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Post Info TOPIC: Levavasseur Theory
James H


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Levavasseur Theory
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http://en.wikipedia.org/wiki/Levavasseur_project

The article on Wiki and the one in Tank Zone (which might both have been written by François Vauvillier) describe the tracks of the vehicle thus:

The all-terrain mobility necessary to this machine is achieved by a contraption equivalent to a wheel of very large diameter. This contraption, called an "articulated wheel", consist in a sort of rim composed of links ("voussoirs") connected together by bolts around which they can rotate, and with an elastic connection tending to close up the space between the voussoirs.

In the drawings, the vehicle is shown with what look very much like flat track plates. However, the choice of the term voussoir is very interesting. Its sole definition is 'a wedge shaped stone used in the building of arches', sounding more like a tapering block than a plate.

I'm interested by the use of this very specific term. The Hornsby and one or two other machines of the period travelled on blocks. If the Levavasseur also did, and they were tapered towards the inside circumference, that would allow them to compress on the inside as they travelled round the sprockets and an unbroken surface would be presented on the outside circumference. (In the same way that you can bend a piece of wood by making a series of cuts on one side and flexing it towards them)

It seems to me that an advantage would be a reduction in the 'nutcracker effect' that was such a problem for the Hornsby, Pedrail, etc. This pic of the tracks of the 1869 Minnis Tractor (posted some time ago by Laffetenheini) seems to show an arrangement like the one I've described.

I wonder if anyone, especially François, Michel, or other French-speakers, think this makes sense.



-- Edited by James H on Sunday 28th of June 2009 10:53:32 PM

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Tanker


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Bonjour James,

I have not other informations about Levavasseur project.

I just want to answer about the terms "Voussoirs", who is also a British word.  
In Nuttall's Standard Dictionnary - 1890 :
"Voussoir : one of the truncated wedgelike stones forming part of an arch - (fr : voussure : curving of an arch) "

I agree that the tracks on your photo, probably, look like to Levavasseur's idea.

And I don't explain the "Elastic connection between voussoirs"

Michel

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James H


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Salut, Michel.

Voussoir must be a corruption of voussure.

I don't understand the 'elastic connection' part either, but there might have been a set of springs or some other material that pulled the sides of the blocks against each other.

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"Sometimes things that are not true are included in Wikipedia. While at first glance that may appear like a very great problem for Wikipedia, in reality is it not. In fact, it's a good thing." - Wikipedia.
françois vauvillier


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Bonjour James,

No sorry, I am not the writer on the Wiki article. I did not even know it.
I drew all my technical informations (published in TankZone #3) from Duvignac's Histoire de l'armée motorisée (very short on proper tanks but very detailed on motorized artillery. In fact another 'bible').
I tried hard to understand what Levavasseur meant by his description, before giving drawing instructions to Laurent Lecocq who illustrated the project.
The 'estimated profile' published page 9 could still be improved but we had to keep as close as possible to the original sketch and description, while putting a proper75mm gun at a correct scale.
All this preparation work helped me to understand (supposedly ?) what was described.
Here are my views of the 'voussoirs' (the word is absolutely correct in French ; it refers, exactly as in English, to any indistinct stone of a voult, not the keystone = clé de voûte).
In a stone voult, only the inner part is rounded.
But Levavasseur refers as an 'articulated wheel' : this implies (in my opinion) that the outer side of the wheel has to be rounded.
Therefore, I asked Laurent to illustrate this : you can see on our '1/72 estimated profile' that each track link has a bulky outside suface. In principle, the diameter of the curve should be the same as the diameter of the full track (=wheel) if it was to be put in the shape of a perfect circle.

Another problem was the number of tracklinks. The original Levavasseur sketch (as published by Duvignac, I hope the original was the same) shows only 19 links. We had to keep to this, thus making long, likely unsuitable, links. I explained this in my note A, stressing that, if the design had been realized, the links would have surely been reduced at least by half.

This is my interpretation of the Levavasseur idea, rather that the Minnis type of track you show (on photographs) on your post.

But this is, of course, subject to endless discussion, since the Levavasseur projet did not go beyond the description and sketch (as fas as I know).

We have to be very careful in our interpretations of what was in a man's mind more than one hundred years ago.

A factor towards my interpretation is the post-WWI type of " boat-shaped" tracklink used on the B tanks and R 40 light tanks. This design allows a variable pressure of the vehicle on the soil, whether it is solid or muddy.
But I would not swear Levavasseur went that far in designing his 'articulated wheel'. We can just assume that this is the first French recorded military attempt for a caterpillar.
Another of our great men, Clément Ader, the pionnier of the Air, designed a proper caterpillarin the 1870's , but as an entertainment goat-drawn carriage for children in the Jardin des Tuileries.

Regards

François





-- Edited by françois vauvillier on Monday 6th of July 2009 02:51:00 PM

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