- 2 days ago
Mecum Las Vegas Motorcycles 2026 takes place January 27–31 at South Point Hotel & Casino, and it’s one auction you won’t want to miss. Browse the full list of consignments, learn more about the Vegas event, and register to bid today by visiting Mecum.com. We’ll see you in Vegas!
https://www.mecum.com/auctions/las-vegas-motorcycles-2026/?utm_source=CycleWorld&utm_medium=Podcast1&utm_campaign=12032025
As Technical Editor Kevin Cameron likes to say about aircraft, they have to be light enough to fly and heavy enough to make it to the destination reliably. This drove innovation in design and metallurgy in aircraft that made it all the way to motorcycles, of course! Roller tappets for camshafts? Check! And so much more. Kevin and Editor-in-Chief Mark Hoyer talk about the flow of technology and design from aircraft to motorcycles.
Become a Channel Partner: https://octanemedia.co/home/become-an-advertiser/
Listen on Spotify: https://open.spotify.com/show/6CLI74xvMBFLDOC1tQaCOQ
Read more from Cycle World: https://www.cycleworld.com/
Buy Cycle World Merch: https://teespring.com/stores/cycleworld
https://www.mecum.com/auctions/las-vegas-motorcycles-2026/?utm_source=CycleWorld&utm_medium=Podcast1&utm_campaign=12032025
As Technical Editor Kevin Cameron likes to say about aircraft, they have to be light enough to fly and heavy enough to make it to the destination reliably. This drove innovation in design and metallurgy in aircraft that made it all the way to motorcycles, of course! Roller tappets for camshafts? Check! And so much more. Kevin and Editor-in-Chief Mark Hoyer talk about the flow of technology and design from aircraft to motorcycles.
Become a Channel Partner: https://octanemedia.co/home/become-an-advertiser/
Listen on Spotify: https://open.spotify.com/show/6CLI74xvMBFLDOC1tQaCOQ
Read more from Cycle World: https://www.cycleworld.com/
Buy Cycle World Merch: https://teespring.com/stores/cycleworld
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SportsTranscript
00:00:00Welcome back to the Cycle World podcast. Well, we're back anyway. If it's your first time, thank you for joining us. I'm Mark Hoyer. I'm the editor-in-chief of Cycle World, and I'm with Kevin Cameron, the technical editor.
00:00:12And this week's topic is how aircraft engines improve motorcycles. What do aircraft engines have to do with motorcycles?
00:00:22Before we get into that, this episode is sponsored by Mecham Auctions. Mecham is doing the Las Vegas Motorcycle Auction. It's the 35th annual auction in Las Vegas for Mecham.
00:00:35It's huge. They've got usually more than 2,000 motorcycles. There are 50 collections coming through this year.
00:00:43It's the biggest motorcycle auction in the world. Better registrations are open. I can't recommend this auction enough.
00:00:54Now, Mecham is sponsoring us, but I would go anyway, and I would recommend it anyway. So we're very happy to have them as a sponsor because there are so many reasons that I love going, and one of them is that there are 2,000 motorcycles,
00:01:08and there are multiple examples of everything that you would ever want to see. If you want to see a lot of Vincents, you can go see most of the Vincents.
00:01:17If you want to see an XS-650, and like, I wonder if there's supposed to be washers under that.
00:01:21You can find some either incredibly original XS-650 or one that's been restored to an nth degree, and you have a reference, and you can go there and take pictures,
00:01:31and they're just in—you can't even believe it when you—you know, there's like sort of the rodeo area where it's like the big stands and the big auction block where they roll everything across,
00:01:42and they've got the big screen, and it's mental the way that the auctioneer runs the show.
00:01:49But there's the whole area in the back. It's like the warehouse, and it's full of all the bikes, and they're just parked, and you can go look at them because you've got to look at them if you're going to bid on them.
00:01:59You don't have to go, but you should go. You can register. You can register and bid by phone. You can bid online. You can do all that stuff.
00:02:09They're adding more bikes. Kevin and I are going to do a podcast in a couple weeks that will be our picks from the auction. We'll get over those.
00:02:20It's like bring the family. It's really fun.
00:02:24And for me being in the industry, you get to see all your friends, all the collector guys. There's Baxter Cycle shows up.
00:02:33He's a great guy, and he brings bikes to the auction.
00:02:37Oh, there's a guy, Leo Goff, who's an engine guy or restorer. He used to drag race.
00:02:44He's in the Memphis, Tennessee area.
00:02:48He always goes. It's just a great place to gather and talk motorcycles.
00:02:53It's at the South Point Hotel and Casino.
00:02:56It's a great place to stay. It's huge. There's rooms booked now. Get in there.
00:03:01You can watch the live block cam on the website.
00:03:06TV, Roku, Mecham TV, Roku, Thursday.
00:03:10And I think they have added an extra day to the auction because it's really loading up with a lot of killer stuff.
00:03:20Join me. I'll be there.
00:03:22It is January 27th through the 31st or possibly an extra day.
00:03:2950 plus collections, etc.
00:03:30So anyway, thank you, Mecham, for sponsoring it.
