Use: the crate is going to be used by local farmers (up to 25-30kg). Thus, we want it to be durable, light and easy to fold and unfold. It should also provide some aeration to the good inside. Folded crates should fit into each other for easy stacking.
The parts of the crate are going to be produced with a compression machine with 35x47x41 cm3 (height x length x width) size. Thus, the mould´s size cannot exceed that. We use a dremel for the finishing.
To mould should be producible by local artisan: The mould should be produced with locally available low tech (welding, cutting) and materials (steel mainly)
Output: .dxf, .pdf and an editable document (preferably one that can be edited with OS software like FreeCAD)
Test: Hinges
We tested the “basic” set up with a metal stick:
We performed a fatigue test where we released a 10kg bottle on the crate which was hanging from its 2 handles. After 1:40 one of the side sheets where the handles are placed broke due to the downward force of the metal stick.
Learnings: that hinge is the weakest. The side sheet is not produced with a mould (not ready yet); hence, it is understandable that it brakes. I would recommend that the side sheets (the ones with the handles) have two ”projections” instead of just one.
We performed a static test where we added up to 40kg on top of the crate which was hanging from the 4 side hinges.
The crate withstood that weight for around 2 hours, until the bottles fell to the floor due to the wind.
Learnings: The bottom part of the crate can hold 40kg. The weakest points are the 8 projections that are usually attached to the side sheets with handles. As it can be observed in the pictures below some cracks appeared. I would recommend making these projections wider and making sure that enough plastic is added in those areas before melting.
Finally another static test was performed: I hung from the crate (60kg) and it broke immediately.
As expected from the previous tests one of the projections broke. Same recommendation as before.
Limitations of the tests. I used ropes to hang the crate. It is likely that the crate was not perfectly horizontal; thus, some hinges (projections) might have received more force than others. This limitation puts us in the “safe side” since under normal use conditions the crate will be held with both handles, meaning that all 4 hinges will withstand the same force. In the worst case only one handle will be used and two hinges will withstand all the force.
Design review
A drop taste and fatigue test were performed on the crates to ascertain the weakest parts. It was determined that the weakest part was the hinges.
On the side panels the hinges were very weak and a recommendation to add the number of projections was made.
On the bottom panel:
When 10kg was added to the bottom panel hanging on the hinges. It can be observed that there is slight curvature on the panel.
It is assumed that the panel was able to withstand the weight.
With 20kg it can be observed that uniform weight distribution did not bulge the panel further.
It is assumed that the panel was able to withstand the weight.
With 30kg it can be observed that there is further bulging.
With 40kg we can see the bulging is at it max.
It is reported that the crate withstood that weight for around 2 hours, until the bottles fell to the floor due to the wind.
Recommendation
Making the projections wider and making sure that enough plastic is added in those areas before melting.
Adding more projections to distribute the weight.
Computer Simulation
This makes it easy to analyse the weakest point and the reaction due to forces without having to fabricate the product. The analysis was done with a 40kg weight distributed force on the face of the plate. The fixed points were the longer hinges just as done in the physical experiment.
Stress analysis
It can be observed that the hinges receive mass stress and the red section shows where max stress is received. This confirms the experimental results.
Displacement analysis
The displacement also confirms experimental results.
Strain analysis
Similar results can be seen confirming we have to strengthen the hinges or distribute the hinges location.
Analysis with all hinges used.
Stress analysis
This analysis suggests that we could probably reduce the stress on the crate hinges by using all the provided hinges.
This seems a more realistic way of doing the analysis since once the crate is assembled all the hinges will share the weight.
Displacement analysis
There seems to still be more displacement in the middle which suggests probably we need to move the hinges towards the middle or reinforce the middle.
Strain analysis
Personal recommendation
A test to be redone with all hinges used and results recorded for further analysis.
A load of 10kg to be added progressively until breaking point.
Test 2: Hinges
All tests run for at least 30 minutes.
10 kg
20 kg
25 kg
30 kg
50 kg
Bahati hang on the crate for some seconds and nothing happened
60kg
Unai hang on the crate for some seconds and nothing happened
Conclusions
Nothing broke, the hinges withstood the weight. No damage has been observed and the sheet did not bend during the test.
