- 2 days ago
There have been many engine valve designs since the dawn of the internal combustion engine. What made poppet valves stick? (See what we did?) There were many other designs and some, like the sleeve valve in the Bristol Centaurus WWII radial aircraft engine, that worked very well. Classic Kevin Cameron stuff here as he and Mark Hoyer discuss the relative merits of engine valve types.
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SportsTranscript
00:00:00Welcome back to the Cycle World Podcast. I'm Mark Hoyer. I'm the Editor-in-Chief, and I'm with Kevin Kamin,
00:00:05our Technical Editor.
00:00:06Today, we're talking about the pop-it valve. We're going to dive into the valve. The pop-it valve, our
00:00:12little tulip, you know, little valve that pops up and down.
00:00:16It has usually a coil spring. The smart people use a coil spring, not hairpins, as on a Velocet, if
00:00:22we're going to get out of the gate already here, folks.
00:00:25Yeah, so coil springs, pop-it valve stems, sometimes we sodium cool them. Lapping valves can be a very soothing
00:00:33process.
00:00:33I have a valve machine. I can cut faces. I kind of like that. I like seeking that seal, and
00:00:40we think it's important.
00:00:42But there have been many other alternatives to the pop-it valve, and there's, you know, sleeve valves and rotational
00:00:48valves,
00:00:48and I'm sure Kevin's going to bust out something that's 1865, so let's just hand it over.
00:00:55Well, there are two reasons, two different periods when alternatives to the pop-it valve were considered,
00:01:05and some were adopted for a period of time. And one, as you would expect, is at the beginning,
00:01:12at the beginning of any new technology, in this case, the internal combustion piston engine,
00:01:19a mad outpouring of ideas, and some of them tremendously ingenious.
00:01:28And then commerce steps in and says, what can we make here? This is too complicated. This has too much
00:01:38handwork.
00:01:39So, hmm, this looks like a good solution. And pop-it valves were good for one major reason,
00:01:50and that is when they were closed and under pressure, nothing moved.
00:01:57The pop-it valve became just like a big piece of stone in a stone floor, the combustion chamber.
00:02:05It was just sat there.
00:02:07Well, and the pressure's holding it against the seat. And when it's 1,000 PSI in there, man,
00:02:12we're just jamming the valve up. So that does sound good. I like the idea of the,
00:02:16it's very easy to drill a, well, it's not easy, but drill a straight hole, and then that's where the
00:02:22valve goes. You just drill a thing. Here's one for the stem slash guide, and here's one where the
00:02:29valve seats, and it's concentric, and you put it in a lathe, and you're done.
00:02:32I mean, that's simplification, but yes.
00:02:36So there's a tendency, an economy-driven tendency, to adopt choices that are effective,
00:02:48long-lasting, inexpensive. And the pop-it valve has much to recommend it. But at the beginning,
00:02:57when cam contours were just straight lines and circles, there were a lot of impact loadings in
00:03:05valve trains and a lot of clatter. So the so-called silent night, K-N-I-G-H-T,
00:03:17the night sleeve valve, which was two sleeves, one within the other, and then the pair of them put
00:03:24into a cylinder bore, the two sleeves were moved up and down by their own little crankshafts and
00:03:31connecting rods. And this enabled the four strokes of the auto cycle to be performed.
00:03:40And it was quiet. So British Daimler adopted this thing way back in the single digits and stuck with
00:03:49it until the 1930s. So there was a special application, namely, quiet engines for wealthy
00:04:01people who cannot be disturbed as they are swiftly moved from place to place. The second
00:04:13set of pressures that sought a possible alternative to the pop-it valve occurred in the 1920s.
00:04:22And what was happening in the 1920s was that people had started the mad progress of raising the
00:04:30compression ratio until, what's that noise? What's that sound like? Two rocks being knocked together
00:04:36underwater. Well, it was a normal combustion cycle from the spark up to close to peak pressure.
00:04:48And only at the very end of combustion were there sudden, violent, and destructive pressure spikes.
00:04:57This is detonation. What's happened here is that progressive heating of the still unburned remnants
00:05:06of charge out near the cylinder wall changes that stuff chemically, releases little fragments that
00:05:13are, that encourage a chain reaction. And suddenly you have supersonic combustion with pressure waves
00:05:21that can knock softened aluminum off of your piston or off of the cylinder head. Oh, we don't know.
00:05:30We're not having that. So one of the possible causes for abnormal combustion was the presence of a
00:05:38very hot exhaust valve in the combustion chamber. And that is what made the sleeve valve attractive.
00:05:50Nobody cared about quietness except quieting down detonation. Um, but, uh, Harry Ricardo,
00:06:00who was one of the deep thinking pioneers of the IC engine and also a, um, a consulting engineer. I
00:06:10think he,
00:06:10he did okay in his career, which ended in 1974. Um, and the other was, uh, the Bristol airplane company
00:06:22with Roy Fedden, a, a man noted for never letting up. He was thinking all the time. He was trying
00:06:35to work
00:06:36around the clock. He expected his, uh, engineers to do the same. He looked at a different kind of sleeve
00:06:46valve. This is 1927. Same with Harry Ricardo. It is a single sleeve.
00:06:52And it was invented by two different people, uh, Burt and McCollum and the single sleeve
00:07:04performed
00:07:09this motion. It went up and down while oscillating this way. So it went
00:07:19you'll have to explain what you're holding in your hand, Kevin. What I'm holding is a sleeve valve
00:07:26from a Bristol Hercules air cooled radial sleeve valve engine of which
00:07:3557,400 were built during World War II. And up to 1960, they continued to produce them because they were
00:07:45very reliable and the ports you see in the sleeve, uh, can line up in varying degrees with ports
00:07:57in the cylinder so that as this spiral motion is performed, it carries out the four stroke cycle.
00:08:10And to this day, there are people who are, who are staunch supporters of the sleeve valve. It's a crazy
00:08:20thing that it wasn't carried forth after, uh, 1960. And there are the nonchalant jingling the chain in their
00:08:29pockets, self-assured poppet valve advocates whose attitude is, yeah, but as a mechanical curiosity,
00:08:38if they put the same amount of money into poppet valve engines, they'd have been farther ahead.
