Pages

Thursday, October 11, 2012

Direct vs. Reverse Plunger Design


Science:
Spring-powered blasters use one of two designs to transfer the spring power to the back of the dart--direct or reverse plungers. Direct plungers empirically yield better ranges than their counterpart. Why are direct plunger blasters better? The #1 reason is dead space. Dead space refers to space that air occupies in the plunger system that is unused. Essentially, this air and space has little to no effect on power generation and is a waste. If you look at the direct plunger, you will notice that all of the air gets pushed into the dart by the green plunger. The reverse plunger setup, on the other hand, wastes half of its usable air volume. When the reverse plunger is all the way forward, you can see that there is still a LOT of air that could have been pushed out!

In addition to having minimal dead space, direct plungers are usually bigger. With a reverse plunger, you have to make room for the reverse plunger as well as the plunger tube. Some reverse plunger blasters have a "bulge" in the back of them (like the Recon) that is just extra space for the reverse plunger to occupy when you prime the blaster. Direct plungers can have the plunger tube hog all the space inside the shell while the plunger rod sticks however far out the back. A couple of examples would be the Nite Finder and the Crossbow.

Another minor  reason the power is a little better with a direct plunger setup is that the airflow isn't disrupted by flowing from a bigger tube to a smaller one. Direct plungers provide a nice straight path for the air to travel down, while air at the edges of the reverse plunger is turbulent because it hits the "lip" of the smaller plunger tube.

History:
Before the Elite series, Nerf decided that it would be a good idea to switch to reverse-plunger blasters. This included the Alpha Trooper, Recon, Raider, Longstrike, and Spectre. This meant a minor drop in power for stock blasters and a major drop for modded ones. Before this, pretty much everything was direct plunger. The very first dart-shooter, the Sharpshooter I, had a direct plunger! Fast forward to today, and the Elite Series is finally back to the old ways. Woohoo! Hasbro listened to the cries of anguish from the modding community. The power gains are minor since the plunger tube sizes remain nearly the same, but the Elite 75-foot ranges are achieved through the elimination of dead space and a great seal with the O-ring plunger head.

Hopefully this shines some light on the the differences between two fundamentally different springer designs. Thanks for reading!

~T da B

2 comments:

  1. A much better explanation than that on the so-called Nerf Wiki, which is so much dead space. The terminology the modding community adopted for this part is confusing from the get-go. I expected a reverse plunger to be traveling toward the back of the weapon when released. I would have called these piston and sleeve types.

    Anyway. Thanks for a succinct and accurate description of the two different mechanisms.

    Do we know why Nerf decided to try the "reverse plunger" given that the piston type is easier to make?

    ReplyDelete
    Replies
    1. Thanks for the feedback! I totally agree with you on the confusing nomenclature. I'm not entirely sure why Nerf went with reverse plungers but I have my theories:
      1. They wanted less power without making things too easy to prime
      2. They wanted to prevent modded blasters from hurting people

      I'm amazed they did it considering the increased cost of manufacturing!

      Delete