NerfHaven: Homemade Rifle (Longshot-esque) - NerfHaven

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Homemade Rifle (Longshot-esque)

#31 User is offline   dapperrogue 

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Posted 23 February 2012 - 09:57 PM

The catch tube (the inner polycarbonate tube that the spring compresses against) is 1 1/4" OD, 1/16" wall. It is 7 1/2" in length. The ring that holds the back of the spring just sits on top of it.

A rainbow style catch poses a few engineering problems for this type of gun.
1) There's no guarantee you'd get the plunger rod into the rainbow catch, with the current layout. I get around this with the prototype version of the gun with the point on the end of the plunger rod, but I don't want to carve another one of those since I don't have a lathe. Plus, it was a pain to carve.

2) The plunger rod is free to rotate around inside the air chamber. In fact, the spring does cause it to spin some each time it's fired. You couldn't just have a notch, you'd have to have a 360 degree groove (which was a pain to carve). So, you basically end up with what I made in the prototype -- point plus groove.

3) To combat point 1, perhaps you could put it at the other end of the catch tube (the spring end). Because the air chamber slides back over the catch tube, it would cover the end of the rainbow catch when you prime the blaster. Not sure how you'd get the trigger to work in that case. You'd have to work around that space somehow, or have a trigger that wasn't always connected. You'd still need a 360 groove, but wouldn't have to make a point any more. Groove was still a pain to carve.


I ended up making a pivoting catch, with the pivot point located inside the catch tube in-line with the plunger rod.

Here's what it looks like:
Posted Image

And here's what it does when the trigger is pulled:
Posted Image


When the washer moves back, it engages the hook. Trigger releases it. Because of the pivot location, the K26 doesn't slip off OR fight the trigger.


Edit: Also, video up: http://www.youtube.c...h?v=9wovA97NgBY

This post has been edited by dapperrogue: 24 February 2012 - 07:55 AM

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#32 User is offline   Meaker VI 

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Posted 24 February 2012 - 11:15 AM

View Postdapperrogue, on 23 February 2012 - 09:57 PM, said:

A rainbow style catch poses a few engineering problems for this type of gun.
1) There's no guarantee you'd get the plunger rod into the rainbow catch, with the current layout....

3) To combat point 1, perhaps you could put it at the other end of the catch tube (the spring end). ... Not sure how you'd get the trigger to work in that case.


If you put the catch at the end of your catch tube, since that tube is fixed, a rainbow catch could probably be worked out such that it went back up and around inside the tube. I see how that would be a pain though - and I'd forgotten about the 'all-around' catch issue; my current setup has a notch in a dowel that actually stays pretty well in place, despite it being free to rotate.

It'd require a redesign, but do you think you'll be looking into removing the catch tube? It adds 7.5" of mostly empty space to the length of the blaster. In my designs, I'm hoping that a short-plunger with a spacer on it (possibly a small PVC endcap or coupler) will ride inside a spring; keeping the plunger centered and able to use a rainbow-style catch. Then I'd push that back with my dart-pusher, rather than push with the whole plunger tube. It adds another seal to worry about (dart tube to plunger tube), but should take quite a bit out of the length. You've got that dart-tube/plunger-tube seal down pretty well, I was surprised when you then bolted it in place rather than use it; I would have just glued it down and/or used a bushing instead of making seals.

All in all, however, this is really cool and your images and video do a great job of showing everything. This may be one of the simplest-to-understand homemades that uses clips.
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#33 User is offline   dapperrogue 

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Posted 24 February 2012 - 03:26 PM

Oh. I see. You'd make it work like standard longshot internals where the air chamber is fixed and the breech/reducer pushes the plunger back. In that case, yes, you could get rid of the catch tube and simply have a rainbow catch or something at the back of the air chamber. I still think you'd want to have a long plunger rod, though, which would stick out the back of the assembly when primed. Shouldn't be much of an issue, though, because you'd have a stock or something to cover it.

I have a sliding air chamber because it makes a really secure priming handle attachment point. I know I'm not the only one who's broken a longshot bolt sled, and this was my way of eliminating that as a design piece. Not saying you'd need to use a bolt sled in your design, of course. You could somehow attach the priming handle directly on the 9/16" brass.


FYI, the length of the gun can be reduced by switching to an angel breech instead of the breech system I've shown (e.g., cut your dart reciever hole into the 17/32" rather than into the 9/16", and use a shorter piece of 9/16" that slides over it). This would let you chop about 5" or 6" off the front of the gun. Potentially even more, since you could cut down the remaining 17/32" to whatever you like. An angel breech is definitely something I'd use if building a pump-action version to make it easier to handle. For the bolt-action rifle, I wanted to maximize barrel length, so I made no cuts whatsoever to the 17/32 brass.
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#34 User is offline   Meaker VI 

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Posted 24 February 2012 - 04:55 PM

View Postdapperrogue, on 24 February 2012 - 03:26 PM, said:

Oh. I see. You'd make it work like standard longshot internals where the air chamber is fixed and the breech/reducer pushes the plunger back. In that case, yes, you could get rid of the catch tube and simply have a rainbow catch or something at the back of the air chamber. I still think you'd want to have a long plunger rod, though, which would stick out the back of the assembly when primed. Shouldn't be much of an issue, though, because you'd have a stock or something to cover it.

