Crane’s Balance

3- Development of a manufacturing project
Authors : Hélène Merle(plus d'infos)
Muriel Guedj(plus d'infos)
Summary :
Discovery of specifications. Creation and implementation of a plan and a sheet detailing the stages of production, taking constraints into account.
Publication : 1 February 2004
Objectives :
Procedure goals: learning mapping, anticipating construction actions, taking into account technical constraints. Know-how goal: write a technical sheet
Material :

For each group of pupils:
a “specifications? statement” sheet,  a large poster per group.
For the classroom:
the materials quoted in the specifications, bearing a label indicating its name.

Pedagogical approach


The challenge

Available materials and tools

Reminder of the object’s use:

“The crane is a construction machine that can lift and move loads along a linear or circular path.”
The scale model of the crane will lift loads vertically (vertical translation of the hook) and move in a circular path (rotation of the arrow), and then deposit them.

Eventually, we will provide more distance from the load of the mast to the crane (carriage movement).

Details on function:

- the mass of load to be lifted and moved will be 500 grams.

- the size of the crane must not exceed 45 cm in height (mast, jib, and base included).

Time constraint:
the crane will be manufactured in two one and a half hour sessions.

Financial constraint:
the crane will have to be manufactured at a low cost.


A: wooden tile of 20mm

B: a wooden board of 200x200mm square and 10mm thick

C: spikes and wood screws with a length of 100mm and a diameter 3 to 3.5 mm (a non-threaded part of at least 20mm should be removed from the head of the screw)

D: spikes with a length of 30mm and a diameter of 1.5mm

E: a reel fishing line in 20/100 (approximately 2 to 2.5 kg of resistance)

F: red stones or bricks (such as BBQ bricks)

G: fencing (type of spike in “U” shape)

H: metal washers (with a diameter of 20mm and a hole  of 3.5 to 4mm)

I:   a hook

J: wood glue

K: electrical wire with a thickness of 4mm

L: small curtain rod rings that can be screwed

M: a matchbox

N: plaster (or cement and sand)


Tools for the children
-    a handsaw 
-    clamps and a vise
-    hammer 
-    screwdriver
-    a ruler
-    a carpenter’s square
-    a file and sandpaper
-    a gimlet
-    cutting pliers.


Tools for the teacher:

-           a drill and wood drill bits (a standard box, from 3 to 10mm in diameter)





1. Individual: read the specifications   Make sure that the constraints are well understood.

2. Group work: make a labelled diagram and a construction sheet.

Changes to the previous individual drawings of past sessions.
The pupils in each group list equipment they need and draw a diagram of the crane they want to make. They specify the stages of manufacture.

Encourage pupils to provide accurate information, in particular on the material and dimensions.
Guide them on the diagram as they tend to produce drawings.
3. Collectively:
Display of the diagrams and presentations by the different groups for the purpose of mutual enrichment

The teacher will highlight the issues raised and suggested solutions.


Word from La main à la pâte

It is in fact possible to communicate only the constraints of the “challenge” and not give details on the name (and the spelling) of materials used until the need arises. Everything depends on the children’s habit in engaging in technological activities. The list of materials induces a certain realization.


Dans cette fiche vous insistez sur la précision : inciter les élèves à donner des informations précises sur le matériel et les dimensions en particulier. J'avais aussi donné de l'importance à cette idée, en en faisant une situation de communication vraie. Les élèves devaient rédiger la commande de leurs matériaux, à laquelle j'avais répondu en stricte application des textes réalisés. Ici, cette précision n'est-elle pas dans le seul dessin dans la mesure où la liste des matériaux (avec les dimensions précises) figure dans le cahier des charges ?