[desdiv]

The pistons rotate. Not just the pistons, but the cylinders and the connecting rods as well. It's basically the entire engine block rotating against a stationary cylinder head.

The large rotating mass problem is basically what killed off the pre-WWII-style rotary engines, and the Duke engine suffer from the exact same problem.

[JoeAltmaier]

So why not connect the disk to the shaft, and have it rotate instead? Not a mechanical engineer, but that would have way less mass, way less clever mechanical linkages for valving, spark.

[bradleyland]

The disc contains systems that are not easily reciprocated: the intake and exhaust ports, as well as the ignition system. You can be sure that if it were possible to simply swap the rotation, Duke would have done it. The issue of reciprocating mass is well known by engineers who work with axial engines.

[JoeAltmaier]

I guess I still don't understand. Lots of engines don't put the valves and ignition on a disk - so don't. The idea of valve-less cylinders via rotating ports can be done either way - rotating cylinders or rotating shaft - so reverse them.

I know, that's not a Duke engine. Just wondering who got it wrong the first day and went down this path. Like the old 'drum memory' systems that rotated the heads and left the magnetic memory stationary. Didn't take but 2 years to turn that around and invent disk drives.

[bradleyland]

So, you believe that sitting in your armchair, you've identified some fundamental flaw in the Duke engine design that they overlooked from day 1?

Yes, ported intake/exhaust solves the problem of rotating the disk instead of the cylinders, but porting comes with its own set of drawbacks. Ask any engineer who has worked on Wankel Rotary engine design and they'll tell you all about it. Ported engine designs include the Wankel Rotary design, as well as 2-stroke, reciprocating, piston-in-sleve (traditional 2-stroke ICE) engine designs. Both have issues meeting emissions requirements because of inherent limitations of ported engine designs.

Cam operated valves have some very specific advantages that play a large role in the ICE's ability to reach current specific output levels. With a ported engine, you cannot vary the intake/exhaust profiles; with a cam, you can. Variable overlap in intake/exhaust, as well as variable intake/exhaust opening area are key aspects of state-of-the-art ICE design. You give up both of these with ported engine designs.

Wondering about these kinds of things is great, but be conservative with your assumptions, and generous in your interpretation. It's condescending and narcissistic to assume that you can take a cursory look at the Duke engine, wave your hand, and solve a massive design flaw.

[JoeAltmaier]

Oh get off your high horse! I'm speculating. You condemned the design in an earlier post, right? There are all sorts of possible geometries, and many have been tried; some are found wanting. Elsewhere I speculated about using such an engine for constant-speed operation e.g. a generator. It might be a win there, where the ICE responsiveness is not a priority.

Its great to hear from an expert, though one that's clearly invested in the current popular technology to the exclusion of admitting any benefit to this one. I thought you'd be right on board with speculating about where this went wrong. Sorry to have misjudged.

[bradleyland]

I'm a novice, not an expert. I have a great interest in cars and engines in general, and I've pursued them to some degree, but I'm not an engineer. I have no where close to the level of expertise that the Duke engineers do.

> I thought you'd be right on board with speculating about where this went wrong. Sorry to have misjudged.

You've misread me. There's no thing wrong with asking questions. For example, take the question:

"Why can't we rotate the disc instead of the cylinders?"

Versus your statement

"The idea of valve-less cylinders via rotating ports can be done either way - rotating cylinders or rotating shaft - so reverse them."

You state this as if it's obvious, and it is obvious. It's also obvious (to someone with domain knowledge) that it's not a simple matter. I took us part way down the rabbit hole, and I'm always happy to do that, but it really gets under my skin when questions are states as presumptuous declarations such as, "so reverse them." Not to mention this one:

"Just wondering who got it wrong the first day and went down this path."

This presumes that the Duke solution is the wrong one, and your solution is the right one, but you aren't even familiar enough with ported engine designs to know the basic drawbacks. Again, I'm not an expert, but I know enough to know that I can't make these kinds of presumptions. You don't, and my suggestion is that you should recognize and start with questions rather than insulting someone else's work.

I know this comes across as a scolding, but I genuinely don't mean to be harsh. I just felt like I should say something because of the way your writing came across.