+Bow Rev.3 - Spring-Powered Nerf Rifle

Essential Tools
+ Band Saw or Scroll Saw

+ Drillpress or Power Drill

+ 9/16" & 5/8" size flat-blade wood-boring drill bits

+ Mitre Box & Mitre Saw

+ #6-32 Tapping Bit

+ Fine-Point Permanent Marker

+ Screwdriver

+ Half-Round Rasp

+ 300 grit sandpaper

+ Bolt cutters (for cutting spring)

+ Hobby Knife (to clean the edges of the sheets once cut)

+ Scissors

+ Inkjet or Laser printer

+ Packet of full-sheet label paper

+ Electrical tape

+ Face Shield or Safety glasses

+ Super Glue

+ Silicone Grease

+ Vice or C-Clamp

No other tools expressly needed. All tools listed are not easily substitutable. You can cut out the center of one part using a Scroll Saw or Coping Saw, and a Band Saw could be used to make the external cuts more quickly.

Part List

Download: bow3_partlist.xls

All items available through http://www.mcmaster.com

A full set of prices is included. Simply copy and paste the first two columns into the text box of the McMaster Carr "Build Order" page. All items on the "Grip" page are essential. The other two pages provide you with plunger tube options.

The "+bow" plunger and plunger tube have a 6.25" draw at a maximum of 35 pounds with a smaller working volume.

The "2-11" plunger and plunger tube have a 4.5" draw at a maximum of 29 pounds with a larger working volume.

The "+bow" has the higher range of the two options, but also has a heavier and longer plunger draw which maxes out at 29 pounds.

Download the cuttings template sheets: bow3.doc

Print them on full sheet label paper. The included legend will tell you what size holes need to be drilled where. Most of which are labeled with the bit size or tapping requirements.

There are two plunger tube options available, so select the size you intend to make and apply that extra page of labels as well.

The templates used for drilling the plunger tubes are only likely to
work perfectly for you if the plunger tubes you are supplied have a diameter matching the measurement used to make the template. So the "+bow" plunger diameter template was made for a 1.52" OD Aluminum tube and the "2-11" plunger tube was made for a 2.25" OD polycarbonate tube.

Any alternate material used to make your plunger tubes that has a different outer diameter will not be able to make accurate use of these specific templates.

An alternate material to use for making the "+bow" plunger tube is 1-1/4 SCH40 PVC pipe which has an outer diameter of 1.66".

Making your own templates of this type however is quite easy. You simply take the diameter of the tube you intend to use, convert it to its circumference, then divide that circumference by 4 and that's what you hole spacing should be measure out to on the outside of that material using a flexible measuring tape.

It's also worth noting that most "1/4" Polycarbonate sheets do not come in a thickness that is exactly 0.250", but rather measure at 0.230". This difference in thickness impacts the spacing away from the end of the plunger tubes that these holes need to be drilled to.

The "+bow" plunger tube you will need to use a mitre saw or a band saw to cut a 12"-long piece of the 1-1/2" OD aluminum tubing. After doing so deburr the edges of the tube.

The "2-11" plunger tube will need to be cut down to 8-1/2" in length using a a mitre saw or a band saw. The cut edges will need to be deburred using a box cutter or hobby knife.

Apply the appropriate template to your selected plunger tube ends. Make sure to apply these temporarily using tape and NOT BY USING the label paper itself. Tape will be easier to later remove, where-as the label paper can sometimes be difficult to get back off.

If the cut ends of the template do not come close to meeting each other or overlap too much then your drilled holes will not be spaced evenly at 90-degrees. The impact of this will be discussed later.

You can trim them apart to try to fit all the parts into the space available on the sheet you have, otherwise simply adhere the entire label set onto your plastic sheet after trimming off the edges.

Also apply the parts for the matching pump-action grip if you intend to make that as well.

Using a Hammer and a Center Punch (or a Nail put a centering divot on the centermark of ever hole on every part template.

Using a Drill Press drill all of the holes labeled as "#6-32" with a #36 or 7/64" drill bit.
Then drill all the unlabeled holes with a #23 or 5/32" drill bit.

Using a Drill Press and a 9/16" Flat Wood-boring drill bit
bore out all the holes labeled "9/16". Go slowly and carefully with minimal downforce to help avoid tearing the templates off the plastic.

Using a Drill Press and a 5/8" Flat Wood-boring drill bit
bore out all the holes labeled "5/8". Go slowly and carefully with minimal downforce to help avoid tearing the templates off the plastic.

Using a Scroll Saw or a Band Saw coarsely cut all of the parts free from the plastic sheet.

Add as many relief cuts as you think are needed. A relief cut is a
cut made perpendicular to the intended cutting line that allows excess material to break away as the cut is made along the intended contour.

Using a Scroll Saw or a Band Sawmore accurately cut all of the parts to their outlines.

Using a Hobby Knife deburr all the cut edges of the now mostly-finished pieces.

Using a Fine-Point Permanent Marker draw a line on the edges of the now cut parts whereever a dotted line meets the edge of the template.

Also mark a perpendicular line as close to the approximate center point of the edge of the piece.

Drill all of these new center marks with a a #36 or 7/64" drill bit.

Using your #6-32 tapping bit and a Tapping Wrench tap all of the holes you previously drilled with a #36 or 7/64" drill bit. If needed, lubricate your tapping bit with common dish soap.

