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Bollard assembly

An Alliance Bollard is a piece of Pool hardware, not part of your Robot. It clamps to the top rail of the Pool frame and hangs a string over the water. Hex Links in the Alliance colour attach to the end of that string, which is what Robots score onto.

One Bollard sits in each corner of the Pool: two Blue and two Red. A complete Pool therefore needs four Bollards, and this page describes how to build one of them.

Pool layout seen from above and in perspective. A Bollard is mounted in each of the four corners of the frame, two Blue on one side and two Red on the other, each hanging a string down over the water.

Each Bollard clamps onto the pool frame at the corner, so nothing has to be drilled or permanently attached to the Pool.

Close views of a mounted Bollard. The arm clamps over the top rail of the frame at the corner, the vertical support board presses against the wall panel, and a string hangs from the end of the arm with a red Hex Link at the bottom.

What you are building

A Bollard is made of four sub-assemblies:

Part What it does
String clamp Grips the string between two small plates. Sliding it along the arm sets how far the Hex Link hangs
Diving board The horizontal arm that reaches out over the water and carries the string clamp
Support board The vertical leg that braces the arm against the Pool wall
Frame clamp The M8 screw and jaw that lock the whole Bollard onto the Pool frame

The finished Bollard from two angles: a horizontal arm with a clamp block at one end and a vertical support leg hanging below it, forming an upside-down L shape.

Parts and tools

Fasteners for one Bollard. Multiply by four for a full Pool.

Fastener Quantity
M3×8 screw 4
M3 nut 4
M4×16 screw 5
M4×20 screw 1
M4×25 screw 6
M4 nut 1
M4 nylock nut 11
M8×80 screw 1
M8 nut 1

You also need the machined plates and blocks for each sub-assembly, a length of string, hex keys for M3, M4, and M8, and spanners to hold the nuts.

Nylock nuts are not plain nuts

Most M4 nuts in this build are nylock (nylon insert) nuts. They resist vibrating loose in a wet environment. The one plain M4 nut belongs inside the string clamp in step 1, where a nylock nut will not fit. Do not swap them.

1. Assemble the string clamp

The string clamp is two small plates that close onto each other. The plain M4 nut is captured inside, and later takes the screw that tightens the clamp.

  1. Drop the 1× M4 nut into its pocket in the lower plate.
  2. Place the upper plate on top, slotted face up.
  3. Pass 4× M3×8 screws down through both plates.
  4. Fit 4× M3 nuts underneath and tighten.

Exploded view of the string clamp. Four M3x8 screws pass down through a slotted top plate and a bottom plate, with an M4 nut trapped between them and four M3 nuts underneath. The finished clamp is a small block with a slot across its top face.

Insert the M4 nut before closing the clamp

Once the two plates are screwed together, the pocket is sealed. If you forget the M4 nut you have to take the clamp apart again.

2. Assemble the diving board

The diving board is the horizontal arm. The string clamp from step 1 goes inside it, between the two long plates.

  1. Lay down the long plate with the notch facing below. The notch marks the underside of the arm.
  2. Place the string clamp and its spacer between the plates, lining the clamp slot up with the slot in the plates.
  3. Add the second long plate on top.
  4. Pass 4× M4×25 screws through the outer holes and 1× M4×20 through the slot into the M4 nut in the string clamp.
  5. Fit 4× M4 nylock nuts on the M4×25 screws and tighten.

Exploded view of the diving board. Two long plates sandwich the string clamp and a spacer, with four M4x25 screws through the corners, one M4x20 screw through the centre slot, and four M4 nylock nuts underneath. A callout marks the lower plate as the one with the notch.

Leave the M4×20 screw slightly loose for now. It is the screw you use later to set the string height.

3. Assemble the support board

The support board is the vertical leg. It is built the same way: two plates with a triangular spacer between them.

  1. Lay down the plate with the notch facing below.
  2. Place the triangular spacer on it.
  3. Add the second plate on top.
  4. Pass 3× M4×16 screws through and fit 3× M4 nylock nuts underneath.

Exploded view of the support board. Two long plates sandwich a triangular spacer, joined by three M4x16 screws and three M4 nylock nuts. A callout marks the lower plate as the one with the notch.

4. Mount the diving board

The clamp block is the part that will grip the Pool frame. The diving board slides into it.

  1. Slide the diving board into the clamp block, notched plate facing down.
  2. Pass 2× M4×25 screws up through the joint.
  3. Fit 2× M4 nylock nuts and tighten.

The clamp block sliding onto the end of the diving board, then fixed with two M4x25 screws and two M4 nylock nuts through the joint. A callout says to insert it with the notch plate facing down.

If the diving board will not slide in, check the orientation. The notch only clears the block one way round.

5. Mount the support board

  1. Slide the support board up into the clamp block below the arm, notched plate facing forward.
  2. Pass 2× M4×16 screws through the joint.
  3. Fit 2× M4 nylock nuts and tighten.

The Bollard now has its finished shape: a horizontal arm with a vertical leg under the clamp end.

The support board sliding up into the clamp block underneath the diving board, fixed with two M4x16 screws and two M4 nylock nuts. A callout says to insert it with the notch plate facing forward.

6. Fit the frame clamp

The last two parts turn the block into a clamp that closes onto the Pool frame.

  1. Place the clamp jaw over the top of the block.
  2. Pass the 1× M8×80 screw through the block and into the jaw.
  3. Fit the 1× M8 nut and run it up until the jaw is held but the clamp still opens far enough to go over the frame rail.

The clamp jaw fitted over the top of the clamp block, held by one M8x80 screw and one M8 nut. The finished Bollard is shown alongside.

The Bollard is now built.

Install it on the Pool

  1. Open the clamp far enough to pass over the top rail at a corner of the Pool.
  2. Position the Bollard so the arm reaches out over the water and the support board rests flat against the wall panel.
  3. Tighten the M8 clamp until the Bollard does not rotate or slide when you push the end of the arm.

Repeat for the other three corners, matching the Alliance colours to the correct sides of the Pool.

Set the string height

The string clamp inside the arm is what sets how far the Hex Link hangs below the Bollard.

Cutaway views of the string clamp inside the diving board arm. The string runs down between the two clamp plates, which pinch it closed. A screw at the end of the arm opens and closes the gap.

  1. Loosen the M4×20 screw. The clamp plates open and the string can slide.
  2. Pull the string through until the hanging length is right.
  3. Tighten the M4×20 screw again to pinch the string.
  4. Pull down firmly on the string to confirm it does not slip.

Check the height before every event

A string that has crept even a little changes how easily Robots can reach a Hex Link. Check all four Bollards during Pool setup, not after Matches have started. See Pool management for the rest of the Pool checklist.