That is the problem with gears is everything has to be perfect, with chain and sprockets you have some wiggle room, if you were running for a few years on gears, you had to have had a high level of precision going, I wouldn't even want to try it, I'm not that good
An oil bath roller chain drive is just about maintenance free. On a close shaft spacing you don't need any sort of tensioner either.
Oil bath chain drives drove Detroit V-8 camshafts for years and years before some idiot came up with the idea of using a rubber band to drive overhead cams. And those chain cam drives operated for years and thousands and thousands of miles at very high speed with very few failures. And those weren't even roller chains for the most part - mostly link belt chains with a plastic driven sprocket on the camshaft so they'd run quiet. The plastic cam sprocket shedding its teeth was the main point of failure in those cam drives. The first thing you did when building a high performance engine was throw the stock timing chain and sprocket set away and bolt in a dual-row roller chain timing set.
With the roller chain drive there's no need to change oil in it unless it gets water in the gearcase somehow - and even then it probably wouldn't hurt it much because the water will just settle out in the sump and not cause a problem anyway. I'm expecting between 20,000-30,000 hours out of a chain and when the backlash gets excessive you pop the cover off the gearcase, roll a new one around the sprockets, fill it up with oil and stick it back up in the air. As long as you don't run it after it develops excessive backlash so the chain starts climbing the sprocket teeth, the sprockets will last indefinitely in oil bath. Putting the high speed pinion in the oil causes it to pick up oil like a pump and fling it around inside the gearcase to prevent rust on the insides of the gearcase. As long as you got the oil level right - so just the bottom of the chain is covered as it goes around the pinion - it also sucks a "hole" in the oil level so there's no viscous drag. All you have to do is keep the chain wet.
My concerns about the roller chain drive being hard to turn in extremely cold weather was completely unfounded too. Even at 30 below last winter that turbine started up at 3-4 mph and was putting out power at 6. The first one had ATF mixed with diesel fuel, the second one had 80W-90 gear oil in it - didn't make one bit of difference. I finally put 80W-90 in both of them because it sticks to the chain better.
--
Chris