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Discussion Starter · #1 ·
Hey yall, I am so very sorry to post yet another DMR build thread, but after hours of scouring forums, reading related links, and going so far into airsoft tech work that I got lost, I am now, yet another, DMR noob. I have some questions based off a build I am wanting to do so let's get strait into the build. I will have links attached to the parts I am looking at using for this build and will cover all the information that I know/will calculate when time comes and ask my questions at the end.

Field Rules
The local field for where I live seems to have a very unique rule set compared to the ones I have been seeing throughout the threads. But the only ones that matter for this thread is the DMR rule set. They allow DMRs as long as they have a 20 inch outer barrel assembly. This can include any mock suppressors or just a whole barrel that is 20 inches long. However, the total gun length has to be 35 inches when the stock is in the shortest position if it is collapsible. The field joule limit for DMRs is 2.8 joules which appears to be higher than most field regulations. The minimum ingagement distance for DMRs is 100 ft. The gun must have a fire rate of one bb/sec and locked into semi or safe.

Goal
The goal is to build a DMR that will be right at field limits for FPS with the lowest possible spring rating to reduce stress on the gearbox and noise, have a slow fire rate, and be very accurate(this is a given in any DMR build).

The Gearbox
This section will cover the whole entirety of the gearbox build. I am most familiar with V2 gearboxes having done some tech work on previous rifleman builds. Because of this, I am trying to stick with the v2 gearbox which is very hard to achieve the power output result I am wanting without putting extra stress on the shell.

Shell:
From reading through the forums, it seemed almost as if the shell of the gearbox was one of the more overlooked items in the build. However, to me, a strong build is going to start from the gearbox shell itself. For this, I was originally planning to use the Krytac Nautilus V2 gearbox due to its outstanding strength, however, after doing my research, I found that this gearbox is very proprietary and thus does not accept a wide range of components. Since then, I have planned to go to the Retro Arms CZ Billet 8mm V2 gearbox. The construction is made of 7075 t6 structural grade aluminum, and after building aluminum boats for 4 years I have faith that with the right bearing and shimming of the gears it will hold up to what I want to do. However, I can change just a few of the following components if need be to use the krytac gear box.

Bearings:
The next part I will include will be 8mm ball bearing by prometheus. I believe that these will help reduce the friction of the gears and increase the longevity of an aluminum gearbox.

Gears:
Following the prometheus train, I am going to use prometheus tripple torque gears for a v2 gearbox. I want to use these due to the higher spring rating that I will be using within the gun to ease the amount of stress the motor will see.

Mosfet:
This is probably one of the more confusing parts for me. From reading forums it seems as if everyone is including a mosfet, but the types and styles get scrambled in my head, due to this, i am going with the only mosfet I know of that is reliable based on research. I will be going with a Gate titan v2 advanced mosfet. This is how I will obtain the slow fire rate within the gun, and hopefully if possible the semi or safe only opperations. I will also have the precocking option enabled because why not! However, this brings the topic of anti reversal latches.

Anti-reversal Latch:
After reading countless of threads, the question of the ARL still lingers within my mind. The Gate titan mosfet does have the electric braking feature which is theory would eliminate the use of the anti reversal latch. However, for gearbox safety, many users are recommending to keep it installed. The one worry that I have with that, is being locked into semi only, I would hate to get 10 shots through and have the gear box go into the dreadful semi lock. This problem is easily solved with aegs that can fire full auto, but when your gun is permanently locked into semi, you would have to remove the spring to relieve tension on the gears. Without the ARL, you would not have the semi seizing problem. If an ARL is needed, I will go with a prometheus hard anti reversal latch.

Trigger:
Once again another underlooked component of the gun. Due to using the Gate titan mosfel, I will be using an adjustable MAXX trigger due to the precise adjustment to ensure positive contact and prevent damage to the mosfet.

Piston:
This is yet another Grey area for me. Based on the reading, you would want a heavier based piston due to forces with the lighter BB due to basic physics. If you are trying to push a heavier BB down a barrel, you have negative forces upon the bb traveling through the inner barrel compressing the air infron of it, in which will cause a need for more energy from the piston. The larger the mass of the piston, the less affect the negative forces will have. Within this, in my mind a metal piston would be ideal due to its high strength from impact, and the weight compared to a plastic. The number of teeth the piston should have is also confusing and if they should be full teeth or if the last two should be incremental to the rest. From reading, it seems as if a v2 piston should have 16 teeth, however some are made with more and some are made with less. Because of this, my piston is still unselected.

