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I need a little help designing an ass...

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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I need a little help designing an ass...

Unread postAuthor: Gun Freak » Mon Jun 14, 2010 9:54 pm

ASS- AirSoft Sniper :D

I want to build a cheap simple and fun little springer for airsoft wars. I know this doesn't seem practical, but with careful designing and construction it should be cool. So far I have only designed the piston. It has one floating o-ring in between 2 washers. The setup for the piston is something like this:
Washer almost ID of pipe, washer a bit smaller for o-ring to slip over, washer almost ID of pipe, bolt head.
That is the front of the piston.
The back will be something like this:
Lock nut, washer almost ID of pipe, lock nut.
The sear (I think thats what its called, the part that holds the piston back), will catch on the washer.
The spring is behind all of this. I plan to house it all in 3/4" sch 40 PVC. There is about maybe 3 inches between the front setup abd the back setup of the piston.
It will look like the picture attached.
The slice down the middle is for the cocking mech, which will pull it back into place and then slide back forward. It will be bolt action. I am stuck at how to house the bolt and what to use for it... I can't think of anything that would fit though the bolt and still be strong... any thoughts welcome.

EDIT, after studying bolt snipers animation, I want to put the bolt in 3/4 sch 40 and put that inside thin walled 1" to make the bolt thingy. Very similar to bolt snipers design.
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Unread postAuthor: deathbyDWV » Mon Jun 14, 2010 10:37 pm

Oh haha. I get it. You said ASS. But (hehe but(t)) you really meant it as an acronym... :roll: OMG you are so funny!!!

Umm well, I don't have much to say. This is disappointing...
Oh wait.

Why is there a washer on the back? It just seems like it'd make it heavier. Why can't the spring go all the way up the the back of the washer section?

Also with that much metal, I don't see how any good power could come out of it. Just too heavy... :(
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Unread postAuthor: Gun Freak » Mon Jun 14, 2010 10:50 pm

It's nylon....
the back washer is for the trigger to catch and release on.
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Unread postAuthor: Technician1002 » Mon Jun 14, 2010 11:01 pm

deathbyDWV wrote:Also with that much metal, I don't see how any good power could come out of it. Just too heavy... :(


It is a springer. Mass is required for it to work. This piston is not a valve. It is a mass slammed into an air pocket. The then compressed air ejects the projectile.
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Unread postAuthor: Gun Freak » Mon Jun 14, 2010 11:02 pm

So tech, would it be better to have it all metal, or nylon? Nylon would move way faster and compress air faster... but would the extra mass actually help it? Two of the washers are metal, the bolt itself will be nylon unless the weight would help.
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Unread postAuthor: Technician1002 » Mon Jun 14, 2010 11:18 pm

The math for the kinetics of a springer is beyond my skills. The best match for piston mass, air compression, and projectile ejection is a complex equation. If the mass is too small the compression is faster than the projectile (takes less time) takes to accelerate, then the piston will bounce on the air and rebound. This returns energy to the piston instead of transferring it to the projectile. If it is too heavy, it moves too slow and the projectile ejects before the piston momentum is transferred. Again the piston has energy that is not transferred. At the proper balance, the piston comes to a stop (no bumper needed) and does not recoil.

The easiest way to do a guesstimate on mass is to take your piston acceleration and distance and figure the deceleration due to compression of air ahead of the piston. The deceleration time should equal the acceleration time of the projectile accelerating at the same time the piston is decelerating. Due to the diameter difference and mass difference (where it gets complicated) the compressed air volume will transfer the kinetic energy of the piston to the lighter smaller projectile, but for the same KE, the projectile will travel faster. The air acts like a springy lever in between changing large slower mass into faster lighter mass.

Someone advanced in physics may be able to help with the sizes and masses so the piston comes to a stop with no KE when the projectile finishes taking on all available KE from the gas and ejects.