00:08:45And this kind of thing is wonderful because it is so purposeless and pointless. Uh, the,
00:08:53the sleeve valve was made to work very well, but it took Roy Fedden and his team 12 years. Now
00:09:02that
00:09:03sounds like a real condemnation, but it took even longer to make the poppet valve as successful as it
00:09:10became, because in the beginning they made the valves out of steel. And it went to pieces, uh, the seating
00:09:23corroded, chunks came out, the material became red hot. Um, it was, it was a disaster. So
00:09:36then they thought, well, what, what have we got here? And someone said, high-speed steel, the revolution
00:09:44in the machining industry, alloy of, uh, cobalt and tungsten. Well, uh, where is a chromium and tungsten?
00:09:55Anyway, a bunch of tungsten is in there and tungsten has a, an out of sight melting point of about
00:10:013,300 centigrade. That's our TIG, uh, TIG electrodes. That's why we have various kinds
00:10:08of tungsten on our TIG electrode because that's what we weld with and it's very heat resistant.
00:10:12Yes, indeed. It tends to hold to itself. It doesn't evaporate. It doesn't melt easily. Anyway, uh,
00:10:22these, uh, tungsten steel exhaust valves were a big improvement. And
00:10:33they were the, the coming thing until, uh, tetraethyl lead began to be, uh, used as an
00:10:43anti-detonant in percentages from one CC to six CCs per gallon. The extremely poisonous tetraethyl
00:10:54lead don't get any on your skin. It'll kill you like, uh, methyl dimethyl mercury.
00:11:01And for the same reasons, um, tetraethyl lead had a miraculous detonating, detonation suppressing,
00:11:10uh, quality. And they tell us that what it actually did was some of those little fragments,
00:11:19uh, hydroxyl radicals that are produced by heating the unburned charge over a period of time as the
00:11:25flame front travels, uh, out toward the cylinder wall. It turns those hydroxyl radicals into harmless,
00:11:35um, gas. And, uh, it also has been accused of, uh, reducing the intelligence of urban children and
00:11:48many other things such that it is no longer used in gasoline.
00:11:54But when engines with, um, tungsten steel valves were run on leaded gasoline,
00:12:02in the words of, uh, Sam Herron, another tremendous pioneer of the IC engine and a specialist
00:12:10in air cooled design, he said the valves, the exhaust valves looked as if they'd been dipped
00:12:20in molten slag, but help was at hand. Now, the reason that I'm talking about poppet valves now is
00:12:32comparing how long it took to make them successful to the 12 years that it took, uh, Roy Fedden to
00:12:39make the sleeve valve successful. So now they're saying, oh, well, look, there's this new stainless
00:12:46material that looks promising. Let's, uh, try some of that. It had originally been created to slow down
00:12:56the erosion of rifling in gun barrels, um, which is a corrosion process.
00:13:05Stainless steels such as KE965, older, uh, folk will remember that as a, an exhaust valve material in
00:13:15British bikes. Didn't care about it. It was unfazed by lead. So there was a way forward. But
00:13:25meanwhile, they're developing more and more powerful engines and exhaust valve temperature is going
00:13:31up. And at every step of the way, there was trouble so that exhaust valves had to be constantly
00:13:42improved. The next step was, oh, what if we make the valve hollow and we fill it partly with salt
00:13:52of
00:13:53some kind that will be liquid at operating temperature. And as the valve, click, click, click, does its
00:14:00little, um, hopping, it's, it's poppet motion. Um, this material, this liquid will slosh back and forth
00:14:10between the head and the stem and carry heat from the hotter to the cooler. And this was highly effective
00:14:19also. And at each step, uh, either more compression ratio, higher compression, or more supercharger boost
00:14:27in the case of aircraft engines. And the exhaust valve was seething in mindful rebellion, preparing
00:14:36its, its next destructive act. But for the moment, it was a truce so that poppet valve engines advanced
00:14:48as the exhaust valve advanced. They found that that part of the cylinder head had to be especially well
00:14:56cooled. For example, in World War one, liquid cooled German aircraft engines. They had a fresh, uh, a tube
00:15:07inside the head that carried water that had just come from the radiator. So it was at the minimum
00:15:14temperature in the system. And it had little jets at each exhaust valve. Today, we call this strategic cooling.
00:15:23That sounds modern. Yeah. Well, it's over a hundred years old. What they were doing was they were staving
00:15:32off valve ceiling, ceiling surface failure by cooling the exhaust valve seats from inside the head.
00:15:43People even tried water inside of valves, hollow valves. And of course, some of them burst.
00:15:53Bad. Yeah. Or as Mr. Yoshida used to say, bad effect.
00:16:00Yes, bad effect. I always liked that.
00:16:02Um, so this valve thing, uh, by 1953, Norton were about to, to, uh, pull out of Grand Prix racing,
00:16:16but they were still trying making all kinds of clever stuff. And one of the things that they did
00:16:22was to provide that the exhaust valve guide had a spiral passage that connected to circulating oil
00:16:34and a little heat exchanger on the right hand down tube. Now, would they have done that and taken the
00:16:40risk of the risk of getting oil everywhere if they didn't have a serious problem?
00:16:45The moment that World War II ended and a gas turbine alloy called Mnemonic 80
00:16:53came onto the market and was no longer a military secret.
00:16:59BSA breathed a sigh of relief for their 500 single, the gold star and gave it Mnemonic 80 exhaust
00:17:08valve. So the exhaust valve thing just went on and on forever. And the reason that modern motorcycles
00:17:15don't have a problem with it is their valves are small. So their heat gathering ability is quite
00:17:21limited and their valve seats are quite close to the center of the valve, which is the hottest part
00:17:29or one of them. And so, oh, also modern motorcycles are in general liquid cooled, big advantage. So in the
00:17:41motorcycle world, the problem is solved. In 1927, it wasn't solved either way. It wasn't solved for
00:17:48the sleeve valve and it wasn't solved for the poppet valve. So it was a kind of developmental race.
