Gravity dredge specs?

[Ragnor]

I used the seach function and didnt find anything useful. I'm sure allot of people forget to ad tags to they're posts and the don't seam to be able to be added in the edit feature. So, anyway....

I have found some stuff on syphon operated designs, but that's not what I'm after.

My idea is to make a run of 1-1/4" poly pipe up hill from from a bench to the stream on the edge of my claim. I'm wondering how to calculate head pressure and gpm flow from elevation drop and pipe diameter. I know there was a real good table for that on Mike Higbee's sight but Ive been unable to locate one here.

Anyone have a link to a table or care to lay out the formulas?

I'm thinking on how can I run a dry land dredge on a high bench without using a pump?

 

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[motohed]

You maybe to look up some formula on a plumbing site under head pressure etc , I'm not quit shure how they will work . It would depend on stream or river flow , gallon per minute etc . I'm shure you would have to catch a large amount of water and funnel it down to size , the closer you get the main feed reduction to your dredge the better . I would also consider a holding tank then pipe it to your dredge .

 

[SpecJet]

2.3 Feet of head = 1 Psi

Calculate your head pressure and use this link, input orifice size and pressure and it will give you flow in GPM.
Calculator: Water Flow Rate through an Orifice | TLV

 

[winners58]

this is a compilation I think its from the early 90's its a save from the old 49erMike website so you may want to copy/paste and save the info.
A Gold Fever Experience - Gravity Dredge Plans - Olympic National Park

 

[Laz7777]

Ragnor: spelling is "siphon" not "syphon", might help in the search...winners also posted his link for another name for it: gravity dredge.

I'd like to know if anyone has any info on legality of one in Cali, have listened to discussions both pro and con, mostly running nay, though.

 

[winners58]

seems like if you could get the water to where you wanted to work you could use the weight of the water and siphon to a sluice box.
.

 

[Laz7777]

a few years ago, saw a guy on the South Yuba using a creek with a drop as his gravity, and a T from that hose to/from the crash box on his sluice.
tod me it was working, but draw was slow. not sure, but think it was 3", and I'm fairly sure he had no nozzle, which would have helped.

 

[Goldwasher]

legal in california. There's no motor

 

[Ragnor]

2.3 Feet of head = 1 Psi

Calculate your head pressure and use this link, input orifice size and pressure and it will give you flow in GPM.
Calculator: Water Flow Rate through an Orifice | TLV

Well if I understand it correctly I get ~308 gpm at ~100psi on a 250 foot drop. I recon that would power a suction nozzle just fine.

 

[SpecJet]

With that much head, you can power just about anything.

 

[GrizzlyGremlin]

Well if I understand it correctly I get ~308 gpm at ~100psi on a 250 foot drop. I recon that would power a suction nozzle just fine.

Holy smokes man! 250' of head!! Yeah that'll do it haha! You could use that flow to do some hydraulicking! Too bad its illegal.
Seriously though ive gdredged bank pockets, and it seems to me that 1' of drop for every 6-10 feet works out just fine.
250' is crazy!

 

[Timberdoodle]

Well if I understand it correctly I get ~308 gpm at ~100psi on a 250 foot drop. I recon that would power a suction nozzle just fine.

Sorry Ragnor but wrong calculator for what your looking for. First thing you need to know is the flow requirement (size dredge nozzle). You have plenty of head pressure but the volume speed of flow is limited based on the pipe size or you will loose pressure to friction losses.

1 1/4" line 500ft long could supply around 20gpm without much loss but that's not enough volume to run a nozzle.
3" line 500ft long could supply 200gpm with a little loss (15psi) and could run a 3" nozzle good.

This calculator is fairly good and you can try different sizes etc.. unfortunately it doesn't have 1 1/4" pipe size, but basically that idea is out anyway.
Liquid Friction Pressure Loss

The piping design calculators in the TVL site look good also. Try "pressure loss through piping"

 

[Hoser John]

http://www.waterboards.ca.gov/water_...ghbank_faq.pdf read and weep-John

 

[Ragnor]

Thanks, I wondered about that. I seam to recall Vortex Rex lamenting friction losses in his designs back on the old 49erMike forum.