6 replies to this topic

[Slagr]

Myself and an associate of mine have been looking into constructing a Nerf-type gun using a falling weight as opposed to elastic tension, and please trust that we have a "good" reason.

Basically, we will be dropping a 4.5 kg weight onto a plunger apparatus that will fire a racquetball from a length of PVC, probably with foam stuffing behind it to catch the air better. We're not looking for stellar performance, just as long as it fires at all, really. I'd like to use a ~10 in diameter plastic barrel for the plunger tube and construct a plunger from plastic and foam on which to attach the weight. My main concern is of course the effectiveness of the weight in forcing air through the gun at an adequate velocity.

Is this a plausible proposal?

It's worth noting that this is not my, nor my associate's first homemade nor will it remain weight-powered after the concept is proven.

[HOTH]

Sounds interesting, but most people like it better when you try it first, and post your results then.

[Slagr]

HOTH, on Feb 24 2010, 10:49 PM, said:

Sounds interesting, but most people like it better when you try it first, and post your results then.

True, but I thought it would be beneficial to find some helpful advice prior to construction.

[catmods]

Sounds kind of like a Trebuchet. Make it out of wood, give it about 20 pounds for the weight, use a cut up liter soda bottle as a cup, and you should be able to launch 30 darts 150 feet, effectively creating an artillary weapon. Please, inform us how it turns out. Otherwise, get some pictures up soon, as concept threads are generally looked down upon.

[CA13]

catmods, on Feb 24 2010, 10:57 PM, said:

Sounds kind of like a Trebuchet. Make it out of wood, give it about 20 pounds for the weight, use a cut up liter soda bottle as a cup, and you should be able to launch 30 darts 150 feet, effectively creating an artillary weapon. Please, inform us how it turns out. Otherwise, get some pictures up soon, as concept threads are generally looked down upon.

What the fuck? Are any of you capable of designing this? Trebuchets are modified levers, and I really don't think that's what he wants. If you would want some sort of "weight operated cannon", try taking a trebuchet and on the sling end attach a pivoting piston. The piston would be inserted into a plunger tube and be forced down as the weight drops and the pivot moves across the linkage. It wouldn't be worth it, but you and your "associate" (what the fuck could that mean?) probably wouldhave a great time, having associates and rapid insertion and all.

[Zorns Lemma]

CA13, on Feb 24 2010, 11:26 PM, said:

stuff

Try not to be so adamant when you have no idea what you're talking about.

Slagr, I take it you want to build an oversized push-pull gun that is powered by gravity rather than your arm. This is easily feasible. The only comment I have is that a 10" diameter pipe is probably overkill. If you have a taller but thinner pipe, air volume is the same, but you will build up more acceleration through gravity and will get better results anyways.
This is what a 4" diameter pipe does, powered by hand:

Writeup on the plunger mechanism:
http://www.nerfrevol...c.php?f=9&t=870

[KaneTheMediocre]

Zorn's Lemma, on Feb 24 2010, 09:46 PM, said:

CA13, on Feb 24 2010, 11:26 PM, said:

stuff

Try not to be so adamant when you have no idea what you're talking about.

Slagr, I take it you want to build an oversized push-pull gun that is powered by gravity rather than your arm. This is easily feasible. The only comment I have is that a 10" diameter pipe is probably overkill. If you have a taller but thinner pipe, air volume is the same, but you will build up more acceleration through gravity and will get better results anyways.
This is what a 4" diameter pipe does, powered by hand:

Writeup on the plunger mechanism:
http://www.nerfrevol...c.php?f=9&t=870

Mostly what Zorn said, but I just got on the Haven about 10 minutes ago, and posted the same writeup here:

http://nerfhaven.com...showtopic=18962

My main concern is your weight--I'd want a bit more than 4.5 Kg, unless it's being dropped from great height. Stiction may partly negate the drop height anyways. As for pipe size, I agree that 10" is probably overkill, but if possible go with at least 5-6". And it's not like 10" is a BAD idea, in fact I'd like to see it. Although a tall thin pipe can provide the same airflow as a short fat one, your velocity is going to be limited by gravity, so I wouldn't go too thin or too tall. Also, since a tall cylinder will take longer to compress, the projectile might leave the barrel at suboptimal speed well before the plunger has reached the bottom, wasting whatever air remains in the cylinder.