I have a sliding air chamber because it makes a really secure priming handle attachment point. I know I'm not the only one who's broken a longshot bolt sled, and this was my way of eliminating that as a design piece.


Yep, basically that. I'm not too worried about the bolt sled breaking though because I'm planning on cutting up a piece of 1" (that should nest inside the 1 1/4" plunger tube) so it has a slot in it that is long enough to allow the cycle to happen. Ideally, I'll leave ~1" on either end; one to attach to the pump and the other to nest dart-pusher and pressure chamber seal parts in. The current design looks like this:
Posted Image

Blue = Charging system
Green = Barrel
Red/Orange = Plunger
Yellow = Trigger
White = Stationary

The clip would stick out the side and I don't have any parts to support it drawn.
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#35 User is offline   dapperrogue 

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Posted 25 February 2012 - 11:20 AM

Played around with Google Sketchup. Seems good, but will take me forever to put something together. So, graph paper and camera for now.

EDIT: Don't use these as plans. Templates coming soon. Also, design flaw corrected. See two posts down for what I'm talking about.

Scale is one square = half an inch.

Here are the 1/8" pieces:
Posted Image
The two smallest pieces here are used in the firing mechanism. The very small ones are used to keep the trigger in line. The slightly longer ones are used to connect the trigger to the catch hook.

Here are the 1/4" pieces:
Posted Image
I divided the page into four parts. Top left is for the front of the gun. Top right is for the center of the gun. Middle is for the air chamber/priming handle/reducer assembly. Bottom is for the rear of the gun.

The blacked in holes (around the grip) represent screws that are used to hold a small spring in place. One for the trigger, one for the catch.

This post has been edited by dapperrogue: 01 March 2012 - 07:34 PM

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#36 User is offline   atomatron 

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Posted 28 February 2012 - 03:55 PM

I cannot believe I missed this thread for so long. Excellent work thus far.
Perche Germolgi. [Because it shoots]

Rainbow Clan
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#37 User is offline   dapperrogue 

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Posted 01 March 2012 - 07:33 PM

Posted Image

Great news:
Meaker VI has made an awesome 3d model of the blaster, and is working on actual, printable templates for you guys. He's built the whole thing off of my cell-phone photo of a graph paper sketch (aka, no small feat). I've had a chance to review it, and I'm really impressed. This is a screenshot from Sketchup.


Sad news: While making a firing test video (not a range test), I snapped the priming handle off.

Posted Image
Posted Image


Bad news:
I'm pretty sure the handle design I posted is flawed. The piece(s) failed at the screw-holes that attach the handle to the plates on the plunger tube.


Good news:
I designed a better handle, and have sent it to Meaker IV (also shown in the first photo):
Posted Image

Rather than have separate pieces for the handle and for the plates, I've made them one and the same. There are no longer screw holes that will weaken the part.

This post has been edited by dapperrogue: 01 March 2012 - 07:38 PM

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#38 User is offline   dapperrogue 

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Posted 05 March 2012 - 10:59 PM

Ok, this is completely Meaker VI's doing, but here are the templates and 3d model he created. Again, I am really impressed with how cool this is, and that he was excited enough to do all of this.

This pdf is 12" x 12" sheets:
http://dl.dropbox.co...4889/LAMBDA.pdf

This pdf is split onto 8 1/2" x 11" sheets, so you'll have to align what you print, but it will work with a letter-sized printer:
http://dl.dropbox.co...LAMBDA_8511.pdf

Here's the Google Sketchup model:
http://dl.dropbox.co...64889/HMLS3.skp

Thank you so much for making these! I really dig the decorative Lambda on the side of the stock.



One thing about the templates he asked me to share is that the surface holes are indicated, but not the edge holes. The positioning of holes drilled in edges should be apparent from how the pieces line up. You should use the other pieces as guides when marking your edges.

For the holes in the edges of 1/4" polycarbonate, they should ideally be drilled 7/64" and tapped with a 6-32 tapping bit (like in Captain Slug's +Bow writeup). If you are lazy, like me, you can drill with a 1/8" bit and not tap, just force the screws in. However, I expect all of you to drill and tap everything properly.


The larger hole diameters are as follows:
Barrel Guide: 9/16"
Mag Well: 5/8"
Plunger Tube (PT) Reducer: 9/16"
Spring Stop: 1/2"

Both of the holes in the Catch are 9/64" -- they act as hinges, and this diameter is large enough to pivot freely on a 6-32 machine screw.

