Removable and camouflaged goal project – Alexandre Leclaire & Alexandre Hercouet
The aim of the project is to create football goals for a personal football field. These goals should be movable, and should remain discreet, as they will be in a natural environment with greenery. The requirements for this project are explained in the following.
create removable and camouflaged football goals, so that they can be easily moved while remaining integrated into their environment.
Main Function (MF1):
- Football rules: Suitable for matches, goal shape with net.
Constraint Functions (CF):
- Ergonomy (CF1): Mobile, less than 70 kg for 2 persons.
- Design (CF2): Blends with surroundings, natural appearance.
- User Security (CF3): Stable when installed, no sharp edges.
- External Environment (CF4): Durable, weather-resistant materials.
- Football Ball (CF5): Endures strikes up to 100 km/h.
- Sporting Standards (CF6): Standard size (180 x 120 cm).
- Cost (CF7): Structure costs less than €70.
Responses to needs
MF1 & CF6 : To guarantee a football goal shape with net to the object, while respecting the given standard dimensions :
The selected dimensions shown in this illustration are standard. We can find the same dimensions on goals sold by sports equipment manufacturers.
CF1 & CF4 : Ergonomics and weight of the set, as well as resistance to the external environment :
For weight, ergonomics and outdoor strength, PVC hollow pipes were chosen. This allows for a structure that is not too heavy and that can withstand the test of time. It also allows the use of standard fittings and pipe sizes, which are easy to find on the market.
CF2 : To give the ensemble a natural appearance so that it can remain discreet in its environment.
In order to camouflage the whole, without having too many constraints in terms of weight and maintenance, the choice was made to use artificial plants like the ones shown below. This gives a natural look to the football goal, in addition to the use of PVC tubes which can be painted in a more natural colour.
CF3 : Ensuring user safety
The use of PVC pipe and matching fittings removes any potential sharp edges that may have been present on the assembly. Weights or sardines can also be used to help secure the goal from tipping over.
CF5 : Dimensioning of the football goal structure in the case of a ball impact in the context of a football match :
- Mass of the ball : m = 450g
- Maximum speed of a ball (professional record) : v = 100 km/h = 27.8 m/s
- Ball impact time (approximate) : t = 8ms
- Acceleration of the ball on impact : a = v / t = 27.8 / 0.008 = 1563.75 m/s²
- Impact force of the ball : f = m * a = 0.450 * 1563.75 = 703.7 N
Diagram of the resistance problem on the transversal bar :
After obtaining these results, numerical simulations were performed to see if the chosen material could withstand the previously calculated impact force.
The results can be seen on the following page.
In the illustration above, we can see that the 50mm diameter, 1.80m long tube can withstand an impact force of a football thrown at 100 km/h.
Indeed, the forces are below the critical threshold of 35×10 Pa (which is equivalent to the bending strength of the material). The only violations of this limit are calculation errors in the software, which can be ignored. The material can resist the force.
CF7 : To guarantee a material cost lower than 70 € for the realization of the structure.
Here is a goal with the same dimensions sold by a sports equipment manufacturer :
This goal costs 70€ each, or 140€ for 2 units.
Here are the production costs of a goal sized for this project:
- The set of connection parts = 20 €
- The green paint = 16 €.
- 20 meters of PVC pipe diameter 50 for 2 goals ≈ 80 €
- Use of a larger net to cover the 2 goals = 27.5 €
- All artificial plants used to camouflage = 66.18 €
TOTAL = 209.68 € (104.84€ per units)
The surplus compared to a goal sold by a sports equipment manufacturer (seen above) is due to the addition of artificial plant and paint for the camouflage of the goals.
List of required parts
Tube dimensions : outer diameter Ø50mm / thickness 2,4mm
Length required :
- 1.80m x2
- 1.35m x3
- 1.20m x2
- 0.60m x2
Total : 11.25 m x2 for 2 goals
90° PVC connection
6x 90° PVC female-female fitting, for Ø50 pipe x2 for 2 goals = 12
6x T-fitting PVC female-female, for Ø50 pipe x2 for 2 goals = 12
(and for Nick : 2x 90° PVC female-female fitting, for Ø50 pipe)
History of the different versions of the goal
Here is the first prototype of the goal, which represents the structure of the latter, in PVC tube
Here is the first version of the paintless goal on PVC pipe. We can see artificial plants on the net, solutions that will not be retained for the final version.
Here is the latest version of the goal, with paint on the structure, a green net installed and artificial plants installed only on the goal uprights.