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All About Pulley Systems - Part 3 - Connection Point
There are three main ways to anchor your pulley system to the tree (or master point of your highline): one involves using a separate anchor sling for your pulleys and your brake, another uses the becket of your main pulleys to attach the brake (inline brake method), and the last involves using a rigging plate. There are pros and cons to each, we will look into them below.
This method of connecting your pulley system to the anchor is unique because it uses separate slings for the main pulleys and the brake. Some of the benefits of this system is that you often have more room in your pulley system because the brake is typically behind the main pulleys with respect to the anchor. This gives more room for the multiplier rope-grab to travel before running into the brake.
Another benefit to this method is that you don't have the problem of having the handle of the brake hit the pulleys when trying to detension. This problem can be quite cumbersome and can lead to detensioning explosions (all the tension lets out at once, not fun). There are ways around this, but not nearly as clean and simple as separating your brake from your main pulleys.
Some of the faults of this method are that it requires a lot of extra gear and weight. You have to remember to bring an extra sling, an extra connection device, and another carabiner for detensioning when using the separate anchor method. Also, while rigging (lowlines, mainly), you have to go through the hassle of making sure both your pulley sling and brake sling are high enough on the tree before you tension the line. This can be a major pain when you are in a rush to get your line up.
Inline Brake Method
This method of connecting your pulley system to the anchor involves attaching your brake to your main pulleys becket allowing you to directly connect the pulleys to the anchor, bypassing any added components.
I really like this method simply because it's the lightest, most efficient, cheapest way to anchor your pulley system. You only have two anchors on your whole slackline using this method, and it's using the least gear possible. There are some big drawbacks to this method though, which give the other methods a slight advantage. The most notable downside to the inline brake method is the added friction, especially with smaller pulleys and larger brakes (i.e. Rock Exotica Machined Doubles and Petzl RIG). When the rope travels through the sheaves of the pulleys, the brake is typically too wide to avoid being rubbed when it's attached to the becket of the main pulley. This can seriously effect the amount of power you can get out of your pulleys when tensioning longer lines. This system is best for highlines where weight is absolutely critical.
Another big drawback to this method is that releasing tension is very difficult, especially with smaller pulleys. The handle of the brake gets lodged beneath the tensioned ropes and is nearly impossible to free when the tension is high. You can somewhat avoid this by using a twisty shackle, as shown in the picture above.
The last and least drawback is that having the brake attached to the becket reduces the amount of throw that can be pulled out of your pulley system. With the knot on one pulley and the brake on the other, you are forced to have at least 2 ft. of pulley system left when you pull all the rope through. This matters the most on highlines where it's a shear cliff right beyond the anchor and you are leaving the pulley system in the line.
Rigging Plate Method
This method involves separating the brake and main pulleys by using a rigging plate. This method is very effective and is my favorite method for anchoring my pulley system.
One of the main reasons I like using this method so much is that it organizes your rigging very nicely. Not only does it separate your brake from your pulleys, it also allows you to connect a second multiplier without adding yet another anchor sling. You can also tie your backup knot for your brake and connect it directly to the rigging plate. You can also use your rigging plate to organize all your gear after you are done derigging.
The only disadvantage that I can see with this system is that it requires another piece of gear (a Rigging Plate).
With the rigging plate method, there are different plates to choose from and certain qualities to look out for. Here is a list of the main characteristics to keep an eye out for:
- Breaking Strength
- Anchor Hole Size
- Rigging Hole Size
- Hole Spacing
As with all of the other components in our pulley system, if you choose to use a rigging plate, it should be strong. Keep an eye out for the minimum breaking strength (MBS), and try and keep that number higher than the MBS of the webbing you are going to be using. For instance, if you are using Type-18, which has an MBS of 27 kN, you should choose a rigging plate with an MBS higher than 27 kN.
Since we are adding a component to the pulley system that doesn't necessarily have to be there, it's important to be aware of the weight that this component is adding to your overall system. Most good rigging plate are made from aluminum, so the weight isn't substantial, but it's still an important quality to keep an eye out for.
Anchor Hole Size
This quality is very important for a rigging plate because you need to have options for being able to anchor your pulley system. You don't want a rigging plate that can only accept small carabiners because this will limit the types of anchors that you can setup. The bigger the anchor hole, the better. This will give you many many options for anchoring the plate to a variety of connectors (i.e. Shackles, Carabiners, Quicklinks, etc...).
Rigging Hole Size
Most rigging plates will have a number of rigging holes, which are typically all the the same. The size of these holes is very important because this is where you will be connecting your pulleys and brake (and other items in your pulley system). You don't want to be too limited on what type of connectors you can use to anchor your pulley system components with, so the larger the holes, the better.
Not only does the size of the rigging holes matter, but their spacing as well. Some rigging plates have sort of a paw shape, where the rigging holes fan outwards, and some rigging plates are long and have many many holes. The fan shaped plates typically have a nice spacing between the holes that allows you to have a nice gap between your main pulleys and your brake, which is the main reason why we would use a rigging plate for our pulley system.