Cylinder:
For this, I am going to use a full MAXX cylinder to allow the most volume possible out of the gearbox. This will also allow for my to make adjustments and decrease the volume by finite amounts as needed to perfectly match the barrel length and volume while only trying to adjust one variable being the cylinder.

Air Nozzle:
For this, i plan to match the cylinder and go with a MAXX double o-ring 21.25mm metal air nozzle. This length should seat very well within the hopup and the double o-ring will help prevent leakage of air.

Cylinder Head
I plan to go with a double o-ring MAXX cylinder head as it should be compatable with the cylinder and air nozzle.

Piston Head:
For this, I thought it be best to continue with, you guessed it, MAXX. I will be using a MAXX double o-ring piston head. This piston head is my choice do to the other components used as well as the ball bearing allowing spring life and performance longevity so it is reliable and the same every shot. I will also utilize a sorbothane pad if needed to adjust the AoE and reduce noise from the piston head

Cut off lever:
Once again, another component i have no idea about. If someone would like to send me to a forum to read about the use of this, or explain, I would be so greatful for that!

Selector Plate:
For this, I will just be going with a regular run of the mill selector plate due to modifications that will need to be made to lock into semi only.

Tappet Plate:
The tappet plate from my understanding is what holds the air nozzle. Due to the fully upgraded parts and potentially high shock from a m160 spring (could be higher or lower depending on seals to get to 2.8 joules) I will be going with a prometheus reinforced tappet plate.

Hopup
The hopup that I will be going with will be a MAXX CNC rotary hopup due to the components used and the high precision and adaptability by MAXX on the hopup unit itself.

Barrel
The inner barrel is yet another area of conflict. However, I do know that I need to match cylinder and barrel volumes to help reduce noise and reduce the needed spring size in the gun for maximum output of the BB. For this, I am mostly confused as to if I should use a precision TBB (6.01) or a precision WBB (6.04+) after reading multiple forums, there is a mix of both answers. Some saying 6.01 is better for accuracy, while 6.04+ is better due to an air cushion around the bb, preventing it from hitting the sides of the barrel where on a 6.01 it could bounce back and forth between the tight tolerances. When reading about the barrel length, are you wanting to match your barrel your your cylinder volume size. Or your cylinder volume to your barrel? Also, it is a cardinal size to slap in extra long inner barrels, however, when you are at a required barrel length of 20 inches, it is best to have an inner barrel that is near 20 inches, say 500mm due to a loss of 9mm in the hopup, to allow guidance of the bb up till it leaves the barrel. With this, would the cylinder being a V2 gearbox and not an elongated V2.5 have enough air volume to support a 500mm inner barrel?

Motor
For the motor I will be using a Prometheus high torque motor. This will increase the motors time to full speed and help longevity with heavier springs.

Springs
When it comes to springs, i will be trying a vatiety of sizes starting at a m150 to see where my FPS will be at. My goal is to achieve a energy near my field limits without ever going over it.

Building
When building this gun, I know it will take time to precisely tune and shim every component to eliminate wiggle, movement, noise and prevent any air leakage. But would this build achieve me goals in the gun or what would yall suggest. My biggest questions are the blank spots within the build such as the piston and cut off lever. As well as the questions mentioned is the barrel section. I'm very sorry for the long post as to being a DMR noob, I hope I laid out enough information though for my questions to be answered. I have tried to do my dudiligence and research, but there is only so much you can answer on your own without asking questions. Happy shooting!
 

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Ummm...let's just start off and let me say.

This is Airsoft, there are no Standards and American Consumerism does not apply.

Some of the parts you picked above are not needed. Some parts are in fact a down grade for your application.

Before we discuss the merits of each part, which AEG are you choosing to be your DMR platform?
 

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Discussion Starter · #3 ·
Ummm...let's just start off and let me say.

This is Airsoft, there are no Standards and American Consumerism does not apply.

Some of the parts you picked above are not needed. Some parts are in fact a down grade for your application.

Before we discuss the merits of each part, which AEG are you choosing to be your DMR platform?
As for the aeg I am building the gun off of, I'm going to build the whole gun off a upper and lower. Depending on the gearbox shell I go with (krytac or Retro Arms) will depend on the lower and upper that I go with, however, I do plan to go with all metal. If I go with the Retro Arms shell, I will go with the VFC VR 16 upper and lower due to TM compatability. If I go with the krytac shell, I will go with the trident upper and lower.
 

