The CD nozzle outlet

Not sure if I'm the first to try this, but wanted to share that an outlet nozzle I found that worked well for my design is a CD. I started with a hole punched in a thin aluminium sheet, which worked well but there were micro striations on the jet. In a later design I was testing with a pipe cap that was domed as that could offer benefits, but I had problems fixing my aluminium sheet nozzle. I then realised that a CD fitted the inside of the cap and had the size hole that I wanted too, so I fixed it in and wow, it worked really well. It also made a cool whooshing sound when the water first started up The CD spindle holes seem to be very clean and free from artefacts, and perhaps the surface contact with the stream reduces if the CD flexes under pressure. Perhaps it'll help someone with their design.

Nick

I've noticed something about CD/DVDs and water:
I don't know if you have tried "washing" a cd with water, drying it and then playing it in a cd (I have kids so I have ) - but you will find that sometimes the water makes its way into the CD as it spins (inertia). I had this happen with a DVD too.. (in fact it wrecked my FaceOff DVD - no great loss )

it appears that CD's and DVD's are actually manufactured in laminations - and just immersing it in a little water then spinning it was enough to force it between the laminations.
I've also some CD's that have fractures on it from the kids pushing a little too hard - considering the pressure of the nozzle I'm not sure if its something to consider.
I don't know if this affects what you are doing - I thought you might want to keep an eye on it.
Mike

Good points. If we still used CD's then my 2 and bit year old would be having fun no doubt; instead everything goes on a server and we stream them with units from Slim devices, and she has fun with those units instead

What would happen long term I don't know, and I may get a metal nozzle machined this year as that's probably the best way to go long term. I'd only been playing with the CD nozzle for a few days before we started major works on the garden and it was all out of bounds for water jet experiments, but it produced a good stream with no striations and near silent landing over a fair distance, so seemed to do the job well. This was on my design without straws, low pass filter and a tangential entry.

The more I think about this, the more I think it is a really great idea. I think I will be trying this on the nozzle I am working on for this Spring. If you use CD-R media, it is basically a solid slab of polycarbonate with a very thin coating of dye, then a very thin coating of metal, then a very thin coating of some protective sealant. I found I could easily strip it down to just the polycarbonate disc. Just use a box cutter blade to slightly scrape the top surface near an outer edge. Then put duct tape on the disc, press it down good, then rip it off suddenly. Do that a few times over different parts of the disk and you will have removed all of the top layers. At that point, you just have a slab of polycarbonate with no real chance of delamination. You have pretty much done a total delamination in advance. Some other types of discs might not be constructed on a solid polycarbonate substrate, but CD-R discs are. Also, polycarbonate is incredibly deformable without breaking. If the disc is placed against the inside surface of the front plate (I am using 3/8 inch PVC for that plate) then I don't think there will be even close to enough deformation to break the disc. (Of course, non-polycarbonate discs might be much more subject to breakage - or just using the thin polycarbonate like it was the top plate might also be a problem.) It will be interesting to see how it works later this year. I have high hopes for it. The biggest down side I see right now is that the center hole is 5/8 inch diameter and I was hoping to use 1/2 inch. Not a huge deal, but I will have to rework some calculations and reconsider pump sizing when I get to that point.


-David

What a great idea using a CD\DVD :-)
Many ppl dont have a lathe to make them self a brass ring, so this is a simple solution !

I just wonder if a CD will hold the pressure from my flow4000 pumps.
When I did try a 4mm glass, it did break

The plus side of having a larger opening will be that the stream should be easier to keep laminar, but the downside is it won't shoot as far, or will need a larger pump to shoot it further.