Just because you can hear the valve closing doesn’t mean anything. you can’t let valves snap closed uncontrolled because they will stretch, which is what leads to breakage. Plus it will accelerate wear of the valve/seat interface. if they close in a controlled manner by following a cam lobe down (whether closed via spring or via rocker arm) there’s no room for them to stretch.
Check out the list of stuff I laid out in post #26; there are many things changing what they are doing when you try to run an engine in the other direction.
It certainly looks like it closes rapidly - except for the last little bit, the closing ramp. It’s like a C-130 performing a tactical approach: it may drop like a mofo during final approach, but just like any other plane, it still has to flare at the last second for a gentle touchdown, lest bad things happen.
About ten years ago I worked on a prototype hydraulically actuated valvetrain, and moderating the closing impact forces was an important consideration. It’s been a while, but ISTR a setup wherein during the last few mm of travel, the end of the valve stem entered a sleeve with tight clearances, such that hydraulic fluid being driven through those clearances at high velocities by the advancing valve stem generated braking forces that slowed the valve to an acceptable touchdown speed before the valve head actually contacted the seat.
Only crank assembly thing i noted in it is offset wrist pins on some engines.
You would of course not use them and use a centered assembly.
I do know that it is entirely impossible for a wankel to run backwards.
I simply thought discharging grass on both sides might be more efficient than forcing it all out 1 side.
And to the rest of the posters, thanks all, I learned quite a bit.
That’s a very common way to snub hydraulic actuators. Not surprising it was used on your prototype.
What’s the problem? Looking at this Wankel animation, it certainly appears that it would pump air backwards through the engine just like a conventional four-stroke piston engine; ISTM you’d just need to introduce fuel in the right place and tweak the spark timing, but those are the same issues you’d have with a piston engine. What am I missing?
Firing the grass to one side is handy if you’re bagging it, and it’s also handy for mowing next to landscaping or parked cars, so that you can blow the clippings away from the bushes/flowers/cars instead of all over them. It would be easy to design a single-engine/blade mower with chutes going to both sides, but for those reasons I don’t think it would be a big seller.