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A few things that I know:
1. There's no point shelling out over $100 for a standard set of 18:1's. SHS or rocket gears are fine and are a fraction of the price of those prometheus ones. I'm sure the prometheus gears are high quality, but gears ain't worth that much unless they're siegteks.
2. Because the GATE titan runs using an optical sensor, you don't need a cutoff lever at all yay.
3. Stock anti reverse latch will be just fine, no use spending money on things that won't really help.
4. I doubt you'll need a fancy trigger for your GATE titan (aster units require one sometimes) because the trigger is sandwiched between the 2 boards and just passes in front of a sensor, so no contact, and no damage.
5. Lonex red (called "extreme toughness piston" or something) or the regular lonex red (full metal tooth rack) are good pistons.
6. When spring hunting, go with prometheus, guarder, lonex, ASG ulitmate, or modify. Stay away from SHS, matrix, lancer tactical, and evike labeled springs. <--- these brands have been known to shatter or crack and that will create a horrendous mess in your gearbox.
7. I don't know the quality of a prometheus high torque motor, but I'm sure it's decent. Thing is, there are cheaper and arguably equally performing motors such as the ZCI high torque, element high torque, or rocket high torque.
8. Sorbo may or may not do weird things to your fps.
9. I think you could just use a guarder v2 tappet plate, which is cheaper and does the same thing as the prometheus. Only thing is ime, the guarder tappet doesn't get pulled back far enough with rocket gears, so I needed a sector delay chip (even though delay chips aren't usually used for that purpose).

Disclaimer: I say these things due to experience or research. I may have given bad information, so do fact check me.
 

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And there is also a design flaw in the RetroArms shell...I would pick your platform and get parts that fit versus getting parts and hoping it will fit into your platform.
 

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I also have a question: how is your field going to enforce the 1 rps rule? Does your build have to be physically incapable of shooting faster? If not, what happens if you accidentally shoot a bit faster? The only way would be to build a gun that shoots that slow, but that's mind blowing in itself. Are you allowed to do a 1 sec count after every trigger pull (honor system)? Otherwise, you're stuck with a very slow setup. When you pull the trigger it'll sound like this: rrrrrrrr pop, when it could sound like this: rr pop. A more efficient setup would be lower ratio gears with a high torque motor, but your semi rps will end up being too high. Are you specifically choosing to pair standard (more on the high side) ratio gears with a high torque motor to be slow?
 

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Discussion Starter · #7 ·
I also have a question: how is your field going to enforce the 1 rps rule? Does your build have to be physically incapable of shooting faster? If not, what happens if you accidentally shoot a bit faster? The only way would be to build a gun that shoots that slow, but that's mind blowing in itself. Are you allowed to do a 1 sec count after every trigger pull (honor system)? Otherwise, you're stuck with a very slow setup. When you pull the trigger it'll sound like this: rrrrrrrr pop, when it could sound like this: rr pop. A more efficient setup would be lower ratio gears with a high torque motor, but your semi rps will end up being too high. Are you specifically choosing to pair standard (more on the high side) ratio gears with a high torque motor to be slow?
I'm going to reply to both of your responses in this one message, thank you for the gearbox suggestions on the pistons, tappet plate, gears, cut off lever, and other components. I liked the idea of the tripple torque gears based of the research of them being supposedly 26:43:1 for the gear ratio making them have an extreme amount of torque and not just 18:1 gear sets. Knowing that I don't need the ARL is amazing to know because that eliminates the semi locking that can happen. As for the Field Rules, it is roughly the same group of 50 to 70 people every Saturday, thus new guns are very widely noticed. With that being said, the game moderators require you to chrono a new gun after modification to ensure it meets the safety requirements. Knowing that it is a DMR they will require you to show that it is locked in semi only and is at 1 rps. This is why I am using the Gate titan due to programming of the mosfet. There is an entire program within the mosfet that you can set your rate of fire from .01s between shots, all the way to a 5 second interval between shots. So I will easily be able to achieve the 1 second interval between shots. This restriction is also only for dmr builds. This can solve the problem of long winding times of the gearbox (with correct gears) to a short sound, and will only allow the gear box to wind within the time permitted by the mosfet.
 

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Discussion Starter · #8 ·
And there is also a design flaw in the RetroArms shell...I would pick your platform and get parts that fit versus getting parts and hoping it will fit into your platform.
Thank you for letting me know about the design flaws in the Retro Arms gearbox. It is definitely a great idea to build the gearbox with parts that fit rather than hoping. However, in theory, if proper research is done, you should be able to find parts and know that they will fit, but that can only take you so far. I will definitely keep your advice in mind and ensure I get parts that fit.
 

