PimentoUK

Seeing as the 'Bi-Axial' shape of the stock 11"x7" coil was considered a 'good thing' , and was presumably what the machine was designed for, it always baffled me why the big coil was round in shape. Surely a 18" x 12" or whatever, resembling a scaled-up stock coil would be best ?
( I did wonder if the 5" coil may be internally a bi-axial, but NASA-Tom D stated it was as it appeared - circular inside and out. Perhaps it doesn't matter so much on such a small coil ? )

The brand is actually Quest, they were formerly known as Deteknix, but changed their name a few years ago. But the old name still gets mentioned, particularly in relation to their pinpointers, which were big sellers.

Their website, questmetaldetectors.com will give you a starting point for your research.

I preferred the older style, personally. The new larger font size seems to give distorted characters, with poor aesthetics, like they've been resized badly. Attached screengrab shows the effect. "SDC2300" only has the D correct, all the others have that odd pixel at the top. If I shrink the display size down (ctrl -  on Firefox) it looks more like it used to. And when viewing the 'front page' , the thread titles don't show fully. For example
Ice Age Fossils In Nevada
just displays as:
Ice Age Fossils In ...
shrinking it down restores normality.

Makes me think it's optimised for wide-screen monitors.

( my PC is coal-powered, though, so don't take too much notice of me, I'll just carry on as normal... )

 

Bill:
That 0.2mm was a starting point, it's what I made my ones from. You could try thicker ones, like 0.3mm if you're having trouble sourcing suitable scrap, and of course you can use multiple sheets, so if 0.15mm is to hand, try 0.15mm or 0.3mm ( 2 x 0.15mm ).

It's hard to say how much packing is needed, especially considering there may be product variations - early models may have different rubbers to more recent production ones etc.

As for the source of plastic: products that are packed in cardboard boxes with clear plastic windows so you can see the toy etc inside could be OK. Screen protectors for phones/tablets may be in the right thickness range.

Bill : I've added a photo to my original post.

"Do you feel that the Detect-Ed Coil Savers would do the same thing?"

The coil-savers seem to offer little adjustability, that's likely their weak point. And it only takes a fraction of a millimetre to make the difference. Ed's choice of rubber compounds is good, but fine-tuning of the mechanical aspect is also needed, I think. [ if he has a punch tool made up, it may also be useable for teardrop shim manufacture ]

I'm thinking that if a softer rubber was used, it would give greater friction, but it would also compress more, possibly resulting in the plastic-plastic contact. Perhaps have a half-thickness washer, backed by a non-compressible spacer?
The stock rubbers supplied by ML seem adequate, and resourceful folks can source plastic sheet from a wide variety of places around the home, which is why I thought that was the simplest solution.

"So that means the Detect-ED things likely work, as they're there fixing the exact problem you describe"
It certainly looks like that's one part of their solution. I've not seen them in the flesh, of course, so they may be softer ( or harder ) rubber blends, with different friction levels. If less force from the bolt is needed, to achieve the same resistance to clevis movement, that could be useful.

"Coil ears don’t break... people break coil ears. Seems like nearly all the breakage reports are from surf users."

Few people detect surf here in the UK. It's mostly inland, though crop stubble and grass can create a coil side-load. Most people report the ear(s) broke when not in use, the EQX was taken from storage/ a carrying bag etc and it was found broken when the machine was assembled. That was how mine failed. Simply putting the ears under strain continuously for months is enough to cause failure.

As an engineer, I've given this some thought and closely examined my coil. And saw the cracks, saw them get bigger, then one ear broke. Mine broke at the bottom, seemingly the most common failure mode.

I think the problem is this:
The teardrop rubber washers should protrude above the clevis recess they sit in, this includes when the bolt is tightened. This is the problem. The washers get squashed until the coil ears touch the clevis, plastic on plastic. This does two things: it allows the coil ears to bend inwards more than they were designed for, and it allows wear of the plastic when the coil angle is adjusted, such as when it's packed away flat. Abrasive dirt can also get into this exposed area, worsening the wear. This plastic wear then allows the coil bolt to be tightened further, bending the ears in even more. Repeat this, and the ears get grooves worn in them, the clevis gets narrower. I recommend you take a look at your own coil ears inner faces. If there's a circular wear groove, you're heading for problems.

