- A plastic piston head for springs up to SP150
- This piston head is fitted with two high-quality O-rings (one guiding and one sealing)
- 11 counter-pressure holes with proportional geometry for perfect tightness inside the cylinder
- A ball bearing for problem-free spring operation
- A special screw connection between the piston head and piston via a thread placed on the bearing's flange made from aircraft-grade duralumin
- The weight of the piston head only is 3 g, the weight of the complete assembly with the bearing, flange and bolt is 9.1 g
- Made from high quality POM-C plastic, which offers very low friction coefficient and high stiffness
- O-rings made from NBR 70 sh rubber
- Made in the Czech Republic
- 1 piston head with fitted guiding and sealing O-rings (16×1 and 19×2.5)
- Additional guiding and sealing O-rings for cylinders with wider inner diameter (18×1 and 19×2.65)
- 1 axial bearing
- 1 bearing flange with thread for the piston head mounting bolt
- 2 high strength bolts (M3×16 with Phillips and Torx heads)
Low weight, high strength
During the design phase of this plastic piston head, we set two main criteria – low weight and high strength. In order to achieve the low weight, the mounting bolt of the piston head is inserted from the front of the head. The thread used to secure the piston head is not inside the head itself, but rather on the flange of the piston head's axial bearing. Otherwise, the thread would have to be cut into the plastic material of the piston head. This would not be a good solution for repeated mounting and dismounting. Alternatively, we could have used a duralumin threaded insert inside the plastic, but this would increase the weight of the head, which would then negatively impact the performance of the part. We decided to choose the most optimal solution.
Advanced geometry of the counter-pressure system
The piston head uses the so-called counter-pressure design – an established contemporary standard. Regardless of that, we were able to push the proven design a little bit further.
The EPeS piston head features 11 air intake holes for the sealing O-ring. The placement of these holes has been selected to maximize the flat surface in contact with the piston head's impact rubber pad, while keeping excellent compression attributes. The larger the functional area of the impact rubber pad, the more effectively the impacts are absorbed. This results in quieter operation of the gun and also increases the pad's longevity.
The edges of the EPeS piston head intake holes are rounded to an ideal aerodynamic shape for efficient air intake towards the sealing O-ring and for the disruption of sharp transition between the flat piston head's front side and the hole's inner cylindrical surface. This sharp corner transition is, in most cases, the reason for rubber pad damage.