Looks like a valve build might be able to happen this weekend! We are pumped to get the Ion firing more effectively. As long as I can get to work on some design we should be able to turn it out this coming weekend!
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With our last build resulting in a gun that could be muzzle loaded to fire single shots, Brian was confident that we could attain semi-auto firing over the course of the coming weekend. The main problems and parts that needed to be addressed to get to that point were correcting the cycling issues in the bolt, rigging a sort of makeshift trigger system to fire the gun, and feeding paintballs into the system.
The issue that had to be solved first was the issue of cycling. After our second build, we found that the bolt was not being forced forward by the firing pressure when the control pressure was released. To fire the gun, we had to assist the bolt by pushing on the back of it with something. We expected that the primary cause of this problematic friction was the surface finish of our internal parts. This appeared to be an easy fix after some fine grit sanding on the lathe. Another way that we helped the movement of the bolt was by deepening the o-ring grooves to relieve a little pressure on the bolt.
After these two fixes, the bolt started to cycle the way it was intended. In order to achieve semi-automatic dryfiring, we had to rig up a hose system to imitate our future trigger. This is roughly what we came up with…
In this setup, pressure is supplied by separate hoses. The firing pressure is constant as it will be on the final version, and an air gun is used to dump pressure from the control chamber in place of a solenoid-actuated valve. We did have a problem off the start because the trigger pressure input was pumping air too fast for the air gun to dump it. this was causing the chamber to remain at too high a pressure for the bolt to cycle. to fix this, we basically jammed a plug into the input hose to slow the rate at which air could flow through it just enough to allow the bolt to cycle. With this setup, we achieved semiautomatic fire without ammunition.
At this point I am returning to this post after over a year of absence, so my recollection may be a bit fuzzy. I apologize for any inconvenience.
In order to feed paintballs into the gun, we decided to create a basic hopper feed system by boring a large hole in the top of the gun. We then threaded the hole and created another piece that fit tightly onto the neck of a hopper and threaded into place on the gun.
Since this was the first time we had to do anything on a different axis than the firing axis, it meant we got to use a new toy. Brian had recently bought a four jaw chuck that was useful for this type of operation. The mount for this job is pictured below. The hole was started using a wood bore bit, and the hole was widened using a boring bar.
After making both parts, we attached a hopper and voila! It is amazing how much that hopper makes it look like a gun.
We rigged up our makeshift trigger system (partially pictured above) and took it outside to try firing it a few times.
Now that the firing mechanism is operational, we need to set up a trigger mechanism. The primary phase of this process will be the design of the solenoid valve. A concept is shown below.
First: A cross-section of the valve Second: A full image of the valve hammer
This valve will be actuated like a solenoid. There will be a copper wire winding around the left end of the valve body which will pull the hammer back when charged.
In the rest state, pressure will be routed through the valve as such:
With the valve in its rest state, constant pressure is applied to both the control chamber and the firing chamber. Due to the pressure in the control chamber, the gun does not fire. Once the valve is actuated by an electric current through the solenoid, the air pressure will behave as such:
With the control pressure now dumped, the present firing pressure will be able to fire the weapon. After firing, the source pressure will return the hammer to its original position as soon as the solenoid is deactivated, allowing the recharge of the control chamber.
Hopefully with some refinements to this design, and a free weekend to build, Brian and I can get a real paintball gun together. We still have to deal with making the gun run on CO2, which brings in a whole host of regulation and expansion issues, but I think we are fairly close to a workable product.
I am sorry to anyone who was affected by my delay in posting this write-up, and I hope you enjoy its contents.
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Following the first day of work, we had nearly completed both the bolt and the charge chamber, and had completed the boltstop. In this session we needed to finish up these parts and create the firing chamber. Brian and I had high hopes going in to this session. He was confident that we would at least fire a shot by the time I had to head home. I was somewhat skeptical! Although we were interrupted by some thermite and Doctor Mario, we were able to achieve this goal.
We did the usual shaping and machining to get the firing chamber roughed out and then got on to the fun stuff… threading. Three parts needed threads. The firing chamber and charge chamber had to thread together at the middle of the gun; and we had to thread the inside of the front end of the firing chamber in order to put one of our Spyder barrels into it. The charge/firing chamber threads would be somewhat simple, as they only have to match each other and require no standardized dimensions. The barrel, on the other hand, has its own thread type that we would have to match. Just to make things more fun, The threads were metric, (M22 x 1.5) and our thread turning gears were standard. Brian worked his magic and got something pretty close to the barrel (7/8 x 16) and we went with it.
