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The Fomebow - Extensive Bow And Arrow Makeover.

Selectable barrel system, RSCB breech, and more. Video, page 2!

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#1 Fome

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Posted 11 July 2009 - 05:11 PM

This is my contest submission.

Remember this guy from the 1990s? I found one in my attic a few months ago, set out with an over-ambitious project, got frustrated, and finally simplified it into the contents of this thread. I hope you enjoy.

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Here's a general outline:

1. Basic BnA mods
a. Materials needed
b. Plunger + plunger tube
c. Bungee anchor
d. Reinforcements

2. Selectable barrel system
a. Materials needed
b. How it works
c. Construction and end result

3. RSCB breech
a. Materials needed
b. How it works
c. Exploded view
d. Construction and end result

4. Homemade arrows
a. Materials needed
b. Construction
c. Concept arrows

5. Finishing touches
a. cosmetics/ergonomics
b. RSCB string
c. Priming handle bungee centering knob


1. Basic BnA Mods

a. Materials needed
- Hotglue + gun
- Epoxy Putty
- 1/2" USS metal washer
- 20mm Metric washer
- 016x1/2" Brass strip
- 4 small screws and nuts
- 10 1/2" Bungee
- some other form of thin, long reinforcing material

b. Plunger + plunger tube

Assuming you've already opened the blaster (incredibly easy, 8 big screws), take out the pink plunger tube and yellow plunger.
Cut off the white tab at the tip of the plunger tube, as seen here:
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I used a sharp razor blade

Remove the black cushion, rough up the plastic, lay down some hot glue, center the foam again and place it back on. Then fill the remaining hole with glue. Should look like this:
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The seal was already pretty good, being able to vacuum load stefans, so I left it.

Next, take your pink plunger tube, cut the "barrel" until you have a 1/4" nub. Epoxy a 1/2" PVC coupler and set it aside. (I do not have pictures of this because I cut a flush cut on the plunger tube and spent about a week trying different adhesives to get my PVC bushing to actually stay on. More surface area = better bond, so use part of the original barrel if you can.

c. Bungee Anchor
I had trouble finding a spring suitable for this guy, so I went with the tried and true method of attaching a bungee to the shell. Unfortunately, I could see that with time, the bungee might pull the shell apart. Let's delay this process, start with the 3 slots towards the front of the shell:

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Drill/dremel an opening at the back of the middle slot. Take a thin piece of reinforcing material (some kind of brass would work), I used part of a steel bristle from a street cleaner. B) Secure it, and test your bungee hook, make sure it fits, like so:

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We will be covering this with epoxy putty later. This provides a durable, secure, and load-distributing area for the bungee to attach to.

d. Reinforcements.

These reinforcements should be done towards the END of the modification process.

According to what sort of barrel/coupler/RSCB setup you settle on, any degree of dremeling will be required. Although I had to do surprisingly little, I still had to knock down some plastic walls and then rebuild them in other areas while reinforcing the blaster. The BEST way to do this is to fill the shell with putty and then press your FINISHED plunger tube setup into the putty, close the shell and then immediately open it up again and remove the plunger, smoothing out any clinging bits. Here's a picture of what I eventually reinforced:

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1. I epoxied a 20 mm metric metal washer inside of the plunger tube. (this prevents the plastic from flexing, and cracking the e-putty which attaches the coupler/bushing)
2. I also replaced the flimsy plastic ring that holds the spring against the shell with a 1/2" USS metal washer.

NOTE: You DEFINITELY need to reinforce the front handle.

Also, although not being functional... yet. I thought that the pink "bow arms" were a little flimsy:

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So I reinforced them with 016x1/2" brass strips. I beveled one side to fit with the curves of the arm and drilled two holes, one at the top of the arm and one at the bottom. I may "string" these like the original BnA, I may not. At least now they're much stronger. Here it is, firmly attached:

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More to come.

Edited by Fome, 18 February 2010 - 09:57 PM.