The last characteristic to be aware of when purchasing a rigging plate is, of course, the price. Once again, you get what you pay for. Higher priced rigging plates tend to have the above characteristics optimized and will typically work a lot better than the lower priced rigging plates. Be sure to evaluate each of these characteristics when choosing your plate though, do not be fooled by a high price alone.
- Breaking Strength: 33 kN (7,418 lbf)
- Weight: 1.79 oz. (51 grams)
- Anchor Hole Size: 1-1/8" x 1-7/16"
- Rigging Hole Size: 0.75" Diameter Circles
- Rigging Hole Spacing: 2-5/8" from top of top hole to bottom of bottom hole
- Dimensions:Length: 2.83"
- Price: $25.00
A really nice rigging plate machined out of high quality Alloy 7075 Aluminum. The anchor hole is very nicely size and will fit on any size shackle that us slackliners would consider using (anything below 7/8"). The rigging holes are a little on the small side, but they are big enough to accomodate any standard carabiner or quicklink.
I really like this plate because it's SUPER lightweight. I use two of them for my lightweight pulley system and they are perfect (I use two so they fit on the bolt side of a 1/2" Anchor Shackle).
- Breaking Strength: 36 kN (8,093 lbf)
- Weight: 3.84 oz. (108 grams)
- Anchor Hole Size: 2" x 2-1/4"
- Rigging Hole Size: 0.75" Diameter Circles
- Rigging Hole Spacing: 4-1/16" from top of top hole to bottom of bottom hole
- Dimensions:Length: 3.98"
- Price: $43.00
A great mid-sized rigging plate that's wonderful for lines in the park. I like this plate because of it's MASSIVE anchor hole, which can accept up to 1" shackles (HUGE ones). This makes anchoring it quite easy compared to other rigging plates (none of which we are displaying here though).
There are few downsides to this plate though. The first is the size of the rigging holes. They are very small and can only accept a carabiner or quicklink. No shackles will fit through them. Also, the thickness of the plate is odd. If doubled, it doesn't fit on the pin of a 1/2" Anchor Shackle, and when doubled, they are still too thin for a 5/8" Anchor Shackle. The best way to anchor them is to use the spanset through anchor-hole technique, which is shown in the picture to the left.
This system works very well for anchoring any single rigging plate. If you try and attach your rigging plate directly to the bolt of a shackle, it will often sit offset, which can place strange loads on the area in contact with the shackle. By passing the spanset through the rigging plate anchor hole, you avoid any tri-loading situation as well as the offset issue. If you want to connect your rigging plate directly to a shackle, it's best to use double plates.
- Breaking Strength: 52 kN (11,690 lbf)
- Weight: 11.4 oz. (323.2 grams)
- Anchor Hole Size: 2-1/4" Diameter Circle
- Rigging Hole Size: 1-1/2" x 1"
- Rigging Hole Spacing: 6" from top of top hole to bottom of bottom hole
- Dimensions:Length: 7.00"
- Price: $51.85
The best of the best rigging plates. The large size gives more than adequate room for spacing your main pulleys and your brake. The large anchor hole is optimized for all shackle sizes. The rigging holes are nice and big and will accept many sizes of carabiners, quicklinks, and shackles. When doubled, these plates sit perfectly on a 5/8" anchor shackle. The high strength is stronger than most slackline webbings. There is simply nothing wrong with this rigging plate. I use it for nearly every slackline that I setup (excluding the times when I use the inline brake method).
Here's a nice table showing the differences between the five brakes above:
|Attribute||Rock Exotica TriRig||Rock Exotica PentaPlate||SMC Large|
|Breaking Strength||33 kN (7,418 lbf)||36 kN (8,093 lbf)||52 kN (11,690 lbf)|
|Weight:||1.79 oz. (51 grams)||3.84 oz. (108 grams)||11.4 oz. (323.2 grams)|
|Anchor Hole Size||1-1/8" x 1-7/16"||2" x 2-1/4"||2-1/4" Diameter Circle|
|Rigging Hole Size||0.75" Diameter Circles||0.75" Diameter Circles||1-1/2" x 1"|
|Rigging Hole Spacing||2-5/8"||4-1/16"||6"|
Here's a nice picture showing the above Rigging Plates side-by-side:
- All About Pulley Systems - Part 1 - Main Pulley Characteristics - Shopping Guides Sep 29
- All About Pulley Systems - Part 2 - Brake Characteristics - Shopping Guides Sep 29
- All About Pulley Systems - Part 5 - Multiplier Characteristics - Shopping Guides Oct 03
- All About Pulley Systems - Part 4 - Rope Characteristics - Shopping Guides Oct 01
- All About Pulley Systems - The Complete Guide - Shopping Guides Oct 12
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