Use Super Glue and a C-Clamp to glue together the three
plunger head parts that match your chosen plunger type. Make sure to line up the center hole on all three pieces as well as the "check valve" holes.

Set this aside to cure.

Remove all of the template labels and protective film from your plastics parts.

Do a test assembly of the Grip with the components as shown.

Using a Half-Round Rough File (Rasp) or Belt Sander or a Router soften all of the edges of the test assembly to suit your preferences regarding fit and comfort with your hand. Cut away and excess material as desired using a Scroll Saw or Band Saw.

Using 1/2" screws and the 1-inch long threaded spacers assemble the "V-Block" parts.

Use a few Zip Ties to clamp the "V-Block" onto the end of the plunger tube near the template.

The V-Block will help you keep the plunger tube stable so that you can drill the hole out using a #23 or 5/32" drill bit.

Rotate the plunger tube to the next center mark and drill the next holes, then repeat the process.

Slide the V-Block down to the opposite end of the plunger tube and repeat the process again.

For the "2-11" style plunger tube use a Mitre Saw or a Band Saw to cut the 1-1/4 SCH40 Pipe coupler in half along the mold seam.

Put two wraps of e-tape around the end near the cut, then slide it into the end of the plunger tube. Tap the 1-1/4 SCH40 Bushing adapter into the coupler half.

Use a #36 or 7/64" drill bit and a Drill Press to drill these holes into the PVC components.

Using your #6-32 tapping bit and a Tapping Wrench tap all of these holes. Then install 1/2" length screws.

You may want to use a 1-1/2" length screw in one of the holes as a safety measure to prevent darts from being suction-loaded into the plunger tube.

For the "+bow" style plunger tube wrap the 1-1/4 SCH40 bushing in 4 to 6
layers of e-tape until it fits the aluminum tube snugly. Insert it all the way into one end.

Use a #36 or 7/64" drill bit and a Drill Press to drill these holes into the bushing.

Using your #6-32 tapping bit and a Tapping Wrench tap all of these holes. Then install 1/2" length screws.

You may want to use a 1-1/2" length screw in one of the holes as a safety measure to prevent darts from being suction-loaded into the plunger tube.

Using a Mitre Saw or Band Saw cut the lengths of 1/2"
Plastic rod as specified by the cross-section drawings that were included with the template sheet for the plunger type you selected. Those lengths are.

"+bow" type: 4-3/8" and 7-1/2"

"2-11 type: 2-5/8" and 6"

For the Stock: 9-3/8", 9-1/4", and 8"

Use a #36 or 7/64" drill bit and a Drill Press to drill the centers of both ends of each length of rod. Also follow the dimensions listed in Template Sheet 4 to drill and tap the holes in the sides of the rods.

Using your #6-32 tapping bit and a Tapping Wrench tap all of these holes.

From the 5/8" OD Aluminum use a Mitre Saw, Band Saw, or a Pipe Cutter to cut: 2-1/2" and 1/2"

From the 3/4" OF Polycarbonate use a Mitre Saw or Band Saw to cut: 1-3/4" and 1/2"

Deburr all cut edges before continuing.

Fully assemble the Grip. Pcross2 should be the part from the plunger tube you selected.

Test fit your plunger tube over the Pcross parts, then use a Fine-Point Permanent Marker to label the hole locations on Pcross2.

Use a #36 or 7/64" drill bit and a Drill Press to drill these holes in the center of the edge of Pcross2.

Using your #6-32 tapping bit and a Tapping Wrench tap all of these holes.

Use a Vice or a C-Clamp to press the 1-3/4" length of 3/4" OD polycarbonate onto one end of the 2-1/2" length of 5/8" OD aluminum tube.

Install the combined piece into the Grip assembly. You may need to use the Vice or C-Clamp again.

Use your #6-32 tapping bit and a Tapping Wrench to tap all of those holes.

Use some Bolt Cutters to snip the head off of a 1-1/2" screw.

Use the now headless 1-1/2" and the 3/8" length spacer to assemble the two plunger rod halves together as shown.

Use a Vice or a C-Clamp to press the 1/2" length of 3/4" OD polycarbonate onto one end of the 1/2" length of 5/8" OD aluminum tube.

Install the combined piece onto the front end of the plunger rod and use Super Glue to glue it in place. Then attach the plunger head using a 1-1/2" length screw.

Once the glue has cured, add the correct size Ultra-Compressible O-Ring designated for that Plunger Rod type.

Remove the Frame2 part from the Grip assembly.

Slide the CatchPlate up into the grip assembly. You can use a rubber band on the outside of the assembly as a cheap return spring.

Or you can use an extension spring on a 1/2" (or longer) screw with the other end looped onto a 1-1/2" (or longer) screw held to Frame1.

Lastly install the Trigger using a 1-1/2" screw.

Attach the Middle Stock rod to Frame2 using a 1/2" length screw, then re-install Frame 2 into the Grip Assembly using four 1/2" length screws.

Assemble the rest of the Stock Parts onto the Grip Assembly as shown.

Apply Silicone Grease to the Plunger Head.

Install the Plunger Rod and Main Spring in the Plunger Tube.

Work the Plunger Rod back and forth in the Plunger Tube until it's fully lubricated.

Slide the assembled plunger tube onto the Grip Assembly by feeding the Plunger Rod through it while holding the Trigger.

Attach the plunger tube to the front of the grip assembly using 1/2" screws.

Install the Phandle onto the Plunger Rod using a 1/2" screw.

You are finished. Just add a barrel of your choice.