#2 Fome

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Posted 11 July 2009 - 05:12 PM

2. Selectable Barrel System

This system allows you to switch between an RSCB setup and a singled barrel with relative ease. It can also be adapted to be used on various other high-volume guns. (+bows, PAS, BBBB, etc.)

a. Materials needed
- 1/2" SCH40 PVC
- 1/2" SCH40 PVC T joints (2)
- 1/2" SCH40 endcap
- 1/2" CPVC
- 1/2" FBR
- hot glue + gun
- sandpaper, fine and coarse grit.

b. How it works:
Singled barrel: The sanded CPVC seals with the ring of 1/2" SCH 40 at the back of the T-joint, forcing all of the air through the barrel, instead of the RSCB setup.
RSCB plug: This essentially stops the air from going out one branch of the T-joint, forcing it instead into the RSCB assembly.

c. Construction and End result
First, take one of your PVC T joints, fill one end with PVC, and then cut it so it's flush. This end will connect with your plunger tube. You may add a dart stop if you like:

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Next, constructing the singled barrel. (I used CPVC at the time because that was my barrel material, I will likely change this so it uses brass instead but the same basic concept can be gleaned)
Take a length of CPVC and hammer it into a piece of sch40 PVC so that 2" are exposed.
This next part is a little tricky: sand the 2" of CPVC so that it can slide into 1/2" SCH40 yet remain air tight.
Here is what it should look like:
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And here it is seated inside the PVC T:

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You can see how, when pushed back far enough, the CPVC creates an airtight seal with the 1/2" SCH40 PVC.

Now, we're going to make the plug which will direct air up into the RSCB assembly instead of the singled barrel.
The construction is very simple.
Take a length of 1/2" SCH40 PVC, hammer CPVC into it, allow 1/4" of CPVC to remain. Take your FBR, fill the CPVC, and fill that with hot glue. Glue a 1/2" endcap onto the other end and call it good. If that's not clear enough, here's a picture:

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3. RSCB Breech

This RSCB Breech is an alternative to using a ball valve. Ball valves can be tricky and cumbersome to use, and finding the ideal kind (low torque, high flow, etc.) might be difficult. Plus, this is just much cooler.
Note: if your darts don't move around freely in 19/32" brass then you need to go up a size.

a. Materials needed
- 9 1/2" of 1/2" SCH40 PVC
- 9 1/2" of 19/32" brass
- 4 1/2" of 9/16" brass
- 1/2" SCH40 PVC coupler
- 1/2" SCH40 PVC endcap
- 1/2" CPVC endcap
- E-tape
- FBR
- Hot glue + gun
- Flathead nail (I used a roofing nail)

b. How it works
Simple. Instead of using the 9/16" as a barrel material, it acts as a follower which pushes darts into the 19/32" brass, where they're free to move around. The locking coupler and nail keep the air pressure from ejecting the 9/16" Brass follower. completely airtight as well.

c. Exploded view
The measurements of the cuts required in the 19/32" brass and 1/2" PVC are shown in the picture:

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d. Construction and end result.
Some more explanation is necessary. Take your 1/2" PVC coupler and cut an "L" into it like this, the measurements are included in the picture:

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Set that aside and assemble your follower. Take a 4 1/2" piece of 9/16" brass, fill it with FBR and hot glue similar to before with the RSCB plug. Wrap one end with E-tape until a 1/2" CPVC endcap fits snug. Stick a 1/2" PVC endcap on top of that. Drill a hole 3 1/2" from the bare side, insert a roofing nail and epoxy/glue it into place. Glue together and set it aside.

Pictures of the follower:

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And here's some of the final setup, it should be evident where everything goes, but please ask for explanation if needed:

Open:
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Closed:
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Edited by Fome, 17 July 2009 - 03:56 AM.


#3 Fome

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Posted 11 July 2009 - 05:14 PM

4. Homemade arrows
Posted Image
These babies fly beautifully! They're much simpler to make than other methods and are unweighted, meaning they fly farther (but just as straight) due to the tilt in the fins. A separate writeup will be posted soon.
a. Materials needed
1/2" frost king pipe insulator.
1/2" FBR
Craft foam sheets
Hot glue
Electrical tape
Sharp razor blade

b. Construction

Homemade arrow writeup

c. Concept arrows

5. Finishing touches
a. Cosmetics/ergonomics
A paintjob was necessary (I smudged the original with epoxy putty). Black isn't always evil. Combined with some simple white highlights, the PJ nicely emphasizes the bright yellow and pink. I also plastidipped both handles for a very comfortable ride. Here is the finished product:

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I also had to build the singled barrel up with electrical tape. The CPVC was just a little too small for the homemade arrows to fit snugly. The previous 4" CPVC barrel was much too short, these pictures include a 7" CPVC barrel for the RSCB setup, which currently, is performing the best.

b. RSCB string
c. Priming handle bungee centering knob
One final touch improved performance significantly.

