How to Make a Nerf H.A.M.P (High Air Manual Propulsion)

A nerf H.A.M.P is a really cheep (less than $5) nerf gun that does not use any springs, weights, pulleys, or pumps. The whole gun is made out of stuff you can find at a good hardware store.
I am a beginner at making nerf homemades... so bare with me.

Tools:

(Optional) scissors
Hacksaw, Dremel, pipe cutter, or anything else that can cleanly cut PVC (NOT CPVC)
Vice
Hot glue gun and hot glue
Rubber mallet 
Sand paper
(Optional) Flat, heavy weight
PVC cement (I also used a primer which I highly suggest)
Lazer level (or just use a lazer or a ruler)


Materials:

DUCT tape (NOT DUCK TAPE)
Lots of E-Tape (electrical tape)
2" inch PVC about 2 feet
(1) 2'' inch PVC coupler
1.5" inch PVC about 3 feet
1/2" inch PVC about 6 feet
(1) 1/2'' inch PVC ''T"
(2) 90 degree 1/2" inch PVC elbows
As many bushings as it takes to get from 2" inch PVC to 1/2" inch PVC
Nerf darts, Screamers work the best (Streamlines kinda don't work)
Cardboard
Pen
Some sort of Plastic/ Tape friendly Lube

 

Cutting the body:

The body (2'' inch PVC) should just be just long enough so your non dominant hand can still stretch forward a good 10 inches (look at the photo)


Plunger cutting:

I used a black 1.5'' inch piece of PVC
 
Cut on the longer side of your piece of PVC about three fingers down

You should have made marks of were you want things to be.... now go and cut those pieces

Remember, wear eye protection and always cut in a vice if you are using a hand-held saw.

Basically you want to cut out pieces of cereal box cardboard that are the same diameter as the outside diameter of the plunger.... Just look at the pictures

Using a hot glue gun glue all the pieces into a cylinder  

Do this by glueing one to another, squishing it with a weight until it's dry, and glue another one on top and squish it with a weight until it's dry. Repeat until all four are glued together

I used a giant, concrete book-end (look that up on google) to squish them all together

Once the plug is dry put a bead of hot-glue along the edge of the plunger and press it together until it is dry. It should be flush so there is no lip sticking out around the pipe.

Once you have done that cover it in DUCT TAPE so it is Uber held on.

To create the proper air seal you will need the wrap the very front part of the plunger in e-tape so it JUST fits into the body. After the electrical tape o-ring move down an inch and wrap that in DUCT tape so it also just fits into the body. Both o-rings should be the same width.

Depending on you hardware-store's selection of PVC fittings you may have to use quite a few bushings to get from 2" inch PVC to 1/2" inch PVC (like in the first picture of this page) I was able to buy a bushing that took me straight from 2'' inch to 1/2" inch! OH YEAH!!!!


The problem with the bushings is that you have to use a coupler to join the bushing to the 2'' inch PVC

Use a PVC primer on the OUTSIDE of the 2'' inch bushing and on the INSIDE of the 2'' inch coupler. Then put PVC cement on the INSIDE of the 2'' inch coupler and place the first (my only one) bushing into it and GENTLY tap into place with a rubber mallet. DON"T WAIT FOR THE PVC GUE TO DRY!! ! Continue to use primer and glue on all the bushings into place, GENTLY taping it  into place with a rubber mallet after each one is place in the last one. 

Finally primer and glue the coupler with all the bushings sticking out of the opposite side to the end of the body of the H.A.M.P

Sorry, no pictures.

To create this you need 2 pieces of 1.5 inch long 1/2'' inch PVC,  two 90 degree 1/2'' inch elbows, and that PVC primer and cement.
Simply glue one of the 1.5 inch long, 1/2'' inch pieces of pipe inside the two elbows, but make use the elbows are totally vertical (I did this by pushing them, on their side,  on a flat surface) JUST LOOK AT THE PICTURE IF YOU DON'T UNDERSTAND. 

Primer and glue in the other section of 1.5 inch long, 1/2'' inch PVC piece into an end of a elbow.

Cut a piece of PVC that is just longer than the whole gun at full draw.... Oh, just look at the picture because I am terrible about giving descriptions!

I wrapped mine in some e-tape so it looks cool.

As you might of seen in last step's photo I had a small piece of PVC on the main body, this is so I can have a modified PVC "T" on top.

To modify one of these (yes I know mine is not a "T" but oh well) you need to take out the old dremel ( or you could use a small file but that would take FOREVER! !!) and use a sanding bit to get rid of the ridges on the inside that prevent you from pushing one pipe all the way through. Once you have triple checked that some 1/2'' inch PVC will easily slip into the modified "T" it is time to mount it.

I am fortunate enough to have a lazer level (basically a fancy lazer with a level) so i just marked where I wanted the modified "T" to go and made sure it would live up with the PVC U we made earlier. I realized the "t" would be too low so my barrel would bend, so I put a small section of  1/2'' inch PVC in the "T" 

To make sure the PVC that will go in the T will stay in place i ground down the bottom so it was the same as the surface of the Body.

I AM TERRIBLE ABOUT DESCRIBING THESE KINDS OF THINGS SO PLEASE FORGIVE ME AN TRY TO BARE WITH ME :(

I used super glue to bond it to the body, after the super glue dried T filled the empty hole at the top of the 1/2'' inch PVC nub that fits into the "T" with lots of PVC glue

This gun reminded me of Dennis The Menace from Beno cartoons. He always wears a black and red striped shirt so that is the design I did.

I cover my fingers in Vaseline and rubbed them all over the Giant o-ring we made in step 6 and inserted the plunger back into the body and pushed and pulled on the plunger to coat the inside of the body, I pulled out the plunger again and covered it again in Vaseline and repeated about 2 more times. After I took some paper towel and wiped off any extra Vaseline on the outside of the body.

Hold the plunger and pull it out until the o-ring, then push back into the body quickly. Make sure not to trap your fingers!!!

Small H.A.M.P  (Firing test done with homemade stefans)

Average: 20 feet

Regular H.A.M.P (Firing test done with "Whistler" darts)

Average: 80 feet