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Air Max 10

How I turn this $16 lump into a fun primary.

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#1 Majestic

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Posted 15 April 2014 - 01:42 AM

When this blaster was released last year I took one look at it and knew this was how I was going to spend the entire winter. Figuring out how to make this thing perform better, and after months of work the following is what I came up with.

Lets turn this,

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Into this,

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You will need(with part numbers)

.53 PETG - McMaster 2044T43
5/8 in OD Clear PVC - McMaster 53945K15
3/4 in OD Clear PVC - McMaster 53945K16
1/8 in Polycarbonate Sheet - McMaster 8574K26
Miniature Air Pressure Gauge - Mcmaster 38105K51
8mm Vinyl Tubing - McMaster 5233K117
3/4 in OD Neoprene Washer - Bought at my local Ace
Ace Repair Kit - 45503 or 45478
8-32 Nylon nuts & bolts - Bought at my local Ace
1/2 in Wooden Dowel Rod - Also from the local Ace
8mm SMC Residual Pressure Relief Valve - On Amazon
Bell Airstrike Dual Action Frame Pump - Also on Amazon

Dis-assembly

1) Remove the 2 screws from the pump handle, the 12 screws in the body, and pry off the 2 black accent pieces.

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2) Clam shell the blaster and remove the trigger, pump, and tank assembly. Be careful not to lose the air seal or its spring.

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3) Remove and discard the air hose, but retain the nuts.

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4) Remove the turret assembly and the trigger actuator by removing one screw. Separate the rotation mechanism from the turret and set it aside.

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Turret Mods

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1) Mark the air seal and cut out a hole the size of the PETG, I use a scrap of tubing and a drum sanding mandrel to keep it centered. Cut out the air restrictors.

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2) Make marks 3/8in from the tip and 1in from the base of the barrels, and then cut. Throw away the middle bit.

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3) If you look closely you will see that there are 3 different I.D.s in the barrels, this is what will hold our .53 PETG barrels in place.

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4) Flatten any rough or uneven edges by sanding on a flat surface. If you will be painting your turret, now is the best time to do that.

5) Cut the PETG into 7in segments. To keep them from deforming and identical, I insert a length of 1/2in dowel rod marked to the length I want to cut and run a pipe cutter around it. Then carefully ream and deburr the ends.

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6) Make tightening rings on the PETG. I used a piece of thin spring that I bent into a ring with an ID of .52 and a jig made with a 1/2in dowel rod. Slip the ring over the PETG >1in from the end and slip the tube over the rod. Pass a blow torch over the assembly, rotating the tube so that it gets heated evenly. Allow the PETG to cool and move the ring to >1/2in from the end and repeat the heating process.

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This process takes quite a bit of finesse to do well. The PETG deforms and turns to mush very quickly. Practice on scraps until you get it right. The rings should be lose enough that it is easy to pass a dart through, but tight enough that the dart doesnt fall out when the barrel is shaken or turned upside down.

The method I use is very similar to and based heavily on MIG's write-up. Thanks MIG!


7) Carefully pop out the air seals with a large screw driver. Wrap a single layer of Electrical tape around each barrel above the tightening rings and push the tube through the turret far enough that the seals can still fit in their slots. Remove the excess tape as you seat each barrel. Fit the smaller turret piece over the end of the barrels, a friction fit is plenty. Fill the gap between the barrels and the base of the turret with hot glue. Use the low setting if your glue gun has one so as not to deform the PETG. Before the glue cools replace the air seals and press them in with the handle of a screwdriver. Once the glue cools trim the excess with a hobby knife.

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Improved Indexing

1) Make 2 disks out of 1/8in polycarbonate with an OD of 3/8in and an ID of 11/64in. Cut notches in the disks just large enough to slip over the spring perch on the rotation mechanism.

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2) Lubricate all of the teeth and set aside.

Improved Air Seal

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1) Cut 1/8 in rings from both in OD clear PVC and 5/8 in OD clear PVC.

2) Remove the rubber gasket from the seal and sand the rim flush. Take care not to damage the O-ring inside the seal. Wash and dry the 2 rings, seal and the in neoprene washer. Nest the pieces and epoxy them together. I put a little grease on the internal O-ring to ensure that no epoxy cures on it.