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Thank you for letting me know about the design flaws in the Retro Arms gearbox. It is definitely a great idea to build the gearbox with parts that fit rather than hoping. However, in theory, if proper research is done, you should be able to find parts and know that they will fit, but that can only take you so far. I will definitely keep your advice in mind and ensure I get parts that fit.

This is not so easily found, applied or verified as valid from independent searches...
 

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Oh duh...I totally forgot about the gate advanced or expert package. But I would still strongly recommend lower ratio gears. Pairing high torque gears with high torque motors is very slow. If you're ok with that, cool. But I would think you would want the bb going out pretty much as soon as you pull the trigger?
 

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Discussion Starter · #11 ·
Oh duh...I totally forgot about the gate advanced or expert package. But I would still strongly recommend lower ratio gears. Pairing high torque gears with high torque motors is very slow. If you're ok with that, cool. But I would think you would want the bb going out pretty much as soon as you pull the trigger?
[/QUOTE/]
I would love for the gun to fire almost immediately after the trigger is pulled, obviously there will be a delay due to mechanics and electronic signals. I was going with the low torque gears due to the heavy spring, but what gear ratio would you reccomend. With the gears I previously selected, would I be able to ditch the high torque motor and use a regular, faster speed motor without adding strain to the motor and get the response time I want. Also, with the mosfet, I should be able to program a precocking function that allows the mosfet to wind the piston back close to the point where it is fired almost immediately when the trigger is pulled. However, it doesn't sold the long winding sound of the gearbox that you are suggesting with the low torque gears and motor
 

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Well there's 2 ways to get trigger response:
1. low ratio gears (high speed) paired with a high torque motor
2. high ratio gears (high torque) paired with a high speed motor

Option 1 is almost always going to be more reliable than option 2. Option 2 is honestly quite silly imo because high speed motors will wear themselves out faster (even with high ratio gears) than high torque motors, and especially more so with heavier springs. So to answer your question, yes you could just get a higher speed motor but I'd advise against it. I'd advise going with option 1 and picking up a pair of 13:1 rocket gears.
 

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Discussion Starter · #13 ·
Well there's 2 ways to get trigger response:
1. low ratio gears (high speed) paired with a high torque motor
2. high ratio gears (high torque) paired with a high speed motor

Option 1 is almost always going to be more reliable than option 2. Option 2 is honestly quite silly imo because high speed motors will wear themselves out faster (even with high ratio gears) than high torque motors, and especially more so with heavier springs. So to answer your question, yes you could just get a higher speed motor but I'd advise against it. I'd advise going with option 1 and picking up a pair of 13:1 rocket gears.
Would the 13:1 rocket gears with a high torque motor be able to pull back a potential m160 (could be as high as m170 but very unlikely) spring without added stress the the shell, motor, and gears)
 

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The spring will induce stress - period.

Motor and gears pulling it back will not mitigate this in any way.

And a full stroke mechbox will be very stressful on the front of the mechbox, which the V2 has a design flaw in general.
 

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Discussion Starter · #15 ·
The spring will induce stress - period.

Motor and gears pulling it back will not mitigate this in any way.
I do understand there there will always be a constant stress, but like a car going up a hill, your drop your gearing to provide more torque (less speed and more RPM) to ease the lugging of the motor and the added stress. So by increasing your torque through your gears you should help reduce some stress on gears and motor of the gearbox with a loss of speed. There is a point where you loose too much speed as mr. Potatohead had mentioned above. So if you have a 13:1 gear ratio you could induce more stress than a gear ratio of 18:1. I am not sure if different gear ratios are available to find a happy medium between speed and torque for the spring and motor used. And as mentioned, I am new to this and am only using my experiences that I have and do not know if they directly relate to an airsoft gearbox so if I'm wrong, I am more than happy to be told that I am so I can learn! Thank you Guges MK3 and Mr. Potatohead for your help in getting this figured out. I greatly appreciate it. It is helping me learn a lot. I just don't want to spend 1200+ dollars and get half of it wrong
 

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Yes 13:1 gears and a decent high torque motor will be fine. Things you can do to mitigate gearbox stress are radiusing the gearbox (only the front, back is irrelevant), installing a sorbo+neoprene pad combo, correcting AOE and the like. Threads should be pinned in the gun building and modification section.
EDIT: pairing high torque with high torque is reliable but will be disappointingly reliable, with no speed.
 

