Author:Keith V. Alexander

Keith V. Alexander is a professor of engineering at the University of Canterbury in New Zealand.

By replacing traditional metal springs with flexible composite rods and using a soft-edge design, he significantly reduced injuries caused by impacts with hard frame structures. His innovation made him a pioneer in trampoline safety design and helped transform industry standards and product development worldwide.

What Is The Weight Capacity Of A Trampoline？

Definition and importance:

We often say that “trampoline load-bearing capacity” does not refer to the trampoline can withstand the maximum static weight. It has a more central definition: the maximum total weight that the trampoline can safely withstand when it is designed and manufactured, which includes the weight of the jumper itself and the dynamic impact generated during the jump.

Why is this so important? Because it is directly related to the safety of the user, the service life of the trampoline, and the avoidance of potential structural damage. If the upper limit of the trampoline is exceeded, the wear of the trampoline components will be accelerated, and the weight may cause the trampoline frame to bend, the spring to break, and even the risk of the user falling.

1.2 Static vs  Dynamic load-bearing:

 There is an often confused concept here, which is static and dynamic load-bearing.

 Static load-bearing: refers to the maximum weight that a trampoline can bear while still. For example, if you put a weight gently on the surface of a trampoline, the weight it can bear. This value is usually relatively high.

 Dynamic load-bearing: that’s what we really need to pay attention to when actually using a trampoline. When you jump, the momentary impact you produce on the trampoline is much greater than your actual weight, due to the effects of gravity and acceleration. As an example, when a person weighing 100 kg jumps, depending on the height and manner of the jump, the instantaneous impact force he exerts on the trampoline, which is what we call the G force, may easily exceed 200 kg, or even 300 kg.

That is why we always emphasize dynamic load-bearing as a more critical safety indicator. When manufacturers mark load-bearing capacity, they usually refer to dynamic load-bearing, but consumers tend to misunderstand it as static load-bearing, which requires special attention.

 So, when choosing a trampoline, don’t just look at one number, but understand the science behind it. After all, safety is what makes us enjoy trampolining.

Key Factors Affecting The Weight Capacity Of Trampoline

Trampoline load-bearing capacity, is not only a number so simple. It is determined by a series of design and material choices. In my opinion, understanding these core factors is the basis for choosing the safe and durable trampoline.

Frame structure and materials

The framework of the trampoline is the most direct determinant of load-bearing capacity.

Material: High-quality steel is preferred. Specifically, galvanized steel is what I ‘ve always recommend. Its advantage is that it not only has high strength and can effectively resist the impact of jumping, but more importantly, its galvanizing treatment can effectively prevent corrosion and rust. Trampolines are often placed outdoors, wind and sun, if there is no good anti-corrosion ability, no matter how strong the steel can not stand the test of time.

Pipe wall thickness and diameter: The thickness and diameter of the frame pipe directly determine its bending and compression resistance. trampoline with good load-bearing capacity, the frame pipe is usually thicker and larger in diameter, which can provide greater structural stability and reduce the risk of deformation caused by frequent use. I have seen some low-priced trampolines, the frame pipe is as thin as paper, that kind of product, I personally will never recommend to my family.

Welding quality: no matter how good the material is, if the connection is not firm, it will be useless. High quality welds are critical to the structural integrity of the frame. I often observe the solder joints of the trampoline carefully. They should be uniform, firm, and have no obvious pores or cracks. Good welding ensures that the parts are tightly connected and that the impact of the jump is evenly distributed, rather than concentrated at a weak point.

Number, length and mass of springs

 Quantity: A simple rule of thumb is this: more springs usually means better weight distribution and load-bearing capacity. The greater the number of springs, the less load each spring will have to bear, extending its life and providing a smoother jumping experience.

 Length: The length of the spring affects the depth of the jump and the rebound force. Longer springs generally provide deeper, softer jumps and perform better at absorbing impact, which indirectly enhances cushioning against weight. But I personally think that excessively long springs can also cause a risk of “bottoming out”, so the length needs to match the design perfectly.

 Material and shape: Galvanized spring is standard, it can effectively resist corrosion in outdoor environment. As for the shape, there are cone springs and straight springs that are common on the market. Tapered springs provide more progressive elasticity when compressed, while straight springs may provide more direct rebound force. Both have their advantages, the key being the tensile strength and durability of their materials.

 Jumper material and weaving

 A jumper is the user’s interface in direct contact with a trampoline, and its durability directly affects safety and longevity.

