Ripcord Pins, Do you know the difference?
Do You Know the Difference?
There are two kinds of ripcord pins: Terminal and Intermediate. Both begin as a piece of steel rod about .127 ” diameter. They are cut to length, then the blade portion of this rod is rotary swaged to a diameter of .093. The other end is drilled to an ID of .093″, and a depth of about 1.5″ (inches). The pins destined to become terminal pins, are then trimmed and finished. The pins which are to become intermediate pins, are offset stamped and re-drilled – this time drilling through the newly formed offset. These pins are then trimmed and finished.
The process for mounting each of these pins to the cable is similar. Each is threaded onto the cable then swaged or crimped to the cable. The terminal pin is then ready for inspection. The intermediate pin can have excess cable protruding from hole in the end of the pin used in the terminal position, which must be ground off. This excess cable is ground off until it is smooth and even with the edge of the pin. This smooth edge is then observed for alignment between the OD of the cable and the ID of the pin. There is no visible demarcation of these surfaces, they appear as continuous.
The required inspection is to pull test the cable against the joint for 300 lb. for 3 seconds. The reason for the 3 seconds is that, it is recognized that this kind of joint can slip when held to a load over time. A crimp which is sub-standard might hold the load for 2 seconds, then fail, or it might hold for 3 seconds and not fail, but move enough for it to fail the next time it is loaded. After the pull test on the terminal pin there is no inspection method to verify to the world that the joint has not slipped during testing. You could pre-mark the cable but the mark could be off location. Later in the field, if the cable has slipped, there is no way for the rigger to confirm the integrity of the joint.
The intermediate pin on the other hand can be verified, and is in fact rejected for any microscopic movement which would disrupt the alignment described as observed, after grinding.
In my 30 plus years in the sport I know of three ripcord pin failures. The first involved an over- swaging on intermediate pins causing stress cracking and splitting from this excessive cold forming (See Poynter Manual 6.15.1). This defect was visible and could easily be detected. The other two failures were on the terminal pin. One occurred at Para-Gear in the early 70’s during a demo to a customer of a new Style Master Chest reserve. It had been packed with stuffing to simulate a full container. The salesman pulled the ripcord and the pin stayed in the cone, coming off the cable. I had one of these reserves and my ripcord was recalled and replaced with one with intermediate pins. No official recall was ever issued as it was a new product and all units were easily found and corrected. The other failure occurred on a Rigging Innovations product, Service Bulletin #1503. A rigger assembling a new rig found the pin unswaged. The corrective action for this was to inspect visually for the crimp marks and to pull test the pin to the cable with your fingers. The FAA specification for this joint was 300 lb. for 3 seconds.
The choice is yours, as an informed buyer you now have the facts to purchase based on knowledge, not hype about how many people or events the company sponsors.
John B. Sherman