The 'solution' I have tried is to insert thin plastic shims behind the rubber washers, to space them out 'fatter' , so the coil ears tighten on the washer, not the clevis body, and they don't get bent inwards so much. Shim plastic is readily salvagable from packaging, household items. Thicknesses around 0.2 mm ( 8 thou ) seem a good starting point, use the same thickness under both washers. Scissors and a sharp craft knife will be enough to cut them out. Use the rubber washers as a template.

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The second failure I've seen is cracks running from the ear hole out to the edge, often in multiple places. This is caused by improper moulding. The 8mm hole is moulded into the ear, so the liquid plastic has to flow around some 'pin' in the mould, and then join up solidly on the other side. This creates a weak point, when cooling plastic doesn't fully merge.
ML should consider moulding the ears without holes, then drill the hole afterwards as a seperate process. Ideally the hole should be reamed, to give a clean bore that will be resistant to crack formation.

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The solution to ears cracking at the bottom is probably to have taller ears, so the flexing caused by bolt-tightening doesn't cause stress concentration in one small zone. Larger ears would let more/all of the rubber teardrop washer be compressed, instead of just the 'round' part. The tip of the teardrop is further away from the pivot point ( the bolt hole) so it's friction contribution would help resist 'coil-flop' better than the current arrangement.

The idea of a more discrete hand-digger is a good one. I have thought about it myself, I have a salvaged steel bicycle frame that's a mix of hi-tensile and 4130 cro-moly tubes, and a digger was one possible use for the metal. But I think the tool still needs to be fairly strong and sturdy, and that's possibly the weak point of your tool. It's nicely made, but you're restricted by the tool that it's created from. The handle, and the region where it joins the blade, look vulnerable areas.

If your blade was attached to a brass handle in a more substantial way ( silver solder ? ), you would have a neat and unique tool.
For my design, I was thinking along the lines of a hori-hori trowel, but smaller:
horihori_trowel

The largest target market is the 'high-conductor coin-shooting' user, and the 5-8 kHz range suits that.

Beginners don't want fidgety, sparky machines that false-signal on iron too much.

From a technical view, lower freqs pick up less ground signal, so depth is easier to obtain without the troubles of adjustable ground-balance. It's likely to be cheaper to make a lower-freq machine; coils need less precise adjustment, lower-speed analogue parts like amplifiers are slightly cheaper etc.

It is a US-led phenomena, though. I notice UK manufacturer C-Scope have used 13kHz as a good all-round choice on a large number of their machines, including beginners ones.

I think it's more obscure than that, probably intentionally so.
If you look at that French website, and compare the Coinmaster1 TRDX, Coinmaster 2 TRDX and Coinmaster 3 TRDX, they have date codes of GL , K4 , R4 respectively.
They all appear to be similar in vintage, though - the same big box, big coil connector. I suspect they update the date code on a monthly or weekly basis, and probably miss out a few letters to obfuscate things.

Here's a Pinterest page showing a Coinmaster 1 TRDX listed on Etsy, it has a date code of L4:
pinterest CM-1TRDX

I do find it amusing that you got rid of the half-cent in the 1860's, yet the next coin to go is still in use 160 years later. US inflation has to be 50-times since then ?
We have managed to lose our lowest-denomination coin a few times, 1956 (farthing) , 1971 ( halfpenny ) 1984 ( decimal halfpenny), but nothing since. We have had higher inflation than you, of course, about 100-times since the late 1800's. [ and trivia : inflation is 5000-times since the Pound Sterling came into use in about 760 AD.]

Yes, throwing them away is another option. In the early 1980's we had a small halfpence coin that was worthless, and they were discarded, children would throw them at each other as weapons, if anyone dropped one, they certainly wouldn't bother picking it up. And rather annoyingly, they target ID identically to a more modern One Pound coin ( about 1.20 US dollars ), which makes cherry-picking these 'valuable' coins more troublesome, in addition to the various aluminium bottletops that ID in that range too.

We're overdue getting rid of our near-worthless 1 pence and 2 pence coins ( = 1 & 2 US cents ), our next denomination, the 5 pence, is cheap to make ( steel cored, nickel-plated outer skin), so it can continue in use for the future. You US guys need to ditch the 1 cent and the 5 cent simultaneously. If just the 1c goes, that puts extra demand on the 5c, which is over-expensive to make, so causes more problems. As your 10c is cheap to make, it's OK to have it as the lowest denomination coin.

