# Idea for 4 stroke rotary valve.



## radfordc (Jun 9, 2011)

Will this work?







The valve is a 1/2" diameter rod with two chambers for intake and exhaust. Each chamber has holes to connect to the intake and exhaust ports in the cylinder head and to the carb and exhaust pipe. The valve will run in the cylinder head and be driven by a timing belt to a gear on the crankshaft.


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## Rayanth (Jun 9, 2011)

I'm assuming from your drawing that the entire light blue area is turning, thus the white holes will line up only at certain times during the rotation?

If so, it looks plausible, assuming your timing is set to one half of crankshaft rotation, but your exhaust valve needs to be rotated- your drawing suggests it being lined up the same as intake, leaving BOTH ports open simultaneously...you will need to offset it to the proper location for the fourth stroke ( one quarter turn prior to the intake hole, fine tuned after that for best results based on timing needs)

If i'm misreading it, please elaborate


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## radfordc (Jun 9, 2011)

The drawing is for concept only...and reflects my lack of expertise with Powerpoint. You're correct that the light blue portion will rotate and that the holes for intake and exhaust will be offset as required.


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## radfordc (Jun 9, 2011)

The advantage I see to this arrangement is not having to make a camshaft or poppet valves. As long as you get a close fit between the rotary valve and its bore so that there isn't any leakage between the ports it should work. I'm thinking of using 1/2" polished drill rod for the valve and lapping it to fit the bore through the cylinder head.


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## Rayanth (Jun 9, 2011)

Your concept is similar in its basic idea as a sleeve-valve on old radial engines. In those, the sleeve was inside the cylinder and rotated to line up holes in the sleeve with the intake/exhaust ports in the cylinder. You have a very similar concept, but different execution. It should work if, as you say, you maintain a very good finish and close tolerances in the rotating portion. If you have a gap, then you'll face blowback gases to the intake port, and if this is combustion, you could also face coking and valve wear on both ports. Get a good 'tight but loosen fit and it could work very well.

It does also have the advantage of no cams, and simple timing adjustments, with easy machining. I'd give it a shot!


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## mike4517 (Jun 9, 2011)

Yes it will work.
I have seen one working the rotary valve was run at 1/4 crank speed.


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## Rayanth (Jun 9, 2011)

Unless my math is wrong, and I wouldn't put it past me, given my american education, I would want 1/2 crankshaft speed. A 4 stroke engine counts each up and each down stroke, two up, two down for four...each up/down is a rotation of the crankshaft, so every other 'down' would be an intake...or one every two crankshaft rotations.

If you ran the valves at 1/4, you'd only be intaking every 4 'downs' and creating an 8 stroke engine, with four strokes of just compressing/decompressing without any intake or exhaust.

Of course, if you had TWO holes in the rotary valve, then 1/4 speed would be the answer.

Feel free to color me an idiot if i'm mistaken


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## dvbydt (Jun 9, 2011)

Have look here for rotary valves :-

http://www.aqpl43.dsl.pipex.com/MUSEUM/POWER/unusualICeng/RotaryValveIC/RotaryValveIC.htm

On _this_ site Chuck Fellows made a great air driven opposed four with a rotary valve and I am building a V8 version.

"Will this work?" Try building an experimental single cylinder and you can tell us. 

Ian


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## n4zou (Jun 9, 2011)

Here you go and he will e-mail you the plans free. This is my next project engine.

*Ridders 4-stroke with rotary valve *
http://heetgasmodelbouw.ridders.nu/Webpaginas/aanvraag_ridders_4takt.htm

I plan on changing a few things. I'm just going to let atmospheric pressure operate the intake valve and I'm going to incorporate the rotating valve in the head.


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## ruzzie (Jun 9, 2011)

hi 
their where a couple of motors with rotary valves in the cylinder head released in the 80's
A Webra T4-40 displacement 14.3cc it recorded a power output of 1.10bhp @11200 rpm and a Condor 120
their are some Webra T4-40 on youtube you can check out


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## radfordc (Jun 9, 2011)

The Webra T-4 used a rotary valve that was mounted axially in the cylinder and used miter gears to drive it.

