starting a build for a robotic dredger

[Fermion]

Hi guys,

I am an electrical engineer with a hobby of mechanical engineering. My wife is a software engineer who does most of the microcontroller programming and UI in our past projects.

We have been interested in gold prospecting just for fun for several years, and watching Bering Sea Gold has us thinking of merging some of our past robotic projects with the idea of gold dredging.

It is somewhat hard to calculate if this is a viable project. The fun factor would convince me to build it if I have a chance of at least recouping materials costs. I already have a very large cnc bedmill and lathe in my shop, plus plenty of electronic test equipment.

The robot would allow the dredge hose (considering a 6 inch hose) to be remotely operated underwater with several cameras and lighting to give feedback to the user on the surface. Ideally it would be very suited for dredging under the ice as the entrance hole would not need to be much larger than 12 inches and possibly could be made with an auger. This would save time when spot checking several sites. All of the exposed parts of the robotic section would be made of stainless, delrin and rubber.

I intend for the robot to be controlled by a human but will have some canned sweep programs to allow it to run semi-autonomously. It should be able to grasp or nudge boulders up to about 300 pounds.

One of the sticking points is actuators. I am unsure right now what would be the best choice. I have considered hydraulic, pneumatic, hydraulic using pneumatic cylinders, and electro-mechanical (ballscrew/servomotor) actuators. It might be best to proceed on this project by developing the actuator and cycling it under load at depth pressure in salt water for several hundred hours to make sure it is robust. Once the actuator is proven, the rest of the robot is somewhat trivial as is the programming.

Anyway, if you have any ideas or suggestions as to approaching this project, I would be happy to hear them.

 

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[Fermion]

A cone or dome with grizzly bars and additional scissor bars is sort of what I had originally envisioned, but from what these experienced dredgers are saying, that may not be enough. I can now see how small rocks could form an impaction jam against the bars. Maybe if the actuated scissor bars are designed correctly they could release this. It might be ok just to have the scissors cycle every few seconds automatically even if there is no obstruction just to free the operator on the surface from this task.

How often does a 6 inch dredge jam inside the hose past the nozzle if bars prevent objects larger than 3 inches from passing into the hose? Once every few hours or is this a constant issue? If the snake can perform some fairly rigorous twists, I wonder if that might be enough to clear those type of jams...

The idea of a flat hose that is inflated to try and clear jams is interesting, but I worry that anything that impedes the flow of material once it gets past the nozzle might do more harm than good.

 

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[Fullpan]

Please know there has been this problem since small scale suction dredges were invented over 50 years ago. The best technology invented so far, has been
a restricter ring welded at mouth of suction nozzle that "closes" the opening by 15-20%, along with a suction-killing flap mentioned earlier. An experienced
dredger, with this set-up, will process 100 times more material, than a new guy. He knows to keep a sharp eye for rocks that will plug, he knows how to
keep a steady stream(not too much and not too little) of gravel and sand heading topside, and he knows to toss bigger rocks out of the area, so the hole
does not become "boulder-bound", and he does these things as fast as he can for 2 to 6 hrs per dive. Manual labor has been replaced by robots in many
industries, but they knew the design parameters they had to overcome. Please carefully watch all the utube and reality shows you can. You will see good dredgers and poor dredgers. Take the knowedge and run with it. P.S. the windshield wiper approach
sounds good til you realize the stuck rocks will fall right back where you are trying to suck.

 

[Lanny in AB]

A cone or dome with grizzly bars and additional scissor bars is sort of what I had originally envisioned, but from what these experienced dredgers are saying, that may not be enough. I can now see how small rocks could form an impaction jam against the bars. Maybe if the actuated scissor bars are designed correctly they could release this. It might be ok just to have the scissors cycle every few seconds automatically even if there is no obstruction just to free the operator on the surface from this task.

How often does a 6 inch dredge jam inside the hose past the nozzle if bars prevent objects larger than 3 inches from passing into the hose? Once every few hours or is this a constant issue? If the snake can perform some fairly rigorous twists, I wonder if that might be enough to clear those type of jams...

The idea of a flat hose that is inflated to try and clear jams is interesting, but I worry that anything that impedes the flow of material once it gets past the nozzle might do more harm than good.

The bars will stop big rocks from entering, but they will suction-clog as bigger rocks or flat rocks are encountered. While dredging, as fullpan mentioned, I'm always moving rocks out of the way that I estimate will clog or obstruct the nozzle. Even with that, sometimes oblong rocks will enter, then flip crosswise and then start a chain reaction jam in the nozzle or in the hose. Then there's slides and slumps of material that will overwhelm the nozzle as they're unpredictable, and often you can't get the nozzle out of the way fast enough.

