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Author Topic: Le trap question  (Read 6517 times)

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Offline goldbrick

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Le trap question
« on: May 03, 2007, 07:51:19 PM »
Hello from Oregon. I bought a Le Trap to run the concentrates from my 6" dredge, but have been playing with it in the creeks this winter. I adjust the angle and amount? of water according to all the advice on the net but I have a problem with uneven flow at the head of the box sweeping parts of the upper riffles. I built a puddle box to use with it and that works great but still the upper riffles  are partially swept if left running with no material for a few minutes. I don't think I am losing any gold as I sample my tailings and never find any gold. Just wondering if other people have this problem or it's just me.
Goldbrick

Offline gangesex

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Re: Le trap question
« Reply #1 on: January 06, 2008, 03:04:48 PM »
Le Trap is a simple effective sluice that just works, however i have noticed the same symptoms as well with ours. I have just shut the valve off for the water supply if its gonna run for any length of time with no gravel loading. Any sluice isnt good to have clean water running over your cons for a while with out any gravel added.

Offline Bob

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Re: Le trap question
« Reply #2 on: January 13, 2010, 06:01:14 PM »
Hi goldbrick, I have a high banker with a letrap on it, i have issues with leveling the unit at the start and the amount of water needed for the material running thru it but when its set it works awesome. Maybe if you posted pics for us we could help.

Offline picker

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Re: Le trap question
« Reply #3 on: January 14, 2010, 09:45:25 AM »
Hi Goldbrick,

Not to worry, The three drop riffles at the flare section of the La Trap sluice is ware you should find most all of your gold. Just try some # 8 Bird shot #14 is even better, if the shot washes out...slow the water velocity..raise the tail race.

What you are seeing is the cleaning action of a drop riffle the way it is suppose to work. if you were getting any gold it would still be in the riffle even after the black sand is washed out. the material in the drop riffle will move sideways as water currents change within the riffle...parts of the riffle are not being swept out, but rather concentrated to other areas of the riffle as the lighter material is cleaned out of the riffle. 8)

The longer you run the sluice without adding material is only going to concentrate the material in the sluice.
this is how it was meant to be used. once the gold is in a drop riffle is is quite hard to lose any!!!

Offline muconium

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Re: Le trap question
« Reply #4 on: January 14, 2010, 11:40:57 AM »
I know my letrap is working when my first three riffles start to turn pinkish-black. Pink from garnet sand and black from hematite/magnetite. It's true, those will not wash out unless you step near the intake and get a surge of water... Anything heavy that falls into a drop-riffle will displace something of lighter specific-gravity, which then gets trapped further down in the letrap. If you have doubts, just clean it out and save your material more often. Then take it home and pan it out.
Rusty dirt makes me drool.

Offline rkockx

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Re: Le trap question
« Reply #5 on: March 14, 2010, 10:53:34 PM »
Hello,
Has anyone built a header box for their letrap and put a rubber matt down to moderate the water speed?

Offline fatkat

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Re: Le trap question
« Reply #6 on: March 16, 2010, 03:18:44 AM »
several people have beaten me too it !

though my sluice is not a le trap its similar in construction ......

I also look out for a change in colour of the cons in the top drop riffles to those lower down ....mine are darker at the top [black sand] and tan coloured lower down [quartz sand ?]

I let my sluice run for twenty odd mintues after the last  input this allows any of the lighter material to make its way out the bottom of the sluice before I start to clean up ....

having also tested my tailing with no gold found..I must also conclude that the sluice is working as it should ...

its very important to get the right flow....down the sluice    both angle of drop and  making ceratain its pretty much level....if its not level then  you can see how the water is deflected in a zigzag fashion down the sluice by the scouring of the riffles .....

now one tone occasion I took the time to closely watch what the sediments were doing    ...it was clear that scouring was happening ..but the heavy material was not being lost  but rolling [vertically]  back along the drop riffle ...the lighter material  rolling with it    as this came near the edge of the scoure it was thrown up [drawn up] and ejected into the next drop riffle zone ..

whatching this was quite mesmeric and I found that  several minutes had passed ...!     

I've actually found it quite hard to get the right angle in my local river as  the bed rock is close to the surface of the stream ...and theres often not a huge flow of water either .....

my promac  standard sluice  does not work at all well in these low flow  and limited slope conditions  hence the purchase of the drop riffle sluice

Offline Al in Ogden

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Re: Le trap question
« Reply #7 on: February 05, 2011, 01:00:24 PM »
Hello,
Has anyone built a header box for their letrap and put a rubber matt down to moderate the water speed?

I have a long rubber mat attached to my LeTrap dredge at the header box exit. It works well for smoothing the flow through the sluice.
Al