The web site with all the old R/V info was interesting. Looking at it I realized that I don't have to use a valve with chambers...I can just cut recesses in the exterior of the valve that communicate between the carb/intake port and exhaust/exhaust port.


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## moanaman (Jun 9, 2011)

Rotary valves most definitely work. Big plus with internal combustion is when over revved, pistons and valves don't hold meeting and destroy one another and quite operation. Big minus is sealing of gases and lubrication. They tend to be a bit smokey. The first evidence I have of a rotary valve road going car was Daimler (British) cir 1918. I think I can recall 1930'sh Willy's (USA) with a rotary valve . 

Some times these were called sleeve valves motors. Although I think of a sleeve valve engine more akin to the valve system on locomotives. 

David Dunstan Adelaide Australia, in the 1950's made a rotary valve head for the road going Holden motor (140 cu inch 6 cylinder) and mostly used in speed boats because of the racing boats in Australia of that era had a habit of jumping up out of the water so the rotary valve system did away with the fore mentioned meeting of valves and pistons. A Dunstan head Holden was credited of revving to over 7500 rpm. Wished I was a crankshaft supplier at that time. David died and so did the Rotary head.  

Barry G


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## radfordc (Jun 9, 2011)

dvbydt  said:
			
		

> On _this_ site Chuck Fellows made a great air driven opposed four with a rotary valve and I am building a V8 version.
> 
> Ian



Yes, I have a similar Liney RV-2 air engine with rotary valve. That should work for a four stoke engine, too.


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## Joachim Steinke (Jun 9, 2011)

Hi

A rotary valve with inlet and outlet channels coming from the cylinder heads side will not work very well. You will get overlapping port edges, in any cases if you want to achieve a suitable timing for an IC engine.

I think some pictures will say more than a long explanation..








In the early days of engine construction Alfred Baer for example had the idea of arranging the channels upright from the top of the cylinder head. 








But now the bore in the rotary drum will open the port twice at each rotation. So in this case the gear ratio has to be 1:4 in relation to the crankshaft. A new problem turns up, if you want a proper channel cross section the timing gets sick, this 120deg on the rotary drum means 480 crank degrees, that wont work.

For that reason the Baer engine has channels in the shape of slotted holes instead of cylinders, so the front view section is much more slender and we will get the desired valve timing, but the cross section wont get really opulent anyway.








One good and practicable way is the coaxial design like the Cross Rotary principle, in- and outlet is coming from the front and end of the rotary drum.








This allows a wide range of timing layout and you can achieve sufficient channel and port sizes (in any case you dont want to build a high performance engine). 

For increasing the port size further more you have to stretch the port openings from the cylinder side to the centre of the head. And that leads to a single port for in- and outlet duty, like the design of E. Brown you can see in this picture:








But this Brown rotary drum is a complex piece of craftsmanship, both internal channels open out into bended shapes to achieve the desired overlapping in the middle section without too much restrictions. 

Achim


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## mu38&Bg# (Jun 9, 2011)

Webra produced such engines for RC models in the 1980's. There were others as well. If power output is not the primary goal, what you have will work fine. Webra used only a single opening into the cylinder and the ports in the valve were overlapped to give as much area as possible. They still made little power. The one I have has induction through the center at the rear and exhaust radially near the front.


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## warranator (Jun 9, 2011)

This is exactly what I am building at the moment, I also thought it would be pretty simple to make, which it was. I used brass rod which I place in the head and then drilled the exhaust and intake ports. Mine is a two cylinder so I then rotated the cam shaft 180 deg and did the same. Bit hard to explain where the holes are situated so as not to interfere with intake and exhaust. I am going to drive mine with a tiny chain which I am going to make every little link and make the timing gears.


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## radfordc (Jun 9, 2011)

Joachim Steinke  said:
			
		

> Hi
> 
> A rotary valve with inlet and outlet channels coming from the cylinder heads side will not work very well. You will get overlapping port edges, in any cases if you want to achieve a suitable timing for an IC engine.
> 
> I think some pictures will say more than a long explanation..




