finally good winding

[satdaveuk]

Nice job

You have done a nice job of that simon, after seeing your job, im wondering whether to take a mould from my minelab DD coil using casting sand, because by using that I could use it over and over again for different projects, and also apart from that less messy and alot cheaper.
Far as shielding ive always used 10mm lead tape which I used to use on shop windows for security purposes, Its thin lead with sticky backing, its plyable so no chance of cracking, also you can oviously solder to it, plus when wraped around it makes the coil very sturdy, by using this stuff in the past ive only ever loomed the coil with string nice and tight, like they did in the old days before cable ties, fit heat shrink sleaving to each coil lead, otherwise they can become brittle and break off, emerse in varnish for 8 hrs, take out allow excess varnish to drip off, allow 48hrs to fully harden, then apply self amalgamating tape which stretches and sticks to its self tight like a elastic overlaping as you go, then the led tape ,wrapping round over lapping 3-4mm, leaving the normall 5-10mm gap. After that the coils are ready for the housing.
Far as installing into the housing im going to fix with a small amount of resin, then fill with exspanding foam just to fill the mould, that way it should be a lot lighter.
I havent made the circuit board yet, got most of the components off the shelf, and the rest are on order.
When i get started i will do the same as you showing my project in stages, but in the meantime any tips will be greatfully received.
Ive been following the golden sabre thread since I joined here with great interest.
Many thanks again
Dave

[simonbaker]

You have done a nice job of that simon, after seeing your job, im wondering whether to take a mould from my minelab DD coil using casting sand, because by using that I could use it over and over again for different projects, and also apart from that less messy and alot cheaper.
Far as shielding ive always used 10mm lead tape which I used to use on shop windows for security purposes, Its thin lead with sticky backing, its plyable so no chance of cracking, also you can oviously solder to it, plus when wraped around it makes the coil very sturdy, by using this stuff in the past ive only ever loomed the coil with string nice and tight, like they did in the old days before cable ties, fit heat shrink sleaving to each coil lead, otherwise they can become brittle and break off, emerse in varnish for 8 hrs, take out allow excess varnish to drip off, allow 48hrs to fully harden, then apply self amalgamating tape which stretches and sticks to its self tight like a elastic overlaping as you go, then the led tape ,wrapping round over lapping 3-4mm, leaving the normall 5-10mm gap. After that the coils are ready for the housing.
Far as installing into the housing im going to fix with a small amount of resin, then fill with exspanding foam just to fill the mould, that way it should be a lot lighter.
I havent made the circuit board yet, got most of the components off the shelf, and the rest are on order.
When i get started i will do the same as you showing my project in stages, but in the meantime any tips will be greatfully received.
Ive been following the golden sabre thread since I joined here with great interest.
Many thanks again
Dave

It's worth trying different ways to manufacture these parts. dfbowers technique seems to be the best if you can make the vacuum-former and get the right materials and use your oven. I think casting is an alternative, although I struggled with it. The latex mold was too much trouble -- if you can make a reusable, easy-to-make mold another way, that would be great, let us know how it works.

But bear in mind my mold was poured solid with the coils embedded (very heavy), so no space for foam -- but if you can mold a "shell" someway, that would be interesting.

Lead tape actually sounds quite good, other than lead is toxic (but so is much solder). It probably has lower conductivity than Al foil, which may be an advantage.

Still, all this wrapping of coil shields seems like too much trouble. It would be nice to have a conductive foam that works as a shield as well.

Every technique is worth knowing about - everyone has access to different materials and prices. Keep us informed of what you do.

Cheers,

-SB

[satdaveuk]

Price of Shell

Hi Don
Unless i got it wrong do you sell the shells?
If so how much £... where are you based? I live in the south west of England

Regards

Dave

[satdaveuk]

It's worth trying different ways to manufacture these parts. dfbowers technique seems to be the best if you can make the vacuum-former and get the right materials and use your oven. I think casting is an alternative, although I struggled with it. The latex mold was too much trouble -- if you can make a reusable, easy-to-make mold another way, that would be great, let us know how it works.

But bear in mind my mold was poured solid with the coils embedded (very heavy), so no space for foam -- but if you can mold a "shell" someway, that would be interesting.

Lead tape actually sounds quite good, other than lead is toxic (but so is much solder). It probably has lower conductivity than Al foil, which may be an advantage.

Still, all this wrapping of coil shields seems like too much trouble. It would be nice to have a conductive foam that works as a shield as well.

Every technique is worth knowing about - everyone has access to different materials and prices. Keep us informed of what you do.

