The Cobra 4120 Series motors are built with 6mm steel shafts that will last through countless hours of flying fun, but occasionally, on a "Less than Perfect" landing, you may bend or break one. For these occasions, we offer factory replacement shafts for all the Cobra Motors.
The shaft kit for the Cobra 4120 series airplane motors includes a new shaft, which measures 5.98mm in diameter and is 74.5mm long, along with a new C-Clip to hold the motor together. The ring groove for the C-Clip is cut 18mm from the back end of the shaft. The shaft kit will also fit other brushless motors that require a 6mm shaft of this length. The shafts can be cut shorter with a Dremel tool and a cut-off wheel if necessary to fit other motors.
The shafts in the Cobra motors are a slight press fit into the aluminum front housing. The shafts will not just slide out when the setscrews are removed. They need to be pressed out in a bearing press, or in a drill press, with the front housing of the motor supported in a block of wood to prevent warping the front housing. Never tap the shaft out with a hammer! The shock induced can bend the motor parts and knock the glue joints loose on the motor magnets.
If you are unsure about how to change the shaft in a motor, you can watch the How To Change a Motor Shaft
video that we have on YouTube.
For more information about this product and the rest of the Cobra Motors product line, please check out the Cobra Brushless Motors web site.