Here is a synchronous belt from my 1999 Camry. It ran the camshaft and the water pump. That was until the pump bearings failed, causing the pump sprocket to fatigue and release a piece of the sprocket, which destroyed one of the teeth on the belt, which caused the belt to jump the cam sprocket, making the engine lose timing, stranding the driver. What you see here is $600 later.
As you can see the belt was very durable. Some evidence of fraying can be seen on the side of the belt where the sprocket shed a piece of itself, but the belt did not break. These types of belts are a real leap in power transmission, as they have taken over many applications were chains and gears previously ruled.
That being said, I have come to believe that these types of belts have, at best, a niche of a niche in the world of experimental aviation. Let me explain. I was fascinated by these belts and even started an unsuccessful business trying to develop and sell reduction drives for experimental aircraft based on these belts and automotive-sourced gears.Do they work? Yes. Can they be the basis of a successful business? No. I forgot one of the cardinal rules of everything - KISS - Keep It Simple, Stupid.
A reduction drive (re-drive) adds weight, complexity, and reduces reliability. Three things you don't want in an aircraft or aircraft engine.
Take a look at the most successful alternative aircraft engines out there - VW and Corvair. Sure there are lots of others out there, but you can count their installed base on the fingers of one or two hands, while VW and Corvair based conversions number in the thousands.
There is a reason for that. It took me a long time to learn even though it isn't rocket science. VW and Corvair engines look a lot like most piston aircraft engines. They are air cooled and horizontally opposed, just like Lycomings and Continentals. They were made by the millions and there is a healthy supply of aftermarket parts, like pistons, cylinders, cams, etc. And, they are direct drive.
Thus, the VW and Corvair conversions hit the sweet spot of price, availability, simplicity and reliability. Also, they are ideally sized for Light Sport aircraft. I think they will continue to be successful in their market. (Which will never be more than thousands, but that's a topic for another blog.)
Oh, by the way, I have seen the magazine articles about the guy with an RV-6 and a Chevy V-6 and the one about the Corvette LS1 in some slick composite airframe, both with re-drives, belted or geared. But how many installations are there? Most are one-off installations. And I guarantee that the owner would have spent less time and money and spent more time in the air with a more reliable engine, if he would have just installed a big bore Lycoming or Continental, instead of engineering a complete installation from a $7,000 Corvette crate engine even if the Lyc or Cont cost $60,000! Some people just like to be different.
