylon we like Taulman Bridge or 910 and Hobby King CX12. Bridge is about $40/kg and the softest of them and ok for most gears . CX12 is harder, very slippery and a little tougher to print and about $70/kg 910 is in most cases the best choice hard, slippery, little easier to print than cx12 but close to $90/kg (prices are not figuring at someone having a sale) For enclosures we like Hobby King HIPS its tough and you can pick it up between $8 and 12/kg. We even use it for some slow speed gears like ball intake this year. Now printing requires a printer that can handle those materials (all metal hotend) and the knowledge and experience on how to do it. Most prints are coming out fine now but at the beginning we wasted quite a bit of plastic making mistakes. We currently have a Matterhackers PULSE with an E3D V6 hotend and a Garolite build plate (makes nylon printing easier) We are getting an Anycubic Chiron for bigger prints (400x400x450 mm build volume) which will come next week and probably be operational in a few weeks after that as we will modify it to our needs (replace the hotend with an all metal one, upgrade the stepper motor drivers and make the necessary changes to the Marlin firmware plus build an enclosure to improve print quality which will necessitate some rewiring and moving of some components like the electronics box and filament spool holder. But then we should have a big 2nd printer that comes in in budgets ( < 700) This should help us finish “Bumble bot” (this years robot in plastic which we will test at an offseason competition in November, I display bot, a couple of gear boxes and if the kids don’t get too busy with other things we intend to build a 1mx1m CNC that will do plastics, wood and some aluminum we have about $500 budget planed for that Probably an XYZ setup using Tslotted extrusion, a cheap router motor with Bits some 3d printed parts a Mega Arduino board some drivers, some NEMA 17 or 23 steppers etc running Marlin and GRBL to produce the G-code. Is that going to work? IDK but you don’t know until you try as for how tough is plastic - it depends. PLA is very hard but brittle Nylon you can hit with a sledge hammer and it will deform you hit it hard enough it will stay deformed so every material has its own characteristics

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