I took a plastic shelf hanger, drilled a small hole in the center of the yellow handle, and epoxied it in like so:
Posted Image

You can see how this prevents the bungee from traveling up the slant of the yellow handle. Before, it would press the priming rod up against the roof of the shell, creating friction and potentially bending or breaking the original handle. Now, the bungee stays centered, both increasing the pull of the bungee and forcing the plunging rod to take a straight path.

Posted Image



Qs/Cs/Fs?

Ranges still to come. Video's up, page 2!

Edited by Fome, 20 July 2009 - 03:09 PM.


#4 bigred1rifleman

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Posted 11 July 2009 - 05:52 PM

Your planning on replacing the back handle, right? I hate to see BnAs with big chunky handles on the back. If your going to replace it, I would suggest epoxy and a 3/4" CPVC "T". It works very well.

Finn
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#5 Fome

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Posted 11 July 2009 - 07:08 PM

Your planning on replacing the back handle, right? I hate to see BnAs with big chunky handles on the back. If your going to replace it, I would suggest epoxy and a 3/4" CPVC "T". It works very well.

Finn



I don't know why I'd replace the handle with something structurally weaker, smaller, less attractive (imo), and much less comfortable.

#6 TantumBull

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Posted 11 July 2009 - 07:14 PM

That's one sexy and practical-looking mother fucker. Excellent job, Fome. Two questions. Not sure if its just my comp. or not, but two of your pics during the barrel selector part aren't showing up for me. After reading over the writing part where the pictures should be, I'm guessing you made some sort of plug to direct air to the RSCB.

1) What's the purpose of the part where you made the CPVC slid-able but air tight?

2) When using the single barrel, what's stopping air from going into the RSCB set-up? Is this where the sanded PVC comes in?

Sorry for these questions as I'm sure the answers are obvious. I just can't figure it out without the pictures.

Edit: Fome: I'm guessing he suggested replacing it to cut down on plunger mass. You would be choosing between ugly but more effective or pretty and less effective. Then again, I may be wrong, because I don't know the weight of the BnA handle.

Edited by TantumBull, 11 July 2009 - 07:16 PM.

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#7 hardshot

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Posted 11 July 2009 - 07:18 PM

Tantum:There not showing up for me either.
Fome: That looks amazing. Would you use it in a war? I am really excited tyo see the ranges
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#8 white moonlight

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Posted 11 July 2009 - 07:36 PM

Nicely done, and great writeup.

I'm hoping to get ahold of one of these soon seing as they have potential.

Edited by white moonlight, 11 July 2009 - 07:38 PM.

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#9 aishihigeo

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Posted 11 July 2009 - 07:59 PM

So the reason for the slide able cpvc is so you can pull it out and rear load the dart?

And to use the rscp you switch out the barrel with the plug?

For the breech loading you should have a pvc covering with multiple slots. Then after each shot you can place it in the next slot eliminating dead space after each shot.
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#10 bigred1rifleman

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Posted 11 July 2009 - 08:15 PM

Your planning on replacing the back handle, right? I hate to see BnAs with big chunky handles on the back. If your going to replace it, I would suggest epoxy and a 3/4" CPVC "T". It works very well.

Finn



I don't know why I'd replace the handle with something structurally weaker, smaller, less attractive (imo), and much less comfortable.


Well, I guess I'm wierd then. I always thought that the handle was fairly flimsy and uncomfortable, and unattractive. It's your blaster, I'm just making suggestions. I think it's looking great, though.

Posted Image

Finn

Edited by bigred1rifleman, 14 July 2009 - 01:28 PM.

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#11 Fome

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Posted 11 July 2009 - 08:22 PM

Aishihigeo: Yes. I am using arrows for the singled barrel, but you could easily use stefans, yes.

Hardshot: I would. The BnA has very promising internals except for one thing: no trigger. Using large, quickly reloadable projectiles (ie, arrows) and the ROF of an RSCB (which in this case is particularly effective, given the natural motion of pulling the plunger back involves aiming the blaster down), greatly compensates for the blaster's natural weakness.

Tantum: Making the CPVC seal with the back of the T coupler allows the air to be directed solely through the single barrel, bypassing the top joint of the T completely.

Replacing the yellow handle with something that small would 1. be harder to attach the bungee, and 2. compromise its ability to be pulled back quickly, an essential process to the firing of the bow, seeing as there is no trigger. But yeah, it would probably provide a marginal increase in range.

Bigred1rifleman: Thank you.

Can you guys still not see the pictures? They're showing up for me.

Edited by Fome, 11 July 2009 - 08:27 PM.


#12 canuck

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Posted 11 July 2009 - 08:23 PM

That looks great.
You did a great job making that old school blaster kickass.

