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Thread: Mech Warfare Weapons Guide

  1. #1

    Mech Warfare Weapons Guide

    Greetings,

    There have been quite a few threads on the topic of airsoft guns, and I thought I'd try to compile all info on MW weapon systems into a guide. Ideally cutting down greatly on the number of separate threads discussing guns, and making it easier for people to find info they are looking for without reading through 10 separate threads (or starting a new one).

    I'll attempt to include as much information as possible, but I'm bound to forget something (or get something wrong). Just post what you think should be included (or changed) and I will add it in .

    Choosing a Gun:
    The MW scoring system uses 3.5" square target panels to detect the impact of projectiles, with a maximum rate of 1 hit per second. The purpose of your weapon is to trigger the target panels, preferably in an accurate, reliable manner from across the arena. In the airsoft league your weapon cannot be any more powerful than an airsoft gun.

    While Nerf weapons (foam darts) are allowed, they are not recommended. Nerf guns tend to be large, heavier than airsoft guns, and darts are very large compared to bbs (and you need at least 20 hits, which is probably a few hundred shots on a good day ).

    So, airsoft guns. There are two main types of airsoft guns used, and I'll start with the easiest (probably) to use: the "defender" style gun.

    Defender:
    There are many different guns that fall into this category, but I recommend this one: http://www.amazon.com/Pulse-M74DP-AE...=crosman+pulse.

    To put one of these types of guns on your mech, you'll probably want to chop of some of the unnecessary plastic pieces, remove the semi auto mechanism, as well as some other modifications mentioned here (adding a spacer as detailed there helps keep the gears from stripping). There is really only one ready made solution for mounting a defender, which you can buy here, the kit also includes parts to make modifications, and is probably a good solution if you pick a defender.

    AEG Gearbox:
    The other option is to purchase a stand alone gearbox. This is a good option because it will be lighter and smaller than the defender (which has its gearbox built into the plastic shell). The disadvantage is that you have to come up with your own hopup solution (the part which connects the gearbox and barrel, and is where the bbs go before being fired). The most commonly (read: only) gearbox used is the double eagle gearbox.

    Note that any AEG will likely work fine if you're willing to design your own hop-up and mounts. The main reason we use the Double Eagle is that they are very affordable, and once there's a little bit of a standard, it's easier to stick with that than re-design from scratch.

    Jwatte's DE Gearbox Setup:
    If you've decided on the DE Gearbox, one of the most easily available hopup/hopper solutions is Jwatte's setup. Purchase the parts off of shapeways (strong and flexible plastic is recommended), or print them yourself. Then just add a defender barrel, some pipe for the hopper and a micro gear motor for the agitator.

    Feeding Your Gun (The Hopper):
    So, you've got your airsoft gun, now you'll need a way to get bbs into the breach to be fired. The defender has a built in hopper, but I've found it doesn't work too well. Basically the hopper is a box (or other hollow shape) that sits on top of your gun and is full of bbs, and after a bb is fired another one falls into the chamber (thanks to gravity). There are of course, force feed hoppers, but I won't discuss those until myself or someone else manages to make one that works reliably (I believe Gdubb made one a while back, but I don't remember how well it worked).

    A good hopper will have a good bb capacity, and there isn't much reason to not bring as much ammo as you can fit. To help prevent jams, it's a good idea to add an agitator of some sort. Basically a piece of something that spins around in your hopper to keep the bbs in motion, usually actuated by a continuous rotation servo or micro gear motor.

    Jwatte has a pretty nice hopper on his design (which is intended to be used with his double eagle gearbox hop up unit).

    Powering Your Gun:
    You'll need to be able to control your gun, and run it off of a battery. 5-6V is probably about right (you don't need to fire that fast as you can only score one hit per second). There are a few ways to accomplish this:

    Relay/MOSFET:
    Relays and MOSFETs are pretty straightforward and easy to set up. The only downside being that the closest LiPo is a few volts higher than the preferred voltage for the airsoft gun. Keep in mind that airsoft guns pull a lot of current, you'll need something with a pretty beefy current rating. I'd recommend something around 30A or more. While it might be a little more than necessary, there is really no reason to cut it close.

    Pololu Motor Driver:
    Probably the most popular option, and for a good reason. Motor drivers are reliable, and can get your 3s or 2s lipo down to the right voltage. Pololu motor driver boards are a proven and reliable solution, I'd recommend this one if you only have one gun. Others have had success using this one, or this one for multiple guns.

    Hacked AX-12:
    Another solution, which has the benefit of being able to be plugged directly into the dynamxiel bus, is to hack an AX-12. Basically remove the motor and solder the gun motor leads in, then set the dynamixel to wheel mode and control the gun just like another servo. Note that I haven't actually tried this, but I believe that Immortal's guns are driven this way.

    Onyx Fire II:
    Jwatte designed the Onyx Fire II specifically for MW weapon systems. It can be plugged directly into your dynamixel data line and can be easily controlled just like a servo. More details and features can be found here. You can purchase one here.

    Custom Motor Driver:
    Some mech warriors have opted to make their own motor drivers. While it might be more work than purchasing one ready to go, it offers the benefit of being specifically designed for mech warfare, as well as supporting any features one might desire. More on this in the future.

