Gears and gear boxes

Miniaturization opens-up a wide set of applications, but many interesting mechanisms are difficult to miniaturize due to to the difficulty in getting adequate parts. Small pager motors are available, but gears, axles, encoders are difficult to get. At LAMI-EPFL, we developed in 1995-99, thanks to the expertise of André Guignard, small robots down to 1 cubic centimeter around specially cut gears.

DIDEL sells a proprietary set of Module 0.3 gears (G3xx family), that still can be implemented with easily available precision machines: distances between the axle must be met with a precision of 0.02 mm.

G3xx gears - see also Microgears.pdf (Mod 0.3 and 0.2)

The G3xx gear family consists of a 12-teeth pinion, and gears with 36, 48 and 60 teeth molded in POM material.This allows for the following reduction ratios:
Pinion and one gear: 1:3 1:4 1:5
Pinion and two gears: 1:9 1:12 1:15 1:16 1:20 1:25
Gear sizes for the M360L (60 teeth light) are given next. The important parameter is the nominal diameter, equal to the module multiplied by the teeth number.

  Teeth number Nominal dia Ext diameter Length/ thickness Hole diameter Weight
G312 12 3.9 4.2 4.0 0.78 0.04
G336 36/12 10.8 11.4 3.0 0.70 0.13 0.17


48/12 14.4 15.0 3.0 0.79 0.19
G360L G360S 60/12 18.0 18.6 3.0 0.71 0.76 0.18 0.25

Theoretical distance between two M0.3 gears with N1 and N1 teeth is (N1+N2)/2 * 0.3. Practically, one needs to add some play (0.05 to 0.08mm).
Gear combination Reduction ratio Theoretical distance between axle Practical distance between axle
12/36 3 7.20 mm 7.26 -0.01 +0.02
12/48 4 9.60mm 9.66 -0.01 +0.02
12/60 5 10.80mm 10.86 -0.01 +0.02

Shafts and bearings

Gears must be inserted loose or tight on the axle with the correct diameter. POM gears have a good friction coefficient and can rotate loose on steel and brass axles. Steel axles can use brass bearings.

RMB will be pleased to provide ball bearings down to 3mm in diameter. André Guignard build at LAMI-EPFL a nice mechanism with ten 3mm bearings to move the wings of a Morpho butterfly (3mm smoovy motor from RMB).

DIDEL built another flapping wing Morpho butterfly using its Nanobird magnetic actuators. See the video (1.8 Mega)

Examples of designs


CH-1092 Belmont/Lausanne
Tel +41 21 728-6156
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Last update: 08.05.02/jc 31.1.03/us 051010 jdn