Originally Posted by fishguts
It makes little mechanical sense to me that a slam valve would work very well (although I've seen videos showing it does) in that it opens the steam well before TDC, an equal amount on either side of TDC actually. My only guess is that the inertia of a turning engine beats the incoming steam enough to allow it to overcome the pressure. In the world of real steam engines, you want that steam coming in no more than about 5 degrees BTDC and hanging in there for maybe 3/4 of the power stroke. But I'll give this another go before I rig up an external valve system. The trick is to just keep messing with it until it works.
You have quadrupled my understanding of steam in a day (maybe not saying much but thanks anyway) Makes a ton of sense that the valve is opening before TDC. Is it building up enough pressure to stop the piston cold, you think? would explain that metalic clunking noise you described, pistons slamming into an imovable smash valve? Seems like the Dudes online are running larger flywheels at MUCH lower PSI. I wonder if hooking up the jackshaft and getting some momentum on that upstroke would do the trick or dropping the PSI and ramping up slower perhaps?
Really looking forward to that beautiful thing running....