Shock Cord (Bungee Cord) Manufacturing and Specifications

 All about Bungees!

A length of bungee cord acts like a cross between a spring and a rope. It is mainly used for it's shock absorbing properties hence why at PTW we mostly refer to it as Shock Cord.

There are various other terms and they tend to be used interchangeably including Braided Rubber Cord (as per B.S.I.), Stretch Cord, Occy cord (in Australia) and simply Elasticated rope.

Note that some people may distinguish between the different terms according to either the construction of the cord, it's end purpose use, or whether the ends have been finished off with a hook/fitting. For example, internally at PTW, we generally refer to the cord itself as "Shock Cord", but a finished article with a hook, clip or eyelet loop at each end as a "Bungee".

Bungee/Shock Cord Construction

Braided Rubber Cord is the best descriptive term. The cord consists of a rubber core (which can be a solid rubber core or multi-strands of thin latex) which is then encased in braided sheath such as braided from polypropylene, or another type of, thread. Many different thread types can be used according to the end use requirement with thread colours to suit preference. It is the combination of the materials and construction used for both the inner core, and that of the braided cover, that determine the performance characteristics of the final product so must be matched to the end use specification.

  • Core: Solid or Multi-stranded in natural rubber (latex) or synthetic rubber.
  • Sheath: Braided nylon, polyester, polypropylene, or cotton for abrasion resistance and protection of the core.
  • Fittings: Metal or plastic hooks, loops, or crimps for securing the cord in various applications.

For quality and performance consistency reasons, PTW stock and offer solid natural rubber solid cored product where possible (usually diameters above 5mm) with either a high quality Polypropylene braiding, or our new premium Monoflex® Polyester braided shock cord stock range for it's improved strength, UV and abrasion resistance characteristics making it ideally suited to harsh environments including marine.

What have Bungee Cords been used for?

  • Aircraft Landing Gear (since World War I) acting as a shock absorber
  • Launching Gliders (from early days of flight & since 1934 at: Midlands Gliding Club & YouTube Launch Video )
  • People leaping from high bridges (since 1979) : First Bungee Jump Video (Bristol,UK)
  • & much more besides! It is an incredibly useful product that can be specified precisely for use in heavy duty and technical applications!

However, the vast majority of Bungee Shock Cords are typically used for:

  • Transport Load Restraint
  • Fixing of covers and tarpaulins
  • Flexible fixing of display banners, textile partitions, marquees, tents etc.
  • Leisure equipment including trampolines and soft play 
  • Seating
  • Accessory and tool fixing straps on bags, clothing, vehicles and other items.

Shock Cords from PTW stock can be specified to suit any of these typical applications.

What specification do I need?

Unlike most ropes, Shock Cord is intended to act as a spring and so the primary performance is about how strongly (or softly) you need it to resist being extended and how far it needs to be able to extend without it losing it's ability to spring back to it's original length. Note that it will already have failed as a Shock Cord long before the cord itself snaps, having lost it's ability to spring back to it's original length well before the cord breaks apart completely.

So the main specification considerations are: 

  • How strongly do you want the cord to resist being stretched?
  • What is the maximum force that might be applied to the cord whilst it still being able to return to it's natural length?
  • Durability factors such as abrasion or UV resistance for length of life
  • What diameter of cord is preferably (to be comfortable in the hand, or easy to tie or to fit onto or around other components?
  • Colour preferences for the outer braiding

An important criteria should also be consistency. Settling upon the best specification is commonly one of trial and testing to determine the best resistance for the application so it is important that those characteristics are then maintained across the entire length of the cord, all the reel of cord purchased and subsequent batches of cord for the same application going forward. This is a principal reason why PTW recommends single core Monoflex® product were possible, being a distributor direct from the manufacturer who controls the entire production process from the forming of the rubber core through to braiding so it not susceptible to differing rubber quality standards and latex grade variations more likely with generically sourced rubber and differing braiding materials and techniques.

Extensive inspection and strength testing at all stages of production and on through the whole supply chain into our despatch warehouse reinforces PTW's commitment to supplying shock cord to the consistently precise, high quality performance specification which is important to our customers.

All this means you are assured that the shock cord specification which PTW sample and supply will have a consistent performance that many low cost bungee cord suppliers are unable to match.

Why buy from P.T. Winchester?

  • Extensive range available from stock for next day delivery.
  • Competitive pricing for high quality assured cord specifications.
  • Discounted price list for approved business trade customers.
  • Knowledgeable staff ready to assist with specifications with sample matching service also available.
  • Additional large volume price discounts available.
  • Manufacturing specification consistency (we can't stress enough how important this can be for businesses with repeating bungee requirements).
  • Bespoke assembled Bungees made in-house to order with wide range of options for end fittings.