About load capacity and strength loss
All load capacities are indicated by direct pull on the magnet, which means the load capacity a magnet has when in direct contact with a magnetic surface and subjected to a straight pull (learn more about glass boards here, where different rules apply). If there is a downward load on the magnet, the pull is indirect, and thus the need for load capacity must be calculated from other parameters.
This can also be explained by hanging a piece of paper versus a calendar/picture frame on your fridge or whiteboard with these two examples:
Example 1:
If you hang a piece of paper with a magnet, there is virtually no distance between the magnet surface and the magnet; thus, the magnet's capabilities are not significantly challenged. However, if you hang up 10 pieces of paper, there will be a considerable distance between the magnet and the metal surface, thereby putting more strain on the load capacity - and it is no longer a direct pull. The same applies with a bit heavier card stock: there is still not a large gap between the magnet and the metal surface, so the magnet can carry the heavier card stock without issues. But if you stack several pieces of card stock on top of each other and hang them with a magnet, there will be a significant distance to the metal surface. And thereby the magnet is no longer only challenged in direct pull.
Example 2:
If you hang a calendar (or a framed picture), there is a strong downward pull on the magnet, and this poses quite different requirements for the magnet's load capacity. In this case, consider choosing a very strong hook magnet, which can handle the downward pull. The larger the calendar (not just the weight but also the dimensions), the greater the need for load capacity. We recommend this magnet for hanging calendars that are max. A4 size: Hook-magnet ø20 mm. If the calendar is A3 size, you need a larger magnet with more strength, like the Ø25 mm. hook magnet (or bigger).
Also: if the calendar needs to hang on the fridge and you have kids in the house who often slams the refrigerator door, please consider to choose the Ø32 mm. hook magnet in stead as this bigger hook magnet can withstand the pull from the sides also, when the calendar hangs and dangles.
Contact us to learn more about hanging picture frames.
Loss of magnetism withd istance
As mentioned above, distance causes the magnetism to "weaken," regardless of whether it's paper, fabric, glass, or air between the magnet and the magnetic material or the other magnet that it needs to connect to.
At a distance of 2 mm., the load capacity is reduced to 30% of the stated strength with direct contact.
At 5 mm. distance, we're down to 8% of the original strength capacity measured in direct pull.
Therefore, it is most optimal to ensure that there is as little distance as possible between magnets or magnet and magnetic material to fully utilize the magnetic field. This is especially important to keep in mind when looking for magnets for magnetic glass boards or if you are venturing to make a magnetic knife strip yourself.
Optimal conditions for magnetism
When talking about load capacity/strength, it is about the magnet's performance under optimal conditions. Here, it's important to know a bit about the conditions that apply. So do not hesitate to contact us when in doubt regarding need of magnetic strength / load capacity.
Direct pull / horizontal Pull
It can be a bit challenging to describe direct and indirect pulls in a way everyone can understand. But let's take the ceiling as a starting point for direct pull, i.e., mounting a magnet in a ceiling:
For example, if you want to hang a lamp in the ceiling, this mounting will occur via direct pull. You should account for the item's weight, and whether there are fluctuations (see below). As a rule of thumb, you should multiply the weight of the lamp by 2 to be safe, covering most considerations. The lamp must not fall down, and therefore it is important not to choose the exact same strength as the weight of the device.
Factors that can diminish the magnet's performance include vibrations, skewed/angled pull on the magnet, and possible building tremors (if you have premises next to a train station, right up the metro, by a heavily trafficked road, etc.). It is difficult to make rules of thumb for such things, as there is a great variation in these parameters. Light vibrations due to draft from the window can easily be managed by doubling the strength relative to the weight of the lamp. But if there are major tremors in the building or daily drafts, you will likely need to multiply by 4 or more. Feel free to contact us - we know it can be tricky to calculate.
External factors
As we touched on above, remember to consider potential external factors that can influence your strength needs. Here, the proximity of a metro station, doors opening and closing in the same room, gusts from open doors, and the like can significantly affect the magnet's performance.
If you're going to mount a magnet outdoors, you also need to take into account the wind strength it can be subjected to. This will also significantly affect the magnet's performance, and therefore we recommend that you at least multiply the object's weight by 6-8 to be entirely sure. And if it's a banner to be hung in windy conditions at a festival or during a concert, you should multiply by at least 20. There's not much joy in a banner being torn loose by a fierce gust of wind, causing a severe pull on the magnet, which can be quite impossible to calculate precisely in terms of wind direction.
If you're unsure whether you've determined the correct strength needs, you always have the option to contact us with questions.
Calculate your own strength needs
If you're up for making your own calculation, we've created a magnet calculator where you - by providing different information - can calculate several tasks yourself. Sometimes you want answers quickly when you have a project in mind, and the magnet calculator will quickly guide you in the direction of which magnet sizes you need based on potential distance and weight.
