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Author Topic: Pulse Induction detector build  (Read 28628 times)
nobby
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Wanna be boy band....


« Reply #30 on: October 01, 2015, 03:50:13 PM »

just a thought for a shaft......Val Beechey has some bamboo for sale Cheesy Cheesy Cheesy
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« Reply #31 on: October 01, 2015, 05:57:38 PM »

Fantastic job with the casting

Thanks Wink

The foundry is quite a recent addition to my armoury - did my first casting in 2011. Back in the 1990s I became aware of a series of books by an American author, Dave Gingery, called 'Build your Own Metal Working Shop from Scrap.' I finally bought them in about 09 and devoured every word. His premise was that by making your own castings from scrap aluminium and fitting steel sliding surfaces you can build a set of machine tools. So the first book shows how to build a charcoal-fired crucible furnace and make castings, in the second book you use the furnace make the castings to build a lathe. In the third book you use the furnace and the lathe to make a shaper; in the fourth book you use the furnace, the lathe and the shaper to build a milling machine etc. Book 5 is a drill press, book 6 is a dividing head and other accessories and the 7th book (illogically) shows how to build a sheet metal folder.

Built the furnace but was unhappy with the time it takes to melt aluminium with charcoal so made a propane burner. Much better. Already had a lathe - not worth building one so decided to build the shaper as a first project. Made most of the patterns and was waiting to start casting them when I was offered a commercially made shaper for a pittance. No brainer - I bought the shaper and rebuilt it from the ground up. Started making the patterns for the milling machine instead but bought a small (2" x 10") lathe off eBay from a seller in Brum. When I went to collect it the guy said, 'Oh, yes - this goes with it too  . . . ' When I got home I discovered that 'this' was a beautifully made Gingery milling machine. Couldn't make it up Roll Eyes I've already got an Elliott drill press so don't need to build one, so there's only the dividing head left to do.

I can understand your method of making your shafts - as I've said mine is probably over-engineered but it works for me. Good job I'm not trying to make money out of it - it would cost a fortune! I did try the plastic lower shaft in the aluminium upper shaft - I had a coil fitted to it to give it some weight and it seems stiff enough as it is - when I built the Barracuda I planed a long, thin piece of wood down to make an internal 'spine' in the plastic pipe which stiffened it up. The upper shaft was the problem as it 'hogged' in the middle where the handle was hence the reason for the MK2 aluminium setup.

Think I'll christen this machine 'The Vincent,' - Vincent motorcycles were once described as 'a set of solutions to non-existent problems . . . ' just need someone to make the vinyl stickers for me  Wink

just a thought for a shaft......Val Beechey has some bamboo for sale Cheesy Cheesy Cheesy

Don't think I wasn't tempted . . .  Wink
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Cymro
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« Reply #32 on: October 10, 2015, 07:49:28 PM »

Been busy in the workshop again - working on the main PCB box now.

There are only two components inside this box - the PCB and the battery. The last thing I want is for a heavy sealed lead-acid battery to break loose and destroy the PCB, so I needed to make a good solid mounting for the battery.

Couple of problems there. The battery needs to be at the forward end of the box, which is also where the wires from the PCB to the handle-mounted control pod need to exit the box. I also didn't want the battery terminals to be able to short-circuit on the aluminium box. I wanted the terminals at the top in the operating position - although it's a sealed lead-acid battery there is the minute chance that it might leak acid from the casing onto the PCB if it was upside down - and the most likely place for that to happen would be where the top of the battery is fixed to the bottom.

I had the additional problem that the bottom part of the PCB box has a lip about 1/2" deep which fits inside the upper part, so the battery compartment couldn't be allowed to sit flush against the end panel - it needed a stand-off.

I used some thin (1mm) aluminium sheet I had in my stock of 'useful one day' metal so I drew up a layout for a folded box, marked it out on the aluminium and cut it out (Pic 1.) Folded the lip for the front and the back in Pic2  then folded the sides up into the box shape in Pic 3 and brazed the mitres in the corners then cut a hole in what will be the top for the terminals to protrude through.

I still had the problem of the lip in the bottom part of the box, so I had a root around and found a bit of 4mm flat aluminium plate, which I bandsawed a suitable chunk from and drilled and countersunk a couple of decent sized holes in it (Pic 4.) I clamped it to the battery holder and brazed it on - Pics 5 and 6.

When it was cool enough to handle I drilled and tapped four M4 holes to attach it to the box - pic7. It's bolted to the box in Pic 8, and Pic 9 is the same view with the picture rotated so it looks as it will in use.

Its position means that I have enough space to run the wires under the battery through a hole (yet to be drilled) and up the handle. The battery will be held in position by the bottom part of the box, but I may yet attach a Velcro'ed webbing strap under the base of the battery to hold it in place if I remove the bottom of the box.

I've attached the PCB/battery box to the shaft with M6 button-head socket screws now that the battery is firmly attached - I wanted to find the best point of balance with a coil and the arm cup fitted.

Going to have to decide how I'm going to mount the PCB in the box soon - oddly, there aren't any holes in the PCB and it's double sided so I can't drill any. It needs to be mounted in the same orientation as the battery - component side up in the operating position - to help with routing the wires. I could use PCB stand-off clips but I don't want any holes in the top of the box to let water in. Got an idea about how I'm going to do that - I'll explain in due course.