00:03:33And thank you, audience, for checking out Mecham, all the stuff's in the description.
00:03:39And, you know, tune in for our collection podcast because it's a lot of fun.
00:03:45We pick bikes that we want to talk about, and Kevin picks them for some reasons,
00:03:49and I pick them mostly because, I don't know, I like pizza where Kevin's sort of very doctorial about his, like,
00:03:55the historical significance.
00:03:57I'm like, I really liked that when I was growing up.
00:03:59I want one, you know.
00:04:00It's a good time.
00:04:02So join us.
00:04:05Thank you, Mecham.
00:04:06All right, Kevin.
00:04:08Aircraft engines.
00:04:09So we were talking about the topic here and just the very fact that we said,
00:04:14well, what if this is a topic, and then off we went.
00:04:17We just started blabbing, and we thought, well, that's a pretty good topic because we haven't made really –
00:04:22I mean, we have a lifetime of research about this, more you than me, metallurgy and all the things that change.
00:04:28But the thing that strikes me about aircraft design, and Kevin will kind of illuminate all this,
00:04:35but the thing that strikes me is aircraft design is peculiarly honest.
00:04:41It has to be.
00:04:42And Kevin pointed out in our conversation that it has to be light enough to fly and heavy enough to make it.
00:04:48And the light enough to fly part is the honesty and the authenticity.
00:04:53It's just enough material to cover the working internals.
00:04:57It's not extra.
00:04:59It doesn't have covers that are supposed to suggest a certain feeling.
00:05:04Like when you put a fairing on a motorcycle, you can kind of shape it however you want.
00:05:09It should have some aerodynamic something about it.
00:05:11But we just put fairings on bikes, and we make them really pointy if that's what the style is,
00:05:16or they're very curvy and flowing if that's what the style was.
00:05:20It was style.
00:05:21Well, MotoGP fairings, functional, right?
00:05:25That's the way they look is that they're highly functional.
00:05:28They got all these wings and ground effects and stegosaurus things on the tail sections.
00:05:33It has a reason, and in that way, we kind of like it.
00:05:38But aircraft is honest and shrunk down, and you see the shape of the crankcase.
00:05:43You see where the push rods are going.
00:05:45You see the taper of the fins.
00:05:46There's just enough to get the job done that it was designed to do, and that's what I love about it.
00:05:52And that's what's, to me, that's what the best motorcycles are made of.
00:05:57If you look at a dirt track bike, it's very much a land-bound aircraft.
00:06:03It has a purpose.
00:06:04It's meant to be light enough, and it's meant to do certain things, and it's just enough.
00:06:09And I think that's what's so essential and beautiful.
00:06:12What do you think, Kevin?
00:06:13Well, the motorcycle, of course, is an engine, two wheels, and a place to sit.
00:06:20And there's a lot of nuance in all those elements.
00:06:25But although you can add all kinds of things to a motorcycle that are on there for artistic or emotional or socio-political reasons,
00:06:39when it comes down to trying to get around the circuit very quickly or building a ride you can stay on all day long and be ready for the party at the end of the day,
00:06:54that takes some doing, and there isn't room for extra.
00:06:59Aircraft, anything that is required to fly has to pay its way, because otherwise it is subtracted from the payload.
00:07:10So, for example, if the engines are going to have to be fueled on an inferior gasoline, inferior to what they were built for,
00:07:24they're not going to develop the power that they were required to, because they can't push on into NOC with a supercharger boost.
00:07:34So, you're going to use more runway, you're going to be running the engine in a different manner,
00:07:44so that your range suffers, your payload suffers, and ultimately it can become unworkable.
00:07:57So, in the early days of aviation, getting in the air was the big one, and that's what the Wright brothers did.
00:08:06And then the French, 1908, 1909, the Wrights gave some people rides.
00:08:17I think Glenn Curtis did it.
00:08:20And then everyone wanted to go, so they began to build the beginnings of airliners.
00:08:31Some of them were pretty boxy and strange-looking, and they had wicker chairs inside,
00:08:37because look around, what's lighter than wicker?
00:08:41Used to be wicker sidecars, right?
00:08:43So, all of it...
00:08:46Well, nature's composite.
00:08:48Yes, that's right.
00:08:50It was all very much cut and try, and that's what motorcycles were as well.
00:08:57The two Werner brothers, Russians working in Paris, tried putting an engine into a bicycle every place that they could,
00:09:10beside the rear wheel, on top of the rear wheel, on the handlebars.
00:09:15That's where the Solex ended up, driving the front wheel through a roller, and presumably blowing oily smoke onto your person.
00:09:25And ahead of the down tube, that's where Minerva liked it in 1903, or above the bottom bracket, which is where it's ended up.
00:09:35And cut and cut and try, they tried all those things.
00:09:39There was another outfit in Czechoslovakia that ran through the same set of experiments, because they wanted to be sure they weren't overlooking something.
00:09:49And there are people who have written theoretically about motorcycles, but it's because it's a simple machine, it's quicker just to try it.
00:10:01And so, because if you develop a math model, then you have to validate it.
00:10:09Yeah.
