What are opening and closing ramps on a camshaft profile and why are they so important? Why do we use nested or beehive valve springs? When is it best to use pushrod valve actuation or DOHC shim-under-bucket tappets or finger followers? Should we drive cams with gears, chains, or belts? Technical Editor Kevin Cameron and Editor-in-Chief Mark Hoyer (but mostly Kevin...) talk about the intricate details of opening and closing valves and different types of drive systems.
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SportsTranscript
00:00:00We're back with the cycle world podcast brightening up as Kevin just said, I'm Mark Hoyer. I'm the editor-in-chief
00:00:06Sack world and it's Kevin Cameron the technical editor
00:00:10We are back with the cycle world podcast and we're gonna talk about
00:00:15driving valve gear and
00:00:18camshafts and
00:00:19All the subtleties that go into that
00:00:23We take so much for granted
00:00:25We can spend such high rpm now
00:00:28We don't need no stinking push rods, although some people are still using push rods, yeah, we're gonna get into all that mass and and
00:00:37Seat pressures and all these things and this is one of those podcasts where I will occasionally make comments
00:00:44to punctuate Kevin's
00:00:50Lifetime of insights and study and all the people he's talked to so why don't you help us out here, Kevin?
00:00:57Get us going
00:00:59Well the thing where we need help is the people who've spent their lives studying all this stuff and it's about to become irrelevant
00:01:05Oh, yeah
00:01:08This is the thing if if you want to get into that
00:01:13You could consider that cars and light trucks if they were electrified overnight. We'd need
00:01:21Another
00:01:2530% more electric power
00:01:28So and that isn't going to happen very soon because anytime somebody wants to build an electric power project
00:01:34There are many who say no, but in any case the four-stroke
00:01:39internal combustion engine
00:01:41Has to have valves to let the fresh charge into the cylinder when the piston descends
00:01:50the valve must then close the piston rises on compression and it rises on compression because
00:01:57The peak combustion pressure is roughly
00:02:03100 times the compression ratio in PSI
00:02:07So if there's no compression, there's no power
00:02:10and
00:02:12And if the valves aren't closed because that's that's one of any any Augustine's great lines
00:02:18It's we were talking about cam timing
00:02:20He was helping us at a sport bike shootout with some electronics and and he said we were talking about that and I said, oh
00:02:26it's always so interesting, you know this all this combination and you know
00:02:32Intake length and
00:02:35trumpets and volumes and camshaft profiles and
00:02:39Extreme cams and I'm like r6 r6 long duration and he says well, you know, all that's very very well and good
00:02:46But it's important to remember that the only time the engine makes power is when the valves are closed
00:02:51They're closed and it's a it is it's a great fundamental observation
00:02:56Cylinders been filled through the intake valve the valve closes piston rises on compression
00:03:05Ignition occurs with spark
00:03:08Although there are other ways to do that and
00:03:11The next down stroke is the power stroke. And when that one is finished you have the cylinder full of
00:03:18very hot
00:03:20Combustion gas at a
00:03:22moderate pressure of
00:03:2450 to 100 psi
00:03:26so you have to have an exhaust valve that can open against that pressure and
00:03:32Because there are four strokes, it means that the cycle is
00:03:36requires two revolutions of the crankshaft to complete a
00:03:40Down stroke an up stroke a down stroke and another up stroke
00:03:45so
00:03:47The first engines had a cam controlled
00:03:51exhaust valve and the cam was geared two to one from the crankshaft so that
00:03:59the cam would make one revolution while the crankshaft made two revolutions and
00:04:05the intake valve
00:04:08was
00:04:09Given a light spring based upon the idea that as the piston descended on the intake stroke
00:04:15the atmosphere would
00:04:18compress the spring push the valve open a bit and
00:04:21intake would take place and
00:04:24by
00:04:251900
00:04:26Count the deal in France and his mechanician
00:04:31George
00:04:33Bouton
00:04:35Had built
00:04:3620,000 of these engines and they'd been exported all over the world because internal combustion engines were the hot new
00:04:44technology
00:04:45Everybody's doing it
00:04:47So this is why you will see early
00:04:51Harley-Davidson's early this early that
00:04:54with atmospheric intakes
00:04:57Instead of a cam operating the intake valve. They just let the atmosphere push on it was a kind of like a
00:05:03reed valve, which is self-operating
00:05:07And
00:05:08around
00:05:111903
00:05:131903
00:05:15car manufacturers began to operate the intake valve from a cam as well and
00:05:20So the basic engine had two valves an intake and an exhaust
00:05:26They were each operated by a camshaft and they were given timings that were obvious
00:05:31that is the intake valve open at top dead center or began to open a top dead center and
00:05:39Was fully open somewhere in the middle of the stroke and began to close
00:05:45Thereafter and at bottom dead center. It was closed. So the compression could begin these engines operated at
00:05:52quite moderate rpm
00:05:541,500 for for a car engine in the early days, so
00:06:00Cam timing was no big deal
00:06:03but then at Brooklyn's and other places people who were
00:06:07Playing with these engines. What if I do this? What if I do? Let's try the other thing
00:06:13they discovered the value of
00:06:17Opening and closing the valves at other times. They said well
00:06:21The piston is at maximum downward velocity at 76 degrees after top
00:06:27Shouldn't the valve be more open at that point?
00:06:31maybe we should start opening it before top dead center and
00:06:35And
00:06:37When considering the exhaust stroke here comes the piston it's pushing out the
00:06:43residual hot combustion gas and
00:06:46as
00:06:47It's reaching top dead center. The valve is nearly closed. So that last bit of gas is kind of
00:06:53whistling out there
00:06:55Maybe we should close the exhausts
00:06:57Later after top dead center and they also discovered
00:07:02George
00:07:04Bouton discovered they could make their engine one of their engines turned as high as 4,000 revolutions
00:07:11They began to discover that you could increase power
00:07:16By delaying the closure of the intake valve past bottom dead center, and we've talked about this in other podcasts
00:07:23But what's going on basically is by the time the piston is nearing the end of the suction stroke
00:07:31The air and the intake port is moving along at a good clip
00:07:35And it would be a shame to stop that rapid motion by closing the valve at bottom dead center
00:07:41So we leave the intake valve or valves open after bottom center dead center to allow that intake momentum
00:07:49to keep coasting into the cylinder and
00:07:53completing its filling
00:07:55The more stuff you've got in the cylinder the higher the combustion pressure will be and the greater the
00:08:01Yank on the rear tire
00:08:03so
00:08:04Little by little and through the efforts not of engineers with degrees but of practical people
00:08:11Trying things at places like Brooklyn's the great Speedway in England that was built in
00:08:18What 19 oh?
