Magnets as a fastener/clasp/velcro alternative
Discussion
Can anyone advise me on which types of magnets might be appropriate for the following application please?
They would need to:
Be cost effective
Retain their magnestism
Be no bigger than 12ish mm dia.
Be more or less unnaffected by moisture/damp
The application would be to be stitched into a fabric flap so the magnet would hold the flap either open or closed. There would be a fabric thickness between the two magnets of max 1.5mm.
Rather than one expensive small magnet being integrated, 28 need to be incorporated so a cost effective type of magnet is required. The holding strength doesn't need to be high, but I would like a positive action of the flap being held into place, but it doesn't have to jump open and closed when the flap is moved.
Got any knowledge you'd like to share...?
They would need to:
Be cost effective
Retain their magnestism
Be no bigger than 12ish mm dia.
Be more or less unnaffected by moisture/damp
The application would be to be stitched into a fabric flap so the magnet would hold the flap either open or closed. There would be a fabric thickness between the two magnets of max 1.5mm.
Rather than one expensive small magnet being integrated, 28 need to be incorporated so a cost effective type of magnet is required. The holding strength doesn't need to be high, but I would like a positive action of the flap being held into place, but it doesn't have to jump open and closed when the flap is moved.
Got any knowledge you'd like to share...?
Search eBay for 'magnets': http://www.ebay.co.uk/itm/20-x-Strong-Round-Magnet...
Simpo Two said:
Search eBay for 'magnets': http://www.ebay.co.uk/itm/20-x-Strong-Round-Magnet...
Thanks for taking the time to link those - was wondering if anyone had a magnety background who might be able to recommend something through experience of a particular type and cost.Will check them out, ta.
You said the holding strength didn't need to be high and you wanted it to be cheap.
Ndfeb and ferritic magnets can break if constantly joined. Unless they are individually retained will join together.
If you can be more specific with the question we can be more specific with the answer...
Ndfeb and ferritic magnets can break if constantly joined. Unless they are individually retained will join together.
If you can be more specific with the question we can be more specific with the answer...
I can't go into explicit, exact details of the application (for good reason!) - but an almost identical application would be a large heavy duty waterproof backpack or holdall or large 'tactical' kit bag-type of thing.
From what I have read velcro degrades in UV light. So if the bag spends a lot of time outdoors then velcro may, over a number of years, degrade - and perhaps through necessity the bag has to be made in such a way that replacing the velcro could be difficult, yet the bag is designed to last a lifetime.
So the requirement is that maybe it has a number of external packs and flaps which need to remain open instead of flapping around as you search inside.
The magnets would be enclosed in a small pocket or maybe, if they had a hole in the centre, stitched into place and left exposed.
So if magnets replaced the velcro then would they rust when they get wet?
And very importantly - could they affect a smartphone or laptop?
How long would they last?
Another issue is that, for cosmetic reasons the flaps have already been made to accomodate 22mm dia. velcro coins - so strips would be difficult to integrate as the flaps are already in production, and the fastening points which the velcro was to be sewn to would become redundant and unfastened - meaning it's almost a complete certainty that circular magnets need to be used.
Therefore I require: long lasting, non rusting, circular magnets - yet a good balance between cost and power (I have to say that the cost of the linked ebay magnets from Simpo was surprisingly cheap, even at those retail prices).
Is that enough to determine something which should fit the bill? I need to know what the performance will be like after, say, five years.
From what I have read velcro degrades in UV light. So if the bag spends a lot of time outdoors then velcro may, over a number of years, degrade - and perhaps through necessity the bag has to be made in such a way that replacing the velcro could be difficult, yet the bag is designed to last a lifetime.
So the requirement is that maybe it has a number of external packs and flaps which need to remain open instead of flapping around as you search inside.
The magnets would be enclosed in a small pocket or maybe, if they had a hole in the centre, stitched into place and left exposed.
So if magnets replaced the velcro then would they rust when they get wet?
And very importantly - could they affect a smartphone or laptop?
How long would they last?
Another issue is that, for cosmetic reasons the flaps have already been made to accomodate 22mm dia. velcro coins - so strips would be difficult to integrate as the flaps are already in production, and the fastening points which the velcro was to be sewn to would become redundant and unfastened - meaning it's almost a complete certainty that circular magnets need to be used.
