jet-log Lengths

[Bill_saf]

I was wondering if some one could let me Know if the length's in this PDF are ok or to short. The reason that I'm asking is what I had planed on was a 4" but as of things have come about and can only do a 3" with what I have on hand. I found this about a year ago.

View attachment dredgenozz.pdf


thanks
Bill

 

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[russau]

Bill that's a good read on nozzle building! as noted on the "power jet tube length" towards the end of the article , I agree with those tube lengths and should be measured from where the high pressure water enters the jet to the exit of the jet for maximum laterial flow of the water / material. but ive seen where those lengths have been shortened to fit a persons needs. on my4" dredge , I use the 4 inch hose (from the jet to the flair)to make up that length I need to make the 40 inchs .

 

[Bill_saf]

Thanks russ I will do that so I can get a nozzle out of the 46" x 3" steel Tube that I had sitting around ( old drive shaft torque tube out of 1975 ford pick up)

 

[Gelmac]

Not trying to hijack the thread but I reckon Dale Russell (the author of the article Bill has included in his post) has his own design of dredges. Just wanted to know any one has more info/pics or owned one and wanted to share his/her own experience with them.

 

[Timberdoodle]

I do not see a major problem with the main tube length, but I do see some major issues with the other criteria listed for jet nozzle sizing and angles. A 5 degree angle is very steep and great operation can be found in the 10deg-15deg range with 11deg being the most utilized. The jet tube has been listed as the same size from 1 1/2 up to 2 1/2, and listed with 4" using a 5/8" feed. While this can be done, it requires running much higher pressure.
Standards for these jet inlet tubes are generally 1 1/2=3/8", 2=1/2", 2 1/2=5/8" 3=3/4" and 4=1". This allows for good operation from a pump running pressure of 30-40psi and delivers more working volume of water jet for each increase in jet size. The pump volumes listed looked ok.
For reference, I have a 2" keene jet that has a 5/8" jet orifice in the inlet tube(yes it is bigger than 1/2"), this jet orifice passes approx. 75gpm at 30psi. For a 5/8" jet orifice to pass 200gpm in a 4" jet, the running pressure (not max pressure of the pump) would need to be approx. 200psi. vs a 1" jet orifice inlet which would pass 200gpm at 45psi.
I would not build to the listed specs in the attachment. Hope this helps

 

[russau]

Yep the pumps (GPM) and the jets orfice need tobe matched up for optimum performance.

 

[Bill_saf]

Not trying to hijack the thread but I reckon Dale Russell (the author of the article Bill has included in his post) has his own design of dredges. Just wanted to know any one has more info/pics or owned one and wanted to share his/her own experience with them.

Gelmac
I have no idea if he has any dredge designs or not. I was looking for Info on stuff to build a dredge and a high banker and found his PDF and saved it. so if any one wants to save it thats up to you.

but like Timberdoodle has pointed out the jet sizing is off but I think ( I may be wrong ) he just set them up for high psi.

and well I already have my nozzle and jet-log built did them up today I just need to do one or two tweaks on the jet nozzle and Ill be good to go. I did go with the 10 deg at 5 deg the end is to close to the tube.

 

[Gelmac]

Bil, didn't mean to drive the discussion to another way. Just thought along the lines of the topic, the idea seemed somewhat related somehow

I have read but I don't remember exactly where, that Dale Russell has his own dredge design, and after reading the article you provided- thanks by the way- I wanted to know how he incorporated his jet ideas into a dredge of his own design.

 

[Gelmac]

To avoid a double post , I removed a link to a PDF article about one of Dale Russell's submersible dredge designs from this thread.

You can find it here if you're interested :

http://www.treasurenet.com/forums/dredging-hi-banking/277651-submersible-dredge-2.html

Seemed more appropriate there.