Shuttle or Pilot Valves

[markh]

Hey guys. I can't remember where, but someone wrote that John Larson reccomends shuttle and pilot valves now for air hammers. I would like someone to explain to me how this works. I have the kinyon plans but don't know which parts will be replaced by the Shuttle and/or pilot. Thanks

[John Larson]

Mark, the Kinyon plans are noted for their insufficient info on some topics. Ron is a heckofa nice guy and a full time metal smith in the Phoenix area and I respect him quite a bit.

Also, terminology can be varied. So let me try to explain.

The main valve that routes the air into and out of the cylinder is a shuttle valve. A cylindrical piece moves back and forth (shuttles back and forth) to turn a cylinder hose from intake to exhaust mode, and vice-versa, to get the reciprocation needed in the hammer head.

The shuttle is activated by air pressure. Typically, a roller valve triggers this air pressure. The roller is on a short lever and the roller bears against the hammer head when the head is up, and is released when the hammer head is down. This lever's movement pushes a small spring loaded shuttle to pulse the air that activates the bigger shuttle valve. This is analogous to electrical relays where a small current flow is used to switch a big current flow, like with the headlights on a car.

I use Norgren brand valves in my hammers. The main shuttle valve is MN01CHA73A000. It has 3/4" npt ports. The roller valve I use is 03061122 and it has 1/4" npt ports. This roller valve is rugged and has proven durability with all aluminum and steel construction, as compared to lighter duty roller valves with some nonmetalic parts that suffer breakage and that do not flow air fast enough to give snappy performance (in my opinion based on experience). Each of these valves is in the $75-$100 range. Like I said the roller valve is durable. The big shuttle valve will only live for 4-6 years and is susceptible to dirty air. Use an oiler and filter--mandatory--, preferably mounted on or close to the hammer. The filter is obvious. The oiler should be set so that a teaspoon of oil is used every hour or so. The tell tale of adequate oiling is an oily finger when you stick it in the hammer's exhaust pipe, not dripping wet but just moist. Valve failures in the field in my experience almost always stem from inadequate oiling and air line crud. If there is a long hose between the filter and the hammer expect to have water condense out of the air between the filter and the hammer.

[markh]

Thank you Mr. Larson. I appreciate your willingness to share your expertise.

[ptree]

John Larson, The industry names for the valve you call a shuttle valve is a "spool valve"
If the spool vale has two delivery ports, it is a "4 way" way. Also called a 5 port, 4 way directional control valve. The lever operated valve is a 3 way control valve. The lever operated valves just like the 4 way valves can be spool, poppit, diaphragm, or sliding element.

At a hydraulic and pnuematics shop if you ask for a shuttle valve you will most likely get a "Shuttle" valve. This is a valve that has a shuttle (can be a poppit or can be a diaphragm) that has three ports. These have many uses. They can be used as "quick exhaust valves" or to allow the higher of two pressure to be fed to the delivery port.

Not a critism, just trying to help folks find the parts they need. I learned these terms when working in the R & D lab of a major Pnuematics manufacturer about 30 years ago.

[John Larson]

ptree, the terms you use are familiar to you but maybe not the typical reader. What is a "way", a "poppit", etc. ? I'm quite willing to hereafter say "spool valve" instead of "shuttle valve" , and I have certainly used "5-port valve" a lot in my writing and posting. I find the term "way" to be too obscure for my thick skull. How obscure? Letme count the ways. :-)

[ptree]

John, The term 4 way is an industry standard. So is poppit. The intake and exhaust valves in you truck are poppit valves.
I was just trying to make the terms used by the industry clear so folks can get the valves you have found best on the firts try.

For obscure, try "pilot operated, 4 way, 5 port directional control valve" This would be the standard callout for a 5 ported, two position control valve operated in both directions by a pilot air signal:)

The way refers to flow paths. with pilot signal to one end, the valve shifts and there are 2 paths. one supplies pressure and one exhausts. Pilot the other end and there are 2 paths, but opposite the first condition.
sorry to be obscure:)

[eseemann]

John and Ptree, 

 

Please let me start by saying I am a hobby smith that knows less about Pnuematics than my dog. I think I now understand how this is supposed to work and this post has provided a missing bit. 

Tell me if I have this right. The 2 position, 4 way, 5 port valve's exhaust is connected to the "button" (what you use to start the hammer). As long as the exhaust is blocked no air can move. Since no air can move the hammer can't move.

The roller valve is (tell me if I am wrong, I can take it) in a "pressed down" state when the hammer is up top. This shoots air to the 2/4/5 valve to send the ram down. Once the hammer falls the roller valve closes and the 2/4/5 valve sends the ram up. As long as the exhaust is blocked no air can move at all, open the valve blocking the exhaust and the 2/4/5 valve and the roller valve can do their thing. 

Is that about it? 

Ernest