ropewalk.pdf

Building a Ropewalk

by Phil Krol

Many model builders who have reached the rigging stage on their models wish

they had better cordage. Most have heard that a contraption called a ropewalk

makes model rope, but have no idea where to begin. Let me assure you from my

own experience that if you can build a ship model to the rigging stage, you can

build a ropewalk. The obvious advantage of using one is that you can lay up (twist)

high quality rope in all the necessary diameters to fully rig the model. W hile some

ropewalks are very complex and require advanced machining skills, my approach

keeps it as simple as possible without sacrificing functionality. A ropewalk

consists of three components:

1) The whorls (gears) that twist the individual strands.

2) The topper, a cone-shaped bobbin with three grooves, that holds the strands.

3) A spinning looper that keeps up with the twist as the rope is formed.

As the strands twist, torsion builds up until they want to knot or break. The three

strands come together at the narrow end of the topper and with the aid of the

looper begin to spin in the opposite direction to relieve this stress and form the

rope. During the rope making process, the topper moves toward the whorls as if it

were motorized.

Traditional rope is made in three different styles.

1) Hawser laid has three strands with a right-hand twist.

2) Cable laid has three lengths of hawser laid (nine strands) with a left-hand

twist. This is sometimes referred to as two stage rope as you first make hawser laid

and use that as feed stock for cable laid. These large ropes are used for anchor

cable, lower stays, and sometimes the shrouds.

3) Shroud laid has four strands with a right-hand twist around a center core

called a goke. Laying up this type requires a fourth whorl. In my opinion, itÔs

difficult to see the difference between shroud and hawser laid rope, and the fourth

strand with a goke adds complexity making the rope making process more

difficult. It simply isnÔt worth the effort.

THE COM PONENTS

The whorls are nothing more than a set of four gears that simultaneously twist

the strands. The center or drive gear turns three gears spaced equidistantly

around it. Their size and pitch arenÔt important, since the gear train is built around

the gears you find. I found 1-5/8" diameter nylon gears with a bronze bushing in a

surplus store for 50 cents each.

I laid out the gears on a rectangle of 3/8" tempered Masonite§ 5" x 6-1/2"

drilled four holes to press fit bronze bushings with 1/4" inside diameter. The gears

were pinned to 1/4" brass shafts that slid into the bushings and were held in place

by collars locked with setscrews. These are available in the parts bins of most

hardware stores. The center drive gear shaft extends 2" beyond the collar so it can

be connected to a motor (see Fig 7).

Fig 1

To attach and hold the strands to the whorls, I first counter bored the shafts on the

three twist gears to take a 1/16" copper tube č" in length. Next, I drilled and

tapped 3 holes for a 2-56 thumbscrew to hold the tubes in the shaft holes.

Fig 2

The topper is a cone shaped piece of wood 1 ċ" long by 1 Č" in diameter with

three grooves to hold the strands spaced equidistance. The point is hollowed out a

little to allow space for the rope to form. These dimensions are not critical and

variants of this shape will perform as well. The topper is mounted on a rod which is

inserted into a č" x č" piece of brass rod to give the assembly some heft. This was

mounted on a 7/8" x 2 č" x 1/8" wood platform which was mounted on a pair of O

gauge railroad trucks to make a facsimile of a flatcar with a topper on it. The

sprung trucks were purchased as a pair for $3.50.

Fig 3

The flatcar topper assembly travels on O gauge track which is mounted on a 2" x

4". Mine is 10' long and half lapped at a track joint so it can be taken apart to

facilitate storage. The 10' length produces finished rope about 7' long. I have yet to

encounter a rigging situation where the 7' length was inadequate. However, you

can make the bed longer or shorter, as you wish.

Fig 4

The looper is the spinning device the three strands are attached following the

narrow end of the topper. Some advocate the use of a reversible motor to assist this

process. However, I prefer using a quality ball bearing fishing swivel for the

looper. This is a simple yet effective approach. As rope begins to form at the tip of

the topper, the looper starts spinning and the topper starts moving on the track

towards the whorls. You just stand there and watch with little to no help from you.

Fig 5

A variable counter weight should be used to tension the strands and the forming

rope. The weight is attached to a cord on the end of the swivel and extends over

the end of the bed to the floor. A pulley or sheave on the end for the cord is helpful

or even a smooth groove for the cord to ride in. The amount of weight varies from

Č oz. for small rope to 1 ċ oz. for heavier rope. As the rope forms, the strands get

shorter pulling the weight off the floor to about one third the length of the bed. A

counter weight attached to the flatcar to create some resistance to its travel is also

needed. This varies from nothing for very small rope to about ċ oz. for heavier

rope. Since this weight travels the entire length of the bed, a gaff was installed to

compensate for the shorter distance to the floor. This works by placing the cord in

a sheave at the base of the gaff, running it over a sheave at the extended end of the

gaff and down to the floor. The flatcar travels along the bed pulling the weight and

when it reaches the top of the gaff, you stop the motor and transfer the weight cord

from the tip to the base of the gaff and restart the motor.

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