Cowans Sheldon 50 ton Electric Dockyard Crane

ModelPlan with complete model building instructions

Designed, described and Illustrated by Michael Adler - July 2001

If you would like to receive a complete zipped file of the text and all the illustrations, please send a request to <anthias@actcom.co.il>

This ModelPlan may not be used in any way except for private and personal use.  It will be published in the International Meccanoman magazine of the ISM.

capetowncrane A number of cranes were built for the admiralty during the Second World War.  Order No. 8118 was placed with Cowans Sheldon & Co Ltd of Carlisle and the crane was erected and commissioned at the new Sturrock Graving Dock in Cape Town during 1943.  The crane had a maximum lift of 60 tons with yoke and minimum radius of 19.6 metres.  The crane is well maintained and still operating today and can be seen in the photo against the dramatic backdrop of Table Mountain.   Two further examples of this crane can be found at the north dockyard, Devonport.

The Meccano model reproduces all the features of the original.  It was designed with simplicity in mind, and uses silent running Faulhaber 6 volt DC motors with built in reduction gearbox.  Their ease of mounting is facilitated by built-in 1 1/2" square flanged plates.  There are four movements - traveling, slewing, luffing and double winching.  The luffing mechanism is particularly interesting and faithfully reproduces that of the original.


capetownmeccano Construction of the Carriage (Fig. 1)
The top of the carriage is formed from pairs of 5 1/2" girders on each side arranged in channels in front of flat girders, and enclosing a 5 1/2" flanged plate.  4 1/2" angle girders and flat girders are arranged vertically at each corner.  A 5 1/2" girder joins the verticals at the lower ends on each side, and 1 1/2" triangular plates are fixed also at each corner which provide bearings for the bogies.   Aligned with the lower girders are horizontal 5 1/2" strips, fixed to the flat girders by angle brackets and additional triangular plates are fixed here.  A framework to support the drive to the traveling gear is fixed under lower girders and strips and this consists of overlapped 1 1/2" flat plates on the outside, and a single flat plate on the inside to which a horizontal 1 1/2" angle girder is fixed.  A 1 1/2" strip is bolted below the oval flanges of this girder to provide a lower bearing for the vertical travel drive rod.   The two sides of this framework are joined by a lock-nutted transverse 2" screwed rod, which greatly strengthens this structure.

Roller bearing
The lower part of the roller bearing is a 3 1/2" gear wheel (part 27b) fixed to the upper surface of the flat plate by four 1 1/8" screws.  It is separated from the plate by two collars on each screw.  A 5 1/2" circular girder (part 143) is also fixed to the top of the flanged plate and is ornamental.  When completed, ball thrust race will be bolted to the underside of the machine house with a ball cage between the two.  A screwed rod is lock-nutted in the centre hole under compression to hold the components tightly applied to each other.

chassis

 

Traveling gear (Fig. 2)
The sides of each bogie is a vertical 2 1/2" flat girder with its round holes below, which provide bearings for the wheel shafts.  The flat girders are fixed to 2 1/2" angle girders which are then attached to a horizontal flat girder.  The oval holes of the girders are horizontal.  A handrail support (part 136) is fixed under what will be the inner angle girder, but separated from it by a standard washer.  This forms one of the bearings of a drive rod, and should be carefully aligned and securely attached.  A 1/2" transfer pinion runs on a 3/4" bolt in the middle lower hole of the inner flat plate.  Fix 3/4" flanged wheels and 1/2" pinions to 1 1/2" rods on each side.  Two of the bogies are driven, one on each side, and the other two have no gearing. 

Drive to traveling gear
The most important shaft is the 1 1/2" shaft which has already been encountered in the bogie.  Its other bearing is the end longitudinal bore of a coupling, and a worm gear and 7/8" bevel are fixed to it.  Make sure the worm is free to rotate by placing sufficient washers under nearby bolt heads.  Ensure that the handrail support is aligned in two plains.

bogiedrive
A vertical 6 1/2" rod finds a bearing in the base plate above and the 1 1/2" angle girder and strip below. A 7/8" bevel is placed on lower end of the rod, which then passes through a collar and then the middle transverse bore of the coupling previously mentioned.  Two further collars are attached before passing the rod through the lower bearing.   Ensure free running of the rods and gearing with proper rod alignment and gear positioning.

Two trunnions 2 1/2" apart fixed under the 5 1/2" flanged plate are used as bearings for a transverse 3 1/2" rod.  A 50 tooth gear is fixed on the rod, and a 7/8" bevel at each end, outside the trunnions.  These gears mesh with 7/8" bevels on the vertical rods, but one is below and one above the transverse rod bevels, to obtain correct rotation direction of the traveling wheels.  A Faulhaber motor with a 3/4" pinion is fixed under the flanged plate to drive the gearwheel.

 



underbogie
Underneath view of bogie drive

Superstructure Chassis (Fig. 3)

chassis
Four longitudinal 9 1/2" girders are fixed at each end by transverse 5 1/2" girders.  Two 3 1/2  x 5 1/2" flat plates, one on top of the other for strength, are attached to the upper front of the inner two, and a 3 1/2" strip to the rear.  Three further 3 1/2" strips are fixed between the inner girders.  These provide support for a central channel bracket (part 160) and two girder brackets (part 161) one on each side.  Fix four trunnions to the long girders alongside the brackets, and also four angle brackets to the outer girders.  Ensure that the angle brackets are offset as much as possible inwards using the their oval holes and the oval holes of the long girders to which they are attached. 

winding
Fix main bearings for the winch drums in position.  Each consists of a 1 1/2" angle girder, a 1 1/2" flat girder and a flat trunnion.  Fix a central 1" x 2 1/2" double angle bracket in place just in front of the winch bearings.  Its central hole is the upper central screw of the roller bearing.   Fix a ball thrust race (part 168a) below the flat plates, with its central hole under centre of the double angle strip, but separated from the flat plates by three washers on each bolt.

Superstructure framework

derricking This consists of four 5 1/2" angle girders, joined at the front and sides by three further 5 1./2" girders.  Use narrow strips for the cross bracing attached to 1" triangular plates above and 1 1/2" flat plates below. Each jib bearing is formed from two 1" corner brackets attached to two double angle brackets.  These assemblies are bolted in position at the front end of the upper girders.  Fix a pair 4 1/2" angle girders to the upper horizontal girders by 1" corner brackets plates. 

The derricking rails
These consist of four vertical 9 1/2" girders bolted by their round holes at their lower ends to the previously attached angle brackets.  The round holed flanges of these girders must be fixed half way between the nearby trunnions as they form the running rails.  The tops of the rails are joined on each side by 2 1/2" girders, and as allowance must be made for the alignment of the long screwed rods with the rails which pass through their middle holes, washers are placed between the them and the rails.  Fix a 5 1/2" strip across the back rails at the upper end and use narrow girders here for bracing.

Derricking crosshead (Fig. 4)

crosshead Each side consists of two pairs of 1 1/2" flat girders, bolted to each other by their oval holes and overlaid by 1 1/2" strips.  1/2" pulleys and with bosses and collars run on 3/4" bolts which fix the two sides together.   A central transverse coupling is held in place by two 1 1/2" rods. .  Make a mirror image copy for the second side.   Two threaded couplings are screwed firmly onto the two lower bolts on the inner side  of each , and then the two sides are joined together with two 2 1/2" rods.  The derricking screw are 8" screwed rods.  Lock nut a threaded coupling to the bottom of each, to which a 2" rod is fixed and this carries the bevels which mesh with the motor drive.     





Attachment of derricking screws (Fig. 5)



 

The rods at the lower end of the derricking screws rotate in bearings which are collars.  These are fixed to the trunnions by screws on each side with suitable washer [packing so that the screws can be tightened without obstructing the central bore of the collar.  The lower ends of the derricking screws are then prevented from pulling upwards by washers and collars.  Set the bevels so that they mesh properly.

Derrick drive gear
In the prototype, the luffing screws are left and right hand rotation.  This is not possible in the Meccano model, and a 1:1 reverse gear is incorporated so that both screw rods turn in the same direction.  7/8" bevels on 1 1/2" rods  mesh with similar bevels at the base of the screwed rods.  On one side, fix  a 1/2" pinion to this rod, and on the other, a 1" gear.  An intermediate pinion meshes with the 1/2" pinion.  The final drive carries a 1/2" pinion, a 1" gear, and a 50 tooth gear.  The latter meshes with a 3/4" pinion on the motor output shaft. 

Slewing motion

A 1/2" pinion is fixed on 1 1/2" rod above the base plate, and another below to mesh with the 3 1/2" gear of the roller bearing. Build a top bearing for the vertical drive rod which consists of e 1 1/2" strip lock nutted to a screwed rod on one side and the motor support plate on the other.  Fix a worm  gear to the motor output shaft to mesh with the upper pinion. 

The Winding Drums

These are each built from a 2 1/2" gear, a wheel flange (part 137), a boiler end (part 163a) and a second wheel flange.    Carefully align all four components using rods through all the holes before fixing with four 1 1/2" bolts, and check for concentricity.  The second winding rum is a mirror image of the first.
The drive to the winding drums is taken from the motor to a 50 tooth gear.  This is fixed on a rod with keyway, the bearings for which is the 1" x 2 1/2" double angle strip fixed to the base plate.  One pinion is fixed to this rod, but the second has a keyway bolt so that it is free to slide.  A selector mechanism can be built if required to slide this gear into engagement with the 2 1/2" drum gear, otherwise it can also be fixed in place on the rod.   The sides of the drums can be deepened by slipping driving bands onto the wheel flanges.  Wind about 3 metres of cord onto each drum.

Drive motors

These are all fixed in line with each other on the left side of the base and the position of each is shown on the drawing.

Wiring

Attach wires to each motor, and bring all the wires, including those for the travel motor to a common point.  Use plastic cable ties for neatness.  Arrange for four centre off double pole switches to control the direction of motion, and fed from a potentiometer for speed control potentiometer via a transformer.

The machine house (Photo)
housing
This is built according to the photograph.  The ventilators are each made from four 3 1/2" strips and a 3 1/2" girder.  Washers are placed between each on a 2" screwed rod, and the structure is fixed to the cab side above using two angle brackets.  The cab sides are mirror images of each other, and are joined to the front.  The whole unit can be fixed
to the supporting framework of the jib using two 1 1/8" bolts on each side.   Built a counterweight from 5 1/2" strips at the back and flat girders at the sides.  If desired a roof can be added to the machine house. 


counterweight
The Counterweight

The jib

jib
This is built entirely from strips and narrow strips.  The lower compression longitudinals are each two 12 1/2" strips overlapped two holes.  The upper tension  strips are two 12 1/2" narrow strips overlapped four holes.  The base formed from a 7 1/2" strip on each side, and they are connected near the top with a transverse 5 1/2" double angle strip.  The hinge hole must be left free for the 1 1/2" locking rods, and two fish plates connect the angle and receive the narrow braced strip.  Fix a 1 1/2" double angle strip inside the compression strips four holes from the upper end.  Fix a double bracket to the middle hole, and fix two 2" strips to it.  The other ends of these strips form part of the pulley wheel bearings at the end of the jib.  These are 1/2" pulleys without boss, and are running free on a 2 1/2" rod.  Fix jib bracing built using narrow strips according to the photograph, which closely follows the prototype.   A weight overload device is fixed between the angled bracing near the base.   It is built from two 5 1/2" double angle strips, between which are fixed four 1 1/2" double angle strips and attached to the bracing.  1/2" pulleys run freely on rods between brackets. 

Attachment of jib
Four 7 1/2" strips are required as the links between the crosshead and the base of the jib. The ends of the strips are held on the cross head rods by collars.  Place the jib in position at the hinge, between the 1" corner brackets on each side and run 1" rods through, fixing them in place with collars.  Attach the links to the base of the jib, using a transverse 6 1/2" rod and eight collars.  Tension loads are spread by adding a 3 1/2" strip on each side to the jib in line with the links.

Pulley Blocks
Each of the four Pulley Block cheeks are built from two 1" corner brackets.  The cheeks are joined to each other by 3/4" bolts.  Two 1/2" pulleys are positioned on rods between the cheeks.  A small forked piece is fixed to the lower free hole of the cheeks.    A transverse bar is formed from two 1 1/2" narrow strips bolted to the sides of a third forked piece.  The bar is fixed to the pulleys blocks with 3/4" bolts.

The sheaves
Run the wire from each drum through its weight overload device pulley, and onwards over the jib head pulleys, twice round the pulleys blocks, and finally attach to the 2" strips at the jib head.     Ensure that the transverse bar is horizontal by adjusting the pinion at the winding drum. 

Builder's note  - If this crane were built with a base 12 1/2" square, it would be on the same scale as the Meccano blocksetter.  The limiting factor would be the lead screws for derricking. 


Cowans Sheldon 8118

    

Blocksetter size!                                             In 1972, Radio Controlled 

Michael Adler - February 2002