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Homemade Smdtg Trigger

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#26 Zorns Lemma

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Posted 16 February 2009 - 03:43 PM

Rather than opening up valves, you're just letting air escape out the front to create backpressure?

Interesting.


That's how the hornet's blast triggers work.


With a blast button you don't have to worry about triggering each chamber sequentially, since the intent is for simultaneity.
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#27 venom213

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Posted 16 February 2009 - 05:25 PM

Okay, I tested the gun with the sealed tubing. The sealing helped a lot, but there were still some leaks. It turned out that the sealer wasn't sealing as well as I thought. I was able to get it to shoot a few times though, and it shot the darts pretty hard. Other times it would only shoot one of the darts very weakly. Then after a while the brass broke off the CPVC. But, that was also good because now I can add the barbed connectors instead. Here is what I think went wrong:
-Brass didn't bond well to the CPVC
-I used Loctite superglue to bond the brass to the CPVC, with plumbers goop over that. I've found in past projects that Loctite does not bond brass to plastic very well, and plumbers goop does not provide enough strength to compensate for it.
-The sealer shifts around in the CPVC, causing it not to seal
-The washer sandwich was tightened either too much, or too little

Here are some solutions:
-Replace the brass with barbed connectors for a better bond (plastic on plastic instead of brass on plastic)
-Use a stronger adhesive
-Add more washers or retaining objects to make sure the sealer can't shift around. The endcap I talked about adding to the front would serve this purpose.
-If the retaining objects are added, fine tuning the washer sandwich should be much easier.

I didn't post this before, so I figured I should now. I actually had two designs for the sealer. This was the other one:

Posted Image

It was to use a thicker (1/4") screw and an O-ring that fit over the screw, and in CPVC. I tested it earlier with the glued together trigger, and it seemed to work quite well actually. I think it is most likely because the nuts around the O-ring fit very well in the CPVC, and add more length to that area which prevents it from shifting around as much as the other design. I'm going to explore both designs some more and see which is best.
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#28 Zorns Lemma

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Posted 16 February 2009 - 06:28 PM

One problem with this design is that you can't shoot 1 tank and then pump it as trying to do so will fire the 2nd.
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"In short, the same knowledge that underlies the ability to produce correct judgement is also the knowledge that underlies the ability to recognize correct judgement. To lack the former is to be deficient in the latter."
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#29 Lt Stefan

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Posted 16 February 2009 - 06:38 PM

When you pressurize the tank how does the "sealer" stay in? Wouldn't the pressure push it out? I want to use a design similar to this only with PVC and that's a problem I see happening.
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#30 Lt Stefan

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Posted 16 February 2009 - 08:58 PM

When you pressurize the tank how does the "sealer" stay in? Wouldn't the pressure push it out? I want to use a design similar to this only with PVC and that's a problem I see happening.


Yeah, you have to hold it in somehow. I was using metal instead of CPVC so I just crimped part of the end of the tube.


So if you pressurize it to 4o psi, and say the head of the piston was 1 sq. in., you'd need a 40lb resistance spring?
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#31 venom213

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Posted 16 February 2009 - 09:38 PM

I would just hold it in with my thumb, which proved to be difficult. As the pressure got higher, I would have to apply more pressure with my thumb, and it was hard to keep it equal. For V2, I'm going to put a cap with a hole drilled in it on the end. Another problem was that I would accidentally shift the sealer around which would cause it to not seal. V2 should fix, or at least make all these problems less significant.

JSB: That's a good point about check valves. I may experiment with check valves on V3 of V4 of this, but V2 will only be triggering two hornet tanks, like V1, so that aspect will remain the same.
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#32 Zorns Lemma

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Posted 17 February 2009 - 03:03 AM

Standard check valves just inserted between the tank and the trigger would defeat the purpose of a back-pressure system. You could rig up 3 check valves between the pump and the trigger, each on a branch to a different segment of the trigger, but this system would be more akin to having 3 separate triggers rigged together than 1 trigger that operates 3 tanks.

Edit:
Actually, by cutting up a spring-loaded ball check valve and mounting it on thinwall CPVC, you can almost completely recreate the stock trigger.

Edited by Zorn's Lemma, 17 February 2009 - 04:03 AM.

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"In short, the same knowledge that underlies the ability to produce correct judgement is also the knowledge that underlies the ability to recognize correct judgement. To lack the former is to be deficient in the latter."
Kruger and Dunning (1999)

#33 Anson at HK

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Posted 20 February 2009 - 11:11 PM

Wow nice. We can save money with this.

Edited by Anson at HK, 21 February 2009 - 12:28 AM.

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#34 Quilan Fett

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Posted 21 February 2009 - 02:39 PM

Standard check valves just inserted between the tank and the trigger would defeat the purpose of a back-pressure system. You could rig up 3 check valves between the pump and the trigger, each on a branch to a different segment of the trigger, but this system would be more akin to having 3 separate triggers rigged together than 1 trigger that operates 3 tanks.

Edit:
Actually, by cutting up a spring-loaded ball check valve and mounting it on thinwall CPVC, you can almost completely recreate the stock trigger.

I cut open a Big Salvo trigger last night. There is a check valve between the trigger and the tubing and each tank. Each one has a little nub sticking into the trigger that opens it. When the moving trigger peice slides through, it opens each valve separately.
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This guy can see the future!

QUOTE(pokemaster @ Mar 3 2009, 04:18 PM) View Post

hasbro in a nerf war!!!!! dude the will cancel it and confinscate are guns

#35 balisticjoe

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Posted 21 February 2009 - 09:33 PM

When you pressurize the tank how does the "sealer" stay in? Wouldn't the pressure push it out? I want to use a design similar to this only with PVC and that's a problem I see happening.


Hopefully this will help. I have been trying to do this for a while now, it's going to take more time. Now my focus is mostly on making the barrels out of PVC. Imagine-being able to put numerous barrels on any gun. A nerfer's paradise.
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#36 DJ Mashbot

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Posted 21 February 2009 - 09:59 PM

Now my focus is mostly on making the barrels out of PVC. Imagine-being able to put numerous barrels on any gun. A nerfer's paradise.


If you're referring to the Salvo tanks as barrels (I'm assuming, correct me if I'm wrong), you may want to check out imaseoulman's work.
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QUOTE(dizzyduck @ Apr 1 2009, 09:14 PM) View Post

Forget about ranges; range means nothing if your blaster is a giant rattle after three shots.

#37 NerfCrazy

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Posted 21 February 2009 - 11:37 PM

If you get this to work well that would be nice but you never made that home made 2k tank work. :(
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#38 umpshaplapa

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Posted 23 February 2009 - 10:42 PM

Can someone please explain how these types of triggers work? I don't get where the tank is. It looks like the take is just the back part of the trigger.
I'm refering to the horntet/salvo/SMDTG.
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QUOTE(Talio @ Jun 29 2009, 01:50 PM) View Post

i got a black belt in noob banning in 2004.



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