Hi all I wanted to share a project that is a long time coming.
This all started back in high school. A buddy of mine had come across a company that had a design for rotary valve heads for a small block ford with some impressive claims. I always thought it was pretty cool. Years go by but I never forgot about it and periodically spent long hours searching the end of the internet looking at rotary valve head designs and checking on the latest developments of that company. I then go to college for an engineering degree and managed to talk the school into doing a directed study for which I would design a rotary valve cylinder head for credit to satisfy some technical elective credits for my degree. I went out and bought 4hp horizontal shaft engine and designed a cylinder head for it. In another class I designed and built a engine test stand dyno for the engine. I worked in the student machine shop at the school and was able to get most of the machine work on the new head design done but was not able to get it finished before I graduated. After graduating I bought a used small Grizzly knee mill that was converted to CNC and a manual lathe. After much work I had a prototype that started and ran but left much to be desired. During this time I exchanged some emails and phone calls with the company that had the rotary valve head design. I was very interested in being a part of bringing the technology to market and eager to work with them. I told them I wanted to see a working prototype I could test out and they were not interested in that. They told me non-exclusive US only patent rights was going to be on the order of several million dollars. After a few more emails with them trying to get them to work with me I gave up on them. Personally I think the whole company is a scam but I was still intrigued by the idea of rotary valve. I then changed direction in occupation which landed me overseas for a year during which time I had no shop to work on the new prototype. Since then the patents I was interested in expired so I figured game on! My plan was to work on the small engine some more or go straight to doing a car engine. Two different co-workers I made friends with convinced me the 4G63 engine would be a great candidate for such a design. I took their advice and bought a used head off of ebay and spent the next year drawing up the stock head in CAD and the new rotary valve head design.
Fast forward a year and I got back to the US and started setting up a shop. I built a furnace and started learning how to cast aluminum. bought a full size knee mill I converted to CNC that was big enough to do the machine work for the new head design. After tying to balance a marriage and a long commute to my day job and long hours as an engineer I convinced my wife to take a year off from work to work full time on the project. It was really tough going and a really steep learning curve but I finally see the light at the end of the tunnel. So now over a year later and having taken longer than estimated and costing a small fortune; my eighth head casting, so far seems to be usable and is just about ready to start up for the first time.
Here is the cylinder head casting next to the sand molds
Here is the head installed just about ready to go but with all the wiring.
I was impressed with your dedication to your project it looks like this turned into a full on obsession :-) my experience with rotary valves is limited to only one engine a long time (30 years or more ) ago but thought it was a really good idea. I should think advances in materials makes it more viable now.
Over the years I have designed different variations of rotary valve engines and even built a few and have come to the conclusion it is somewhat like chasing rainbows. They looked promising in my head but when you start taking into account the enormous loads, expansion and the need to lubricate these valves and their bearings and fit it all in a limited space that needs cooling with space for a spark plug and an injector it starts to fall apart in reality. The biggest problem is in my opinion expansion, the exhaust valves have to have so much running clearance that there are compression losses which defeat the object often they will fail through distortion. Several of my designs used the same valve for exhaust and inlet keeping things a little cooler, others have coolant passages running through them. Another design uses a rotating cylinder again water cooled with valve ports in the cylinder wall, there are many others all of which would work - in a fashion but realistically none would have been any better than conventional valves. Far better than me have tried and failed, since the IC engine was invented people have been experimenting with them. The sleeve valve used by Bristol and others worked well but they never cured the excessive oil consumption. Probably the most successful so far is the Coates spherical engine which looks like your design but it has yet to stand the test in time. I wish you the very best of luck, many modern engines achieve their high power and efficiency through variable valve timing and in some cases mechanism to direct inlet flow to compensate for different engine conditions, both of which are difficult if not impossible to achieve with any kind of rotary valve. Rotary valves could be used to advantage on engines that maintain constant RPM and power ie in situations that will work well with fixed valve timing and have a constant thermal loading such as industrial engines or aero engines. Large diesel engines which could take advantage of the higher compression ratios achieved and cause less thermal stressing might be more suitable candidates than the average petrol car engine which needs a much wider power band that often takes advantage of VVT. Keep up the good work but just remember no matter how good your idea is someone will have already done it. We have the advantage over the old designers in that we have CAD and access to much better materials and manufacturing methods so revisiting these old ideas might have some merit and the patents will have expired, check out the Aspen engine for example. All the best Dave
I assume you have seen the model RCV engine ? they still seem to be making engines which was a surprise to me.
It struck me what Bdrangdo said about constant rpm engines being a better application , A friend of mine develops hybrid cars and the engines they are using are a constant rpm IC engine driving a generator for recharging the batteries .. He explained to me that running at a constant rpm the engine can be tuned for very high efficiency,
I for one had never heard of the RCV engine until I checked out their website, like many model engines it is just that and could never be scaled up to any degree, the oil consumption and resulting smoke would make it fall foul of emission regulations as would most other novel engine designs. All practical valve designs of any kind need some kind of lubrication some of which will be lost or burnt. The exhaust valve in particular is often prone to gumming or carbon deposits building up which may not be immediately apparent until the grand test of time when it is too late to change the idea. Modern engines with conventional poppet valves will run for thousands of hours without these problems largely because they are easy to seal and the seals are away from the high temperatures which is the killer for any kind of rotary valve. They may well work reasonably well for a short time but most will ultimately fail because of the heat and lack of lubrication. The valves that Goldenfab has shown are also exposed to the full combustion pressure which can produce a huge load on the small bearing surface area they rotate on. I am not sure how they are lubricated or sealed but the inlet side will be exposed to partial vacuum which will tend to suck the oil into the combustion chamber. That said one great advantage of rotary valves in general is that they should (in theory) run somewhat cooler than the poppet counterpart and should again in theory allow high compression ratios because of the reduced tendency to detonation. Increased CR sadly also increases the bearing load and in practice rarely can go above 14 to 1 because of pumping losses. I know all this sounds a bit negative maybe there is an idea out there waiting to be thought of but the end of the IC engine is in sight at least for road vehicles. That is why I suggested that an engine of this kind would be better suited to an application that requires a narrow power band which could allow optimal valve timing and port shape such as encountered in industrial engines driving generators and the like and of course as an aero using a variable pitch prop. The Wankel engine is a good example of this and takes advantage of the fact that these applications are not subject (as yet) to emission regulation. The Wankel engine has been around for 30 years or more and has seen the same time scale of development and even now is not really practical for road use because of oil consumption and fuel inefficiency. All the best Dave