3) To accommodate the larger seal remove the bit of shell from both sides marked with a sharpie.

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4) Take the conical spring out of the Ace Repair Kit #45503, this will replace the weak stock spring. Slip it over our beefy new air seal, and the blaster can now handle the increased amount of air flowing out of the tank.


Pump Replacement

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1) Using a rotary tool, remove the end cap from the stock pump and set aside.

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2) Unscrew the head from the Bell pump and throw it away. Plug the end of the pump with tape and remove the threads with a rotary tool. Clean the area with soap and water then remove the tape. Fit the stock end cap over the pump and epoxy it into place.

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3) Remove the nylon nuts from the pink tube and set aside. Dispose of the tube, it is garbage.
4) Mark the shell 7 in from the end of the pump support and cut off the whole thing. DO NOT damage the screw at the bottom of the turret. Cut 1 in off the end of the pump support. Cut two 4 in by in pieces from the scraps. Sand all of the cut edges smooth. If you will be painting your blaster, now is a good time to sand the entire thing.

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5) Tack the two thin pieces together with hot glue and tack that into one side of the shell. Epoxy putty the piece into place, then repeat with the other side of the shell to get a smooth line, then remove the hot glue.

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6) Attach the 1 in pieces to the end of the pump support using the same method. Once attached remove enough material from the end of the shell to accommodate the new pump.
7) Drill two holes in each side of the pump support, and mark the pump cylinder where it touches the holes. Epoxy nuts to each mark. I used 8-32 nylon nuts and blots cut to 3/16 in. Nylon hardware is great because it is easy to cut, sand and is paint-able. You will have to sand the nuts until they are slim enough to fit in between the pump cylinder and shell.
8) Cut the pump handle down so that it will clear the bottom of the shell.

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Tank Expansion

1) Separate the tank and blast button. Remove the O-ring and discard.
2) Sand the walls of the tank as well as the contact area between the blast button and tank. Be very careful not to get debris inside either piece.
3) Cut two 1 in lengths of OD clear PVC, two in length of 5/8 OD clear PVC, and two 5/8 in disks from 1/8 in polycarbonate sheet.

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4) Carve a U-shape into one end of each 5/8 OD clear PVC piece so that they conform to the shape of the tank.
5) Drill a 3/8 in hole in the center of one of the OD clear PVC pieces. Sand all of the surfaces to be epoxied, wash them all with soap and hot water. When they have dried, epoxy them together.
6) With a scrap of 5/8 tubing, mark the places where the expansion chambers will be mounted. Drill out the center. So that the insides of the tank are not damaged, use a sanding drum to thin the walls (It is 1/16 in thick). To keep debris out of the tank, hold it upside down and finish cutting the holes with a hobby knife.
7) Epoxy the expansion chambers and blast button into place.

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8) The holes must be drilled in the 2/3s of the tank opposite the blast button or the valve on the inside of the tank will not function. Not below the red line in the picture below.

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9) Carve out enough of the shell to accommodate the new tank.

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The method I used is heavily based on iamthecat's write-up. Thank you MR. Cat!

Residual Pressure Relief Valve

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The purpose of the Residual Pressure Relief Valve is to release all of the pressurized air between the pump and the check valve on the blast button (Blue section). Doing so will greatly increase the efficiency of the blaster because the air in the prime chamber(Green section) no longer has to compete with the air in the tube to exit the system through the port in the blast button(labeled B). The competing pressure causes the valve inside of the tank(labeled V) to close slightly slower, allowing some of the air in the tank (yellow section) to escape out the rear of the tank causing diminished ranges.

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1) Cut two lengths of 8mm tubing one 6 in and one 2 in.
2) Use a torch to lightly heat one end of each tube and press it through the end of the stock nylon nuts. Attach the short length of tubing to the pump and the longer segment to the blast button. I used a 7/16 socket to ensure a good tight seal.
3) Cut off the mounting ring from the bottom of the RPRV (It is the shaded part in the picture above). Be sure to close the ends with tape to keep out debris.
4) Mark where the RPRV will go in the shell of the blaster, drill a small hole first then widen to fit. Make sure that your placement leaves room for the trigger actuator rod to move freely and that there is room for the tubing on both ends of the RPRV. Hot glue it in to place.
5) In order to accommodate the larger tubing, the supports must be removed from the black trim piece.

