Drawing of the gantry crane - continued

Rails and hoist trolleys

I don’t have a photo showing the trolleys rails. Basing on the diagram, I felt that it would be sufficiently similar to put rectangular or even square profiles of about 70 mm. It is also necessary to provide mechanical and electrical end stops for limit switches.

As for the trolleys, the matter is more complex, and I have only partial views. Here, as for other details, the shape of the hoods has evolved over the years. I want to represent the older models, with the cross travel electric motor protruding at the rear. One may think it was to improve ventilation.

First here is a picture of the exterior side, where we can clearly see the bonnet of the motor fan protruding out of the hood. Note the special shape of the hood.

Note: I emphasized the hood limit on the sky by a stroke, because it was very little visible.

Trolley rear view

On the inside, it is even less obvious, with an electrical connection box, probably a traction device for the festooned power cable, the messenger track (cable support rail), and the relative position control system of the two trolleys, which seems quite different from the one that can be seen on more recent cranes.

In the absence of a more precise picture, I will be led to simplify a lot, rather than to invent.

Trolley front view

  1. Electrical connection box
  2. Position control system
  3. Messenger track
  4. Guardrail
  5. Rail holder

Here is the result of these cogitations. For the dimensions, I first based myself on those of the diagram, especially for the wheelbase (1500 mm). Once modeled, I realized that the trolley size was too large, inconsistent with the photos. So I selected a picture almost front view whose perspective I rectified. From this picture, and based on the length of the girder, I recalculated the trolley size:

Photo of the trolley on the girder

I applied a coefficient of 75% on the length, which gave me a value of 1875 instead of 1855 on the image, a very close value. On the other hand, there is no change in the width: the distance between the rails must be respected, unless we assume that all the dimensions have been changed between the successive generations of gantries… I also preserved the wheel diameter (300 mm), already small, that it would have been dared to reduce even more.

Drawing of the trolleys

Pulley block

The pulley block is not the most complicated piece, but here again I will have to make assumptions. It consists of two hollow cylindrical casings containing the pulleys, put together by a piece of indeterminate shape, which I chose to make parallelepiped, which supports the hook. A kind of sheet metal belt encloses the whole horizontally.

Photo of pulley block

For the overall dimensions and for the hook, I had the same problem of size too big compared to the photos. The old real pulley block could not have the measured diameter of 800 mm. As for the trolleys, I reduced its dimensions a little arbitrarily to 75%, hence a retained diameter of 600 mm.

Drawings of the pulley block

Load plate and logo

I also installed the maximum load plate and the SNCF logo. I would not talk about it if it had not been a problem for me. Indeed, neither simple text (Drawing / Text) nor a bitmap image (Insert / Raster image...) accepted to display in Realistic Rendering mode. I had to declare the images as Material “pasted” on plates drawn as a Region.

Progress report

Here is an overview to conclude this step, with the load plate and SNCF logo inset.

View of gantry crane with its hoists

To be compared with this picture (see also here).

View of Dunkirk gantry crane

The top platform is longer on my model than on the original — but conforms to the diagram. It seems that over the years, all the platforms have been extended. I think, however, that I will leave it as it is, otherwise I would have to modify the electric cabinets without documentation.

What’s next?

To do: improve the drawing of the long travel motors, draw the various cables and wires, the three-phase current pickup system, and, above all, model the spreader. The latter is a rather complex device; maybe it will be enough to evoke it (frame, locks and possibly gripping arms for semi-trailers).