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Bolt Action Blaster Stress Breakage Issue


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#1 Phree Agent

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Posted 11 May 2013 - 06:14 PM

Bolt Action Woes

I have been working on this bolt-action blaster project of mine for quite some time now, and have a working prototype version completed. Sadly, one of the pieces (for this thread I will refer to it as the cocking slide) is not strong enough to withstand the leverage/stress it is required to hold. This blaster is loosely designed around the blaster found here: , by Wes.

I would really prefer to use a more Bolt action type priming mech in my blaster as opposed to his (but they function very similarly). Here is my video showing the functionality of my blaster, as well as how the piece in question primes the blaster. (Sorry for the crappy video. Hopefully, even through the painfully pixel-y picture you can see how this thing functions)

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For those who might be better reading than watching, the bolt action handle is lifted and is pulled backwards on the blaster. This handle is connected to the “cocking slide” that pulls the entire plunger rod back into the catch. At this point, the spring is not compressed. The plunger rod is caught (by the rainbow catch), and the cocking slide is then returned to it’s original position thus priming the spring against the plunger head. The trigger is pulled, and the plunger rod shoots forward. Return to step one.

The “cocking slide” currently is made of a ¾ to 1/2 reducer that has been reamed out so that my ½ in CPVC plunger rod can slide through it.

My question to everyone with homemade knowledge is: Is there a way to attach the bolt action handle to this “cocking slide” piece so that it can be strong enough to prime a [k26] in the levering position it is in? I have tried Goop, Super Glue, and PVC cement. Any help or suggestions would be great.

(This blaster isn’t finished yet obviously. Still needs some cosmetic work, but worked for a while before the cocking slide to bolt action handle was broken)

Specs: 1-1/4 PT, ~7 inches of draw, full [k26] inside. Has a hardware store cup seal on a cpvc PR. It’s a monster to prime, but hopefully with proper material strength it will become easier. Ranges easily break 100.
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#2 andtheherois

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Posted 11 May 2013 - 06:46 PM

Drill a 1/2" hole through the cpvc rod and stick nylon/delrin./alum/ whatever into it, then sheth it wih a 1/2ID/5/8OD tube to coupler onto the cpvc handle. That may hold it. You can also fill in that space with putty. Lube up the cpvc and putty around it. The lube will keep the putty from sticking and you'll hve something solid to support the handle.
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#3 Phree Agent

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Posted 11 May 2013 - 08:52 PM

Drill a 1/2" hole through the cpvc rod and stick nylon/delrin./alum/ whatever into it, then sheth it wih a 1/2ID/5/8OD tube to coupler onto the cpvc handle. That may hold it. You can also fill in that space with putty. Lube up the cpvc and putty around it. The lube will keep the putty from sticking and you'll hve something solid to support the handle.


I am not sure I understand your first suggestion, but I would rather not drill any holes into the PR. I would have to do a slotted rod, and that is a pain as you know. The putty idea sounds good, I just don't have a lot of room to work with between the PR and the "cocking slide" to add a substantial depth of putty. I will give it a shot though if no other ideas surface. Thanks Hero.
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#4 Zorns Lemma

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Posted 11 May 2013 - 11:54 PM

After watching your video demonstrating functionality, I don't think there's an easy/practical way to get the look you want while retaining that exact functionality.

Because the force of priming is taken up entirely by that ring (purple from solvent weld), you're going to encounter crazy amounts of torque on any sort of adhesive bond, most of which were designed only for lateral stress. You also have almost 0 surface area to bond to.

Mechanically fastening is also going to be a pain because there is barely any material concentrically.

My best ideas are:

1) That purple ring/sliding piece that you use to pull back the plunger rod and then prime the blaster should not have a hole for the CPVC to attach to, because wall thickness is too low for any sort of structural strength. Instead, take a piece of 5/8" solid rod, drill an appropriately sized hole through it (have fun centering that), dremel it down (this part will be awful) to fit the curvature of your PVC ring, and then use a screw from the inside of the ring into the rod. A 1/4-20 screw is probably strong enough to withstand the priming forces.

2) Use a PVC tee and slide it through there so that way the plunger rod can fit through and you have a single molded piece to attach your cocking bolt to. This may require you completely redesign your blaster so the pieces fit
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#5 Phree Agent

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Posted 12 May 2013 - 07:37 PM

After watching your video demonstrating functionality, I don't think there's an easy/practical way to get the look you want while retaining that exact functionality.

Because the force of priming is taken up entirely by that ring (purple from solvent weld), you're going to encounter crazy amounts of torque on any sort of adhesive bond, most of which were designed only for lateral stress. You also have almost 0 surface area to bond to.

Mechanically fastening is also going to be a pain because there is barely any material concentrically.

My best ideas are:

1) That purple ring/sliding piece that you use to pull back the plunger rod and then prime the blaster should not have a hole for the CPVC to attach to, because wall thickness is too low for any sort of structural strength. Instead, take a piece of 5/8" solid rod, drill an appropriately sized hole through it (have fun centering that), dremel it down (this part will be awful) to fit the curvature of your PVC ring, and then use a screw from the inside of the ring into the rod. A 1/4-20 screw is probably strong enough to withstand the priming forces.

2) Use a PVC tee and slide it through there so that way the plunger rod can fit through and you have a single molded piece to attach your cocking bolt to. This may require you completely redesign your blaster so the pieces fit



Thanks Zorn, I think I will give option 1 a try next. I will keep this thread posted with results.
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#6 Carbon

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Posted 13 May 2013 - 11:25 AM

Zorn has largely covered the bases here, but I thought I'd mention a few points based on some similar designs I've had.

I used a somewhat similar "priming shuttle" on the SNAP-8. It was several layers of PVC thick, and used screw mounts similar to those used for particle board furniture (not sure exactly what they're called, but they have coarse threads on the outside, and are threaded for a machine screw on the inside.). Anyway, I discovered after only one war that I was already developing stress fractures at that screw join (the reason why I never bothered posting it). My design pulled the spring back as opposed to pushing it, but the concept was similar, as the plunger rod slid through it.

Long story short, I'd suggest Zorn's second idea, as it allows you to use a molded piece, and spread the force out over a larger area.

Sidenote: I'll be curious to hear how you feel about long-term use of this design: I've found that push-spring designs tend to be more tiring to use (as they require use of the tricep vs the bicep).

Edited by Carbon, 13 May 2013 - 11:26 AM.

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