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This is an update on the state of the Alpine WebLock 5 front pin with serial number W19ZZ. We have found that there is a possibility of the front pin disassembling itself under normal usage.
As we have studied the problem in greater detail, we have found the following:
The pin design is unique in that it lacks a shoulder at the base of the handle. This shoulder functions normally as a barrier between whatever the pin is attached to and the handle. This lack of a shoulder causes the pin handle itself to rub on the body of the weblock if it is spinning.
The assembly of the pin requires that we screw the handle onto the pin rod with a normal, right-handed thread. The threads on the handle and shaft are a course thread measuring roughly 6mm in length.
The cord that helps keep the pin with the device is spliced onto the base of the pin handle with a very low stretch Dyneema rope with a very tight Brummel splice.
When the pin rotates, this cord will wrap around the pin until it is taught, which then, if the Brummel Splice is tight enough, causes the pin to stop rotating.
When pulling slack through the weblock, the webbing grips onto the pin and the pin rotates in a clockwise direction. While the pin rotates, the bottom of the pin handle rubs against the body and the retention cord wraps around the pin. Once the pin has rotated enough and the retention cord is taught, the pin will likely stop rotating. However, if webbing is still traveling through the device, it will continue to apply torque on the pin shaft against the pin handle.
Now, the only thing preventing the shaft from unscrewing from the handle is the LocTite that was applied to the threads during assembly. If the tension is high while slack travels through (i.e. during tensioning), this can put a very large amount of torque going against that LocTite. Basically, the perfect storm for the pin handle to unscrew and fall off the device, removing all security on the installed webbing.
This is definitely a huge oversight on our part in the design of the pin.
We have totally redesigned the front pin of the weblock and will be providing every weblock owner with a replacement. The new pin has the following design specs:
- The pin handle is now a more traditional flat top handle with a single hole in it for a retention cord
- We will use an elastic cord tied to the pin hole with a stopper knot, allowing the cord to rotate as the pin rotates
- At the base of the pin handle is a stainless steel shoulder, providing a barricade between the weblock body and the base of the pin handle
- The assembly of the pin requires a left-handed thread to attach the handle to the rest of the pin (thus causing the pin handle to tighten on the pin shaft if the issue were to reoccur)
- The threads on the pin handle and pin shaft are moving to a fine thread, giving a higher thread count, providing more surface area for the LocTite to adhere
- Red LocTite will be used to lock the handle onto the pin shaft
- In addition to LocTite, we will install a spring pin between the pin handle and pin shaft in order to prevent any rotation between the two pieces
Now, with the new pin installed, when slack is traveling through the device, the pin will continue to rotate in the clockwise direction. However, if the cord wraps around the pin and locks the rotation of the pin, the torque caused by the webbing traveling through will only need to fight the elastic resistance of the cord. If that is too strong, the torque will only try and tighten the pin shaft on the pin handle. However, the spring pin will prevent any relative rotation between the pin handle and pin shaft.
With this updated design, we have eliminated any possibility for the pin to disassemble under normal usage.
We are asking all purchasers of the Alpine WebLock 5 to fill out the following form (very short):
We just need your name, order number that had the weblock on it, and shipping address. We will be sending out the pins with retention cords once they arrive in 4-6 weeks (after we test them, of course).
We will provide instructions for removing the old pin and installing the new one (very easy).
We will then require all customers dispose of their original pin. This is absolutely necessary to ensure the safety of the device. We cannot allow anyone to use the old pin any longer as it poses an extreme security risk, particularly when used at height. PLEASE, THROW AWAY YOUR ORIGINAL PIN!
Now, having dealt with this issue regarding the front pin, it has occurred to us that we need to audit our Research and Development protocols as well as our Quality Control protocols in order to prevent this sort of thing from happening again in the future.
For this particular project of a new front pin on the weblock, we will be doing the following tests once we have a sample:
- High Tension tensioning - we will setup a small slackline in our test machine and pull slack through the weblock to as high of a tension as we can and make note of any changes in the pin. We found that high tension tensioning exerts a LOT of torque on the pin, which has exacerbated the issue above.
- We will repeat the above test, making sure that the cord wraps around the pin in an unfavorable way, replicating the current issue as best as we can.
- The plier test - Using a set of vice grips and a pair of long-handle pliers, we will attempt to remove the handle from the pin body. This test was used on the current pins and removing the handle was quite easy.
- Standard weblock break test - We will break a few of our AWL5’s with the new pin installed using the standard ISA weblock break test protocol, making note of any changes in the pin.
If you have some ideas of other tests that we should run on this, we would love to hear them!
For projects beyond this pin replacement, we will step up our testing and vary the configurations and protocols as much as we can to attempt to alleviate any potential issues that may occur in the field. This is obviously a broad statement as the testing and safety measures vary from product to product. However, we will do our due diligence and test all configurations we can imagine for any new product development we enter into.
Batch testing will continue and be more rigorous than before as well. We will be adding the above test methodologies to our batch testing protocol for the weblocks and will amend all other batch testing protocols to be just as rigorous.