This has a familiar ring to it. Our neighbours in the Republic of Ireland have had this issue twice in recent history, each time requesting the public 'look in their drawers and stop hoarding money'.

Shortly before they transitioned from the Irish Pound to the Euro in 2002, they stopped making the Pound coinage - resulting in a circulation shortage.

Then 15 years later they found they were short of near-worthless 1 & 2 Euro-cent coins, as people didn't bother using them more than once before putting them in jars, etc.

links:
IrishTimes 2000

IrishIndependant 2014

No beauty, but I hope it hold up for a long time, a new coil is not a cheap item.

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I always wondered what the bolt supplied with Fisher/Tek machines is made of. It's a commercial bolt made from some engineering plastic, possibly like PEEK, that's been over-moulded by FT with some softer plastic like nylon to create the big knurled head. The nut is what it appears to be, no 'embedded' high-strength nut. PEEK fasteners seem to be seriously expensive in small quantities, maybe they become more cost-effective when 1000's are purchased? The bolt could be glass-filled plastic, that would certainly be cheaper.

They seem pretty sturdy, considering they aren't that large in diameter.

Their catalogues are a guide to when a machine was introduced, though they no doubt would be manufactured for a number of years before being discontinued.

Here's a French website, with pics of your machine, catalogues:
whites detectors

whites catalogues

and Sven's site has many old catalogues too:
treasurelinx site

It would be interesting to see if anyone does know the 'secret'.

I have a Coinmaster 2 hipmount version, date code is HD. The few electronics part with any obvious date codes are an IC dated late 1978, and the loudspeaker appearing to be 1980. This is a Savo Scotland produced machine, so may not necessarily match a US-made one.

I would suggest looking for date codes on the inner workings. IC's ( if it has any ? ), the loudspeaker, electrolytic capacitors, the potentiometers.

In a nutshell ... it sounds like you've understood it.

As I've never used BBS/FBS machines, I never took the time to understand the details, so I can't explain FE/CO properly, but that Knowledge Base pdf seems to cover it, though I'll add another ML article to that post, just fer info.

It has been discussed on Geotech1 and Dankowski's forum. I'll try and pull together a few links that are relevant. There's also a technical paper on ML's website explaining some of FBS operation.

The summary is:
FBS transmits its two frequencies CONSECUTIVELY. It produces 8 cycles of 25 kHz, followed by 1 cycle of 3.125 kHz, then repeat. The key point is that during the 3.125 kHz transmission, there is no other signal present, so there is just a square-edged waveform with a 160 microsecs gap between two consecutive transitions. This is used as a crude PI signal, which allows the detector to analyse a target differently to how a continuous sine-wave machine would see things. By combining the analysis of 'crude PI' and the 'continuous waveform' (that goes back to BBS machines like the Sov) it's possible to create a 'FE' figure, in addition to the more conventional 'CO / conductivity' one.

Multi-IQ does transmit all three of its signals SIMULTANEOUSLY , in a complex square-edged waveform that clearly has a lot of 39 kHz, in addition to the 7.8kHz & 18.2 kHz signals. So there is never a point where there's a big long gap between waveform transitions - about 20 microsecs is as big as it gets. So this 'crude PI' method can't be applied.

So to produce FE/CO figures, the Equinox would have to generate something close to a BBS/FBS signal. Long gaps between signal transitions are needed at some point.

Possible solutions would include a user choice of Multi-IQ or FBS operating modes. Or perhaps a mashed-together mode, such as one cycle of 5kHz followed by a burst of Multi-IQ waveform for 200 microsecs then repeat. The first of these is simpler, as nothing 'new' needs to be engineered, the existing know-how just needs transferring to the Eqx platform.

