Magbound holding force multiplier

[Konsba]

Hello everyone! I lurk here occasionally and decided I finally wanted to share something.

I have recently built my own version of magbound (using a similar 40 kg holding force electromagnet) and found, to my disappointment, that I could pull the metal disc off quite easily (even though I don't consider myself particularly strong). So easily, in fact, that all the common scenarios depicted on the magbound site were not secure enough for me.

I was quite disappointed by this, but luckily I have found that I can use a simple pulley system to effectively double the holding strength by pulling a rope from the magbound disc, through a rigid ring of sufficient size, and back to the magbound body (not the disc again). Then I tie myself (e.g. one of my hands) to the ring itself. When the magbound finally releases, the disc is pulled through the ring and I am free. Of course I shouldn't be able to reach the rope going through the ring because I could pull on it directly, but pulling on the ring itself should halve the force on the magbound disc and so give it double the holding strength.

It is quite secure like this, though I have found a position in which I can still pull the 80 kg if I put my all into it. But for most scenarios it is sufficient now. And more, with two such rings you can make a double pulley, tripling or quadrupling the strength... but then space, friction and tangling start being an issue. I have not yet tried a double pulley in a real scenario.

The ring should be sturdy, smooth and of sufficient size to allow the disc reliably through. I 3D-printed mine, but I imagine it should not be too hard to find.

Play safe!

EDIT: Added some photos below.

[Shannon SteelSlave]

Aloha from Bound Anna, Konsba

[TNTBound]

if your looking for a more powerful magnet, this site https://apwcompany.com/round-electromag ... dc/page/3/ is the one i used to buy my electro-magnets. i use them to keep my sleepsack secured to my bed, and when the magnet releases, i can roll over and grab the string on the zipper pull with my teeth to release me. this https://apwcompany.com/em200-12-212/ is the one i bought, but if in a spread eagle position, can pull it apart. i'd like to try the 400lb magnet at some point. i dont think i could separate that.

[Kinbaku]

Welcome to our group, Konsba.
You can also use the parachute system with an electromagnet as final lock.

The last loop is an iron chain that is held by the electromagnet (instead of the clothes pin).

[Konsba]

Thank you!

this https://apwcompany.com/em200-12-212/ is the one i bought, but if in a spread eagle position, can pull it apart. i'd like to try the 400lb magnet at some point. i dont think i could separate that.

That's interesting, your magnet has the same dimensions, voltage and current specs as mine, but is rated for 140 lbs (vs. 88 lbs). I considered using larger magnets, but I'm pretty much maxed out in terms of operating current and temperature. Any more current and I will run into problems (I already trip OC protection in my smaller powerbanks at around 2.5 amps), and the magnet already gets uncomfortably hot (though I'm sure my 3D-printed enclosure doesn't help with heatsinking at all).

You can also use the parachute system with an electromagnet as final lock.

That's a good idea to have in one's toolbox, though there's still the problem with magbound-like device that there is a largish flat metal surface stuck to the magnet (the disc) that would have to slide through the loop when releasing. That's what I use the large ring for. (Hmm, I could have a larger ring after that, and even larger ring after that, and basically have a release sequence like in your linked post, though I doubt it would be much practical.)

The last loop is an iron chain that is held by the electromagnet (instead of the clothes pin).

Oh I see. I imagine a chain would not stick too firmly to the magnet. Is it sufficient?

[Shannon SteelSlave]

Send me a private message, Konsba, if you are interested in a promotion to a club we have here that might interest you

[TNTBound]

this is the battery bank i am using. https://www.amazon.com/gp/product/B01M7 ... UTF8&psc=1 i use the 12v bullet plug and it works great. i used a pvc end cap to mount the magnet into so it doesnt burn anything as it does get warm, insulates it nicely. i also added a picture of my magnet is setup. EDIT: that power bank will keep that magnet setup held tight for a bit over 5 hours when fully charged.

[Konsba]

this is the battery bank i am using

I'm using a classic 20,000 mAh powerbank with with two USB-A and one USB-C ports (I think it's a Xiaomi). That one handles the current well and can run the setup for 8 hours, which is plenty.

I have my own timer box that uses the 5V port and contains a boost converter for 12V. I guess I could get more power from the bank if I used QC or USB-PD (the bank should be capable of 50 watts), but so far that has not been worth the hassle.

i used a pvc end cap to mount the magnet into so it doesnt burn anything as it does get warm, insulates it nicely

The insulation is the issue here - the heat gets trapped inside and so the temperature rises. If I could make the enclosure from metal, it would help dissipate the heat and lower the operating temperature significantly, like a heatsink.

[Konsba]

I have taken some photos to illustrate the idea. To the left is a hard-point, to the right is whatever you want to tie to it. The second and third photos illustrate the release.

So far I have been very happy with this system. The depicted setup usually resides under the bed (the hard-point being its leg) and ties a rope that goes to the headboard and is used creatively there. Or the setup is out of reach high on a wall and ties one hand of a vertical spread-eagle, or is used to hold keys which I have to pull in once released. I have also used it under a chair to hold down my hands tied behind my back.

[Kinbaku]

If you ever want to make it stronger you can use that system of yours for the top ring of https://en.m.wikipedia.org/wiki/3-ring_release_system.

So without that yellow wire, but only the blue strap all the way from the top to which the narrow disc is attached that is released from the magnet.

[Konsba]

That would be crossing into dubious practicality and reliability territory (and the metal disc itself is 5 cm across already). I like the original system because it is dead simple and reliable, and after all, reliability is paramount in selfbondage. But it's good to know there are options to explore if ever more strength is needed.