Rifling Design - Machining Limitations
Rifling Design - Machining Limitations
(OP)
Hi there,
I am looking at adding a rifling design through a fluid cavity to "swirl" the flow as it passes through. Does anyone know what is the size limitations to manufacture this feature? Diameter, Length, Clearances, etc....
Thank you in advance for your help!
-Paul
I am looking at adding a rifling design through a fluid cavity to "swirl" the flow as it passes through. Does anyone know what is the size limitations to manufacture this feature? Diameter, Length, Clearances, etc....
Thank you in advance for your help!
-Paul





RE: Rifling Design - Machining Limitations
See 'Francis turbine' and 'volute'.
That said, rifling can be produced with broaches. See 'broach' .
A certain Arsenal near my hometown used to make cannons.
BIG cannons.
The barrels were rifled by pulling broaches through them with a cable.
There were a series of, I think, 31 broaches, to be pulled through in sequence, in order to produce some pretty deep rifling in a pretty big bore.
I've been told that the engineers couldn't figure out why the last, final, broach lasted half as long as the rest.
I've also been told that everyone in the facility, except the engineers, knew that the production crew only used half the broaches on each barrel; i.e. barrel N got broaches 1,3,5,7, etc.,
and barrel N+1 got broaches 2,4,6,8, etc.,
but every barrel got the last, finish broach, which duh, wore out faster than the rest.
Mike Halloran
Pembroke Pines, FL, USA
RE: Rifling Design - Machining Limitations
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Rifling Design - Machining Limitations
Assuming he meant rifling, it may not work to induce much swirl in the bulk fluid, unless the rifled bore is also lined with a plug, so that _all_ the fluid gets some rotation.
Depending on the fluid, given a bore with a central plug, it is also possible to produce a rifled annulus by inserting helically twisted vanes between the plug and the outer wall. That may be cheaper than rifling a thick tube, though producing the correct blanks, e.g. laser cut arcuate flats, and twisting them correctly, could be interesting. Perhaps the blanks could be equipped with ~1T wide tabs inserted in radially drilled holes in the plug, secured by tack welds, maybe with the whole core assembly having its OD trimmed in a lathe to fit the big tube, and retained by welding or some other means.
Or just have a radial volute fed with a tangential inlet, and a simple central axial exit into a simple tube, sort of like one element of a Lee Visco-Jet(r), which would be much simpler to fabricate. That's a good example of tangential entry to a prechamber.
Uh, Paul, are we understanding your wishes correctly?
Mike Halloran
Pembroke Pines, FL, USA
RE: Rifling Design - Machining Limitations
But- all of these parts are made using very specific tooling, custom made for each application; they are mostly either small and made in giant quantities (think handgun barrels) or very large and made in small quantities for a customer who isn't cost sensitive (think artillery piece or tank cannon barrel).
So the real question is- what do you have to spend and how many parts are you making?
If you're making 1 of this widget, this will be prohibitively expensive. If you're making 100 million, it won't be.
RE: Rifling Design - Machining Limitations
MY hole diameter is 0.22mm (0.00866in) and 1.03765mm (0.040852in) long. The effect I am looking for is shown in the attached .jpg. Hope this helps clarify any confusion.
RE: Rifling Design - Machining Limitations
Look at the illustration captioned 'Mixing Action' on this page:
http://www.theleeco.com/electro-fluidic-systems/sp...
Just use half of one Lee Viscojet pair; only the entry swirl generator, in roughly the proportions shown.
It still may not do what you want; at low Reynolds number, the flow in the swirl generator will just go radially from the tangential entry right to and through the central hole.
At least it's relatively easy to machine, for someone who does small holes for a living.
Mike Halloran
Pembroke Pines, FL, USA
RE: Rifling Design - Machining Limitations
Wow, that's a small bore. Helical broaching would be very difficult. Maybe EDM?
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Rifling Design - Machining Limitations
I'm sure he's skiing on God's mountain now.
Mike Halloran
Pembroke Pines, FL, USA
RE: Rifling Design - Machining Limitations
RE: Rifling Design - Machining Limitations
Mike Halloran
Pembroke Pines, FL, USA
RE: Rifling Design - Machining Limitations
RE: Rifling Design - Machining Limitations
Deburr the cut, and the part is gone.
Mike Halloran
Pembroke Pines, FL, USA
RE: Rifling Design - Machining Limitations
RE: Rifling Design - Machining Limitations
The part as envisioned by the OP can be produced at considerable expense, but will not do what the OP wants it to do.
Luckily for the OP, rotation is mostly conserved in flow, so it's possible to get the bulk flow rotating in a larger lumen, and it will continue spinning (faster, I think) as it transits a lumen of the desired size.
Mike Halloran
Pembroke Pines, FL, USA
RE: Rifling Design - Machining Limitations
This is used for injection pressure (which is why the hole is so small), I am looking for an additional swirl for the individual holes (4X) which will create a swirl on its own. This should improve droplet breakup.
The pressures are around 4-6 bar (approx. 58-87 psi) for this application.
I would even conceder an insert for ease of manufacturing, which could be pressed into my assembly.
RE: Rifling Design - Machining Limitations
Now that you've explained what you're trying to accomplish, it seems clear that what you want to happen will not be the result of the machining operation you have in mind.
Your best option is to add tangential velocity to the fluid stream BEFORE it hits this orifice.
RE: Rifling Design - Machining Limitations
I suggest that you spend a couple dollars at the hardware store and buy a trigger-pump spray bottle and examine how it works. You can turn the nozzle cap to go from a solid stream to a cone spray.
My favorite nozzle on my back pack sprayer from Harbor Freight has four holes, and can be adjusted from four solid streams to a single cone pattern. In this design there is no swirl. the fluid enters through a single center hole and passes radially through an adjustable gap and approaches each of the four orifices from the side. Each hole creates a fan spray, which adds-up to a single cone. Having four cone spray orifices next to each other is not a good idea, as droplets will coalesce as they hit each other. After a spray nozzle all droplets should move away from each other to avoid this.