Grade 8 technology project: how to build a mine shaft headgear, step by step

The mine shaft headgear is the Grade 8 Technology project about frame structures. It is the tall frame that stands over a mine shaft and lifts the cage up and down, and the reason it gets set as a school project is that every part of it is doing a job you can point at and explain.

This guide covers what the real thing does, the order the model goes together, and the part the marks are actually for — being able to say why it is built that way.

Watch the whole build first

Two and a half minutes, every part going on in order. It is worth watching once before you open the box, because a frame structure is much easier to assemble when you already know what the finished shape looks like.

What a mine headgear actually is

A mine shaft is a vertical hole in the ground. The headgear is the frame built over the top of it. At the very top sits a large grooved wheel called a sheave. A steel rope runs from a winding drum on the ground, up the frame, over the sheave, and then straight down the shaft to the cage that carries miners and rock.

So the headgear is doing two jobs at the same time:

• It holds the sheave high enough that the cage can come right up out of the shaft and still have room to clear it.
• It carries the entire pull of a loaded rope — which on a real mine is many tonnes — safely down into the ground.

Everything else about the shape follows from those two jobs. That is the sentence to build your whole write-up around.

What is in the kit

The Slotbok mine headgear kit is cut by laser from 3 mm MDF or plywood. The parts come flat and labelled, and they slot together.

• A flat base — the ground the whole model stands on
• The head frame: the tall slot-together panels that make the tower itself
• An angled back-stay, with a triangulated lattice running up it
• A ladder up one side of the frame
• The sheave wheel, and the curved housing it turns in at the top
• A winder on the base — two spoked wheels, a drum between them, and a crank handle
• Thread, which runs from the drum up and over the sheave

The build order

It goes together from the ground up. The order matters more than it does on a glued model, because a slot-together frame only becomes rigid once it is closed — a half-built headgear feels alarmingly floppy, and then suddenly does not.

1. The base. Everything registers off it, so get it flat and square before anything else goes on.
2. The head frame. The tall panels and the cross members between them. At this stage it will lean if you let go of it — that is expected.
3. The back-stay. The angled leg with the lattice. This is the part that stops the leaning, and the moment it goes in the model stands on its own.
4. The ladder. Detail rather than structure, but it is what makes the model read as a mine and not just a tower.
5. The sheave and its housing. Check it spins freely before you go further. A sheave that binds will drag the thread instead of letting it run.
6. The winder. The two spoked wheels, the drum and the crank, mounted on the base.
7. The thread. Tie it to the drum, run it up and over the sheave, and wind a couple of turns on so it does not slip the first time you crank it.

Why it is built that way

This is the section the marks are for. The model is the easy part; the explanation is what is being assessed.

It is a frame, not a solid tower

A solid column that tall would need an enormous amount of material, and most of that material would be sitting there doing nothing. A frame keeps material only where the forces actually run, so it gets nearly the same stiffness for a small fraction of the weight. Every real headgear in the world is built this way for exactly that reason.

The triangles are the whole point

A square frame can be pushed over into a diamond without a single one of its sides changing length. A triangle cannot change shape at all unless one of its sides actually stretches or breaks. That is why the back-stay carries a lattice of diagonals: every diagonal you add turns a square that can fold into two triangles that cannot.

Try it on the model. Push the frame gently sideways before the back-stay goes on, and again after. Describing that difference in one sentence is the entire structures lesson.

What the back-stay is actually for

Here is the bit most learners miss, and it is the best thing you can put in a write-up.

The winder is not under the headgear. It sits off to one side. So the rope does not pull straight down — it pulls the top of the frame sideways, towards the winder, the whole time it is hoisting. Left alone, that would fold the tower over.

The back-stay leans the other way and pushes back against exactly that pull. It is the reason a real headgear is never a plain vertical tower: the shape exists because of where the winding house is. Point that out and you are explaining the structure rather than describing it.

What the sheave does

The sheave does not make the load lighter. What it does is change the direction of the force: you pull horizontally at the winder, and the cage moves vertically in the shaft. One wheel, turning a sideways pull into a straight lift.

Why the crank handle sticks out so far

The crank turns on a long arm; the thread winds onto a much narrower drum. That difference is mechanical advantage. Your hand travels a long way round a big circle while the rope moves a short way, and in exchange the load feels lighter. A longer crank or a thinner drum lifts more easily but takes more turns — that trade is worth a line in the report, and it is easy to demonstrate.

Struts and ties — naming the forces

Grade 8 Technology wants the right words on the right members, so walk the model and label them:

• A strut is being squashed. It is in compression. The legs and the back-stay are struts.
• A tie is being stretched. It is in tension. The thread is the clearest tie on the model — you can see it go taut.

A good test in your write-up: for each main member, say whether it is being pushed or pulled, and how you could tell.

What to write down while you build

Most of the marks on a Technology mini PAT are not for the model — they are for showing what you did and what you worked out. Note these as you go, and you will not have to reconstruct them afterwards:

• How far the frame leans when you push it before the back-stay goes on, and after. One sentence on the difference.
• How many triangles you can count in the finished frame.
• Which way the rope pulls the top of the tower, and which member resists it.
• How many turns of the crank it takes to raise the thread a measured distance.
• Where the model is weakest, and what you would change if you built it a second time.
• Anything that went wrong and what you did about it. This is the easiest part of a report to write and the one most learners leave out.

A photograph at the end of each stage is the simplest way to have material for the write-up without stopping to take notes.

One thing worth saying plainly: copying someone else's answers for a mini PAT is the one way to lose marks you had already earned. Everything above is here so you can explain your own model in your own words.

Afrikaans terme

If you are doing this project in Afrikaans: Graad 8 Tegnologie (Grade 8 Technology) · skoolprojek (school project) · mynskag (mine shaft) · raamwerkstruktuur (frame structure) · hystoring (headgear / hoist tower).

Get the kit

The kit is cut in our own workshop in Gauteng, and every design is built once by hand before it is packed, so the slots and tabs are known to fit.

• Mine Headgear School Project Kit — Grade 8
• All Grade 8 Technology projects
• The cell phone tower build guide, if you want another frame-structure project to compare it with

Questions about a kit, a class set or delivery to your town: message us on WhatsApp.