Planetary Gearset

Wouldn’t it be cool if someone made a planetary gearset for an automatic transmission?
I wanted to try my hand at Inventor, so I spent the night clicking around, and this is what came out. Obviously it’s still missing the clutches and actuators needed to be a transmission, but I think it looks pretty :). I don’t have the extra parts to build this, but it would be really cool if someone else did.

What holds the chain to the 1xN metal pieces?

It looks cool, and I understand how they work but, what is the actual application of a planetary gear?

Zipties probably :stuck_out_tongue: You’ll need something there to hold it against the metal, but I’m sure the sprockets will make up a lot of the actual structure.

It’s a concise way to create different gear ratios without having to "move any of the gears around. All the gears are pretty much always touching, and you just have to change the inputs, outputs, and what you hold steady. I doubt it has much real application in a VEX drivetrain though. Now if someone were to make a pneumatic engine…

I like it, but wouldn’t it just be easier to work on a different kind of transmission? I might build a vex transmission one of these days just to do it, But first I have to get my works 4 axis lathe :wink:

Overall though seriously I do like that people are thinking out of the box :smiley:

By changing inputs and outputs and what you hold still on a differential, you can get a similar effect. Powering two of the three points on a differential will produce 3:1 with twice the torque of one motor. The planetary gear box (why a gear box, it is most defiantly a circle) is a flatter package but has a larger diameter than the differential. Not counting style points.

I believe someone on 575 was working on one of these. It was crude but workable.

I wonder if any teams at Worlds will have a planetary gear shifter on their robot.

Like, for example, a team from Hawaii. Or a team that wears red shirts. Or a team with a member who’s active on VEXforum. Or a team with a four-digit number that begins with 24…

What a coincidence that would be!

Wow that would be a great coincidence… an even better coincidence would be if they posted a couple pics of it on this thread or PM’d me them if they didn’t want to post it on this thread and explained how it worked to someone (me) who doesn’t know how they work :stuck_out_tongue:

EDIT: Ope, I missed the “hint” that 13of2 dropped. lol. oh well

Our team built one for Worlds this year (a planetary gear). They’re on both of our bots.
Well, it’s not a true planetary. We call it a compound planetary because it has several layers. The ratios that it can produce are 1:1 and 3:1. It shifts between these by use of a piston.

Images here:

Here’s an excerpt from our Innovate Award write up:

We were very tight for space in the Innovate award submission, so we didn’t mention that those four gears are more like a stand-in for the ring gear rather than ring gears themselves. Hopefully we get an interview though!
Video forthcoming!

Oh, please do tell. I’m curious as to what a “real” one would look like. What made you pick a planetary gear system? It seems right for continuous hard-to-precisely-control output like a car engine provides that has to switch at high frequency at high torque, but it hardly seems suitable for a motored drive like VEX has. What problems did you run into, what does the final design look like? What gear ratios do you get? How fast can you switch? Do you wear down your gears? TELL US MORE!

I posted some specs earlier. I’m on the same team as 13of2. :stuck_out_tongue:

We wanted to pick a planetary gear system because we felt like both speed and pushing power were needed in Gateway (this has been our experience).

It’s a little slow at changing (read: not immediate) but it gets the job done. Sub-second changing speed, I’d say, per my estimates.

Problems - It’s relatively touchy. Touchy enough that one cannot just replicate the design that we’ve posted here. (EDIT: However, the “touchiness” is not enough to render it ineffectual - it just needs to be checked after matches, etc. Spacing is where most of the touchiness comes from, and that’s just trial and error.) There’s some extra bits that need to be added so that it can “reset” properly. Also, screws come loose, but we fixed that with locknuts. :smiley:

We haven’t had any weardown on our gears.

That’s quite a mechanism. I really want to build a pneumatic engine now to exploit all of these too-rugged-for-just-VEX-motors devices that are popping up. Maybe we can have a miniature VEX car. That would be something cool to do next year for worlds. It wouldn’t be too hard if different teams built individual pieces of it from excess parts and assembled it at the competition. I mean, you could definitely build a V6 engine with three pneumatic tanks, we have transmissions going as we can see on this thread, VEX already sells differentials and u-joints, and the potentiometer already looks like a steering wheel. What more incentive do you need?

It looks interesting. I didn’t understand the write up, so maybe the video will help. My understanding of the main advantages of planetary geartrains is that it can provide high ratio high-torque capacity in a compact space, for electric screwdrivers for example.

Sometimes pictures on the forum seem to inspire new Vex products:

  • double-roller small omni-wheels
  • Mechanum wheels
    Maybe the recent pictures will lead to a ring-gear and planet carrier products from Vex.

Mention it on the new product ideas forum, sometimes I notice ideas mentioned in various threads but they are never restated on the product ideas forum. Having their own threads will others to comment on the ideas and not get lost in the mass of information of the forum.

Yep, that’s exactly correct. That’s why we wanted to use a compound planetary gear + pneumatic shifter instead of a regular “dog shifter” (manual transmission).

Both of these Planetary gearboxes are pretty cool :cool: Now I want to make one.

What an excellent Idea… I might try to build me one of these…

Did you create a BOM for the parts required??? You might publish it with the Photos and the Video(s)…

Here is a video of it shifting!

Sorry it’s late, we stay on Hawaiian time

Like this one:
Planetary gear educational set


  • Dean