Customers
1 complaint about the price of bamboo crates (10000-15000)
In case of accident (bodaboda) a lot of veggies and crate get broken
After long distance transport products decay
Bamboo crates get roten by microorganisms
Aeration is needed
The current size 50x40x30 and I think it could be good.
It would be nice if the whole crate had the same colour
Mettodo
commented
2 years ago
Mould & product
Specs
Use: the crate is going to be used by local farmers (up to 25-30kg). Thus, we want it to be durable, light and easy to fold and unfold. It should also provide some aeration to the good inside. Folded crates should fit into each other for easy stacking.
The parts of the crate are going to be produced with a compression machine with 35x47x41 cm3 (height x length x width) size. Thus, the mould´s size cannot exceed that. We use a dremel for the finishing.
To mould should be producible by local artisan: The mould should be produced with locally available low tech (welding, cutting) and materials (steel mainly)
Output: .dxf, .pdf and an editable document (preferably one that can be edited with OS software like FreeCAD)
Test: Hinges
We tested the “basic” set up with a metal stick:
We performed a fatigue test where we released a 10kg bottle on the crate which was hanging from its 2 handles. After 1:40 one of the side sheets where the handles are placed broke due to the downward force of the metal stick.
The crate withstood that weight for around 2 hours, until the bottles fell to the floor due to the wind. Learnings: The bottom part of the crate can hold 40kg. The weakest points are the 8 projections that are usually attached to the side sheets with handles. As it can be observed in the pictures below some cracks appeared. I would recommend making these projections wider and making sure that enough plastic is added in those areas before melting.
Finally another static test was performed: I hung from the crate (60kg) and it broke immediately.
As expected from the previous tests one of the projections broke. Same recommendation as before.
Limitations of the tests. I used ropes to hang the crate. It is likely that the crate was not perfectly horizontal; thus, some hinges (projections) might have received more force than others. This limitation puts us in the “safe side” since under normal use conditions the crate will be held with both handles, meaning that all 4 hinges will withstand the same force. In the worst case only one handle will be used and two hinges will withstand all the force.
Design review
A drop taste and fatigue test were performed on the crates to ascertain the weakest parts. It was determined that the weakest part was the hinges. On the side panels the hinges were very weak and a recommendation to add the number of projections was made. On the bottom panel:
When 10kg was added to the bottom panel hanging on the hinges. It can be observed that there is slight curvature on the panel. It is assumed that the panel was able to withstand the weight.
With 20kg it can be observed that uniform weight distribution did not bulge the panel further. It is assumed that the panel was able to withstand the weight.
With 30kg it can be observed that there is further bulging.
With 40kg we can see the bulging is at it max. It is reported that the crate withstood that weight for around 2 hours, until the bottles fell to the floor due to the wind.
Recommendation
Making the projections wider and making sure that enough plastic is added in those areas before melting. Adding more projections to distribute the weight.
Computer Simulation
This makes it easy to analyse the weakest point and the reaction due to forces without having to fabricate the product. The analysis was done with a 40kg weight distributed force on the face of the plate. The fixed points were the longer hinges just as done in the physical experiment.
Stress analysis
It can be observed that the hinges receive mass stress and the red section shows where max stress is received. This confirms the experimental results.
Displacement analysis
The displacement also confirms experimental results.
Strain analysis
Similar results can be seen confirming we have to strengthen the hinges or distribute the hinges location.
Analysis with all hinges used.
Stress analysis
This analysis suggests that we could probably reduce the stress on the crate hinges by using all the provided hinges. This seems a more realistic way of doing the analysis since once the crate is assembled all the hinges will share the weight.
Displacement analysis
There seems to still be more displacement in the middle which suggests probably we need to move the hinges towards the middle or reinforce the middle.
Strain analysis
Personal recommendation
A test to be redone with all hinges used and results recorded for further analysis. A load of 10kg to be added progressively until breaking point.
Test 2: Hinges
All tests run for at least 30 minutes.
10 kg
20 kg
25 kg
30 kg
50 kg
Bahati hang on the crate for some seconds and nothing happened
60kg
Unai hang on the crate for some seconds and nothing happened
Conclusions
Nothing broke, the hinges withstood the weight. No damage has been observed and the sheet did not bend during the test.
Customers
Test