detector stem

[bernte_one]

hello,

i´m still looking for the perfect selfmade detector stem.

If anyone has an idea post it here.

I uses most time an elbow crutch.

there are some newer models which you can fold

http://www.popab.com/opofoldable-en.html

[WM6]

Nice upper parts, but lower part have to be nonmetalic.

I am using mostly cheap bamboo for my testing devices.

For my "hiking" detector I am planning to adapt Portable Telescopic Carbon Fishing Rod for this purposses:


http://cgi.ebay.de/ws/eBayISAPI.dll?...=STRK:MEWAX:IT

[satdaveuk]

hello,

i´m still looking for the perfect selfmade detector stem.

If anyone has an idea post it here.

I uses most time an elbow crutch.

there are some newer models which you can fold

http://www.popab.com/opofoldable-en.html

Another good idea ive used in the past is using exstention telescopic assemblys used for paint rollers, you need to substitute lwr stem with water wast pipe or such like for ovious reasons, but they do a cheap light job and look the business.
Another one is using exstention telescopic rod thats used for car cleaning brushes.
And another option is, if you want to go real cheap and dont care to much on cosmetic, use one of those exstention rods that are used in the middle of wall to wall washing lines, there cheap and chearfull about £2-50 in uk.
All the best
Dave

[homefire]

These work quite well for the upper.

Simply replace the lower stem with PVC.

You can heat the end of the PVC and clamp it to get it to fit within the Coil Ears.

[bernte_one]

hello,

i has already replaced the lower parts of the elbow crutch with a 25mm cable channel pipe.
Over the cable channel you can place another one cutted in length and over them you place a shrink tube. So you can get a very stiff lightweight and good looking lower part.

But i´m wondering that the professional stems often have a lower metal part.
It can take effect on the magnetic field thats clear but it´s not moved in relation to coil - so it is equal or not?

[satdaveuk]

hello,

i has already replaced the lower parts of the elbow crutch with a 25mm cable channel pipe.
Over the cable channel you can place another one cutted in length and over them you place a shrink tube. So you can get a very stiff lightweight and good looking lower part.

But i´m wondering that the professional stems often have a lower metal part.
It can take effect on the magnetic field thats clear but it´s not moved in relation to coil - so it is equal or not?

Interesting one Bernte, I would say its equal but theres some say its proberly not.
All the early mainstream upmarket detectors i came accross had metal shafts, maybe its worth trying with and without, Now you have created another survey for us all to do.
All the best mate
Dave

[Qiaozhi]

But i´m wondering that the professional stems often have a lower metal part.
It can take effect on the magnetic field thats clear but it´s not moved in relation to coil - so it is equal or not?

If metal parts are used for the lower stem, or for the stem bolt, there are two main problems. Firstly, this unwanted metal affects the sensitivity of the coil, and secondly it distorts the electromagnetic field and upsets the coil balance.

As a simple experiment, you can take a detector (without a metal lower stem or metal stem bolt) and place a metal object close to the coil. Notice how the sensitivity is reduced when you perform a few depth tests with your favorite test targets.

[satdaveuk]

If metal parts are used for the lower stem, or for the stem bolt, there are two main problems. Firstly, this unwanted metal affects the sensitivity of the coil, and secondly it distorts the electromagnetic field and upsets the coil balance.

As a simple experiment, you can take a detector (without a metal lower stem or metal stem bolt) and place a metal object close to the coil. Notice how the sensitivity is reduced when you perform a few depth tests with your favorite test targets.

Interesting point Qiaozhi, I was thinking that maybe the reason why sensitivity is reduced is infact as you correctly stated the fact it knocks the coil inductance/ balance settings out.
So that tells me that proberly in the old days when balancing and designing the coils the stems must or should have been taken into account.
I got one of those zennox 1006 cheap detectors here with a metal shaft its as unstable with or without its shaft lol, so that doesnt prove much.

[Qiaozhi]

Interesting point Qiaozhi, I was thinking that maybe the reason why sensitivity is reduced is infact as you correctly stated the fact it knocks the coil inductance/ balance settings out.
So that tells me that proberly in the old days when balancing and designing the coils the stems must or should have been taken into account.
I got one of those zennox 1006 cheap detectors here with a metal shaft its as unstable with or without its shaft lol, so that doesnt prove much.

With older TR detectors, problems with the lower metal shaft were probably not so noticeable. Especially since it would be masked by the other problems of drift and lack of sensitivity anyway.

[bernte_one]

high pressure water pipe min 16bar 20mm dia lower part 25mm dia upper part connector 20to25

the stem stiff enough to make more stiff cut a second pipe lenght press it a little bit and stick in the one with the same diameter

the pro of this stem NO metal parts very cheap

[DOOLEY]

just thought id chip in ,

a stem made from 20-22mm water / wast pipe to floppy ,
40mm waist pipe not floppy but to big ,

use 20mm internal 22mm external waist pipe from diy (b&q etc...)
and slide in 19mm wood dowling with insulation tape to pad it out.
would have liked 20mm dowling , but cant readily find any.

end result , slim stiff stem , waterproof , and many joining bits available for this common size of pipe.

[Tepco]

This is my favorite "low labor" one: Upper part is from elbow crutch, thin wall Al alloy, 19mm inner diameter. (local cost 11E). Lower part is from "beginners" 3-section carbon fiber fishing rod (5E), diameter fits luckily. Two sections used, inner one wrapped whit glass fiber (boat repair kit) and 2-component resin and inserted in outer section. When hardened, only drill few holes for length adjustment on upper side, and grind down lower side to fit "ears". 10min. of work, very strong and lightweight, even not looking that bad.

[wam]

I have one of this as well but I have turne around handel so the upper shaft is bent in "up direction". I was lacky becouse the Minelab lower shaft was perfect fit for it.
Regards,

[Tepco]

I'm using this in "inverted" position for most of the time too, seems to be more practical.

[Tec]

DIY All the other (non electronic) bits

Attached is my design, it requires some epoxy and fiberglass, all from readily available parts. It's better than most commercial detectors in my Unbiased opinion .

** Note, The most important trick with the epoxy/fibreglass on the shaft is to wrap it all up with electrical tape when it is wet. The elctrical tape will easily peel off later after the epoxy is dry. This will leave a tidy 'epoxy composite' shaft that can be sanded and painted.