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Discussion Starter · #17 ·
Yes 13:1 gears and a decent high torque motor will be fine. Things you can do to mitigate gearbox stress are radiusing the gearbox (only the front, back is irrelevant), installing a sorbo+neoprene pad combo, correcting AOE and the like. Threads should be pinned in the gun building and modification section.
Thank you for your help. I will definitely be going that route with this build then as I do more research on components. Thank you again for your help!
 

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Keep in mind that you can get multiple views from others and that what I say isn't the absolute truth lol. Throwing this many parts together ain't gonna be easy, to be honest with you. Ask Guges and he'll tell you that "American consumerism doesn't apply here." Parts will claim compatibility but won't fit, and things will be off spec. You're almost guaranteed to run into problems, but that's just part of the process. Do keep us updated, and we'll try our best to help you.
Also I don't know much on volume matching and air shock waves and stuff like that, so hopefully those that are more knowledgable will be able to fill ya in. :D
 

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The example with the car is exemplary, but the concept isn't complete. It's not just a constant motion of pulling a heavy object up the hill in one direction. Rather its like winding up a battering ram.

It's pulling a car up the hill (against a gravity, in this case can be like a spring constant) and them letting it go and slamming said car against a wall (mechbox shell), repeatedly, until something breaks either on the inside, gear teeth or on the outside, mechbox shell.

Your performance maximum of 2.6J is well beyond the operational specs of 98% of the mechboxes on the market. I can only think of two that can handle this stress and Krytac isn't one of them.
 

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I have some experience with some of the parts you mentioned. I don't have time to read the whole thread, so others may have already mentioned these things...

Retro Arms gearboxes have some issues. Do a search here on the forum and read up.

Maxx cylinder heads have that extra buffer on the front of the head, where it meets the gearbox shell. This can actually damage the pins that hold the cylinder head in place, especially on a CNCed gearbox shell.

Cylinder looks fine. Just remember that for efficiency's sake you may want to pick the BB weight you're planning to use, and then pick your cylinder size and barrel length accordingly for good voluming. This will get you more FPS with a certain spring, and your gun will be quieter.

The others are right. 2.6J is a lot. If I were you, I would design your build to incorporate a lower stress spring, and then get a stronger spring if you really want to put in the extra work and risk, AFTER you play with the thing and get the feel of it.

My personal build uses an M130 spring, full cylinder, and 407mm barrel, and with .30g-.32g BBs, I joule creep to 1.8J, which is plenty enough for my large outdoor field.

You should look up joule creep, and how to use it to your advantage.

Instead of a sorbothane buffer, I suggest making your own out of fishtank/glass silicone. This may not be so influential in your build with 1 round per second, but sorbo pads are basically memory material. They don't instantly expand back to the same shape every time, so your air volume will be different. Silicone doesn't do this.

For a MOSFET, I recommend staying away from the TITAN for the purposes of price and ease of programming. Nothing wrong with it, and the build I'm using one in works fine with it, they're just more expensive for something that only adds diagnostic and technical data gathering features.

I recommend using a Perun V2. Cheaper, all the same practical functions, and it's way easier to program. You can adjust settings in literal seconds through trigger inputs.

Yes, use the adjustable trigger. Love those.

Don't do a metal piston. They're not really more durable than the plastic ones, and have a bunch of issues. Do a quick search here for those as well. Metal teeth are fine.

You can definitely use that hopup, but just know that it won't really be better than a decent plastic one. It's just more expensive, and aside from a couple of kinda-cool features, it'll just make you feel better, and might actually add issues. I suggest researching if the stock hop up of the platform you choose has any issues, and just use the stock one.

My best nozzle suggestion for you is to ignore the o-rings, and buy a few different kinds of nozzles, plastic and metal, to see what works best in terms of consistency and accuracy. I personally use the Maxx adjustable nozzle to find the perfect nozzle length, but frankly, Maxx nozzles have wiggle issues even on the Maxx cylinder head. Wiggle = bad. You want it to fit and seal in the same place every time.

Go with bushings instead of bearings. They're just the better choice for this kind of build. Bearings can be much harder to install, and don't do much for a DMR.

I second the high torque motor/low ratio gears suggestion. High speed motors, in my experience, heat up much faster than high torques.

The most important part of any DMR is your bucking. What are you planning to use? Do more research on your ideal bucking. I'll even go so far as to suggest you create a custom hop up nub to ensure good tuning with whatever bucking you use.

Keep us updated! I'm one of the newer peoples, and my suggestions will probably be dissected by all the others who know more, but this is the place to post what you're doing, how it works, and to have others give you new ideas.
 
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