Trampolines from oztrampolines online are dangerous. Don't buy them.
Here is my experience.
In March of 2014 bought a 7 x 10ft Rectangular Trampoline from Oztrampolines online. It was delivered fairly promptly but when I got it here is a picture of what I got.
Actually a 6ft x 9 ft trampoline with an extra rail 1 foot around the outside. But this is just disappointing not dangerous. The legs are complicated and not especially stable, but again not dangerous, just annoying.
From about 18 months after I got the trampoline, the springs started breaking. They would snap and would fly off and hit the person on the trampoline causing at least bruising. Thank goodness they haven't hit anyone in the head or eye yet. This continued on and off since.
5 or 6 have broken this way. I complained to oztrampolines online and they said that the trampoline had a five year warranty but the springs had only a two year warranty and they would sell me a new set of springs cheaply. Presumably with a two year warranty. The complaints went on for a while and they would say: did you install the springs the right way round? Yes I had. Did you have the guard pads installed? Yes I did.
Everyone seems to believe oztrampolines when they say that the spring guard pads should stop this happening but the physics is quite clear, the pads stop someone landing on the springs and hurting themselves, but they don't stop the springs flying off and hitting the person on the trampoline.
I went to my government consumer group to dispute the fact that the trampoline I bought was not fit for purpose, but they wouldn't take it any further. I tried the checkout but they weren't interested.
A friend had an idea to put cable ties on the springs to stop them flying off. We did that but they don't work as it has just happened again.
I am now throwing the trampoline out as I believe it is unsafe to use as a trampoline.
1. Who sells dodgy springs in trampolines that break? I have owned trampolines that are decades old that no spring has ever broken.
2. These springs all break at a similar point, the frame side hook.
The physics: When you are at the bottom of a trampoline jump, your feet or what ever part of you is contacting the mat are well below the level of the frame. The mat applies something like 7G* of acceleration to you at the lowest point. That is the time the springs have the most force on them, and are most likely to break. It is also the time when the springs are below and not touching the guard pads. If the springs break at the frame side or anywhere in the middle, the part that is on the mat side will be propelled in the direction of the force, ie towards the person on the mat.
You can clearly see in this picture how the guard mat does not cover the springs at the bottom of a jump.
*http://iopscience.iop.org/article/10.1088/0031-9120/50/1/64/meta
Here is a sketch of the forces at the bottom of a jump:
And the forces on a spring:
You can see that the guard pad does not cover the spring any more. If the spring breaks before the person reaches the bottom of a jump the force that caused the spring to break will launch the spring above the mat. In the lower picture you can also see that the hook on the mat when it
hits the mat side of the triangular clip will be launched upwards.
Here is my experience.
In March of 2014 bought a 7 x 10ft Rectangular Trampoline from Oztrampolines online. It was delivered fairly promptly but when I got it here is a picture of what I got.
From about 18 months after I got the trampoline, the springs started breaking. They would snap and would fly off and hit the person on the trampoline causing at least bruising. Thank goodness they haven't hit anyone in the head or eye yet. This continued on and off since.
Everyone seems to believe oztrampolines when they say that the spring guard pads should stop this happening but the physics is quite clear, the pads stop someone landing on the springs and hurting themselves, but they don't stop the springs flying off and hitting the person on the trampoline.
I went to my government consumer group to dispute the fact that the trampoline I bought was not fit for purpose, but they wouldn't take it any further. I tried the checkout but they weren't interested.
A friend had an idea to put cable ties on the springs to stop them flying off. We did that but they don't work as it has just happened again.
I am now throwing the trampoline out as I believe it is unsafe to use as a trampoline.
1. Who sells dodgy springs in trampolines that break? I have owned trampolines that are decades old that no spring has ever broken.
2. These springs all break at a similar point, the frame side hook.
The physics: When you are at the bottom of a trampoline jump, your feet or what ever part of you is contacting the mat are well below the level of the frame. The mat applies something like 7G* of acceleration to you at the lowest point. That is the time the springs have the most force on them, and are most likely to break. It is also the time when the springs are below and not touching the guard pads. If the springs break at the frame side or anywhere in the middle, the part that is on the mat side will be propelled in the direction of the force, ie towards the person on the mat.
 |
| http://iopscience.iop.org/article/10.1088/0031-9120/50/1/64/meta |
*http://iopscience.iop.org/article/10.1088/0031-9120/50/1/64/meta
Here is a sketch of the forces at the bottom of a jump:
And the forces on a spring:
