Tom Shelley reports on a mooring system for boats
whose philosophy offers benefits to most kinds of coupling and
mechanical connection
A mooring system for boats avoids damage to hulls from fenders by
adopting a unique philosophy. Restraint is still by mooring ropes
but the boat is pushed away from the pontoon at the same time by
a system using strong and weaker springs, universal joints and
break away couplings.
Invented by a retired petrochemical instrument engineer, it
manages to achieve its goal while avoiding the effects of any
kind of mishap, whether caused by man, tide or weather.
Despite its sophistication, it is not excessively expensive, and
its underlying ideas are applicable to any kind of mechanical
attachment, whether fixed, linear or rotating.
Richard Meredith, who lives in Crowborough, calls his inventions,
Epor, which is rope spelled backwards. He has named his company,
Silverpin. He came up with the idea as a means of holding a boat
away from the edge of a mooring pontoon without totally relying
on fenders. While fenders do a superb job in protecting a boat
hull from the worst effects of banging and grinding against the
side of a mooring pontoon, they do mark the gel coat on the hull.
This is unacceptable to somebody who has just spent a small
fortune on purchasing their shiny new toy for big boys.
His idea comes in two forms for boats. A "Low Power"
type for craft up to 30 feet in length, and a "High
Power" type for craft from 30 to 40 feet. For larger types,
he suggests two High Power types could be used.
The Low Power type has a heavily constructed spring housing
permanently attached to the pontoon. Into the shaft in the centre
of this slots a torque arm. This ends in a universal joint to
which is attached a male member, fitting into a female element on
a connecting arm, permanently attached to the boat by a second
universal joint. A foot pedal which clamps onto the torque arm
assists partial compression of the main spring during mooring.
Although not in the original design, the arrangement now includes
a weak spring element to keep the end of the connecting arm
pressed against the male member element under all circumstances.
These include situations, where, perhaps the boat is not tied up
tightly enough, and it is able to move beyond the point where the
torque arm reaches its extreme outward position. When the weak
spring decompresses, it exposes fluorescent bright red painted on
its normally covered shaft.
In the High Power version, there are also two spring elements but
in reversed positions. The pontoon spring is the weaker spring,
but the main spring force is exerted by a gas spring forming part
of the connecting arm. We were told that it requires 600kN to
even start compressing the gas spring. Mooring involves using a
screw or block and tackle gas spring compressor. The weak spring
enables the compressed gas spring to be connected to the torque
arm, freeing two hands to gradually disconnect the compressor. As
the gas spring expands, it gradually pushed the boat away until
its is constrained by its mooring lines. When this happens, the
compressor can be completely removed.
During surges in gale conditions, the maximum spring force is
designed to be momentarily overcome, allowing the craft to kiss
its conventional fenders. Meredith claims that, "For 99.99%
of the time, the craft's conventional fenders do not come into
play."
The sliding male-female connection, it is said, "Allows
easy, safe connection and disconnection even in gale
conditions." In the event that the craft loses all its
mooring lines, either because of extreme weather or incompetence
by the crew, the connection just pulls apart, without causing
anything to be pulled off the side of the hull.
The connecting arm then drops down, a rubber doughnut ensuring
that the falling end of the connecting arm does not mark the hull
when it hits it.
The incorporation of two universal joints in the system ensures
that the craft can range horizontally by about plus or minus one
foot (300mm) and rise and fall vertically by about the same
amount relative to the pontoon. The torque arm is adjustable in
length in order to cope with a range of gunwhale heights above
the pontoon, and incorporates an adjustable mechanical stop,
which allows it to overhang while in the 'parked' position,
before attaching to the connecting arm. This stop can be adjusted
to suit different craft and fender diameters. The length of the
connecting arm may be adjusted by means of an incorporated
screwed rod.
Custom clamps fit different pontoons and custom gunwhale and
toe-rail attachments fit different craft. Hooks on the connecting
arm allow fenders to be positioned amid-ships, away from the
hull. The prototype equipment was manufactured by ER Edwards and
Sons in Horsham, and looks solid and dependable. Meredith
describes it as being, "Fully marinised with sealed for life
lubricated springs, self lubricating bushes and a hard anodised
finish. Richard Paine, the managing director of agents
Inventorlink Products estimates production scale manufacturing
cost to be around £1,000, which he considers to be quite trivial
to the sorts of end customers he intends it to be sold to.
But more than a product, it represents a philosophy. It is often
desirable that mechanical couplings should at the same time
couple securely, yet be able to break away in a worst case
scenario. Using springs to absorb force and hold in place is
quite a common approach but usually, the spring force only takes
performance into account, and not possible problems that might be
encountered when coupling up or which might result from excessive
movement. Two springs is the solution in the design of the Epor,
but it is also possible to consider variable rate springs, which
exert a weak force when they start to compress, and a strong
force when further compressed, although it would be hard to
design one for the Epor application.
All aspects of the designs are covered by patents either granted
or applied for.
Inventorlink
Products
Richard
Meredith
Email
Inventorlink Products
Pointers
* Coupling is designed to work in conjunction with rope moorings,
but keep a boat hull at a sufficient distance from a mooring
pontoon to avoid the fenders marking the gel coat
* A weak spring keeps the system in engagement, and in the case
of the system with a gas spring, also assists in the engagement
process, while a strong spring absorbs the main forces.
* The system copes with vertical and horizontal movement and
breaks away without causing damage should the rope moorings fail
For more technical
developments see www.eurekamagazine.co.uk