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Tim Cumpert is a prototype model maker by day, but outside of work hours, he creates custom bikes and furniture in his workshop, aptly named Cumpert Contraptions. His remarkable imagination is well-suited to the unique and imaginative projects he takes on.
Tim Cumpert’s idea for BMW Boxer Tricycles was transformed into a reality. His inspiration stemmed from his admiration for pre-war racing cars, and he was eager to challenge himself in the realm of aluminum sheet fabrication.
The tricycle itself is built upon a 1993 BMW R100R Mystic skeleton, combined with the front end of an ATV. Aligning the two frames required considerable skill as the ATV’s front end was square, while the BMW frame was round, but Cumpert was undeterred. He began by attaching a pair of Austin 7 wheels to the front, then measured the wheelbase by supporting both ends of the frames.
After some ingenious TIG welding, the rest of the tricycle was sawed into shape. While most of the ATV’s front end remains intact, including the steering linkage, swingarm, and suspension, Tim intends to upgrade these components.
The ATV’s disc brakes have been retained and are prominently featured in the tricycle’s design, while the BMW’s original drum brakes and wheels are still used in the rear. The rear shock has been upgraded to a Hagon part that was installed on the sponsor’s bike. One particularly discreet modification is the new position of the boxer engine’s mounting, which has been skillfully integrated into the tricycle’s design.
Tim’s intention was to propel the BMW Boxer tricycle’s design forward, which led him to construct new mounting points for OEMs using bolts to attach them. Additionally, he built an additional link to transmit power to the stock drive shaft. The BMW’s refined bodywork is on full display, showcasing its striking design.
Sketching up for tricycle
Prior to building the tricycle, Tim invested considerable effort into conceptualizing his design. He created several sketches outlining his vision for the tricycle, and once the chassis was completed, he used CAD software to further refine his concept. The use of digital rendering provided several benefits, enabling Tim to refine his design in ways that would not have been possible through sketches alone.
The use of CAD software offered several benefits to Tim throughout the design process. Firstly, it allowed him to machine a 1/3 scale model of his design using CNC technology. Additionally, it helped him to create wooden carts to hammer the boards onto. As this was Tim’s first sheet metal project, he intentionally designed the shape of the BMW Boxer Tricycle to feature mostly simple forms.
The majority of the BMW Boxer Tricycle’s body is constructed using rollers, with the front grill and side covers mounted on MDF boards. Tim utilized an English wheel to smooth out the body’s surface. The most complex section of the body is the rear, which is composed of approximately six distinct parts.
Although Tim acknowledges that the tricycle was built primarily for its aesthetic value, he opted to attach each panel to the inner frame using a multitude of dome head screws. While this design choice certainly contributes to the tricycle’s unique appearance, it also means that even the most basic services can take a considerable amount of time.
Challenges
The bodywork of the tricycle is truly breathtaking, and features elements reminiscent of Star Wars vehicle design. Tim has incorporated a number of elegant details, such as CNC-machined side skirts that nod to the iconic BMW 507.
The tricycle’s unmissable front grille is made from a newly replaced Kawasaki Versys windshield, mounted on custom positions. At the rear, the seat cushions and upholstery are from a Triumph Bobber, mounted on a handcrafted pan.
The tricycle’s middle section features countless compact lines that illustrate the exceptional level of care and attention to detail that Tim put into its creation. The BMW Boxer Tricycle retains many of Tim’s original parts, including the switches and tachometer, which contribute to its vintage vibe.
The tachometer has been creatively reassembled into a bulge panel on top of the tank, with the original BMW key located just below it. For those wondering where the fuel cap is, it can be found between the handlebars and the display.
Among other modifications, Tim installed a Daytona speedometer, a Honda brake lever, and a full rev with a Motogadget control box. Additionally, he recently fitted a Yamaha BT1100 silencer, as he took the bike to a noise-limited event.
Tim may describe this project as a “shed build,” but his work is impressive, given that he completed the entire project single-handedly while saving money. He is also realistic about the BMW Boxer Tricycle’s abilities.
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