David W. Hansen, engineer, inventor, industrial engineering. He put his ideas and patents into practice by producing different prototypes of very original vehicles. Son of a Forest Ranger, David Hansen was born in 1935, and he lived 12 years in Nevada. He is graduated from :  High School in Moab 1953, Utah, Aero technology at Utah State 1955, Industrial engineering at Cal Poly 1964.

He worked for El Paso Natural Gas, Weyerhaeuser, Vickers hydraulics, McGill Bearings, Schurman Machine, TRW/Ross, NL Rucker, Spencer Fluid Power, King Bearing, Tracker Inc. and his own firm Iguana Technology.

During his 27 year working career, he worked as Manager, Engineering Consultant, Sales Engineer. He helped solve engineering problems dealing with bearings, hydraulics and power transmission at International Harvester, OBC, Frisch Bros, American Molding, Boeing, United Airlines, Hyster, Pacar, Kenworth, Freightliner, Ederer Crane, Tucker Sno-cat, Esco, Cascade, Tacoma Boat, FMC, and many others. David is very familiar with cranes, planes, boats and all types of ground vehicles used in construction, logging, marine, government agencies, as well as the formulas for statics, dynamics, speed, torque, capacity and system life.

He was a member of ISTVS (International Society of Terrain Vehicle Systems created by Gregory Bekker in early 60s) for 10 years and has almost 100 of the Journals. This engineer association is specialized in the study of soils related to land mobility and its papers are essentially theoretical. The majority of members are now from China and Japan.

He got the idea for his invention during business trips when he would look down from a plane and see 50,000 miles of snow-covered roads that no one could travel on in winter, and lakes that couldn’t be crossed without a ferry or a boat. He says :

“We’ve got plenty of room but we can’t take advantage of it because we don’t have adequate transportation. My dream is to improve that, to allow us all to have more room and to do it in a way that we don’t harm anything and we don’t tear things up,”

David took out patents for his all-terrain vehicles :

1 - ‘Low impact tracked vehicles’, 1994. US 5318141 https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US5318141.pdf.

2 – ‘Traction device for tracked vehicle, bolted on the tracks of the vehicle’, 1996. US 5547268


Hansen’s vehicles do not make ruts. That’s because they exert less than a pound per square inch of ground pressure thanks to wide tracks which are equipped with what Hansen calls “grousers.” He has redesigned the grousers six times.

The grousers are fitted with teeth on a base and are made of a suitable elastomeric material. The teeth are conical and aligned on the grouser. “The idea is you’re supporting a vehicle with the resistance to penetration of a rubber cone into the turf, snow, mud, rather than mashing things down. And then, when you need to maneuver, the end of the cone bends and becomes a little runner that glides through the material and doesn’t dig a hole”. It runs clean and provides low impact engagement in soft materials, avoid sliding of the tracks, as well as support and control on highway.

3 - David Hansen designed and built 5 patented prototypes :

3.1 - In 1988, a 4x4 ATV of 350 cc was built with an additional kit of 2 wheels more at rear to fit a track. At the front, the steering wheels were wrapped with a band, the Track Tires. The vehicle was called Tracker of Tracker Industries Inc. near Portland. D. Hansen designed and built this kit. He was sales manager. D. H. says Toyomenka (Japan) killed the company in 1989.

3.2 – D. H. built prototype 1 issued of a John Deere tractor in 1991 and tested in snow sand, gullies, swamps and mud at Mount Hood. It was similar to the Tracker.

In 1995, he tested a snowmobile Polaris, with Brent Bonham, on a lake at Deer Creek. The test was to observe how a track behaves at high speed on the surface of water : it was the test of ‘spin surfing’ that’s to say high-speed track keeping the vehicle on the water surface while propelling. D.H. says : “It took off from the edge of the water and was on the surface in 10 feet.  At full throttle it was indicating 55 mph.  It was going 35 mph and if it were on packed snow it would be going 90 mph.  You cannot let up on the throttle because the first thing that happens is the track slows and that is keeping you afloat. It is 80 hp with 800 pounds”.

