Friday, June 08, 2018

How I constructed a timber gantry crane

 Having completed the sawmill (see How I constructed the sawmill) and its interior (see How I detailed the interior of the sawmill), I then started construction of a gantry crane to unload and load wagons.

Background research

As with the sawmill, there wasn't an enormous amount of information on the web about gantry cranes during the period when my railway has been in operation (1890s - 1930s), though I did manage to track down this drawing from the magnificently helpful Wagon Loads and Materials Handling website:

Using this image as my guide, plus a few more photos of gantry cranes which I gleaned from the net, I set about constructing something similar.

The gantry

For the main load-bearing beams of the gantry, I used 15mm square stripwood - which in 16mm scale is nearly 1ft square.

Two 660mm lengths were cut.

 I decided my crane would have four pairs of legs and so eight 180mm pieces of 15mm square stripwood were cut.

I decided to add additional bracing to my legs and so eight pieces of 10mm x 15mm stripwood were cut. Their overall length was 192mm, from which angles were cut at each end, one 44mm  and the other 4mm from the ends - as in the photo.

Eight more pieces of 10mm x 15mm were cut - 30mm long, from which an angle was cut 3mm from one end, as shown.

Twelve 50mm long pieces of 10mm x 15mm were cut, with 45 degree angles at each end, as shown.

The legs were then ready for assembly on the main beams.

Firstly, two pieces of code 200 rail (from a length of Peco SM32 flexitrack) were cut to a length of 662mm. A vee-shaped notch was filed into each rail, 10mm from the ends,

The ends were then bent upwards .......

...... and soldered.

Brass pins were tacked into the main beams at intervals of 110mm. The were positioned off-centre to allow for the width of the rails.

The heads of the pins were snipped off and filed flat, leaving about 3mm protruding.

The rails were cleaned of oxidation at 110mm intervals and then soldered to the pins ...

...... until all the pins had been soldered.

 Then, the legs were glued to the main beams, 220mm apart.

 The 50mm diagonals were then glued into the corners between each leg and the main beam.

 When the glue had set, the diagonal supports for each leg were glued on, making sure they were level with the bottom of the leg. I used superglue with accelerator spray and a brass panel pin to make sure they became fixed quickly and accurately.

The cross-brace was then glued into the angle.

When all the legs were done, two pieces of 15mm square stripwood were cut to a length of 250mm and glued into place between the two main beams (the uppermost beam in the photo is positioned there temporarily while the glue sets to help ensure the legs are perpendicular).

When both cross-beams had been glued, the gantry was test-fitted in its location to make sure my measuring had been accurate .......

...... which fortunately, it was!

Now the the gantry was more or less finished, I turned my attention to the travelling and lifting parts of the crane; ie the bridge and the trolley.

The bridge

The length of the bridge was, of course, dictated by the space between the rails on the gantry. Two pieces of 9mm square stripwood were cut to a length of 289mm and another two pieces cut to a length of 241mm. The shorter pieces were glued to the longer pieces with a 24mm overlap at each end.

Two pieces of code 200 rail were cut to a length of 309mm. Notches were filed 10mm from each end were and the ends turned up and soldered (as above).

Brass panel pins were taped in at intervals of 80mm along the top of the longer pieces, and the rails soldered to these (as above)

Eight 90mm long pieces of 9mm square stripwood were cut and glued together in pairs. Two of each pair were then glued beneath the bridge, as in the photos below.

These now formed the main components of the end trucks on which the bridge would run. The wheels for the trucks were made by removing the wheels from a skateboard toy found in my local 50p shop.

The wheels were superglued to 12mm diameter washers designed to be used with pop rivets - ie with a 3mm  diameter hole.

The mounting brackets for the axles were made from 5mm x 8mm rectangles of 1.5mm thick plasticard on to which 5mm lengths of 5mm Plastruct tubing were glued. A couple of Cambrian Models bolt heads finished off each bracket.

The brackets were glued beneath the end truck beams and 24mm lengths of 3mm diameter brass rod ....

A 296mm length of 3mm brass rod was passed through two set of brackets on both end trucks to provide power for moving the bridge.

I decided that the motive power for moving the bridge would be similar to that provide in the prototype drawing above, namely a chain wheel. I also decided to add some gearing to reduce the amount of effort needed. For the chain wheel, I used a 48mm diameter cartwheel (obtained online from

The rim was too broad for my purposes and so I slimmed it down by inserting it into a mini drill and reducing its thickness with the blade of a craft knife.

The wheel was mounted on a 3mm diameter axle, together with a small spur gear (from Technobots) and fixed to a couple of brackets positioned on the upper beam of one end-truck - as shown here.

At this stage, all the smaller plastic and brass parts were given a couple of coats of Halford's grey primer followed by a couple of coats of satin black, using aerosol rattle cans.

The gearing mechanism could then be finished off, with a larger spur gear mounted on the lower axle (you may notice the paper packing wrapped around the axles to pad them out to be a more secure fit in the 3.9mm holes in the gears).

The wheels were also fixed into place at this stage, a dab of superglue holding them in place on the axles.

Apart from painting, the bridge was now complete and so work was begun on the trolley.

The trolley

Working on the axiom that simple is best, The trolley was made from four 'skateboard' wheels (as outlined above), two plasticard sides (30mm x 35mm for the upper part, plus another 20mm narrowing down to 10mm at the base). Four 8mm long pieces of 7mm diameter Plastruct tube and two 8mm long pieces of 5mm tube were cut to act as spacers.

3mm diameter holes were drilled 5mm from each of the upper corners of the side pieces ....

... and the 5mm tubes glued over them. The 7mm tubes were  glued as shown.

25mm long pieces of 3mm brass rod were inserted in the holes (to help with alignment while the solvent set), and the other side of the trolley was glued into place.

While the solvent was hardening, a hook and the sides of the hook assembly were fashioned from 1.5mm thick plasticard. The sizes weren't critical, I just made them to a size which looked about right (the 10mm squares on the cutting board give an idea of scale).

These were assembled, with some 1mm diameter brass rod.

The wheels were then pushed on to the axles .....

..... with a dab of superglue to hold them in place. By the way, I use cocktail sticks to apply superglue when only small quantities are required.

 The trolley was then slotted into the bridge and left loose so it could be adjusted as needs be.

I was fortunate that, after converting some Bachmann Jackson Sharp coaches into something vagely resembling Leek & Manifold coaches, I has some trusses left over (see How I converted Bachmann Jackson Sharp coaches into Leek & Manifold(ish) coaches)

Holes were drilled at appropriate places beneath the bridge and the trusses superglued into place. It was sheer coincidence that the length of the bridge was appropriate for the trusses!

Apart from painting and titivation, the gantry crane was now complete.

Painting and titivation

Lengths of fine chain were wrapped around the chain wheel and the trolley supports to simulate the chain hoist mechanisms for moving the bridge, moving the trolley and raising/lowering the hook. Once cut to length, the chains were fixed in place using the ubiquitous superglue.

I decided that it would be sensible for the workers in the mill to construct some sort of heavyweight bench to allow the logs to be rolled on to the saw carriage. Inevitably, this would have been constructed from large baulks of timber. Consequently, I used 15mm square and 10mm x 15mm stripwood. To give the bench a slight angle down towards the carriage, one of the supports for the bench was made from two layers of 15mm square stripwood and the other was made from one piece of 15mm square and one piece of 10 x 15mm stripwood.

The slats were made from 10 x 15mm stripwood glued on their narrower side.

An extension to the saw carriage track was made using the same technique as outlined above and the two were fixed to a 355mm x 235mm piece of 10mm thick plywood to match the base of the sawmill. Everything was given a couple of coats of dark brown acrylic paint, liberally applied. The rails were picked out in rust colour and some weathering was applied to the bench and the supports to the track.

The intended site was landscaped, using my usual approach of a concrete mix to bring the ground up to sleeper- or rail-height, followed by a mix of sand, grit, soil and cement dry-brushed into place, wetted and then dribbled with SBR additive.

The gantry was painted dark brown and the rails picked out in rust colour before being screwed to the base on which the log bench had been fixed.

The bridge was also painted in the same way and the whole structure positioned for a photo-shoot.

I have made the sawmill and the gantry crane removable. I doubt they will survive weather conditions which this part of the North West of England will throw at them. They reside in a weatherproof storage cupboard when not in use, and take no more than a couple of minutes to deploy before a running session.

I am very pleased with the outcome. I did not work to a scale plan or drawing, but resolved each part of the build as I went along. I need to add a few more fine details, particularly stacks of sawn timber and also a boiler house for the mill engine in the sawmill. But this area of Peckforton Station is now beginning to look more businesslike.