00:08:2019 well
00:08:22very shortly after 1900
00:08:26A
00:08:27Great deal was learned and British motorcycle manufacturers would hire these specialist tuners
00:08:36to give their new models
00:08:38Greater power than they would get if they were designed according to the simple-minded ideas of the time
00:08:45so
00:08:46those
00:08:47speedmen
00:08:49were
00:08:51the itinerant engineers of their time and you would find that
00:08:55Progressive manufacturers would employ one or more of these men and they would go from company to company
00:09:02Building a little extra excitement into their products well Jim fueling did that in modern times didn't he he sure did you know
00:09:11And I have to hats off to anyone who has a tank collection
00:09:18That's
00:09:20That's pretty esoteric yeah ship it to me how
00:09:24No, we're not driving it out there. Yeah
00:09:28so
00:09:32The problem in the early days of course was that exhaust gas is hot and
00:09:37an ordinary steel
00:09:39exhaust valve
00:09:41quickly corroded away and stopped sealing
00:09:45So that early day cars had to have their valves ground
00:09:51Every few hours of operation and that was one of the duties of a chauffeur
00:09:55Very often the garage of a wealthy family
00:10:00would have several bays for their automobiles and the chauffeur and his family would live upstairs and
00:10:07And the chauffeur would be busy in the afternoon or whenever not otherwise engaged
00:10:13grinding the valves on whichever car
00:10:17he had reason to believe the master would want next and
00:10:24People tore their hair over this problem they they made
00:10:28exhaust valves in two pieces with the steel stem and
00:10:32A cast-iron head. Well, they make stoves out of cast-iron. It's a good worth a try and
00:10:39I should say
00:10:41What this type of valve was this is the poppet valve a poppet valve is like a miniature
00:10:50Manhole cover that we drive over in town
00:10:53so many times in a car with a
00:10:57Stick coming out of one
00:10:59face of it
00:11:01that is in one piece with it and
00:11:04this valve is
00:11:06Seats against a conical seat in the cylinder head typically cut at 45 degree cone angle
00:11:13so it's self-centering and
00:11:16the valve stem is
00:11:19in the intake port passes out through the wall of the intake port and goes up into the
00:11:25Lubricated space or down in the case of a flathead and there is a valve spring and
00:11:33Fixings on the end of the valve stem to attach it. The spring is there to hold the valve closed against its seat
00:11:41now one of the great things about the poppet valve is that when the high-pressure part of the
00:11:48cycle occurs the valve is motionless and the pressure of
00:11:53Combustion is holding it tightly against its seat so it can't leak
00:11:58It is also valuable that it holds it tightly against the seat in order that
00:12:03The heat of the exhaust valve can be lost
00:12:07Into the cylinder head and the exhaust valve
00:12:10Therefore runs cooler than it otherwise would
00:12:15Well
00:12:17Frederick Lanchester, who's a
00:12:20Definitely worth anyone's while to look up some of the
00:12:23wonderful
00:12:24Flood of ideas that this person brought to light from his from his forehead
00:12:32He decided let's make the the valve system self-cooling
00:12:38so he had one valve in the cylinder head and
00:12:41In the pipe leading away was a diverter
00:12:45So that it was a Y pipe and the diverter could connect the single valve to either
00:12:52leg of the Y
00:12:55So what would happen is the diverter would connect to the intake
00:13:00the valve would open the piston would descend on the suction stroke and cool fresh charge would be drawn in and
00:13:09Then
00:13:11Compression and combustion would occur and at the end of combustion
00:13:15the one valve would act as an exhaust valve and
00:13:19The diverter would send that gas to the exhaust pipe
00:13:24So in this way the fresh charge coming in cooled
00:13:28The valve which had just been heated by the last hot exhaust gas going out
00:13:35It's one way to get no overlap
00:13:37Absolutely true so but it was it was a
00:13:45It was an artifact of the fragility the thermal fragility of exhaust valve materials and
00:13:53fortunately
00:13:56Everybody scrambled around like mad. Well, let's try this. Let's try that
00:13:59One of the first ones is tungsten steel because around 1900
00:14:04Machine shops began using so-called high-speed steel, which was alloys with tungsten and
00:14:11It was as hot as
00:14:13as sharp as when it was red hot and as hard as when cold and
00:14:20so
00:14:21It seemed like that might make a great exhaust valve pretty good take electrode. Yep, so
00:14:29Tungsten steel was enjoyed a bit of a vogue and then
00:14:34In the 1920s sometime they came across
00:14:38They began to make stainless steels
00:14:41they were originally they came into being because people didn't want the bores of
00:14:47Military rifles to corrode with with all the corrosive black powder that they were shooting
00:14:54so
00:14:56Still even with stainless valves intakes
00:15:00Were ran cool exhaust valves ran
00:15:04Dangerously hot so one of the other solutions that came up was they said well
00:15:11Let's make two
00:15:13Smaller exhaust valves each of them will have a shorter heat path from the hot center of the valve to the cool
00:15:21valve seat area
00:15:24So
00:15:26Mainly for this reason
00:15:29early engines such as
00:15:31Aircraft engines of World War one 1914 to 1918 had four valves and
00:15:42Then along came
00:15:46Harry Westlake in the 1920s he bought three
00:15:52Sun beams, I think and
00:15:54He dino'd them and one made 25 horsepower one made
00:15:5926 horsepower and the third one made 29 horsepower
00:16:05Well, why can't they all make 29 horsepower?
