19 replies to this topic

[minsc]

I present to you the RSCBow. It’s basically a SNAP or SNAP bow design scaled up to 1 ½ in. PVC, with 2 eight shot RSCB sections made into nice stock. I used ideas from Carbon’s original SNAP mk2 design and wood grip design, Rork’s SNAP bow mk4 design and superlative head, and the RSCB guys.


Materials Needed:
1 12” Length of 1 ½ in. PVC (can be shortened to 11” without any effects)
2 1 ½ in. by ½ in. PVC Bushings
2 1 ½ in. couplers
1 ½ in. PVC ball valve
2 ½ in. CPVC tees
1 ½ in. CPVC elbow
1 ½ in. PVC coupler
1 ½ in. PVC tee
1 ½ in. PVC endcap.
1 12 in. length of ¼ in. PEX pipe
1 +bow spring
1 clothespin, zipties, nail, all the stuff you need to make a clothespin trigger
1 1 ½ in. washer
1 rubber sheet
1 CPVC endcap
1 Belleville washer
Screws
½ in. PVC
½ in. CPVC
Wood

Part 1. RSCB stock. This is probably the easiest and in my opinion the most useful part of this gun, as it can be used in virtually any nerf gun with enough power.



To make one of these for darts that fit CPVC, I’ve found the best way is to use CPVC fittings for the T section of the RSCB (the elbow and tee). Then, I use a ½ in. PVC couplers lightly sanded/reamed out and shove the CPVC fittings tightly into PVC coupler. I’ve found that ½ in. CPVC fittings are only slightly larger in diameter than ½ in. PVC, and will usually fit into ½ in. PVC fittings with a little force. The CPVC tee is reamed out completely on the side facing the PVC, and the CPVC barrel I use on the other side is reamed out completely as well. See below:



I personally believe this is the most efficient RSCB setup in terms of dead space, and the smooth transitions due to the reaming have almost never given me a double fire on any setup I’ve used, including big blasts.

The rest of the RSCB stock is made of 2 sections of PVC with a ball valve in between. I made mine able to hold eight 1 ½ in. stefans, so about12 in. long each. You can make it as long or as short as you want, as long as the one closer to the air supply holds equal or more darts, or else the ball valve will eat your darts. The way it works is you fire all eight stefans with the ball valve closed, then open the ball valve and shake until the darts fall into the next section. Once you close the ball valve again, you can reload the back at any time.

The stock part is shown below:



I shoved a crayola marker barrel wrapped in tape into the pvc section. This allows for easy loading, as darts can be loaded in but won’t fall out because they fit snugly in the marker area. The PVC tee is cut down for comfort and a short section of PVC with an endcap was used for the stock. The whole setup is very stable and if you cut it to the right length, very comfortable.

Part 2. Plunger rod assembly

This is very similar to the setup Rork created in his last SNAP bow design, using ¼ in. PEX pipe for lightness and cheapness, and a similar plunger head to his superlative plunger head design.



I found the rubber sheet in the plumbing section of Lowes for about 2 bucks. It comes in 2 different thicknesses, so I chose the thicker one; I think it was like 1/8th in. or something. Basically, it allows you to cut custom rubber washers of any size and shape you need, which was great because I couldn’t find 1 ½ in. rubber washers anywhere.

I traced the inside of the 1 ½ in. PVC coupler and cut it out using scissors. This turned out to be a little too big, so I trimmed it down carefully using a utility knife until it fit snugly into 1 ½ in. PVC with a concave shape and was airtight. Patience is key here; you don’t want jagged edges, or for it to be too small or else it’ll be useless.



The order for the plunger head goes top to bottom from left to right. I ended up using a different bolt and wing nut, but basically it was the same. First I centered and drilled a hole in the CPVC cap for the bolt. Then, I roughed up the surface of the cap and superglued the flat washer to it. Make sure you carefully superglue the concave washer to the top of the flat washer, using superglue liberally around the seams. Then poke a hole through the rubber washer, and bolt everything together. The setup is shown below.