Cheers,

-SB

But as i said Simon I like many others on here was very impressed at your coil making, and as you stated we are all very much on a learning game with manufacturing coils, and im so sure that with the engineering brains behind all this with the likes of you and everyone else on here, we will between us crack it.
And I for one looking to the fucture if we get that good at it theres know reason why we cant make these coils to order for people and actually make some money for all are pains and time spent on this subject. You know as well as I do the biggest let down with a branded or unbranded metal detector on the market these days is the search coil, that is why people like SEF are making a killing on the market.
In my opinion Minelab for one never supplied a decent search head since they pulled away from Coltec, which as you know or may not know used to manufacture and supplie for all Minelab detectors.
Anyway i hope this thread keeps going because I for one have learned so much from here.
Many thanks and warm regards
Dave

[satdaveuk]

Casting

Hi Simon
I forgot to mention casting is actually quite easy, the art of it is just make sure your resin mix is thin, its just the same as alloy casting, when I was a kid still at school I used to practise at home using moulton lead from old gas pipes etc, boil up in a old saucepan, skim the crap off the top and poor into the hole its simple as that, just make sure you make a vent hole at the upper box across from the hole you poor the mix otherwise you get air gaps, which is a favorite mistake people make.
just knock up a couple of box shaped jigs, size to suite your mold and a extra say 2" all round, fill the bottom box full of damp casting sand compact as if your going to make a sand castle, I say casting sand because unlike ordenary sand its very very fine.
Build the coils up to make them quite alot larger using masking tape, or anything thats easy to take back off later, but be neat with it because this is what you mold is taken off.
Dust the coil assembly with chalk powder
If your with me at the moment you should have the bottom of your coils laid in the damp compact sand ready chalked pressed in just to make a impression.
Then sprinkle the fine chalk powder all over .
If you have not or cannot get a tin of chalk either go to your local pub that plays shove halfpenny because they use it in the game, or get a stick of chalk and grind it very very fine, im sure that will do the trick although never used it.
Now get your second box and do the same, damp sand just like it would be perfect to make sandcastles , compact it solid, cover then dust with the chalk, then marry the two boxs up, pushing firmly down.
So now if your still with me, you have one box ontop of the other, the coil is between the two boxes, chalk sides are facing each other in the middle.
Its about this time I would go and make a cup of tea, very English I am lol
Now what you need to do is get a bit of half inch dia pipe and insert it through the top of the upper box in the middle of the coils till you feel contact with the coil, that is the tricky bit just take your time.
Now do a smaller hole at the left or right hand side, that your breather hole.
After that split the two boxes apart, now you understand why we needed the chalk, because without it, the sand between the two boxes would have stuck together, and also taking the coil out the sand would stick to it
Now the next step will govern how good your cover of resin and your finsh will be.
First of all make sure the holes in the top box are clear, note top part of the coil impression.
Secondly lift coil out of the lower box , again you can see why we need the chalk.
You should now have the top part of the coils impression on the top box, and the bottom of the coils impression on the bottom box.
The next bit is important and tricky because if you had just wanted to make a normal mould all you would have had to do is put the two boxes back together without your coils and poured either your moulten metal or resin into the hole until it overflow out of the hole, and let it set, after that split the boxes and bingo, perfect casting of your coils, you would then have cut off the feeder stick that would have been left.
In you case we need to mould around the coils and as I stated in theory it should work, but ive not yet tryed it.
You can see now why i said build your coil up bigger thicker.
Undo all the masking tape which will now make the impression bigger than your coils.
Lay your coils back into the sand placing small random spacers underneath , cock tail sticks should do.
Put second box back on making sure they are well anchored together then pure the glue, remember keep it thin, thinner the better finsher.
Wether you go down this road or not is oviously up to you but im certainly going for it once i built my coils, and I will let you know the result.
Anyway for all of you that didnt know, at least now you know how to make moulds.
All the best everyone
Dave

[Jerry]

Simon: Your coil winding set up and shielding technique mirrors what I did almost exactly. Very interesting to see all the pictures of your handy work. I have everything I need but still have not actually made a plastic shell yet. I have a vacume table and everything and just need to get back with this project. Have been hung up on this step for a long time. You are getting me interested again! Good work.

Jerry

[simonbaker]

Simon: Your coil winding set up and shielding technique mirrors what I did almost exactly. Very interesting to see all the pictures of your handy work. I have everything I need but still have not actually made a plastic shell yet. I have a vacume table and everything and just need to get back with this project. Have been hung up on this step for a long time. You are getting me interested again! Good work.

