Tipps und Tricks

Tensioning of the longline – pulleys for long slacklines

Table of contents

Pulley block

If slacklines get longer, they not only become more difficult to walk on, but the construction of a longer line – from approx. 25 – 30 m – becomes more and more of a challenge. Longlines in the range of 30 – 40 m can be tensioned with a low-stretch strap just with two large ratchets (one at each fixed point). With the Ellington pulley block and motivated personnel, you can go that little bit further and put the strap material and hands under a lot of strain. You need a different tensioning system.

You have the choice: either you use easy-to-operate but very heavy lever chain hoists for tensioning, or you opt for a pulley block suitable for longlines. I recommend the latter variant to all those who like to work with rope, pulleys and backstops and want to travel as light as possible. In recent years I have tested various pulley systems and material combinations and will present a few proven variants here.

Material and technology for a basic pulley system

5 to 1 basic pulley

The standard is a basic pulley with a ratio of 5:1, which only requires two double rollers and a rope. A static rope with a diameter of 11 mm is ideal. The required length depends on the tension range. For lines up to approx. 70 m, 30 m rope is sufficient, for lines up to approx. 100 m, a 50 m rope is safe. A discarded climbing rope (min. 10 mm diameter) will also do for shorter longlines.

There are several points to consider when selecting double rollers:

  • The roller sheaves must be positioned next to each other, not behind each other (such rollers are also available for use on cableways).
  • The breaking load must be at least 30 kN. For lines in the range 100 m and more, breaking loads in the range 50 kN are recommended. This oversizing is for safety reasons and to ensure that the recommended maximum working load limit is observed. This is significantly below the breaking load.
  • There must be a second suspension point on the rollers opposite the main suspension point.
  • Rollers with ball bearings work much better than those with plain bearings. The difference is unfortunately also reflected in the price.

The basic pulley block is quick to assemble: I tie the rope directly to the pulley with a figure eight knot as “tight” as possible (see picture!), to avoid wasting any lift. You don’t have to worry about the metal edges at the eye of the pulley. The rope will not be damaged here. Only 1/5 of the total force acts on the single rope. Now the rope is inserted into the sheaves as shown in the picture.

Variants for more power

6to1 basic pulley system

The basic pulley block can be upgraded with an additional simple rope pulley. This results in a ratio of 6:1. With high-quality components and this transmission ratio, even lines of over 100 m in length can be tensioned. In addition, the backstop (more on this later) is less stressed. For this extension I deliberately use a small roller (breaking load 30 kN) so that it does not “overload” the basic block too much. A twisted screw gate (Maillon Rapid Twist, 8 mm) is used to connect to the double roller to which the line is later fixed. You can see how the parts fit together on the photo.

The connection to the fixed point

Longlines are almost always stretched between solid trees. The basic pulley block is attached to the trunk of such a tree with a tree sling. Industrial slings (WLL 500 kg or better 1000 kg) are suitable as tree slings. Personally, I prefer the adjustable tree slings from Slackline Tools. The connection to the pulley is made with a delta screw gate (min. 10 mm material thickness). A sufficiently dimensioned shackle works the same way.

Connection to the rope pulley with bolt linelocker

Seilrolle mit Bolzen-Linelocker
Rope pulley with bolt linelocker

First of all, the span distance must be estimated, which requires a lot of experience. Then pull the pulley block to the required length and connect it to the band. For longlines up to approx. 70 m or tensioning up to 10 kN you can lay a classic chain link linelocker with a clear conscience. Bolt linelockers are safer and can also be used for longer lines.

You need a backstop

A backstop must now be fitted to the rope of the basic pulley block. Eddy (Edelrid) and Grigri (Petzl) are proven in this area. The Eddy is more solid, which is why I prefer it. Both devices not only hold the pulled in rope, but also serve to (later) relax the line.

Eddy als Rücklaufsperre
Eddy as a backstop

If you install a separate relief device in your system, you can also use Minitraxion or, even better, Protraxion (both Petzl) as a backstop. The advantage of this combination of clamp and roller is that there is less friction lost than with Eddy or Grigri.

But careful: used this way, no more than 2.5 kN wire rope pull should be expected per/Minitraxion. With a 5:1 basic block and a heel tension of approx. 12.5 kN, the limit of what is reasonable would be reached.

Minitraxion im Longline-Flaschenzug
Minitraxion in a longline pulley block

The backstop is attached to the tree trunk with a second tree sling and a suitable fastener (made of steel) slightly below the base block.

5:1 + 3:1 = 15:1

However, it is not possible to achieve sufficient heel tension for longlines with the basic pulley block alone. This is why a 3:1 block and a total gear ratio of 15:1 (or 18:1 with a 6:1 basic block) is added. The cost of materials for this is reasonable: an ascender (or a short Prusik), a carabiner and another roller. In contrast to the rest, these parts are also not safety relevant.

Kompletter Flaschenzug
Complete pulley block

I usually use the minimalistic Tibloc (Petzl), a large ball bearing single roller and an oval steel carabiner. Steel because the material is not dented by the edges of the Tibloc. You can see how the parts fit together on the photo. In reality the pulley block is of course not pulled that far together!

If a few people help, it’s easy to tension a longline with this technique. The way to do this is pretty self-explanatory. Tip: using hand grips on the pull rope makes this more comfortable.

Securing the rear of the pulley

Hintersicherter Flaschenzug
Rear-secured pulley block

Back-up measures are generally a good idea for longlining. The length/heel tension at which the pulley block is backed up depends on its components and personal safety requirements. A piece of rope (single rope or static rope, min. 10 mm diameter) is all you need to back up the hoist (see picture). I usually attach the back-up rope during tensioning and shorten it again at the end.

Loosening the longline

Once again, caution is advised when loosening! At first it is often very difficult to release the clamp of Eddy or Grigri. The rope can be pulled into the device so quickly that it can cause burns to the skin. Teamwork is required: one person holds the brake rope in braking position with both hands (do not wrap the rope around the hands!) and slowly lets go. Meanwhile, the other operates the release lever.

Longlining is not without risk

Important: the information in this article is not complete and can in no way replace basic knowledge of longlining. Everyone is responsible for their own actions!

Share this article with friends

Discover the suitable products in the alpinetrek shop

Alpinetrek-Expert Fritz

Alpinetrek-Expert Fritz

Climbing and mountaineering became my passions thanks to my fascination of the mountain world (and thanks to a few coincidences). And now, looking back on my now 25 or so years of climbing experience, I believe I owe a lot to mountains and climbing walls.

No comments yet

Leave a Reply

Your email address will not be published. Required fields are marked *.
The comment will be unlocked after moderation.

You might also like

by Alpinetrek-Expert



Discover the suitable products in the alpinetrek shop

You might also like


Frag die Bergfreunde

Wir sind Mo. – Fr. 10:00 – 17:00 Uhr für Dich da!