00:10:10You have to, oh, it predicts this, well, we'll build that.
00:10:13Oh, oops.
00:10:15Must have left out a term.
00:10:17So, anything that flew became very spare.
00:10:27The rotary radial engines, by rotary I mean that the cylinder, all the cylinders and the crankcase whirled around while the crankshaft was bolted to the firewall and did not rotate.
00:10:43Now, the advantage of this is that it doesn't vibrate.
00:10:50If you can balance the cylinder assembly because it's axisymmetric.
00:10:57And that was a great thing in early airplanes because they were made out of sticks and cloth.
00:11:05Two cables.
00:11:06With wire bracing to sort of pull it all together.
00:11:10And the cylinders on early Nome rotaries were machined from solid steel.
00:11:20And they were machined away until there was practically nothing left of them.
00:11:25We've all heard the jokes about he bored out his engine until it was just a stack of washers, meaning that the cylinder itself disappeared.
00:11:33The boring bar turned it into dust.
00:11:36Oh, that's the joke my friend Bill liked to say about his Trail 90 that was taken out to 110 or something.
00:11:43He said you can see the shadow of the cylinder or the piston moving in the engine.
00:11:48So, uh, the temptation was to machine anything that was going into an airplane because then you could control all the thicknesses.
00:12:01Well, uh, that didn't work out for complicated shapes like crank cases, cylinder heads, and so forth.
00:12:11And so for a long time, those parts were cast.
00:12:14That is, liquid metal, uh, was made to fill a mold whose cavity was the shape of the part you wanted.
00:12:24And you had to use the shrinkage rule for the material you were pouring because it would tell you how, uh, what's, what's dimensions you should make the cavity so that when it returned to room temperature, it would be the size and shape that you wanted.
00:12:41Lots of little details were uncovered when engines were made to run for long periods of time.
00:12:52Ball bearings suffered fatigue failure.
00:12:56One of the biggies was cylinder hold down bolts.
00:12:59The problem there is that the bolt isn't very long.
00:13:05You can tighten it up until it starts to get loose, torque to yield.
00:13:11Um, but it doesn't have much elasticity so that if there's a gasket there and the gasket compresses, you can lose all the preload and the cylinder is just sort of sitting there.
00:13:24So, uh, also they found that the hold down bolts or studs broke constantly.
00:13:34Now, this was a, a huge thing in, in the time of World War I, uh, the French and most of the Continentals used a lot of rotary engines.
00:13:47The Germans built a lot of inline sixes that were liquid cooled.
00:13:54Um, but this problem with threaded fasteners is that in the beginning threads were cut with a dye.
00:14:04What crudity.
00:14:07I mean, it works for a lot of low stress operations.
00:14:12Yeah, your swing sets and, you know, just, you can go get your grade fives.
00:14:18That's fine.
00:14:19But rolling, yeah, rolled threads.
00:14:21I, it reminds me when you talk about cutting threads, you know, you're, it's kind of savage.
00:14:26It works, but you know, you're taking your dye and you're like, and it's, it's cutting, cutting the steel or whatever your fastener is made of.
00:14:33Uh, I've seen that high speed video where they put a camera on a lathe or it's a milling machine or something.
00:14:41And it's the high speed kind of like microscopic camera.
00:14:44And it's showing you the cutting of the part.
00:14:47And it is savage, even though it looks like, oh, here's the chips.
00:14:50And when you, when you set your lay that really well, and you've got a nice sharp tool and it's in the right spot and you cut, you can get a long chip that just goes forever.
00:14:59It's just peeling off the whole thing.
00:15:01It's not flying.
00:15:02Do not take hold of it and try to pull it off the lathe.
00:15:06No, no, but it's, uh, it seems wonderful.
00:15:10And if the machine is, is in good shape and you're making that finish pass, especially you can end up with an incredibly shiny, seemingly perfectly smooth piece.
00:15:21But at the, at the microscopic level, it's really savage.
00:15:25Like you can find this on the interwebs.
00:15:27You can find that, that cutting video.
00:15:29So it's just, oh man, it looks so, so hard.
00:15:34And when you roll it, you know, you put that, that surface into compression.
00:15:38Into the thirties, into the 1930s, Wright was still, uh, doing ground threads for high stress fasteners and they were still failing.
00:15:51And of course, when you grind something, you can make the surface finish finer, but ultimately it is the result of scratching metal off of it.
00:16:03And, uh, so the process of rolling threads recommended itself because then the threads are forged.
00:16:17The surface of the surface of the metal is compressed, which you want because things fail in tension.
00:16:25So if you've got the surface in compression and you begin to apply stress, first, you have to overcome the preexisting compression in order to get no stress.
00:16:39And then you have to stress, and then you have to stress, and then you have to stress, and then you have to stress it even more to put it into tension.
00:16:44So rolled threads forge the material into the shape that's desired, and the threads are forged.
00:16:53They are not torn, i.e. cut.
00:16:57And they have even developed now methods of forging internal threads.
