Schneider CA1 : The first French tank
The project.
The idea came from the creation of an exhibition network with the theme of rail supply during the First World War at 1/43rd scale. There is not much railway material available on the market compatible with this era: practically everything has to be created from scratch. On the other hand, if we accept the small difference in size, small military equipment intended for 1/48th scale can be used without disfiguring the realization. While doing research I found that the transport of tanks on flat cars was an original subject to be treated.
It therefore remained to find the wagons and of course the load: the tanks.
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To start, I spotted on Shapeways a Renaut FT which seemed correct to me, at 1/48th. So I ordered on the site in question, two copies which were delivered to me (at 1/43rd because I had previously asked to "re-scale" them to the right size. Unfortunately, if the look there it is, the finesse is not there....
Disappointed, I decided to set my sights on a lesser known but equally interesting machine, the Schneider CA1 tank.
I then made the decision to make it from scratch with my resin printer. Drawn at 1/43rd, it will be easy to reduce it if necessary to 1/48th.
A brief history of the machine
The story begins with the stabilization of the front at the end of 1914. Very quickly, ideas spring up to pierce the front - coming from various inventors -, but none will be valid. The idea of an "armoured battleship" is however gaining ground, an idea shared by a certain Colonel Estienne.
From these reflections, conducted simultaneously on both sides of the Channel, will be born on the one hand the Mark I tanks, on the British side, and on the other hand the Schneider tank which will arrive on the battlefield after its British counterpart.
Underpowered with its Peugeot engine, badly armored, its first appearance in combat was a bitter failure, the Germans having learned how to fight against these large machines, which were not very agile and slow.
Among its faults, the tanks located inside the hull and not protected from shrapnel, its inefficient 75BS gun, especially badly placed on the side (only one side...). In addition, the Germans have developed the K bullet specially developed to pierce the armor of tanks.
Quickly, the French military organization adapted to this new weapon, the tank itself ordered with 400 specimens, was improved, while keeping some flaws like its barrel. He made an honorable career until the armistice or the last surviving copies will be of all the fights.
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Realization of the "beast"
On this 3D view of the drawn tank, we can see the junction between the chassis and the body. This real junction will be used to hide the link between the two main parts.
Before starting to draw the model, you must have plans... However, on the internet, there are many diagrams but all have different dimensions. We had to start by redesigning the tank by compiling the different sources.
After this stage, the actual study begins: To be able to print the tank with the Photon printer, its dimensions must be compatible with the dimensions of the printer plate, If you do not want to have any deformations during printing, it is prudent to keep a margin around the part to be made (at least 5mm if it can be done....)
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On the model, the chassis is well separated from the rest of the body. This will be the demarcation between the two main parts of the model. To facilitate painting, the tracks will be separated from the rest of the body. Nipple will allow the correct positioning of the tracks.
Finally, in order to better pass on the printer plate and always to facilitate painting, the cut-off tail will also be a separate part. To optimize printing, there will ultimately be three separate clusters:
- The box.
- The chassis.
- The right and left caterpillars, and the tail is cut (a second tail is provided on the same sprue).
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Finally, before going to the next step, you have to think about hollowing out the parts, leaving thicknesses
at least 1nm for the part to be strong enough.
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The Slicer : Chitubox
The different parts being studied and drawn, they must be placed on the clusters that must be made. The placement is done with an appropriate software, the printer being delivered with this utility.
However, looking on the forums on the internet, it appears that the free software "Chitubox" made it possible to do a very good job in a simpler and faster way than the Photon software...
The icing on the cake, this software is fully compatible with the printer... and for good reason: the same Chinese developers produced both software! Thus, you will not be lost by the ergonomics of Chitubox if you have started working with the Photon utility.
This type of software is called "Slicer" because its primary function is to cut your part into "slices". The advantage of Chitubox is that it goes very fast (just a few minutes with my 5 year old laptop for my most complex parts). However, I note some "crashes" when I request it despite the addition of RAM on my computer....
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Software screenshot. We can see in this view the support reduced in height so as to limit the printing time. Here the support protrudes a little from the platform at the front of the tank (area in brick red): it will have to be repositioned.
Preparation of parts before printing.
If the resin printer is capable of producing very thin parts, it quickly finds itself in difficulty to produce long straight parts.
This defect can be corrected - without actually remedying it completely - by slightly tilting the parts, at least on the X-Z or Y-Z axes. I don't do it systematically because it has the disadvantage of further reducing the printable surface.
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Another constraint of 3D printing: supports. As far as possible, they should be placed in an invisible part. Chitubox offers us the possibility of 3 different types of supports and to use all three types on the same piece.
Real view of the roof of the tank after assembly but before decoration. Only a light coat of primer comes to cover the model: we realize a slight aliasing due to the printing, aliasing which will disappear completely after painting....