Screw-Propelled Vehicles: Surprising Advantages in Warfare

What is the best way to traverse difficult terrain?

That is a question that military leaders, engineers, and even common farmers have been asking themselves for millennia. For most of that time, animals such as horses, donkeys, camels, and even elephants were the best available options as they could be ridden through areas that most people could not easily travel on foot; however, everything changed with the advent of the steam powered engine. Suddenly, generating locomotion became a much easier task, and as such, a whole new world of transportation technology was developed in a very short time.

Within decades, trains were rolling across nearly every continent on earth and, soon after, the first automobile was created. But, as great as these advancements were for mankind, they brought with them many different logistical challenges—not the least of which was how these newfangled motorized vehicles could best make contact with the ground.

Today, the ubiquitous rubber tire is the most common way of ensuring that your personal vehicle grips the road as intended; however, it has significant shortcomings when traversing mud, snow, ice, or basically anything that is not a solid, textured surface. Because of this, in certain driving conditions you may find yourself sliding across icy pavement or spinning idly in the mud. Off-road and winter tires with specialized treads exist to mitigate some risk, but they can only do so much.

Today, we will be looking at one of the strangest and certainly oddest-looking examples of mankind’s ongoing quest to find the best wheel/tire alternative: the Screw-Propelled Vehicle.

Origin

Screw-propelled vehicles, as the name implies, are vehicles that uses large, flanged drive-screws, instead of tires or treads, to achieve locomotion. These screws, which are actually just hollow, cylindrical tubes with helical flanges spiraling around them, move the vehicle by rotating their bladed barrel or barrels beneath them to, sort of, crawl along the ground. This type of movement can provide many benefits depending on the vehicle’s intended use case.

For example, one of the earliest known designs for a vehicle of this type was introduced in 1868 by Mr. Jacob Morath for the purpose of transporting farm equipment across tilled soil. Morath’s designed relied on a single rotating screw for locomotion and a system of wheels and slides around the vehicle’s perimeter for balance and turning. Morath believed that, while other machines had significant trouble gaining traction in mushy farm soil, this new design that utilized both a screw and wheels would fare much better while also pulverizing pesky roots as it went.

Although the design was completed and patented, Morath never actually constructed this vehicle; however, its design did go on to inspire James and Ira Peavey, founders of the Peavey Manufacturing Company in Stillwater, Maine, to build something very similar. At the time, the Peaveys owned a logging company and liked the idea of being able to transport whole felled trees during Maine’s harsh winter storms. The Peaveys took Morath’s design, modified it to include a second drive-screw, and made the overall build much sturdier. Then, they put it to work.

What resulted was a mediocre performance that revealed several flaws in the machine’s design:

First, while the rotating cylinders had no problem gaining traction in hard-packed snow and ice, it struggled significantly in lighter, fluffier snow. Instead of sliding forward as intended, the machine would end up burrowing downward.

The second problem was, because the machine had been designed so stiffly and sturdily to allow it to carry heavy loads, it had significant trouble navigating the area’s narrow, windy roads. Moving forward was no issue—so long as the snow beneath it was solid—but turning was nearly impossible no matter the weather.

The Peaveys attempted to remedy these problems with a slight redesign; however, the design’s problems proved too difficult to overcome and neither prototype was ever mass produced.

Military Interest

For the next several decades, screw-propelled vehicles would see their fair share of civilian redesigns and minor advancements, but by WWII, the German military had also developed an interest in finding the best way to traverse snow, specifically the brutal snow along Germany’s eastern front against the Soviet Union. So, in 1944, the German army designed and tested a prototype that could pull one metric ton behind it while scaling minor inclines.

Physically, the vehicle looked like a large snowcat; although, instead of treads, it was perched atop a pair of wide, cylindrical tubes. These tubes were powered by two separate drivetrains which allowed them to spin at different speeds independent of one another.

All of this may sound rather complicated, but operating one of these vehicles was not that much different than driving a treaded tank:

Inside the crew cabin, two levers on either side of the driver’s seat allowed for independent control of the speed and direction of each cylinder’s rotation. To accelerate, both levers were pushed forward simultaneously and with equal force. This caused both cylinders to begin rotating—although, it is important to note that they did so in opposite directions. That is to say that, while moving forward, one cylinder rotated clockwise while the other rotated counterclockwise. This way, the two cylinders counteracted each other’s lateral forces, and the craft was able to move in a singular direction.

As the cylinders spun, their blades dug into the snow below, and the vehicle was pulled forward. To reverse, they pulled back on both levers with equal force and the direction of the cylinder’s rotation was reversed and, in turn, the vehicle.