00:17:03It's for the same reasons that if, well, for example, the, the cylinders on, um, Wright's giant,
00:17:143350 that powered B-29s in the war, uh, powered the, um, Sky Raider, uh, in Vietnam,
00:17:26it's, it's, uh, cylinder is, uh, for a steel forging, an upset with an integral flange at the bottom,
00:17:35and it is bolted onto the crankcase.
00:17:38It's, naturally, like a motorcycle engine, starts out with four studs.
00:17:47What happens if you blow head gaskets?
00:17:49You go to six.
00:17:52Then you go to eight.
00:17:54Ten.
00:17:56Wright took it all the way to 21, which was all that they could cram into the flange.
00:18:02And every last one of them, the, uh, bolt came down on a part spherical washer that rested
00:18:13in a part spherical seat machined into that flange.
00:18:18So that when there was relative motion, and there always is, because when the engine fires,
00:18:2732,000 pounds of force try to uproot the cylinder, which means that the flange holding it down
00:18:34is bending down, and the mouth of the crankcase is bending upward, which means that the fasteners
00:18:42are, are being tilted.
00:18:44That's why those parts spherical washers are there, to allow it, so that the stress occurs
00:18:51between the washer and its seat, rather than being applied to trying to bend the, bend the bolt,
00:18:58accumulate stress cycles, and have a fatigue failure.
00:19:02Reminds me of the super blend bearing.
00:19:05Yes.
00:19:05The roller bearing, you know, we, we were having roller bearing failures in Norton's, and then
00:19:10also, uh, you know, Norton's of the sort of seventies and, uh, the Ducati V-Twin was having
00:19:18some issues and super blends.
00:19:21It takes that straight roller, you know, where you have perfectly parallel rollers.
00:19:26Cylindrical.
00:19:27Yep.
00:19:27Yes.
00:19:27Perfectly cylindrical.
00:19:29So the sides are, you know, pair, yeah, cylindrical.
00:19:31And then the cases would flex and the edge of that bearing would dig into the bearing service
00:19:36and it would go.
00:19:36Because the crankshaft is trying to do this.
00:19:39Yeah.
00:19:40Because, uh, North British parallel twins have no center bearing except for the AJS matches.
00:19:47Um, and so the crankshaft does flex at higher revs.
00:19:53And so the main shafts are doing this.
00:19:59They're, they're mutating.
00:20:00They're like the axis of a gyroscope when it's getting tired and wants to lie down.
00:20:04And that edge loads roller bearings.
00:20:09Well, why not use ball bearings?
00:20:10Because they have, uh, roughly a little better than half the load capacity of a roller.
00:20:18So you think to yourself, well, let's relieve the edges of the, the outer ends of the, of the roller just enough that it would accommodate that degree of crankshaft flex.
00:20:33We're not talking about an eighth of an inch or something huge like that.
00:20:37We're talking about something quite small.
00:20:39Yeah.
00:20:40It's just like a, some kind of radius instead of.
00:20:43They can make, they can make any profile you want on those rollers.
00:20:47And they figured it out and we got, we got those so that your, your dish, your dished, uh, washer surface, just like that, giving them a little bit of ease to slide instead of bend or dig in and flake and cause problems.
00:21:03A motocross dad came to me and said, my son must just rev the living Dickens out of his 250 because he said, uh, I can't keep main bearings in it.
00:21:14And I said, well, what do you think's happening?
00:21:17And he said, well, it's like, I tried putting rollers in there and the edges, you know, they flaked off.
00:21:26So I said to him just being, you know, I, I, recreation can be such a thing as reading a bearing catalog because there's a lot of good information in there.
00:21:39How about using a spherical bearing?
00:21:41It, it, it has good capacity as a roller bearing, but the shaft can, can nutate and nothing gets overstressed.
00:21:53Is nutate the new word that we're going to be, you know, we have a sparity.
00:21:56It could be a sparity.
00:21:58And velisets.
00:21:58Nutating.
00:21:59Yeah, velisets.
00:22:00TZ750 is a good one.
00:22:03Yep.
00:22:04So I spent 10 years with those TZ750.
00:22:07So there, well, reading the bearing, just to pause, I want to pause to, just to clarify, there are people and then there's Kevin Cameron.
00:22:17And what does Kevin Cameron do for recreation?
00:22:19He reads the bearing catalog because there is a lot of great information.
00:22:24You'd better read it.
00:22:25Yeah.
00:22:26You better read it.
00:22:27And if you, uh, it's going to the steel supplier, the metal supply and reading the book that talks about the qualities of the metal, like, well, what are you trying to accomplish?
00:22:41And you can read all of that stuff and you can say, well, you can wonder if you're working as I am on a Taylor craft aircraft, putting a Taylor craft aircraft together.
00:22:51And the guy who's assigned me at this place, this airplane hangar where I go with my son, he's assigned me to fixing the panel because I busted out my hammers and dollies to fix the backing plate and the brakes.
00:23:06So they're called shin brakes.
00:23:07And so they're these real mechanical, they're cable actuated brakes with this kind of horseshoe actuator.
00:23:12The linings are put on the inside of the drum.
00:23:16So the linings rotate.
00:23:18Yeah.
00:23:19And the, the shoes are just steel.
00:23:22They're just steel.