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Rear Loading

1) To find the proper placement for the hole in the shell put the indexing assembly, turret, and shell together. Turn the blaster to face you and find the barrel at top-dead-center and count two barrels away from that. Count clockwise if you wish to load darts with your left hand and counter-clockwise for the right hand. Drop a sharpie down the barrel to mark where the hole should be drilled. Take the blaster apart and drill out the hole to in, taking care to keep it centered on the mark.
2) Drill a hole in the outside of the shell in line with the interior hole and widen it to fit your index finger. Be sure to clear any obstructions on the inside of the shell.
3) Cut a piece of clear PVC large enough to fill the space between the holes in the shell. Cut one end of the segment at a 30* angle and cut a T into the tube at the opposite end. Use a torch to carefully mold the wings created by the T to fit the cavity in the shell.

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4) Hot glue the new dart ramp into place making sure that the trigger rod can still move freely

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I found the corpse gray color of the plastic uninspiring, so I painted mine. I used VHT White vinyl dye as a primer(it sucks don't use it), and white spray paint base coat(thanks for the tip Duke Wintermaul). The accents are Citadel Abaddon Black and Genestealer Purple, the dry brushing was done with Testors Metallic Silver. A few coats of matte clear coat finish the job. For fun I also and threw in some pink LED's actuated by a momentary switch at the end of the trigger pull.

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Using the blaster took a bit of getting used to as you have to press the RPRV before the trigger is pulled, but I placed mine so that it can be easily reached with my index finger in the same motion.

As for the ranges, I live in a pretty congested neighborhood in Chicago where open spaces without people stumbling around or massive wind all the time are pretty much non-existent. But from my back door to the wall where the ally behind my building dead ends is about 125 ft. #6 slugs fired at an angle hit the wall about 5 ft up and bounce backwards another 10 ft. Level shots are hitting in the 95-105 ft range with the same slugs. Both are at 5 pumps and 80 psi.
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#2 shmmee

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Posted 15 April 2014 - 08:21 AM

Wow. That's one of the best write-ups I've seen in a long time. Very impressive. There is one point I'm confused about though - the "Residual Pressure Relief Valve". Does it replace the blast button? It's the first time I've ever seen one and I'm a little unsure about how it works or why it was used. Any chance you could do a range test comparison with and without the residual pressure relief valve? You might have to clamp the barrel down for accurate data. I'd like to see a quantitative comparison to see how much it actually contributes to the system. I love playing with back pressure tanks but they can be finicky. My experience is that the least amount of dead space between the blast button and tank the better. Adding an extra component and more dead space might be hurting rather than helping. But if it functionally removes dead space of the tubing between the pump and blast button so the blast button can focus on venting the tank stem - that could be a component I need to add to my parts bin.

Using the sanding drum mandril is a new centering method I've never seen before. Props.

Could you include a completed internals pic? I'd like an overview of how it all fits together.

Edited by shmmee, 15 April 2014 - 08:31 AM.

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#3 Duke Wintermaul

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Posted 15 April 2014 - 10:01 AM

Wunderbar! I've been working on a writeup for the Air Max 6, basically because nobody has done one in the new Extreme line yet. This puts what ever I might have squirted out to shame.

I was reading through, and kept thinking "Damn, so much work and effort for that little air tank" and then you expanded it. Artfully done, it felt like reading a thriller book.

Do not remember telling you to avoid white vinyl dye, but you are correct it is absolute shite. A dollar can of white paint will work seven times better at a seventh of the price. But, I guess I already told you that...

The only thing this writeup is missing is some chronograph data. I, too, have an overhauled AM10 and would really like to see how your tank expansion, and other fixes, stack up in muzzle velocity.
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#4 Aeromech

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Posted 15 April 2014 - 10:22 AM

I've been working on a writeup for the Air Max 6, basically because nobody has done one in the new Extreme line yet. This puts what ever I might have squirted out to shame.