00:17:57Well, the most exciting engine that was given sleeve valves was Napier's 24-cylinder Sabre, which was two
00:18:05flat 12s, one on top of the other. Oh, the Sabre. I saw one at, I saw one at the
00:18:11Royal Air Force
00:18:12Museum north of London a few years ago. Amazing. Also the, the gear train. We should really, that's,
00:18:18I mean, go ahead and carry on, but let's talk about the, the gear operation. Well, we've shown that we've,
00:18:25we'll have images of the, the gear train in the middle of the Centaurus or the, the other guy.
00:18:33Yeah. Sabre. Yeah. Sabre. Yeah. Sabre or the Hercules. Yes. Uh, the Sabre was put into some, uh,
00:18:40Tempest air, Tempest fighters. Um, the, the sleeve valve haters say those things couldn't be started.
00:18:50Cold star. They'd have to wait for climate change to be able to start those things because the, the sleeve
00:18:57was in contact with a, with a huge oil film and those engines were running on 50 or 60 weight
00:19:06oil.
00:19:08So imagine the starter to turn these things. Now the, the pro sleeve valve people said,
00:19:14oh, actually they were much easier to start than you would have thought.
00:19:18One of the great things about the sleeve valve is that there is always relative motion between the
00:19:25piston and the sleeve, which means that when the piston comes up on compression and essentially
00:19:32is unmoving for several degrees at top dead center, the oil does not squeeze out from between the
00:19:39top piston ring and the cylinder wall, but rather it, it wipes on, on a continuous oil film.
00:19:47Such that, uh, experiments are ongoing at the moment to see whether sleeves that rotate
00:19:54steadily have no ports in them or anything. It's a regular poppet valve engine, but by rotating
00:20:00the sleeve, it might be possible to reduce friction. Because the sliding seal is never allowed to slow
00:20:13down and squeeze out its oil film. Well, uh, how are you going to put a steel sleeve
00:20:24into an aluminum cylinder with an aluminum piston inside the sleeve? Because the expansion coefficient
00:20:34of aluminum is much greater than that of usual iron based alloys. Well,
00:20:44that went on and on and on. But basically what they did was they started with a stainless such as
00:20:54KE965,
00:20:57which contained chromium and nickel in large proportions and which was austenitic.
00:21:05Austenitic is the crystal habit of, uh, uh, iron based alloys at very high temperature.
00:21:17And it happens to have a much lower than room temperature thermal coefficient of expansion.
00:21:28So that was good. Then we turn around, we're going to make the cylinder itself out of low X,
00:21:37which is 15% silicon. Those of us who race two strokes will remember a Gordon Jennings article
00:21:44in which he announced to the world that hyper eutectic, uh, aluminum silicon alloys were
00:21:52the heart of the high powered two stroke motorcycle racing engine, 22% silicon.
00:22:01So
00:22:05then they found that the stainless material stainless loves to stick to stuff.
00:22:10It, it, it grabs on things. If you're drilling in stainless, you have to stay under the chip
00:22:17because if you don't, the tool will ride up on top. It will glaze and all action will cease.
00:22:29And many, many exhaust valves are made with a carbon steel stem friction welded to a stainless head.
00:22:37Yeah. You can see the seam. It's really neat. Yeah. You can just test it with a magnet tone,
00:22:42tone change in it. It's, it's barely visible. It's there. You could see it, but it's, uh,
00:22:47yeah, you might be able, if the thing were very clean, you might be able to
00:22:51taste it. Like you can taste the solder joint in a ring.
00:22:56Because it's slightly different. That's a battery.
00:22:59The solder is different from the, from the parent metal.
00:23:05So, oh, what are we going to do to stop this? I've got it. We'll nitride this, uh, stainless alloy.
00:23:14Hmm. Well, to make it nitridable, we're going to have to, you know, drop in a pinch of this and
00:23:19this and this. The metallurgists, uh, their daily log is just as complicated and just as tired
00:23:29making as the development logs for the poppet valve, for the sleeve valve, for any of these
00:23:37difficult to make practical technologies. You just have to keep at it. You just have to slug away
00:23:46at the problem. So they found out that they could nitride this material and suddenly the pickup and,
00:23:53and scoring and seizing gone.
00:24:00Their troubles were never over completely, but in the U S Pratt & Whitney and Continental both
00:24:09of, uh, prototype and Continental built operational units, uh, sleeve valve engines.
00:24:16And in their work logs, it sounds like the sleeve is kind of like, yeah, you need a lot of
00:24:23centerless
00:24:24grinding machines and you need, uh, lapping equipment, but no problem. Slide it in. It works.
00:24:32But they tell you that, uh, with the sleeve from, from a Hercules, don't lay it down horizontally. It
00:24:41must stand on end. If it's not in its cylinder, if possible, keep it in the cylinder where it stays
00:24:47round. One of the last steps in making the sleeve valve practical overcame out of round.
00:24:58And what it consisted of was grinding the OD with a dull wheel. Now, what this sounds like to me
00:25:08is
00:25:10the outer surface of this grinding wheel, having been dulled in service, some other kind of grinding,
00:25:18is like a micro view of a cobblestone street, rounded stones in great numbers.
00:25:27And they beat the living daylights out of that, uh, KE-965 based alloy, maybe enough to put the
00:25:39surface in enough compression to kind of sprawling the thing round. I have no idea how it worked,
00:25:44but that was the final step for Bristol that allowed them to make one after another sleeve that
00:25:52were round did not need hand finishing. Uh, give me another three hours, boss. We should be able to use
00:25:58this thing. No, that is not mass production. That is craftsman production, which takes or can take
00:26:08forever. So they were able to make these things work. Uh, they flew a great many. They built 4,500
00:26:18sabers. They, uh, Bristol built a bigger, um, version of the, uh, Hercules called the Centaurus,
00:26:29which had a longer stroke and 18 instead of 14 cylinders. And these were big horsepower engines.