00:23:24And so you put all that stuff together.
00:23:26Uh, anyway, he's assigned me.
00:23:30I bought, I was fixing the backing place because they are made, they are lighter than a pie tin.
00:23:35What we're talking about, like lightness of aircraft, just enough to get the job done.
00:23:39A pie tin, an aluminum pie tin is heavier material than the backing plate for this break.
00:23:45Nothing.
00:23:46It's not mechanical.
00:23:46It's just a cover.
00:23:47And then the, the, uh, the brake itself, the mechanics of the brake, it's like this kind
00:23:53of dog bone shape that bolts to the axle with seven 82 degree taper, uh, countersunk screws
00:24:01blade.
00:24:02And then the mechanics are all there and the plate just sits in between that dog bone that's made out of steel and that aluminum.
00:24:13But I had my hammer and dolly cause the things are mangled.
00:24:16And so I'm smoothing them out and I'm, I'm fixing the flange and he's, we're just getting to know each other.
00:24:21And he says, well, you should work on this panel too.
00:24:26But what I'm getting to is like, you get to learn about what's it made of.
00:24:30Cause I like to weld and there's cracks in this panel.
00:24:33I'm like, well, I should, I should weld this.
00:24:36And I, I asked him what's the panel made of it because it's aluminum.
00:24:40It's a very thin aluminum.
00:24:41It's probably, I don't know, 30,000 or something.
00:24:44And also very light.
00:24:47And he says, I don't know.
00:24:48I said, is it 1100?
00:24:49Cause I know I can weld 1100.
00:24:5230.03, age 14.
00:24:53I could weld that.
00:24:55And it also, uh, it age hardens.
00:24:5830.03 gets better with age.
00:25:01It's, you know, like you build your body work out of 30.03 and it'll stand up.
00:25:05Give it a little rest before you put it on your bike.
00:25:08Precipitation hardening.
00:25:09But you, yeah, but you know what the numbers are because you read the catalog.
00:25:13And if it's 2024, which is a very popular aircraft aluminum, you can't weld it.
00:25:18It just has so many alloying elements that when you try to weld it, the, uh, what do they call them?
00:25:26Heteroatoms move to the center of the weld and become a defect.
00:25:32Yeah.
00:25:33And you just, so it's, and they've, and then you learn about numbers by reading the catalog.
00:25:38Cause 2024 was just what it was.
00:25:40And then, then they go up the chain.
00:25:42And it's 20, whatever it is.
00:25:43And it's 20 and it goes along and they've added more elements and it's stronger for this.
00:25:47And you get to learn about the manganese and the other things that they put in to get those qualities.
00:25:52So read the catalogs.
00:25:53That's what I'm saying.
00:25:56Read the bearing catalogs, read the metal catalogs, learn about it.
00:26:00Use, figure, figure out what the metal is used for.
00:26:03This is what Kevin's good for us.
00:26:05Cause he'll be like, Oh yeah, they made those pistons out of RR 56.
00:26:08That was the Rolls Royce alloy.
00:26:10And it was the 56 recipe, you know, that's like, Oh, Hey, that's pretty good to know.
00:26:15I like it.
00:26:15Well, RR 58 was used until like 98, 1998 in, uh, uh, GP racing and formula one.
00:26:26So it was good stuff.
00:26:29And not that there aren't better alloys now, but the thing is you get to know how to work
00:26:35with something, you know, what to expect from it.
00:26:38So it's an old friend.
00:26:40Can you replace an old friend with a new friend?
00:26:44If you have to, I suppose you, you do it, but that causes people to cling to old standards.
00:26:51And for example, I wanted to make gears and I, I did some reading and I found out that
00:27:00for small gears, 8620 steel is a good material because it can form a relatively thin case hardening
00:27:10and be heat treated to have a tough core.
00:27:15Well, later I learned that, that Yamaha used 8620 to make connecting rods for all their two
00:27:21stroke stuff for those same reasons, because what had to bear on the hardened surface needle
00:27:27rollers.
00:27:28It's one of my, this is reminding me of one of my favorite moments is when we went to go
00:27:33see, uh, Byron Hines with the first Harley, uh, V twin drag drag bike.
00:27:39And we, we got access and we had Byron, right?
00:27:44Byron Hines.
00:27:44I mean, the metallurgist and designer and they're in there making this thing from scratch because
00:27:52it had to be a push rod thing.
00:27:53And they, you know, it was like, whatever it was, 2200 or 2,500 CC, 2600 CC is ridiculously
00:28:00large, big, huge cylinders and the push rods of a certain length.
00:28:04And you were having a conversation because they had handfuls of parts.
00:28:07We were at a test, they were running it down the strip and then Kevin's talking to Byron
00:28:12and he's holding up the parts and, and you were asking him like, Oh, is that, you know,
00:28:178620 or is that this or that?
00:28:19And he's like, well, no, it, it doesn't need to be durable.
00:28:23It needs to be tough, you know?
00:28:26And that was the conversation and it was the quality of the material that was being used.
00:28:29It wasn't like necessarily a case hardened piece because they didn't need that.
