Rocker Box?

[Duckshot]

Thanks for the link Old Bookaroo.

If you make it rigid then, as the rocker is tilted, the sides/edges will alternate being shallower so concentrates will be subject to spilling over the edge. A cloth apron pretty much maintains a consistent shape as the slurry shifts from side to side. Canvas is probably as good or best since it is durable but over time and use any cloth will need to be replaced.

O.k.

Im trying to wrap my head around this without actually having something tangible to play with. Are you saying that the cloth apron acts like the arm of a pendulum, becoming steeper on the edge as the weight is moved towards the side edge and less steep on the side opposite? If so, there is a solution to a rigid apron- make the dump edge round instead of straight... ...maybe.

IF I took a gold pan , held it at the proper angle, then dumped slury into it while moving it side to side in such a way that when slury is added it displaces the slury in the pan, would it catch the denser parts of the slury while the less dense material spills out, or not? I think it might.

Or, do I still have no clue how the apron works?

 

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[deserdog]

If you are using a gold pan analogy, imagine a gold pan with a flexible, saggy bottom. As the pan goes back and forth, gold on the bottom would not only have to climb uphill, but it would have to make it up an overhanging edge formed the the movement of the pan.(Keep in mind the pendulam, as the pendulam swings back and forthit would form an ovehanging edge, and this edge would be facing the movement of the gold. )

 

[deserdog]

/_____(overhanging edge formed by movement of pan) o(particle of gold) <----(motion of pan and particle of gold)
Now when you move the pan the other way, the opposite wall forms the overhaning edge)

 

[Duckshot]

Yes Deserdog, i think I get that. But the gold pan I was describing is not rocking, it is reciprocating side to side...

 

[arizau]

Thanks for the link Old Bookaroo.



O.k.

Im trying to wrap my head around this without actually having something tangible to play with. Are you saying that the cloth apron acts like the arm of a pendulum, becoming steeper on the edge as the weight is moved towards the side edge and less steep on the side opposite? If so, there is a solution to a rigid apron- make the dump edge round instead of straight... ...maybe.

IF I took a gold pan , held it at the proper angle, then dumped slury into it while moving it side to side in such a way that when slury is added it displaces the slury in the pan, would it catch the denser parts of the slury while the less dense material spills out, or not? I think it might.

Or, do I still have no clue how the apron works?

As an example of what I was describing: Your imagination of a rigid apron is basically the same as the cross section of a box. When you tilt a box on it's corners (pivot it when fixed in a rocker box) two things happen and those are that 1. It's sides are not the same height when measured from the surface it rests on and 2. Now the sides, when you look at them as a cross section, are no longer vertical and the low side effectively forms a ramp since it is tilted leading to contents being spilled over the side, etc. A loaded apron pocket's bottom rolls from side to side but the pocket's contents pretty much retains their depth, angles and volume while it is doing that. Hope this is something you can visualize.

 

[Old Bookaroo]

If you are seriously interested in using a rocker, I'd highly recommend The Gold Rocker Handbook published a number of years ago by KvonM.

If you can't locate a copy send me a PM and I'll see if I can locate one for you.

Good luck to all,

The Old Bookaroo, CM

 

[deserdog]

The book is Gold Rocker Handboo by Tron Miller, introduction by Mueller. They are hard to find now, and expensive! Great book on rockers though!

 

[N-Lionberger]

I'd think the denser the cloth the better, if it could drip through you're gonna lose the fines. I have used the astro turf in my dredge header but not in a rocker. i used the kind with the little circles of blades of "grass", it holds a LOT of heavies.

 

[IMAUDIGGER]

Not everybody has fine gold in their pay gravel....I bet the rocker works crazy good for areas with chicken scratch gold.

 

[coolfinie]

@Deserdog:
I'm trying to get a better idea of how much "belly" the canvas section should have.

If the rocking stopped during use and everything was allowed to settle with material in, how much would the middle be below the sides at that place?
If this were done with the box empty before starting, what would the "droop" measurement be approximately?

 

[arizau]

coolfinie

Years ago a hardcore rocker box user/"builder for sale" over on the GPEX forum described how he made his aprons and this is my visualized version of how he made them....

Cut the cloth oversize and lay it over the frame and temporarily tack or clamp it when there is an equal amount of depth along the frame from front to rear and side to side when you press straight down at the center points of opposite sides at the same time....I would start with about 2 or so inches of depth below the frame. Now pull the cloth out on one end only including about an inch along the adjacent sides so that the depth is about the same as the height of the frame when you press down and tack it on the side. Now go to the center points of the sides and pull the cloth up until it is only about half as deep as the average between the deep and shallow end (frame height X deep end depth, AFTER IT IS REMEASURED, divided by 2) and tack it. From this point you can pull the cloth out from corner point towards the center points and adjust them so that there is a gradual change of depth up or down to the deep and shallow ends of the frame. This is probably easier to do if you have a matching frame piece lightly clamped on top of the main one. TIP: Suspend the frame and put a rock or something in the apron to keep it stretched while you are making all the adjustments.

It goes without saying that you want some sag BELOW the frame most of the way around. When you set this frame in a rocker it will not need a steep angle...Maybe 1" in one foot just like the starting point for stream sluice setup. If you find/feel that the sag at the deep end is too deep or shallow then adjust that end and re-taper the sides...I would still maintain the original depth on the high end. With this design the apron will not pooch very much or at all under the low end of the frame when it is loaded and probably not abrade very much with use but keep an eye out and remake when needed. The whole process may take a few tries to get it right.

I hope this helps and Good Luck

PS: Make sure you have a diverter above the apron section so that the apron is fed only in the area of it's highest end. That insures that the material and gold is fed into the shallowest water filling the apron so the heavies are already pretty much on the bottom.

 

[arizau]

I've made some edits/clarifications to the above post so previous interested readers may want to re-read it.