Here's the Minelab Technical article that mentions the 'FE' - determining technique:
ML article

There are a couple of other simple 'how detectors work' articles on ML's site that are perhaps too basic, but might be interesting to some:
www.minelab.com/usa/support/knowledge-base/articles

Here's a couple of Eqx threads on Geotech1 which show the waveform:
Geotech EQX Freq

Geotech EQX general

This FBS thread on Dankowski's Forum unfortunately does contain a lot of poor info as well as good info, and the waveform screengrabs that Yeasty posted up have now 'gone' , so it's not so good now.
Dankowski FBS geekery

Quote:"Unless there is something inherently limiting regarding Multi IQ's ability to support Fe-Co target ID ..."
There is. The simultaneous multi-freq technique used in the current Equinox models has no means of determining the 'FE' characteristic of a target.
But ... as the Equinox would appear to be able to generate any frequency waveform ( it's created by software ) it could be made to run a BBS/FBS-style signal, and hence have CTX-like performance. The limiting characteristics of the coil may affect what is possible. The Eqx seems capable of working at 5kHz and 40 kHz , FBS works at 3.125 kHz & 25 kHz, so maybe a tweaked FBS operating at slightly higher freqs would be viable. There's nothing magical about the FBS frequencies, the 1:8 ratio isn't 'golden' , it was chosen because it was easier to create in the early Sovereign-era electronics.

@ Cobill: I think you've made an error in purchasing those '8000 mAh' cells. The highest capacity I've found available from a known/reliable/trusted brand is 5500 mAh. Those cells in your link are very likely to disappoint, and may well have a capacity some way below 2000 mAh.

I was aways puzzled as to why the Fisher 15" coil was round in shape. Everyone seemed to think the 11 x 7 bi-axial stock coil was a good shape, and presumably the machine would in some way be 'optimised' for that shape. So why wasn't the 15" coil actually a 18" x 13" or suchlike?
If you're hoard-hunting, then I guess shape doesn't matter that much, so the round coil would be acceptable. But heavy ... if you're only planning on light-duty use, there is no doubt some weight-saving possible.

I have tried large-target hunting with my F75 / stock coil. It works, but really needs a bigger coil in the 15 - 20 inch area to do the job properly. I never bought the Fisher 15 coil, and since buying the Eqx, I've found its stock coil is large enough to give reasonable 'hoard-hunting' potential. So hopefully in the next month I will be trying it out on some farm fields that are ready for crop harvesting.

The problem with the T2 is going to be down to the 'sensitivity hole' , the worst case being when Disc is set around 25-30. The F75 in DE (default) mode has the same issue, when Disc is set to around 11. A quite significant loss of sensitivity occurs, not that the User Manual makes any mention of it. On the F75, increasing Disc from 1 through to 11 causes a progressive loss of sensitivity. Increasing it from 11 through to 23-ish steadily increases sensitivity back to 'full' level. I guess on the T2 this is roughly 1 thru 25 thru 50 ( I've never used a T2)

The F75 thankfully has JE ( Jewelry ) mode, which does things differently, and seems to not suffer the 'hole', being sparky regardless of disc settings. I haven't really tried large iron hunting on my F75, so I can't guarantee JE is the best mode, though.

Shelton is a man of few words ....

He's demonstrating various 3D printed modifications to his Equinox with telescopic carbon shaft.
Audio is in Polish.

Quote:" Are you using a BMS module inside the 4s1p tube? I don't know if I'm correct but seems to be the easier combination for a self balanced recharge .."

Lithium-Ion cells don't self-balance, and have to be forced to charge correctly. This means either:

A seperate charging connector bringing out all the cell terminals, (which will be 5 connections in the case of this '4s' pack) and charge with an appropriate balancing charger ( eg. R/C model charger )
or:
A charge balancing circuit integral to the battery, allowing simple charging ( eg. current-limiting), on just the end terminals.

In the case of using a seperate charging connector, the pack can be charged quicker, as all the thermal issues are moved to the charger, which can have high-power transistors/heatsinks etc as needed. A balanced charging circuit has less ability to juggle the currents through each cell, so generally they seem to be used in conjunction with slow ( trickle ) chargers.

A seperate charging cable still means a battery protection circuit is needed, however, to guard against over-discharge, accidental overload/short-circuit, and possibly overheating. That is what the module pictured in OBN's post appears to show.
It's also wise to fit 'gross overload' protection on a high-powered pack like this. That would include a conventional one-time wire fuse, a thermal fuse, and possibly a self-resetting 'poly-fuse'.

I currently have a dismantled 5s lithium pack from a handheld Vax cordless vacuum cleaner. That has charge-balancing internals, and there's a surprising amount of stuff on the large circuit-board inside the pack, it's the full size of five 18650 cells.
I also have an EBL 9 volt PP3 apart, which obviously is much lower power, and only two cells. There's not much to the balancing electronics in that. I don't know what techniques either of these packs use to achieve balancing, they are probably quite clever.