Isothermal Heat Transfer

[Tom Booth]

The displacer phase angle is not subject to my opinion.

OK, if you say so.

IMO the timing only "seems" different because of the opposed piston configuration makes it appear different.

[Fool]

I think I agree with Tom on this. The crank pins are offset by 90 degrees. The push rod doesn't even reverse the direction. It's called a two force member, kinda, sorta. If anything it just reverses the viewpoint of what direction the engine will turn. The gas sees the same hot cold volume phases. The hot and cold positions are reversed relative to the crankshaft. So it will run the "opposite" direction.

[VincentG]

You guys are right. I must be drinking too much lately.

When operating the Essex by hand, the extreme rod to stroke ratio of the displacer causes a very sudden movement of the displacer relative to the power piston that I was mistaking for a difference in phasing. That combined with the rod kinda sorta working backwards had my viewpoint all screwy.

What it really is, is a genius way to bring the displacer movement more in phase without complicating the linkages.

Sorry to hijack your thread Fool.

[matt brown]

I think I agree with Tom on this. The crank pins are offset by 90 degrees. The push rod doesn't even reverse the direction. It's called a two force member, kinda, sorta. If anything it just reverses the viewpoint of what direction the engine will turn. The gas sees the same hot cold volume phases. The hot and cold positions are reversed relative to the crankshaft. So it will run the "opposite" direction.

My graphics were to show this double reversal, but I wasn't sure of rotation direction due to ideal distinct phasing (via double dwell) vs real out-of-phase motion which might have Essex running opposite common gamma (I'm still unsure).

[matt brown]

You guys are right. I must be drinking too much lately.

What I think when I hit Starbucks more than once a day.

What it really is, is a genius way to bring the displacer movement more in phase without complicating the linkages.

What I thought while watching your video (you should leave it up, maybe change narrative). With DP stroke greater than PP stroke, Essex adds PP dwell at TDC. Quite a contrast vs Koichi monster with PP stroke 2.5x longer than DP stroke.

Per my graphics, hot and cold gamma have equal pressure values, so hot gamma can also have an ambient compression stroke which might change the game.

[VincentG]

Yup ill reshoot video with more accurate explanation of kinematics. Double reversal is a good description here. It still hurts my pea brain thinking about whats going on exactly.

Btw the original Essex has 1.5" displacer stroke compared to 2" for the myfordboy version.

Between that and the aluminum cold end, his Essex clone probably runs fantastic.