00:28:33It just needed to be really durable for a short period of time.
00:28:37Like it needed to be tough, not necessarily durable.
00:28:40It didn't need to last 46,000 miles.
00:28:43It needed to last quarter mile plus, or maybe to the next run or whatever it needed to be.
00:28:47And it's, uh, it's wonderful where you get that guy who has, who's looking at all the
00:28:54recipes and making things out of way.
00:28:56Another, another similarity between motorcycles at high level and aircraft is that parts have
00:29:04specified lifetimes and, uh, every part in a racing motorcycle has a specified lifetime,
00:29:14wrist pins, pistons, rings, uh, connecting rods, what have you, how many hours when it's
00:29:23powered out, it has to be replaced.
00:29:26And in the aviation business, if you decide, well, it'll probably be, it looks good to me.
00:29:35I think I can do another a hundred hours.
00:29:38Hmm.
00:29:39Is that good for business?
00:29:43We don't think so.
00:29:44So, so you're having to work with, within the capabilities of all these materials processed
00:29:54in various ways that are well understood by specialists in that field.
00:30:01So it used to be, for example, that, uh, mnemonic 80 was a, uh, refractory, uh, material
00:30:11for making gas turbine blades.
00:30:13It was developed by the English, but it, it had this, um, problem in that the grain structure,
00:30:24the size of the crystals in the material, see all, all normal metallic material is polycrystalline.
00:30:32Now, my dad was of that generation that said, oh, look, it crystallized and broke.
00:30:40Nothing.
00:30:41It's already crystalline, so it can't crystallize.
00:30:46Um, but what's going on there is that the, at operating temperature and under stress, the
00:30:57material is made of these poly, zillions of tiny crystals oriented randomly in those
00:31:05days, we came to oriented, uh, crystal materials.
00:31:10And then finally, single crystal materials.
00:31:14You got trouble with the, the intergranular zones where all those crystals are stuck to
00:31:20one another, get rid of the zones.
00:31:23Then you'll get rid of the trouble.
00:31:24You should explain that a little bit more, just that the turbine blade is now one giant
00:31:29crystal.
00:31:30Is that correct?
00:31:31Yes, that's correct.
00:31:32And they, they're able to grow the crystal under very carefully controlled conditions so
00:31:39that it begins solidifying where they want it to.
00:31:43And it starts at a seed crystal that has been placed in the mold correctly oriented so that
00:31:50when crystallization, when solidifying begins that it begins from that crystal and continues
00:31:58with its orientation, then there's a spiral passage that basically says this acts as a
00:32:05filter to make sure that that orientation is being preserved on its way to the actual mold
00:32:12cavity and they are able in this way to produce these, these single crystal blades that are, they
00:32:24just, they don't look different.
00:32:26They look just like, Oh yeah, that's obviously a turbine blade.
00:32:30It hasn't been machined yet.
00:32:32What's it out of?
00:32:33Oh, F-100 or something.
00:32:35Well, uh, the problem of course, with jet engines is, is that they have to keep operating
00:32:43them hotter and hotter.
00:32:44And they finally got them to the point where during takeoff, the gas passing in which the, by which
00:32:53the blade is surrounded is hotter than the melting point of the material, but they have developed
00:32:59cooling methods that keep layers of cool gas flowing over the surfaces.
00:33:07Boy, there we are sitting back in our seats.
00:33:11Having a little sip of champagne or some tea, you know.
00:33:16And meanwhile, those hardworking turbine blades are whirling around in a, in really hot air,
00:33:24hot combustion gas.
00:33:26So this is a process of development that has taken some time.
00:33:32It is just a miracle though.
00:33:33It really is a miracle that, that somebody decided to get rid of the, the intergranular zone
00:33:40or whatever, that they just said, well, we can solve this problem by, and, and someone,
00:33:45you know, they just worked on it and figured it out.
00:33:48I mean, if you've ever, if you've ever, if you've ever, um, mixed concrete, you know, you,
00:33:56you have some, some, uh, cement and you have some, some sand and you have some gravel and you mix
00:34:06all that stuff together in a specified amount of water, uh, and you can make, uh, concrete
00:34:13like for a foundation.
00:34:15So in this case, um, it is as though the, the little stones in the gravel are the crystals
00:34:22and the, uh, cement that is holding them all together is the intergranular zone.
00:34:29Um, and the gravel in there is all randomly oriented and odd, different shapes and it's,
00:34:38it's a workable material.
00:34:40Well, it's why my garage, it's why my driveway is cracking for one.
00:34:45When, when you, when you apply stress, repeated cyclic stress to, uh, polycrystalline materials,
00:34:53uh, the little atoms that are, um, under strain in some places because the intergranular material
00:35:06is trying to make a bond with material, other things that are nearby and crystals, it's under
00:35:13some strain.
00:35:14So at some point that strain may be exceeded pop that bond is gone.
00:35:19Now it's load is being carried by its neighbors and pop, pop.
00:35:27So there's all this trouble that goes on in the intergranular zone because basically you've
00:35:32got these, this massive crystals.