If you watch some of the video from Bering Sea gold you'll see how they're very careful about what they send up the nozzle, and often, especially with the bigger dredges, they're pulling in a small stream of material--they're not hogging it up the nozzle as would happen by just thrusting the nozzle in among the cobbles.

I still feel if you want more ideas and input you should post this on the dredgers forum. You'll get a fresh perspective that way. I've always admired inventors and fabricators--they often find a method to get things done that others have never imagined. With the right input, you may be able to invent just such a robotic dredge--but at least you'll get a lot of input on the realities of dredging.

All the best,

Lanny

 

[Fullpan]

A more positive suggestion - the dredging environment has mostly been rivers where changes in bedrock (waterfalls, rapids, deep pools, steeply sloping side
banks) were not applicable to pre-classifying material, it seems the Bering Sea claims are more like a farmer's field, and farmers have been removing rocks
and boulders for a hundred years. If you can develop a "rover-raker" to work ahead of suction hose to remove (rake aside) most oversize material, then
you're going to have a much simpler operation. BTW does the "rumba" (the automatic vacumn) really work, or is it just another
impractical "gadget"? I never seen one up close.

 

[Fermion]

Thanks Lanny. You and others have opened my eyes quite a bit to the complex tasks a diver needs to perform to efficiently move material. I apologize if I came off sounding like I had it all figured out. The only part I know I can do based on past experience is the software, electronics, and actuators. It sounds like these may not actually be the hard part.

Is it worth pursuing? For the very specific application of dredging under ice, maybe? The snake could go places a diver might not want to be such as closer to the shore where the turbidity limits visibility and the bottom to ice zone is narrow. The snake would not get hypothermia, die from a tangled air line or falling ice block.

But we are talking some significant expenditure. I estimate a working prototype snake capable of carrying a 6 inch dredge hose in it's gullet would be around $10,000 to $20,000 depending on how many parts I use off the shelf vs fabricate. Then I would need a generator, dredge, hose and pump, yurt, and something to tow it out on the ice (although slight possibility the snake could pull it's support equipment across the ice on a sled). Oh yes, and I would need an ice auger. Then I need to have all of this shipped up to Nome. Before all of that, I would need to secure a claim to dredge.

Really giving me a reality check, which is good.

BTW, what do you mean by posting on the dredge forum? Do you just meant the section on this website? Thanks again.

 

[Doug Watson]

Another idea you might consider if you can work past the nozzle problem, is what they call a suitcase dredge. There were some versions posted in the past on the Alaska Gold Forum and I believe yahoo gold miners forum. That would eliminate the suction hose to the surface and the surface sluice box. The major problem is the amount of work that the diver actually does. Like has been said, the diver is constantly working to move rocks, controlling the feed rate, watching ahead, etc. Dredging is hard work! Good luck on your project.

 

[Ace2010]

Even with restrictor bars over the nozzle with only three inch holes you will still have jams up the hose.The long skinny rocks are what causes the most hose jams.I've never dredged in the baron sea but here in Alabama we have alot of slate that breaks off in long skinny pieces.With this hose inside the snake I just don't see how you will be able to get the jams out 10-15 feet down the hose when a long skinny rock jams sideways with the next 5 minutes of every small rock packing up against it before you cut the power.
I didn't read every post but was wondering how this mechanical stuff is going to last long in the salt water?

 

[mjarvis]

Very interesting concept - "sounds good on paper". I like the idea of starting small, like they do on "Myth Busters" show to demonstrate "proof of concept"
and "repeatability" before gearing up. Remember that at least half of the effort "down there" consists of "rock chucking", that grasping odd shaped cobbles
weighing from 2 lbs up to 60 lbs and more, and chucking them as far away from suction nozzle as possible. Hope this helps.

Hello full pan.

Do you need a permit to pan or sluice in the Amercian River??

 

[FC-Treasure]

I'm not a dredger, but I was really struck by what Lanny said about clogs. He could have been describing my problems with vacuuming leaves out of my pool. It is maddening, especially the clogs in the hose. I too spend a lot of time either hammering the hose to free clogs or cleaning the nozzle.

I have wondered what would make a robotic pool cleaner any better than a human. Maybe most people don't have their pools under trees, with the stick, leaf clog problems.