A large scale example of how it works is this youtube video. Note the bowling ball does not hit the bottom hard and does not bounce back on the air.
[youtube]http://www.youtube.com/watch?v=US6keYG9HAw[/youtube]
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Last edited by Technician1002 on Tue Jun 15, 2010 3:12 am, edited 1 time in total.
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Unread postAuthor: Gun Freak » Mon Jun 14, 2010 11:52 pm

Thank you very much Tech for your help, and the video. It helped support what you were saying. I might experiment with a few different weights to get the best one.
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Re: I need a little help designing an ass...

Unread postAuthor: jackssmirkingrevenge » Tue Jun 15, 2010 12:54 am

Gun Freak wrote:I want to build a cheap simple and fun little springer for airsoft wars. I know this doesn't seem practical, but with careful designing and construction it should be cool.


Careful designing and construction for something cheap, simple and fun does sound impractical.

I think you're much better off buying a cheap-o springer like this one and upgrading the existing internals, say heavier piston, stronger spring, stronger trigger mechanism to support it, decent sights etc.
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Re: I need a little help designing an ass...

Unread postAuthor: Technician1002 » Tue Jun 15, 2010 1:09 am

jackssmirkingrevenge wrote:say heavier piston, stronger spring, stronger trigger mechanism to support it, decent sights etc.


Bigger spring and heavier piston will need smaller volume between the springer and projectile, otherwise instead of getting higher pressure, you get smashed piston. These are engineered. Think about what else has to change for any change made and why.
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Re: I need a little help designing an ass...

Unread postAuthor: Techie » Tue Jun 15, 2010 6:10 pm

jackssmirkingrevenge wrote:
Gun Freak wrote:I want to build a cheap simple and fun little springer for airsoft wars. I know this doesn't seem practical, but with careful designing and construction it should be cool.


Careful designing and construction for something cheap, simple and fun does sound impractical.

I think you're much better off buying a cheap-o springer like this one and upgrading the existing internals, say heavier piston, stronger spring, stronger trigger mechanism to support it, decent sights etc.


Like Gun, I'm also attempting to make an air soft gun...
We talked a lot last night, and one thing we have in common is our parents won't let us buy one.

I know mine (mostly because of the lack of materials) will be VERY simple. Mine is going to be pneumatic though, without machining or casting parts I don't think you can make a reliable springer.
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[Techie] 12:04 am: heck why dont i just light a fire under random cars
[Techie] 12:04 am: that aughta be fun while it lasts
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Unread postAuthor: kydavies » Tue Jun 15, 2010 6:32 pm

techie, i feel your pain...
i to am very limited to materials, machining and money.

for a cylinder use a syringe cause it comes with its own air tight piston/plunger


edit:i seem to get my hands on what ever i can find ex)yesterday i got 11 springs off of those old school wall mounted metal desk lamps that retract
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mikemurph wrote:yea, the ammo has been changed to a more aero dynamic projectile. it consists of the back half of a dart, and a hot glue ball
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Unread postAuthor: Gun Freak » Tue Jun 15, 2010 8:12 pm

The syringe is a good idea, I might try that, but I was planning to use a floating o-ring and pvc pipe... If I can get my hands on one, I will experiment with it.
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Unread postAuthor: Techie » Tue Jun 15, 2010 9:05 pm

Your going to need a lot of lubricant if you use a syringe, they airtight seal isn't just airtight.
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Unread postAuthor: Gun Freak » Tue Jun 15, 2010 9:13 pm

Yeah it is tought to push, thats why I wanted floating o-ring seal. They have very little friction. Also syringes are very airtight, I once plugged the spout with my finger then pushed it and it didn't leak at all, it retained the pressure...
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Unread postAuthor: kydavies » Tue Jun 15, 2010 10:16 pm

ah the reason why its so hard to push is because of the small porting hole in the front (make it bigger) and lube it up and it should be like 10x esier

edit: because a syringe is so airtight your plunger will be extremely efficent
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