I've found my external tank to be extremely useful and has turned some of my otherwise useless-in-a-war weapons into potent and functional arms. For those unfamiliar with the parts involved in making your own low pressure air tank I've made a simple write-up.
The numbered list items under each header correlate with the numbered items in this diagram.
Generic Materials list
1. Large size PVC pipe (2" or 3" works best since 4" is very hard to find accessories for)
2. Pipe Couplers
3. Pipe Cap
4. Size adapter bushing
5. Threaded bushing
7. Rigid Tubing
9. Flexible Tubing
10. Check Valve
11. Stem adapter (for bike pump)
12. Tubing Coupler
13. Adapter/Coupler to connect the external tank to the air system of the gun
+ Standing Bike Pump
+ PVC Cement
+ Sealant epoxy or Teflon tape
+ Some donor backpack or other kind of shoulder straps for the tank
Optional: Pressure gauge & non-relieving regulator
A NOTE ON TANK SAFETY
1. With a standing bike pump you're not going to be able to fill the tank any higher than 65psi, so you'll be safe in that regard since the maximum rated pressure of the PVC pipe is 120psi. A handheld pump won't be able to go above 40 psi.
2. If you want to be able to fill the tank with a compressor YOU MUST HAVE a pressure gauge on the tank, a regulator to step down the output pressure level, and you SHOULD NEVER attempt to fill any kind of PVC pipe to it's maximum pressure rating.
3. For this type of tank it's best not to fill beyond 100psi. If you want a higher capacity tank, purchase a purpose-made tank with a higher rating.
4. I have a pressure gauge on my tank so that I can monitor tank capacity and to make sure it doesn't have a leak. It can be added anywhere you want it, but I recommend putting it on the tank side of the check valve so you can watch the gauge while you're filling. It also allows you to monitor how much air volume is expended each time any given gun is fired. Certain guns expend more air than others.
1. Cut 3" PVC Pipe to desired length (anywhere from 12" to 20" depending on how big of a tank you can fit on your back)
2. Use PVC Primer on end of the 3" PVC pipe section and the 3" PVC pipe caps. Pre both with PVC cement and then joint them together using a wood blank and hammer.
3. Use the same process to glue the 3" PVC cap into one pipe coupler
4. And to glue the 3" Reducing Hex Bushing into the other pipe coupler
5. Apply some epoxy sealant on the thread of the threaded 1"-to-1/4"Hex Reduce Bushing and screw it into the 3" Reducing hex bushing.
6. Apply some epoxy sealant on the Instant Tube fitting and screw it into the 1"-to-1/4" Hex Reduce Bushing.
7. Use a box cutter or X-acto knife to cut a short length of Polyethylene tubing and insert it into the Instant tube fitting.
8. Attach the Tee fitting onto the other end of the tubing.
9. Cut two lengths of PVC tubing that will easily reach from the Tee to about your waist when the tank is mounted on your back.
10. Install the Check Valve Coupler onto the end of one of the lengths of tubing. Make sure the arrow points to the tank so that it will allow the pump to fill the tank, but not allow the tank to empty once the pump is disconnected.
11. Install the Tube x Stem adapter onto the pump fitting. Then cut a roughly two foot long length of PVC or polyethylene tubing to connect the Tube x Stem adapter to the Check Valve Coupler.
12. Connect the Instant Tube Coupler to the other line.
13. This line will connect to the gun(s) you plan to use the tank with, and how you accomplish that is highly dependent upon the dimensions of the tubing in the gun itself. Some guns have metric dimension tubing, others have imperial dimension tubing, but with strange inner diameters. The magstrike specifically has 1/4" OD tubing that can plug directly into this type of coupler.
For the magstrike you will need another Tee coupler to go inbetween the pump and the bladder.
