12 replies to this topic

[Hammy]

Can anyone tell me what the volume displacement in cc, of a night finder plunger is.

I need to know if it is larger than 38 cc. 50 cc and above would be good.

It is in consideration for a Brass Breech on a reverse plunger Nerf gun.

[lech]

Can anyone tell me what the volume displacement in cc, of a night finder plunger is.

I need to know if it is larger than 38 cc. 50 cc and above would be good.

It is in consideration for a Brass Breech on a reverse plunger Nerf gun.

Around 20CC according to my calculations.

I used this site: http://www.online-ca...indervolume.php and measured the plunger tube to have an approximate radius of 12mm, and 44.5 MM.(1.75 inches) of height (draw) - I read this figure in the NIC spring database thread

You would need to almost double the draw length to get in the 38-50cc range. Or increase the radius by approx 5mm

Regards,
Lech

Edited by lech, 30 January 2012 - 05:19 PM.

[zx532]

You could double check these measurements simply by sealing one end and filling it with water. Then measure how much water you used.

[lech]

You could double check these measurements simply by sealing one end and filling it with water. Then measure how much water you used.

Well you would have to fill it to the exact point that the plungerhead will draw to which would require measuring the draw anyway.. pointless.

[zx532]

Well you would have to fill it to the exact point that the plungerhead will draw to which would require measuring the draw anyway.. pointless.

Didn't think of that, good point.

Edited by zx532, 30 January 2012 - 08:43 PM.

[Hammy]

I am on a business trip, so far away from all my things, and I cannot make these measurements, this is why I asked the forum.

To measure the air-displacement,

Measure the diameter of the Plunger in cm, D
Measure the draw length (the thing you pull back) in cm, L

then D*D*L*3.142/4 = air displacement in cc

The reason I want to know the air displacement, is that I want to BB a reverse plunger blaster, and am wondering if the NF plunger could be a used as a donor for this project.
For this project to work, the air-displacement needs to be in the order of 50 cc, which is the volume of the brass pipes that will be attached.

1.25 x 1.25 x 38 x 3.142 / 4 ~= 47 cc

The 1.25cm is the diameeter of a 9/16 Brass pipe which will be the barrel, and the barrel is 30 cm long
And an additional 8cm of 19/32 pipe is required for the CLIP area. so 38 cm.
I assume that on average the diameter of these pipes is about 1.25 cm.

Edited by Hammy, 01 February 2012 - 06:21 AM.

[lech]

Thanks for the lesson. If you read my post you will find that I have already given you the relevant measurements and the answer.

Why do people think pouring water into guns is easier than basic maths ?

[lech]

Because it is.
Doesn't even require a screwdriver.

Haha yeah fair enough. Although as you mentioned it requires the gun to be completely free of leaks.

[Hammy]

20cc ain't very much
I need to think of another solution, but thanks annyway

[Blue]

The idea that you need a certain volume of air for whatever brass pipes you are using is a flawed idea to begin with.

[nutterbutter]

By removing some internal parts of the shell, you can increase the draw by sliding the plunger tube forward to the back of the part of the shell that wraps the barrel. It won't be enough for what you're looking for, but I felt it was worth mentioning.

[Hammy]

The idea that you need a certain volume of air for whatever brass pipes you are using is a flawed idea to begin with.

Then I need to fabricate something else.

Edited by Hammy, 03 February 2012 - 04:42 AM.

[Blue]

Then I need to fabricate something else.

I didn't say it wouldn't work, I'm just saying that you can't use that kind of math. Whatever springs you use make a difference and I'm sure there are other factors

Somewhat related...
If you want to look at math type stuff look at DOOM's blog: http://btrettel.nerfers.com/