It’s all in the timing

One of the people who joined us during our treemagineers meeting this week was Elliot Tanner, a very talented designer, who is in not small part responsible for the look and function of the tools whose development we have been involved with.

We had a very interesting discussion regarding the timing of locking mechanisms on karabiners, which I thought I had an understanding of – it turned out this was not so. I love learning and understanding things better, it feels a bit like peeling back layers, gaining deeper understanding with each layer you remove. This is especially true of complex issues – and designing and manufacturing PPE without a doubt is complex.

Pic: Rob Fisher

What is crucial for safe and correct use of a connector is a functioning locking mechanism. This relies upon a number of factors.

Auto-locking gates, such as the one on the Locksafe Ultra O pictured above, rely upon two springs in the barrel, a torsion and a compression spring, to rotate the barrel through the movement and to push the gate closed. I was under the – wrong – impression that when someone talks about a timing issue on a gate preventing it from closing correctly, that this is linked to one of these springs being faulty. This is not so.

Timing refers to a purely mechanical process, somewhat analogous to a computer script, which sketches  a pathway that the locking mechanism follows from closed to open state. This relies upon very specific surfaces and contact areas which interact with each other during the movement.

In the case of the barrel of the Ultra O pictured above left, the barrel butts up against the lower hinge rivet. This limits the distance of rotation. Once the barrel has been rotated into this position, the gate can swing open. During this swinging motion, a tab on the lower part of the barrel prevents the barrel being able to inadvertently turn back into the lock position (pic above, right), due to the way it interacts with the flat surface area below the rivet. This is important, as otherwise, if the locking mechanism did swing back towards the closed position with the barrel already in the locked position, it would prevent the karabiner from closing and locking correctly, remaining in an open position.

The interaction between the nose and the gate is also part of the timing mechanism.

You will have noticed on the Durolocks that there is a very long spike-shaped tab on the lower part of the barrel. This also has to do with timing.

Because the purple barrel is relatively far out from the gate, this point has to be long, so as to remain in contact with the flat plane below the hinge rivet to ensure correct timing and again, to not rotate around in the depressed position.

Over-rumbling (the process where all sharp edges are removed from the karabiner bodies by rumbling them in a tub of ceramic elements) can cause surfaces to become too rounded and cause timing issues. For this reason, some manufacturers choose to machine these surfaces to ensure a clearly defined area of contact and correct timing.

Wow. Heady stuff.

It certainly makes me look at the Durolock gates, a highly complex locking mechanism with a barrel within a barrel,  in a new light. In fact, it makes me look at all locking mechanisms in a new light. So often we take things for granted, never considering the time, ingenuity and effort invested to ensure consistently reliable function.