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Really Compact APH

Posted: Thu Mar 03, 2011 11:28 pm
by strato_2r5
Hi guys, I'm new to the homemade world and I'm thinking of making an APH. The ones on this site are really bulky and I'm thinking of making this Shotblast sized. Any tips for a trigger? And is the Pressure chamber big enough? Here's my design for it.

Re: Really Compact APH

Posted: Fri Mar 04, 2011 12:19 am
by soakernerd
That would work....sort of. You really need a large PC for good performance
The real problem in most homemades isn't their size, but their ergonomics. It is very hard to create a good trigger for a APH.
I am currently working on a similar project:The valve from that design does not work. I will be using something like a PVAT, but housed in the Tee like the original design.

Re: Really Compact APH

Posted: Fri Mar 04, 2011 12:31 am
by martianshark
That would not work - there's no pressure chamber. As it is, it might squirt out a little water for a moment... but it really isn't going to do anything without a PC.

Re: Really Compact APH

Posted: Fri Mar 04, 2011 12:31 am
by cantab
Not going to work very well. Remember in the pressure chamber the air always sits above the water. As soon as you tilt the blaster upwards - which you have to for best range - the air is right against the firing valve, and when you shoot you'll just shoot air.

Re: Really Compact APH

Posted: Fri Mar 04, 2011 6:04 am
by strato_2r5
cantab wrote:Not going to work very well. Remember in the pressure chamber the air always sits above the water. As soon as you tilt the blaster upwards - which you have to for best range - the air is right against the firing valve, and when you shoot you'll just shoot air.
Would adding two more bends in the pressure chamber fix that problem? The top pipe would bend down towards the pump then forwards, creating an S-shape. Would that solve that air problem?

Re: Really Compact APH

Posted: Fri Mar 04, 2011 6:25 am
by mysterio
Soakernerd, you didnt even reference my thread?

Back on topic, it would somewhatly, not really. it would only fire flat, and if you angled it, the air would bubble out like in the original design. Slower, but it would.

Re: Really Compact APH

Posted: Fri Mar 04, 2011 9:00 pm
by soakernerd
oops. Couldn't remember who posted that. Sorry.
Credit to mysterio for suggesting the PVAT as a firing mechanism.

Re: Really Compact APH

Posted: Fri Mar 04, 2011 11:44 pm
by strato_2r5
mysterio wrote:Soakernerd, you didnt even reference my thread?

Back on topic, it would somewhatly, not really. it would only fire flat, and if you angled it, the air would bubble out like in the original design. Slower, but it would.
So how could I fix that?

Re: Really Compact APH

Posted: Sat Mar 05, 2011 12:19 am
by soakernerd
Add a pressure chamber. A vertical length of pipe is really needed for it to perform well.

Re: Really Compact APH

Posted: Sat Mar 05, 2011 12:31 am
by cantab
Attached is a possible layout for the pressure chamber and nozzle section. This is probably the most compact feasible layout, however it will sacrifice performance compared to the more usual vertical design.

The pressure chamber - the uppermost pipe - should be as large a diameter as you consider practical. The barrel - the lower pipe - should be large diameter for performance, but small in volume to reduce "dead space" (water that cannot be fired). So its diameter is a compromise. You could shorten it, having the pressure chamber protrude further forward than the nozzle.

Re: Really Compact APH

Posted: Sat Mar 05, 2011 1:43 am
by strato_2r5
Thank you cantab. I'll try that once I get the materials. Any tips for a trigger mechanism?

Re: Really Compact APH

Posted: Sat Mar 05, 2011 7:12 pm
by mysterio
Build the PVAT that soakernerd mentioned in the thread earlier. It should work out okay, as long as its a tee.

Re: Really Compact APH

Posted: Sat Mar 05, 2011 9:58 pm
by C-A_99
If you really need the compact design, I'd have to seriously recommend making a CPH or APH pressurized reservoir design instead. Even if you have a backpack, an APH can still get large quite easily as a lot of volume is needed to store the air.

A PRH (pressurized res homemade) would be easier to build and may not perform as well as a standard APH. For a CPH, you can nest the bladder into the reservoir and keep it fairly small. No one has actually done it before, but it doesn't seem to be difficult to do if your reservoir design allows for it.

Edit: soakernerd's correct on that, my bad.

Re: Really Compact APH

Posted: Sat Mar 05, 2011 10:16 pm
by soakernerd
I think JLspacemarine's CPH had and internal res/PC.

Re: Really Compact APH

Posted: Sun Mar 06, 2011 8:03 am
by strato_2r5
How do I stop my resovoir from caving in when pumping? And mysterio, would you please draw a design showing how to attach the PVAT?