Therefore I require: long lasting, non rusting, circular magnets - yet a good balance between cost and power (I have to say that the cost of the linked ebay magnets from Simpo was surprisingly cheap, even at those retail prices).
Is that enough to determine something which should fit the bill? I need to know what the performance will be like after, say, five years.
A rare earth magnet shouldn't degrade, though they can if they are heated. The he problem you may find these is that they are too strong and can damage themselves when they make, they may fold up the lid.
Ferrite magnets are cheap, probably a more appropriate force, but can be prone to shatter.
I wouldn't expect a magnet to affect most products when they are turned off, but may not be great for an HDD if it is spinning, or your credit cards. Some products such as tablets will have magnet operated wake functions. But I wouldn't really see it as your problem. My tablet case has a magnetic clasp.
I would buy a few off ebay and trial, and buy a few cases that use magnetic clasps and take them apart to look at the size, type and distances used.
Ferrite magnets are cheap, probably a more appropriate force, but can be prone to shatter.
I wouldn't expect a magnet to affect most products when they are turned off, but may not be great for an HDD if it is spinning, or your credit cards. Some products such as tablets will have magnet operated wake functions. But I wouldn't really see it as your problem. My tablet case has a magnetic clasp.
I would buy a few off ebay and trial, and buy a few cases that use magnetic clasps and take them apart to look at the size, type and distances used.
CubanPete said:
..The he problem you may find these is that they are too strong and can damage themselves when they make, they may fold up the lid.
I'm really glad you've pointed that out about the rare earths - could be an issue that if they all try to come together it could distort the shape because there would be four in fairly close proximity.You're right, I have to get a small range of sizes for evaluation, see what I can get away with in terms of holding the flap but not gathering the fabric up because of the strength.
Thanks for your pointers.
)The example I'm giving above is as close as I can think of without stating exactly what and why - can't do that for good reason.
Yep, a zip *could* work as you say - but it might make use just a little more clumsy/complicated. I'm aiming for a 'open the flap and it stays open automagically' kind of usage.
But I appreciate your input (just received notification about an order for some zips I've recently placed, funnily enough!).
Yep, a zip *could* work as you say - but it might make use just a little more clumsy/complicated. I'm aiming for a 'open the flap and it stays open automagically' kind of usage.
But I appreciate your input (just received notification about an order for some zips I've recently placed, funnily enough!).
I'm assuming that you are aware of magnetic closures being used in the outdoor clothing industy. I've come across several high end skiing jackets that use them. Have a wander round Snow&Rock, make a note of the manufacturers and see if you can get in touch. Alternatively, find the chinese subcontractor that is undoubtedly manufactuing the jackets and see if they can supply.
Also I wouldnt be at all surprised if you could find exactly what you are looking for on Alibab.com
Also I wouldnt be at all surprised if you could find exactly what you are looking for on Alibab.com
XM5ER said:
I'm assuming that you are aware of magnetic closures being used in the outdoor clothing industy. I've come across several high end skiing jackets that use them.
Hadn't heard of their use in clothing - really interesting, thanks - I'm not a ski-ist so that tech was a bit of a blind spot for me. Will look into it.ReaderScars said:
The example I'm giving above is as close as I can think of without stating exactly what and why - can't do that for good reason.
Yep, a zip *could* work as you say - but it might make use just a little more clumsy/complicated. I'm aiming for a 'open the flap and it stays open automagically' kind of usage.
D'ye know, readerscars, I've never, ever seen a zip not "stay open automagically".Yep, a zip *could* work as you say - but it might make use just a little more clumsy/complicated. I'm aiming for a 'open the flap and it stays open automagically' kind of usage.
They just don't close by themselves! Strange, isn't it?
John
Simpo Two said:
Hang on, I thought only iron and nickel were magnetic. Presume neodymium is as well... any others? Do we know WHY they are magnetic?
And cobalt, and the other rare earth metals, also some alloys are ferromagnetic (or not) even when the alloying elements aren't (or are). E.g. stainless steel is largely iron and nickel but many types are not ferromagnetic.Gassing Station | Science! | Top of Page | What's New | My Stuff