Waissi Engine Update: The Differences Between Waissi and Bourke Engines
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Waissi Engine Update: The Differences Between Waissi and Bourke Engines

Oct 27, 2023

Bourke Engine (click for animation)

In a comment to my post last month about Professor Gary Waissi’s new piston engine that has no connecting rods between the pistons and the crankshaft, one of our readers asked about similarities to the Bourke Engine, invented by Russell Bourke. Based on the diagrams of the Bourke motor, that seemed like a good question, so I asked Prof. Waissi about it. I received his reply today. Waissi said that while there were similarities between his engine and Bourke’s, there were also substantial differences, resulting in the Bourke engine having more operating friction. Dr. Waissi also said that he hoped to have a two-cylinder prototype of his own design assembled and running by the end of this year. Waissi’s response after the jump.

Thank you for the message, and for writing the article. I am very familiar with the Bourke engine and concept; a Scotch Yoke engine. A number of similarities, including aligned cylinders, and connected piston structure. The main difference is, as clearly shown in the animation, that the Bourke Engine uses a “conventional” crankshaft with “yoke”. There is no “yoke” in the Waissi Engine, because the crankshaft is like a camshaft (a straight shaft).

The Bourke engine does also not use hydrodynamic lubrication in-between the bearing rings, which does not, in my estimation, reduce the friction, but increases it. Both engines, the Bourke and the Waissi Engine, have only primary piston forces (because of no piston rods), and therefore are simpler to balance. In the Waissi Engine design the crankshaft is actually like a camshaft — a straight shaft; and an off-set camdisk, and a hydrodynamically lubricated bearing ring. The bearing ring has a significantly larger surface area (between the inside surface of the ring and the disk outer perimeter) distributing the piston force to a larger area resulting into a lower bearing pressure.

Another advantage of the Waissi Engine is manufacturability — straight shaft vs. crankshaft — especially with multi-cylinder engines; you can use the same cam(crank)shaft for engines with different piston strokes, by just changing the disk (as the stroke depends on the disk off-set). For example in an F-1 engine the stroke is 40 mm; andf for “regular” engines the stroke varies widely (60- 70- 80- 90- 100 mm). With regular engine designs, including the Bourke engine, for every variation you need a new crankshaft. With the Waissi Engine from a F-1 engine to a pick-up truck engine you need just one.

I am currently working on a two-cylinder version of the Waissi Engine. My plan includes to get a testable version running before the end of the year. (A two-cylinder version, because it is cheaper to build).

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The only differences I see between the Wasai and the Bourke are the diameter of the crankpin journal and the structural method of connecting the two opposed pistons. Whether you you use anti-friction (Bourke) or fluid film (Wasai) is moot. If i were to bet on which is lower friction, I would put my money on Bourke. A problem that both these engines have is balance. Unlike an opposed twin crank engine, the pistons do not "box". Instead they shuffle back and forth. Yes, you can put a balance weight on the crank/eccentric to oppose the reciprocating mass, but then you introduce an unopposed reciprocating mass acting perpendicular to the piston. Some designs of these types of engines use two pairs of pistons in a cross type arrangement to deal with this. But then you will still have the second order (moment) shaking forces to deal with. I agree with the commenters who pointed out that this mechanical fiddling doesn't do anything to improve the thermal efficiency. What is needed is something that turns more of the fuel energy into mechanical work instead of lost heat. The other area is part throttle efficiency, which is dismal for spark ignition engines.

Achieving better part throttle efficiency is THE most important engine-related way to improve fuel consumption in real-world driving. Changing the way the back-and-forth is translated into round-and-round does nothing whatsoever to affect this ... unless you can somehow vary the amount of back-and-forth instead of throttling the air supply. Very difficult to achieve in a manner that has sufficient mechanical soundness. Neither of the concepts discussed appear to do that.By the way, there is one reasonably easy way to filter out the mechanical concepts for translating back-and-forth to round-and-round to see whether they can have long-term durability: do they rely on surface contact between adjacent moving parts, or line contact (or even worse, point contact)? A piston has surface contact with a wrist pin. The wrist pin has surface contact with the con-rod. The con-rod has surface contact with the crank pin. The crank pin has surface contact with the crankcase. This allows the (very substantial) forces involved to be distributed in a way that makes the stress manageable. If there is line contact involved anywhere - rollers, cam lobes, etc. - that is a potential weak point.Yes, I realize that valves in a normal engine are operated by a camshaft with line contact to the followers ... but the forces at the valve springs are orders of magnitude smaller than the piston-to-crankshaft forces! And there ARE production engines out there that have valvetrain-durability issues because this stress point was taken a wee bit too far.There are production engines that use rolling-element bearings (line contact at the rollers) on an otherwise-normal crankshaft ... I own one. But the piston displacement on that engine is 124.7 cubic centimeters. The piston diameter is smaller than a credit card. And needle rollers have a multitude of line contacts, not just one.

@Brian P Camshafts are gone in the next 10 years (except for GM which is owned by the Chinese...). They'll be pushing the same tech that their Neanderthal brothers at H-D peddle, to the same part of the Bell Curve...Valve actuation will be 100% electric/electro-hydraulic, on a quasi-desmo system.The current, primitive, state-of-the-shelf has already eliminated gas-engine throttle plates a decade+ ago with BMW's Valvetronic. Every ignition event will have not only optimal fuel and spark timing, but optimal valve timing as well.

@porschespeed That's easy to say, but harder to achieve.I thought that electronically actuated valves made sense when in first learned what an ECU was when I was a kid. And I heard a news report of an engineering team that had actually built one a few years later (early 1990s).But, their prototype only ran at low RPM, and durability wasn't even discussed.Anyway, I agree with you that replacing a heavy mechanical camshaft with limited tunability with electronics seems like an excellent idea. But excellent/obvious ideas that haven't been implemented are often harder than they look.Why will the next 10 years be different than the last 20 years for electronically controlled valves?On the other hand, all of this may become irrelevant for me personally, as soon as I can afford an EV.

@Luke42 Very true, it's easy to see the future - it's just hard to attach an accurate date to it...Here's my case for why I see them coming in rather less than a decade on serial production vehicles. Check out my points and then make your own call.1. It works. F1 cars have had various pneumatic and/or electro-hydraulic hybrid valve operators since the mid-1980s. Sure it needed development and it got it. Straight electric is still not quite there, but there's things afoot. Easy diagram...http://scarbsf1.com/valves.html2. There's a ton of folks actively working on this with cubic feet of cash. Here's just one...http://www.launchpnt.com/portfolio/transportation/electromechanical-valve-actuator/ 3. Save for coatings, alloys, and treatments, fully controllable valve actuation is one of the final frontiers for the ICE. As regs tighten, it just has to happen - there are no options. 4. Honestly, people with way more resources than me have been at this since the mid 70s. My friends and I modded a Briggs lawnmower engine to run with no cam on hand-wound solenoids and the stone-age analog electronics we could afford in the early 80s - even though we knew we weren't going to be the ones who did it, we knew that it would happen eventually. (talk about cobbled together opto-electronic triggers and breadboards!) It's really that the tech, computing power, and cheap manufacturing have caught up with the ideas that many had 40 years ago. Much like active suspension (which has been in process for 2 decades at Bose) it's just waiting for the prices to drop and the market to not only demand it, but require it.

After three years, the inventor couldn't afford to renew the patent, which resigns this idea to oblivion, like many others.I'm afraid it takes $millions to even build a prototype and patent it. I should know, because I'm in the process of doing that very thing myself.I can never understand why people make their ideas public before they are able to substantiate their claims with real numbers taken off the dynamometer.