Internals….. The Functionality of a Piston.
January 30, 2013
Gears are one of the important aspects inside a gearbox. Next on the list is the Piston. The piston is what formulates the initial compression of the gun, along with other parts such as the spring, cylinder, and more.. The piston is what the gears will catch on to, allowing the spring tension to increase as the piston is pulled back, and then released to generate the compressed air inside the cylinder. The compressed air is then used to propel the projectile forward.
There are different types of piston on the market. From those you see in stock guns with more of a plastic body to those made out of Polyoxymethylene (POM) and some with a full metal body. Keep in mind though, the heavier the piston, it would required more time and more energy to pull the piston back after every shot. You will need a stronger motor with a higher voltage battery to counter this. Also, you have the option of choosing full metal teeth or just have the very last tooth to be metal. Whatever you choose, it is important that the last tooth on the piston that the sector gear releases has to be metal. Otherwise you will be stripping pistons constantly.
Upon my experience of opening and working on different gearboxes, I always see people using the POM type piston since they have a high strength-to weight ratio. Airsoft GI sells POM Pistons from Magicbox, which are a great buy for the money. Metal Pistons are great for DMR rifles in my experience, because the rifle will need a strong piston for the heavy tension spring and torque gears. For other gear sets such as the Dual Sector from Siegetek or the Double Sector Gear from Modify, you will need a piston with at least 10 Metal teeth. The body does not have to be metal, just the teeth do. Since there are only 8 teeth being contacted on the piston, you need the release tooth to be metal. Modify has created a piston called the Quantum Piston, which every tooth is coated with titanium to increase the durability and the life span of the product.
In my experience, I always aim to look for the strongest piston with the strongest teeth that will hold up in my builds. Now, I know what you guys are thinking, if I wanted the strongest, that would almost mean that the piston was initially going to be heavy. Yes, initially. However, I would always decrease the weight on any piston by either drilling holes or cutting slots with a dremel. With a lighter piston, it would take less energy from my battery and also reduce the amount of strain on the motor and gears. Lastly, I would correct the Angle of Engagement (AOE). In order to do this I usually use a Sorbothane pad from Scatterplot. To install the Sorbothane Pad you have to remove the initial rubber padding on the cylinder head and then us a form of epoxy to adhere it on to the cylinder head yet countering the lubricants that spread as the piston moves. The type of thickness varies on what parts I am using. However, any plastic washers placed between the piston and piston head are just fine in doing so. Adding these spacers will push the piston back to certain millimeters for proper engagement. When correcting the AOE, the angle of the first piston tooth has to be equivalent to the angle created from the point of contact on the initial tooth from the sector gear. Correcting the AOE would increase your piston life and durability over time. Too much AOE or not enough AOE will decrease your piston life rapidly. I personally have put over 45,000 rounds through my Noveske M4 with an output of 348- 350FPS at approximately 40BPS on an 11.1v 1100mAh 15C LiPo battery and my piston only shows minimal wear.
Airsoft GI has vast assortment of pistons at different prices that you will find to your likings. From OEM replacements to the stronger POM pistons, there are always something out there for whatever you need in your gearbox. I would recommend having a professional technician, such as the techs at Airsoft GI, install certain parts in your guns, unless you are tech savvy enough to do it on your own. Stay tuned to our blog for the next article in this internal lineup. Have fun and be safe when you play airsoft. I’m Marq. See you guys around.