UrPeaceKeeper Posted March 12, 2007 Report Share Posted March 12, 2007 I was thinking about this today in class (yes, rather then paying attention to the Enron Movie) and I remember someone mentioning that its going to take alot of gas to move the barrel back and forth on each shot. I'd just like to point out that yes, by following the original design it would but if you were to use bearings around the barrel's end would that reduce friction enough that it would be effecient enough to move it using gas? Bearings DRASTICALLY reduce friction but its not what I'd call exact replica but it certainly allows them to acheive what they want. Link to post Share on other sites
Catman Posted March 12, 2007 Report Share Posted March 12, 2007 [..]Calculations[..] Looks fine to me *cough cough* I think fuse in my head just went pop Looking at it, to replicate the real M2's firing/recoil action: the bolt travels ~182mm and at a rough guess'timate the barrel recoils ~50mm If you look at this: You'll notice how the bolt and barrel move. I'm thinking it'd be a lot easier to move the bolt back the 130mm then for the last 50mm pull the barrel back rather than doing it first - less mechanical bits to break/go wrong. And yeah heavy use of bearings will be required Link to post Share on other sites
amateurstuntman Posted March 12, 2007 Report Share Posted March 12, 2007 OK, that gives me some numbers to work with, I drew this without knowing the distances and I don't know how much space you have inside your receiver so I have missed a few parts of the drawing (notably the piston but there are a few places it can fit into this design). This design will allow the bolt and barrel to recoil together and then go forward separately. In essence it is a gas cocked springer. Stay with me. It gives very stable fps that can be changed by swapping springs around (with a bit of thought the spring change can be made very quick and easy) and means that adjusting the gas pressure will only effect the rof. It also means you can have a single action spring return piston. Also manually cocking it will actually cock the weapon and it can be fired in single shot without any gas pressure at all. You can have the bolt return with a nice metallic clang and if you design and make your own piston and cylinder you can have a nice clang from them too. The trigger will actually release a sear and will have a very realistic feel. OK picture: Right in the above pic is a (very - sorry) simple pic of the internals. The black components are the piston and the spring stop which is drawn in totally the wrong position, if it was there the piston couldn't possibly go far enough back. the operation should work like this: 1. you cock the weapon, the red bar is drawn back by, but not attached to, the cocking handle. One of the main sears (white) catches the outer barrel (grey) and draws it back. The other main sear catches the piston (black) and draws it back. The white dots above the red bar are bolt heads or any movable metal part, they function like a cam. When the outer barrel has travelled it's 50mm the cam tips the sear and the outer barrel returns. The piston is still moving back with the red bar, when it goes past the auto sear (green) it's sear is disengaged by another cam. In this pic I have ommitted for clarity another sear in the same position as the green one but released by the trigger. Now you release the cocking handle and the red bar moves forward. The main sears are sprung and ride over the piston and outer barrel. The piston is held in place by the auto sear (green) and the trigger sear (not shown) When the red bar has fully returned to battery it releases the auto sear but the piston is still held in position by the trigger sear. 2. You pull and hold the trigger: The trigger sear releases the piston and the shot is fired. The gas piston activates (I have not shown the mechanism that activates the gas because it depends on the internal space in the gun) and pushes the red bar backwards recoiling the barrel and setting the piston. Now the piston is held only by the auto sear as you are still holding the trigger. The piston remains in position until the red bar returns to the battery position and releases the auto sear at which point another shot is fired. repeat millions of times. nb. I have sketched a quick loading nozzle idea, the inner barrel remains in place and a nubbin on the inside of the outer barrel moves the loading nozzle back right at the end of it's 50mm travel. The yellow part is the cylinder and an extension that leads to the loading nozzle. I have drawn the barrel return spring being mounted against the front of the cylinder but it doesn't have to go there. I think this system will be better than an escort type system in that is has more moving heavy metal parts that will make a lot of clatters and clangs and the fps will not be altered by cooldown on long bursts Also you could have the piston hit something outside the cylinder before it has gone it's whole stroke length which will make a lot of noise on firing. Anyway I hope this helps a little, just an idea. Stunt Link to post Share on other sites