I agree with observation about not wanting to have overlapping port edges. If you off set the carb inlet hole from the cylinder intake port I think this can be avoided. You create the proper valve porting at each orifice and then connect them with a communicating port.

Charlie


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## Maryak (Jun 10, 2011)

Charlie,

Can't see why not once the timing issue is resolved. You may want to think about slots rather than holes, not only is the timing issue relative to degrees but is also relative to mass flow rates in and out.

Hope this helps

Best Regards
Bob


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## mu38&Bg# (Jun 10, 2011)

Why is overlapping undesirable?


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## mike4517 (Jun 10, 2011)

You can see it here http://modelenginenews.org/gallery/images/pascoe_v3.jpg 
Valve driven by shaft at 1/4 crank speed.
This means ports can be smaller and helps with sealing
He has used chain drive as well.


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## Rayanth (Jun 10, 2011)

if your intake port and exhaust port are open at the same time, it's either during the end of the exhaust stroke (intake opened too early) or intake stroke (exhaust closed too late)

Why valve overlap is bad:

If it's during the exhaust stroke, then your intake port is open while you're pushing exhaust out of the cylinder. In a combustion engine, this means you're backfeeding 'bad' air into the carb, or other air supply system, and will make the engine run REALLY rough if it is forced to try and burn air it's already burned, or not at all if the backpressure prevents it from getting fuel at all (more likely.)

If it's during the intake stroke, then you're sucking in both your properly metered fuel/air mixture from the intake valve, AND residual exhaust air from the exhaust valve, thus offsetting your carefully metered fuel/air mixture, and again making the engine very rough as it tries to burn already burnt air.

Either case is bad - and mixing them both will almost surely lead to a nonrunning engine. And even in compressed air or steam engines, you end up with significant performance loss as valves try to handle air in a way they weren't meant to.

The issue isn't necessarily with the valves themselves. in most cases they're mirror images of each other and couldn't care less. The issue is more with the systems attached to the other sides of those valves - intake systems aren't designed to handle exhaust, and exhaust systems aren't designed to be feeding exhaust back IN to the chamber.

Note, in most poppet valve combustion engines, the exhaust valve IS kept open past BDC on the fourth stroke. This is carefully designed to ensure that the exhaust has plenty of time to get out of the chamber (after combustion you have a net gain in pressure, this pressure will briefly prevent any fuel/air from coming into the chamber, so leaving the exhaust valve open lets the pressure balance itself). In these engines, the intake valve is often starting to open just before BDC on the fourth stroke as well. this intentional overlap ensures that the maximum amount of fuel/air can get into the chamber, for fuel efficiency. It is not _necessary_ to have any overlap, and it's far easier to have none than a carefully designed forced overlap.

Hope this clears things up

- Ryan


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## mike4517 (Jun 10, 2011)

Ryan
You have a few things wrong in your last post.
Should be TDC not BDC.
And overlap is an advantage the exhaust system draws mixture through the open inlet valve.


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## radfordc (Jun 10, 2011)

Intake/exhaust overlap is usual for high performance...

http://www.compcams.com/Pages/416/valve-timing-tutorial.aspx
Now something quite unique begins to take place. Just before the piston reaches the top, the intake valve begins to open and the exhaust valve is not yet fully closed. This doesn't sound right, does it? Let's try to figure out what is happening.

The exhaust stroke of the piston has pushed out just about all of the spent charge and as the piston approaches the top and the intake valve begins to open slowly, there begins a siphon or "scavenge" effect in the chamber. The rush of the gases out into the exhaust port will draw in the start of the intake charge. This is how the engine flushes out all of the used charge. Even some of the new gases escape into the exhaust. Once the piston passes through Top Dead Center and starts back down, the intake charge is being pulled in quickly so the exhaust valve must close at precisely the right point after the top to keep any burnt gas from reentering. This area around Top Dead Center with both valves open is referred to as "overlap". This is one of the most critical moments in the running cycle, and all points must be positioned correctly with the Top Dead Center of the piston. We'll look at this much more closely later.


