EAAers in action
what our members are building & restoring
One-of-a-Kind Design
Building a tricycle gear Hiperbipe
JEREMY MACDONALD, EAA 748627; SANTA CRUZ, CALIFORNIA
jeremym@spxdata.com
One day an unusual-looking biplane, a Hiperbipe, ground looped at my airport. It careened off the runway and made a long furrow in the waterlogged grass. In the last half-second, just as the aircraft
stopped, the left undercarriage leg socket broke out of its
place in the engine mount and the aircraft slowly tipped
onto its nose. Amazingly, there was no other damage
and no impact to the wingtips. One prop blade had been
slightly bent, but the engine
and airframe were completely
undamaged.
I examined the Hiperbipe
a few days later. By this time
it was back in its hangar, with
the legless side sitting on tires
and the broken-off leg lying on
the floor next to it. I jacked the
airplane until it was level and
climbed inside. I moved the controls about and looked at
the view out the side window. The instrument panel was
beautiful and made of wood—it reminded me of a classic
cabin cruiser. Right then I decided to buy the aircraft and
restore it to flying condition, but only under one condition—that it would end up as a tricycle gear aircraft!
Within a few days I had the engine mount repaired
and the gear legs back to where they belonged. I sent the
prop in for an overhaul and removed the engine mount
and started to figure out how I was going to get a nose
gear socket mounted. I removed the wheel from one of
the Hiperbipe’s original legs and leaned the leg against the
engine mount on the firewall, with the axle portion pointing straight down. Amazingly, it was perfect for the nose
gear leg, so I fabricated a three-part socket for it out of 4130
steel and had it TIG welded together. Then, I proceeded to
cut 4130 tubing to support the socket. It took 10 separate
tubes TIG welded into the mount before I had a strong leg
socket. A Van’s nose wheel fork and wheel fit on the new
leg with no modifications!
Right then I decided to buy the aircraft
and restore it to flying condition, but
only under one condition–that it would
end up as a tricycle gear aircraft!
I decided on an aluminum spring gear. I chose the one
that is used on the Zenith CH 801 aircraft and began to
figure out how to mount it on the Hiperbipe. Obviously,
I couldn’t just sit the aircraft on it because that would
bend that square-section 4130 steel longeron tubing that
runs fore and aft below the aircraft doors, which is where
the main gear needed to be mounted. I had to spread the
weight and any rearward twisting to the nearest pair of
hard points. The front one is where the lower wing’s main
spar joins the fuselage—this is a really strong point—the
second strongest on the entire airframe, in fact, and much
stronger even than where the engine mount bolts onto the
