Ronstan Series 55 Orbit Cheek Block

Features

• Ultra Lightweight
• Low friction 2-stage Orbital ball bearing system
• Highest working load in its class
• Easily fitted and securely retained Dyneema Link head
• Low profile and compact
• High performance cleating
• Recessed underside to suit cruved mounting surface

Specifications

• Sheave Diam: 55 mm
• Max. Rope Diam: 10mm
• Max. Wire Diam:
• Pin Diam:
• Max. Working Load: 500 kg
• Breaking Load: 1000 kg
• Weight: 70 g

Lightweight
Kilogram for kilogram of working load, BB and RT Orbit Blocks™ are the world’s lightest. To gain peak performance, we engineered out the heavy steel load straps, head post, shackle, full-length fasteners, and cleating accessories.
Through extensive research and development, we replaced virtually all metal components with high-tech polymers and fibre equivalents.

The unique orbital design allows the bearing to only be in the active areas of the floating sheave.
This minimises the mass of the inactive return race and hub.

Weight and bulk are further reduced in the different block configurations. The ball bearing single and becket block has a through-sheave becket arrangement. The result? The lowest weight possible.

Multi-sheave blocks have only single intermediate cheeks and an ultra-light and efficient head arrangement.
This gives a 30% weight saving advantage over the nearest competitor. Other brands just link together their single blocks.
This results in unnecessary double cheeks between each sheave, held together by a heavy steel channel across the top of the block.

Highest working load in its class
The orbital ball-bearing arrangement gives the largest possible bearing race diameter. This maximises load performance. The proven Ronstan 2-stage bearing system features high compression grade acetal ball bearings and a secondary full-contact bearing. This gives minimum friction across the full working load range.

The floating sheave and bearing system is supported by a fibre-reinforced load frame. The design was computer modelled to be stress optimised. The Dyneema® Link is produced from FSE Robline SK75 fibre, which is 10 times stronger and lighter than steel, and provides the final connection from the block to the load point.

Simple and secure attachment
The Dyneema® Link is easily fitted and is retained securely by a moulded retainer clip. The flexible link can be left with one end attached to the block when fitting - no more lost shackle pins.

The system is compatible with Dyneema®/Spectra® strops, webbing and carbon connection points - much more so than steel loop tops or shackles.

Low profile and compact
The flexible Dyneema® Link provides controlled rotation and 0° or 90° orientation. It connects directly to the head of the block rather than to an intermediate head post. This reduces weight and gives the lowest possible profile while allowing full articulation. Beckets have been carefully designed to minimise height.

Applications

• Mainsheet systems on dinghies, sportsboats and small keelboats to 9m (30ft)
• Spinnaker sheets on dinghies, sportsboats and small keel boats to 9m (30ft)
• Halyard, Vang and Backstay application on boast to 8m (26ft)
• Control line applications on larger yachts

Materials

• Ball bearings - High compression strength carbon black Acetal
• Stage 2 bearing - Carbon fibre reinforced, PTFE impregnated Nylon
• Frame/Cheeks - Toughened, glass fibre reinforced Nylon
• Rope Link: UV stabilised, multi-strand impregmented SK75 Dyneema®
• Sheave: Carbon fibre reinforced, PTFE impregnated Nylon