 Material: High-strength polypropylene (PP) mesh cloth is currently recognized as a quality choice in the industry. Not only is it extremely durable and able to withstand repeated stretching and impact, but more importantly, it has excellent UV resistance. The sun is the biggest “killer” of the jumper cloth, which has no anti-UV function and will become brittle and crackable in less than a year or two when used outdoors.

 Weave Density: Denser weaves provide better strength and tear resistance. You can judge the density of the weave by looking at the texture of the patchwork, and the tighter the weave, usually, the better its durability.

 Stitching process: Multiple stitching and reinforcement of the edges of the patchwork is essential. The point of connection of the spring to the jumper is one of the places where the force is greatest. If the suture is not firm, it is easy to tear, leading to safety hazards. I’ve seen too many jumpers scrapped because of poor edge stitching, so this must not be overlooked.

Overall design and engineering

 In addition to specific components, the overall design philosophy of the trampoline determines its load-bearing capacity and safety.

 Leg Support System: The stability of a trampoline is largely determined by its leg design. For example, the classic “W”-shaped leg design, or the use of multi-leg support, can effectively increase the contact area at the bottom and disperse gravity, thereby greatly improving the overall stability of the trampoline and reducing the risk of rollover.

 Structural Triangle Principle: Good engineering designs skillfully apply the structural triangle principle to disperse stress. Think of those large bridge structures where triangles are the most stable geometry. In trampoline design, a reasonable connection and support structure can effectively spread the impact force generated when jumping over the entire frame instead of concentrating at one or two points. This not only increases the load-bearing capacity, but also extends the life of the trampoline.

 Brand reputation and certification: one last point, and one that I emphasize repeatedly: buy trampolines certified for international safety. In my opinion, a brand with a good reputation and certified by authority will have a product that is more secure in design and materials.

Why Is The Manufacturer’S Load-Bearing Capacity Guide Important?

 Test criteria:

And you might wonder, how did those load-bearing numbers come about? Behind this lies a series of demanding tests. When the manufacturer determines the safe load-bearing range, it performs various tests, such as cyclic stress tests, simulating thousands of jumps to see if the structure and materials of the trampoline can withstand repeated impacts over a long period of time.

There is also an extreme load-bearing test, which will be carried out well beyond the nominal load-bearing to ensure that there is also an adequate safety margin in extreme cases.

These tests are not carried out haphazardly, and they usually take into account dynamic loads ——that is, not just the weight at rest, but the instantaneous impact force produced when jumping. At the same time, a safety margin will be added to ensure that the load-bearing capacity actually used is well below the critical point of failure of its structure. It’s like you’ll buy a car with its maximum load in mind, but it usually doesn’t fill up for everyday use, always leaving room for it.

These testing standards are not decided upon unilaterally and casually by manufacturers, they tend to cite the guiding principles of industry authorities, such as ASTM International, which has clear specifications for trampoline safety load-bearing testing. It is clear to us all that following these standards is the cornerstone of ensuring product safety and reliability.

Safety and Warranty:

I must seriously point out that the potential dangers of using a trampoline beyond its load-bearing capacity are real. I have seen cases of structural failure caused by overweight, such as bending and deformation of the support rod; I have also seen spring breakage, and even more serious jumping cloth tears, which can cause the jumper to lose balance and fall from a height, resulting in fractures, Serious injuries such as head injuries.

Just imagine, when you enjoy free jumping in the air, suddenly structural failure, it will be a terrible scene.

In addition to the immediate security risks, there is another issue that is easy to overlook but equally important: use beyond the manufacturer’s guidelines will invalidate the product warranty. That’s right, once the trampoline is damaged due to overweight use, you will not be able to get free repairs or replacements. This is not only an economic loss, but also reflects the manufacturer’s expectations and responsibilities for the safe use of products.

The risk of more than people jumping:

This point I must repeatedly emphasize is also a mistake that many parents are prone to make: even if the trampoline has a high total load-bearing capacity, it is strongly not recommended that multiple people jump at the same time, especially those with obvious weight differences. This is not a problem that weight-bearing numbers can completely solve, but a combination of physics and human kinematics.

This is what experts often refer to as collision injuries. When two people jump at the same time, it is difficult for their bounce trajectory and rhythm to be completely synchronized.

One person’s descent may meet another’s ascent, resulting in an unexpected collision. If one of the children is much heavier than the other, the light child may be thrown higher by the acceleration of gravity and rebound, or even fly out of the trampoline, which is very dangerous. Even adults, two people of similar weight jump together, there is this risk, and the body is more difficult to control.

So, my advice is always the same: only allow one person to jump at a time, which is the safest thing to do. This not only protects the jumper, but also maximizes the life of the trampoline.