External Firing Chamber Threads
Internal Barrel Threads
Whole Firing Chamber
And I have saved the internal threads from the charge chamber for last to present you with a conversation that took place just moments prior to the cutting of the first internal threads we had done.
Joe and I: “Brian are you sure you want to do this without a practice run or anything?”
Brian: “I know what I am doing.”
He apparently wanted our threads to look like the mouth of the Kraken, but as long as he knew what he was doing, who were we to question him! 🙂
The embedded video shows our first paintball break on target.
The graphic above shows the air system we had set up when we fired the gun. Constant pressure is supplied to the firing pressure input, where the pressurized air waits to be released and force the ball from the gun. The bolt is held back by air pressure from the trigger pressure input. Whenever the air gun valve is open, this pressure is supposed to be keeping the bolt to the rear and keeping the gun from firing. Whenever this pressure is released (the air gun is pulled away from the input) the firing pressure should cause the bolt to move forward and the gun should fire. This wasn’t happening for us due to what we speculate to be general surface finish and O-ring fitting issues. With some further work and refinement this should be fixable. We ended up poking the back end of the bolt with random stuff and that provided the motivation required to start the firing cycle.
Once Brian had gotten his design work fairly completed, we knew it was time to dive in and start our construction. I got a free weekend and headed up to Brian’s for a long day of trial, and hopefully not too much error!
We decided to start work on the smallest and most simple part to sort of “get our gears turning” on the lathe. 😉 This part was the bolt stop, as shown in the picture below and depicted in yellow in the previously posted CAD screenshots. We somehow proceeded to pull it off without a hitch and moved on to some more “interesting” parts.
After selecting the Smart Parts Ion as the basis of our paintball gun project, the next phase was to get the design details worked out. Designing on paper is a lot more efficient that trying to work out details in metal as we were doing when we started the project.
The main goal of this part of the project was to get detail drawings made of each component, with the analysis to back them up and ensure the gun will function as desired. Ideally, this work would be done in a solid modeling package with detail drawing support. At the time, I hadn’t found a good solution that was in my price range … I mean free. Fortunately, I stumbled upon Creo Elements/Direct Modeling Express, which fit the bill nicely. I’d highly recommend checking it out if you’re looking for a solid modeling CAD program for hobby work.
With the CAD question answered, we needed to get started on the design. Again, ZDSPB.com was a great resource. The cross-sections, animations, and functional descriptions were extremely helpful, and enabled us to reverse engineer the Ion without having access to one.
Instead of simply copying the design, we wanted to make a few changes along the way. Our design should operate on 90 psi and uses standard NPT fittings rather than microline. These changes facilitate hooking the marker up to an air compressor, and minimize the cost of hardware we have to purchase. Using an air compressor should allow us to do some initial testing of the firing assembly without having to make or buy a high pressure regulator like you’d find in a regular paintball gun. We also simplified a few areas of the gun to better suit the limited capabilities of my shop.
The drop in pressure required some math to determine the required dump chamber volume. Without going into too much detail, we put together a spreadsheet to calculate the velocity of the paintball as a function of chamber volume and operating pressure. It’s surely not exact, but it should be close enough to work. Here’s the predicted projectile velocity as a function of time for 80 psi in the dump chamber in our design:
Ben came over for the weekend a couple of months ago, and we were looking for a project to do in my fledgling machine shop. He’d never really used machine tools, and I hadn’t done any “real” machining in my home shop yet, so we were looking for an excuse to pick up some experience. Ben’s in to paintball, so we decided to try to make a paintball gun.
We tossed around making a Spyder clone since that’s what Ben’s taken apart the most, but decided not to because I wasn’t sure how we could make the stacked tube housing with the tools currently in my shop. Keeping things to a single centerline makes them a lot easier to make on a lathe!
The next type of gun that came to mind was the Tippman style marker. They work on basically the same principle as the Spyder, but are arranged in a straight line rather than two stacked tubes. However, neither of us had ever owned a Tippman, so we couldn’t just make up the design from memory. We did a bit of research and came across a great site in ZDSPB.com. With the info on that site, and a few crude hand sketches, we headed out to the shop to “get something done.”