dskippy

Hello everyone, and in particular Doom (btrettel)

 

I'm interested in making a pneumatic semi-auto similar to Doom's FANG. I've created a 3D printed part that mates with the standard Nerf-band clip that I'm pretty happen with. I just need to figure out which air cylinder I'll be using to feed the darts through.

 

I'm hoping to get exact specs or part numbers on the air cylinder that was used on FANG upgrades. I've done some reading on the original FANG post here.

 

http://nerfhaven.com...un-prototype-1/

 

It was found in the parts bin so he didn't have a part number. He also said this: 

 

After some discussion at Spudfiles, I've already decided on one major change from prototype 1 to 2. I used a spring-return air cylinder here. The air cylinder seems to be designed to move the rod at once rather than gradually, so the spring is prestressed. To keep the force increase small, the spring doesn't travel much and has a low spring constant. And to keep the force sufficiently high to return, the spring must be rather long. All that combines to make a long air cylinder. My cylinder was about 8 or 9 inches long when it only had a 4 inch stroke.

The solution is to use a dual action air cylinder and make one side contain compressed air, with a small air chamber attached to the opening. This will still allow the spring to return all at once, but the energy can be stored in a dimension other than length.

 

So simply put, what have people had the most success with? The task is pretty simple but buying several air cylinders and using trial and error could be pretty expensive.

 

Based on my measurements and Doom's being 4" I'm tentatively looking at the smallest and cheapest McMaster-Carr air cylinder with a 4" stroke. 6498K114 with a or 6498K516 which is 3/4" longer.

 

Does anyone have any opinions on these? Does anyone have any experience with others that they recommend or would suggest avoiding? Does anyone use regulators to restrict airflow to slow down the movement of the cylinder? I've considered doing that but I haven't had my hands on one yet so I don't know if the speed will be too fast anyway.

 

Thanks for the help. One I get enough into on this thread to make a decision I'll put together a test and get my 3D printed part and McMaster-Carr parts list up here on Nerf Haven. 

Hey everyone,

I just recently finished a pretty standard Rainbow with a 1-1/4" PVC plunger tube, [k26] spring, 6" of draw, and 11" CPVC barrel. I'm getting about 110 feet on elite darts with it but they are rather inaccurate and fishtail a lot. I've been told that this is a limitation of the stock darts that I'm up against. For the time being I'm not interested in making my own darts and I'd like to stick to the stock darts. I'm wondering if anyone knows of a configuration that will give me good performance but not over power the darts.

I'm considering a Rainbow Pistol with 1-1/4" plunger tube and half of a [k26] spring but I'm not really sure since I haven't tried it.

I'm also interested in what configuration folks are using for darts with larger heads, like the suction cup darts or the velcro taggers. I'm interested in making a front loader for these, probably a pistol-sized gun, and I'm wondering what kind of air volumes and barrel tightness people are using for these as well.

Thanks,
-mike

Hey everyone,

I am having some trouble making a decent barrel for my new rainbow with a full [k26] inside a 1-1/4" pvc plunger tube using a skirt seal.

I have read a lot of the posts and tried to follow the conventional wisdom of cpvc and brass but it's not working.

I made one barrel, very standard, of 11" of 1/2" cpvc and hammered it into pvc that I drilled out. I cannot push my darts into the back in at all a reasonable amount of time. I reamed out the back to try to help loading but still it's very very tight. Firing actually works okay once it's I'm there but it fish tails.

I then tried 17/32" brass inside 9/16" brass inside pvc. this is okay. Not as tight and I can load it. this barrel however fish tails like mad. I mean our banks off at right angles and his the ceiling. sometimes I get a really long strait shot. mostly fish tailing.

my brand new, first rainbow is far from perfect too. the Aral it's weak and needs to be corrected but even a is seems like way to much power for my barrels.

I tried putting 4 inches of pvc with no brass at the end of my barrel made of brass to give it more length, telescoping, just to straighten it out but no luck.

