Hand-cranked Planetary Gear

planet-a39

Make your own hand cranked planetary gearbox from laser cut parts.
The parts are now on my 3d printing/ laser cutting site. You can download them for free here:
You will need:

3mm plywood.
12mm dowel: 15mm long x 1 | 55mm long x 1 | 30mm long x 1
6mm dowel: 15mm long x 6 | 36mm long x 1
optional 12mm wooden ball
12mm MDF baseboard 130mm x 100mm
6 small wood screw.

Start with the parts from the ringgear.pdf file. You will need to cut out two copies of the ring gears. Cut out the parts from 3mm plywood on your laser cutter. These make up the frame of the gear box.  Each of the two ring gears is made from three layers. The centre layer has a longer tongue than the two outer layers.planet-a01

Use cocktail sticks to help align the pieces as you glue them together.planet-a02

Glue the third layer into place and again line it up with cocktail sticks through the location holes.planet-a03

Notice how the longer tongue protrudes from the centre of the ring.planet-a04

Clamp the parts up and let the glue dry thoroughly. Repeat this process to make up the second ring.planet-a05

Glue together the three spacers.planet-a06

Fit the two rings into the base and glue them down. Thread the spacer into position glue it and clamp it into position at the top of the ring.planet-a07

Assembling the Parts from Planetary1

The larger gear has eighteen teeth. You will need a dowel 12mm diameter x 15mm long
Thread and glue the three gears to the dowel and centre them along the length of the dowel. Use the small arrow to help accurately line up the teeth.planet-a08

The two spacer pieces have a slightly larger centre hole than the holes in the gears. Glue them onto one side of the gear.planet-a09

Carefully clamp them up as the glue dries.planet-a10

Glue and clamp the spacer side of the gear to the spider lining it up carefully with the hole in the spider.planet-a12

The small gears have twelve teeth each. The dowel is 6mm diameter x 15mm long. Glue together the three gear pieces and centre them over the dowel. planet-a11

Assemble all three in the same way.planet-a13

Drop the three small gears into the spider.planet-a14

Glue in the three spacers.planet-a15

…and fit the cover piece into place gluing it to the spacers to complete the first planetary gear module.planet-a16

Planetary gear viewed from the other side.planet-a17

Assembling the stands.pdf parts

The main gear has eighteen teeth and is made from three layers. The dowel is 12mm diameter x 55mm long. Thread and glue together the three gears onto the dowel carefully lining up the teeth. The dowel should protrude just under 3mm from the top gear.planet-a18

You will need these four parts to make the handle stand.planet-a19

Glue and clamp them together.planet-a20

The completed handle stand.planet-a21

Thread the gear into place in the stand with the five spacers fitted as in the picture.planet-a22

These parts make up the output stand.planet-a30

Front and back views of the assembled output stand are shown here. Use glue to fit the parts together.planet-a31

Making up the parts from handle.pdf

You will need a 6mm diameter dowel 36mm long. A wooden ball finishes off the handle nicely. The ball in the illustration below is a 12mm diameter beech wooden ball with a 6mm hole drilled into it. The balls can be purchased from eBay – I’ve written a blog post on drilling  holes in wooden balls here.

The handle is made from two layers. Glue and clamp then together then fit the handle to the drive shaft as shown. The remaining parts (the star and spacer) will be fitted to the output shaft later.planet-a23

Assembling the parts for planetary2.pdf

You will need the final 12mm dowel for this part. 12mm diameter x 30mm long.

There are three circular spacers in this module. Two large outer diameter (27.5mm) and one with a smaller outside diameter (25mm). Starting with the smaller spacer, line it up with the hole in the spacer and glue it down.planet-a24

 

Fit and glue the two larger spacers to the end of the dowel so that they are a flush fit. Glue the spacers and dowel to the first spacer so that they are lined up as accurately as possible. planet-a26

Make up the three twelve tooth gears as before. Drop them into place on the spider.planet-a27

Glue the three spacers into position…planet-a28

…thread the ring into position and glue it to the spacers to complete the second planetary gear.planet-a29

Final Assembly of the Parts

Draw an alignment line 22.5mm from the centre of the board. Line up the edge of the ring gear base with your alignment line then screw the ring gear to the centre of the board.planet-a32

Fit the second gear assembly into the first ring gear.planet-a33

Fit the output stand over the output shaft. Screw the stand into place.planet-a34

Push fit the star onto the output shaft. This helps make the turn of the output shaft clear and visible.planet-a35

From the other side of the gear, fit the first planetary gear into place.planet-a36

Fit the input gear and handle into place in the first planetary gear…planet-a37

…and screw the stand into position.planet-a38

 

That’s it! Turn the handle and marvel as the wheels within wheels turn in beautifully harmonic synchrony!planet-a39

 

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