Sweep Speeds vs. Sweep styles

Just as a thought experiment to consider the difference in coverage between a normal walking sweep with the detector versus walking holding the detector to the side and essentially dragging it along.

Sweeping side-to-side in front would cover approximately 2 feet either side of your center-line axis or 48" of sweep arc. If the DD coil overlap area was 10" x 2", typical for an 11" coil, then the area covered with one sweep is 480 sq inches. Sweeping a med-slow rate of 10 sweeps left-to-right per 15 seconds equals 40 sweeps per minute. Thus the total area covered in one minute when sweeping with an 11" coil is about 19,200 sq inches per minute.

Now, compare holding the coil perpendicular to the direction of travel (lengthwise) so the most coverage is acquired, and just walking (not sweeping). The same med-slow pace would cover about 4 yards (144 inches) in 5 seconds, or 1440 sq inches in 5 seconds, or 17,280 sq inches per minute.

All things being equal, swing the coil in front covers more ground than braced off to one side - but not much more. It is probably conceivable that in target sparse areas where the walking pace could be increased by 10%, this method (braced to the side) would cover ground faster and with much less effort expended (and less sore muscles).

Assuming that targets could be anywhere within a grid area, the second method (braced to the side) would provide as many target opportunities as sweeping, yet with less effort. It would be ideal for fields, along the beach tide lines, or grassy areas in parks and ball fields.

I've done exactly this on open areas - hold the E-Trac coil perpendicular (lengthwise) and just walk in parallel grids until something registers as a possible target. No swinging, covers the same or more ground, and gives the arm a rest from the constant back-and-forth torque. It's also a bit more relaxing.

For instance, applying the thought experiment, we have a farmer's field containing 1 gold coin somewhere within 1 acre of open farmland. 1 acre is 6,272,640 sq inches. It would take 327 minutes to cover the entire acre swinging the detector in front of you as you walk. That's 5 hrs and 30 minutes of detecting (assuming no other target is analyzed) and 6,540 left-to-right swings and 6,540 right-to-left swings to cover the acre and find the coin (assuming it is found last).

The same gold coin in the same field would take 363 minutes or a bit over 6 hours to find at the pace described above. But it would require zero swings. If the pace were stepped up by 10% the times would be identical.

Yes, sweeping in front side-to-side makes sense if the area is trashy and requires analysis but under certain circumstances you would be better served to just take your detector for a med-slow paced walk and listen for a high tone.



Edited 1 time(s). Last edit at 02/15/2013 03:09AM by Johnnyanglo.

Wow!

((( Seems to me........... this would involve a heck of a lot more 'walking'.......... due to only 10" width sweeps. What is the walking distance 'delta' (differential) between the two posed methods? )))

Try making a special coil-mounting bracket so the coil sits at 90 degrees to the norm. Then hold it out in front of you like normal when you go for your walk.

If we round off an acre to 200' x 200'.

At 4' sweeps (200' divided by 4' = 50 passes x 200' = 10,000 ' divided by 5280 = 1.89 miles.

Straight walking, 200' x 12" = 2400" divided by 10" (width of coil) = 240 passes x 200' = 48,000' divided by 5280 = 9.09 miles

So your walking over 7.2 miles more.

Check me for mistakes, it's early.

...but you would be walking at a natural easy pace, not at an uncomfortably slow pace.

When you have arthritis in your hips and dicey knees you want the best coverage for the least walking! But I have been known to cover some extra area that way walking back to my truck.

Heck whatever works comes to mind....coil mounted backwards, walking backwards, using garbage can lid type coils, fast sweep, slow sweep etc. etc.

Read somewhere doing my research that it would take years to completely cover a football field and going by that logic if the coil don't go over it or for that matter from the correct direction you are not going to hear it. Interesting topic and thats why so called worked out areas keep producing even if its just a goodie now and then.

So take your coil out for a walk or a swing and again whatever works...

I have a hunting buddy, and he has been detecting for 2o years, first with a Fisher 1266, then a 1270. He finds stiff too. But if you watch him swinging, you'd cringe. I cringe. I even tell him to get that coil closer to the ground!!! And whe he swings, it looks like he's using a sling blade. I have seen grass actually fly off the coil on the highest part of his arch. I gave him Tom's Inleand DVD to watch hoping that would correct his swing. But he's a 20 year man ans he just AIN'T gonna do any different. So I hunt, and he hunts. And we find stuff. His coil is NEVER under 4inches from the turf. He now uses a F75SE in Boost mode so that, hopefully, is making up the difference.
I'll try to address the Original posters post now. Me? I keep my coil parallel to the ground. At all times. And I make my swings as wide as I can make them and still keep the coil parallel to the ground. I think that my swath is around 6 feet. And I overlap half the coil with each second swing. In other words, I swing back and forth in one coil width. I then advance a half a coil distance and repeat. Now, in the woods and among the understory brush and spalings, all of this is moot. I have to swing around stuff and down into stump holes, and all kinds of obstacles. But even there, I practice to things. Swinging the coil TWICE over one coil-width, and also keepting the coil parallel to the ground. I hope I was even CLOSE to the orginal posters intent. Intersting thread!

Hi,, Just think if you used two Tesoro Umax's equipped with clean sweep coils....Put one in your left hand and one in your right hand and just walk ever so slowly, you could cover 36" at a time....Heck now that's saving a lot energy in my book....It's called green energy saving detecting....Just drag a Compadre off your back belt buckle to cover even more ground...LOL....JJ

jimmyjiver Wrote:
-------------------------------------------------------
> Hi,, Just think if you used two Tesoro Umax's
> equipped with clean sweep coils....Put one in your
> left hand and one in your right hand and just walk
> ever so slowly, you could cover 36" at a
> time....Heck now that's saving a lot energy in my
> book....It's called green energy saving
> detecting....Just drag a Compadre off your back
> belt buckle to cover even more ground...LOL....JJ

,
That's called trolling, should work well if you can stand it!