00:35:35This is what, what John Britton was talking about when he said, you know, he said, when
00:35:41you've worked with directional materials, as long as I have, ordinary metals start to seem
00:35:47like just really tightly packed sand.
00:35:53And that's what they are.
00:35:54Yeah, it is.
00:35:55It's a, it's a big, uh, a big feeling of distrust.
00:35:59And what was the old saying about, uh, magnesium electrified dirt is what, um, the jet engine,
00:36:08I was going to say when we were talking about turbines and all that, and, you know, starting
00:36:13the podcast often and saying like how essential aircraft are and that, you know, they're, I'm
00:36:19a, we're a fan of piston engine stuff in my house.
00:36:23You know, my son's 12 and he's a little pilot now taking lessons and he's flown a 150 and
00:36:28a 172 and he's helping me with the Taylor craft.
00:36:31He's really into it.
00:36:32He wants to understand.
00:36:33We like those.
00:36:34We like to propeller planes and we're fascinated with jets and we love our F 35s and, and all
00:36:39of that, but it's really, um, the one thing that I think is we, we're, we kind of derisively
00:36:45call jets vacuum cleaners because they just make the whirring sound, but they're awesome.
00:36:51And what I do love about a jet engine is the shape of turbine blades, how they've become
00:36:58these beautiful, efficient little swirls, like little, they're just really, they're so
00:37:06elegant and wonderful.
00:37:08So we, we do like the jet engines, but, uh, we're here for combustion in a cylinder, you
00:37:15know, pop and then valves.
00:37:16What are you holding up there?
00:37:18Well, that's a, that's an exhaust valve from a, from a, uh, an R 43 60.
00:37:24And Kevin was once a collector of those, just so you know, three of them in my, in my shop
00:37:32at a point.
00:37:32They're not small.
00:37:33It's why I had a gantry crane, folks.
00:37:35You can't just pick an up 43 60 up.
00:37:38One pound per horsepower.
00:37:40Yep.
00:37:403,500 for takeoff.
00:37:42This is a, uh, hollow valve exhaust valve, and it has this very thick stem because it is
00:37:51hollow too.
00:37:52The head is hollow and it is partly filled with sodium metal, which melts at a quite a low temperature.
00:38:00Not this temperature, but in service, uh, the sodium rattles around inside there because
00:38:10the valve is moving, lifting, returning, and then sitting closed for a while and then lifting,
00:38:18closing.
00:38:18And that serves to equalize the temperature of the part all over.
00:38:26Most of the cooling is between the valve and the seat because that's a, the seat is a lot
00:38:35cooler than the valve and the head is a lot cooler than the seat into which it is shrunk.
00:38:41So sending heat up the stem, you want the stem to be well lubricated.
00:38:49How hot can you tend the lubricant stand to be?
00:38:52Yeah.
00:38:52350, 400?
00:38:54Yeah, you don't want to coke, you don't want to coke your oil.
00:38:56That's a big problem in the exhaust bridge too.
00:38:59If you have little passages.
00:39:00Yes, they have to be designed to drain after the engine has stopped.
00:39:07It's like a turbo where they, where they used to keep the fan running on the turbo where you
00:39:11had a shutoff period where you had to idle the engine to keep cooling oil going through
00:39:18the turbo bearings so the bearings would cool off.
00:39:21And because if you just shut it off, it's just cooking in there.
00:39:25It's turning it into gunk and then no more circulation, which means that the exhaust bridge
00:39:32becomes very hot and it expands powerfully yielding the material around it.
00:39:40And then when you switch off and the magneto goes to sleep, uh, the cylinder head cools and
00:39:53that material that has been yielded is now too big for the exhaust bridge, which is placed
00:39:58in tension.
00:40:00We spoke before about how tension is the big problem.
00:40:05So, uh, there were some low performance air cooled four valve engines in, uh, the early
00:40:14days of, uh, motor cycling, um, of super bikes, and they were able to operate as long as they
00:40:26stayed away from making everything real hot and suffering, uh, exhaust bridge failures.
00:40:33That is the material between the two exhaust valves.
00:40:37If you look at a Ducati cylinder head, turn it upside down, you'll see, uh, two large intakes
00:40:45and then as far away as they can get from each other, two little dinky exhausts and they're
00:40:52moved apart as far as they can for the obvious reason that, uh, the larger the exhaust bridge
00:40:59region is the better it can conduct heat away to the rest of the head and not be hot enough
00:41:05to cause this, uh, cycle of tension, compression, tension, compression, pow, a crack forms.
00:41:16And this is a, uh, crack formation in cylinder heads.
00:41:21There's all sorts of special instructions for, uh, general aviation pilots in the use of engines
00:41:29in such a way as to avoid, uh, various forms of cylinder head cracking.
00:41:34Oh, well, there's the, uh, the Howard 500 beautiful, uh, uh, beautiful twin engine piston,
00:41:40high performance, uh, aircraft, uh, the landing procedure coming down from cruise is pretty complex
00:41:50because you have to slow down slowly.
00:41:52You can't just shut it down cause it'll shock cool the engine and it'll break stuff.
00:41:58Yeah.
