Puff the magic dragon

[DaveH]

Hello,

What I am looking to do / make, is use something that will control the compressed air (30psi or lower) to give me “puff…….puff…….puff” say every 2-5 seconds (adjustable).

I thought about using a pop off valve of some description. Somehow?

Just to put you in the picture, I have  CNC Sherline mill, using small dia ( .5 – 2mm) and re-cutting the chips is not good – tends to break the cutters. I have also found that an interrupted air flow works better than a continuous one for clearing away the chips.

So any thoughts anyone, - no electrics, ideally should be self contained perhaps with a “twiddle knob” to control the time between puffs.

Any ideas, a little box 30psi in one side and “puff…….puff…….puff” out the other.

 
DaveH 

[arnoldb]

Hi Dave

I know you said no electrics...  But how about a small el-cheapo variable speed hand drill driving a worm and wheel with a cam attached to the worm wheel.  The worm and wheel will be needed to reduce the speed to your requirements.  The cam attached to the worm wheel can drive a simple valve system to pass the air in puffs...

For a pop-off valve you would need some kind of storage reservoir with air inflow restriction to mimic a boiler in action...  Don't know how you would get adjustable timing though 

    Of course, you can also make a pendulum based "clockwork" to operate the valve  - won't be a little box though

 , Arnold

[DaveH]

Arnold,

Thanks mate,   mmmm .... do you have a drawing

Won't need much of a reservoir ..... I think

I thought increasing the spring force using a screw or something might do. Or a needle type valve restricting the fill rate may also work

But there again I'm guessing - not too clued up about pnuematics     (A little self contained 3"x3" box would be nice)
Must be a way.
 
DaveH

[Lew_Merrick_PE]

What I am looking to do / make, is use something that will control the compressed air (30psi or lower) to give me “puff…….puff…….puff” say every 2-5 seconds (adjustable).

I thought about using a pop off valve of some description. Somehow?

Just to put you in the picture, I have  CNC Sherline mill, using small dia ( .5 – 2mm) and re-cutting the chips is not good – tends to break the cutters. I have also found that an interrupted air flow works better than a continuous one for clearing away the chips.

So any thoughts anyone, - no electrics, ideally should be self contained perhaps with a “twiddle knob” to control the time between puffs.

Any ideas, a little box 30psi in one side and “puff…….puff…….puff” out the other.

Dave,

Take a look at http://www.clippard.com/store/display_details.asp?sku=R-331 -- you might have to add a control volume to get your time delay, but it uses air pressure metered slowing in to operate the valve.  You would probably have to cascade valves to get to your signal level, but taking part of the output line to feed the over-power air pilot might work for you.  Everything in one valve.

???

[modeldozer]

What software are you using to control the mill?  Reason for asking is if it is Mach3 it can control a soleniod valve and a brain can be set-up to do the timing, I an using this on my router.  If yuo need could do some pics of the setup.

Abraham

[BiggerHammer]

The only option I can come up with is to use a solenoid valve with a timer. ASCO ( http://www.ascovalve.com/ ) makes some nice ones. A bit pricey but will do the job.
Or you could just borrow that new hit-n-miss air engine cfellows just made. Use it's exhaust to power your chip-clearer. 

[DaveH]

Abraham,
BiggerHammer,

I did look at electrically operated solenoids and timers – just gets a bit expensive. It would nice if it operate just on air alone.

I still think there is a way to do it - although I can't see it

Thanks for your help, .... but don't stop thinking about it

DaveH

[DaveH]

Dave,
Take a look at http://www.clippard.com/store/display_details.asp?sku=R-331 -- you might have to add a control volume to get your time delay, but it uses air pressure metered slowing in to operate the valve.  You would probably have to cascade valves to get to your signal level, but taking part of the output line to feed the over-power air pilot might work for you.  Everything in one valve.

???

Hi Lew, had a look - didn't really understand much of it. 
Can you explain simply how it works
 
DaveH

[djc]

...What I am looking to do / make, is use something that will control the compressed air (30psi or lower) to give me “puff…….puff…….puff” say every 2-5 seconds (adjustable).

How about something on the principle of a peristaltic pump (http://en.wikipedia.org/wiki/Peristaltic_pump)? An air motor with a cam on the end (speed of motor adjusted with standard regulator). The cam opens and closes the tube to provide the puff. Cam might have to be steep in its action on the opening part.

Even simpler would be to have the cam bear on a push valve.

[DaveH]

djc,

Even simpler would be to have the cam bear on a push valve.

....mmmmmm ... thats got me thinking.
Thanks
DaveH

[BillTodd]

Some sort of variation of this device might do it:

http://www.homemodelenginemachinist.com/index.php?topic=14802.msg0#new

Bill

[DaveH]

Bill,

I think I'll wait until it is finished.

Sort of thing I'm looking for but a little more gentle

 

DaveH