    Triggering False Hits:
    Because of the high current spike the gun draws, and/or the gun's motor, the gun can put out a lot of EMI. This can cause your scoring panels to trigger when you fire your own gun (not good). Here's a few tips if you are having this issue:
    - Keep your panels away from your gun.
    - Keep your scoring panel leads away from your gun power cables.
    - Twist your gun power wires, in theory this should cause the EM fields to cancel out.
    - Shield your panel wires and or gun wires.
    - Don't run your gun power wires parallel to your scoring panel leads, try to make them perpendicular to each other.
    - Add a capacitor, this should help with the big current spikes.

    More to come in the future, and I'll try to add some pictures to break up the intimidating wall of text . Lemme know if I'm missing anything!
    Last edited by Deimos; 05-09-2014 at 02:27 PM. Reason: Now with more bold!

  2. #2
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    Re: Mech Warfare Weapons Guide

    The trossen store sells a kit for modifying and mounting a defender; just add the defender and a hopper. It uses a relay and includes a 7V5A power supply, but that appears intended more for stationary turrets and non-MW rovers.

    The defender gearbox has a tendency to strip its gears if one of the modifications detailed in the trossen instructions is not followed (a thin spacer added to keep the gears better aligned/mated). Stripping gears renders the defender good for only parts (barrel and maybe hopup), unless you manage to procure replacement gears.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  3. #3

    Re: Mech Warfare Weapons Guide

    Added a bit about that in the "Choosing a Gun" Section. Thanks for mentioning it!
    Last edited by Deimos; 01-27-2014 at 04:08 PM.

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    Re: Mech Warfare Weapons Guide

    Looking good. This was definitely much needed. I'm planning on using a force-fed hopper this year, so I'll report back how that goes. In addition, I may be able to supply additional CAD for hopup and gun mounting. Thanks for setting this up.

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    Re: Mech Warfare Weapons Guide

    Fantastic effort, make this a sticky? Great if we can list custom driver board solutions and hopper 3D designs offered by the community as they become available - thank-you to all the guys making their hard earned design work accessable to the rest of us.

    Speaking from the perspective of a newcomer, I have just about finalised my first robot build and overall I have found the AEG solution the most confusing, perhaps due to its specialisation, little off-the-shelf parts and few collated sets of information. In addition, due to my lack of access to 3D print manufacturing, its another contributor barring access and participation in mech warfare. As experience and toolsets grow this will be less of a problem, however im talking about the newcomer here.

    Finally, I have found it difficult to source either the double eagle or crosman from European suppliers. Anyone aware of European supplier or all ordered stateside?

    Great work again, invaluable concise source especially for the newcomer. +1 rep.
    Last edited by Grumpybeard; 01-25-2014 at 02:51 AM.

  6. #6

    Re: Mech Warfare Weapons Guide

    I'm planning on using a force-fed hopper this year, so I'll report back how that goes. In addition, I may be able to supply additional CAD for hopup and gun mounting. Thanks for setting this up.
    Sounds good!

    Great if we can list custom driver board solutions and hopper 3D designs offered by the community as they become available - thank-you to all the guys making their hard earned design work accessable to the rest of us.
    Great idea! If anyone has a hopper / hop up unit / driver board they think should be included just let me know.

    Finally, I have found it difficult to source either the double eagle or crosman from European suppliers. Anyone aware of European supplier or all ordered stateside?
    I believe Xevel had a similar problem, and I think he found some DE gearboxes that a local store was going to throw away (very lucky). You might see if he could point you in the right direction.

  7. #7

    Re: Mech Warfare Weapons Guide

    Note that any AEG will likely work fine if you're willing to design your own hop-up and mounts. The main reason we use the Double Eagle is that they are very affordable, and once there's a little bit of standard, it's easier to stick with that than re-design from scratch.

  8. #8

    Re: Mech Warfare Weapons Guide

    Note that any AEG will likely work fine if you're willing to design your own hop-up and mounts. The main reason we use the Double Eagle is that they are very affordable, and once there's a little bit of standard, it's easier to stick with that than re-design from scratch.
    Noted . Seemed to fit nicely so i just pasted your comment into the AEG gearbox section .

  9. #9

    Re: Mech Warfare Weapons Guide

    >> but the magnetic field it generates tends to mess with the scoring system, causing false hits.

    No, it doesn't. I've conducted tests, posted the results, and provided well-reasoned theory why this is not the case. Why does this urban legend persist ? If someone has conducted tests that show otherwise, please post them.

    Again, I hate to steer potential builders away from such a simple, inexpensive solution.

    Otherwise, it looks great

    Thank you,
    CogswellCogs
    Last edited by CogswellCogs; 01-27-2014 at 09:30 AM. Reason: typo

  10. #10

    Re: Mech Warfare Weapons Guide

    No, it doesn't. I've conducted tests, posted the results, and provided well-reasoned theory why this is not the case. Why does this urban legend persist ? If someone has conducted tests that show otherwise, please post them.

    Again, I hate to steer potential builders away from such a simple, inexpensive solution.
    Fixed. I must have missed that discussion .
    Last edited by Deimos; 01-27-2014 at 04:08 PM.

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