3.3 - Construction of Prototype 2 from a John Deere tractor, tested in 1996 at Umpqua River in Days Creek, Oregon. It was named TT955, 33 hp, hydraulic transmission, of the Terak Corporation. This articulated prototype included the patents of David Hansen : the Tbar track suspension, the track tension, the cone concept for low impact, the high-speed track assembly and tracked tire.

3.4 - Prototype 3 was built and tested by Technical Solutions Group in Charleston S.C. in 2000 for participation in the V-22 Osprey program. In July 2000 Iguana Technologies granted Technical Solutions Group a license and a third Iguana vehicle was designed and built at ¾ scale machine, around the V22 Osprey's Internally Transportable Vehicle (ITV) requirement.

3.5 - Prototype 4, built by Iguana Technology Company near the Port of Ilwaco, WA. It is a high speed, all terrain, low impact, amphibious vehicle that levers over obstacles and demonstrates a new water mobility concept, the spin surfing. As the project is closed, Iguana Technology is now at Tillamook, OR, and provides engineering services and R & D on off-road vehicles.

The Iguana vehicle is designed for marginal/all-terrain mobility : it is an articulated tracked vehicle equipped with a positive pitch control (with a jack, normally floating) to help overcome vertical obstacles until 1.22 m. Chassis is made of aluminum. Soft terrain like swamps, snow and mud are very well crossed thanks to a ground pressure of 1 PSI only. The power pack and engine 200 hp, from the Hummer, are at rear. The road speed is high, 80 km/h thanks to the flexible tracks and the suspension combining track tension, tires, idler carrying wheels, track support. The rear section is sprung by a patented pneumatic system, while the track units of the front section are linked transversally by a centrally pivoting walking beam. Steering is by articulation but also by individual brakes.

Amphibious without preparation, being propelled in water by its tracks, this vehicle is capable of spin surfing. It forwards at speeds of around 80 km/h, the shape of ‘V’ of the vehicle being configured.

David Hansen writes :


David W. Hansen was awarded a patent in 1994 for Low Impact Tracked Vehicles (5,318,141). His working career as sales engineer/manager specialized in bearings, hydraulics and power transmission. Following his graduation from Cal Poly in 1964, he worked for 8 major corporations calling on hundreds of customers in Chicago and the Western USA territory.

Hansen’s private quest since 1991, is to use his education, experience and dedication to improve mobility for all terrain ground vehicles; stay with the soldiers in the military, save lives and property in urgency response and provide low impact means for utility, construction and agriculture.  David has designed, built and tested 5 prototype vehicles to provide an empirical data base for future all terrain ground vehicle design.

The requirements for getting off road, crossing ditches and climbing steep  over snow, mud, sand and wet turf are extremely difficult and complex.  Support, engagement and power to the ground are factors that must be addressed in order to achieve reliable mobility.  Hansen has identified these factors and tested the mechanisms designed to achieve them.

Hansen calls his designs, “mechanical composites”.  They consist of new concepts in ground contact, track construction, suspension, drive train, steering, water management and configuration.  They cannot be evaluated by a CAD program which is based on historical data.

Power from the latest lightweight engines and motors are complimented by Hansen’s designs which are; lighter, simpler, stronger, repairable and less expensive.  In addition they use; momentum, Inertia and levering to achieve the stated goal of improved ground vehicle, “all terrain” mobility.


New Concepts : Ground Contact,   Suspension,   Drive,   Steering.   Frame,   Configuration

New technology : System of systems featuring, flexible mechanical composites.

Based on : high tension, superior traction, low-impact, fast all terrain tracks.


John Deere prototype

John Deere Prototype, articulated.

