RamLock with Low Tension Highlines
It’s time to talk a little about webbing anchors and minimalist rigging practices. Slacklining has been undergoing some rapid changes in style these last few years so we figured it would be a good time address an issue that is surprisingly common; ineffective webbing anchors with minimalist rigging. SlackTech seems to be the only company putting forth and meeting the challenges of “how can we make a safer weblock” and “how can a weblock be incorporated into a simpler slackline rigging system.” Others tend to focus on building features into their weblocks that deviate from these modes of thinking. Common drivers seem to be, “how can we make the cheapest weblock” or “how can we make a weblock that is really easy to pretension” or “or how can we make the strongest weblock” or “what is the most creative thing we can do to a weblock.” This article is intended to shine some light on the ramifications of recent trends in rigging and define what a weblock is SUPPOSED to do; create a no slip and no flip, high functioning connection point for your slackline. Something the RamLock is especially suited help with.
Recent trends in slacklining (more particularly highlining) have been to do away with tension and to do away with pulleys. And although these trends are not necessarily a bad thing, there is rising concern that the supporting hardware and gear reduction practices are trending towards some very dangerous situations all in an effort for “style” and “sending.” We will start by looking at some of the complications that arise with a low tension slackline by looking at what the interactions between the webbing and the webbing anchor actually are.
Weblocks hold webbing in place because of the friction created inside the device. For the “single wrap” method, a bite of webbing is inserted into the device wrapping around the diverter and held in position with the front pin. This creates the “friction lock” as we have come to call it. The thing is, tension is NEEDED to create the friction inside the weblock otherwise the webbing is likely to flip around and/or slip under quite low loads. We have seen countless examples of this on slackline forums and have had much discussion internally about this issue. Slackliners can’t just put webbing in a weblock and call it good. TENSION is needed to create the friction lock with the single wrap method. If there is no tension, the webbing will slip, flip and effectively render that webbing anchor ineffective. Work-arounds like tying off the webbing, putting knots in the webbing to prevent slip, taping the webbing to the weblock to prevent slip... What’s the point of using a weblock if it doesn’t do what it’s supposed to do, which is to EFFECTIVELY anchor and maximize strength retention of the webbing being held?
To create more friction (which translates to more holding power) inside a weblock the methods of the 1.5 wrap and double wrap were created, but due to the studies performed by Andy Reidrich of LineGrip LTD using traditional banana style weblocks, the practice has almost disappeared. He found that significant mechanical advantage was being created within the device (most prominently in the double wrap method) causing an unexpected failure mode at moderate tension; a slip, causing a shockload within the device making the steel side plates warp under compressive loads causing a catastrophic failure of the device far below the stated breaking strength. The double wrap method was quickly shunned by many gear manufacturers and slackliners due to this study. Because almost all webbing anchors relate to this dated banana style design. The critical part to notice with this study is, Andy didn’t necessarily find a problem in rigging practices, Andy found a problem with the way gear was being made.
A weblock should not fail catastrophically. Steel is already known for being a poor choice of material for non-gusseted compressive loads, which is how almost every banana style weblock is made. Steel does well under tension. Tension in a typical banana occurs in the region from the diverter to the shackle connection, but that’s not to say tension is by any means uniform throughout the device. The RamLock is engineered to incorporate many geometric strengths; H beams, gussets, triangles and radii. It’s also made so there is practically no tensile loading in the device, it’s almost completely compressive. What we achieved with the RamLock is Kaizen – Japanese for “positive change.”
Link to Andys youtube video - coming soon!
Another common practice for highline rigging is to invert the main webbing anchor to allow esthetic alignment of the weblocks and allow for easier application of the Buckingham tensioning method. This practice of inversion is one of the worst things one can do with a weblock when using the single wrap method because it’s changing how the webbing leaves the weblock. When oriented properly the walking portion of the webbing is pressing down on the tail, maximizing the friction within the device. When the weblock is inverted, significant change in the webbings angle of deflection leaving the weblock occurs, thus reducing the total capable friction of the device. It’s like lifting the walking webbing off the diverter, effectively reducing the holding power making slippage more likely. Couple that with low tension and your webbing will slip. This practice of inverting the weblock should be stopped for safety reasons ASAP. We are getting to the point of having to reengineer how a weblock should function and how it can be used.
Fortunately, Ben Plotkin-Swing and myself, Jason Fautz did this exercise 3+ years ago when designing the RamLock. We looked at many of the “problems” that were present within the current weblocks and engineered solutions to those problems. One of the biggest complaints about the RamLock is the difficulty in pretensioning. Pretensioning was never a defined goal of ours because we already figured out that a webbing anchor that was easy to pretension was also more likely to slip. We decided it would be more important to focus on eliminating failure modes, safety and effective holding power.
We also addressed the side plate warping issue by manufacturing the RamLock as one solid piece and incorporating the top bar. The top bar adds rigidity to the side plate so that they are fixed together, not two separate side plates acting independently. This top bar also keeps the webbing from flopping out of the device under low tension which is a phenomena becoming more common with low tension slacklines. The top bar also maintains contact pressure on the walking end of the webbing so the tail is always held. This makes the inversion issue a non-issue because the webbing is held in place no matter what orientation.
6061-T6 aluminum was used instead of steel alloy. Aluminum is much more malleable than steel allowing deformation of the side plates when overloaded in compression. The failure mode on a RamLock is much different than a banana style design. The pin is slowly pulled towards the giant diverter and “mushrooms out” the aluminum along the way. It is a slow process and is visible when occurring. It also starts happening when a load occurrence of 10,500 lbf (46 kN) is experienced in the guested region. The RamLock has a detectable failure mode and it is not catastrophic, totally unique for the industry and it’s a good thing. So go head and use the 1.5 or double wrap method with the RamLock on low tension highlines. It works particularly well with thinner, high stretch webbing. Super static webbing has the greatest load transfer back to the anchor. If you see any signs of the pin hole becoming elongated or bigger than the ½” pin diameter, retire the RamLock.
As a community we need to be designing gear and developing methods that solve real problems, not creating gear and using rigging materials/methods that create more problems. It’s really a concept that should be embraced within the art and practice of slacklining in general; Kaizen – Japanese for “positive change.” We also need to start looking at the highline as an entire system, not just a series of individual, stand-alone components. When one can look at the entire system, see it flow as one, can understand it and demonstrate critical thinking skills; that’s what brings a slackline Jedi to Master Jedi status. A capable slackliner with the proper awareness to see highlining for what it is, an engineering problem. Taking a complete look at the entire system will become increasingly important as new technologies emerge and we dream up new adventurous challenges. It should be the goal of every slackline gear designer, manufacturer and advocate to allow the slacker to explore the limitless potential that is slacklining while keeping them safe and aware.