dry bong

We wondered, is there a way we can get more magnetic field through the steel without resorting to an even bigger, more expensive magnet? It was inspired by our experience making a Magnetic Knife Holder, where a row of magnets were placed side by side. If the first magnet has the north pole facing up, the next has the south pole facing up. We found that the magnetic field was especially strong (concentrated?) at a location right where the two magnets meet.

First, we tried a pair of B842 block magnets (1/2” x ¼” x 1/8”) side by side. It offered a really nice pull force, much better than the 1/8” thick D82 disc. Next, we tried a 2x2 array of four B442 magnets, which worked even better. It’s a great amount of pull force that uses less magnet, so it is more cost effective than a similar feeling DA4 or DC4 magnet. We also tried a 2x2 array of larger B642 magnets, which was quite strong. Force required to slide jar down (lb) 3/8” x ¼” x 1/8” blocks. In each case, the poles facing up alternates, north and south. See the video at the bottom of this article to see us assembling them. Are we a bunch of magnetic geniuses to come up with something this simple but effective?

Closer examination of some of the photos we've seen shows that many folks are actually using more than one magnet underneath the lid. Most commonly, we saw two disc magnets arranged side-by-side. While not as slick as our blocks, two discs can work well. We tried two D82 magnets arranged side-by-side under the lid, which also performed well. You might also experiment with other magnets sizes and combinations. Using at least two magnets in a side-by-side arrangement seems the way to go. The largest size jar we found in this style holds 9oz., and requires more magnetic strength to hold when full. We tried a single DC4 magnet, which failed to hold it up. A pair of DC4 magnets side by side worked well enough. The best solution was four B882 magnets arranged in a 2x2 square. While putting together some photos for this article, we noticed that many of our spices at home came in 4oz jars. We found that a single DA4 disc magnet was a bit light on strength, but held. Again resorting to an array of magnets, the four B442 magnets held. For this larger size, though, the larger B642 magnets had a better, more secure feel. For the small, 1.5oz jars, use four B442 magnets arranged in a 2x2 array. For the larger 4oz jars, use four B642 magnets in the same 2x2 array. For 6oz jars, four B662 or B862 magnets worked well, again in a 2x2 array. For the biggest, 9oz jars, use four B882 magnets in a 2x2 array. While experimenting with placing magnets on the inside of the lid, we never bothered with any glue. The magnets stuck to the inside of the lid pretty well, and stayed in place while sticking the whole thing to the fridge. This wasn’t true when you stick a magnet on top of the lid. When you stick a jar with a magnet on the lid to the fridge, the magnet will tend to stay stuck to the fridge. When you pull the jar off, the magnet stays stuck to the fridge. It doesn’t seem nearly as nice as a solution where the magnet stays with the jar.

We taped it on top of the lid for a quick prototype, but you might consider gluing it on for a more permanent solution. For more advice on adhesives, see our article: How to Glue Neodymium Magnets. The ½” diameter x 1/16” thick D81 disc held, but because of the small size of the magnet, the result was a bit wobbly. Next we tried a larger but thinner DX001 magnet, 1” diameter x 1/32” thick. The strength was nice, if a little on the weaker side. Be careful handling magnets this thin, because they are fragile.

We also found that the layer of packing tape worked better than the same magnet glued to the lid. The packing tape offers more friction on the smooth surface of the fridge.

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