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QDV Continued

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QDV Continued

Unread postAuthor: jagerbond » Tue Dec 14, 2010 2:47 am

Technician1002 wrote:So Jagerbond, how soon are you going to be making QDV valves?


We've made a couple already.. The most notable is in the VARGAS cartridges.
[youtube]http://www.youtube.com/watch?v=dptkE5UZ8sM[/youtube]


Topic starts from Tech's quote, edited and split by jrrdw.
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 14, 2010 3:12 am

Clucking bell, looks great in action! But really it's a piloted piston valve, Tech's referring to a piston with the same diameter as the inner diameter of the seat that is externally actuated.
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Unread postAuthor: jagerbond » Tue Dec 14, 2010 3:27 am

jackssmirkingrevenge wrote:Clucking bell, looks great in action! But really it's a piloted piston valve, Tech's referring to a piston with the same diameter as the inner diameter of the seat that is externally actuated.


so, piloted piston valves aren't quick dump valves?
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 14, 2010 3:30 am

A valve that dumps quickly is a Quick Dump Valve, but on the forum the convention is that QDV is this type as promoted by Tech. Your cartridges would be more like Quick Exhaust Valves due to the use of pilot exhaust for operation.
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Unread postAuthor: jagerbond » Tue Dec 14, 2010 3:41 am

Got it. Makes no sense, but OK.
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 14, 2010 3:55 am

It's just forum convention, in the same way that "hybrid" to most people would be a vehicle with both internal combustion and electric propulsion, but on spudfiles it's assumed to be a pressurised combustion launcher.
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Unread postAuthor: jagerbond » Tue Dec 14, 2010 5:05 am

hmmm, not sure I agree... at least with the hybrid analogy.

Hybrid defines the combination of 2 objects so accurate for both applications... online dictionary excerpt:
b. Something having two kinds of components that produce the same or similar results, such as a vehicle powered by both an electric motor and an internal combustion engine as sources of power for the drive train.

in the spud gun sense it is a combination of Pneumatic cannon (pressurized chamber) and a combustion cannon (combustible fuel with ignition).

Hybrid is accurate for both.

The acronym QDV doesn't accurately describe if there is a pilot involved, so makes no sense IMO. i understand that it is forum convention so I'll understand the reference moving forward.

why not:
POV (pilot operated valve)
NPV (non piloted valve)
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Unread postAuthor: MrCrowley » Tue Dec 14, 2010 5:29 am

in the spud gun sense it is a combination of Pneumatic cannon (pressurized chamber) and a combustion cannon (combustible fuel with ignition).

In that sense, technically, a metered combustion is also a hybrid. MAC (Multiple Atmospheric Combustion) could possibly be a better acronym but I'm really just talking out of my a$$ here.

I believe the QDV is actually a commercial valve and Tech was just the first to make it suitable for spudguns. In fact, Quick Dump Valve may actually be the original name of the commercial valves. I think MythBusters use them when they have those huge red propane tank looking chambers which seem to have no valve.

Anyway, this discussion is similar to that of the hybrid one we had a little while ago. There's no point changing the name as everyone knows what it already means and changing the name would just create more confusion. While we're nitpicking, some of Tech's valves are designed to open slowly, does that mean we have to call them a Slow Dump Valve?

why not:
POV (pilot operated valve)
NPV (non piloted valve)

That could cause confusion with hammer valves and the like.

At the moment everyone knows a QEV is generally a commercially bought piston valve (unless you're French), a piston valve is generally homemade, a QDV is a valve that operates with the same principles as Tech's design, a hybrid is a multiple atmosphere combustion and an advanced combustion (while not being particularly advanced) is a metered combustion with perhaps a fan.
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 14, 2010 6:06 am

Mike, I agree with you in principle, it's not the best nomeclature.

Alas, by now the name's kinda stuck - and judging by the amount of people here who still insist on calling their launchers "snipers", I doubt it's going to change any time soon :roll:

MrCrowley wrote:Slow Dump Valve


That sounds disgusting :)
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Unread postAuthor: jagerbond » Tue Dec 14, 2010 6:12 am

My report card stated once "resists conformity". :D
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Unread postAuthor: Technician1002 » Tue Dec 14, 2010 6:19 am

In reference to the naming convention on the Quick dump valve, in research I found the valve exists for liquids. It is designed to quickly dump a chemical or rinse tank in processing. It is often operated mechanically or with a small coupled air cylinder.

I kept the name instead of creating a new name for an air part.

Here is a manufacture of them;
http://www.imtecacculine.com/prod_acc_qdr_dump.html

The quick dump valve used in cars as a pressure relief valve on a turbocharger is not the same thing by any stretch of the imagination. It is a large pop off valve.

The Mythbuster air cannon valve is a piston valve. You can find the valve and red tanks from the original manufacture. They contain a narrow ratio piston valve with a short piston, much like a QEV. The piston is less than half as long as it's diameter. The piston is hockey puck shape. You can see that if you find the service manual online for that cannon. It is a PDF. My two hints Hurricane and Martin. Don't bother them. They don't like questions from hobbyists. If you have a cement plant, they will talk to you. They are industrial equipment.

I'll search the valve and post it here.. here is is..
Image

A slow dump valve is often called a dump valve and is used for emptying the waste water tanks on an RV.. and yes it is disgusting.
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Last edited by Technician1002 on Tue Dec 14, 2010 2:03 pm, edited 4 times in total.
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Unread postAuthor: jagerbond » Tue Dec 14, 2010 6:24 am

Speaking of alter acronyms, have you seen the Taser HEMI?

http://www.coolthings.com/new-hemi-projectile-delivers-taser-shocks-using-a-grenade-launcher/

Got to witness it at the JNLWD show this year.
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Unread postAuthor: velocity3x » Tue Dec 14, 2010 11:15 am

jackssmirkingrevenge wrote:It's just forum convention.


I agree. What's in a name anyway? After all, it's actual (verifiable) performance that counts.....not the acronym by which a valve is known!
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Unread postAuthor: Technician1002 » Tue Dec 14, 2010 1:54 pm

Pretty much the definition I have for a QDV is a spool valve with the valve seat and the OD are the same size for a 1:1 seat to OD ratio. It is sealed at both ends by o rings or other suitable seals so chamber pressure does not change the force on the valve when it is closed. Normal operation when closed is with no pressure in the pilot or barrel. When opened, the chamber pressure forces it open. To open it, a mechanical or other force is required to unseat the valve.

Variations on the trigger can include a pull rope, a mechanical linkage, or vacuum in the pilot or pressure in the barrel to initiate piston motion. Once in motion and the front seal opens, the chamber pressure then finishes opening it.
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Unread postAuthor: Hotwired » Tue Dec 14, 2010 2:39 pm

I always think of that valve as a spool valve to be honest and still do.

A "quick dump valve" is a phrase I've seen used to describe a lot of fast acting piston type valves for industrial use.

I've never been comfortable saying that your valve is THE quick dump valve because that doesn't make much sense when compared to what it physically is and what you're going to get if you search for a quick dump valve.

Doesn't mean I don't recognise that others say it but I don't like saying it.

On that note, it says something that many of the top listings in a search for a "quick dump valve" are the ones that link to your cannons.

If it wasn't for you naming it as a Quick Dump Valve it would not be called that I'm entirely sure. Parsoneaults pitching machine and then the Avalauncher have earlier claims to the valve principles in a launcher.
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