00:16:09so he built a
00:16:11crude flow meter for himself and he discovered that he was right in his first assumption that
00:16:20The airflow was different in the three engines
00:16:23So he looked at the ports and he realized that there was
00:16:26Some
00:16:29Of them were a mess because the casting process wasn't terribly refined and
00:16:33Others just happened to come through looking a bit more smooth
00:16:38so he thought let's
00:16:41See how far we can go with this process of improvement and he and others coming after him
00:16:48all these airflow people with their
00:16:53Wonderful flow benches
00:16:55Were able to try out an idea as soon as they had it basically you would
00:17:02Do a port on an engine and walk over to the flow bench when you where you had it configured so that you could
00:17:09bolt the cylinder head on
00:17:11Set the valve at a particular lift
00:17:14That would enable you to compare it with yesterday's experiment the day before and the day before that
00:17:19very quickly
00:17:21People developed a useful body of information and
00:17:29That work goes on today
00:17:32Except that we humans who are so easily bored and want a fresh peak experience every moment
00:17:40Think how discouraging it is to to come up with a wonderful flowing intake port. It is so fine and
00:17:48then realize
00:17:50This engine has eight cylinders. Now. I have to make seven just like it and I don't want to I don't want to
00:17:58Well, I've made custom carburetor needles and and doing one carburetor needle custom is a lot different than trying to make another one
00:18:05Exactly the same it is
00:18:07Yeah
00:18:08So fortunately today, of course we have CNC
00:18:13computer numerical control
00:18:16machining and
00:18:18They can digitize the beautiful port that our artist airflow expert has created
00:18:25And then all the other seven will be the same
00:18:31So
00:18:33Nobody wants to get
00:18:35repetitive brain injury
00:18:38They have those machines in the KTM race shop, it's amazing. Yes. Yeah in the work. Sure
00:18:45so
00:18:47Now let's consider how the valve should be arranged on an engine
00:18:55it was it was clear in the early days that
00:19:00There would be advantages to putting the valves above the piston with their stems up and
00:19:06Their heads facing the combustion chamber because this would allow a port to come
00:19:11Right to the valve seat
00:19:14Fairly
00:19:16Directly and the flow would be good
00:19:19but there were important reasons for building side valve engines which had that the two valves and
00:19:26Some engines had four some engines had six side valves on both sides of the cylinder. Everything's been tried
00:19:34but the side valve
00:19:37The air has to go up to the valve because it's sitting next to the cylinder with its stem down and its head up
00:19:44It has to make the turn to come out of the valve
00:19:48go across the valve chamber and turn down into the cylinder of the engine and
00:19:54the same thing
00:19:56retracing its steps on the
00:19:58leaving the cylinders exhaust gas
00:20:01but
00:20:03The side valve engine had a tremendous advantage because it was very easy to give it combustion squish
00:20:09You could make part of the cylinder head come very close to the top of the piston which was flat
00:20:16So that as the piston rose to top dead center the trapped mixture between those two surfaces would be
00:20:24squished out
00:20:26into the valve chamber
00:20:29Where it would create whirling turbulence so that when the spark occurred the light up would be rapid and
00:20:36Rapid light up was very important in those days when gasoline was dreadful. It not so easily I used to
00:20:45To hold the can up to my ear and say I hear you knocking
00:20:54Ricardo made a buck
00:20:56On side valve. Yes, sir. The squished side valve Harry Ricardo was an English
00:21:04engine pioneer and
00:21:06of course
00:21:08We everything we do to stay alive is called business
00:21:14And he sold the concept to Harley-Davidson he sold it to everybody
00:21:20But what this did was it fixed it so that Indian flatheads
00:21:26Could quite often beat eight valve Indian and Harley-Davidson
00:21:33Factory racers and I think the reason for this was
00:21:38That they accelerated well
00:21:41With the overhead valves
00:21:45At low speed if you were to open the throttle and if you were to give this thing a fair amount of compression
00:21:50you'd hear it knocking and
00:21:53It would shortly destroy the piston ring seal by hammering the top piston ring lounge down
00:21:59Land down onto the ring and trapping it
00:22:03so I think that
00:22:06Charles Franklin at Indian was able to run more compression in his side valve squish engines
00:22:15Then the eight valve overhead people could in their open chamber engines
00:22:22Because there was no way to have squish at a compression ratio of four to one
00:22:28So flatheads had a reputation for good low speed pulling power
00:22:33Without knocking and they persisted for years and Harley-Davidson
00:22:38came and and won Daytona and in 68 and 69 with a
00:22:45750 flathead engine that was making
00:22:4758 horsepower and
00:22:49What that did was it chased the 500 triumph that had won
00:22:54in 66 and 67 just take those take those things away and put them in a museum someplace because
00:23:02they were
00:23:03They were hard-working little 500s and they just couldn't do any any more
00:23:10so
00:23:11The flathead as a principle
00:23:14Lots and lots of car engines were built as flatheads
00:23:18Okay, put that aside now
00:23:21The overhead valve engine is the one with the valves above directly above the piston
00:23:26so the flow don't doesn't have to go through round a lot of corners and
00:23:33The problem with it was the prototypes were encouraging
00:23:39Because they only had to last long enough for a dyno run
00:23:42But what did you do when you've got this these exposed rocker arms and push rods?
00:23:47rattling around on this engine
00:23:50unlubricated
00:23:51It would take years before all that stuff was enclosed and lubricated and it became a normal
00:23:59way to design engines
00:24:01whereas a side valve the cam and the
00:24:05The
00:24:06Followers that operated the valves were down at crankshaft level where they were getting oil thrown on them
00:24:12All the while so it was a great way a money-saving way a simplifying way to build engines
00:24:19And they built lots of flatheads or side valves as the British called them
00:24:25But eventually people accepted the overhead valve. The performance is is good
00:24:32but
00:24:34They had to overcome problems of knock and what-have-you
00:24:39and
00:24:41So the the four valve era
00:24:44after World War one sort of died out
00:24:47because
00:24:48The Italians at Fiat discovered that two valves
00:24:53Set not parallel stems, but swung apart
00:24:58more than 90 degrees
00:25:00Now you had a larger space in which to fit large valves and
00:25:09That became
00:25:11an overnight success Fiat won a lot of Grand Prix races with their
00:25:16with their two valve Grand Prix engines and
00:25:23Everybody suddenly was doing two valves and the
00:25:27in fact the
00:25:29predecessor of all
00:25:32Transverse inline four motorcycle engines was being prototyped by a couple of engineering students
00:25:41In Italy and
00:25:44They were I'm sure impressed with Fiat's accomplishment. They gave their engine two valves
00:25:50So when Grand Prix racing began again after World War two
00:25:54The FIM got its act under control and they began the series in 1949
00:26:01The Jalera was two valve the Norton was two valve all those racing engines of that classic period were two valve engines
00:26:10And the airflow people were discovering
00:26:14that a
00:26:16hemi chamber
00:26:17With a single intake valve in it had a very it it was
00:26:23Very flow enhancing and if you talk to airflow guys
00:26:28They will say to you one of the most neglected
00:26:32Possibly well the most neglected area of airflow is downstream from the valve
00:26:39When the air leaves the valve what happens to it
00:26:45Any of you who have flow benches can can reproduce this experiment you put
00:26:50A head on there with an exhaust valve lifted
00:26:55blowing
00:26:57Out through the exhaust valve and you
00:27:01twist all your dials you set your pressure and you look at your flow meter and you convert it to
00:27:07cubic feet per minute and you find
00:27:11X and
00:27:14It's making a funny roaring noise
00:27:17So you take a piece of paper
00:27:21And roll it up
00:27:27Into a cone and
00:27:29you stick the
00:27:31Small end of the cone into the exhaust port the roar goes away the flow goes way up
00:27:38What's going on?
