How to choose the correct Spinlock product?

The advances in rope technology, particularly with the advent of materials such as Vectran and PBO and the resulting increases in shock loads, demand better and better holding solutions for higher loads at smaller diameters. Latest developments include holding solutions for coverless Vectran line.

The undisputed principles

1. The larger the diameter, and hence surface area of contact, the larger the load that can be held on the same type of rope. This is the golden rule of rope holding and applies to all types and makes of holding device.

2. There are two distinct types of solution: a clutch, and a jammer. A rope clutch is a device which automatically engages on the line, yet allows the line to be pulled through and up to certain (relatively low compared with rope strengths) limits can be released under load. There is no make of clutch that can get within even 20% of the break load of the latest hi-tech ropes. A jammer is non-releasable under load, but because the holding system does not need to be compromised to provide release, is optimized to safely hold very high loads indeed, in some cases beyond the working load of the rope itself.

Definition

Rope Clutch - AUTO lock and release
Jammer - MANUAL Lock and release but higher holding loads

3. The limit of a conventional core/cover rope is usually the polyester cover, as when pressure is applied at a position on the line, the cover becomes loaded and is then in many cases the first part to fail. This applies at a clutch, but equally at sheaves, on winches and other turning points.

An important part of the Spinlock Powerclutch design (but not for the ZS jammer) has always been to try and ease the load at this limit, rather than break the cover but this becomes increasingly difficult to achieve with smaller diameters due to the high point loading.

4. Loose covers are one of the biggest problems. If the cover is loose, then the likelihood of the cover failing greatly increases. When outside sleeving is used (a very effective method of increasing the load holding on all systems more diameter / surface area always wins), it is vital that a cover from the same diameter rope is used to ensure this.

5. Vectran and PBO transmits much higher shock loads than previous cordage types. These shock loadings are transmitted back to the jammer. Clutch mechanisms are not as effective as the ZS jammer and XX system at dealing with these peak loads. With the ZS and XX, two parallel and symmetrical jaws always move in unison, in the direction of load, and in shock create no shearing loads on the rope cover.

Summary of key facts

a. Diameter is the most critical factor.

b. Any claim that a device can hold the same load on several different diameters is untrue.

c. Vectran significantly increases gear shock loadings.

d. "We only want to hold the load for a few seconds...” is the most dangerous comment we know. It only takes a few microseconds to break a rope.

e. Loads of up to 12,000kg REALLY CAN be held - but not on conventional rope clutches.

f. There are very few differences in rope holding maximum between brands of normal rope clutches.

g. A balanced clutch / jammer mix is usually correct

Read about: Spinlock Products