Tracked tires on a Jeep


Tracked tires on a Jeep


TSG Iguana

TSG Iguana

Du texte 3

QT truck with Flex-Trac


The purpose of this paper is to record and explain the discoveries made by David W. Hansen in his quest to improve on/off road, all terrain ground vehicle mobility.

  • T-bar suspension and track angle control.


  • Any deflection or twisting of the track reacts to the tension spring and the pneumatic tires.


  • The hydraulic powered angle control provides means to lever over obstacles and load or unload.


  • Using the angle control, in concert with left and right brakes, results in spin turns about the braking wheel.

  • Large drive wheel and small idler wheel maximizes track drive engagement and provides room for the suspension to flex.

Iguana 2
  • Two forces result from this type of drive.

Force 1= Drive Torque

                                 Tire radius

               Force 2= Tension X 2

  • The grouser assembly is bolted to the belt perpendicular to direction of travel. It consists of a roller tire guide, deicing pad, traction bar and molded rubber cone grouser. It has a center solid block for highway travel.

  • In soft material the cone shaped fingers support with the resistance of penetration. The rolling action causes them to flip on exit creating a thatching effect in turf, a fluffing effect on snow or sand and a cultivating effect on soil.

  • Two layers of 3/16”belting provide a working tension of 400 pounds per inch of belt width. In most cases this feature eliminates the need for road wheels. It also improves engagement over rocks, logs and rough ground.

Track with grousers

. A staggered grouser pattern places the load over the tires and improves traction in soft material. It also leaves fewer footprints.

The materials in the track assembly are conveyor belting, rubber grousers, stainless steel traction bare, roller bracket and a plastic roller. The assembly is held together with standard stainless steel bolts. It is easily repaired.

Tracked tire with grousers

. A combination seal and suspension for the drive axle utilizes a standard pneumatic tire mounted on the axle housing. Shock loads are supported 360 degrees and the stiffness is a function of the tire pressure.


Suspension of the drive axle

. A configuration with track and engine forward, rear steering and a tubular one piece chassis, provides a good amphibious design.


Scale amphibious model

. This design takes advantage of current laser fabrication techniques and provides an ideal hull for amphibious operation.

Iguana design
Iguana design 3 Iguana design

. QT truck with Flex Trac"

Semi-tracked vehicle with patented track

Hansen explains also : “The Iguana vehicle is full of new concepts that are unprecedented and unparalleled : the configuration, integrates both tracks and wheels into an amphibious chassis, driven by conventional engines, transmissions and differentials.

The tracks and tracked tires, made up of modular rubber grousers supported by stainless steel hardware, cone shaped rubber fingers for soft materials and turf. Hard tire rubber for highway.

High speed tracks with pitch control, provides propulsion in soft materials and water also provides the ability to lever over obstacles and bridge gaps.

Low impact or beneficial terra-mechanics means the vehicle leaves little evidence of passing and is many cases vegetation growth is promoted by the act of aerating, thatching and poking holes for moisture, nutrients and seed. Minimum disturbance means not getting stuck.

Iguana Technology believes that a few, multi-talented people with appropriate education and experience, working in low cost, independent facility best accomplishes Research & Development. We have found that you cannot schedule discovery, and ideas. Progress in design comes with hours of undisturbed thought and solace; close to your work with the opportunity for hands on feedback. Best to be in convenient, simple surroundings with minimal overhead, are surrounded by tools, mockups and prototypes.  Iguana Technology, as a result of extensive research, has a pool of knowledge concerning the requirements for mobility in combinations of hard and soft materials, cross country, all-terrain travel and overcoming natural as well as man-made obstacles”.

3.6 - Semi-tracked truck, 2008

Qt truck with FLEX Trac 2008

QT truck with FLex Trac, 2008. David Hansen says on 23 April 2017 : “This was my last prototype in 2008. I was partner in Biosblade Inc. and I supplied the tracks, did the design and assembly. They proposed a three way split then took the tracks and parts to New Mexico to start a business. The final agreement which I refused to sign gave me a fraction of the original proposal. We were going to enter the truck races in Parker Ariz. Not a winning combination!  
Next I got involved with the ATAV guys from Idaho who used my prototype (Utube) at the Idaho State Fair to raise $300,000. They spent it on flat screen engineering, rented a shop and hired a mechanic.  I put a clause in the contract requiring a production prototype in two years. They could write business plan and resumes but did not know how to build anything.  
I made my own toys during WW2, designed and built my own model airplanes, certified airplane mechanic, BS Industrial Eng., 6 months training in management, bearings, hydraulics and power transmission.  20 years as Sales Engineer calling on hundreds of customers and prospects. Industrial, aircraft, marine, automotive, space and nuclear.
Today's business and technology is controlled by software programmers, coders and engineers. The solutions I have achieved are not on the internet and are not free. I believe people are learning more and more about less and less”.

Semi-tracked vehicle with Flex tracks

3.7 - Semi-tracked articulated vehicle with FLEX Tracks. FLEX Tracks (patented) were invented by David Hansen who built this articulated vehicle. He says on 25 Avril 2017 : “The integrity of my track system is based on very high tension.  
The hydraulic force on the idler axle is 4000 pounds which is distributed to 1000 pounds in each track and 1000 pounds to each of the drive tires.  With that amount of tension there is no need for road wheels and the flexing of the suspension tightens rather than loosens the track (most track systems).   The allowable tension for the tracks in the picture is 8000 pounds so, it is not close to max capacity.  Any deflection reacts to the tires.  
Hydraulic cylinders on the idler axle cause the pivot point for the vehicle weight to shift from the drive tires to the idlers which are close to the center of gravity.  Spin turns are easy when the left or right brakes are actuated with the vehicle weight on the idler tires.
So, I don't have road wheels so, I don't need a frame to mount them.  The track system of the pictured truck weighs around 1000 pounds but creates a support area of over 2400 square inches.
You want to go "off road, all terrain" then you better be able to float, lever, spin, wiggle, jiggle and rock or you may not make it home for dinner.
Thank you for your question.  I had an obscure web site for 5 years and got over 10K hits but no calls or questions.  Yet, I have never seen a track system like mine.  Maybe that's why I was awarded the patent !”

On May 29, 2017 David Hansen wrote :

"By designing and building the tracks for the 4 wheel ATV's in 1986, I discovered the best way to distribute drive power to the ground is with tracks consisting of metal traction bars attached to rubber grousers connected with conveyor belting. 

I was 50 years old and had the education and experience to understand the ratios, proportions, weight, balance and endurance required for all terrain vehicles.  I also understood the complexity was far greater than water or air vehicles.

The tractor with tracks demonstrated the value of track angle control both to create a pivot point for spin turns and lever over obstacles.

The Iguana Project was funded in 1996 by the Army and administered by the Navy.  I partnered with a friend in the hydraulic business and we received $80,000 to build a prototype soonest.  It was called a "logistics demonstrator".

Five months later a group of 15 came to see it the day after we got it running.  It had to be diesel, carry 1000 pounds and float. We threw a track while drag racing a Hum Vee (we won) then sunk it in the river.  We found that the "closed cell" foam we used for flotation absorbed 20% water). The contract was for 3 years and was supposed to have maintenance and test follow on but we never heard from them again.

I made a number of modifications.  It's the yellow one in the video.

The second Iguana Vehicle was made from aluminum.  It consisted of two water tight hulls with a two way articulating joint with tracks in front and tracked tires in back. The design was arrived at with advice from a new investor.  Experience and education taught me the three steps to product improvement are Eliminate, Combine and Simplify.  Also, it’s the value of cardboard, plastic or plywood mock-ups for designing and studying new concepts. The improvements to the track proved exceptional. It’s truly a mechanical composite where the whole becomes greater than the sum of the parts.