To make the Plunger Tube Reducers and the Spring Stop, I suggest you drill half-way through your 1/4" piece of polycarbonate with a 1 1/2" hole saw, then bore out the correct center diameter with a spade bit, then resume drilling the rest of the way through with the hole saw. Your outer diameter will be less than 1 3/8", but the rubber washers will compensate. This will leave you with a 1 1/2" hole in both handles, which is what you want for it to fit over your plunger tube.


Parts List Time:

Quote

Stuff I got from McMaster:
8574K26 2 Each Impact-resistant Polycarbonate Sheet, 1/8" Thick, 12" X 12", Clear
8574K28 1 Each Impact-resistant Polycarbonate Sheet, 1/4" Thick, 12" X 12", Clear
8585K431 1 Ft. Impact-resistant Polycarbonate Round Tube, 1-1/2" Od, 1-3/8" Id, 1' Length, Clear
8585K631 1 Ft. Impact-resistant Polycarbonate Round Tube, 1-1/4" Od, 1-1/8" Id, Clear, 1' Length

91780A337 10 Each Aluminum Female Threaded Hex Standoff, 1/4" Hex, 1-1/2" Length, 6-32 Screw Size

90272A146 1 Pack Zinc-pltd Stl Pan Head Phillips Machine Screw, 6-32 Thread, 3/8" Length
90272A148 1 Pack Zinc-pltd Stl Pan Head Phillips Machine Screw, 6-32 Thread, 1/2" Length

6435K54 2 Each One-piece Clamp-on Shaft Collar, Black-oxide Steel, 9/16" Bore, 1-5/16" Od, 7/16"w

90131A104 1 Pack Abrasion-resistant Reinforced Rubber Washer, 1/2" Screw Size, 1-3/8" Od, 1/8" Thick
9637K26 5 Pack Continuous-Length Compression Spring Spring-Tempered Steel, 11" L, .844" OD, .08" Wire
8538K18 5 Ft. Nylon 6/6 Rod 1/2" Diameter
9562K46 1 Each Stretch-fit Rotary-shaft Ring Seal, 1" Shaft Diameter, 0.95" To 1.07" Shaft Diameter


Stuff you can get from your hardware store in smaller quantities:
90272A151 1 Pack Zinc-pltd Stl Pan Head Phillips Machine Screw, 6-32 Thread, 3/4" Length (I used 5 of these).
91090A109 100 Pack Zinc-Plated Steel Large-Diameter Flat Washer 1/4" Screw Size, 1-1/4" OD, .04"-.06" Thick(I used 2, for my plunger head)
90126A509 100 Pack Zinc-Plated Steel Type A SAE Flat Washer NO. 6 Screw Size, 3/8" OD, .03"-.07" Thick (I used 1 or 2, for my plunger rod)
90295A080 100 Pack Nylon 6/6 General Purpose Flat Washer Off-White, NO. 6 Screw Sz, .32" OD, .02"-.04" Thk (I used 2, for the catch)

Stuff I got from my local hardware store (didn't find 17/32 brass on McMaster, only 9/16" and 1/2" -- probably there somewhere though):
9/16" Brass tube, 1 foot - Dart pusher, plus misc. brass
17/32" Brass tube, 1 foot - Barrel
1/2" Brass tube, 1 foot - Breech

Stuff I don't know where you would find, but probably have in your house already:
2 small springs, one for the trigger, and one for the catch. These fall out of nerf blasters if you take them apart. Pretty sure mine were from various Longshot locks.
Coarse Threaded screw, 1 1/4" (wood screw?) - I had these lying around my house. Used for plunger rod ends, because 6/32 thread ripped out of the holes.



Note that I didn't include the 3/4" washer I mentioned I was using for the rod catch. I switched to a 1 1/8" diameter plate out of spare 1/8" polycarbonate, but I might switch back to a metal washer of the same diameter if I can find one at the hardware store:
Posted Image



Since I mentioned it last time, here are the 1-piece handles. Here's the plunger tube, priming handle, and 9/16" breech all by itself, out of the blaster.
Posted Image

And here it is in the blaster. Note that I switched to 1 1/8" metal washers for the plunger head. I included these in the parts list above.
Posted Image


Lastly, that means the blaster is no longer broken! Range test coming soon!
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#39 User is offline   Meaker VI 

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Posted 06 March 2012 - 08:22 AM

View Postdapperrogue, on 05 March 2012 - 10:59 PM, said:

One thing about the templates he asked me to share is that the surface holes are indicated, but not the edge holes. The positioning of holes drilled in edges should be apparent from how the pieces line up. You should use the other pieces as guides when marking your edges.

For the holes in the edges of 1/4" polycarbonate...


And actually, I'm not positive that the sheets are indicated as 1/4" or 1/8" on the plan, but that shouldn't matter. The more complex pieces are 1/4" and the large flat pieces are 1/8". If anybody has any issues with the templates or model, let me know and I'll take a look at them.
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