car trench of Calisi
Armored Car Concept - nobody built
Patents are strange things. Some of them are clearly crazy flights of fantasy without common sense or real use, and others are solid interpretations of real projects that are built. A third type is one where the inventor has an idea that looks good on paper, but that would not be usable in the real world. The armored car that crosses the Calisi trench is one of those ideas.
Side views of Calisi's war machine showing the rails in the raised and lowered positions. Source: patent: US1307238
The inventor and design
Adriano Calisi was an Italian citizen who lived in Waterbury, Connecticut when he filed for a patent on January 18, 1919. He came up with the idea of combining the road speed of an armored car with the off-road capabilities of a tracked vehicle. The concept was quite simple on paper. An armored car with wheels (called them War Cars) with a pair of tracks in front on "arms" to support.
With the rails fixed in place, the War Car is free to drive unhindered during normal operations. After encountering an obstacle, such as a pit or a trench, the crew would lower (by means of chains) these rails to cover the gap. The chains used to move the rails go inside the vehicle and connect to a winch connected to the engine inside the vehicle. The vehicle then crosses the space above the rails with the rails still attached by chains that open as the vehicle moves forward.
The Clever Bit
So, the vehicle went through the trench and has to retrieve those rails safely. This is done simply and elegantly by going back into the chains. The chains are fixed on two points on the support uprights on the rails and those uprights are hinged in the middle. When the chains are pulled back, the hinge gives way and the support posts bend to be narrower than the distance between the front wheels. Withdrawed completely forward, they are then lifted and restored to a position ready for use the next time.
The problems with the idea are obvious. First, those rails protruding from the front would themselves be prone to damage and loss as they are very vulnerable to the effects of rough terrain or enemy fire. The idea of stopping to retrieve the rail later means that you have to stop on the enemy side of the obstacle just to retrieve this bridge - this means that the next vehicle should do the same and so on. All this potentially even under enemy fire. It's not just a bad idea, but probably fatal on the battlefield.