Personaly I would add a stock for extra comfort.
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#13 Hi Yah

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Posted 11 July 2009 - 08:52 PM

Nice mod. The only question I have is what kind of ranges is it getting?
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The yellow balls are also slightly smaller in diameter than the green ones.

#14 father time

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Posted 11 July 2009 - 09:00 PM

[ If you decide to use the bow arms , you must reinforce the part where they go into the main body of the gun.
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#15 roboman

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Posted 11 July 2009 - 10:07 PM

[ If you decide to use the bow arms , you must reinforce the part where they go into the main body of the gun.


Why would you need to do that? They're not load-bearing structures... They're only there for aesthetics.
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#16 SonReeceSonJensen

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Posted 12 July 2009 - 08:13 PM

The only black gun you won’t get the nuts flamed off of you for.

Very nice, I like how you can capitalize on the ROF with the simple pull-back. And it has a very sexxxy look.

Now get a red bandana and tell people you are their worst nightmare.
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#17 Vincent

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Posted 12 July 2009 - 11:36 PM

I bought a BnA a while back and did some work to it. You said your seal was pretty good, but I would recommend putting something there to keep it that way. Also, I got about 80' ranges with a barrel that was way too tight for my darts and was 2' long. The back handle on mine is almost ready to come clean off, so I think a bit of reinforcement would help you out so that that doesnt happen. Nice bow, I'm glad to see someone uses one of these besides me.
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QUOTE(Carbon @ Jul 14 2009, 07:50 PM) View Post

Heresy. Nothing beats pink flamingos.


#18 canuck

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Posted 13 July 2009 - 01:02 PM

WHy not use brass for the barrel, or copper? Anything to add on those last crucial feet.
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#19 Fome

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Posted 17 July 2009 - 04:05 AM

Nice mod. The only question I have is what kind of ranges is it getting?


So far: really good. The arrows soar. They're quite a bit slower than the darts due to the whole lift/drag relationship, but I'm very happy with them.
The RSCB setup is also very promising. I'll post some "official" ranges when I figure out a way to accurately measure them. The plunger in this thing is huge, so it's capable of moving a large amount of air very quickly.

WHy not use brass for the barrel, or copper? Anything to add on those last crucial feet.


I tried that, however, results with the 9/16" brass (which I thought was a near perfect fit for my darts) is proving to be both less powerful and less reliable than the CPVC (which is a tad too tight) for my darts.

I may play around with some different brass setups, perhaps with some tightening rings, nested barrels, or whatnot. But honestly, if it's not broke, why fix it?

Bump for updates on post 3, with finished product.
Video in the works.

#20 Fome

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Posted 19 July 2009 - 04:56 PM

Video:

Pew pew.

edit: RSCB can actually fit 5 darts, went with 4 for the video though.

Edited by Fome, 19 July 2009 - 04:58 PM.


#21 Bedhed117

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Posted 19 July 2009 - 06:01 PM

Dang man, those are the best home made missiles that I've ever seen.
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#22 TantumBull

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Posted 19 July 2009 - 11:14 PM

Nice. I'm liking those arrows. You should make a write-up (you may have mentioned you would be doing this, can't remember).

WHy not use brass for the barrel, or copper? Anything to add on those last crucial feet.

No barrel material is better than another. It all depends on dart fit. Although I suppose a slicker material may be better for something with a faster air release.

Edited by TantumBull, 19 July 2009 - 11:16 PM.

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#23 Fome

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Posted 20 July 2009 - 03:11 PM

Thanks Tantum and Bedhed.

The writeup for the homemade arrows are on page 1. Conversely, you can also follow the link in my sig.

#24 white moonlight

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Posted 20 July 2009 - 04:12 PM

Dude those missles pack a punch.

Also have you tried the gun with a regular RSCB, (not with the plug on the end)?
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VengefulWaffle BOY, 12 KILLED IN MOUNTAIN PASS BY WILD RACCON, EXPERTS SAY HE ATTEMPTED TO HOLD IT OFF WITH NERF NITEFINDERS
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Guess who he was talking about...

#25 Fome

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Posted 20 July 2009 - 04:31 PM

Dude those missles pack a punch.

Also have you tried the gun with a regular RSCB, (not with the plug on the end)?


Yeah, when I first started on this project. No difference in performance. The plug essentially turns the bottom T joint into an elbow.

I wanted my bow to shoot arrows though, as well as having an effective high-ROF backup system. Being able to switch between what is in essence a singled barrel and an RSCB gives me that option.


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