Idea for 4 stroke rotary valve.

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.

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

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.

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.

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!

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

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

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

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.

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

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.

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

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

Click to expand...

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

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

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.

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.

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…..

Click to expand...

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

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

Why is overlapping undesirable?

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.