Jerry

I can't remember who started the "glue-pot" technique for coating the wire as it winds on, but dfbowers made good use of it, and I've adopted it, with varying success. My coil winder I like, but I'm still all thumbs at making shells and potting. My casting experiment was very awkward and made a big heavy coil head - satdaveuk seems to have ideas on how to do it better and easier.

The vacuum-formed shells seem to make very pretty, durable, and professional looking shells, hard to beat. I like the idea of a lighter foam to pot with instead of resin/epoxy if possible.

I'm still looking for a simple-as-sh*t way to pot a coil, like just sinking it into a workable clay-like substance that will harden and trimming it. Uglier than a mud fence but need something ultra low-tech.

But it looks like for now vacuum-forming rules, so I think you're on the right track, looking forward your results.

-SB

[simonbaker]

Hi Simon
I forgot to mention casting is actually quite easy, the art of it is just make sure your resin mix is thin, its just the same as alloy casting, when I was a kid still at school I used to practise at home using moulton lead from old gas pipes etc, boil up in a old saucepan, skim the crap off the top and poor into the hole its simple as that, just make sure you make a vent hole at the upper box across from the hole you poor the mix otherwise you get air gaps, which is a favorite mistake people make.
just knock up a couple of box shaped jigs, size to suite your mold and a extra say 2" all round, fill the bottom box full of damp casting sand compact as if your going to make a sand castle, I say casting sand because unlike ordenary sand its very very fine.
Build the coils up to make them quite alot larger using masking tape, or anything thats easy to take back off later, but be neat with it because this is what you mold is taken off.
Dust the coil assembly with chalk powder
If your with me at the moment you should have the bottom of your coils laid in the damp compact sand ready chalked pressed in just to make a impression.
Then sprinkle the fine chalk powder all over .
If you have not or cannot get a tin of chalk either go to your local pub that plays shove halfpenny because they use it in the game, or get a stick of chalk and grind it very very fine, im sure that will do the trick although never used it.
Now get your second box and do the same, damp sand just like it would be perfect to make sandcastles , compact it solid, cover then dust with the chalk, then marry the two boxs up, pushing firmly down.
So now if your still with me, you have one box ontop of the other, the coil is between the two boxes, chalk sides are facing each other in the middle.
Its about this time I would go and make a cup of tea, very English I am lol
Now what you need to do is get a bit of half inch dia pipe and insert it through the top of the upper box in the middle of the coils till you feel contact with the coil, that is the tricky bit just take your time.
Now do a smaller hole at the left or right hand side, that your breather hole.
After that split the two boxes apart, now you understand why we needed the chalk, because without it, the sand between the two boxes would have stuck together, and also taking the coil out the sand would stick to it
Now the next step will govern how good your cover of resin and your finsh will be.
First of all make sure the holes in the top box are clear, note top part of the coil impression.
Secondly lift coil out of the lower box , again you can see why we need the chalk.
You should now have the top part of the coils impression on the top box, and the bottom of the coils impression on the bottom box.
The next bit is important and tricky because if you had just wanted to make a normal mould all you would have had to do is put the two boxes back together without your coils and poured either your moulten metal or resin into the hole until it overflow out of the hole, and let it set, after that split the boxes and bingo, perfect casting of your coils, you would then have cut off the feeder stick that would have been left.
In you case we need to mould around the coils and as I stated in theory it should work, but ive not yet tryed it.
You can see now why i said build your coil up bigger thicker.
Undo all the masking tape which will now make the impression bigger than your coils.
Lay your coils back into the sand placing small random spacers underneath , cock tail sticks should do.
Put second box back on making sure they are well anchored together then pure the glue, remember keep it thin, thinner the better finsher.
Wether you go down this road or not is oviously up to you but im certainly going for it once i built my coils, and I will let you know the result.
Anyway for all of you that didnt know, at least now you know how to make moulds.
All the best everyone
Dave

That sounds pretty challenging to me! And don't forget, you have to maintain a precise "nulling" of your coils the whole time, can't slip even a millimeter.

Another consideration is that you don't want the coils to breach the surface of your molded shell, so I'm not sure how you keep that from happening. I tried to solve it by filling the mold 1/4 full, hardening, then placing the coils on the hardened cast, then pouring the rest of the goo into the mold to cover the coils. Still doesn't stop the sides of the coils from poking near the surface of the mold. Again, the plastic vacuum-formed shells provide more uniform protection.

If you make one with sand casting, take a video, should be interesting!

-SB