I know a lot of the write ups here are for home made darts and they fly much better. I really need to use elites though since I play in a setting with shared darts and they are our standard. is anything going to work?

Are homemades just too much power for stock darts?

- Mike

Hey everyone,

I just made my first homemade spring-loaded gun (my second homemade). It's a Rainbow. First I'd just like to say thanks to this community for inspiring and helping me with all the great tutorials.

Now on to the issue. The seal is not perfect. When I hold my hand over the front of the gun and fire, air clearly is leaking back out of the holes in the back of the gun, so it's slipping past the plunger when compressed. It's not terrible, it does compress air and it doesn't dry fire when my hand is over it, but I want to make the seal perfect so that the plunger stops dead like I have seen in so many of your videos.

I'm open to any suggestions or descriptions of any other things people have done that has worked. I am hoping that this thread can become a discussion of all the ways to make a really good seal and debug an imperfect one. Mostly, though, I'm hoping to figure out how to fix my own.

My current setup is using a 3D printed plunger head along with a skirt seal (aka shaft seal) from McMaster-Carr and a fender washer to hold the seal on the front. Then I used plenty of silicon grease to lube it up. I put the plunger head up on Thingiverse incase anyone wants to duplicate my design. I'll be updating it based on feedback from this thread.

Plunger head: http://www.thingiver...om/thing:173486
Shaft Seal: http://www.mcmaster....9562k46/=p5bvgg
Fender washer and silicon grease from the hardware store.

I suspect that in order to improve my seal, I would need to increase the diameter of the cylinder that the seal wraps around. This would cause the seal to stretch to fit and press against the inside to the PVC a little harder.

For those of you using the same McMaster-Carr stretch-to-fit shaft seal, what is the exact diameter of the piece your seal's inner diameter is fit around? Mine is 0.894 inches, at the moment. McMaster-Carr suggests that this is for a shaft with diameter 0.95"-1.07". In the Rainbow-Pump writeup that I followed for this design, he used polyester tube that is 7/8" in diameter. This is 0.875. Unless polyester 7/8" tube is actually bigger than 7/8". I am not sure if his seal is much better than mine though but I suspect it is.

Anyone have any tips? Should I just keep incrementing by 100th's of an and print this plunger head again? Can anyone give me the outer diameter of your plunger heads for use with a skirt seal? Is is possible that using a polycarbonate plunger tube is better because the insides are precisely measured and I wouldn't have to worry about deviations in the plunger tube?

Thanks for all the help,
-mike

I have been reading the barrels and darts form for a while and I have been having a hard time figuring out what I should do to make an optimal barrel for my compressed air gun. The gun is a typical 3/4" sprinkler valve gun. I have made two barrels and two chambers for it. The first a 1' long barrel with a small chamber 4x the volume and the second is a 3' long barrel again with a chamber 4x the size. I am compressing my air to about 30 psi, 60psi, and 120psi. Both barrels are 9/16" brass nested inside 1/2" schedule 40 PVC.

With the 1' barrel I get decent shots, 150' at max psi. With the 3' barrel I get varying behavior. Sometimes 200', sometimes the dart stays in the barrel bunched up, sometimes the tip blows off in the barrel and the foam flops out, sometimes the dart dove tails, sometimes I get a weakish shot off target (probably a minor dove tail).

I am wondering if people have an recommendations. I am using standard Nerf Stefans bought off the shelves and I'd like to stick to that ammo.

I have considered making a telescoping barrel based on what I have read. The disadvantage of a telescoping barrel is that pressure cannot build up behind the dart long enough if you make the tight-fit portion too small. However, if your reading comprehension is good you'll remember that I'm using a compressed air gun. So perhaps telescoping is a good way to go? Perhaps even just a loose-fit barrel. I could do schedule 80, schedule 40 even, I have not tried CPVC, that seems way too tight. Has anyone experimented with compressed air cannon barrels? Basically, I want to make the dart go as far as possible. This is not for a war so I don't care if it would hurt some one if I hit them. I have other guns for actually shooting humans. This is just for show.

Thanks a bunch,
-mike