00:26:37They built 2,500 of those, uh, in the U S Pratt and Whitney built, uh, H24 engines.
00:26:48Continental built, uh, air-cooled radials and Pratt and Whitney at a point said, look, our, uh,
00:26:58what we're actually good at is making air-cooled radials. Why don't we ship the centerless grinding
00:27:03machines to England where they can be, make themselves useful and we'll get on with, with what we do best.
00:27:13So, um, it's interesting to see because, uh, Fedden's biographer, Bill Gunston, a well-known
00:27:23aviation historian is very enthusiastic about the sleeve valve. Uh, but Rodney Banks,
00:27:31who concocted, uh, fuel mixtures for the Schneider cup air races during the late twenties and early thirties,
00:27:41um, basically takes the view that, well, they made it work, but the same money spent on conventional
00:27:50engines would have gone farther and I'll leave them with that. And their, uh, their modern equivalents,
00:27:59still arguing after all these years, um, Bristol found ways to generate swirl in the cylinder.
00:28:09They could generate so much swirl that the rate of pressure rise was excessive
00:28:15and they had to tone it down. They learned to control it just as the poppet valve people
00:28:22learned to offset the intake port so that on a two valve engine, so that looking down on it,
00:28:29the flow would come, uh, sideways out of the valve and would produce axial swirl,
00:28:36which nearing top dead center would translate into random turbulence that wrinkles up the flame front
00:28:44so deeply that although the linear burning speed is low with so much surface area, combustion is rapidly
00:28:53completed. So it's sort of tired making these worn out controversies. And I think they're best left to
00:29:05themselves because we're not going back to large aircraft piston engines. They're done with the poppet
00:29:13valve remains useful. Uh, but what about alternatives to the sleeve valve? Well, before we get
00:29:21there, um, I want to talk about actuation and maybe you can help us understand curtain area.
00:29:29Oh, okay. Sure. I think there's, you know, I think it's, there's a useful difference or enough of a
00:29:36difference between how they work. And, uh, as a poppet valve is lifted from its seat, the area through
00:29:45which flow, uh, the minimum area through which flow can pass is the, roughly speaking, the valve lift
00:29:53multiplied times the perimeter, the distance around the valve head. And because the valve seat is
00:30:03ground at an angle, there's, you know, it's gets complicated, but that's basically it. It's just
00:30:08called curtain area because you imagine the valve head as having this curtain hanging down from it that
00:30:15touches the seat. The area of that curtain is the flow area. And the big deal with jumping from
00:30:25one intake valve to two is that if they both have the same total area,
00:30:32both the single and the pair of valves have the same total area, the perimeter of the two valves
00:30:40is 1.41 times greater. That's the square root of two, roughly. And this is, um, Keith Duckworth's
00:30:50magic number. Um, I'm sure he thought of it after he decided that four valves were the way to go,
00:30:58but
00:30:59everything becomes better to the tune of 1.41 times. I could just go for that. But, um,
00:31:10what does that mean in practical terms? What it means is that you have to begin opening a single valve
00:31:18sooner to make up for the difference in curtain area. What it also provides is that since the, the,
00:31:30the two intake valves of a four valve have an advantage in curtain area, they can get by on shorter
00:31:39valve timing, shorter open time, which automatically means improved
00:31:47mid-range and acceleration because you're not sacrificing something at lower revs by having this
00:31:54tremendous long valve timing. There were engines in the two valve
00:32:00race bike era that had over 100 degrees of valve overlap. That is the intake opening before top
00:32:09center, the exhaust valve closing after top center, and the angle between those being
00:32:15over 100 degrees. Now that is an RPM sensitive timing. When you get up to high speed and
00:32:22the waves in the exhaust header pipe come into step with, uh, these actions, you get a lot of flow.
00:32:35And through the overlap timing, but at somewhat lower speed, it's working against you, which is why we have
00:32:45to recognize that those great British singles, the Manx Norton, the G50, uh, the Velocet, the AJS
00:32:55were pretty much designed to win the TT where there's a lot of high speed running. How many race tracks
00:33:05have a lap record over 130 miles an hour? It's brisk over there.
00:33:13It is.
00:33:13So, um, when, when people went from two valves to four valves, they benefited at least when they got
00:33:23everything optimized, uh, they benefited from this effect. And that's why nearly all modern IC piston
00:33:33engines, spark ignition, um, have four valves. Well, there's a lot of diesels with four valves as well.
00:33:40So that was a benefit. Well, why did they go from four valves in so many World War one
00:33:51aircraft engines back to two valves in 19, early twenties, because they discovered that the flow
00:33:59coefficient that is cubic feet per minute of flow per square inch of valve head area was much better
00:34:08for a single valve in a hemi chamber than for two intake valves in a pent roof chamber,
00:34:19which is two flat surfaces. And why is that? It is because when the flow emerges from the single
00:34:28valve, it is surrounded by a curvature of the combustion chamber. The flow can attach to that.
00:34:35And that attachment allows the deceleration of the high intake velocity into pressure to fill the
00:34:46cylinder in a more efficient way. And the analogy, which I've done for myself, I, I had a hot period
00:34:57on
00:34:57the flow bench where I couldn't stay away from the thing. If you have air being blown up into a
00:35:06cylinder
00:35:06and out through an exhaust port, the valve is being held open by some micrometer apparatus or whatever
00:35:14you whatever you, whatever you like. And the bare port is exhausting into the room.
00:35:23You will get a certain amount of flow.
00:35:27Now, if you take a piece of paper
00:35:32and roll it up
00:35:36into a shallow cone
00:35:39with the small end that just fits inside the exhaust port and stuff it in there,
00:35:44measure the flow again,
00:35:47it's up 15%.
00:35:52What's going on here?
00:35:54Well, when the, when the port is bare, no pipe, the atmospheric pressure is pushing in from all
00:36:01sides at 14.7 sea level pounds per square inch, and it's pitching it shut.
