Bevel gear linkages

This is a system of parts that makes linkages with right-angled revolute joints. The plain links can be replaced with links with bevel gears. The bevel gears mesh with each other and interact with the linkage motion. There are two types of bevel gear: a "double-sided" version and a "far-side" version. These are compatible with each other, although whichever type of gear you put together, you need to alternate mirrored and non-mirrored versions of the gears. In the photographs, the white gears are mirrored, while the green gears are not.

Each link part is made from a linkage_shaft with a nut_cap on one end and a linkage_and_double_sided_gear_cap on the other.

Each double-sided gear is made from a double_sided_gear (or the mirror version) with a nut_cap on one end and a linkage_and_double_sided_gear_cap on the other.

Each far-side gear is made from a farside_gear_1 (or the mirror version) with a nut_cap on one end and a farside_gear_2 (or the mirror version) on the other.

The parts of either a link or a double-sided gear are held together with a 45mm M3 bolt and an M3 nut. The parts of a far-side gear are held together with a 50mm M3 bolt and an M3 nut. In all cases, the nut goes in the nut_cap part, and the bolt goes in through the other side of the link or gear.

Neighbouring gears or links are held together with a T-junction part. One of the photos shows the order in which the parts making up a (mirror) far-side gear are bolted together through a T-junction part.

All parts are intended to be printed with 0.2mm layer height. Most of the parts will need some support, although I've arranged them so that there should be no need for support on the teeth of the gears. You may need to do some post-processing to make sure that the parts move freely. My T-junction parts all needed the hole through the "crossbar" part of the "T" opened up a bit.

The assembly of the parts into a chain or loop of links or gears is unfortunately quite tricky. The reason is that the gear that goes through the "crossbar" part of the "T" of the T-junction blocks access to the M3 nut in the gear that goes through the "vertical" part of the "T".  For that reason, as a first step, it is probably a good idea to hold the M3 nut in each nut_cap part with a dab of hot glue or similar. Following this, for each gear or link part:

• Make sure that the nut_cap part can fit properly into the far_side_gear_1 or double_sided_gear (or their mirror), or linkage_shaft. The "checkerboard" patterns on the two parts should push together. If they don't, you may need to clean the prints until they do.

• Next, insert the nut_cap through the top of a T-junction part, and then push it into the gear or linkage part as in the previous step.

Having done the above two steps for each gear or link in your chain or loop, now start assembling the chain or loop as follows:

• Insert the free end of a gear or link into one side of the T-junction part for the next gear in the chain. Remember that gears have to alternate mirror and non-mirror versions along the chain.

• Insert a far_side_gear_2 or a linkage_and_double_sided_gear_cap (as appropriate) into the other side of the T-junction. Again the "checkerboard" patterns on the two parts should push together.

• Now insert a 50mm M3 bolt (for far-side gears) or 45mm M3 bolt (for doubled-sided gears or links) into the combined gear or link, through the far_side_gear_2 or linkage_and_double_sided_gear_cap and other parts until it tightens on the M3 nut. You may need to loosen the bolt a little if it causes friction in the movement of the gears.