This is my first writeup, so be nice.
This propulsion system uses two nested tubes (I usually use 1.5” and 2” PVC) of no particular size, duct tape, cardboard, and yarn to produce a large low pressure blast of air. With long ( 3’ ish) airgun-fit barrel material it vacuum loads and fires well, regardless of how many darts you put in the barrel. I've been making them for about a year and a half, found the internet nerf community about 6 months ago, and feel its about time I did a writeup. I did a dick-waving video earlier that features some HAMP guns here:
And I built/played with a ridiculously oversize HAMP with at Ryan McNumbers mod party, documented here:
And here's a pic of most of my HAMPS in a pile:
And a writeup on a couple blasters that use the HAMP:
2” PVC (~18 in)
1.5” PVC (~18 in)
Yarn (fluffy is good)
1. Cut the 2” PVC to length X+2, where X = stroke. I use about 12” normally.
2. Cut the 1.5” PVC to length X+4”, or X + whatever amount of PVC you want to use as a handle, or attach a handle/linkage.
3. Cap the 2” PVC however you want, but a cardboard cover/duct tape cover (See #5) will be easier to work with later than the regular endcap if you want to maximize stroke/minimize deadspace.
4. Cap the 1.5” PVC with something that easily clears the entrance to the 2” PVC. Standard endcaps will not work, so I recommend the cardboard/duct tape cover (See #5).
5. Duct Tape / Cardboard End Caps:
a. Cut out a circle of cardboard for both the inner and outer diameter of the tube you want to seal. Go slightly undersize for the inner. (Exact size could work if you are perfect in 5b.
b. Attach the inner (small) circle close to the center of the outer (large) circle. Glue is good here, since you don’t want to affect the diameter of the circle by taping over it. But, you CAN just use a mini-loop of duct tape.
c. Put the cardboard on the end of the tube. If you have a voluminous glue, like elmers, wood glue, or gorilla glue, its very handy here--Put it on the inside corner between the small and large circle, and you won’t have to worry about seal in 5d and 5e. The glue isn’t for strength.
d. Put thin (<1/2”) strips of duct tape tightly over the cap. If you did not use glue in 5c, you need to get something close to a seal here—Do this by going in a spiral, with each strip overlapping the previous, until have covered the endcap (180 degrees).
e. To complete the seal, and keep the end cap from peeling off, place a final strip of duct tape around the perimeter of the endcap / PVC interface, on top of the existing strips of duct tape. Thicker strips of duct tape will make it stronger, but I’ve done fine with ½”. Make sure that this tape extends slightly past the end of the cylinder. More winds adds strength, but if this is a inner/plunger cylinder, you probably only have room for a couple turns.
f. Cut and remove the duct taps strip ends sticking out past the ring of duct tape. A steak knife works extremely well for this, and other cardboard/duct tape/mixed material cutting jobs. I recommend keeping one in your crafting arsenal, since you don’t want to switch between using the knife for duct tap and using the knife for steak.
This post has been edited by KaneTheMediocre: 24 February 2010 - 09:57 PM