That makes two of us. Incredible quality writeup. And nice cosmetics if I do say so myself.
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#5 azrael

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Posted 15 April 2014 - 12:54 PM

Very nice work, some good tips in there for sure. I too, would like to see some chrony data.

Why was it necessary to remove the Bell pump's cap? I use those too, pretty cheap from Walmart. However, I just use old bike tubing's connector to connect tubing. Works great as a check valve, too.

Finally, the inspiration I need to mod my Air Max 10.
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#6 ShaNayNay

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Posted 15 April 2014 - 08:03 PM

Excellent writeup. Glad to see you found an alternative to boiling the turret. I recall that being the original norm, and that risked ruining the entire turret from deformation.

Edited by ShaNayNay, 15 April 2014 - 08:04 PM.

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#7 Sam-underscore

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Posted 15 April 2014 - 08:50 PM

Why was it necessary to remove the Bell pump's cap? I use those too, pretty cheap from Walmart. However, I just use old bike tubing's connector to connect tubing. Works great as a check valve, too

Sorry for the a bit off topic question, but how do you like that pump? I thought about buying one but it had many negative reviews on amazon.
Does it push around a good bit of air for its size?

Edited by Sam-underscore, 15 April 2014 - 08:51 PM.

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#8 Majestic

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Posted 18 April 2014 - 04:17 AM

Thanks for the feedback, this entire project has been a lot of fun and I’m glad ya’ll enjoyed the results.

@Shmmee, the RPRV does not replace the blast button. It goes in line between the pump and the check valve. The stock pump has a notched head that allows the pressure in the tube to be released on the back stroke of the pump. Similar to a nitefinder plunger and is discussed here.
A dual action pump cannot function that way as it is busy pumping on both strokes creating the need to vent the pressurized air in the tube in some novel way. Without the activating the RPRV the air coming out of the tank towards the barrel is drastically reduced and the darts just sort of spill out the end of the blaster.
There are of course other ways to solve this problem like using an “unloading check valve” which closes as pressure increases and vents to the atmosphere when pressure is constant. I have one but have yet to experiment with it. I’ll post my findings when I have them but the RPRV system works flawlessly.

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As you can see the amount of space added between the pump and blast button is negligible and there has been no change in the distance between the BB and the tank.

@Duke, D a n k e schoen. I would love to point this thing at a chronograph and get some hard numbers to tweak this thing with, but alas I don’t have one.

@Azrael, I replaced the Bell cap with the stock one to keep the blaster as clean and simple as possible. I did not want to make any more cuts in the inside or outside of the shell than were absolutely necessary. During the prototyping stages I definitely used the Presta valve head and a salad of tubes and hose clamps, but I wanted the finished design to look, feel, and function like each piece was meant to be there.

@ShaNayNay, boiling the turret and trying to pry off the air seals will definitely deform them, compromising the work done to increase the size and spring rate of the seal on the end of the tank. Once you bore them out large enough for rear loading a large flathead screwdriver can pop them out very nicely.

@Sam, the Bell works better in this application than the Peak DX 2(which is not a bad pump at all) that I tried first. The plunger tube is diameter is small enough that it easy to develop the high pressures this tank loves. As you can see in the pictures I found them on clearance at my local Target for $6.08, and they all came home with me. Later this summer I am going on a 250mi bike trek across Missouri and one of these will come with me. So yeah, I like it just fine.

Edited by Majistic, 18 April 2014 - 05:12 AM.

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#9 shmmee

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Posted 18 April 2014 - 08:39 AM

Ok that makes sense. My go-to valve is the clippard mavo-3. It replaces the blast button and isolates pump tubing while venting the firing tank, but clippard does mean awful nasty things to you at checkout with shipping and handling being a separate $10 charge. The RPRV looks like a much cleaner and cheaper option for a singe shot set up. Good find! I love back pressure tanks. I'm going to have to pick up a couple of RPRV's up. Thanks for including shopping links to the parts.

I think I've got the same bell bike pump on one of my blasters. It's a decent pump. The handle could feel a little more solid, but it is still sufficient for furious mid battle pumping.

