Robert Q. Riley Enterprises: Product Design & Development

Build it yourself from plans

XR3 Video


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XR3 by park

super-mileage XR3 in driveway

125 mpg XR3 by park

Build Shots

Front view of XR3 foam core

Simple XR3 chassis

XR3 body almost finished


XR3 frequently asked questions



Contents of

Plans on disc, complete with Solidworks CAD files.

Standard XR3 Plans in printed format with photo illustrated bound manual

Deluxe Plan-set done in CAD and Complete  with Solidworks CAD files and 3D models

Parts and
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  Robert Q. Riley Enterprises developed the XR3 Hybrid

XR3 Plug-In Hybrid

A Three-Wheeled 125-MPG - 225-MPGe Hybrid
Vehicle Designed & Modeled in CAD
You can build it from plans...

Featured in Discovery Channel's
NextWorld episode, Future Radical Vehicles

Plans and Instructions
Click for Details: Deluxe plans, $200 - Standard Plans, $170 - Plans on Disc, $99.50

     The XR3 Personal Transit Vehicle (PTV) is a super-fuel-efficient two-passenger plug-in hybrid that achieves 125 mpg on diesel power alone, 225 mpg equivalent when diesel and electric power are used in series, and performance like a conventional automobile. The design of the XR3 Hybrid is based on existing technologies and a vehicle personality that makes conserving energy a fun driving experience. It showcases the design ideas explored in Robert Q. Riley's book, Alternative Cars in the 21st Century.
         XR3 on "Looper" set in New OrleansAt just 1480 pounds, this high-performance design combines fast acceleration, a maximum speed of 80 mph, and fuel economy of 125- to over 200-mpg.   You can set it up as a diesel-powered vehicle and get up to 125 mpg.  As a hybrid, fuel economy can excede 200 mpg.  And as a pure battery-electric vehicle, it can run 40 to 100 miles on a single charge, depending on the number of batteries.
          Its clam-shell canopy and three-wheel platform boldly differentiates the XR3 from conventional passenger cars. The vehicle's hybrid power system, diesel engine, and low curb weight are the main ingredients of its super-high fuel economy and excellent performance. Acceleration equal to that of a conventional car and a maximum speed of 80 mph make the XR3 Hybrid equally at home on freeways and surface streets.
         XR3 cruising neighborhood on battery powerPlans enable people with common building skills to build a duplicate of the XR3 Hybrid prototype. Or using the technical information in the construction manual, readers will understand the factors that influence fuel economy, and learn how to make any car achieve greater fuel economy. The XR3 Hybrid gives enthusiasts and experimenters the opportunity to significantly reduce their transportation expenses and have fun doing it.

Plug-In Hybrid Architecture

Get Started When set up as a hybrid, the XR3 is a plug-in hybrid.  This makes it possible to drive on battery power alone on trips of about 40 miles (100 miles when built as a pure battery-electric vehicle with additional batteries installed in place of the engine and transmisison). And when both the diesel and the battery-electric systems are used in series, fuel economy increases to over 200-mpg(e).
        A plug-in hybrid simply means that part or all of the vehicle's energy is taken from the grid system where it is cleaner and less costly to produce. Most of the world's automakers are now working on plug-in hybrids.

Virtually Unlimited Options

       The plug-in architecture also allows much greater flexibility in power system choices. With a mild hybrid, like the Honda Insight and the Toyota Prius, proper control of the power system depends on having known operating characteristics of the subsystems - the internal combustion engine (ICE) and electric systems. Subsystems are selected in advance and controlled by a computer. The computer, however, can properly manage integration of subsystems only when the output characteristics of the two systems are predefined and fixed. Any modification in either of the power systems (electric or ICE) can cause the control system to operate incorrectly.
        With the XR3's unique system, the two front wheels are powered by the combustion engine, and the single rear wheel is electric powered. These two power systems are not connected within the vehicle and they are not integrated by a computer. The connection between the conventional and electric power systems is provided by the ground.  Proper phase-in between the two power systems is handled by a simple throttle mechanism and dash-mounted switches that let the driver select between driving under ICE power, electric power, or dual (hybrid) power modes.
         In the hybrid operating mode, the XR3 has lots of burst power for quick acceleration. If you were to use this acceleration potential to its fullest, fuel economy will be reduced. Fuel economy will also vary according the particular components chosen for the power system. Performance figures quoted here are for a conservatively-driven vehicle having a system configured just like the prototype. Plans provide the information necessary for selecting different components in order to modify the vehicle's performance characteristics.  Builders, however, are free to install a different engine or electric motor without affect the way the two systems work togther, or they can just install one system or the other system.

