Spingarde - Field Artillery Gun Codex Atlanticus Folio 32r
The name Spingarde was used to indicate a kind of war machine that was used to throw stones. The development of gunpowder changed the way in which the Spingarde was fired but the name stuck for a while.
The Leonardo design for the Spingarde cannon typically brings together many existing features into one device, the drawing from Folio 32r shown above shows firstly a cannon mounted on a carriage with wheels for mobility.
He then brings to it the ability to be aimed whilst the frame is staked to the ground to control the recoil. It does this by having a secondary carriage gimbal mounted on the fixed frame so that the cannon can be adjusted in yaw (side to side) and Pitch (up and down).
It has breech-loading of the powder and cannonball, a feature used to increase the rate of fire in battle as these breech blocks can be pre-loaded. Cannon of this type were generally known as Breech-loading swivel guns. Typical examples of this type of cannon are shown at this web site http://en.wikipedia.org/wiki/Breech-loading_swivel_gun The open space at the back end of the barrel was where the breech block would be fitted, and held in position by a wedge. Leonardo has brought some more precision to this design by introducing a screw connection between the barrel and the breech, a similar system used in modern weapons.
Finally, it has protection for the artilleryman loading and operating the cannon, a roof has been added and fixed to the barrel at the front and the pitch mounts at the rear.
All of the features were in existence around Leonardo’s time but he has developed some more detail into these features. Some of this can be seen in this additional sheet from folio 36. it shows 3 options for a Bombarde mounted on a gimbal.
To produce a functioning model from this Leonardo design I have used Folio 32r as a basic underlay and then built the model around it, trying to keep the proportions of the original whilst adjusting the details to produce a functional design.
I should point out that it is never intended for this cannon to be used in any way to fire projectiles, although it is based on Leonardo’s drawings there is no way of knowing that the unit would not explode if tried for real. I have not included a touch hole for this reason and strongly advise against trying it.
It’s not certain what size was intended for the original device but I have made this model 15 inch's long, (385 mm) which would equate to 1/10th to 1/12 scale.
The barrel and breech block are constructed much the same as the original intent but for the thread which is a modern style acme thread ¾ inch diameter.
Leonardo gives us very little to work with for the wheels of the cannon so this interesting page showing wagons and carts of the medieval period helps to determine the type of design to use.
I sort of expected we might be looking at solid wheels but it is clear from this that spoked wheels had been in common use for centuries before Leonardo’s time. I have however used thicker sections for the wheel spokes and rims to help compensate for the weight of the cannon.
Issues that arose during the course of the design mainly concerned the implementation of the gimbal to allow movement in pitch and yaw. The design in folio 32r has the barrel carriage mounted directly on the fixed frame with the gimbal shown trapped between them. Clearly, the carriage can't be moved up and down (pitch) if it is hard against the fixed frame so in my design the carriage has been lifted significantly to allow for the full movement indicated by the arc guide at the rear of the frame.
Another problem is the bottom handle on the arced frame is positioned in the centre and would clash with the handle at the back of the carriage, so I have replaced this handle with two handles mounted on the sides.
Leonardo has given no indication how the barrel is attached to the carriage, so I have used a rope to lash it to the carriage, which seems culturally appropriate. You may want to do it another way.
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