Making A Drag Coil From Scratch

[blackjack]

I tend to agree with GotAU? I think wheels or at the very least I guess a sled. I'm just asking the question 'why did someone invent the wheel', my answer would be because they were using a sled. Seems like people have come up with some good options for you N/E keep us informed, on your progress.

[Northeast]

5 hours ago, GotAU? said:

pulling the 40x20 CT Mothership coil

Yes, that is an option.  I am looking for something a little wider though (60" - 72") to really cover some ground.  

[Northeast]

4 hours ago, blackjack said:

I think wheels or at the very least I guess a sled.

Wheels and PVC tubing to make a sled are certainly an option too.  I am trying to keep it really simple for a couple of reasons though.  The first is so that there is less to go wrong out in the field.  Second is that the more moving parts means it is more complex to make and everything needs to be metal free.  Not impossible but harder.   The third is that I will certainly use it here in Victoria on farms, etc, but it is really being purchased to take to the wide opens spaces of Western Australia.  Something like Woody's loop could be easily shipped to my brother-in-law in Perth before I fly across there and he can simply have some conveyor belt and ropes organised. 

The ideas around the sled make up are appreciated but it is more the make up of the coil that is the concept that is outside my boundaries.  I have had a generous offer of assistance from a Prospecting Australia member to provide some info around that and will definitely keep you updated re: if I proceed with making the coil myself  😊

[Valens Legacy]

Grandfather has made some coils for relic hunting using the same method as a prefab vehicle detection coil.

They are 72 in. long by 9  in. wide and work with a 2k detector. The coil is enclosed in 1/2 in. plastic conduit sealed at the corner where the wires go into the pipe. They are twisted together and then ran to the detector which can be up to 50 feet away from the coil. The pipe has 4 lawn mower wheels attached to it on each corner with plastic bolts, so that it would roll across the ground with ease.

I hope this helps with your design, and I wish I was at home to take a picture of them for you but I won't be back there for several months.

[blackjack]

Yeah, I understand, it would be the coil arrangement that would trouble me as well. The rest of it can evolve. after all you'll be the one dragging it.

[Reg Wilson]

The coil attributed to Jim Straight was built by Jim Stewart in Victoria Australia.

[Reg Wilson]

If you are going to go sledding then you need to spend money. No cheapskate option will cut it. 

You need a diesel tow vehicle with an alternator cut out switch to keep the coil close behind. ( a 4stroke will send your detector nuts with interference) A diesel causes no EMI. 

A rigid coil frame attached to heavy duty conveyer belt for rugged or abrasive terrain. (Desert country will shred PVC in no time.)

The right detector for the job. (I have found the GPX 4000 the best option)

These are just the basics but set up right you will easily pick up targets as small as .22 slugs at several inches. Tested on a real big slug (over 90ozs) at over a meter the detector just roared.

[GotAU?]

1 hour ago, Reg Wilson said:

The coil attributed to Jim Straight was built by Jim Stewart in Victoria Australia.

Thanks Reg- I used your suggestion and gave a correct reference to Mr. Stewart in the post.  Jim Straight must have been visiting  and borrowed one. Do you know how successful these were in Victoria?

[Reg Wilson]

Jim Stewart had success with the 'Bismark' but sometimes spent a lot of time digging deep rubbish. James Beatty along with John Hider-Smith and Jim dug a piece over 30 ozs using one of those coils. They broke a pick and took until midnight to dig it out. Jim also built a big DD coil, but it had to be swung slowly, making it useless for sledding as the target response was too slow. 

My sledding experience was nothing to brag about as the best that I achieved was a 6 oz bit. What it did do was to eliminate large areas that could have been productive (but weren't). At least I don't have to lay awake at night thinking about what I could of missed.  

Mono coils are the go for sledding and having tried different configurations I found that round coils worked best for both coverage and depth. With a grid overlap of 50% very little ground was left undetected.

[Aureous]

So far, the only two people who have any experience with 'drag' coils have said 'flat out' that ya gotta mount the thing behind a vehicle. NE, I strongly envisage that you will put the thing together, get it running, give it a try dragging it about in the scrub personally for half an hour, then throw the thing into the back of the ute and curse that you ever thought of it. Hope I'm wrong, but its no fun attempting to pull a wide, heavy object for hours each day.....let alone attempting to dodge bushes, trees and rocks & snapping your head behind you every few seconds to check that you've avoided the last bush or tree. Sounds like a nightmare to me.....