Catman Posted March 12, 2007 Report Share Posted March 12, 2007 Cheers for that! Maddog is coming over in about an hour so I'll print that off for discussion. We're going to use an air-piston and compressed air/gas to push the bolt back, the idea is that the bolt will be spring loaded and as it pushes the air-piston back in the air/gas in the piston is then routed down the barrel projecting the BB. Hopefully we can get a diagram of this up tonight but if not you'll all have to settle for more pics of rusty steel, angle grinders and people jumping up and down on a bit of metal in a vice Link to post Share on other sites
Catman Posted March 13, 2007 Report Share Posted March 13, 2007 Day Two - Monday 12th March Sanded some more rust off the side panel Cutting out the second side panel. Angle grinding at night, pweetty That tulip is probably having a bad day. Two side panels and the top peice together. Damn it's big. Trying to hash out the internals: (the pics I took of this didn't come out too good :/) We clamped the two side panels together so that we could grind down the sides so they're exactly the same shape Maddog is going to draw up some of the internals in CAD. We're going to only have 100mm travel with the piston but to get we'll do some lever 'magic' so that theres a pretend bolt doing the full ~180mm. We'll have an impact plate so the piston isn't taking the full brunt and we should get a fair noise out of that Link to post Share on other sites
MadDog Posted March 14, 2007 Author Report Share Posted March 14, 2007 Okay, done some more work on what we are going to put in this thing, it's not finished but I need my bed so hears what i have so far. As the piston moves back it will pull the outer barrel back, and the loading nossle. half way through it's cycle back it will release the loading nossle loading in one BB (mech not yet drawn). When at the back of the cycle the valve will be switched, venting the gas now in the piston, down the barrel, launching the BB. The piston will then be pulled forward by a return spring until it reaches the front of it's cycle, where the valve will be switched again God knows if this will work, but there's one way to find out Link to post Share on other sites
Catman Posted March 14, 2007 Report Share Posted March 14, 2007 God knows if this will work, but there's one way to find out hellyeah it'll work Like the red "hose" lines, done in paint? btw you left that bit of paper in the workshop: "25.8mm major, 24.4 minor and 1.7mm pitch" (though I suspect that's out and it's 1.5mm pitch) Link to post Share on other sites
zentaurus Posted March 14, 2007 Report Share Posted March 14, 2007 bravo, dudes. this should be a real gas (literally too ) when it's done. ledpocket, candyman, watch out zT Link to post Share on other sites
airsofthawaii Posted March 14, 2007 Report Share Posted March 14, 2007 Wow guys this is looking so great! I am really hoping this project wont die, I would really like to see this built and able to fire. I was thinking about making the smaller ww2 30 cal. Best of luck to you guys, please continue keeping us informed with pics and such. Link to post Share on other sites
Catman Posted March 14, 2007 Report Share Posted March 14, 2007 Cheers guys! More work to be done on it tonight so providing the forum is working tonight they'll be some more pics to peak at later The Project after this will most likely be a stationary rocket launcher system - something (very) loosely based off the TOW or MILAN design - but that's a discussion for another thread As for the .50cal, we're planning on having it vehicle mounted - we'd like to do a swivel turret system like they have in the Hummers but not quite sure how we'd do that yet. edit: oh yeah, MadDog and I were discussing "over heating", if you've played those games like BattleField2: on the mounted machine guns if you fire too many rounds at once it over heats. As the .50cal is going to be a club gun they'll be a lot of people having a go on it - in order to stop them just laying down constant fire we were thinking it'd be cool to have such a system. Link to post Share on other sites
lord_marmite Posted March 14, 2007 Report Share Posted March 14, 2007 If you could make a system that after a certain period of trigger pull it stops firing with a click, and vents some gas out from under the recoil sleeve thing with a hissing sound much like you would get on a real one due to the heat, that would be the icing on the cake. as for suggestions on how to do this, i have no idea lol as before keep up the good work! Joe Link to post Share on other sites
