Assembly Conventions

Read bolt sizes and counts, measure Socket and Flat bolts, and follow the threadlocker, tightening, and soldering guidance.

Bolt Names and Counts

The manual uses compact bolt names such as and .

M3 is the metric thread size: a nominal thread diameter of 3 mm.

x8 means an 8 mm bolt length. The starting point for this measurement depends on the head type, as explained below.

Socket has a raised cylindrical head. Flat has a countersunk head with a tapered underside that fits into a matching recess.

For example, "Take 4 of " means select four bolts of that size and type. Use "of" for every count, including one: "Take 1 of ." Parts tables use a singular bolt name and put the quantity in the Count column.

Orange, dotted-underlined bolt names open a 3D preview on click or tap. A bolt name without an underline has no verified preview yet. Use the preview to recognize the head shape, not to judge the bolt's length on screen.

Measuring Bolt Length

Use a ruler or caliper and measure in millimetres. Start at the ruler's zero mark, not the edge of the ruler.

Type	Measure from	Measure to	Include the head?
Socket	The flat underside of the head, where it meets the shaft	The end of the bolt	No
Flat	The flat top surface of the countersunk head	The end of the bolt	Yes

Socket Bolts

Measure from under the head to the end of the bolt. Include any unthreaded shaft, but exclude the head itself; do not measure only the threaded section. A measures 8 mm under the head, so its overall length is longer than 8 mm.

Flat Bolts

Measure the entire bolt, including the head, from its flat top surface to the end. A measures 12 mm overall.

Check the head type as well as the size

Socket and Flat bolts of the same thread size and listed length are not interchangeable. Check the head type and measure the length before installation. Do not force a bolt that does not fit, or substitute a different length to make it fit.

Threadlocker

Cut the nozzle tip, squeeze a small pool of threadlocker into the bottle cap, then wipe the bolt threads through it rather than dripping straight from the bottle. That is the easiest way to keep the amount under control. The video below walks through the whole process.

Applying threadlocker to a bolt

Only apply threadlocker once you are certain the joint is correct

Threadlocker is very hard to undo. If you apply it to a bolt that turns out to be in the wrong hole, the wrong orientation, or the wrong part, you may not be able to back that bolt out again.

You can assemble the whole robot without threadlocker. Leaving it off does not stop the robot going together — it just makes the joints more likely to rattle loose over time. So if you are still checking fit, alignment, or orientation, assemble dry first, confirm everything is right, then remove the bolts in a star formation, apply threadlocker, and retighten.

Use less threadlocker on M3 screws

From M4 upwards, one drop is the right amount. M3 screws need slightly less than that, so do not let a full drop land on one.

Excess threadlocker spreads past the threads and makes the screw much harder to back out later.

Use heat to free a threadlocked bolt

If you have already applied threadlocker and need to remove a bolt, heat the bolt head with a soldering iron or similar for a few seconds. The heat softens the threadlocker and the bolt will turn out far more easily than forcing it cold.

Keep the heat on the bolt head only, and keep it away from printed plastic parts, cables, and actuators.

Over-tightening

Never use an electric screwdriver on M3 screws or smaller

The M3 hex screws are small, and an electric screwdriver rounds out the head. Electric screwdrivers are prohibited on M3 and smaller — turn those by hand.

More generally, avoid an electric screwdriver altogether unless you know the tool well and can control its torque. A hand tool is slower, but it is far harder to strip a head or a thread with one. If you are unsure, use hand tools. See Tools for the recommended set.

Solder

Some steps join cable leads by soldering them together, and the head needs a power cable made from XT30 connectors and wire. Use the videos below as the reference for both techniques. See Tools for the soldering iron, solder, heat-shrink tubing, and fume extraction we use.

Slide heat-shrink tubing on before you solder

Once a joint is soldered, you cannot fit tubing over it. Slide heat-shrink tubing onto the wire first, then shrink it over the finished joint so no bare metal is exposed.

Soldering a Wire Joint

Where a step asks you to solder the leads routed from one actuator to the leads of another, join each corresponding conductor following the released pinout. Match each wire to its counterpart before you heat anything; a swapped or poorly made joint can break power or degrade the CAN signal between actuators.

How to solder two wires together

After each joint cools, tug it gently to confirm it holds, then shrink the tubing over it.

Making an XT30 Power Cable

The 1000 mm XT30-Male to XT30-Female power cable that powers the is made during Head Compute Unit Setup from 1 XT30-Male connector, 1 XT30-Female connector, and 2 wires of 1000 mm. Solder one wire to each connector terminal as shown in the video below.

How to build a custom XT30 cable - Josh Pieper

Match + to + and − to −

Reversing the polarity of a power cable can permanently damage the board it powers.

Each XT30 connector has a + and a − marking on its housing. Check them before soldering.
One wire must join + to + and the other must join − to −. Never connect + on one connector to − on the other.
If your wires are red and black, use red for + and black for − on both connectors.
When both ends are done, check that each wire runs between matching markings. If you have a multimeter, use continuity mode to confirm + to + and − to −, and that + and − are not shorted together.

The actuator XT30 (2+2) cables are separate cables that carry both power and CAN signals. Do not make substitutes for them from XT30 power connectors.

On this page