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HEC 3 Half Pump

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#1 atomatron

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Posted 01 February 2012 - 11:09 PM

This is a continuation of my Homemade ERTL Catch (HEC) series. HEC 3 is an attempt to make a light and effective pump action blaster for as cheap as possible. The catch and handle are exactly the same as the blaster in my other thread(which I will refer to as HEC 1 as it was the first blaster of this series).


Materials
1x foot of 1 1/4" PVC
2x 1 1/4" Couplers
2x 1" to 1/2" PVC Bushings
1x foot of 1/2" PVC
1x 1/2" PVC elbow
1x 4" of 1/2" PVC
1x 3/4" PVC endcap
1/2x (half of) K25
1x 5" of 1/2" CPVC
1x 1/2" CPVC endcap
1x 1" OD steel washer
1x 1 1/2" OD rubber washer
1x 1 1/4" OD rubber washer
1x 1 1/4" OD steel washer
Assorted 6-32 Screws
Etape (or vinyl tape)
Polycarbonate (1/4" and greater thickness)

...or at least that's what I used. My most prevalent intention is for others to build off of these designs and make something better.


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Here's the blaster in all it's partially disassembled glory. The stock can be held in place by a screw or removed entirely, The barrel/hopper combo is one suited to the blasters lower volume but high rate of fire.

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The top is internals, the bottom is the pump slide which consists of the two 1 1/4" couplers sanded out and solvent welded together; one cut down to make room for the catch/handle. It has 4" of draw.

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And a slot in the top. It is 4" long, starts 5" from the front and is 1/4" wide

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The plunger rod features a basic rubber washer seal. Using all the washers, the CPVC segment, the 3/4" PVC endcap, Etape (I used a piece of 5/8" ID tubing to decrease the amount of tape needed) and a few bolts.

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The 1/4" bolt segment I put on the pump slide ate into the catchface, I have since ground the threads down

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The pump handle at the end of the priming stroke.

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Here's the HEC 1, 2(Incomplete) and 3, just as a sneak peak I guess.


I apologize for the post-writeup writeup, HEC 2 will have a full, detailed one.



Also for the sake of discussion it can hit ~100' with the half K25; that's about 15 feet less than the HEC 1 which has a full K26 (hits ~120). Our blasters are basically more powerful than they need to be; half the spring still gets 83% of the range.

Edited by atomatron, 01 February 2012 - 11:21 PM.

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#2 andtheherois

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Posted 01 February 2012 - 11:28 PM

So it pushes and catches on the same piece. That's very awesome. I love how short it is. Great works with the HEC!
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#3 Daniel Beaver

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Posted 02 February 2012 - 09:24 AM

The Rainbow clan makes the best guns.

Also for the sake of discussion it can hit ~100' with the half K25; that's about 15 feet less than the HEC 1 which has a full K26 (hits ~120). Our blasters are basically more powerful than they need to be; half the spring still gets 83% of the range.

Yup. The air output is still relatively gigantic, and a half-spring will maintain the same draw force as a full-sized spring.
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#4 Jilliop

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Posted 02 February 2012 - 04:46 PM

And if I'm seeing this right you don't need a ramp for the catch; you are just using an endcap? Just found my new catch design! Great job!
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#5 atomatron

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Posted 03 February 2012 - 12:54 AM

So it pushes and catches on the same piece. That's very awesome. I love how short it is. Great works with the HEC!

Yes, it is awesome.

The Rainbow clan makes the best guns.

We do, that's all there is to say on the matter.

And if I'm seeing this right you don't need a ramp for the catch; you are just using an endcap? Just found my new catch design! Great job!

Look a bit more closely at my other thread. The ramp is on the catch arm of the trigger, so yes; there is a ramp but not like a SNAP. Thanks.
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#6 BOSS9

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Posted 04 February 2012 - 08:05 PM

I keep forgetting to give you props for this blaster and the HEC system. You already know how awesome this is.
I'm super stoked for the REV2 writeup, and you should definitely bring one of these to a war sometime.
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#7 Carbon

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Posted 04 February 2012 - 10:13 PM

Not sure how I missed seeing your HEC posts. Nicely done! HEC2 looks awesome, looking forward to seeing that writeup.

The ramp is on the catch arm of the trigger, so yes; there is a ramp but not like a SNAP.

I would think the most forgiving way to design it would be to use a rounded endcap for the catchface (Home Depot, as opposed to Menards). No beveling needed, and would make the trigger ramp less critical.

Edited by Carbon, 04 February 2012 - 10:14 PM.

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#8 atomatron

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Posted 06 February 2012 - 05:59 PM

I keep forgetting to give you props for this blaster and the HEC system. You already know how awesome this is.
I'm super stoked for the REV2 writeup, and you should definitely bring one of these to a war sometime.

I'll definitely bring these to the next war

Not sure how I missed seeing your HEC posts. Nicely done! HEC2 looks awesome, looking forward to seeing that writeup.


I would think the most forgiving way to design it would be to use a rounded endcap for the catchface (Home Depot, as opposed to Menards). No beveling needed, and would make the trigger ramp less critical.

By ramp I mean the curved bit on the catch arm, I've never considered it a point of interest or concern.
Posted Image


Expect HEC 2 in a couple weeks.
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#9 ChaosPropel

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Posted 19 February 2012 - 04:33 PM

Dunno if this warrants a necro, admins please let me know if it doesn't.

I am currently building a pullback version of this, and so far I have this much done:
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However, I am having trouble with the trigger. I followed measurements Atomatron gave me, and have the spring where he has it, and it's a rather beefy compression spring too. However, the blaster/plunger rod will STILL not stay caught.

Any ideas? My next idea would be to just add rubber bands/extension springs, since stronger springs would be impossible to put in, at least for me.

Thanks.
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#10 atomatron

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Posted 20 February 2012 - 04:03 AM

Currently, I'm trying to better understand and perfect the mechanism via clear plungertube but I actually need to get that..
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#11 shardbearer

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Posted 20 February 2012 - 08:27 AM

To make it catch better, make the trigger closer to the plunger tube, intrude less into the plunger tube, and make it longer from the pivot to the catch surface (front-back). Making the trigger longer from the pivot to your finger will result in an easier pull.

Leverage. How does it work?
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#12 atomatron

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Posted 20 February 2012 - 07:18 PM

My hunch is that there is something about having the catch arm and endcap edge meeting at 90* to the pivot point that improves the catching. As the HEC 1 suffers absolutely no deficiencies while exhibiting this feature.

Edited by atomatron, 20 February 2012 - 07:18 PM.

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