UrPeaceKeeper Posted March 14, 2007 Report Share Posted March 14, 2007 Catman, IIRC the HUMVEE uses two circular sleeves with ball bearings between them and a small pull latch. One of the sleeves (the outer) is attached to the vehicle, and the inner is on a track on the inside of the other sleeve. The seat is made of some car seatbelt material so its extremely strong. The Turret has two different turning modes, one where it latches in a position and the other is free rotate. The latch one has a small spring loaded latch that will allow you to turn the turret in a direction but it locks after you stop spinning. The free rotate just locks the locking pin out so it doesnt catch. As stated MSN Paint Drawings WOOTAGE! Alrighty in this picture here are what the colors are: Green - This i the inner sleeve, the rotating part and the part that the person sits on as he rotates. Brown - Outer sleeve, attaches to vehicle's roof Yellow - Handles to aid in rotating the rotate Red - Seatbelt webbing that is used as a seat Blue - These are the actuall Pintle mounts where the M2 or other gun attaches. This is the cutaway picture, in this picture here are what the colors represent. Green - Again inner sleeve Brown - Again outer sleeve Grey - Ball Bearing of industrial proportion Sorry for the crappy looking images we all know how hard it is to throw something REALLY good together in MSN Paint As for the shot counter, you could use some IR or Laser Counters to coun the number of BB's traveling through the end of the barrel, as it counts up when it reaches a number it could cut off power to the firing system and fire a small solenoid valve for the heatshield "overheating" affect" Then after a timer reaches 0 again it resets the entire system. Unfortunately this means every x amount of shots it "overheats" That would be a good start to the system for overheating. If you really wanted the overheating affect you could use a gas that has a Cool down affect so it just stops cycling when he fires Link to post Share on other sites
Pyromaster Posted March 14, 2007 Report Share Posted March 14, 2007 Hey Catman, do you want me to adapt the counter circuit to see if I can program the PIC18X to do the cooldown sequence? Link to post Share on other sites
Tecro Posted March 14, 2007 Report Share Posted March 14, 2007 Nice job guys, you look really dedicated to making this work. I'll be watching this project fanatically. Looks fine to me *cough cough* I think fuse in my head just went pop <{POST_SNAPBACK}> Same reaction here . The figures look about right, but I probably missed stuff anyway. Looking on Wikipedia (where else?!), it looks like the Browning Fiddy Cal uses a short recoil system. Ie, the barrel/chamber and bolt assembly recoils together a bit, then the bolt recoils much more. I'm trying to find info on how far the barrel recoils. But if its recoil length is only a few centimeters, then you could just connect a plastic outer barrel to the piston. It would also help reduce the ROF to 500 RPM. An overheating system would also be a neat addition. And maybe fake barrel replacement. But for overheating, you could divert a bit of the air from each shot into an "overheating chamber". The OH chamber has a plunger and spring, and as air is added in, the plunger is pushed back. If the plunger is pushed back too far, then a valve cuts off the air supply and you can't fire. There's also a tiny hole somewhere in the OH chamber that slowly lets out air. The plunger must then move (nearly) to its initial position before the valve is opened again. A simpler option would be to have the plunger directly connected to the valve, but then you wouldn't have the whole "wait for cool down" thing. I understand you have your own plans for the internals, but these are just suggestions. Link to post Share on other sites
lord_marmite Posted March 14, 2007 Report Share Posted March 14, 2007 You could also programme the counter so that after say 100 shots you must rack back the charging handle to simulate a reload. Link to post Share on other sites