00:36:07If you blow air through a reed valve, the reed's barely open because the atmosphere is beating on the
00:36:14outside of them.
00:36:18So, this business of the flow from a single valve attaching to the inside of the hemi head,
00:36:26flow attachment is just like what's going on inside that cone. The flow is guided by that surface.
00:36:35It's slowing it down, slowing it down until all of that velocity has been turned into pressure,
00:36:43equal to that in the, in the room. An efficient process, which is why the flow coefficient for
00:36:52the single valve in a hemi head is really good. But the four valve with its two intakes, all they
00:37:00have
00:37:00to do is make the chamber bigger, make the two intakes huge, then you have a Ducati.
00:37:08And, uh, the two, the single valve is an historic curiosity, like the sleeve valve.
00:37:18That's what's happened. Lots of people love their British parallel twins and their single valves
00:37:24forever. Enjoy it. Have the fun and bask in the knowledge of that flow coefficient.
00:37:37And if you look at, at the Suzuki's twin swirl combustion chamber, you will see that an attempt
00:37:43has been made to surround each valve with a little bit of a bowl. I think that the designer was
00:37:53striving
00:37:53for that same effect. So what, and what else shall we say about the poppet valve at this point?
00:38:05One of the things we can say is that as things are scaled down, their weight drops
00:38:12more rapidly than their dimension. So the two valves, two intake valves of a four valve engine way less
00:38:23than the single intake valve of a two valve engine. And that enabled, uh, uh, Mr. Um,
00:38:36uh, Oh, what was his name? The, the designer of the, of the, uh, RC one 15 50 CC twin,
00:38:47Mr.
00:38:48Air Madri was able to get the thing to run to deliver peak power at 21,500 with valve springs.
00:38:58The valves were tiny little things that hardly weighed anything.
00:39:03Whereas when you make the big valves that go into an aircraft engine way over a pound.
00:39:12So it becomes difficult to control large valves. And when BRM gave up on their V 16 in the 1947
00:39:25to 1953
00:39:26period, their next engine was the P 25, which was a four cylinder with the most gargantuan intake valves
00:39:36you've ever seen. And they couldn't control them. They tried and tried stuff broke. Um, they had to
00:39:48decide in the end, well, that, uh, we made a lot of work for ourselves, but this is something that,
00:39:57uh,
00:39:57Kim McCutcheon in his, uh, soft bound book on American sleeve valve aircraft engines,
00:40:07which, which, which C, um, comments in there. He says, here's all this tremendous work that's going
00:40:16into this sleeve valve development, but now read the same developmental log for any of the great radials,
00:40:25any of them. It's the same thing. It is plotting advance by experiments that fail. Experiment fails,
00:40:34experiment fails. Oh, this one shows promise. Let's try to understand that while pushing on.
00:40:41This is how things are designed. Now, some of that information can be stored on computers and as a,
00:40:51as an expert system or predictive, but
00:40:58computers don't design cutting edge race engines. They may, the designer may have some useful help
00:41:08from such things and simulations are good, but somebody has got to decide this stuff and
00:41:16get you close through all these steps. Usually gets you very close and the modeling can be really
00:41:21good, but ultimately running it is how you find out whether it actually works. And usually it seems
00:41:28like usually it doesn't work. There's some unforeseen problem and there's, and we know,
00:41:33we know that at Honda, uh, back in the NSR 500 two stroke, uh, GP bike era that there were
00:41:45two men in the
00:41:46basement of, I don't know whether it was R and D or, uh, HRC, but their job was to get
00:41:54the horsepower
00:41:56that the designers had forecast.
00:42:00And their development log would be something to read.
00:42:04Yeah, wouldn't it?
00:42:06Because when the new cylinder castings arrived and they're plated and they're ready to run,
00:42:15uh, you can imagine them picking up parts from the carts on which all this stuff came into their domain
00:42:22and thinking. Tell the wife, don't hold dinner. I'm going to be here for the rest of my life.
00:42:30Because they had experience. The designer was looking at trends. Well, what if we extrapolate
00:42:39what we've been doing into the future? Then we should be able to make this power. Should be.
00:42:48Should. Not good enough. Reminds me a little bit about the stories I've heard about pattern makers
00:42:53at foundries. So the, you design your cylinder head and then you send it to the foundry to get
00:42:59your prototype and they have to make, you know, the molds and they're going to, they're not,
00:43:03this is not like a die cast complicated mold. This is, we're going to make, it's complicated,
00:43:07but we're going to make it out of sand and stick it together and then pour the stuff in. And
00:43:15of things that happen in engines. It seems based on their experience. Yes. Based on how,
00:43:22and, um, it was something. Oh, they look at the drawing. Metal won't do that.
00:43:27Yeah. It's not going to fill those detail. That comes from the foundries in the motor valley that,
00:43:33that story I was talking to Pierre Terblanche and, uh, when he was a designer at Ducati and we were,
00:43:41you know, talking about refrigerators and coffee makers and coffee and. Oh, where's the coffee?
00:43:47Yeah. And it got to, um, we started talking about my van. I have a British van called the Thames
00:43:54and
00:43:54it has a pretty tragic cylinder head on it. You know, the bottom end is fine. It's a three main
00:43:58four cylinder has great big bearings, English Ford called the Ford console, but the cylinder head is
00:44:04just is terrible. It has two intake ports and four exhaust ports. And I was describing that to Pierre
00:44:11and I was like, yeah, it'd be nice to do something else with the cylinder head. Cause they just don't
00:44:15make a ton of power. And he's like, oh, we'll just, we'll just make one. He said, you don't even
00:44:19have
00:44:19to design it, you know, and just, well, we just need the bore centers where the cooling goes, where the
00:44:25push rods and the valves, and then they'll do the rest. He says, the ports will be great. The chambers
00:44:32will be tight. He says, yeah, the, the foundry guys like do they actually do the work. It was,
00:44:38it was pretty neat. And I, you know, I think to some degree, that's probably true. I mean, it's,
00:44:43it is a partnership. So. Well, those fellows in, in, uh, in the secret room had die grinders. Uh,
00:44:52they had all the, um, tungsten carbide birds, birds you could dream of, especially lots of those oval
00:45:02ones that are the, you can throw away the rest. And they had a system, a modular system of exhaust
00:45:09pipes, which by which exhaust pipe elements could be clicked together to quickly zero in
00:45:18on an approximate design. And I once asked, um, Dr. Blair, later Professor Blair, uh, why the length
00:45:31of the center section was so crucial change of one or two millimeters could really make a big difference.