00:27:40and
00:27:42Then you realize what's going on is
00:27:44That
00:27:47When the air rushes out of the port and runs into the atmosphere in the room
00:27:54Everything is dissipated as turbulence, but when you put a conical
00:28:00Pipe on there it slows the air down gradually and
00:28:06Converts it efficiently back into pressure, which is what you want to fill your cylinder for example
00:28:11So on the intake side what's happening is the air emerges out from under the valve and
00:28:18In a hemi chamber the chamber is is curving abruptly
00:28:23to it to in
00:28:26encase the valve
00:28:27the airflow attaches to the inside surface of the head just like it was half of a
00:28:33Of a diffuser a cone slows it down
00:28:37Converts it efficiently into pressure and the airflow
00:28:41Goes up
00:28:44And
00:28:45so
00:28:47This was used as a reason not to have four valve engines. Oh, they're inefficient. They they're
00:28:53specific flow
00:28:55cubic feet per minute per square inch of valve head area is
00:29:00bad
00:29:02One intake valve very good
00:29:06But then
00:29:08There's always something happening to spoil the beautiful picture that we humans create
00:29:15What happened was
00:29:17They would decide
00:29:19Those people who are racing single-cylinder engines in the for example the Isle of Man TT in the 1920s and 30s
00:29:29Our engine is out running its intake flow. We need a bigger intake valve. Well, there isn't room in the head
00:29:35Okay, let's increase the bore and shorten the stroke and they did this in very
00:29:42Conservative small steps so there wasn't easy for the pattern to appear. What's really happening here?
00:29:50but performance kept
00:29:55Increasing in little steps until finally
00:29:59One of the it sort of reached ahead in in a four-cylinder
00:30:06Grand Prix car engine that was built by BRM in Britain
00:30:10I think was the Stuart Trezillion design and had these monster valves in it and the valves kept breaking
00:30:20Well on the other side of the world
00:30:24The Honda was desperately trying to win the
00:30:29Giant volcano race, which was very important within their industry and it took place on
00:30:37cinder
00:30:38surfaced roads
00:30:40and
00:30:42Yamaha and Suzuki were winning all kinds of stuff and Honda couldn't seem to get a foothold
00:30:47So
00:30:50They designed this wonderful transverse four-cylinder engine and
00:30:59They found that on that loose surface, it was very easy to over rev it
00:31:05and
00:31:07When they studied this matter
00:31:08They found out that some of the MV's that were racing in Grand Prix's at that time two valve MV's
00:31:16Had only 300 rpm between peak power and valve float
00:31:23now that sounds like a bad deal if you're racing on a cinder surface because
00:31:30Suspension was primitive in those days. What if you hit a bump?
00:31:36The engine is going to spike in rpm the valves will float
00:31:41They will collide with the piston and all will be a disaster
00:31:46So the Honda people not for reasons of airflow, but for reasons of mechanical reliability
00:31:54Decided to try four valves
00:31:56four little valves instead of two bigger ones and
00:32:02For equal area the the smaller valve is about
00:32:0770% of the diameter of the single large valve and they found that these smaller valves were easier to control
00:32:15Mechanically, it was easier to get enough spring in there
00:32:19Without stretching the valve stem or cupping the valve head of cupping was big on exhaust valves
00:32:29They made this four valve concept work
00:32:32But there were those in the West who said oh, well these people are years behind the times
00:32:38They're still doing it the way we did it in World War one. Ha ha ha
00:32:43well
00:32:45Not only did Honda succeed in winning the Volcano race
00:32:51Mr. Honda had announced in 1954 that he was going to go racing
00:32:56And he made a trip to Europe and he was terribly discouraged
00:33:00He was terribly discouraged to discover that his products were only about making about a third of the power of
00:33:07Top European equipment
00:33:10but they kept at it and they spent R&D money much like they're doing a KTM now and
00:33:18when they
00:33:20Came to the Alamann in 1959 with a team of 125 twins
00:33:27They practiced early in the week with two valve engines and then the four valve engines
00:33:32Which were furiously being finished in Japan were flown in
00:33:37Maybe it was Kintetsu Air Service. Who knows but the four valve thing was
00:33:43successful because
00:33:45the way you make
00:33:47Serious horsepower from little engines is to rev the daylights out of them so that you perform the power
00:33:55producing cycle more times per second and
00:34:01They they cleaned house
00:34:06Yamaha and Suzuki had their innings but
00:34:10Honda won so many Grand Prix championships in 50 cc
00:34:16125 250 and 350
00:34:19They crushed them in 350. Nobody people just said that's a lost class that belongs to Honda now give up and
00:34:28Suddenly people were reconsidering the four valve idea. Well now we know that
00:34:36Yamaha with their five valve Genesis engine and
00:34:41Ferrari played with five valves. I think Audi did too
00:34:44Why did they do that? Why did they think more valves would be better yet?
00:34:52Some engines were built with eight in one cylinder. I'm not talking about the NR 500. I'm talking about round piston engines with
00:35:01all kinds of valves
00:35:03well
00:35:05These things
00:35:09When a valve opens
00:35:14The area of flow that it presents is the distance around the valve its circumference
00:35:22Multiplied times its lift and
00:35:25for obvious reasons they called this curtain area because you imagine this flow area as a as a
00:35:32cylinder and
00:35:35Curtain area is produced at a certain rate by
00:35:39You know each millimeter of lift gives you so much with a single big valve
00:35:44But there's a 40% increase if you go to two valves
00:35:49What does that buy us?
00:35:51What it buys us is
00:35:54Two intake valves expose flow area 40% faster than one valve of the same area and
00:36:04That means we can use shorter valve timing because the valve is open sooner
00:36:10The valve is flowing a lot of air sooner than the single valve
00:36:15This is the curtain area argument and this is what led to the five valve Genesis
00:36:20and I think there was a six valve single and
00:36:24Engines with all numbers of valves have been tried
00:36:28well, I
00:36:30Have a big old black book in which it describes the experiments that were conducted in England during World War one by
00:36:39AH Gibson and
00:36:42Gibson
00:36:43Wanted to try everything so they'd be sure that what they had was the best possible
00:36:50and one of the conclusions that he drew as a result of these experiments is
00:36:56especially in an air-cooled engine
00:36:59The more holes you make in the cylinder head the more trouble you will have with distortion and cracking
00:37:08so when
00:37:11Ferrari's five valve prototype
00:37:14Endurance racer pulled in to the first gas stop and they did everything the air wrenches rattled and the fuel gurgled
00:37:22Engine wouldn't start
00:37:25They could not resume racing because they had no compression
00:37:31And this also tells us why Harley Davidson
00:37:36for
00:37:371200 Sportster
00:37:39Decided to circulate
00:37:41oil in
00:37:43passages in the air-cooled cylinder head
00:37:46That were closely adjacent to the exhaust valve seat
00:37:52Because in that engine if you ran it good and hard
00:37:58The valve seat area would
00:38:03Become distorted by heat so that seal would be lost
00:38:09and
00:38:11this of course was
00:38:14unacceptable and
00:38:15When people tried to build four valve air-cooled engines
00:38:20they had the same problem that valve seats moved around or they came loose and
00:38:27Rattled around like a like a collar
00:38:30and
00:38:32What Honda did about this is the same thing that?