Edited by shmmee, 18 April 2014 - 08:42 AM.

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#10 Zorns Lemma

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Posted 18 April 2014 - 09:51 PM

So if I am to understand correctly, the point of the RPRV is to act as an additional pilot valve to vent the valve in the tank faster, so it will release more of the air in the tank at once?
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#11 azrael

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Posted 18 April 2014 - 10:17 PM

I've never had a problem with back pressure tanks and a dual action bike pump. I don't think so, at least.

Edited by azrael, 18 April 2014 - 10:18 PM.

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#12 Majestic

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Posted 19 April 2014 - 05:14 PM

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@ Zorns, I know this is an under discussed topic so I shall try my best to explain it again.

The red icons are all of the valves in the system that serve either to create different chambers within that system(the tank valve and the check valve), or to release pressurized air in the system to the atmosphere. The chambers created by these valves are blue, green, and yellow above.

When the system is under load all of the pressure in the three chambers is equal. Activating the BB vents the green air to the atmosphere causing a chain reaction within the system. With the green air now gone the pressure in the yellow and blue sections rush towards that section in an attempt to achieve equilibrium (science). When the yellow air moves toward the green section it brings the tank valve with it sealing the port at the back of the tank and opening the port at the front, allowing the air to escape through the barrel. Simultaneously the blue air also rushes to fill the green section and since the check valve will always allow air to flow in that direction. The flow of blue air into the green section exerts force on the tank valve when it attempts to close holding it open for a fraction of a second allowing the yellow air and blue air to mix as they try to escape the green section through the BB(see what I did there). Eventually the tank valve does close but a lot of the mass within the tank has already escaped through the rear of the tank, which is undesirable if our goal is to fling foam hard and fast.

The solution is to vent the blue air first. Since the CV will never let air move from green to blue, activation of the RPRV vents the blue air only and allows the system to function normally.

All of this only matters if you replace the stock pump(which vents the blue air on each pump) with a more awesome one like I did.

I hope my explanation helps as I don't think I can describe it any better. My only other suggestion would be to spend some time experimenting with back-pressure tanks and see what you discover, you'll have fun.
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#13 Zorns Lemma

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Posted 19 April 2014 - 08:47 PM

Makes sense. Thanks for the great explanation.

My experience with directional control valves has always had the check valve close to the pressure intake, so I never ran into that issue where the blue section is meaningful volume requiring another dump valve.

How does the RPRV work? From searching around it seems that you have to manually press a button for it to vent to atmosphere. Is there a way to perhaps trigger the venting automatically?
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#14 Majestic

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Posted 20 April 2014 - 04:56 AM

That is exactly how it works.

During testing I took the guts out, attached a single barrel to the tank and attached the pump with varying lengths of tubing, going as little as 1.5in and it still noticeably affected the air output of the tank. When I pressurized the system and removed the pump section before firing it shot fricken lasers. So, I then set out to discover ways to approximate that result.

The SMC RPRV is simply a push-to-connect-to-push-to-connect fitting with a dump valve covered with a big red button and some shiny brass. I used it because it solves the problem of the "blue air", is inexpensive, fits well inside the shell and is mechanically simple.

There are of course multiple ways of solving the problem. Perhaps installing another blast button in the blue section and modifying the trigger actuator to activate it just before the stock one.

Control Devices makes a unit called an "Unloading Check Valve" which it designed to extend the life of an air compressor motor by venting the air immediately down stream of the motor when ever the motor is not pumping so that it does not have to contend with the resistance caused by that air while it is accelerating to working speed. I have one of these but have not done any testing with it and there are many issues surrounding its usage in this application. Once I have spent some time fiddling with it I will post my findings.

One could also use a Normally Open or Fully Ported 3-way valve to solve the problem. Clippard makes some neat stuff, including low voltage and amperage electronic models that would be a blast to tinker with, and they are over $50 shipped.

Im sure there are dozens of clever ways to solve the puzzle, and I would love to hear them/see the results they produce.

I genuinely appreciate the interest and feedback ya'll have given to this little project of mine.
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