9087K81 - Polypropylene Instant Tube Fitting Tee for 1/4" Tube OD = $3.30
9087K61 - Polypropylene Instant Tube Fitting Coupling for 1/4" Tube OD = $2.28
For the hornet you will need
2429K52 - Metric Acetal Multi-Barbed Tube Fitting Tee for 3mm Tube ID = $0.80 Each
2429K12 - Metric Acetal Multi-Barbed Tube Fitting Adapter for 4mm Tube ID X 1/4" NPT Male Pipe = $1.54 Each
51825K43 - Chemical-Resistant Clear PVC Tubing 4 mm ID, 6 mm OD = $0.22 for one foot
50785K92 - Med-Pressure Extruded Brass Thrd Pipe Fitting 1/4" Pipe Size, Hex Coupling, 7/8" Length = $1.73 Each
9087K12 - Polypropylene Instant Tube Fitting Male Straight Adapter for 1/4" Tube OD, 1/4" NPTF = $1.70 ea
And to use either gun without the tank you will simply need a stem plug to put in the fitting where you would normally connect the tank.
51025K254 - Nylon Plug, 1/4" OD = $0.63
14. If you later plan to fill the tank beyond 65psi, or you would like to control the pressure level the gun receives, you will need a non-relieving type regulator to reduce the output pressure to a safe level that won't damage the internals of your gun.
Only a non-relieving type of regulator is meant to be used with a tank supply. Most regulators are designed to be used with compressors and will regulate their output by exhausting the overpressure to the atmosphere. In other words they will constantly "leak" and empty your tank in no time.
A regulator will also in turn will help to conserve the capacity of your tank when the gun is in use since you can set it to only deliver the amount of pressure needed to effective fire the gun.
And finally, here's a ready made set of materials available through Mcmaster that will allow you to make your own tank. Only some of these items are available through any given hardware store. Buying anything except the 3" PVC pipe locally will most definitely end up costing more.
Mcmaster materials list
1. 48925K97 - Std-Wall (Schedule 40) White PVC Unthrd Pipe 3" Pipe Size X 5' Length = $16.57
2. 4880K77 - Std-Wall (Schedule 40) White PVC Pipe Fitting 3" Pipe Size, Coupling, 4-1/4" Length - $3.78 Each (x2)
3. 4880K57 - Std-Wall (Schedule 40) White PVC Pipe Fitting 3" Pipe Size, Cap = $3.28 (x2)
4. 4880K222 - Std-Wall (Schedule 40) White PVC Pipe Fitting 3" Pipe Sz X 1" NPT Female, Reducing Hex Bushing = $3.23 ea
5. 46885K259 - Thk-Wall Black Polypro Threaded Pipe Fitting 1" Male NPT X1/4" Fem NPT, Hex Reduce Bushing,
6. 9087K12 - Polypropylene Instant Tube Fitting Male Straight Adapter for 1/4" Tube OD, 1/4" NPTF = $1.70 ea
7. 5180K75 - Crack-Resistant Polyethylene Tubing 1/8" ID, 1/4" OD, 1/16" Wall Thickness, Black = $0.10 per foot (x10)
8. 9087K81 - Polypropylene Instant Tube Fitting Tee for 1/4" Tube OD = $3.30
9. 5006K35 - Abrasion-Resistant Clear PVC Tubing 1/8" ID, 1/4" OD, 1/16" Wall Thickness = $0.22 per foot (x10)
10. 51055K171 - White Acetal Check Valve for 1/4" Tube OD = $11.74
11. 51055K313 - Gray Acetal Instant Tube Fitting Stem Coupling for 1/4" Tube OD, 5/16" Stem OD = $2.02
12. 9087K61 - Polypropylene Instant Tube Fitting Coupling for 1/4" Tube OD = $2.28
Recommended Optional items for adding a pressure gauge
+ 40565K33 - Compact SS Case Gauge +/- 2% Accuracy 1-1/2" Dial, 1/8" NPT Male Center Back, 0-160 PSI = $6.06
+ 50785K72 - Med-Pressure Extruded Brass Thrd Pipe Fitting 1/4" Pipe Size, Tee = $2.75
+ 50785K61 - Med-Pressure Extruded Brass Thrd Pipe Fitting 1/4" X 1/8" Pipe Size, Male X Female Hex Bushing = $0.73
+ 9087K12 - Polypropylene Instant Tube Fitting Male Straight Adapter for 1/4" Tube OD, 1/4" NPTF = $1.70 ea (x2)
Edited by Aeromech, 23 November 2015 - 02:55 AM.