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## mike4517 (Jun 10, 2011)

Radfordc

You are right.
Some of the charge does go into the exhaust but if the tuned lenth of the pipe is right you will get a return wave that pushes it back in, this is at certain revs.
I like to set my cams up equal overlap 5 deg before TDC.


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## radfordc (Jun 10, 2011)

mike4517  said:
			
		

> You can see it here http://modelenginenews.org/gallery/images/pascoe_v3.jpg
> Valve driven by shaft at 1/4 crank speed.
> This means ports can be smaller and helps with sealing
> He has used chain drive as well.



That is exactly what I was envisioning. I knew there had to be one somewhere.


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## Rayanth (Jun 10, 2011)

mike4517  said:
			
		

> Ryan
> You have a few things wrong in your last post.
> Should be TDC not BDC.
> And overlap is an advantage the exhaust system draws mixture through the open inlet valve.



Mike,

Thanks for the correction.

I did try to pay homage to the advantages of intentional, and carefully calculated overlap but should have spent more time there perhaps.

While there is a distinct advantage to overlap, as Redford explained in his followup, there's a bit of a trade-off involved. For every day use, the advantages of an overlap are minuscule enough that it doesn't really make much of aa difference. Properly done, performance is boosted on the scale of about 5 to 10 %, and fuel economy is improved by a bit more than that, as each 'bang' is put to its full potential.

However for a non-performance engine designed by a nonphysicist, the potential for getting it wrong is potentially fatal, as in my worst case scenarios mentioned previously. A difference of just a few degrees of overlap, or an open-stack exhaust system used on an engine designed for a tuned exhaust...that few degrees could go from a 10% net boost in performance, to a loss of easily 25% or more. A few more degrees, and the engine may not run at all, especially if intake is opening too early and the residual pressure from combustion stalls the intake stream.

I did not intend to scare anyone away from any design which has valve overlap...I was trying to explain why it might be a bad thing.  My personal recommendation, especially if you're unfamiliar with the mathematics and physics behind combustion cycle engines and designing something from the ground up, is to have zero to minimal valve overlap at first, and gradually add a little overlap at a time, running the engine to see how it reacts.

Ryan


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## mu38&Bg# (Jun 10, 2011)

Model airplane engines have had significant overlap since their inception. 40-80° overlap period is common. As far as tuned exhaust, just how long of an exhaust are you putting on your model engine?

Anyhow, as we all know engine design is a compromise of many concerns. If performance is not an issue, anything works. One doesn't need to be familiar with design specific of engines to build a model engine, even one that performs fairly well, copying existing designs works just fine. And, existing designs have a lot of overlap.


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## Rayanth (Jun 10, 2011)

In retrospect (what is it they say about hindsight?) I realize I neglected to take scale into account. I have been buried in the nitpicky details of the largest piston powered aircraft engine ever to go into production, and things work much differently when you are running a 5.75 inch bore and 6 inch stroke on 28 cylinders =)

As you scale down a cylinder, the combustion process doesn't necessarily scale with it. For the same fuel/air mix, the flamefront still travels the same speed regardless of size, so in a smaller cylinder it will burn up all the fuel faster. This leads to higher Rom's through a couple other linked processes but I digress...

With the faster combustion stroke comes a MUCH higher tolerance for valve overlap, and in fact it does almost become required, as the strokes are so short and fast you simply don't have time to clear all your exhaust and intake all your fuel/air without overlap (another thing that doesn't scale well is air movement)

So to go back on my previous responses- in small scale engines, by all means overlap those valves! And I wouldn't be a very good model engineer if I didn't recommend experimenting  (on that note, do they make scale dynamometers? How would you be able to tell if one valve design over another is any better?)

Ryan


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## radfordc (Jun 10, 2011)

I worked up some draft drawings for the head and valve. The head will be 1.5" square and the rotary valve will be 3/8" diameter. The cylinder bore will be 1".


