It’s been a long time since I’ve posted, but alas, I’m back! Today I want to share a project I’ve been working on, a vex legal 3 speed planetary transmission! Most advanced vex transmission to date? - YouTube
The design process of this started with the more “traditional” approach to this transmission link and after constructing it with a custom ring gear, I found that it was unable to provide more torque. I knew then that I needed a new design, and after some digging, I found this. This proved to be exactly what I needed, and I started making prototypes. The design presented in the video above is version 4, and works very well. The internal gear teeth are: SUN=40 PLANET=10 RING=60 feel free to ask questions and provide feedback!
This post was ghostwritten by Ian Barber.
Wow, Drew! Great moves, keep it up, proud of you! Amazing transmission! Thanks for all that you do for the community!
This post was ghostwritten by Ian Barber.
Good work anti, this is super cool.
On a side note, love the h3h3 reference
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Thank you Anti, very cool!
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thank you anti, very cool !
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It’s been over 9 months since my last post. I was suspended for very compelling reasons (and actually IP banned as well) and I owe the administrators that un-suspended me a massive thank you and an apology. @antichamber I also need to thank you because you cleaning up your act and coming back onto the forums set the president (I think) for me.
This is an incredibly sophisticated transmission, well done! My only question is what advantage a 3 speed transmission has over a 2 speed one.
Stay awesome!
Very nice implementation with the 3d printed gears. When you get down to cutting gears from polycarbonate, you’ll need to take some precautions. When cutting small gears like that, you’ll need to pay attention to the laser kerf and account for it in your gear design. You may also need to cut thin slices and stack them depending on the focal length of the laser lens. (A short focal length lens makes a shorter, more angled cone, leading to either an angled cut or a larger kerf in the material.) Stacking multiple thin cuts helps alleviate kerf and angle issues.
Also, polycarbonate cutting fumes are toxic. But you can’t leave the laser fully unattended while cutting, since flame-ups and fires are possible in the laser cabinet. So be very careful, or get help from someone who has done this before.
To account for the kerf, you have to either scale the drawings by the kerf width or design with the kerf width in mind. Which means you need to know what the kerf width is. It will vary from laser to laser, and change with how dirty the optics are and how well-focused the beam remains.
To accurately measure the kerf, cut multiple identical rectangles of known size from the material you will be using, then lay them long-edge to long-edge on a flat plate. Measure the total distance across the rectangles with a caliper. The kerf is then:
((n * design width) - total measured width)/(2 * n)
Where n is the number of rectangles. A good number for n is 8 or 10, but don’t use fewer than 5.
I can help generate the gears in .svg format if you need that, but since you’ve already been able to print them, you may not need it.
What about making it competition legal? Multiple thin slices add up in area, as opposed to one thicker piece.
The overall flat layout of the gears will still remain quite small, even assuming you used a stack of three or even four slices. You probably only need two slices for it to be very workable.
The gears in this VERY non-legal VEX assembly were two layers of 1/8 inch nominal acrylic.
Gears of that thickness would likely work for @antichamber’s purposes.
Very nice work!!!
That’s not quite @sankeydd 's concern. The VRC rules say all the piece must be cut from a single sheet with size limits. Cutting three or four thinner pieces uses up three or four times the allowed sheet as cutting a single piece because using a thinner sheet does not allow you to use a sheet with a greater area.
I’m surprised @sankeydd didn’t ask how the slices would be connected to each other when asking that question, though. That could be a pretty big problem within VRC rules as well.
Thanks; this is one of my son’s summer projects. I helped with the gear layout and cutting, and he put it all together. More stuff is coming together for the platform. I’ll ask him to post something about it sometime.
I understood his concern, but you’re correct to call it out specifically like this, since the purpose of the forum is to help everyone, not just the people directly involved in the discussion.
So, to be clear, my assertion is that the gear outlines are so small that it won’t use much of your allotted 12 by 24 inch flat layout even if you cut four copies of each of the gears. And you probably only need two copies of each.
Indeed, that’s a very good question. You can’t glue them, of course, so what do you do? What we’ve done is use screws and nuts in most cases and axles with shaft collars on each side in others, depending on the gear size. You really have to get the size right to use the standard axles and shaft collars to “pinch” the gear slices together. It’s easier to cut square holes for the larger axle inserts if the gear size will accommodate it. All in all, It seems to work pretty well.
And Delrin sheet is a great material for gear cutting; should consider that over polycarbonate. Though it is a good bit more expensive.
@antichamber This is really impressive, but how’s the friction? I know that’s what plagued your earlier versions of the sp mobile goal lift. Have you done any friction tests? Regardless, I still admire the inventiveness.
Do the delrin ring gears strip at all? From testing with polycarb and delrin gears, they tend to strip after using them for a while, however those were tested with metal VEXPro gears at around 1300 RPM instead of the plastic gears from vex.
All the gears were printed in 1/16" thickness and are held together by screws. All gears are 2 layers thick, and they all fit onto the allowed sheet size with lots to spare.
The friction is actually really good, the carrier will spin for a second if I give it a twirl with my hand.
Does anyone happen to have a not-dead link?
unless someone downloaded the video or reuploaded it I think it is gone. His channel is deleted I think, but I don’t know why
that sucks. Sounded cool.
yeah, I watched it but I don’t really remember what it was. I don’t really understand how planetary gear boxes work.
They’re not that difficult. Here’s a good video
I watched that but I and I get how the velocities and stuff work but I still don’t like get how it is so useful. I might need to build one so I can see it and mess around with it