00:45:38Because normally you'd think, well, it does is it moves the reflecting cone back and forth and it
00:45:43should just change the RPM of peak. Oh, no, life isn't that simple. He said,
00:45:51there are two resonances going on in the pipe. One goes from the convergent cone at the back
00:45:58to the cylinder and it's going back and forth. And there's another one that's going back and forth
00:46:04between the rear cone and the front cone. And they're going about three to one, except for the flat pipes
00:46:13on the 1974 TZ 750A, which were two to one. And, uh, when those two resonances come into step,
00:46:25the, the, the amplitude goes up and so does the tension in the drive chain and your motorcycle goes
00:46:35faster. But I was just, I was just considering you, you are a connoisseur of carbide cutters,
00:46:42aren't, are you not? I'm thinking of, of anyone who I know personally, the number of hours that you
00:46:48spent, uh, with long cutters and a variety of cutters in ports. I have a picture of you with your
00:46:53little half glasses in your, in your shop holding my RD cylinder and you're just getting in there,
00:47:01making it happen. My thumbs are, are bent inward from that work, I think.
00:47:10Anyway, uh, shall I move on now to the other rotary valves or do you have other?
00:47:17Well, the question, part of the question about poppets versus sleeve valves and curtain area was
00:47:22the sleeve valve opening. Oh, it was rapid. It was rapid. And in fact, the results, uh,
00:47:30were quite similar between the two engine types. Although there are people who say a proper
00:47:35comparison was never made. Whereas in the Fedden biography, it tells about the comparisons that they
00:47:41made between their puppet and sleeve engines. So, um, um, I think that, that the fact that, uh,
00:47:53Centaurus and saber powered, uh, fighters were effective is ample testimony to the utility of
00:48:04the two types of valves being right there. So basically it's a piston being pushed down by
00:48:14expanding gases, hot, hot combustion gas and a different way of letting it in and letting it out.
00:48:23One of the greats was one of the greats was designed by Frederick Lanchester who invented nearly
00:48:29everything, who had a one valve with a diverter upstream of it. Uh, the diverter would switch to
00:48:39inlet when the intake stroke was desired and the intake flow would cool the valve. Then the diverter would
00:48:47switch to the exhaust side when that function was needed and the valve would be heated up as the
00:48:54exhaust exhaust gas rushed out. That's okay. But it doesn't sound like we have any overlap.
00:49:02Well, they, they had those push pull engines where there was a, a small push rod inside of a larger
00:49:08one. And one of them pushed one of the valves open and the other one pulled the other valves open.
00:49:15Um, I think Curtis built some that way. And so did a lot of other people.
00:49:23So onto the, um, Aspen valve, Frank Aspen was a salesman and he envisioned a conical
00:49:33plug like thing with the combustion chamber in its bottom. And there would be, um, ports leading
00:49:41out of this rotating plug to their respective ports. And it wasn't a crude thing. That is,
00:49:52they didn't allow combustion pressure to jam this cone up against the aluminum head and jam.
00:50:01There was a thrust bearing. There was a sort of clearance. There were attempts at seals.
00:50:10It was a waste of time. Uh, Harold Willis, the racing manager at Velo put about six months into this,
00:50:19as I recall. And then they said, well, that didn't work.
00:50:24Norton did one in developed between 52 and 54 in which the rotating element was a cylindrical
00:50:33rotor in the head. And there was a rectangular orifice in the head that was served as this
00:50:43rotating pipe had the exhaust function on one end, the intake function on the other.
00:50:48And where they came together, they were like this. So that as this whole thing rotated alternately,
00:50:56the rectangular port in the head would be connected to the intake and later to the exhaust.
00:51:02And they were able to make 47 horsepower with this. But as, um, in Mr. Griffith's little,
00:51:11lovely little book. Um, I think it's entitled built for speed. It says that when the engine was throttled
00:51:21back as for a corner and it refused to open out again on occasion because there was a lot of
00:51:29oil involved.
00:51:31And this, uh, this cross rotary was, uh, moving toward Vankal like solutions. The later models,
00:51:40the later test units, test article, pardon me, had, uh, piston rings on the valve to seal the ends
00:51:48and longitudinal strips, uh, which very much reminds us of tip seals in the Vankal engine,
00:51:57but it was not made to work. It was not made to contain the oil. And so, uh, Norton didn't
00:52:04go ahead
00:52:04with it. Not only that, of course, uh, Norton pulled out of GP racing and AMC instituted a
00:52:14program of not spending any money on anything. And of course that going out of business saves the
00:52:20most money of all. And that was ultimately the British solution.
00:52:26But, uh, there is a site on the internet. If you go looking assiduously for information on rotary
00:52:35valves, this one has catalog 50 informative articles about all these different fascinating
00:52:46ways to do this. Some of which were evaluated by formula one teams makes wonderful reading.
00:52:55Go looking if you want more about this because, uh, it's fascinating stuff.
00:53:01Now, one of the big problems, of course, with the rotating valve is that it has to bear combustion
00:53:10pressure when it's closed. And if it's a piece of pipe supported by bearings on either end, there's going
00:53:17to be bending loads. The pipe will go out of, out of, out of round under that load.
00:53:26Oh dear. What, what can we do about this? Well, people said, let's stop the valve when it's under
00:53:35pressure for the 30 degrees, the last 30 degrees of compression and the first 90 degrees of the power
00:53:41stroke. And then we'll let the valve catch up. This, which is exactly what the Geneva drive
00:53:48film advance mechanism in a movie projector does. It advances the film. It puts locking pins in place
00:53:57to align it. The shutter opens. An image is thrown on the screen. The shutter closes. The locking
00:54:04pins pull out. The Geneva mechanism advances to the next frame. 24 times a second.