The next step is to make an epoxy putty ramp against the flat washer to allow the trigger to smoothly catch.
When you are finished, put a short stub of CPVC in the endcap and drill a tiny hole through the endcap, the CPVC and the PEX at the same time. I wrapped e tape around the PEX until it was snug in the CPVC. Now your plunger head is complete.



The pullback handle was made from a CPVC tee, CPVC, a short screw and gratuitous amounts of epoxy putty.

Part 3. Rest of SNAP and Carbon style wood grip

The main plunger tube in this gun was 12 in. long, but looking back you could definitely get away with 11 in. or maybe even 10, as the spring is only 11 in. long, and there is extra length from the coupler and bushing in the back.

Both the 1 ½ in. couplers in the front and back were cut down on one side about halfway from the edge to the middle. In the back coupler, this serves to allow room for the air hole on the bushing while saving space. The air hole in the bushing was cut using a ½ in. spade bit. For the front, the 1 ½ in. to ½ in. bushing was also cut down to reduce dead space. The part was cut to about where the flat section begins.

Fit the back coupler and the bushing together, then drill pilot holes for screws through both parts. I did three spaced equally around the part.

Now for the handle, this gets a little tricky. In Carbon’s original design, a section was cut out of the coupler to allow it to snap on, but because in this design the coupler is actually used as a coupler, I chose to leave it whole. Unfortunately, this meant drilling and screwing the handle on with screws at a slight angle.



I tried to counter sink the screws as much as possible, but they still stuck out and made fitting the bushing and plunger tube on impossible. I dremeled a small groove into the bushing and plunger tube for the screw head, which worked like a charm. This also helps align the screw holes when you disassemble and reassemble the gun.



Assemble the RSCBow and it is almost completed. Make sure to put the rear bushing and spring on the plunger rod before you screw on the plunger head. The next part is to add a clothespin trigger, which you can read about in Carbon’s guide to SNAP’s. The plastic clothespin I used was unfortunately pretty flimsy, and would nearly fly apart after being fired, so it is currently held together with rubber bands, which may be ugly, but work. In addition, to prevent said destruction, I put a block of wood behind the trigger to limit the trigger pull length, which prevents the pin from being pulled completely out and exploding.



Attach the RSCB stock to the RSCBow by forcing the CPVC elbow into the front bushing. This is the most efficient and compact way to attach it, and it is pretty sturdy due to the CPVC being slightly larger than ½ in. PVC. An optional reinforcement would be to take a metal strip and secure the ball valve to the rear coupler with screws, which I haven’t done but will in the near future.

Now you to can make your very own RSCBow. For those of you scared to make homemades, I have to say this was my first one, and it was a lot easier than I expected it to be. It’s very convenient to be able to make something exactly to your needs. I haven’t tested ranges, but I’d assume due to the extra plunger volume and increased deadspace from the RSCB stock, it gets similar ranges to SNAP bows and the like. Right now all I have is an 8 in. cpvc barrel on the end, but I may go longer.

Thanks for reading guys. QCF’s?

Edit-Pictures weren't right.

Edited by minsc, 04 April 2010 - 12:33 PM.

[mr yetti]

Nice! Kow much weight does the rscb add?

[Daniel Beaver]

The crayola barrel in the stock is a nice solution for keeping the darts from falling out - I may have to steal that idea.

[Carbon]

A nice collection of tweaks here.

In addition, to prevent said destruction, I put a block of wood behind the trigger to limit the trigger pull length, which prevents the pin from being pulled completely out and exploding.

My favorite part. Making and attaching a PVC covering to prevent overpull of the clothespin is the last truly annoying and fiddly part, as far as I'm concerned. This is quick, easy, and effective (my favorite combination). Nice job.

[rork]

I like it. My only suggestion would be to nest a reducing bushing or coupler directly in the front of the pressure chamber, a la the Plusbow, rather than using the 1 1/2" coupler. Done properly, this will improve the lines of the gun, the life of the plunger head, the weight, the seal, and the cost. I've been toying with the idea of cutting my own sealing washers for probably a year or more. Props on making it work. And I had guessed that it would be possible to easily upsize my plunger head to fit the tube. Glad it worked (although I would recommend you add the epoxy putty ramp to prevent overdraw and washer damage). And while I coudn't care less about RSCBs, I do kind of want to make a SNAP with 1 1/2" pvc now, even though my setups are borderline overpowered as it is...

