Only eighteen of these prototypes were ever made by Harley-Davidson back in 1941 for World War 2, and only 7 of these trikes were known to survive into the modern era. Specifically made for military use, these bikes were intended for off-roading and it is effectively a trike.
The development of the TA Knucklehead was spurred by the three-wheeled war machines in Europe, which included the likes of the BMW R75—sidecar and all. So the Americans wanted to field a three-wheeler of their own, and this is what came out of that desire. Though, unlike the BMW, this particular model never made it into production.
It just wasn’t green-lit by the United States at the time. Nobody knows the full story of why it never did. Sure, you can say that it was unreliable, but all of its oil leak and excessive vibration issues were largely addressed by H-D.
Interestingly enough, another trike was greenlit in its wake: The Harley-Davidson WLA. Instead of the Willys Jeep getting all the credit for being the only light vehicle in the American army, the WLA served as the spiritual successor of the TA Knucklehead.
It’s questionable as to why the TA never made it into production if you look at its specifications. The 68 cubic-inch V-twin was able to produce 40 horsepower, but the WLA ended up with a smaller-displacement 45-cubic-inch V-twin, which was the same as the Servi-Car. With the bigger engine also came bigger wheels. It essentially had the same wheels and tires as the Willys Jeep, which would mean that it could have been an easy swap for military personnel just in case.
So if the prospect of an ultra-rare military prototype entices you, then I recommend that you register to bid in the Mecum Auctions for Las Vegas 2022. The auction will take place from January 25 to 29, 2022. You have a bit of time to decide whether this lot number will be worth it, but remember Lot R400, and remember to bring your checkbook.