1941 Harley-Davidson TA Shaft-Drive Knucklehead Military Trike
In 1941, Harley-Davidson built an experimental military three-wheeler based on the Servi-Car idea. The model was called the TA, and unlike the standard Servi-Car, which used a 45ci flathead motor, the TA was outfitted with a more powerful 68ci Knucklehead motor.
A Military Servi-Car with Knucklehead Power
The TA’s 68ci motor was mated to a heavy-duty 3-speed transmission with reverse. Instead of using a chain to power the rear wheels, the TA used a driveshaft connected to an automotive Dana 44 rear end. That made the machine an unusual mix of Harley motorcycle parts, Servi-Car utility thinking, and military-vehicle hardware.
It also featured solid disc wheels, an XA-style springer front end, and was built in both right-hand and left-hand shift versions. Those details are part of what makes the TA such an oddball Harley-Davidson today. It looks familiar at first glance, but the drivetrain and rear axle layout are well outside the normal Servi-Car pattern.
Testing Problems and Limited Production
The first TAs were reportedly plagued with a number of problems, including poor handling, extreme vibration, and multiple oil leaks. Harley’s engineers addressed those early problems well enough for a small Army production order, but the project never went into large-scale production.
Accounts generally put total TA production at 18 machines. Of those, two were prototypes and the other 16 were production models. The supplied research material describes the prototype development as moving from an early chain-drive version to the later shaft-drive layout, which is the configuration most closely associated with the TA today.
The timing worked against it. By 1941–42, the Jeep was proving to be a more versatile light military vehicle, and the TA remained a short-run experiment rather than a standard Army motorcycle. It fits into the same wartime development period as the Harley-Davidson XA and other unusual factory experiments, including the prototype Servi-Car with an XA powerplant.
Wheels Through Time and the Surviving TA Story
The Wheels Through Time Museum in Maggie Valley, North Carolina, has displayed one of these rare trikes in its military collection. You will want to schedule an entire day to really go through the museum, but it is well worth the trip.
That is probably the best way to appreciate a machine like the TA. On paper, it is a list of odd parts: Knucklehead power, shaft drive, a Dana 44 rear end, solid disc wheels, reverse gear, and a military three-wheel chassis. In person, it becomes something much more interesting: a rare look at Harley-Davidson trying to solve a wartime transportation problem during the same period when the Jeep was becoming the Army’s more practical light-transport answer.