00:54:15And like that. So people just kept trying ideas one after another. And that's what happens in
00:54:24engine development. And if you have, uh, the talent of people, the talented people, the resources,
00:54:33uh, and the time, uh, you can get a result. For example, that Saturn five thing that flew human
00:54:44beings to the moon, they didn't draw that on paper and build a prototype and fly it. There were a
00:54:53lot of
00:54:53steps to make it happen. A friend, uh, described working for, um, what was it? Uh, rocket dine,
00:55:07one of those companies, he said that they would put short skirted, um, F one engines on the test stand
00:55:17and they would start them. And there would be a clang and the whole thing would roll down the hillside
00:55:25and the bulldozer, which already had its engine running would go over to collect it ready for the
00:55:32next test because they were trying to solve the problem of combustion instability. One test after
00:55:39another until they got it right. So that's the nature of these things. Gyro gear loose does not invent things.
00:55:50Actually, things are developed in a multitude of steps.
00:55:59Uh, so it's, uh, you, if you peruse those 50 articles, you'll see some really ingenious things.
00:56:08I talked to a man, a German fellow who had come over on the paperclip program, no passport,
00:56:15no questions asked as long as you'll work for us corporations, uh, with sincere dedication.
00:56:23And he had a rotary valve that he had put, he had made a cylinder head for a Honda 50,
00:56:29Mr. Crowder. And his valve was spherical because as he observed, it's easy to seal a sphere with a round
00:56:39ring.
00:56:43Um, there's, there's all these arguments. Oh, this should have worked. Oh, those stupid fools.
00:56:50Here we are with the poppet valve after all this effort.
00:56:57And we gave it up in aircraft, you know, basically in, in the mid forties, as soon as the turbine
00:57:02came,
00:57:03it was sort of like, well, why are we?
00:57:06Oh, no point in this thing.
00:57:07Yeah. I mean, a lot of mucking around to make a piston engine work and make the power and reliability
00:57:14we
00:57:14need. And then suddenly the turbine comes and we started figuring out our stages and
00:57:19our metallurgy. And then off, off to the races, suddenly there was a Concord, you know, and we
00:57:24were flying the speed of sound with people in a tube going on vacation or doing important captain
00:57:35of industry things. I liked the quote that you had at the end of your notes. Um,
00:57:39the summing up provided by Robert, uh, Schleifer, author with SD Heron of the excellent development
00:57:48of aircraft engines and fuels, 1949. He notes that no engine that was not already running in 1940 was
00:57:55able to achieve anything of note during World War II. It takes significant time to develop mechanical
00:58:01systems to maturity. That is what you just said, development. It's not invented, it's developed.
00:58:06And if you ask, uh, gun designers, they will say typically a program is seven years.
00:58:15And, uh, well, what about,
00:58:21what about, uh, the pioneer of all the automatic guns and other guns that are not automatic, um,
00:58:32who designed things in his head with one hand on the table and the finger tapping.
00:58:41He could visualize it all. Oh, there's going to be an interference with this part. Let's see now,
00:58:47here's what I'll do about that. And then his brother would do the prototype
00:58:52and then they would work on that until they got it to work. I don't know if that process took,
00:58:59um,
00:59:02seven years, but about half of the, uh, semi-automatic, um, firearms at one time had been designed by this
00:59:13one, uh, person. So it's a, it's a tough road to make mechanical systems work, be reliable,
00:59:28be manufacturable, be cheaply manufacturable. Yeah. And you got to hit all those notes.
00:59:40Yeah. Repeatable parts. That's what we were looking for. As you said earlier about no hand
00:59:45fitting of things, it just comes out. It comes out of the mold. It comes out of the
00:59:49machine and it's ready to put together for years. Um, Bristol had running prototypes that gave
00:59:56excellent performance, but they couldn't manufacture the sleeve as an interchangeable part.
01:00:03And through the process that I, um, briefly, briefly outlined by which they came up with sleeves that,
01:00:13that did work and the process that could be repeated, um, it took a long time.
01:00:23Well, that's it folks for the poppet valve and alternatives.
01:00:28Here we are just poppet valving away. Um,
01:00:33you know, I have a valve machine in my garage that I can
01:00:37do a perfectly adequate 45 degree cut on and make my triumph run, as you said, like,
01:00:43well, let's just enjoy what it is. And that's kind of how I approach that part of the hobby is.
01:00:48It's something I feel like people who have Toyotas with 300,000 miles on them,
01:00:52just for the hell of it. Just for the hell of it. Yeah. Um, people have learned to make things
01:00:59that,
01:01:00that are amazingly durable. Whereas at the beginning of motoring, you sent your chauffeur to
01:01:06the factory to take a course in how to maintain the engine, which included reseating the valves every
01:01:14six weeks because the valve material was poor. And because the compression ratio was low, the exhaust gas
01:01:22was extremely hot. So, well, even in the 1977 ish, the, to the triumph TR seven, you know,
01:01:32the wedge shaped triumph that they came out with, with the four cylinder. Um, I want to say at a
01:01:40very
01:01:40short mileage, maybe 30,000 miles, they were still calling for you to decoke the cylinder head
01:01:46on a car sold in 1977. Yeah. Well, that's one of the things that fuel injection,
01:01:54digitally controlled saves us from. There's no free carbon in the combustion that results from
01:02:02in meeting emissions. And it takes free carbon to develop that coke. And I remember it's really
01:02:12hard scraping that stuff. It's terrible. Oh, it's impossible. Yeah. But, um, there is a,
01:02:21there is a cachet associated with those faraway days of lads who've been given a trashed out
01:02:32motorbike of some kind and are determined to make it go again.
01:02:40Well, that process of making it right is satisfactory in its own right.
