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About Molybdenum

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  • Airsoft Replicas Owned
    JG g36c (project gun) CYMA AK74u An assortment of homemade monstrosities that never work quite right.
  1. Yes, though in all likely hood you will not be able to see the gauge move much if at all on a shot-by-shot basis. The amount of air in even a small 13 CI 3000psi tank is quite large compared to the amount of air required to fire an airsoft pellet. It is totally possible from a mechanical standpoint to have and adjustable regulator that screws into the HPA tank and goes all the way down to 0-150 psi (even if you have to do it in stages). Custom Products makes such a thing (with two stage regulation. Here is the page), and though I can't personally attest to it's quality and usability, it purports to fit your criteria. Keep in mind that the threads on this thing need to hold back 3000-4500 psi of air pressure, so you should thoroughly research the correct procedure for installing it. Sorroritas? That avatar looks familiar.
  2. The gauge screws into the regulator which screws into the tank. Typically that gauge will show the pressure in the tank, as the tank regulator will often have a fixed output pressure. Tank pressure dropping below the regulator output pressure will most likely cause a drop in muzzle velocity and slow/incomplete cycling before the gun fails to fire entirely. The number of regulators you need is purely governed by the pressure you need at the output and the availability of the hardware to get you there. The two-regulator setup is common because tank regulators that output ~800psi are common, as are the easily-adjustable paintball regulators that can bring that down to 0-150psi.
  3. Today I pulled an old M28 out of the closet, and promptly discovered why it had sat there for so long. When the bolt is pulled back into the cocked position, the bolt assembly can't be pushed back into the forward position. Pulling the trigger will usually allow the bolt assembly to slam forward back into the rest position, but sometimes it requires an uncomfortably generous application of force to break past the sear and decompress the spring. I imagine pushing past the sear isn't exactly the best for the well being of the trigger group, but I am loath to leave it stuck there. If I remove the stopping pin that keeps the spring guide from moving with he bolt assembly, I can manually latch the piston onto the sear an push the bolt assembly forward until about 1 cm from the fully forward position, at which point the piston releases and the spring decompresses. My assumption is that there is something wrong with the trigger assembly. All of the parts seem intact from visual inspection, but it has been years since I last looked at it so it is entirely possible that something is out of place or missing entirely. Has anyone experienced a similar issue or care to offer some insight into what might be wrong? EDIT: For what it's worth, I fabbed up a new spring guide that fit the ID of the spring a little tighter but saw no change in operation upon swapping it it.
  4. "I have a programmable MOSFET" is one that bugs me, probably a lot more than it should. There is no such thing. You have a programmable motor controller with FET switching.
  5. A the amount of force a compressed spring exerts is proportional to the distance it is compressed by a spring constant (K). If you have a set of springs whose equivalent FPS output is known, you can observe how far it is compressed by a certain weight. Any spring that is compressed the same distance by the same weight can be said to have the same stiffness. The problem is different spring lengths of the same stiffness will produce different velocities. This will only get you close. EDIT: The energy difference between two springs of different lengths but the same constant when compressed into the same space should just be the difference between the rest lengths squared times half the spring constant. That is, (K/2)*deltaX^2. Because velocity is also squared in the respective kinetic energy term, I would think velocity would vary linearly with extra length as follows: (velocity difference)=(Length difference)*sqrt(K/(mass of the bb)) typical units would be velocity difference in m/s, length in meters, K in N/m and mass in Kg.
  6. I'm actually in the process of hobbling together a pneumatic piece. If you have any specific questions I may be able to offer some help. Specific things I've learned so far and found helpful are: - A drill press is a lathe if you're creative. A piston can be created from a threaded rod through a piece of plastic. - Most of this hardware (especially plastic) can be expensive and/or hard to acquire for a hobbyist. Find a local business that does manufacturing, biomedical, robotics, whatever, and root through their trash. Got me a few good chunks of Delrin and HDPE from my current place of employment that were going to be tossed. - Programming microcontrollers is easy. Knowing where to start is hard. Rather than looking for specific chips, look for programmers and IDEs. Once you have those, select and appropriate chip. - Get a caliper. I got a digital caliper at Menards for like $15. Most productive $15 I've spent on this project by FAR.
  7. By "getting warm" do you mean top of a computer warm or to hot to touch? So long as the fuses aren't blowing, shorted, or melting, you're most likely fine.
  8. How universally true is this? Will fill valves generally be 10-32 for launcher grenades as well?
  9. Look into paintball masks. Dye I4s are known for being both comfortable and small, but they're a bit pricy so try them for fitment first if you can. JT proflexes are cheaper and could be easily cut if cheek-weld is a problem. Both of these masks may even be flexible enough to force a good sight picture simply by pushing the stock into your face. Plus, high end paintball masks are designed to be dragged to hell and back by tournament players (been there, done that). They typically feature tool-less disassembly, fast swap lenses, etc. Considering its the primary factor in both safety and comfort, its worth substantial investment IMO.
  10. It sounds to me like your gearing is not the issue. Make sure you don't have a short circuit.
  11. I made one a while back out of essentially spare parts. The new trigger electronics were housed in a grip from an electronic marker that was hollowed out leaving only the micro-switch and the trigger, then bolted directly to the original forearm. The old trigger hardware was covered with a sheet of plastic that I bent into shape and simply glued over the grip. Looks like crap, and the semi auto doesn't work, but it functions.
  12. Because volt divider of course *shrug*. The switching voltage on the specifies FET is only a few volts so he doesn't want to put the full battery voltage on the gate. Assuming that is the case, however, I'm wondering why he didn't go with something more like a 100K and 2.2 M resistors. Less current in the switch loop the better right? It's been awhile since I was last on these forums, and I'm surprised to find that this guide has stayed alive. With a better understanding of the circuit, however, I'm really not sold on that massive diode, even besides the fact that the unconventional airsoft specified one is like 5K watts . Assuming I read it right, the inclusion of the diode makes sense, but its "downstream" of the motor, meaning the breakdown loop includes the battery. That zener breaks down at 18V, the FET is rated to 40, so the fact that its a zener seems almost unnecessary. Assuming its there to deal with back EMF, I'm not convinced this is the best alternative as opposed to: -A beefier FET that can take the back EMF from the motor. Drop a few bucks for a big IGBJT or a big switching FET and the safety margin should be pretty good. -A cap across the motor. Might detract from your trigger response a bit, but I doubt it would be noticeable. -Running the motor from source to ground, with a zener across it to ground. This way you can specify the breakdown explicitly and the failure current loop includes only the diode and the motor. Plus is will completely negate any back EMF from the motor without involving other components. Thoughts?
  13. If its a cheap MM, .4 is probably the resistance of the probe/wire circuit, and its plenty low anyway. Just to be clear, does the motor still spin in the problematic setup, or do you get no connection at all? Also, it might be that the way you have the longer wire connected allows it to short against something, probably the gearbox. If all else fails, check that the wire is not pushing, pinching, or otherwise being unruly when fitted into the gun.
  14. The only problem is that the "good players" are often not so easy to identify off the field, and things are often to chaotic to judge on field unless your spectating. The dude in head to toe magpul will get asked lots of questions, but no one notices when when the guy in nothing but a cargo pants and a T-shirt single-handedly crashes the left flank.
  15. When you have no living expenses 100% of your income is disposable.
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