Catman Posted March 15, 2007 Report Share Posted March 15, 2007 For the vehicle mount I chanced apon this the other day while looking/drooling over M2 pr0n the big issue is finding something that's round and strong enough to work for the ring. Hey Catman, do you want me to adapt the counter circuit to see if I can program the PIC18X to do the cooldown sequence? <{POST_SNAPBACK}> No worries m8 that counter is for another project - my super secret "that am not mil-sim" project We already have a counter for this, it's an air-counter that clocks everytime there's a burst of air passed through it. Not sure we'll use it as it's quite big. For the "overheat" system we're looking at having an internal tank within the body - MadDog reckons we just feed from the large external tank to the internal one which has a shut off valve, so you have to release the trigger to recharge the internal tank a pressure/flow regulator will prevent it from having the weak shots/action when the tank is almost empty. As for the recoil, the piston is going to move 100mm, looking at the pictures of the real M2 it looks like the barrel moves roughly 50mm, we're going to keep it simple and move the barrel 100mm - which isn't going to be a problem as we're ordering in some rather niffy ball-bearing tracked bushings. The Bolt needs to travel 185mm but we're going to use some lever action to turn 100mm travel into 180mm. Looks like the cocking handle won't do much apart from pull the fake bolt back but that should still feel good and make a sweet noise. The ROF will be adjustable via the piston as it has an intake/outtake at the top of the bottom. So all we need to do is adjust the airflow out the back to alter the ROF. We're going to try and buy some dummy .50cal rounds on links for it too. Details are sketchy atm but we're planning on drilling through the rounds and passing a flexible tube through which the BBs will be feed from. I'd like to get one of those spring-like feed tubes as seen on the STAR M249 box mag (for example) but we'd need a massively long one for this. Gas and BBs will be contained within the ammo box that'll be on the side. Thanks for your input guys we're still hashing around with the internals so there's a good chance we might go with suggestions, +1s dished out Day 3 - Wednesday, 14th March After some more cutting and grinding so the sides are flush I hold the body pieces together: MadDog puts in the first weld, note the box of flammable wooden bits and our fire extinguisher (yes the pan of water that I "put" BBs into *cough* ) Hmmm smokey, the bit of wood underneath gets a tad hot After a bit more welding, *Cough cough* The smoke clears and sitting proudly is.... Front and back plate welded on, the top piece is just resting Need to grind the edges down now. The piston and some of internals will be mounted on the bottom plate so it's easily gotten too - also means they'll be no impact against the rear plate (thus very safe ) Oh yeah, it already weighs a fair bit Link to post Share on other sites
swedge Posted March 15, 2007 Report Share Posted March 15, 2007 For the vehicle mount I chanced apon this the other day while looking/drooling over M2 pr0n the big issue is finding something that's round and strong enough to work for the ring. looks like a wheel with the middle missing? could you get busy wi that angle grinder and cut the centre out of a tractor wheel, then use the rims as runners for a rolling gun mount using skateboard wheels and the like? just an idea! Link to post Share on other sites
1st Commando Posted March 15, 2007 Report Share Posted March 15, 2007 it's a shame that more power will be required as using propane would mean that it would suffer cooldown and that in itself would create the "overheat" time required for realism. I was discussing last night the possibility of a MK19 40mm project once I cut my hours back at work a bit, so I shall be watching your project with great interest ! Good luck guys ,looking good Link to post Share on other sites
creepingfear Posted March 15, 2007 Report Share Posted March 15, 2007 The eyes of a killer if ever I saw one. Be afraid...............be very.....afraid Link to post Share on other sites
tomster Posted March 15, 2007 Report Share Posted March 15, 2007 Awesome project, I'm looking forward to seeing how this develops! Link to post Share on other sites
Pyromaster Posted March 15, 2007 Report Share Posted March 15, 2007 Yo caman, just to say, the guy in the Gunshop in Douglas has a load of 50.cal deacts that he can get for you.... Link to post Share on other sites
Catman Posted March 15, 2007 Report Share Posted March 15, 2007 Sweet I might swing by on saturday and pic 'em up Link to post Share on other sites
MadDog Posted March 17, 2007 Author Report Share Posted March 17, 2007 Some more planning, Basically I've added in the loading nossle, which will be operated by the same bolt as the rest of the system, but when it has travelled the desired distance back it will disengage via a small latch on the back. Bit hard to see in the picture, but its there. Link to post Share on other sites
Catman Posted March 17, 2007 Report Share Posted March 17, 2007 I still dunno what was wrong with my design plan Link to post Share on other sites
Victory Posted March 17, 2007 Report Share Posted March 17, 2007 Yeah...I do like CatMan's idea a bit better...good try though, MadDog. -Vic Link to post Share on other sites
Recommended Posts
Archived
This topic is now archived and is closed to further replies.