00:38:35Norton did up until 1950 with their racer. They cast a
00:38:41Spectacles insert for the cylinder head that had the holes for the valves the seats for the valves and the threaded
00:38:48Holes for the spark plug or skulls. I just want to point out. I'm still here. I'm here
00:38:54We're gonna you bet and thank you for a skull because that's what just what they called it
00:38:59Honda used austenitic iron, I think quite a bit and I think
00:39:04Norton used bronze
00:39:06but that was one approach and when Harley
00:39:12Started liquid cooling the valve seat area of 1200 sportster
00:39:17They were starting something that has has not
00:39:22finished yet
00:39:23Because this has allowed the traditional and well-loved
00:39:30Covered with fins
00:39:33classical Harley engines to continue thumping along in history
00:39:39Because they now have liquid cooling systems
00:39:42To cool the valve seat area well enough that they could adopt four valves per cylinder in the Milwaukee eight
00:39:50now
00:39:52When those Vincent racing fellows down in
00:39:57in Australia
00:39:59Built their first four valve Vincent. They had all these troubles and
00:40:04They adopted a skull construction and it worked for them
00:40:10But
00:40:12Far better to take away the heat before it
00:40:16starts getting out of control because
00:40:19many an engine with skull construction the
00:40:22Aluminum cast over the skull has come loose. Oh
00:40:28Now my engine is spoiled
00:40:32So
00:40:33Better to take away the heat and this is why four valve engines were so easily
00:40:39Successful in liquid cooled form but have required what they call now topical cooling
00:40:46to keep the
00:40:48valve see exhaust valve seats from
00:40:52Deforming or the area between them exhaust air between them exhaust bridge cracking
00:40:58Exhaust bridge cracking is a terrible one because now let's imagine
00:41:03An engine that has two exhaust valve seats. It's a four valve engine and
00:41:08the narrow space between the valve seats when the engine
00:41:14Gets hot everything expands and
00:41:17The expansion pulls on that area and stretches it and
00:41:24Then when it all cools it comes under compression
00:41:29Do enough cycles and you have a crack?
00:41:32and
00:41:34The problem here is called creep, which is
00:41:38slow yielding of metal at
00:41:41far below typically 50% or so of the melting point and
00:41:46It was a terrible problem for
00:41:49the r-33 50
00:41:52radial engines on b-29 stirring during the Pacific War
00:41:57They had this these were two valve engines. They met a H Gibson's criteria
00:42:05but they weren't cooled adequately and they they had all kinds of
00:42:10Distortion leakage and engine wrecks so
00:42:16it's all under control now and
00:42:18we're we're able to
00:42:20move forward with confidence in
00:42:23designing new stuff because they're
00:42:26Not only can we make high-performance four valves
00:42:30Which was the essence of the sport bike era?
00:42:33but when they put four valves into Milwaukee eight and into the
00:42:402018 Goldwing
00:42:42They found that the curtain area effect allowed them to move torque powerful torque
00:42:51into the low-speed area without sacrificing performance on top
00:42:56So that they were given those flat torque curves that everyone liked so much and if you're going to ride an eight or nine
00:43:04hundred pound motorcycle
00:43:06Not only do you like it the torque but you need it to get that thing moving without going
00:43:13and
00:43:14having suffering
00:43:16embarrassment
00:43:19So
00:43:21All this all this from from valve construction
00:43:25And of course if you read the fine print you find out that
00:43:30When Honda was building their winning air-cooled
00:43:33Four valve racers in the 1960s and winning all those Grand Prix's
00:43:38They were using exhaust valve materials that were developed in Britain
00:43:44for gas turbine engines
00:43:47They were using
00:43:50Mnemonic 80a
00:43:53Which was one of the first successful gas turbine alloys and then later they adopted
00:43:58Mnemonic 90 which was the next step in
00:44:02Temperature durability
00:44:05so
00:44:07Information and innovation gets around when you have it when you have a terrible need
00:44:14To exhaust valves per cylinder in an air-cooled engine that's running at very high temperature is a severe application
00:44:24You will sooner or later find oh this mnemonic 90 looks pretty attractive. Let's phone them up
00:44:32So
00:44:33Why don't we have exhaust valve trouble today?
00:44:37excellent exhaust valve materials well-cooled cylinder heads typically water-cooled or
00:44:44topically cooled
00:44:46That's what those two bathroom heaters are on certain
00:44:51Long-distance Harleys they're heat exchangers for getting rid of the
00:44:56Heat that's extracted by liquid from around
00:45:00One of the things you pointed one of the things you pointed out about cooling valves with oil
00:45:06Indicates well, it's
00:45:09It pushes the problem elsewhere, you know, I hopped up my Leverta years ago
00:45:14I put a big pipe on it and rejetted it and I went from 50 horsepower to 69 horsepower on the Cycleworld dyno and
00:45:21What happened next the clutch started slipping?
00:45:25That's so you're talking about cooling the exhaust valve with oil and then
00:45:29If it gets hot you can get coking and you can plug up those little holes
00:45:33Yes, and it's just it's a constant constant battle with problems and solutions now what I want to talk about
00:45:40So we've been spent a lot of time on on valves and we spent a lot of time
00:45:45On that aspect of airflow and flatheads and heat transfer through the seats and all those things
00:45:53But there's a tremendous amount of magic going on in
00:45:57Springs and
00:46:00Particularly in camshaft in ramp and opening the valve getting it to open rapidly
00:46:06without setting the spring into vibration or
00:46:09Setting up so momentum so much momentum that the valve throws off of the cam and is then floating
00:46:17Yes, so if you think about a pushrod engine you have a very long pushrod that has mass you can make it out of
00:46:23titanium you can do all these other things but it's still there and then you have a rocker and if it's if it's if
00:46:29It's like on a BMW or the you know
00:46:31An r75 slash 5 where the cams underneath the crankshaft and the pushrod is very long
00:46:36Like you got to find some solutions there
00:46:39Yes, that's right to avoid valve float and that's you know
00:46:42Advantage of an overhead cam is that there is no pushrod
00:46:46you've taken that mass out of the system and you have you can have a light bucket or you have a bucket under the shim a
00:46:52Bucket over the shim or you can go to the ultimate solution of finger follower, which reduces the mass even more
00:46:58Let's talk about I mean, I think I think you know lift ramp
00:47:03That kind of thing is okay when
00:47:07The first thing you find when you when you put valves into a machine like this is that there has to be a clearance
00:47:14between the driving force the camshaft and
00:47:18The valve or tap it and the reason is that when the engine?