01:02:45Yeah, it is really. It's like cooking, you know, and we, we, there are very efficient ways to get a
01:02:50meal.
01:02:51But you're still chopping and smashing the garlic or whatever you're doing, you know,
01:02:55making the dough rise and thinking about the temperature of the water and which kind of yeast,
01:02:59because yeast, your type of yeast makes a difference. Slow proof, fast proof, how hot is the
01:03:05oven? You know, how, how, how quickly do we seal the outside of the bread? So that the inside has
01:03:12the
01:03:12texture, moisture and flavor that we covet. Yes, covet. It's, it's all part of the process,
01:03:19you know, lapping your valves. There's something, you know, I don't know. I just made a short video
01:03:25about fixing the points, uh, in the XS 650, the, the points, there's a shaft that goes through the
01:03:33camshaft. It's an overhead cam, 360 degree parallel twin XS 650, super common engine made 500,000 of
01:03:40those bikes. And it has, it has mechanical points. It's two cylinders. So on the left side of the head
01:03:47under a chrome cover are the points for each cylinder. And then on the right side is the
01:03:54advanced mechanism and there's a metal shaft. So there's weights and springs for returns. And so
01:03:59when the engine spins faster, the weights wing out and the springs, you know, are overcome by the
01:04:05force of the weights and it advances the ignition timing. So we, we motor off and when you close the
01:04:11throttle, all that's supposed to go and you go back to idle and it should be exactly the same
01:04:17ignition timing. So if you set 10 degrees before top dead center, that mechanism is supposed to
01:04:22every time take you back to 10. But if that shaft is not properly lubricated, which was the case in
01:04:28my
01:04:28old bike and the springs were sacked out, which you could actually see it's an extension spring and you
01:04:33could see the space between the coils, which there should be none. Yes. And you, they're cheap. You
01:04:39buy new springs. It's a, it's a main, it is a maintenance intensive thing. It is a mechanical
01:04:44switch. We've solved that with transistors and micro boards. And, you know, we have ECUs that can
01:04:51calculate billions of things a second and just do whatever we want. That's over here and that's cool.
01:04:57And I love it, but also I fixed that. I pulled the rod out on the XS650. Got a result.
01:05:03Yes.
01:05:03I lubricated. I cleaned the, I cleaned the gum off of it because they were sticking and the springs
01:05:09couldn't, they were, they were just sacked out. And so I cleaned all that. I put the rod back in,
01:05:15I put the weights on and then snap. I took a 10 millimeter on that nut that's in the middle
01:05:20of
01:05:20those weights. And I went like this and I just pulled it off and it goes, snap. And it goes
01:05:26back
01:05:26to idle. And then I'm like, well, this is what we want and kickstart. And sure enough, no more floating
01:05:31because it wasn't staying advanced. Anyway, that's for me, that's part of the process. That's
01:05:36the, that's the attraction is you're making something right again. And you're making them
01:05:42something that is a complicated way to now what we can accomplish very simply, but it's a complicated
01:05:48way to make something simple happen with a desirable result. Yes. And that is pretty much for me,
01:05:55the vintage bike hobby. Yeah. Or cars. The cold weather we've had fixed it so that my wife's tractor,
01:06:02which deals with the product of keeping horses, it would start, but only feebly. And then it would
01:06:11gradually quit. You could do it as many times as you like, same result. So yesterday I went up to
01:06:19change the fuel filter and if everything is rusted and everything is in the way, shall I raise the
01:06:28bucket? Oh, now this other arm is in the way. So I was there for some time. I put in
01:06:34the new filter.
01:06:36I got it aligned top and bottom so that I could get the ring up and tighten it.
01:06:41I bled the system instant starting up to the top of the tack if you want. So satisfying because
01:06:50although it's a dumb ass thing, of course you change the filter. Why didn't you change it months
01:06:56ago, years ago? There it was covered with wax that has precipitated out of the fuel at very low
01:07:04temperature. But it's possible to fix it. Now it's running. Yeah. See, now I want to tell you about my
01:07:11pressure washer. Starts, runs. Well, I got a free pressure washer. It has a little key and carburetor
01:07:17and a Honda 200, a GX200 engine, and then a three-piston pump. And it would only run if you
01:07:24pulled the
01:07:25trigger and there's this unloader valve. And the unloader valve is what relieves the pressure. So if
01:07:30you're power washing, it's going, it's 3,700 RPM. I checked it. It's what it's supposed to be
01:07:36against the governor and it runs, but it would start to cycle and it would go, and it was going
01:07:42against the governor. And it was because the unloader valve was sticky. It was corroded. And
01:07:48the O-ring on the high pressure side was failing. And so it was getting variable bypass essentially.
01:07:56And so you take out this very dumb valve brass thing that used to be available for 13 bucks,
01:08:01but they're no longer available for this pump. So then you're in, in the O-ring shop going like,
01:08:08is this about right? Well, the durometer is different, but maybe this will work. So you slap
01:08:12it together. I put a little bit of a, you know, Vaseline on it to, and what do you know?
01:08:19You put it
01:08:19in and you pull the thing and you don't have to pull the trigger and it'll bop, bop, bop, bop,
01:08:22it'll sit there and idle. And you watch the unloader valve, you let go of the trigger and
01:08:27the unloader valve pulls a compression spring. So the pressure pushes the piston this way to open
01:08:32the bypass when the pressure rises and you watch the spring compress and you're like, Oh, and it's
01:08:38not wobbling. It just goes and it sits there. And then you pull the trigger and it goes back and
01:08:43you
01:08:43get pressure and you max your RPM and the pleasure of pressure washing. The joys of fixing stuff. Yes.
01:08:53It's good times. So, well, thanks for listening, folks. We appreciate the support. Hit us in the
01:08:59comments. We love being here and doing this. And I think we all appreciate Kevin's work. I certainly
01:09:08do. Decades of it and the ability to have these conversations with someone who's both willing
01:09:16to talk about it and has enough to talk about that we can venture into facts. It's a good times.
01:09:24Thanks for listening. We'll catch you on the next show.
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