Ronstan RF74108 Series 75 Core Block – Halyard

Core Blocks are a true all round solution. A tuned 2-stage bearing
system provides excellent performance across the full working load
range with an integrated thrust bearing feature and the resilience
to handle high dynamic or static loads. Acetal sheave, alloy cheeks
and stainless fixings complete the durable package. For reliability
and a long service life, these blocks are the right choice for
sheets, halyards and control line applications for cruising and
racing. 

Universal Bearing –

Dynamic and high static load performance

The Ronstan Universal Bearing incorporates our proven
2-stage bearing system

Stage 1 – Under moderate loads, Acetal ball bearings
ensure minimum friction.

Stage 2 – Under heavy loads, where deformation of ball
bearings alone would result in increased friction, a sliding Acetal
bearing on a polished stainless steel race takes over, maintaining
low friction performance.

Additionally the ball bearings are configured to act as
a thrust bearing between the sheave and cheeks, preventing the
sheave from rubbing on the cheeks and causing friction when the
line lead in and out of the block isn’t perfect. Particularly
important for cheek blocks.

Alloy cheek plates

Block cheeks are manufactured from the highest quality
alloy for maximum strength. Material optimisation and the cut-away
design minimises weight and allows easy fresh water rinsing of salt
and debris from the bearings.  Cheek design has been further
styled with flaring at the block throat and reduced gap between the
cheek and sheave, minimising rope wear.

Applications

• Ideal for use on mainsheet, spinnaker sheet, vang, halyard and
  backstay applications on boats up to 14m (46ft).
• General applications on larger yachts.
• Alloy sheave models are available for use with wire.

Materials

• Sheave: U.V. stabilised acetal or anodised aluminium (AW
  models).
• Cheek plates: Aluminium alloy
• Ball Bearings: High compression strength carbon black
  acetal.
• Pin: 2205 stainless steel

Features:

• Class leading performance and sleek, contemporary styling
• Excellent dynamic and high static load performance
• Less than half the friction of the nearest competitor
• Suits direct attachment to mainsail headboard for 2:1
  halyard
• Removable 8mm (5/16) threaded pin at head
• Acetal roller on head pin to suit spliced line attachment
• Alloy Rope/Wire sheave version also available
• Central hub hole can be used as a becket take-off or tie-up
  point

Specifications:

Sheave diameter	75 mm
Max. Rope diameter	14 mm
Max. Cable diameter	– mm
Pin diameter	8 mm
M.W.L.	1500 kg
B. L.	3000 kg
Weight	234 g