00:47:24Starts and begins to warm up. The valve gets longer and
00:47:31So it would
00:47:33Leak even when it was supposed to be closed
00:47:37So there has to be enough clearance to allow that expansion of the valves as the engine warms up
00:47:43but
00:47:46So that it doesn't touch the camshaft and stay open even
00:47:51Even five pounds less than what the spring seat pressure and all that stuff is supposed to be doing even fractionally
00:47:58Because it's important that the combustion pressure press the seat
00:48:04The valve against the seat not press the valve against the cam lobe. Yes, so
00:48:10It's normal to have a clearance and it may be just a few thousands like three or four or five
00:48:17In in very tall engines. It could be a bunch more
00:48:21but
00:48:22It makes a clicking noise when the cam lobe comes around and takes up that clearance
00:48:28and
00:48:30people didn't necessarily like the clicking and
00:48:34Impacts are bad for machinery. So they adopted what's called a clearance ramp, which is a
00:48:42region on the round part of the cam
00:48:45that is
00:48:48It has a very slow lift so it takes up the clearance gradually
00:48:54So there's no click and
00:48:57Then the lift of the valve can can begin
00:49:03And in the early days when engines were turning 1,200 or 1,500 rpm
00:49:08You could get away with any just about any cam contour you cared to freehand. Oh, this one looks nice
00:49:14I'm gonna make this purple
00:49:17so
00:49:19Engines just kept turning faster as people extracted more power from them and
00:49:24And
00:49:25trouble
00:49:26began
00:49:27valves
00:49:29might break
00:49:30Springs broke often. There's a lovely little book about early days racing at Brooklyn's and it lists all the failures
00:49:38and I went through that book once and found that
00:49:42valve spring and exhaust valve failures were the the biggies
00:49:48So
00:49:50The usual response was well, we're we're floating the valves and and it's destroying our top-end power and
00:49:58What are we going to do we'll put bigger springs in it, okay, that's a good idea
00:50:03So overpower the problem with big springs
00:50:07But the problem is that it's very easy to wipe out tappets by making
00:50:13requiring them to compress
00:50:16humongous springs
00:50:19So there's some limit to how much spring you can put in there so at one point
00:50:24somebody from the
00:50:26California the West Coast scene went to see an engineer who lived up north
00:50:33Somebody with a engineering degree and said look we're having all these problems
00:50:40Can you help us with this
00:50:43And so the guy said let's graph this cam out so they they graphed the valve lift
00:50:49Versus the crankshaft angle and they got a a nice curve that looked pretty okay
00:50:56Now, let's convert this
00:50:59graph of valve position into valve
00:51:04velocity
00:51:05And you do that by graphing
00:51:08The slope as it changes up the profile
00:51:13The slope of change of position is velocity
00:51:19Then you get the velocity curve
00:51:22and
00:51:23Then you do the same thing with the velocity curve to get the acceleration curve
00:51:27And when they did that they saw that this cam profile was asking the valve to accept infinite
00:51:35acceleration
00:51:36Which is the same thing trying to try to push start another car by backing up
00:51:44400 feet and
00:51:46Hitting the other car at 40 miles an hour
00:51:49The cars don't take to it
00:51:52So so
00:51:55The degreed engineer was some use because he was accustomed
00:52:00To an analytical method rather than a an instinctive method plus bigger valve springs
00:52:07And that partnership persists to this day
00:52:09I remember reading about one of the NASCAR teams that phoned up the parent company in Detroit and said you got to help us man
00:52:18Just like the guy I was describing was part of that
00:52:22Race car scene in the 1920s. So Detroit sent them a
00:52:29Brilliant Sino-american
00:52:34Applied math graduate
00:52:36And he went down to to good old boy country
00:52:41probably Statesville and
00:52:45He he graphed all that stuff and
00:52:48He made recommendations. He worked with the cam grinders and they came up with
00:52:54another 300 rpm without valve float without ill effects on the spring
00:53:01gold
00:53:02Cam profile gold. Yes, I think you know, there's a guy named Billy Godbold who does work at comp comp cams
00:53:11and comp cams, you know, it's a
00:53:13V8 company. I mean they do other stuff, but it's all like push rods and money is yep. Yeah, and
00:53:20They just keep getting rpm. They're just doing incredible things and he's a you know rocket scientist
00:53:26He's one of these guys who was you know, I think in aerospace and but he's a he's a hot rod guy
00:53:31I think he has a
00:53:33BMW like an m3 or a 3-series that he has road racing and I'm sure he's done cams for that, but
00:53:40point is it's
00:53:42It's these fine these beautiful tiny little
00:53:45fine
00:53:47contours and measurements
00:53:49fractions fractions of an inch
00:53:51that are taking up the space between the head of the valve and the cam and
00:53:56Getting the momentum to start in a short period of time but without an impact and then
00:54:03It all has to be gradual without exciting the valve and then you know, you're you're talking about how do you control valve vibrations?
00:54:11You know, it can be the thickness of the material
00:54:13Of course, you can use your fabled vacuum remelt steel and you can change you can improve the material to
00:54:20astronomically high levels
00:54:22But you still have yeah, but you still have to keep it from vibrating and that's what you know
00:54:27Dual springs where they would nest the strings a small coil
00:54:30This was this was another big thread in valve train development, which was
00:54:38When they first used the strobe
00:54:41to observe
00:54:43valve action and what they saw
00:54:46Was basically what people in the 1950s who had those first slinkies the child's toy
00:54:53that's a spring of many turns and
00:54:57You can have somebody stand 10 feet away and hold one end and hold the other end yourself and you could pluck
00:55:03at the coils and see
00:55:06the wave travel along to the other person bounce off and come
00:55:12Back to you and it would keep reflecting like that
00:55:15well
00:55:16the desired effect in your valve train that you want to see each not only does this cause a
00:55:22Very an unnaturally rapid accumulation of fatigue cycles leading to failure
00:55:29but it also
00:55:31Causes a variation in the spring pressure that's available to hold the valve against the cam contour
00:55:39So if there's a wave going away just at the point where the
00:55:46Acceleration of the valve upward is
00:55:49Becomes deceleration as it slows down to go over the nose and start closing again
00:55:56It could lead to float that wouldn't occur. Otherwise
00:56:01so
00:56:04They wanted to stop those extra oscillations that were going on and one way to stop them is
00:56:11to avoid wherever possible
00:56:14impact like
00:56:16Driving forces acting on the valve train because
00:56:20They will cause high frequency motion in the spring coils. Lots of fatigue cycles early failure
00:56:28The world is there they're probably barrels full of
00:56:32Rusty old cams. Hey, what are these cams in the corner over here?
