A light vehicle with a heavy tank’s crossing outline
The Skeleton Tank, also called the Spider Tank, was an American experimental vehicle built in 1918 by the firm identified in the cited sources as the Pioneer Tractor Company of Winona, Minnesota. Its defining feature was an open structural frame surrounding a small armored crew compartment. The frame gave the tracks a long, rhomboidal outline without enclosing the whole vehicle in a continuous armored hull. Sources
The intended compromise was straightforward: retain a long obstacle-crossing footprint while reducing the weight that a fully armored heavy tank would carry. The account commonly reports a weight of about nine tons and a crew of two. Those figures describe a prototype, not the accepted standard of a production tank. Sources
Only one completed example is established in the available accounts. Its trial history, later museum condition, and different photographs are states of that same vehicle. The source also records an uncertain gun-armed proposal; it is not counted as a second finished tank. The vehicle's existence is well established, but many precise performance and internal-layout claims still depend on later reconstructions. Sources
Development and the identity of the builder
The project belonged to the American effort to develop armored vehicles during the First World War. Edwin M. Wheelock is associated with the design. Published accounts give earlier-origin claims, including a possible prewar conception, but does not supply a demonstrated chain of patents or drawings establishing every proposed influence. Those claims remain unconfirmed rather than being allowed to turn resemblance into proven ancestry. Sources
A later Army account cited in the cited sources reports a government payment of fifteen thousand dollars to Pioneer for the prototype. The vehicle was sent for evaluation at Aberdeen, with the available evidence placing testing in the 1918–1919 period. It did not become a production program before the war ended, and no later series is established here. Sources
One Published accounts describe uses Pioneer Motor Car rather than Pioneer Tractor. That is a source-identity discrepancy to resolve against contracts and company records, not permission to overwrite the original the cited accounts. Similarly, generic United States Army trial descriptions shared with another prototype do not make the Skeleton Tank and Holt Gas-Electric Tank duplicates. Sources
Frame, crew compartment, and armament
The long track assemblies were connected by an open framework using pipe and other structural members. Within that frame, a much smaller armored box protected the crew, with a small turret above. The design concentrated protection around the occupants rather than around the whole outline of the vehicle. Sources
Accounts describe approximately half-inch armor for the protected compartment. That does not establish a claim of continuous half-inch armor over the exposed frame, tracks, and mechanical equipment. The open structure is the very feature that explains both the weight saving and the design's potential vulnerabilities. Sources
A.30-caliber machine gun is the principal armament supported for the prototype configuration. A possible 37 mm installation remains a proposal or uncertain secondary description. Exact ammunition capacity, sight model, and the complete internal distribution of duties are not firmly documented. With only two occupants, driving, observation, command, and weapon handling would be concentrated into a small crew, but no measured workload assessment is established. Sources
The exposed structure also makes the surviving example useful for illustration. It does not make every component visible in a modern photograph an authenticated representation of the original trial arrangement. Restoration, storage, and later display conditions differs from the vehicle's construction state. Sources
Twin engines and the limits of reported performance
The powertrain is generally described as two Beaver four-cylinder gasoline engines. The accounts record an important ambiguity in output: some descriptions give approximately fifty horsepower per engine, while another reading treats fifty horsepower as the combined figure. Those alternatives materially affect any power-to-weight calculation. The present draft does not silently choose one and derive a supposedly exact performance ratio. Sources
The design transmitted power through shafts and associated gearing within its unusual structural arrangement. Published summaries commonly give a speed of roughly five miles per hour, but The available evidence does not establish a complete measured trial series covering endurance, turning, obstacle crossing, and reliability. The long rhomboidal shape was intended to improve crossing ability; intention and demonstrated results remain separate. Sources
Common structural materials might have made fabrication or repair easier, but that is not the same as evidence of low maintenance cost in field service. The prototype was not deployed as an operational fleet. Sources
Evaluation, custody, and preservation
The Skeleton Tank's service history is an evaluation and preservation history. The source identifies Army testing and later Ordnance Museum custody, not a combat unit. There is no supported overseas deployment, licensed production, export service, or sequence of combat losses. Sources
The account follows the surviving prototype through later museum documentation, including Aberdeen photographs and an October 2009 collection movement. A lifting photograph illustrates that transfer; it is not battlefield recovery. A 2014 Army preservation campaign provides another dated view of the same artifact and its condition at that time. Sources
Those dated records are not established as a fresh confirmation of current visitor access or present storage location. They document the vehicle's custody and preservation narrative at particular points. No original vehicle count is increased by a change in custodian, a repaint, a move, or the appearance of a second museum photograph. Sources
The concept remains an unusual answer to a real engineering problem: obtaining a long crossing footprint without the mass of a full heavy-tank hull. Its experimental status limits conclusions about tactical success. No documentary chain in the available descriptions establishes it as a direct ancestor of a later production family. Sources
Photographs as evidence, not substitute specifications
The image selection spans historical reproduction, modern museum views, a transport operation, and a preservation campaign. A photograph later reproduced in a 1947 reference does not necessarily date from 1947; the publication and exposure dates remains separate. The two 2007 Aberdeen images show different views of the preserved prototype, not separate models. Sources
The transfer and preservation photographs add valuable context beyond the basic silhouette. The cited evidence does not establish every detail of the engines, transmission, and crew compartment. Sources
Photographs and image credits
Background reading and references. Each photograph has its own source and credit.
Sources and further reading
Background reading and references. Each photograph has its own source and credit.
- Bell, T. Anthony. “The tank that never was: prototype makes state's endangered artifacts list.” U.S. Army, 12 September 2014. Official article
- Gaare, Dennis, Major. “Edwin M. Wheelock and the ‘Skeleton Tank.’” ARMOR, January-February 2002, pp. 35-38. Specialist article
- DVIDS. “Skeleton Tank.” Image record, 4 September 2014. Photo by Terrance Bell, U.S. Army Fort Lee.
- U.S. Army Center of Military History. “U.S. Army Ordnance Training Support Facility.” Official facility page.
- U.S. Army. “Ordnance tanks, artillery arrive at Fort Lee.” Official Army article, 2009.
- Tank Encyclopedia. “Pioneer Tractor Skeleton Tank.” Specialist secondary article.
- Wikimedia Commons. “File:AD1116719-014 Skeleton Tank.jpg.” Image page. 1947 U.S. Army work from Development of Armored Vehicles Volume 1; public-domain U.S. federal work.
- Wikimedia Commons. “File:Skeleton tank 1.jpg.” Image page. Mark Pellegrini, own work, 12 June 2007, U.S. Army Ordnance Museum, Aberdeen Proving Ground, CC BY-SA 2.5.
- Wikimedia Commons. “File:Skeleton tank 2.jpg.” Image page. Mark Pellegrini, own work, 12 June 2007, U.S. Army Ordnance Museum, Aberdeen Proving Ground, CC BY-SA 2.5.
- Wikimedia Commons. “File:US Army 52561 Title.jpg.” Image page. Yvonne Johnson, APG News / U.S. Army, 8 October 2009; public-domain U.S. Army work.