[minsc]

Nice! Kow much weight does the rscb add?

Not too much, It also makes a great sight as its pretty much a straight line 3 feet long. Keep in mind that at most this thing maybe wieghs 2 pounds, so a little extra wieght for the ROF is a worthwhile tradeoff.

The crayola barrel in the stock is a nice solution for keeping the darts from falling out - I may have to steal that idea.

Thanks for the compliment. Alternatively, you could also use a section of CPVC, or whatever barrel material is on the opposite end of the RSCB.

My favorite part. Making and attaching a PVC covering to prevent overpull of the clothespin is the last truly annoying and fiddly part, as far as I'm concerned. This is quick, easy, and effective (my favorite combination). Nice job.

Thanks for the compliments. Originally I had planned for a PVC covering for aesthetic reasons, but I couldn't do it because of the rubber bands keeping the whole thing together.

I like it. My only suggestion would be to nest a reducing bushing or coupler directly in the front of the pressure chamber, a la the Plusbow, rather than using the 1 1/2" coupler. Done properly, this will improve the lines of the gun, the life of the plunger head, the weight, the seal, and the cost.

Originally I thought about doing that, but I couldn't find a bushing that was close. A 1" bushing is just a tad too big, and a 3/4" bushing would require a lot of tape or epoxy to bridge the gap. As far as wieght, seal, and cost, the wieght isn't too big of a concern, the seal with correct fittings is probably the best its going to be, and the cost is about 50 cents. Also because I made the plunger tube too long, the plunger head never hits anything, it stops when the handle hits the bushing in the back.

I've been toying with the idea of cutting my own sealing washers for probably a year or more. Props on making it work. And I had guessed that it would be possible to easily upsize my plunger head to fit the tube. Glad it worked (although I would recommend you add the epoxy putty ramp to prevent overdraw and washer damage). And while I coudn't care less about RSCBs, I do kind of want to make a SNAP with 1 1/2" pvc now, even though my setups are borderline overpowered as it is...

Yeah, I looked for 1 1/2 in. washers, but this was a pleasant surprise. It should be available at any Lowes in the plumbing section. And why stop at 1 1/2? I've seen some 2" SNAPs on this site, but there's really no limit to how big your cross section can be, once you find a sturdy material for the catchplate. A concept I've had in my head for the longest time is a blaster where the plunger system is disk shaped, or wider in diameter than it is long, for a medium air output at a super fast rate.

As for the epoxy, I'm starting to think I have some bad batches or something. The putty is still moldable and rips apart when it comes in contact with the firing pin. If anyone has a good suggestion for putty, let me know. I'm using the home depot brand Plumber's Putty that comes in a clear tube.

Edited by minsc, 28 December 2009 - 12:09 AM.

[ice]

I really like the RSCB stock idea. What else could I use that for...

[Carbon]

Yeah, I looked for 1 1/2 in. washers, but this was a pleasant surprise. It should be available at any Lowes in the plumbing section. And why stop at 1 1/2? I've seen some 2" SNAPs on this site, but there's really no limit to how big your cross section can be, once you find a sturdy material for the catchplate.

Didn't even think of that. I've built 2" SNAPs, but getting a rubber washer was a limiting factor. The plunger head I ended up building worked, but was big and heavy, and ended up outdistancing a 1.25" SNAP by only 10% or so (not really worth it). Optimizing the seal with a custom fit and using a svelte plunger head should finally give the kind of results that a large cross-section plunger should be able to achieve.

[CA13]

Sweet blaster. I might just make one of these and find a use for a Furyfire handle.

Maybe you should redo that handle though. Looks un-comfy. One of my SNAPs has a handle like this:
_______

/ /\ / / \ ^ / / \ / Front Face /______/ \ Sides <--+--> \ \ \ _ / \______\/\ \/\ \/ Rear Face \ _____\ \ | | \ |_____| \ \ \ / \ \ / \ \ / \ \ / \ \ / \_____\/

DAMN ASCII EXPLANATIONS. THEY DON'T WORK.

