Planetary gear

[Sunefar]

Hi.

I would like to try some experiments with gears..

something like this :

or

anybody know how to do this with lego bricks?

Thanks!

[legolijntje]

There is a little article about on TechnicBrick's.

HERE

[Sunefar]

GREAT.

Thanks!

[PavementPilot]

I forgot where I saw it, but someone built one with 8t gears inside of the large turntable.

I did a quick lxf to illustrate.

PlanetaryGear.zip

Edited May 2, 2011 by PavementPilot

[Splat]

Some time ago, I put together a proof-of-concept for a larger planetary gear, which you can see in my BrickShelf folder.

The idea was to have a fixed annulus gear (the outer ring), and in this case it is made out of gear racks. As the planet carrier spins, at least one of the planets is in contact with the annulus gear at all times, which is also linked to the sun gear. You can also swap the gears to get different ratios, as shown in this pic.

It works (I made it out of real bricks too), but it is a bit large to include in a real model, and the teeth can grind and/or jam sometimes. But as a proof-of-concept it was interesting to see.

Wikipedia's Epicyclic Gearing page

Edited October 13, 2012 by Splat

[allanp]

I forgot where I saw it, but someone built one with 8t gears inside of the large turntable.

I did a quick lxf to illustrate.

I'm not the only one to have done this, but hear is my simple and strong version of it:

using this part to holt the 8t gears:

http://www.peeron.com/inv/parts/63869

Edited May 3, 2011 by allanp

[Alasdair Ryan]

What about useing one of these:

I dont know if this is any use to you but hay.

[aliburke]

try to build a Simpson planetary to show the principle of automatic transmission:classic:

[Sam42]

I forgot where I saw it, but someone built one with 8t gears inside of the large turntable.

like this?

21012011309 by sam2442, on Flickr

-a planetary reduction hub i built a while ago, (untested)

[PavementPilot]

like this?

21012011309 by sam2442, on Flickr

-a planetary reduction hub i built a while ago, (untested)

Bingo

[Brickthus]

What about useing one of these:

I dont know if this is any use to you but hay.

I've done that. 5 56T turntables will fit in a Hailfire Droid wheel. I even had 8T cogs inside the middle turntable too

You will find that the turntables in the wheel have a lot of friction. The numbers of teeth add up OK (3 x 56 = 168) but the wheel is a bit tight. When I used this system, driving from the sun wheel, I had to add extra motors in the gearbox to force the planet carrier and annulus to contra-rotate, because of the high friction. The friction was partly from the five turntables though, so not just the wheel's fault. Power Functions was really useful because I could drive the extra motors from the battery with infra-red control while it was all rotating!

Some more planet gears, different ratios with the Power Miners wheels here

A Power Miners wheel gearbox has less friction, little enough that a smaller version of the Hailfire Droid wheel application was able to overcome its friction and have the annulus turn the right way, without additional motors mounted in the gearbox. It still took quite a lot of input power though - four 9V 4000 rpm motors and 1.3A of current at 9V.

The Power Functions motors also use planet gears. In this case 3 planets in each of 2 stages for the medium and XL motors. I took a stage out of a medium motor to increase the speed (no point gearing down and up again), but in the end there wasn't much more power available.

Mark

[2GodBDGlory]

I got tired of waiting to acquire the AT-AT ring gears, and now that the B&P interface has changed and they're no longer on there, I decided to take matters into my own hands and 3D-print some of my own.

That led to experiments to determine which gearing options worked with it, and in the end I found four options: 24:12:24, 20:20:20, 16:28:16, and 12:36:12, plus a bonus of 14:32:14 using a 3D-printed 32T gear:

That got me wanting to try out options with the old 48T option from the Power Miners wheel, and in addition to the three options commonly known (20:8:20, 16:16:16, and 12:24:12), I noticed that by using retro 14T gears one can get 14:20:14 as well. This is also another area where the new non-beveled 12T and 20T gears will be handy, because my existing designs with beveled ones require the carrier to be set back half a stud, which would not be necessary with those.

Finally, I decided to make a spreadsheet of all the possible combinations of gears for all possible ring gear sizes in multiples of 4 from 24 up to 60, using the formula that the sun and two planet gear tooth counts must add up to the ring gear tooth count.

The takeaway here is that the 40T ring gear is likely the most practical for Technic MOCs, though it doesn't exist, because of its compromise of many ratios and small size, while the 60T we did just get is rather disappointing in that it doesn't even have five possibilities like 52 and 56 because two of its ratios happen to land on gears we're missing, with the 32T and the 44T both working theoretically. 56 would also have an extra possibility with a 32T gear.

With this in mind, I'll think about designing and printing a 40T ring gear housing and designing a more realistic automatic-style planetary transmission, though I've got plenty of other projects I'm interested in.