00:56:36Oh, they made some of those things made really respectable power, but they broke valve springs
00:56:43so
00:56:45What about them? So nothing about them. They broke valve springs. That's all end of story
00:56:51so they have they they decided they wanted to
00:56:55Stop those unwanted oscillations so that the valve spring would just
00:57:00Smoothly compress and expand without traveling waves bouncing from one end to the other like in the slinky
00:57:07So one approach was to wind a flat
00:57:11coil and
00:57:13Fit it inside the spring so it rubbed on the spring. It was a friction damper
00:57:19Another approach was to if you're using two valve springs
00:57:23you would make them an interference fit with one another and wound in the opposite direction so that
00:57:29They crudely rubbed on each other to create a damping force. That would sort of was like that bell is too loud
00:57:37So will somebody sit on it?
00:57:39and
00:57:42All these variations still exist and recently something
00:57:46Probably clever was added namely the beehive spring he hives. Oh
00:57:53because if you play with the equations, which are readily available for
00:58:01That govern how much pressure a spring of this diameter wire with this many turns this long and so forth
00:58:08It's all very tedious. It's it's just like
00:58:12Like building a house, you know, we've got some boards and we've got some nails and we'll just keep going until we're done
00:58:19But
00:58:21Every valve spring has a natural frequency
00:58:26If you like the slinky you pluck it and you
00:58:30You count off 10 seconds and count the cycles and that's its frequency in cycles per minute
00:58:37and
00:58:39One of the early innovations was to raise the frequent natural frequency of the spring
00:58:46by having so few coils
00:58:50That the natural frequency was above
00:58:53The frequencies that were going to excite the spring
00:58:57And that's when you need your very nice material very nice material and S&W spring
00:59:04were pioneers in this kind of thing because they combined
00:59:09the three-and-a-half turn spring
00:59:12with vacuum remelted spring wire and
00:59:17shot peened spring wire because if you think of it the maximum stress a
00:59:22coil spring is just a
00:59:25torsion bar that you have
00:59:28wound up so you're twisting the wire and
00:59:32The part of the wire that is under the greatest stress is at the surface
00:59:38So that's why shot peening was essential to prevent
00:59:43Cracking and failure because of the surface is the part that is carrying the greatest stress
00:59:50That's a terrible thing. Yep
00:59:52shot peening is is just continually hammering in very small increments the exterior of the spring and
01:00:00Putting it into compression putting it into compression so that resists coming apart better
01:00:05Because cracking requires tension if you have pre-existing
01:00:11Compression you can have to bend the thing further before you reach a given level of tension
01:00:16So that's why you want your shot peened rods and it's a you know
01:00:20People love those polished rods all those World War two aircraft engines had beautiful polished rods
01:00:26People love to chrome them and put clocks into them
01:00:30But
01:00:33Along came the shot peening. Yeah, we love those polished rods, but they're junk now we shot peen everything and
01:00:42That was the SNW people were an instant success Porsche bought their Springs
01:00:49BSA was putting them into gold stars. It was it was wonderful. It was a real transformation and
01:00:55That was a marriage. Yeah, go ahead
01:00:59of a of a
01:01:03Sort of military technology vacuum remelt
01:01:09Sort of flowered in the US in 1953 and I think it's a basically a German invention
01:01:18Lots of stuff now is vacuum remelt the landing gear on 747s
01:01:24Which have just gone out of production is
01:01:27300 M which is a good old crankshaft and connecting rods steel
01:01:324340 in vacuum remelted form when you when you
01:01:37use
01:01:38remelt material in a vacuum you allow many kinds of
01:01:44Impurities in the material to evaporate and they are pumped away by the vacuum system. Goodbye. Go away
01:01:51no more trouble again and
01:01:54Those
01:01:57Materials are are finding wide use in all sorts of high-stress applications such as rolling element bearings
01:02:07So the beehive spring
01:02:10Doesn't have a natural frequency because its coils
01:02:14Its coil diameter decreases towards one end and of course that end is stiffer than the end that has larger coils
01:02:23So the the wave is trying to bounce back and forth in proper slinky fashion
01:02:29and the different parts of the spring are saying oh
01:02:34Your your money's no good here, man. You don't excite me. Yeah
01:02:39and so a
01:02:41Lot of engines are now using a single
01:02:45beehive spring in place of
01:02:47Nested springs with friction dampers and all this other business
01:02:53And
01:02:54Once upon a time I was walking along the back of the garages at Valencia
01:03:00thinking about dinner and a door opened and light splashed out and
01:03:06There was Stuart Shenton and he said oh, it's you. Do you want to come in here?
01:03:12He was working for Suzuki
01:03:14did I and
01:03:16so I
01:03:18strolled in casually not wanting to appear to
01:03:22Be easily led and
01:03:25They were all hard at work changing valve springs
01:03:30And Stuart said yeah, we have to
01:03:33We change them every night on a race weekend
01:03:37because if we don't they'll break and
01:03:41Another part of this story is from
01:03:44Steve Scheibe who was the project engineer on Harley's
01:03:50VR 1000 Superbike back in the 90s running a BMW in in Moto America
01:03:57Yes, indeed. He's very much a person worth talking with because he's
01:04:04He's had his nose to the grindstone throughout his life and he's learned a thing or two
01:04:10And those are the guys we want to talk to
01:04:12And those are the guys we want to talk to that's for sure
01:04:16But
01:04:20Now where was I going with this Scheibe thing
01:04:26Well
01:04:29He said that there had been a steady increase in the maximum allowable
01:04:35fiber stress in valve springs if you're building a
01:04:39Production automobile or motorcycle you're going to use this stress level and your springs will
01:04:46Generally last this long
01:04:48but if you want
01:04:50You need more from the valve. For example by having only three and a half coils
01:04:55You're going to work to a higher level and he was talking about
01:05:00140,000 pounds per square inch which is a significant fraction of the yield strength
01:05:06and
01:05:07What happens when you work to higher you stress valve spring material at?