Edited by CA13, 28 December 2009 - 04:34 PM.

[minsc]

Sweet blaster. I might just make one of these and find a use for a Furyfire handle.

Maybe you should redo that handle though. Looks un-comfy. One of my SNAPs has a handle like this:
_______

/ /\ / / \ ^ / / \ / Front Face /______/ \ Sides <--+--> \ \ \ _ / \______\/\ \/\ \/ Rear Face \ _____\ \ | | \ |_____| \ \ \ / \ \ / \ \ / \ \ / \ \ / \_____\/

DAMN ASCII EXPLANATIONS. THEY DON'T WORK.

I think I will in the future, I only lightly sanded and beveled the edges, so its still essentially a rectangle. It does start to be uncomfortable after priming the gun for a while, as the spring is so powerful.

[Zorns Lemma]

Who originally came up with the idea of using a belleville washer to help shape rubber washers into a nice cup shape? I've currently been fabricating dimpled washers out of plastic sheet and this looks to be saving me mad amounts of time, so I need to give that person due props.

[rork]

That would be Carbon, although this washer is much larger than the finishing washers he and I use.

[Zorns Lemma]

Hmm, yea I see finishing washers mentioned in Carbon's SNAP writeup. But finishing washers are meant to look pretty and help countersink screw heads. Belleville washers act in a similar fashion to lock washers, in using shear forces to pretense screws and prevent dislodging from vibration, which is also why they're available in larger sizes.

So I guess I should thank minsc for the find. Prefabricated parts turned to a new purpose is what homemades is about.

[CA13]

I was considering making a large SNAP with a foot stirrup mounted to the front of it, so I could cock the gun medieval-crossbow style, and then attach my loaded barrel to the coupler. If you have trouble cocking your rifle, maybe you should do some research and plan it out.

[k9turrent]

Done it

[CA13]

Well, butter my butt and call me a biscuit.

[k9turrent]

Well, butter my butt and call me a biscuit.

NOM NOM NOM NOM

[minsc]

Hmm, yea I see finishing washers mentioned in Carbon's SNAP writeup. But finishing washers are meant to look pretty and help countersink screw heads. Belleville washers act in a similar fashion to lock washers, in using shear forces to pretense screws and prevent dislodging from vibration, which is also why they're available in larger sizes.

So I guess I should thank minsc for the find. Prefabricated parts turned to a new purpose is what homemades is about.

Thanks for the compliment. It was in my random parts bin, and I figured it would be perfect for the application, but I didn't know what it was called.

I was considering making a large SNAP with a foot stirrup mounted to the front of it, so I could cock the gun medieval-crossbow style, and then attach my loaded barrel to the coupler. If you have trouble cocking your rifle, maybe you should do some research and plan it out.

Sounds like a good idea, and it's obviously feasible. I don't have trouble cocking my gun though, its just the handle. My only concern is that you could have an extremely powerful single shot, like a medieval crossbow, but also have to put it down to slowly reload, like a medieval crossbow.

[Samzilla]

As for the epoxy, I'm starting to think I have some bad batches or something. The putty is still moldable and rips apart when it comes in contact with the firing pin. If anyone has a good suggestion for putty, let me know. I'm using the home depot brand Plumber's Putty that comes in a clear tube.

This topics kinda old but i thought i might still chime in with a semi-useful comment. Plumber's Putty does not always = epoxy putty. Some "plumber's" putties don't harden at all.

[minsc]

So I finally took the time to take a range test, as it is very nice outside today, and everyone else is still in church. 16 shots were fired with single bb stefans. I used a 12 in. CPVC barrel. The shots ranged from low 90's to low 80's as the 8 shot clip emptied. A couple darts veered off wildly and weren't counted. All in all I'm pretty happy.

I also changed out the PEX plunger rod for plain ol' CPVC. The PEX may have been lighter, but it also snapped on me 2 times and stuck out at a wierd angle when primed.

Finally I still haven't replaced the epoxy, but priming is still pretty simple. I just pull back the plunger rod with my left hand until it stops, then I press the trigger a little bit, and move the rod back a little more and let go of the trigger. It's pretty easy, I just have to keep my hand on the handle.