RamLock Load Tests

Abstract/Purpose

When looking at the strength of a weblock, two aspects come to mind; overall strength of the device and webbing strength retention within the device. Because the RamLock (RL) has unique loading characteristics, we found that the previous methods for load testing (putting a spanset in the device and pulling to device failure) was giving artificial results. We designed 2 tests that look at the two main failure modes of a webbing anchor. The tests were intended to answer the following questions; at what load does the device start plastic deformation and at what loads do different types of webbing break at. The tests conducted were the closest we could get to actual use conditions while maintaining a degree of control. We used this data to create the WLL and MBS of the RamLock.

Additionally, we do not agree with the test method of putting a spanset in the device and pulling to failure; as described by others. It is not an application specific test and should not be used to test and rate slackline webbing anchors. Our informal test showed that the RamLock would not deform until about 17,000 lbf. when using a spanset.

Procedure

RamLock Failure

To determine the failure point of the RL we used a single piece of 1” wide Balance Community SpiderSilk webbing with a stated MBS of 15,000 lbs. We used the same piece for repeated tests. Both ends of the SpiderSilk were connected to RLs via a 1.5 wrap (see Fig. 1). The tension side RL was used repeatedly for testing. The static RL was changed out for every test.

Figure 1 - 1.5 Webbing Wrap

Figure 1 - 1.5 Webbing Wrap

Webbing Break Test

It’s known that all webbing anchoring devices compromise the webbing in some way. We tested 4 types of Balance Community webbing; Type-18 MK2, Aero, Mantra MK3, and BC tubular. Small sections of new webbing were cut to approximately 3 ft in length giving us 3 samples for each webbing. Each end of the webbing was loaded into a RL using the 1.5 wrap technique. When loaded the RLs were positioned so that there was between 2.5 and 4.5 inches of space between the nose of the RamLock (we tried to keep this as consistent as possible in case stretch was somehow a factor; referred to as bar to bar dist. in data) The RLs were connected to the test machine using Green spansets in a U-basket configuration. Webbing was pulled until failure.

Results

RamLock Failure

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Note: No catastrophic failure was experienced. The failure mode suggests that the pin will be pulled towards the diverter and eventually create a mushrooming effect due to compression. This mushrooming effect will eventually sever the webbing. Informal tests show this happening at around 13,000 lbs.

Webbing Break Test

 
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Note: More insight into webbing behavior can be derived from the individual test reports such as slip points. More testing needs to be done industry wide.

Observations and Other Notes

RamLock Failure

One of the astonishing things about the RL is the fact that is does not fail catastrophically. This failure mode is unique in the industry (from what we can find). Most commercially available webbing will break before reaching the upper limits of the device. Shock loading has one of the most detrimental effects at higher loads. A slip occurs when the webbing friction lock slips and re-catches creating a higher peak force. On the RamLock, the

Typical Failure Mode

Typical Failure Mode

Webbing Break Test

There is much to learn about the interaction of webbing and its anchoring device. Each webbing has its own unique properties but we found those with ample stretch and fine weave (Type 18 MK2 and tubular) fared better in strength retention than lower stretch webbings. The worst performer was Mantra MK3. It has a huge weave and is a low stretch webbing. It is also one of the heaviest webbings available. Spidersilk (Vectran webbing) was cut by the device at about 13,000 lbf.

Sample B of Type 18 Broken.

Sample B of Type 18 Broken.