Turning left or right was achieved by simply adjusting the amount of power delivered to each cylinder. For example, to turn left, the right cylinder was given more power which resulted in the right side of vehicle moving faster than the left. This method of turning was, once again, similar to that of a treaded tank; although, this screw-propelled vehicle had one additional movement pattern that most tanks could never even dream of.

As I said earlier, both screws rotated in opposite directions to counteract each other’s lateral forces; however, they could be made to spin in the same direction by pulling back on one lever while simultaneously pushing forward on the other. The result of the screws spinning in the same direction was a lateral movement similar to that of a crab. So, in addition to moving forward and back, these vehicles were also capable of sliding side-to-side.

This unique movement pattern is rarely seen in modern vehicles and was one of the screw-propelled vehicle’s biggest selling points: Versatility.

Around this time, the United States also began to fund their own research into similar vehicles; however, neither the US nor Germany could ever perfect the design to the point that it would be practical for wartime use. No matter what they tried, the vehicle simply did not perform up to their standards and, as a result, neither countries’ design was adopted for large-scale production and mobilization.

Two decades later, during the Vietnam war, the United States once again renewed its focus on building a working screw-propelled vehicle by ordering research into an amphibious vehicle that could traverse Vietnam’s wetlands. Because the cylinders of most screw-propelled vehicles are hollow to reduce their weight and the number of resources required to build them, many were also amphibious, meaning they could move freely between water and land.

The result of this research was two versions of a screw-powered, amphibious vehicle: the Marsh Screw Amphibian and the Riverine Utility Craft. Moving up to 14 MPH in swamps and 8 MPH in open water, both crafts proved adequate for water-based use; however, neither could gain sufficient traction on land which resulted in a pathetic 1.6 MPH average.

The mobility problems didn’t stop there. Soon, the Americans discovered that driving on paved roads often resulted in the blades of the cylinders being bent, broken or otherwise damaged. The roads themselves also took a beating as they cracked and warped underneath the vehicles considerable weight. Tires and treads allow for a healthy distribution of a vehicle’s weight; however, screws do not and oftentimes put pressure on a much smaller surface area.

In addition to this, while in combat and under fire, the hollow cylinders could easily be punctured by bullets which resulted in them filling with water, mud or dirt and losing their buoyancy. At that point, they were left with an amphibious vehicle that could traverse neither land nor water effectively. As a result of these difficulties, both designs were scrapped without ever seeing mass distribution.

During the Cold War, the Soviet Union managed to be the first country to push the idea from a prototype to a functioning vehicle and deploy it for use in real-world scenarios. The solution that they came up with was a combination of two massive vehicles: a six-wheeled truck known as the ZIL-4906 and a screw-driven ZIL-29061—two of the most uninspired names ever written; although, I suppose they are on-brand for the Soviet Union.

The larger and more traditionally driven ZIL-4906 had a flatbed for hauling the smaller ZIL-29061 as well as a crane for unloading it. Together, the two could overcome just about any obstacle. The larger craft on wheels could drive fast and far, and when they ran out of road, the smaller screw-driven vehicle could be unloaded to continue the mission. The pair were primarily used to locate and collect Soviet Cosmonauts who had landed in the vast and unforgiving Siberian wilderness.

The 29061 weighed 4,400 lbs. (or 2 metric tons), topped out at 28 MPH in snow, and had enough power behind it to down large trees. Seeing as it was also amphibious, it could reach speeds of 10 miles-per-hour in open water, and about 12 miles-per-hour in swamps. Approximately 20 were produced and a couple were in service all the way up until the fall of the Soviet Union.

Final Thoughts

Today, screw-propelled vehicles are rarely used for any purpose outside of extremely niche industrial situations. Their slow and sometimes sluggish handling on land and propensity to sink in water makes them an ineffective wartime tool, and as of today, most existing screw-propelled vehicles are restored museum pieces that have been kept as an oddity or small one-foot-long RC models.

While the concept itself may be interesting, many countries throughout the last century have tried and failed to find a practical use for them and, with the advancements of drone warfare and long-range and autonomous fighting, it’s unlikely that they will ever see large-scale use in the foreseeable future.

Sources

Image

Screw Vehicle, by Vyacheslav Bukharov, August 2022, Wikimedia Commons, Creative Commons Attribution-Share Alike 4.0 International license, https://commons.wikimedia.org/wiki/File:UMMC_Museum_(August_2022)_-_24.jpg