Nozzel Construction question from a new guy

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Nozzel Construction question from a new guy

Post  gizmomkr on Mon May 16, 2011 10:00 pm

I have read and experimented quite a lot before I got here. No one hates a board full of newb questions more than I.

Well, I an that new guy, and this site has givven me lots of great information. So I thank you all for that.

I have done a test nozzel right now w/ 4" PVC and am actually using a plain old washer as my nozzel.
this gave me suprisingly good results considering I built the entire unit in a couple hours. (and most of that time was waiting for epoxy to dry)

I have a very solid understanding of what the nozzel SHOULD be. It seems like most folks making nozzels are dooing so with access to CnC milling equipment. (or something similar)

I found a guide that told me to buy brass pipe, mount it in a drill and hold sandpaper on the inside of the tube.
I highly doubt this would result in a nice sharp edge. (at least not by my hands)

Can any one point me in the direction of a post or a guide for a decent nozzel that I could make without access to a drill press & CNC ?

If this is really waht it takes, I think I saw a post mentioning a board member who sells th nozzel.

I have built a pan / tilt mount for my jet, and will be controlling things with Light-O-Rama software and standard servo's. All set to music for my Christmas display.

Thanks for any sugestions.

gizmomkr
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Re: Nozzel Construction question from a new guy

Post  jetty on Tue May 17, 2011 8:59 am

Just to clarify, I'm a newb too and have built a 10 inch tube. For the first time yesterday I got reasonable results, and perfect output at the nozzle end, i.e. no striations at the start of the stream in the first 4 feet with my latest nozzle design.

95% of getting a good laminar stream is the quality of nozzle.

It's was a very windy day, about 50 km/h, so stream was breaking up near the top, so I need to retest in no wind, but the output from the nozzle was perfect for the first time.

Here are things I tried and the ultimate solution for me. Note I'm using a 1/2 inch plastic top plate, with a hole that's bigger than the nozzle so it doesn't touch the stream.

1. Stainless Steel washer countersunk with a wood bit. Obviously bit blunted fast. I rate this on a 1 - 5 scale as a 2, lots of striations. Laminar for a few feet.

2. A sheet of thin brass from a local modal shop. 0.002 inches thick. Punching it didn't work (hole not even). Ended up making the hole by using a wood brad point drill (good quality one). You need to drill through it slowly. Made a very nice hole. DO NOT HOLD SHEET OF BRASS BY HAND WHEN DRILLING, can get painful :-) I'd rate it as a 3, still had significant striations. Laminar to about 1/2 way. Sheet was duct taped (smoothly) to the inside of the top plate.
If you could get the perfect hole and sand it sharp, it probably could be made to work.

3. Stainless steel washer, drilled and ground with a 3/4 diameter conical shaped grinding stone. Looked good, I'd rate it a 3.5, but still no where near perfect. Nozzle was superglued to the top plate (not recessed). Very difficult to build, round wash in square vice don't work too well.

4. I finally broke down and purchased a Taig Mini Metal Lathe. (overkill, but it's a great tool to have). Built a nozzle from 1 inch diameter brass rod. Drilled a 1/2 inch hole in the rod. Countersunk with a 3/4 inch metal good quality countersink. Cut off the piece at 0.1 inch. It made a very sharp edge (can cut paper), and the design looks like a countersunk washer. Used a spade bit to create a 0.1 inch recesses in the top plate and superglued in.

IMHO, bottom line if you haven't got the tools, then get one machined or buy one of John's nozzles, you need that level of quality. Needs to be perfectly round, sharp and all in the same axis. If you're located in Canada or US, I can make you one for the cost of the brass (say $1 per washer) to your specs (up to 1/2 inch diameter) + postage, just message me directly, they only take about 5/10 mins to make.

Use of superglue probably seems weird, but you can easily break the bound with a chisel of small screwdriver, as it doesn't bond well to PVC. Much easier to use than goop, epoxy, polyurethane or caulk. It needs to be a glue that stays put, doesn't get onto the nozzle edge, dries fast and is removable.

Things I've noticed along the way:

Make sure no water can get around the nozzle into the stream. Once with the duct tape and the brass sheet, I had a slight leak causing a drip into the front of the washer into the stream. You can see it if you look at the nozzle and you get regular interruptions to the stream.

Flow rate. If it's only laminar to 1/2 way and that's the best you can get, then use an adjustable valve to reduce the length by half, then it will be completely laminar.

Bleed all air from the tube. I'm using an irrigation Drain Plug.

I'm using a tangential input. I've tried with nothing in the first 3 inches and a cylinder of foam in the first 3 inches to allow the water to rotate around the center. Got significantly more distance with the cylinder of foam.

Volume. Try not to kill your volume. Keep hoses short and big. I'm using a short length of flexible hose for the last foot (saves strain on the tangential input) and strong walled PVC. I've made sure that nothing reduces the diameter, including fittings and valves. This gives the biggest arc.

Pump. Don't believe ratings. I picked up a 2500 GPH pump from rona and a 1500 GPH Pro Pump from Home Depot. The 1500GPH outperforms the 2500, the arc is further on the 1500 and there's virtually no low frequency effect.
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