The half-track truck project was a testament to the exceptional tracks and track angle control. It was also a weight and speed test because the truck weighed 7500 pounds and we drove it at 70 mph without any hot spots. The tracks were taken from the Iguana Aluminum Prototype.

Many changes have occurred during the years of my Iguana project.  They are putting diesel engines in aircraft and gas engines are producing diesel performance. Planetary transmissions with 6 speeds and manual or electric shift but, they are much heavier that the hydraulic counterpart.

Now, if I put my new tracks on the JD tractor, that was my first prototype, it becomes the vehicle, I believe, that the military are asking for in several solicitations. Actually it is beyond what they are asking for at a much lower cost than they are expecting.

To me, the goal is to drive a vehicle down a rough bank into the water, float, hit the accelerator and raise up out of the water using the tracks for propulsion and run across the surface using the tracks both for flotation and propulsion.

I need to find an investor who is interested in doing something worthwhile rather than just making money".

On May 31,2017, D. H. wrote :

"I have learned, if the investor is the boss, the goal is creating a marketing mechanism for profit instead of realizing a profit from solving a problem in mobility.  The tendency is trying to go too far, too fast with too little.

The Peugeot was a wonderful auto.  I bought a new 403 in 59 another 404 in 64. The aluminum head needed to be tightened every 25000 miles or the engine failed.  They piggybacked with Renault for marketing in US. Bad decision.

Saab, solved the problem by using longer head bolts with spacers to allow for the different expansion between steel and cast iron.

I have been concentrating on designing the ultimate all-terrain vehicle and have a very reliable track system. Now, if I put my track system on the tractor (my first prototype), I find it fills the need I discovered with my work for Tracker.  There are at least 5 tractors that fit the requirement and that solve a lot of marketing and service problems.

With Tracker I found that when you take people to places they have never been, the next thing they want is to take a friend or friends and then tools and supplies to do work while there, E.g. summer cabin for Xmas.  Or it’s the military who expect a soldier to carry over 100 pounds".

Pictures are from David Hansen and some comments are extracted from his former site : www.iguanatechnology.com

Videos :





Iguana conceptIguana concept (226.41 Ko), Iguana of David Hansen from Military Machine International, September 2004Iguana of David Hansen from Military Machine International, September 2004 (1.47 Mo),Iguana updated designIguana updated design (231.44 Ko)


David Hansen

David Hansen. Thank you David for your contribution.

Tracker ATV 1989

Tracker ATV, 1989

Second prototype TT955 by Terak Corporation

Second prototype, modified from John Deere, TT955 by Terak Corporation, articulated. It was designed and built from scratch with funding and support from TACOM and NRL. Construction started in April 1996. The first demonstration was conducted on the Umpqua River in Days Creek Oregon in October 1996. This prototype demonstrated the concepts of the patents including; the Tbar track suspension, the track attitude adjustment, the cone concept for low impact, the high-speed track assembly and the cone or tracked tire. Major modifications were completed in 1999 and again in 2001.

Second prototype TT955 by Terak Corporation 2

Second prototype TT955 by Terak Corporation

Prototype 3 modified John Deere, articulated

Second prototype TT955 by Terak Corporation

Tracked tires on a jeep

Track tires on a Jeep. It is like a track but around a wheel


Scale models

Scale models

 TSG Iguana

TSG Iguana built and tested by Technical Solutions Group in Charleston S.C. (2000) for participation in the V-22 Osprey, ground vehicle project and several other military solicitations.

TSG Iguana vehicle patents of David Hansen

Iguana Vehicle of David Hansen, TSG, Technical Solutions Group, 2000, built this Iguana vehicle for US Marine Corps (USMC) for an ITV, Internally Transport Vehicle to fit within the V-22 Osprey tilt rotor aircraft. Built in co-operation with David Hansen, this 3/4 scale version appeared but was nevertheless too tall and long for allowed space. It was also 500 kg overweight, being armored against anti-personnel mines. Today, there is no vehicle for V22 Osprey and David Hansen hope to adapt his patented tracks to a vehicle which would chose for this task. His prototype from John Deere would be ok for dimensions. 1724 kg empty, payload 907 kg, 65 km/h.

