Setting up the Timber Tripod
With the current economic crisis in the country and other countries, fire departments are cutting cost where the can. Normally the training budget is first to go and then comes the equipment budget. There are various companies that have premanufactured tri-pod systems for example, DBI, Skedco, Arizona Vortex, and the SMC/PMI TerrAdaptor to name just a few. Now, these are all great products and they have their place in the rescue environment. But not every department can come up with the funds to purchase such equipment. So that means we need to go back to the basics of rigging. In this second part of The Fundamentals of Timber Rigging, we are going to go over the process of constructing the Timber Tri-Pod.
The amount of equipment needed to achieve this maybe more that the average pre built commercial tri-pod system. First of you need to decide what size of timbers are going to be needed. Most timbers for the tri-pod are going to be 4x4x12’. You can go with 6×6’s or 8×8’s, but they can be heavy and are normally used in lifting heavy objects during a structural collapse. We are going to be rigging up a Timber tri-pod for use in a confined space environment used to lower or raise rescuers and or victims. Next you will need 30’ of ½ inch life safety, 12’ of 2” webbing, and assortment of carabiners and tech cord, all rated for life safety.
To assemble the legs of the timbers, you need to make sure the tip is elevated to allow you to lash the timbers together (normally this is done with saw horse or the back of the apparatus) using the 30’ section of ½ life safety rope. You start off by placing all 3 4x4s side by side leaving a 1.5” or 2” space in between the timbers (normally with using 2x4x2’ slats to achieve this) to allow the lashing to pass through. Next, you would want to make sure the corners are smooth down (this is done by rubbing the corners with a rod or beating the corners with a 3lb hammer) so as there is no damage done to the rope in the assembly process. Once the corners are smooth down, you need to measure down 36” from the top of the shortest pole. This will be your starting point. (Keep in mind timbers shorter than 12’ will reduce the amount of height need to raise or lower your rescuer/victims). Next take your 30’ lashing and start with a clove hitch on one of the outside legs. Next take the rope over and under the three timbers in a figure-of-eight fashion. Make at least six turns, working upward. (This is called figure of eight lashing). Once the six turns have been completed, then make two frapping turns between the first and second timber, and two frapping turns between the second and third timber. After the frapping turns have been completed, secure the lashing with a clove hitch on the opposing leg from where you started and below the lashing. (If you have excess rope after your lashing is complete, you may coil it and tie it off to one of the legs).
Note: You must make sure your lashing is tight. If not, it could cause failure of the tri pod system.
After completing the entire lashing we can then raise the tripod by raising the center timber and crossing the outer timbers forming an equilateral triangle. Once the tripod is in its upright positions you may begin to attach your web sling. To attach the web sling you start by placing the sling over the outside timbers at the top. Next you take a bight of the sling down through one side of the center timber above the lashing and pull a bight up through the other side of the center timber above the lashing. After this you need to attach your system of choice to both bights of the web sling.
After you have completed this step, something you need to consider is the legs of the tripod can and will kick out or lift up may causing it to tip over. You can choose to picket and lash in place or use a tieback system to make sure the legs are secure. If you chose to lash in place you can also use that leg as a snatch block sling for a COD in your haul/lower system. Keep in mind the setup is best done as close to the incident as possible, timbers can be quite heavy. Once the setup is complete a safety officer needs to monitor the Timber tri-pod in case of sudden failure.
DISCLAIMER: Fire and Rescue Concepts suggest extensive hands on training be completed on Timber rigging before performing these techniques out on the field. This four part series is for informational purposes only. If Departments wish more training on Timber Rigging please contact us at firstname.lastname@example.org