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## radfordc (Jun 12, 2011)

Here is the engine design so far. I found a set of drawings for a .60 cu. in. 2 stroke engine and revised them to use a 4 stroke rotary valve head. 

View attachment 4 stroke rotary valve engine.pdf


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## kf2qd (Jun 12, 2011)

2 problems - The size of your rotary valve will severely limit the amount of air you can move into that cylinder. I think you will need a bigger valve. You also need to work on your squish area as it will affect ignition and timing.


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## radfordc (Jun 12, 2011)

The intake and exhaust both have a 3/16" diameter orifice at the smallest point. If it turns out to be a problem it will be reasonably easy to make another valve. The ignition and timing will be done with an electronic ignition with a CM-6 sparkplug.

Upon reflection, increasing the size to 1/4" is probably worthwhile. 

Charlie


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## Drei (Jun 21, 2011)

how can you seal the ports to avoid leaks, say if you had to apply the design on a small v8 block ( a one piece block).

Thanks
Andrei


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## mu38&Bg# (Jun 21, 2011)

http://www.coatesengine.com/


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## VVTi (Jul 20, 2011)

Hello 

My english is not very good, but i want to help you. I know almost all rotary valve sytems.
One rotary valve is better than 2 valves. The diameter of the rotary valve should be relatively large.
A small diameter is too small time cross sections The biggest problem is the seal of the valve. A good material for the seal is crystalline graphite. Crystalline graphite is self-lubricating.


I think that's very interesting and "relatively simple" by MGN W12.


F1 engine MGN W12 with rotary valves. [ame=http://youtu.be/QWb70X0xELA]http://youtu.be/QWb70X0xELA[/ame]
Ilmor F1 rotary valve project http://home.people.net.au/~mrbdesign/PDF/AutoTechBRV.pdf
Patent US 6666 458 B2 rotary valve system http://www.freepatentsonline.com/6666458.pdf
THE DEVELOPMENT OF A VIABLE ROTARY VALVE ENGINE http://ralphwatson.scienceontheweb.net/rotary.html


Best regards

VVTi


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## d-m (Jul 21, 2011)

Interesting topic and one I have been interested in for years. coats international (mentioned above by dieselpilot ) is producing a vary successful rotary valve head used on gen sets. if you dig into the web site there used to be info on early testing of the ideal and its development. As I recall it was a small block Chevy in a impala wagon was there first successful engine . Also at one time they offered heads for the SBC, the key to there success was in the material used in sealing the rotary valve and as i remember the material came from the space program. Its been a few years since I have read there web site, the ideal is old but with the new technology of today the concept is vary exciting and the research to develop it even further is way past do. I for one am going to revisit there site and see whats new, and I will be watching to see how this turns out in the model engineering world. Thm: Thm:

Dave


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## mu38&Bg# (Jul 22, 2011)

I don't see any rotary valve making it in the auto industry. Variable valve timing, duration, and lift, have essentially obsoleted any rotary valve. In stationary single speed apps, like gensets, they could still have a benefit.

Charlie, is that 10cc or larger? The CM-6 plug is fairly large.


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## picclock (Jul 22, 2011)

Just my 2 cents. The fit is fairly critical as you have a large pressure differential. It may be worth considering two rotary valves arranged twin overhead cam style as this would mean the fits would be less critical, easy size optimisation of the inlet and exhaust ports, and simple adjustment of the relative valve timing.

The downside is two extra bearings a timing pulleys (cog ?) and the extra work needed.

Please feel free to ignore.

Best regards

picclock


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## mu38&Bg# (Jul 22, 2011)

That's also been done in the RC engine world. Not many were made. Cipolla 4T-TSV


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## radfordc (Jul 22, 2011)

dieselpilot  said:
			
		

> Charlie, is that 10cc or larger? The CM-6 plug is fairly large.



Yes, 10cc. Here is the head with the plug installed.


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## 1boy (Aug 5, 2011)

hi
please,Have look http://rezadarvishzade.blogfa.com for rotary valves


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