What do aircraft have in common with bicycles and motorcycles?
From chains and sprockets to direct drives
By Kiron Kasbekar | 17 Mar 2025
If someone asked you what aircraft have in common with bicycles and motorcycles, how would you respond?
“Pshaw! What kind of stupid question is that?” you’d exclaim. “Aircraft use propellers or jet engines to power themselves to fly. You don’t have pilots pedaling wheels up there in the air as cyclists do! Motorbikes are another matter.”
What then?
“They all have wheels?”
No. Not true. Amphibian aircraft manage without wheels; they take off from and land in water. Their bodies are shaped like boats or they have pontoons instead of wheels, which help them land on water, float in the water, ‘taxi’ (move at low speeds) in the water, and take off from the water – all without wheels.
“Okay, enough! So what is it?”
Well, early aircraft, such as the Wright Brothers’ planes, used chain-and-sprocket mechanisms. And they were not the only ones. Early aircraft that were produced in the earliest days of powered flight during the early 20th centuries used these mechanisms that were used in bicycles and motorcycles.
The Wright brothers’ 1903 Flyer, the first successful powered aircraft, used a system of chains and sprockets to transmit power from the engine to the propellers. That was not surprising considering that the Wright brothers were bicycle mechanics, and had worked with bicycles chains. So they used bicycle chains to connect the engine of their first plane to the two counter-rotating propellers.
But chain-and-sprocket mechanisms soon fell out of favor in aircraft design. There were several reasons for this.
As aircraft design advanced, every gram of weight became critical; and chain systems were relatively heavy compared to the alternatives.
What was worse, there were reliability issues; chains could stretch, break, or jump sprockets, creating dangerous situations in flight. Chain systems were also not efficient in transmission of power; given their inherent friction losses they did not represent the most efficient way to transfer power.
Then as engine technology improved, direct-drive systems became more practical, eliminating the need for intermediate power transmission. For applications where the engine couldn’t be directly connected to the propeller, shaft drives with gearing proved more reliable and efficient than chains.
By the 1910s and 1920s, most aircraft designs had moved to either direct-drive systems (where the propeller was attached directly to the engine crankshaft) or shaft-drive systems with reduction gearing for larger aircraft with more powerful engines.