Build Time and Costs

      Figure about 500 - 650 hours of build time, depending on your skill level and which version you build (diesel-only, battery-electric, or hybrid).  Much of the time is in building the body.  The simple chassis goes quickly.    Construction costs are also variable because of the many choices individual builders might make. It's a modular design that lets builders make choices according to their budget and performance goals. More than half the cost of parts for the XR3 prototype went to the electric propulsion system.  This is typical of electric vehicles.
      At the upper end, a duplicate of our Li-Ion-powered prototype will top $25,000. If you switch to lead-acid batteries, you can save as much as $5,000, but you'll have to forego the performance of advanced batteries. At the bottom end of the scale, a diesel-only vehicle capable of achieving 125-mpg can be built for less than $10,000. The modularity of the design allows you to begin with a diesel-only vehicle then add the electric power train components later on. 
      Similar options exist with a battery-only vehicle. One can simply leave off the combustion power system, install more batteries in the extra space up front, and end up with a BEV capable of driving 100 miles on a charge. Li-ion batteries can be recharged in about two-hours (or less, depending on the charger and line capacity).   A full recharge of lead-acid batteries normally takes 6 to 8 hours.  With enough line-capacity, however, a Li-Ion battery pack can be brought to about 80 percent charge in less than one hour.  But these rapid charge levels degrade the life of the battery pack.
      These cost-related choices also affect the performance of the vehicle. For example, leaving off the electric propulsion system reduces vehicle weight from about 1500 pounds (682 kg) to approximately 950 pounds (432 kg). This improves diesel-only fuel economy and acceleration. 


         Plans come in three versions, all done in CAD: Deluxe - $200, Standard - $170, and Plans-On-Disc - $99.50.  The order form automatically calculates the shipping charge based on weight and destination.  Click on the images to the left to get details on the contents.  The Standard Plan-Set consists of conventional printed plans and a 149-page bound manual.   The Deluxe Plan-Set includes everything in the Standard Plan-Set, plus three discs.  The discs contain a one-hour video of the XR3 being built and lots of helpful electronic files.  Files include 3D CAD models that can be viewed on your computer, plus conventional drawings. The manual is also on disc, and runs in a web browser with click to enlarge color images, plus links to vendors, logo files, DXF files for water jet cutting, IGES files for CNC machining, and all the original SolidWorks files in their native format.  The Plans-On-Disc set includes the three discs included with the Deluxe Plans-Set, but without printed plans and bound manual.  It is, however, a complete stand-alone set of plans.  You can zoom into a particular part and print the drawing with your standard printer.  If you prefer large prints and a bound printed manual, it's best to get the Deluxe Plans-Set. 
      Benefits of the Electronic Files 
      When you receive either of the plan-sets containing the electronic files on disc, be prepared to experience an advanced building aid unlike anything you've ever experienced.  For more information about the technology, please click on the Advance CAD Technologies for the Home Craftsman.  This is a new DIY technology developed at Robert Q. Riley Enterprises.



                   Phone:  480-685-3225

Other Resources and Information

Essential Resouces for the Do-It-Yourselfer
Additional high-resolution XR3 images
Yahoo XR3 Group  A discussion group of XR3 Builders.
An overview of moldless composite construction An explanation of how the XR3 body is built.
Advanced CAD Technologies for the Home Craftsman

XR3 in the News
Forbes on the XR3

Autoblog Green


PowerPoint presentation by Robert Q. Riley, September 18, 2008, to the Arizona-Nevada Section of the Society of Automotive Engineers (SAE) at the Hilton Phoenix Airport Hotel. For best results, save file, then open in PowerPoint.

A PowerPoint presentation by Robert Q. Riley, October 11, 2007, for the Center for Advanced Vehicular Systems staff at Mississippi State University. Click on the link above to be able to OPEN or SAVE the presentation.


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Robert Q. Riley Enterprises: Product Design & Development
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