TSG Iguana vehicle

TSG Iguana

Tsg iguana vehicle 2
TSG Iguana vehicle

TSG Iguana

TSG Prototype

TSG Iguana

TSG Iguana

Iguana vehicle of David Hansen

Iguana vehicle of David Hansen

Iguana was built at the Iguana Technology shop in the Port of Ilwaco. It is a high speed, all terrain, low impact, amphibious vehicle that will lever over obstacles and demonstrate a new water mobility concept called spin surfing.

Uguana staying besides TSG prototype

Iguana staying besides TSG prototype. Ground clearance could be changed.

Iguana Technology at Ilwaco WA

Iguana Technology at Ilwaco, WA, on 5 February 2004.

Iguana construction

Iguana construction.

Cones on tracked tires and tracks

Cones on tracked tires and tracks, on patented grousers.

Iguana vehicle of David Hansen

Iguana vehicle of David Hansen

The road to survival and success may require a vehicle that can go where a man cannot walk, jump, climb or swim and get him there, quickly and safely. Iguana Technology believes that an all-terrain vehicle should provide transport over soft materials such as : water, mud, snow, sand and wet grass as well as obstacles such as; ditches, ledges, logs, steep hills and rocks.

Iguana vehicle of David Hansen

Following the testing and demonstration of the first production model, Iguana Technology Inc. will be discussing contracts for the special high speed, all-terrain, amphibious, low impact vehicles. They will also be open to discussing ways to integrate their intellectual property, concepts, facts and data into military, emergency, and commercial vehicles with interested manufacturers.

Iguana vehicle of David Hansen

Iguana is to provide a reliable means of surface transportation:

  • From floating vessel to highway

  • For roaming shorelines, estuaries and deltas

  • Over roads and highways with deep snow

  • Over mud, sand, swamp and wet turf

Iguana vehicle of David Hansen

Iguana vehicle of David Hansen

  • It can be seen the support of the ram for pitch control.

  • Prospective Customers :

  • Military, Manned and Unmanned Vehicles: Command & Control, Reconnaissance, Utility, Assault

  • Government Agencies: Coast Guard, Forest Service, Corps of Engineers, Fish and Wildlife, Homeland Security, Border Patrol, Beach Patrol

  • Law Enforcement: Emergency Response, Fire Departments, Search & Rescue

  • Utility Companies: Survey, Construction, Service & Maintenance

  • Agriculture: Seeding, Spraying

  • Ranching: Transport, Feeding, Maintenance

  • Mining: Exploration, Survey, Transport

  • Wood Products: Cruising, Harvesting, Transport

  • Vacation Resorts: Hunting & Fishing Guides, Transport, Maintenance,

  • Recreation

Iguana in water tests

Iguana in water 3

Iguana  spin surfing

Iguana spin surfing

All terrain vision

Iguana articulated and amphibious, very off-road

Articulated semi-track vehicle patent of David Hansen

Drawings of patents

Concept proposed for Darpa

Novel concept proposed for Darpa for Ground/Marine Systems

Iguana of David Hansen 2005

Iguana in 2005, drawing

Iguana design

Iguana design

USP5318141 low impact tracked vehicle patent

USP5318141 Low Impact tracked vehicle patent of David Hansen. There have been ongoing discoveries critical to the Iguana success as well as trade secrets reported to the patent file which comprise the Intellectual Property.

USP5547268 grousers patent

USP5547268 grousers patent of David Hansen

Iguana concept

Iguana concept

Iguana updated design

Iguana updated design

Amphibious Iguana

Amphibious Iguana

Iguana becomes ATAV

Iguana, later ATAV (Advanced Technology All-Terrain Amphibious Vehicle) must be produced in Indiana mid-2011.