The following is a reply directly from Phillip Kelley the author of the article. He asked me to post it as he chooses not to be a contributor to online forums as it can be time consuming. I put his words in red so that all would understand I am quoting an e email he sent me directly. My comment are in black at the end.
Thank you all for your feedback and responses. I always learn something from feedback in whatever form it comes in. I would like to clarify a few points so we can continue this discussion in a positive way
The picture of the sling being used on the Safebloc was only 1 of the configurations used for attachment. As stated in the article the drops that referenced in the article and on which the data was based were done with a 3/4 inch tRex spliced to the safe bloc and performed on a drop tower. I apologize for this picture being used and therefore misleading people to believe that this is how all the testing was done. I did some drops with different slings of various levels of elongation as way to test how much energy is dissipated in the sling and how it affects cycles to failure. These drops were designed to destroy hr sling not test the equipment. This specific area was not the topic of the article so I did not include it except for the the pictures which in hind site was a mistake TCIA was left to choose pictures on a criteria other than the testing referenced in the actual article. The sling failure data did not affect the information given in the article as to whether or not aerial friction affected load force.
I went to Sherrill Tree website, whom I ordered the Safebloc from and took screen shots of the product info( see below) there is no mention of WLL or the fact that the device should only be used with one specific sling construction.
As it has been stated here and on there on line forums the Safebloc has a WWL list of 27oolb. The initial lack of information on my part did not effect the testing, nor does it effect the performance of the safe block. I mentioned it in error and again apologize. Nor was it the purpose of the article to address sling configuration and possible problems. Hence, the lack of research into that subject prior to testing.
The reason for the testing is that people I come in contact with at NATS training programs or TCC events or other things I am involved with (3-5000 + per year) asked questions about these aerial friction brakes and want more data on them. Typicaly I direct them to the manufacturers' websites to for the data they seek. Repeatedly they inform me at subsequent meetings/trainings/events that there is little to no data on line to answer their questions. That is the motive to conduct this type of testing. It is done on a completely voluntary basis with no financial influence from manufacturers, distributers or people who would benefit from the results. If anyone feels that the process is convoluted or with ill intentions, then get involved and help find solutions to the questions that end users are asking. "Remember no one is smarter than us all." and if anyone has constructive information that would prove to be helpful, please pass it along.
Respectfully,
Phillip Kelley
THESE ARE MY COMMENTS FOLLOWING
All in all I fail to see the reason for the excitement/detractors. If you disagree with some points in the article, then simply state your objections clearly and with contextual background. There is always room for discussion, disagreement and debate. In fact, I often look forward to it as it can force me to see things in a separate light or from another point of view. As Phillip stated there were some photos out of the context of the the article included. Only an apology can be offered for this oversight. In the end the pictures do not contradict the summary that the rigging wrench and the safebloc performed well within their design parameters.
The questions Phillip and I along with the other NATS Trainers are constantly asked when it comes to aerial friction devices: Does it work? (as in displace force) Does it tear up my rigging line? How does it compare to using a block? (incidentally there are the same questions we are asked about branch union rigging. (i.e no block or device at all)) Those questions were the basis for the testing. Those were the questions answered with the caveat that this was just one testing scenario performed by limited number of climbers in controlled circumstances. A necessary caveat implicit in all testing outside of normal production tree care for obvious reasons. There is no reason under normal circumstances to push the limits of any rigging system (tree included) to the edge that is often done on a drop tower or under controlled in field situations. However, doing so does glean insight and accelerate the action of the forces involved helping to answer the initial questions.
The information is then left to the reader to discern and take appropriate action as to his or her specific situation, rigging style and tolerance for risk. That is what I do. I am capable of forming my own professional judgments. I appreciate the numbers to help me do that.
Tony