 

[bill-costa rica]

Another idea you might consider if you can work past the nozzle problem, is what they call a suitcase dredge. There were some versions posted in the past on the Alaska Gold Forum and I believe yahoo gold miners forum. That would eliminate the suction hose to the surface and the surface sluice box. The major problem is the amount of work that the diver actually does. Like has been said, the diver is constantly working to move rocks, controlling the feed rate, watching ahead, etc. Dredging is hard work! Good luck on your project.

a suitcase dredge is a neat concept , but does not save fine gold well. the suitcase dredge is pretty new to north america, but very old news in new zeland where the idea sprang from. they work well with a small motor and pump and are very cheap to build.

bill-cr

 

[Lanny in AB]

Here you go Fermion: Dredging & Hi Banking

All the best,

Lanny

 

[improvmechanic]

Another thought I just had, you're going to need some testing on the hose. I don't know if it'll hold up in the joints. I can't see a 6" hose bending past 45 degrees and staying intact.

This concept is a real mental workout. Thank you!

 

[Fermion]

I will look into the suitcase dredge, thanks.

It may well be that the robotic snake project is a little ambitous due to my lack of dredging knowledge. Perhaps constructing a suitcase dredge would give me some valuable experience on a smaller scale and budget. I can't take this 7000 pound cnc mill and lathe to Alaska when we move up there in 2 years, so I am itching to do some builds now while I have the tools.

 

[Doug Watson]

If you can arrange to get on the nozzle of someones dredge for a day or two most of the issues you aren't fully aware of will come to light and would give you a huge advantage over starting from scratch.

 

[Aurabbit79er]

I had an epiphany while reading this thread. Sometimes a picture could be worth 1000 words or in this case I hope it's worth 1000 nuggets.

 

[1more4me]

Um, VMI Dredges makes just what you are looking to make. I think it's called a Rock dredge, but may be a sand or mucker with attachements. Eitherway the gigantic head with two augers down the side roll off all the bolders and big rocks a push the desired material into the suction path. There is no limit to the number of sensors or pressure switches and reverse or dump valves the theing could have- program it to burp hard if pressure drops.

My bright idea is to have two suction hoses or paths. The trailing head be wide like a vacuum cleaner head and a grate inside that rolls. Anything that holds on is rolled to rakes near the top back of the head- ie-a grain combine that retracts it's rakes or teeth.

Just remeber- the fancier it is the more often it breaks and the more expensive it is to repair! That's why dredge ops have evolved this far and no farher... Unless of course you got money like Noble, FCX, Newport, etc...
Good Luck!
PEACE

 

[postcode]

Hi. I also have ideas about mining with a remote system and the issues needing to be solved using a suction dredge. The biggest problem seem to be, If you remove the diver you get rock blockages at the hose intake. I have thought about all types of plough nozzles but putting the work of the trammel on the sea bed is my latest spark. What about building something like a combine harvester, seems to fit the criteria. A front rotating blade feeds rocks onto a belt that removes the larger rocks and sends the fine to a hopper for suction. Its not possible to refine such a vehicle unless you trial and error it. Even NASA have to trial rovers before takeoff and they spend billions on brain power, Tweaks will have to be made. When you put ideas in a pot you sometimes come up with an idea you all didn’t see. Good luck

 

[azman67]

Hi Guys I think I have figured out how to build the under water robot dredge nozzle so it woll not clog. Picture a huge auger bit with a larger center pipe, this center pipe sucks the gold and material to the sluice box. The digging tip of the auger is 12 each 3 inch pipes in a circle about 30 inches in diameter. The tips of these 3" pipes touch the ocean floor and they all have several at least 3 each 5/8" square solid bar weld on at an angle that they slide over rocks and larger material. Also these 5/8" bars are closer together at the front than they are at the back so as they scrape linearily across the ocean floor the small material gets sucked up and the rocks that are to big will get scraped off the sepuction tip of the pipe. This constant scraping will keep the 12 each nozzles clean and clear to suck less than 3/4" material to the underflow sluice box.
My design also uses a bi-directional front auger to push larger rocks to the side of the robot. My design has a hydraulic screw drive 8' x 18" screw augers on either side to manuever the robot on the ocean floor, forward, reverse, spin right, spin left.
My design has video cameras and lights.

A video of my design can be seen here...



I am planning on building this robot asap!
Thx

 

[KiddoTheMiner]

I thought vex robotics was hard, it took us 200+ hours(5 kid team) to build a robot that could put bean bags in trough by remote control
your robot ought to take ten years to develop and prototype!
like the idea though, ambitious

 

[Sick4gold]

How's the ol robotic dredge coming along nearly 2 years later...
Yeah...