I’ve tried the “on the side” technique several times, but mainly when heading back to the vehicle, or moving from one location to another. It seems very stable that way, but keeping the coil very close to the ground, very level, and walking with the coil at a constant rate seems more difficult than sweeping.

Using a longer stem, and using a wide “arc type” sweep can increase coverage, but can also be much more exhaustive.

Detecting since Feb, 2010
E-trac with 18"x15" SEF, 13" Ultimate coil, Pro coil, Minelab 8" coil, 4.5"x7" SEF, Sunray target probe
CTX3030 with 17"x13" DD coil, 11" DD coil

Back when I used to yard hunt with my old sov and coinsearch coil I'd walk along on the sidewalks leading to and around the house and drag the coil slowly off the edges and pick up gooodies that normal swinging didnt quite pick up. Looking back I believe the success was in the slower "sweep speed", in those high volume areas. It worked well AND gave my arm a break. Good post JA

*** Seems to me........... this would involve a heck of a lot more 'walking'.......... due to only 10" width sweeps. ***

Suppose, to continue the thought experiment, we were detecting the entire playing area of Soldier Field in Chicago because it was built in 1924 and you know there are a few silver dollars under the grass. So, the playing field is 300 ft long x 160 ft wide, which is 3600 inches x 1920 inches, or 6,912,000 sq inches.That's a big area to search.

If you walk with the coil even and perpendicular to the direction of travel, say off to one side, you cover 10 inches x 3600 inches, or 36,000 sq inches in one pass end-to-end. Because you are walking medium-slow at 4 yards every 5 seconds or 1.64 mph, it takes you 125 seconds for one pass (about 2 minutes). Since you are scanning only 10" of the width of the field (1920 inches) with each pass, it will take 192 full-length passes to complete the entire field. Those 192 passes would take 124,000 seconds, or 400 minutes, or 6 hours and 40 minutes to complete if you didn't stop to rest. To do this you had to walk back and forth lengthwise across the field 96 times for a total of 57,600 feet (96 x 600 feet), or 10.9 miles to recover the silver dollar (always at the very end of the hunt).

To recover the other silver dollar, you walk swinging the coil in front of you with a standard 4 foot arc with the same 10" detecting width. You are sweeping at a normal pace of 40 swings per minute and cover 19,200 sq inches per minute. The football field is 6,912,000 sq inches, so you complete the search in 360 minutes or exactly 6 hours. Since your 40 swings per minute will move you along at 400 inches per minute you are detecting at a speed of 0.378 mph, and it takes you exactly 9 minutes to make one full-length pass. It takes you longer to complete one pass because you are sweeping side-to-side in front of you while walking, a method that is more than 4 times slower than the side-scan method above. In any case, since your search swath is wider you need only make 40 length-wise runs (1920 inches wide / 48 inch swath). It will take you then 360 minutes (9 min x 40 runs), or exactly 6 hours (just a different method to get the same result), to finish the whole field and recover the silver dollar (at the end). You walked for a total of 12,000 feet (300 feet x 40 runs), or 2.27 miles.

Here's the number breakdown:

Side-scan method: 192 full-length passes takes 6 hrs and 40 minutes to complete and you walked 10.9 miles. You never swung the detector side-to-side.

Front-scan method: 40 full-length passes take exactly 6 hrs to complete and you walk only 2.27 miles. But you swung the detector left-to-right 7,200 times and right-to-left 7,200 times over the six hour hunt.

The two methods boil down to a trade-off between walking 8.63 miles further (4.8 times further) in order to avoid the exertion of swinging your arm with a detector attached 14,400 times.



Edited 1 time(s). Last edit at 02/16/2013 03:54AM by Johnnyanglo.

Johnnya your miles ratio came out the same as the acre scenario......4.8 to 1..... glad to see that.

Now, swinging the detector, and switching arms, you get a upper body workout as well as a lower. And, you save money on footwear. Ha Ha Ha!

Coil control is a lot more difficult with the coil to your side.... thats why many people get falsing at the end of their swing. I suppose individual walking strid wouldnt be much different than individual natural sweep speed.

Dew

Brainstorming = Mild to Wild

Wow! (again).

Well thought out post Johnny..

Sweep speed and proper technique is a must for deeper target retrieval..

Thats the trick though is it not...

figuring out your detectors sweep speeds and behavior at different depth's..

Thats why when one test detectos against each other you have to Know the detector inside and out or the test will be skewed...

each brand detector likes different sweep speed's for one...

Keith

The way to do it now is to have the detector built into a motorized cart that is guided by gps to cover the field in the pattern you specify and call you on your iphone when it gets a good signal.......the deluxe model digs it for you, too.

**** ... detector built into a motorized cart ... ****

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You thought I was kidding....

I swing 3 different machines weekly, The CZ20, AT Pro and the XLT, the speed of the swing is different on each machine and sometimes I catch myself swing the wrong speed, but I always swing level and if I shorten my swing from shoulder to shoulder then from feet to feet, I figure I will just cover the ground different, I go 90 degrees , then 45 degrees, from both sides too, some times I walk real slow too, it all depends on how much I want to play with the detector that given day and the amount of find I dig