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Resurgam
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« Reply #33 on: October 10, 2015, 08:26:18 PM »

What do you reckon the whole thing will weigh, when finished and assembled? 
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Cymro
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« Reply #34 on: October 10, 2015, 08:42:44 PM »

Don't know offhand - I'll try and weigh what's already there tomorrow - all that's missing now is the control pod. The balance is good though - I think that's important.

The coil I put on is off the Barracuda - haven't tried the proper coil on it yet (read: haven't wound the proper coil yet . . .  Wink)
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« Reply #35 on: October 11, 2015, 06:45:05 AM »

                       Having been with you from the commencement of this project; it's interesting to see how serendipity is greatly on your side!  Grin
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« Reply #36 on: October 11, 2015, 11:35:22 AM »

Well Chris, I'm trying to eliminate luck from the equation by breaking it down into steps and planning each step as I go, anticipating potential problems. Sometimes you can't so then you have to work with what already exists.

As I've said this is a learning experience - not the materials, skills or techniques but what will work best in terms of a functional unit - and one reason why I chose to base it on an existing successful design.

Just weighed it and it crashed the digital kitchen scales . . . Seriously - the scales have a limit of 2Kg and they showed 'OVERLOAD . . . ' So I took the battery out and weighed it separately - the battery is 560g and the rest of the detector weighs 1.625Kg, making 2.185Kg or 4.75 lbs. Shouldn't be much heavier when it's finished.

Just hope the PCB is in working order when it's all done . . .  Roll Eyes
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Resurgam
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« Reply #37 on: October 11, 2015, 12:06:07 PM »

                                    Once you have it all together and up and running; if you find you have need of a bungee harness, I have a spare one going free. Just pm me and it's all yours. Smiley
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« Reply #38 on: October 11, 2015, 12:10:01 PM »

That's kind - thanks!  Grin

If you're in the area and would like to have a look at what's going on, you're always welcome!
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« Reply #39 on: October 11, 2015, 02:01:05 PM »

                                   Sounds interesting m8; I should be down that way in the next week or so. Having run some of my finds by the Crown Estates and the FLO and both having relinquished any interest; it just remains to run them past local Plod and the Receiver of Wreck. Not to mention the RAF Historic Section.

                                   Things are starting to get interesting at Talacre; if not a little strange! I chose beach detecting as the easy option but hadn't counted on having to contact the Plod, Receiver of Wreck, Crown Estates, RAF Historic Section, and the FLO. It would be interesting to see you run the new detector over the sands at Talacre and see what you can winkle out. Hopefully nothing for the UXO squad!  Shocked

                                   Do you have any idea of a construction completion date for the new machine?
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« Reply #40 on: October 11, 2015, 02:44:10 PM »

Good luck finding any Plod around these parts - it's bandit territory! We're pretty much reduced to PCSOs these days since they sold the Police Station - they maintain an office at the Town Hall but when I wanted to report something the dopey girl on reception said I'd have to make an appointment to see them  Roll Eyes

Seem to have plenty of time for their Arrive Alive vans though . . .

The detector is getting done in fits and starts between actual detecting sessions and whatever else is demanding my attention at any given time. I tend to mull things over for a bit to allow my brain to evaluate the next problem and find a solution to it so it's difficult to make any promises on a completion date.

Is 'sometime sooner or later' helpful . . . ?

I'll email you my contact details.
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« Reply #41 on: October 11, 2015, 04:45:51 PM »

If you don't mind me asking why haven't you gone the lithium battery route to save weight?
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dingdong
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MAD COWS EAT METAL DETECTORISTS !!!🐂🐂🐂🐂🐂🐂


« Reply #42 on: October 11, 2015, 06:55:48 PM »

Well done for all the effort, and technology,know how,tenacity of purpose, dexterity, but for the likes a me......Naa !! I still think I'll be staying with CRAWFORDS !!!LOL!!!👏👏👏👏👏👏👏👏 👍
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« Reply #43 on: October 11, 2015, 07:00:36 PM »

Good luck finding any Plod around these parts - it's bandit territory! We're pretty much reduced to PCSOs these days since they sold the Police Station - they maintain an office at the Town Hall but when I wanted to report something the dopey girl on reception said I'd have to make an appointment to see them  Roll Eyes


                        I emailed North Wales Police and they said that the nearest police station for reportage of finds at Talacre is Rhyl.  Sad
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Cymro
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« Reply #44 on: October 11, 2015, 07:48:21 PM »

If you don't mind me asking why haven't you gone the lithium battery route to save weight?


Don't mind at all. Simple, quick and honest answer is that I hadn't considered it . . .  Smiley

After your suggestion I trawled eBay for a while and two things struck me: most of the lithium batteries on there seem to be dedicated - rechargeable drills etc, and the ones which aren't seem more expensive than SLA.

But I've got a SLA battery, have mounted it and find it's not so heavy after all, so I won't be tempted to change it.

Thanks for the suggestion though - maybe next time . . .  Wink

Well done for all the effort, and technology,know how,tenacity of purpose, dexterity, but for the likes a me......Naa !! I still think I'll be staying with CRAWFORDS !!!LOL!!!👏👏👏👏👏👏👏👏 👍

I enjoy making things - any things, so for me it's more the journey than the arrival IYSWIM. There is a lot of satisfaction in using something I've made myself as well, but I can appreciate your point of view.


                        I emailed North Wales Police and they said that the nearest police station for reportage of finds at Talacre is Rhyl.  Sad

Yabbut - I'm not in Rhyl . . . Out in the boondocks where I live (Holywell . . . ) they have to send bobbies from Colwyn Bay if there's any crime - but of course there is no crime here . . .  Roll Eyes
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