I'm trying to learn more about inline 3 engine balance and engine balance in general (motorcycles)... I3 interests me for a few reasons but i want to further understand how they work.
L4 and crossplane I4 engines have evenly spaced 90 degree cranks i believe, so when one piston is stopped another is at max speed, meaning the crankshaft speed (and thus the engine) is smoother... That's what i understand anyway.
I'v heard that this same smoothness applies to 120 degree crank I3 engines but i'm a bit confused. I get that the cranks are evenly spaced like the examples above, but the piston movement (and thus speed) doesn't look so simple to me, even after watching it move online. Do the pistons speeds really cancel each other out perfectly like the 4 cylinder examples above (creating even crankshaft speed), or does it do worse compared to them?
Also i believe (could be wrong) these I3 engines can use a single balance shaft to deal with the rocking motion caused by the outer 2 cylinders... In this scenario (using the balance shaft), are there any other imbalances remaining?
I find I3 and L4 engines to be really cool. They're even firing/high revving screamers (my favorite kind), narrow, have great inherent balance/power delivery etc. L4 seems great for litrebikes and would love to see some lightweight I3 screamers (maybe 300CCish) as well since i also find small sport bikes to be really cool. Sorry if i'm rambling a bit haha.