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Image Towing a coil....

As I saw a lot of interest over the web on towing coils I decided to show you how I tow my coils. The first photo shows the sled attached to the bike. I fabricated the whole lot from PVC water pipe and a perspex mat (used in offices for roling seats over on carpet).

The photo below is of the whole sled attached to the ATC (a Honda ATC-110 3 Wheeler Bike). the next photo is the same but with measurements explained after the photo.

Whole sled and rear of bike


As you can see the sled total length from the tow hitch is nearly 4.5m long. The mat is 2m long and the connection shaft made from 25mm PVC pipe is 2.3m (These measurements do not take into consideration the bends in the tow-shaft or the mats bend upwards) Notice that I mount the detector in a old foam 'Esky' box to protect it and use an array of pvc pipe to secure it to the mat and shaft. I didn't put in the measurement from the box to the coil (Oversight) but it is slightly longer than the coil would be if you had it on the detector and was walking as normal. Approximately 1.5 metre. I also wound the power cable around the tow-shaft to prevent snags.

Coil Mat

The mat shows the way that it is constructed with the perspex mat and pvc pipes. Starting from the right you can see the MD protection box and how I mounted it. Notice the coil lead is velcro'd at the detector mounts as well as the coil shaft and is kept above out of the way. Under the box you can see a small part of the crossmount that the towing hitch mounts to. The towing hitch is mounted by using a heat gun on the end of the pipe and then squashing it flat using two flat surfaces. I then reheat it and wrap it around the crossmount pvc pipe and using a clamp make sure that it is tight and leave it until it cools solid.The coil shaft mount is done exactly the same. I do this rather than bolting so I can fold the whole lot up and also slide the 2 shafts to left-right positions for storage under the bike on the trailer. The side mounts are bent and also the perspex mat to let it slide over obstacles.Originally the side mounts were also bolted onto the main tow-shaft like an A-Frame, but when travelling over rocky terrain they broke at the mat end by rocks and sticks. Further left along the coil shaft you notice a plastic bolt (lock bolt) that secures the shaft to the mat and prevents it sliding or jumping whilst travelling. I bent the coil-shaft in that fashion for 2 reasons;
  1. To manage diffetent coils.
  2. To keep the coil cable away from the coil. It also serves as a handle when ground balancing.

Lastly the coil is secured in the normal fashion using a nylon bolt. You may have to flatten the shafts a little to accomodate the coil depending on what size diameter PVC is used.

Now we come to the battery and tow-hitch details.

Rear of Bike

As you can see I have mounted 2 x 10Ahr 6V standard batteries to my GPM connector box for the 12V output. This allows me to detect without charging for days. The cable goes down through the tow-hitch to prevent it from tangling on sticks and the like that I may run over and get flicked up. I also wrap it around the towing-shaft for the same reason. You could velco it to the shaft for quick release if you like. I then wrap the headphone cable around the frame so I don't pull it out of the socket.

There you have it. I put my "walking" detector on the back with the coil facing backwards from the rack out along and high above the tow-shaft so it can't get hooked in tree branches etc when I am navigating through the bush! A few things to mention are:

The detector is mounted on the Sled to eliminate any noise from the bike and also to not introduce any losses in extended coil cables. It is better (in my opinion) to have (and easier to make) a good quallity power lead made long than making longer coil cables with joins, all of which could introduce signal strength losses and noise. Another reason is that the 2000 is very susceptible to ignition & electrical noise and this "Almost" eliminates it completely without doing anything to the bike's electronics.

Also with the GPM I have detected nuggets (5gm and above) with a Coiltek 18" DD and Minelab 18" Mono at speeds between 5-15Kmh so you can go reasonably fast when looking for a virgin patch. It will detect smaller but that is what I decided the best receive signal rather than jumping off the bike on every small signal (MANY MANY over rough ground).

Any questions feel free to ask in the forum section.

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