The Skeleton Tank was an experimental prototype tank

Tank

A tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility, tactical offensive, and defensive capabilities...

 built in 1918 by the Pioneer Tractor Company, Winona, Minnesota

Winona, Minnesota

Winona is a city in and the county seat of Winona County, in the U.S. State of Minnesota. Located in picturesque bluff country on the Mississippi River, its most noticeable physical landmark is Sugar Loaf....

.

The objective of this prototype was to develop a lightweight vehicle capable of crossing wide trenches

Trench warfare

Trench warfare is a form of occupied fighting lines, consisting largely of trenches, in which troops are largely immune to the enemy's small arms fire and are substantially sheltered from artillery...

 in a manner similar to the then-conventional heavy British

United Kingdom of Great Britain and Ireland

The United Kingdom of Great Britain and Ireland was the formal name of the United Kingdom during the period when what is now the Republic of Ireland formed a part of it....

 tanks. However, unlike the British tanks with their fully enclosed chassis, the Skeleton Tank achieved the requisite lozenge shape by supporting its tracks

Caterpillar track

Continuous tracks or caterpillar tracks are a system of vehicle propulsion in which modular metal plates linked into a continuous band are driven by two or more wheels...

 with a skeleton-like framework formed from ordinary iron pipes joined by standard plumbing connections. Suspended between these track frames was an armored fighting compartment carrying a machine gun turret. This arrangement dramatically reduced the weight of the vehicle as compared to the larger British and French

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 tanks and while preserving the trench-crossing capabilities of those machines, and there was a belief that most enemy bullets and cannon rounds would pass harmlessly through the structure. However, it eliminated the possibility of mounting weapons in sponson

Sponson

Sponsons are projections from the sides of a watercraft, for protection, stability, or the mounting of equipment such as armaments or lifeboats, etc...

s as in the British tanks and thus limited the armament that could be carried.

Motive power consisted of two Beaver 50 hp four-cylinder engines with a final drive joining to a gearbox suspended between the rear horns of the tracks. This allowed a maximum speed of 5 mph.

The Skeleton Tank weighed 9 ton

Ton

The ton is a unit of measure. It has a long history and has acquired a number of meanings and uses over the years. It is used principally as a unit of weight, and as a unit of volume. It can also be used as a measure of energy, for truck classification, or as a colloquial term.It is derived from...

s and carried a boxy fighting compartment protected by a half inch of armor, which was in line with the armor thicknesses on other Allied

Allies of World War I

The Entente Powers were the countries at war with the Central Powers during World War I. The members of the Triple Entente were the United Kingdom, France, and the Russian Empire; Italy entered the war on their side in 1915...

 tanks. The crew of two consisted of the driver and the commander/gunner who manned the .30 caliber

Caliber

In guns including firearms, caliber or calibre is the approximate internal diameter of the barrel in relation to the diameter of the projectile used in it....

 machine gun

Machine gun

A machine gun is a fully automatic mounted or portable firearm, usually designed to fire rounds in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute....

 in the turret

Gun turret

A gun turret is a weapon mount that protects the crew or mechanism of a projectile-firing weapon and at the same time lets the weapon be aimed and fired in many directions.The turret is also a rotating weapon platform...

. It was 25 feet long, which compared favorably in trench-crossing potential to the then-standard heavy British Mk IV

Mark I tank

The British Mark I was a tracked vehicle developed by the British Army during the First World War and the world's first combat tank. The Mark I entered service in August 1916, and was first used in action on the morning of 15 September 1916 during the Battle of Flers-Courcelette, of the Somme...

 and Mk V

Mark I tank

The British Mark I was a tracked vehicle developed by the British Army during the First World War and the world's first combat tank. The Mark I entered service in August 1916, and was first used in action on the morning of 15 September 1916 during the Battle of Flers-Courcelette, of the Somme...

 tanks with lengths of 26’5” but weights of 28 to 29 tons, and the French Schneider CA1

Schneider CA1

The Schneider CA1 was the first French tank. It was inspired by the need to overcome the stalemate of the trench warfare of the Great War.-Caterpillar development:...

 and Char d'Assault St. Chamond

St Chamond (tank)

The Saint-Chamond was the second French heavy tank of the First World War.Overall an inadequate design born of commercial rivalry, the war ended before it was replaced by British heavy tanks.-Development:...

 with lengths of 19'9" and 28'11" and weights of 13.5 and 23 tons respectively. It was 8’5” wide, narrower than the 10’ to 12’5” of the British tanks, and slightly higher at 9’6” vice 8’8” for the Mk IV/V due to its turret. It was never ordered into production.

The cosmetically restored Skeleton Tank is preserved under a canopy at the United States Army Ordnance Museum

United States Army Ordnance Museum

The U.S. Army Ordnance Museum is a museum that is in the process of being re-located to Fort Lee, in Fort Lee, Virginia. Its previous building—at Aberdeen Proving Ground in Aberdeen, Maryland—was closed in September 2010, although many outdoor exhibits are still accessible to the...

 at Aberdeen Proving Ground

Aberdeen Proving Ground

Aberdeen Proving Ground is a United States Army facility located near Aberdeen, Maryland, . Part of the facility is a census-designated place , which had a population of 3,116 at the 2000 census.- History :...

, Maryland.