The ElliptiGO Glide Bike
By Brent Teal
■ When my friend Bryan Pate asked if I could
build him an elliptical trainer he could ride outdoors
like a bike, as a substitute for running, I was surprised
he couldn’t buy it. Once I was convinced that it didn’t
exist commercially, I set about designing one. After
extensive 3D modeling, finite element analysis, and
many design iterations, the ElliptiGO was born.
I designed the frame to create a smooth, elegant,
sweeping line that connects the bike’s functional
points without interfering with the rider. I chose fillet-brazed 4130 chromoly steel tubing for the frame
because it’s strong, doesn’t require post-weld heat
treatments, and has an easier learning curve compared to welding. To minimize the frame’s weight
I chose small-diameter, thin-walled tubing and got
sufficient stiffness with a sweeping truss design.
One of the toughest parts was creating the two
large radiuses out of plane bends in each of the four
main structural tubes. The technique that finally
worked involved packing sand in the tubes to prevent crimping and using a plywood fixture to get the
target bend radius and angle while maintaining the
proper phase angle between the two bend planes.
We are very pleased with the performance of this
prototype. Bryan has put more than 1,000 miles on
it, including a 50-mile ride where he averaged over
15mph, finishing in 3 hours and 16 minutes.
Now, we’re moving to production with a professionally built prototype. We’re currently taking deposits
and expect to deliver bikes by the end of the year.
Having an adequate stride length was one of the
critical aspects of achieving a fun, high-performance,
non-impact running experience outside. To facilitate
a long stride while minimizing overall bike length,
I used an offset slider crank mechanism, with the
crank pivot located behind the rear wheel, for the
rider-to-drivetrain interface. I leveraged off-the-shelf
bicycle parts when possible, including the 8-speed
internally geared hub, which provides a great riding
experience whether climbing or flying downhill.
I built the ElliptiGO in my garage in about six
months. I fabricated everything on the bike myself,
including bending the tubes, brazing the frame,
and machining all the other custom components.
ElliptiGO video and news at elliptigo.com
Brent Teal is a mechanical engineer and ultra-marathoner who lives near San Diego, Calif.
Photography by Bryan Pate (main) and Marty Sconduto (inset)
176 Make: Volume 19