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QDV Continued

A place to ask general spud cannon related questions.
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Unread postAuthor: Technician1002 » Tue Dec 14, 2010 5:07 pm

A QDV is a spool valve, but with the outlet configured off the end of the spool unlike most. This provides an avalanche of positive feedback to the spool. This positive feedback is what makes it a Quick Dump Valve.

In most spool valves this positive feedback is undesirable.

Imagine a car that has an accelerator with positive feedback. Touch it and it floors itself until you run out of gas.

For most control valves a simple spring return is nice. Most spool valves do not have feedback related to the pressure they hold.

It is possible to build a conventional spool valve for an air cannon that provided no feedback. It will open only as far and as fast as you move the spool. Building one would be pointless unless you wanted to do some weird flow throttling.

Both the inlet and outlet would be on the sides of the spool and the spool will need more than 2 seals.
Image

A single on off spool valve
Image

In summary, it is a cross between a barrel sealer piston and a spool valve.
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Unread postAuthor: POLAND_SPUD » Wed Dec 15, 2010 4:05 am

so call it an unbalanced spool valve -> USV
or manually actuated unbalanced spool valve MUSV :wink:

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.
I completely agree
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Unread postAuthor: cfb_rolley » Wed Dec 15, 2010 2:59 pm

So, i may have missed the original thread and can't find it and this question may have already been asked, but when will we see cannons with this valve or parts to build it become available?

Forgive me if it's already been asked, and my searching skills are useless.
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Unread postAuthor: saefroch » Wed Dec 15, 2010 3:09 pm

The first two links in Technician1002's signature. :wink:
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Unread postAuthor: jrrdw » Wed Dec 15, 2010 3:10 pm

cfb_rolley wrote:So, i may have missed the original thread and can't find it and this question may have already been asked, but when will we see cannons with this valve or parts to build it become available?

Forgive me if it's already been asked, and my searching skills are useless.


This thread was split from the 2010 Best Shot Contest thread not a showcased cannon thread. Normaly we moderators can catch a threadjacking in progress and turn it around, but the discussion built so fast I split it to it's own thread.
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Unread postAuthor: jackssmirkingrevenge » Wed Dec 15, 2010 3:24 pm

cfb_rolley wrote:So, I may have missed the original thread and can't find it and this question may have already been asked, but when will we see cannons with this valve or parts to build it become available?


The launcher in the video on the first post is this one.
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Unread postAuthor: cfb_rolley » Thu Dec 16, 2010 12:47 am

Ahh thanks for pointing me in the right direction! Well from what I see, it's a cartridge that is a valve and chamber in one, which dumps quickly when operated, so for saying sake, you could call it a quick dump cartridge? I mean technically speaking if there is a patent on it and the description of that patent states that it's a type of quick dump valve, then it can be named as a type quick dump valve. it's just not the kind this forum commonly asscociattes with the term quick dump valve, but I reckon users will probably be able to differentiate between this and other QDVs, especially since it's probably going to be well known about being a pretty fine piece of engineering.
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