CNC PISTON FOR SHORT STROKE 12T RETRO ARMS (RA-9422)

Piston made by CNC
in nylon gf30%
for 12t short stroke configurations
weight 12g

A specially lengthened, strengthened and significantly lightened piston, designed for short-stroke assemblies with up to 12 teeth.
The piston is optimized for retroarms gearboxes, but can also be used in standard gearboxes.
Before final assembly, it is necessary to check whether the piston can be fully cocked by the 12-tooth sector gear.
This piston differs from the standard piston because it has a longer body and at the same time adjusted dimensions of the guides, ensuring less leverage during a short piston stroke.
The rear is significantly reinforced to withstand the forces created by the use of strong springs in the TSG, DSG and SS groupsets (reaching force often around 19kg) in combination with rapid load changes due to high cadences, often even 60 rps.
It is this combination and timing, along with the forces of the ordinary pistons, that cause the rear end of the piston to break off and shoot the piston rack into the rear end of the gearbox.
The piston body is made by CNC milling in nylon with the addition of 30% glass fibers.
This material has excellent properties, in particular it is resistant to wear, survives high temperatures and pressures, tolerates the action of aggressive oils very well, is resistant to breakage and is also lightweight.
The nylon material used is oil resistant and although it is not absolutely necessary to lubricate the piston body guide grooves, we have integrated lubrication pockets at the contact point between the piston and the gearbox.
Despite the robust and extensive body, it was possible to keep the weight relatively low, which is very important for fast builds, namely 15.8 g.
We do not recommend enlarging the drain holes due to possible damage to the structure.
The weight of the piston may vary due to moisture absorption of the material.
However, we strongly advise against drying the piston, immersion in moisture significantly increases the strength of the material.
The piston rack is made of high quality spring steel by CNC milling.
The material used is flexible and at the same time, thanks to heat treatment, it is also hard, wear-resistant.
Although it is not necessary to glue the piston rack, some customers glue it (in this case we recommend a two-component epoxy glue) and for this reason we leave the racks raw (without surface treatment that carries a layer of oil) after the heat treatment, so they are no longer black, but dark gray and may have various colored spots.
Before installation, it is recommended to lubricate the piston rack, ideally with silicone petroleum jelly.
This piston has 12 teeth and is therefore suitable for use with e.g. pandora 13:1 ss12t (8010) gears