dump valves - how do they work?

There are valves out there which dump massive amounts of air (I've seen these used in spud cannons)

How do these work? (does anyone have a plan or diagram that illustrates how they work?)

I suspect these style of valve would be of great benefit for dumping the pressure out of a vessel, or decompressing a cylinder.

thanks, Des

Reply to
Des Bromilow
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That is their primary use - in air brakes for trains and trucks.

Try Googling for it - all my links are "not found". Wonder if that is part of the great improve-security-by-ignoring-the-Constitution plan.

Fred

Reply to
Fred R

Good explanation here-

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H.

Reply to
Howard Eisenhauer

"How do these work? (does anyone have a plan or diagram that illustrates how they work?)"

is this for a pumpkin cannon by any chance?

Reply to
Wwj2110

No, but the question was recalled by that line of conversation.

I've always been meaning to get my head around the design (and eventual construction) of gas regulators (adjustable - but predictable), and dump valves.

I have a few projects I'd like to get my head around, mostly based in the pressure vessel direction. (Visualise a repeatable steam hammer without the steam, but using compressed air)

Thanks, Des

Reply to
Des Bromilow

I think you're talking about poppet valves, similar to auto intake / exhaust valves in principle. They open a large area quickly. Small ones are used in pump-up type airguns, just a tap on the shaft to overcome the pressure releases the stored air.

Pragmatist

"Politicians are not born, they are excreted." - Some perceptive old greek.

Reply to
pragmatist

You might try google and input something like "turbofan engine bleed valves." Those things dump vast amounts of air.

Garrett Fulton

Reply to
Garrett Fulton

Solenoid operated valves work great if your gas volume is not huge. I've used them in oxy-acet machine guns and repeating cannons for the film industry. The whole trick is to dump the gas fast and these valves do the job. You can gang smaller sizes in parallel for larger volumes.

Ed Angell

Reply to
Ed Angell

--IIRC this is how Bendix made his first fortune. Google on "Bendix air brake" for more info?

Reply to
steamer

Blacksmiths use compressed air, a two-way cylinder, and a control valve to operate power hammers to forge steel. A little googling would let you learn more about it. I have a book on the subject, but have not yet built my own power hammer. I have seen them in use, they seem simple and possible to build at home for a reasonable amount of money, perhaps $500 US.

Richard

Des Bromilow wrote:

Reply to
Richard Ferguson

A friend and I built two, one 35-pound for another friend in Columbus OH and one 60-pound for him. At last report, both work well. Though we splurged and bought all the bits and pieces and paid cutting charges, we built both for under $2000.

If you're a good scrounger, and a halfway capable welder, you can probably build one for close to that figure. The biggest expenses are for the valves and cylinder. Everything else can be scrounged or cobbled together with a little creative fiddling. The biggest concern is making sure the hammer head and anvil are solid enough to ensure transferring as much energy to the work as possible.

Check for Larry Zoeller in Google or sign on to snipped-for-privacy@mailman.qth.net

Subscribing and unsubscribing are easy and there are many knowledgeable blacksmiths on the list.

Someone there will have the URLs at hand.

Reply to
Johan

"Des Bromilow" wrote in message news:...

Regulators are members of a group of valves called "compensating" valves. They are used in enormous numbers to regulate air, various gases, water, and so on. The basic principle involves a rubber diaphragm sandwiched between two housings, or a piston in a short cylinder, with a spring against one side of the piston or diaphragm forcing it one way and air or whatever fluid) pressure working against the other side. On the fluid side a shaft connected to the centre of the diaphragm or piston extends through an inlet hole and actuates a poppet valve, so that as the spring forces the diaphragm one way the poppet opens and allows air to enter from the supply. The delivery side of the regulator is ported to the air side of the diaphragm and as air pressure builds up in the system the pressure begins to push the diaphragm back so that the poppet valve closes when the air pressure balances the spring. Raising or lowering output pressure involves adjusting the spring with a screw or whatever. If the valve has an exhaust function, the poppet may be a tube arrangment, with the shaft having another valve seat on it, so that as the spring forces the diaphragm down this seat closes off the open tube in the poppet (which is vented to atmosphere) and then pushes the poppet down and opens the supply. When the spring pressure is reduced, the diaphragm moves up, shutting off the supply and opening the exhaust. There are other arrangments, but the idea is the same. Diaphragm types are generally more precise and less susceptible to dirt contamination than pistons, but require more guiding mechanisms to keep things aligned. Regulators that use a screw to adjust the spring force on the diaphragm (or piston) are used as regulators. An air-brake foot valve uses pedal linkage to actuate the spring (the spring is often replaced by a rubber snubber to reduce travel). A truck hand valve, used to control trailer brakes only, has a lever that drives a cam to move the spring. A relay valve leaves out the spring, and uses air pressure from a control circuit to control the diaphragm or piston movement. Does this help?

Dan

Reply to
Dan Thomas

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