01:05:13Progressively higher levels is you get
01:05:16progressively shorter life
01:05:18so
01:05:20There in 2004 Suzuki were having to change their springs every night
01:05:24They were I think the first in MotoGP to adopt
01:05:29Pneumatic springs the ultimate solution. Yes, sir
01:05:32Because while we expect to see a fatigued crack in a steel spring
01:05:38Nobody's ever seen a fatigued crack in a gas
01:05:42So you have that little piston of quite a moderate pressure
01:05:46Gas pressure inside the chamber and the gas pressure is holding the valve closed
01:05:52Just as a metal spring holds it closed in a conventional system and naturally progressive. Yes
01:05:58It is naturally progressive which is why they stopped using it in suspension, but
01:06:05You can go farther you can say
01:06:09Well, we're drag racing we only run for a few seconds
01:06:13How much stress can we put into our valve springs in that state?
01:06:18Well, I've talked to people who say oh you got five runs from a set of springs. That's doing great
01:06:24five runs some teams in
01:06:27In those
01:06:29Wild and crazy like pro stockers and stuff
01:06:32one run on a set of springs and
01:06:36What they have discovered
01:06:39It used to be when I was a young man and
01:06:42Avidly reading books on how to soup up your triumph 650. They were talking about lightning
01:06:50The rock arms and they lighten them away until they must have been
01:06:54chewing them and
01:06:56They must have been just terrible for valve. I've seen some of those. Yeah. Yeah and
01:07:03But it's it's an ideal application for youthful fanaticism
01:07:07I'm going to polish this thing until it's gleaming everywhere. I'm going to do this as Marcus Aurelius said
01:07:15unwashed and without food
01:07:19This is what people get interested in in in this engineering business and everything else
01:07:25Their their focus of their attention their peripheral vision closes up. The only thing they can see is what they're doing
01:07:32I just I laugh because I my velocette has given I've done a lot of work to my velocette
01:07:37And if you've read the magazine over the years
01:07:40You may have read about it once or twice
01:07:42But I had a connecting rod inside my velocette engine. That was definitely somebody's pet. It had been highly polished
01:07:48Yeah, and it looked it looked pretty darn good. Never mind that it was both twisted and bent
01:07:53It was very shiny
01:07:55So it was useless. Anyways, I was shown a connecting rod made of Mar aging steel
01:08:03by
01:08:05machinists known to
01:08:07Albert Gunther
01:08:08Gunther was a great one for
01:08:12scrounging high technology off of his buddies in aerospace and
01:08:15This connecting rod had been milled from solid billet and it was thin it was thin everywhere
01:08:22And what had happened to it in service it had split where the the flanges on the sides of the rod met the web
01:08:30The radius in there wasn't big enough and it just cracked all the way down. It was wonderful
01:08:37well, we've left a lot out of this because we we didn't talk about you know, we talked about push rods and then
01:08:43There were perillas that had high cams
01:08:45And so what that did is they it was a push rod motor, but they put the camshaft very close to the cylinder head
01:08:50So you had shorter?
01:08:52Connecting or sorry shorter push rods. Yep
01:08:56gear driven cams the search for precision
01:09:00Long camshafts on six-cylinder engines torque torque vibrations changing the I mean, there are so many aspects
01:09:07to valve
01:09:09opening and closing all the heat transfer
01:09:11we spent a lot of time talking about getting the heat out of the valves and then the
01:09:15Evolution of the chamber and flow and all of that
01:09:18That's the beauty of
01:09:22Chasing performance here is that there's just seems to be
01:09:25Well, it's it's so attractive to the human mind because there are infinite problems. Yes
01:09:32That's right
01:09:33Because if you could shift where the problems occur
01:09:37When you try to learn something you discover ignorance faster than you discover fact
01:09:43And what you're discovering is things that you didn't know
01:09:48Yeah, so
01:09:52It's it's
01:09:54Renault got tired of broken Springs. They got tired of changing Springs every night and
01:10:00Somebody in a meeting said what about this idea? Yeah. Okay build it
01:10:05And it must have been a good year for car sales in France
01:10:10And but that's what it takes. That's what it takes is is either a
01:10:15Company that's rolling in money and can afford to spend 5% on R&D
01:10:20Which is a lot usual more usual is two and a half percent or a war
01:10:27Humans are fanatical about wars. They seem
01:10:32Unable to put them aside and they are fabulous
01:10:37fountains of technology
01:10:40it's
01:10:41Just the way things are, you know, so let's just keep talking until we're we're it's dinnertime
01:10:48Yeah, there's lots more to talk about here. There is well, we'll get back to it again. I my my final comment is
01:10:56One of my favorite things in life was getting the coil Springs
01:11:00I did a coil spring conversion in my velocite because it had hairpin valve Springs and if you want to wear out your valve guides
01:11:05Use hairpin valve Springs and hairpins are our two. They're two kind of coils
01:11:11Well, they're like hairpins and they they grab the valve and they're they're never gonna be centered the way a coil spring is
01:11:17so I spent a tremendous amount of money on
01:11:20coil Springs for the velocette and
01:11:23You can see how wonderful they are. You can see the nickel content the sheen
01:11:28Now you can just you can you can look at that after looking at a lot of engine parts and just go
01:11:34Oh, this has to be magic
01:11:36This has got beautiful things and they better because they were not cheap, but they work great and that thing runs awesome
01:11:42Now at least well, yes, and if you want to visualize what a hairpin spring looks like look at a clothespin
01:11:49Yes, exactly clothespin because the spring on there is the basic concept of the of the hairpin spring and so hairpins
01:11:57were developed as
01:11:59one of the possible solutions for
01:12:04Spring
01:12:06Fatigue and breakage because they didn't have the same sort of
01:12:12Prominent natural frequency that a coil spring has
01:12:15So when you see pictures of old-time max Norton's and so forth, they're the valve Springs out in the open air
01:12:22For everyone to see and that's the way it was in those days you could change valve Springs on the starting line
01:12:32If you had the right right tool just reach in there
01:12:36and
01:12:38Snap in a new one
01:12:40Great stuff great stuff. Well, that's it. Thanks for listening folks. I hope I hope this technical tour
01:12:48I like I like I promised at the beginning. We're gonna get a lot of KC out of that one
01:12:51But that's why we're all here. Anyways, so
01:12:54Thanks for listening. Hop down the comments. Tell us what's going on
01:12:58You know like it if you like it comment and subscribe
01:13:02And and if you have serious criticisms we want to hear that too because we do that's why we go racing
01:13:09mother nature
01:13:10criticizes our equipment
01:13:13She breaks it. Well, there's a guy who doesn't want me to touch my hat and that this I did not touch my hat
01:13:18I'm never taking off the sticker though. He'd that bothered him, too
01:13:23Whatever you got come on in her interwebs hit us
01:13:28Yeah, we'll catch you next time thanks for listening