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DFTV Revisited and 3D Printing Pistons

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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DFTV Revisited and 3D Printing Pistons

Unread postAuthor: akb » Fri May 17, 2019 10:48 am

Hi Folks. Been away a very long time. Still making Antenna Launchers, but haven't been on the forum here since 2010, at least in terms of posting.

I'm working on a new DFTV (Darn Fast Turbo Valve) design with some 3D printed parts. I see some folks have done printed pistons. I need to do more reading and some experimenting to see how that works out. Any thoughts on materials, infill, etc?

My goal here is to make a 1.25 inch diameter flow DFTV in a 1.5 inch tee for a 17 inch overall length tennis ball launcher. I like compact solutions that can launch up to 200 feet high and fit into an 18 inch tool case. I've done this with a piston valve from LaunchPotatoes but that requires an expensive (and bulky) QEV trigger, and those piston valves are no longer available. They also don't fill using a small compressor, they need a strong pressure pulse to get an adequate seal. I'm thinking about triggering this Turbo valve with mechanical means which will avoid some problems with o-ring damage from a port into the pilot volume. The o-ring seals are more positive and work with small compressors. It is easy to reset the valve and close the piston by pushing on the turbo disc through the bottom of the valve as I did in the DFTV19 linked below.

Image

Cutaway of new DFTV design

References

DFTV Development - spudtech_archive/viewtopic.php?f=5&t=2851&hilit=dftv
DFTV19 Antenna Launcher - http://www.antennalaunchers.com/dftv19/
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Last edited by akb on Fri May 24, 2019 8:51 am, edited 3 times in total.
-- akb - the Antenna Launcher guy - inventor of the DFTV

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Re: DFTV Revisited and 3D Printing

Unread postAuthor: jackssmirkingrevenge » Sat May 18, 2019 6:35 am

There's a blast from the past :D

Do you still have your G0516 Lathe/Mill? I think if you have the constraint of compactness, higher pressure is the way to go.

The proliferation of cheap and effective airgun pumps makes it accessible but naturally PVC construction is not an option.

Here's a design for a mechanically locked spool valve using a paintball marker trigger group for firing:

Image
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hectmarr wrote:You have to make many weapons, because this field is long and short life
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Re: DFTV Revisited and 3D Printing Pistons

Unread postAuthor: akb » Sat May 18, 2019 9:57 am

Must be a time warp. :)

Yes! You have an excellent memory. Going to use it today (G0516). Have a couple Antenna Launchers to finish up.

Great design, nice drawing. What CAD tool do you use?

Reminds me of the time I did paintball. Another blast from the far past.

I wonder at what pressure the tennis balls might deform.. Of course paintballs are pretty fragile and they seem to do fine. It would be very interesting to go to regulated near CO2 pressure levels, but what a job making all those parts from metal in tennis ball sizes... One of these days I will have to try that. Has anyone done 500 psi with tennis balls? I've stopped at 150, about the limit of plastic. Generally we use about 40-50 psi. With better valves like the DFTV we can use even lower pressure.

I do have some HPA gear. My SCBA tank might not last long with tennis ball launching.

I have these wonderful little CNC robots that will make parts from plastic waiting for my commands... The CNC Mill/Lathe projects are still in the future..

Thanks,
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Last edited by akb on Fri May 24, 2019 8:52 am, edited 1 time in total.
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Re: DFTV Revisited and 3D Printing Pistons

Unread postAuthor: jackssmirkingrevenge » Mon May 20, 2019 4:04 am

akb wrote:Great design, nice drawing. What CAD tool do you use?


MS Paint :oops:

I wonder at what pressure the tennis balls might deform.. Of course paintballs are pretty fragile and they seem to do fine. It would be very interesting to go to regulated near CO2 pressure levels, but what a job making all those parts from metal in tennis ball sizes... One of these days I will have to try that. Has anyone done 500 psi with tennis balls? I've stopped at 150, about the limit of plastic. Generally we use about 40-50 psi. With better valves like the DFTV we can use even lower pressure


It's true that increasing the pressure makes construction a lot more involved and expensive, and for your purposes it's probably not necessary. I'm not aware of any 150 psi + tennis ball cannons, but here's a GGDT exercise:

Image

With a modestly sized chamber (under 2 cubic inches) at 850 psi and a valve with 0.5" porting, we get just over 200 feet per second with a 9 inch long barrel. Peak barrel pressure is around 65 psi so I don't think deformation would be a particular issue.
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Re: DFTV Revisited and 3D Printing Pistons

Unread postAuthor: akb » Thu May 23, 2019 8:04 pm

Image

Having some trouble with images, fixed them again. Here's a Turbo Valve 17 inch Antenna Launcher with Mechanical Trigger and Mini Coaxial Launch Line Reel rendering

I had no idea that MS Paint could look that good. Very good performance on GGDT as well. I don't know if I have GGDT anymore, though obviously I have CALM but GGDT has more features. I see they are working to get GGDT supported here which would be excellent.

I've made some progress on the Turbo Valve Antenna Launcher's CAD. This render doesn't have the cutaway, but the valve and elbow are fully detailed inside. This is done in OpenSCAD which generates STL files for 3D printing or CNC machining.
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