00:41:58You gotta, you're up at high operating temperature and you're doing your thing and the engine's
00:42:02happy and it's, it's all fine, but you don't just like shut her down.
00:42:06You've got to bring her down nice and easy.
00:42:09There's, it's like way out of the way far away from the airport.
00:42:11You're like, you got to plan this and you got to go through the procedure so you don't wreck
00:42:15your very complex and wonderful, uh, radial engines.
00:42:19Um, I talked to a gentleman who operated oversized aircraft.
00:42:26Um, I guess he contracted with NASA and so forth and move large boosters and so on in
00:42:32these guppy airplanes.
00:42:34Yeah.
00:42:35And, uh, he said to me, he said, the moment we bought our first turbine powered airplane,
00:42:42I understood why the airlines got rid of piston engines so fast, just as fast as they possibly
00:42:51could because he said, you've got the flight engineer's manual for the piston engine and
00:42:59for the jet engine, you have, you have the, the, uh, automatic system.
00:43:06And you, you, you hit run and the FADEC, uh, fully automated, fully automated, uh, digital
00:43:18engine control FADEC.
00:43:20Yeah.
00:43:20And it handles it for you.
00:43:24They're doing that.
00:43:25They're doing that with piston engines a bit.
00:43:28Now you're getting where you just have a single thing.
00:43:31You're just like, Oh, I want more power.
00:43:32And you just ask for it and it takes care of all the business for you.
00:43:36It's not like your Taylor craft or your cub.
00:43:38Well, some cubs didn't even have mixture control.
00:43:40You know, some of the J threes just had a carburetor that you didn't have mixture control.
00:43:45So the higher you went, the richer it got.
00:43:47So you got up to 7,000 things.
00:43:52So that's not FADEC, you know?
00:43:55No, sir.
00:43:55Well, also FADEC is important because, um, there was a time when the homeowner, uh, went
00:44:03out to mow the lawn for the first time in the spring.
00:44:06The engine wouldn't start.
00:44:08So he or she, uh, and dump the gas out, put fresh gas in, tried that.
00:44:15Still wouldn't start.
00:44:17Change of spark plug.
00:44:19Starts right up.
00:44:21Mows the grass.
00:44:21But, um, a more modern technique is to buy a new lawnmower every spring because you can't
00:44:30make it start.
00:44:31Because.
00:44:32Yeah.
00:44:33I was just going to say, who was your relation that moved the mower into the sun?
00:44:36And that was my mother.
00:44:38Got it hot.
00:44:38Yeah.
00:44:39Your mother got it hot enough that it would start on the old gas.
00:44:43The old, that it would evaporate enough fuel.
00:44:45Yeah.
00:44:46Uh, the, once it got warm and enough fuel would evaporate that it could be ignited by
00:44:52a spark and it would start.
00:44:54And she told me that she said, well, she said, I, I thought I'd leave it in the sun for a
00:45:00while.
00:45:01And then it usually starts.
00:45:03Yes.
00:45:04Well, Dale, Dale Waxler, um, wheels through time, the late Dale Waxler, uh, what a great
00:45:10guy he was.
00:45:11Uh, his son is, um, is running the museum and he's obviously well-versed in all this old,
00:45:17particularly old American stuff.
00:45:19So it's in Maggie Valley and, uh, what is that?
00:45:21North Carolina.
00:45:23And, um, great museum.
00:45:25Uh, Dale was very good about, uh, what do you say?
00:45:29A intelligent person and really well-educated, but also the farmer guy, very, uh, experiential.
00:45:37Like he'd done so many things for so long and he'd resurrected so many old motorcycles
00:45:41and hit, he was a big fan of the sun and arrow Croyle unpaid endorsement.
00:45:46So Croyle is this, uh, it's an, it is relatively expensive, but it's, it's in my experience, it's
00:45:51one of the best chemicals, penetrating oil to free something that's rusted or stuck.
00:45:57And he was a great freer of stuck cylinders and he would hose the thing off with arrow
00:46:03Croyle and he'd get it in the bores and he'd park the thing out in the sun and really get
00:46:07it hot.
00:46:08And then he'd break the cylinders loose and then he'd work it really slowly, really
00:46:12slowly.
00:46:13And he had all these motorcycles where he did that.
00:46:16And, um, you know, the great sun, we can rely on the sun for some things, can't we?
00:46:20It's wonderful.
00:46:20Starting in the lawnmower after a, now we just buy one or, or it's electric and we change
00:46:25batteries every 36.
00:46:27This is, this is why ultimately we have a big celebration at the time of the reversal
00:46:34of the seasons.
00:46:36Oh, it's getting colder.
00:46:37The days are getting shorter.
00:46:39What if it keeps on forever and we just freeze solid?
00:46:43Oh, now it's getting warmer.
00:46:45I think it's time to celebrate.
00:46:47And we do every year.
00:46:49Something about entropy in there somewhere.
00:46:51Yes.
00:46:52Yes.
00:46:54But we've got enough.
00:46:57We have a future because the sun isn't gone that far along the progression.
00:47:02Thank goodness.
00:47:03One of the things that you'll notice is that, uh, cooling fins on air-cooled motorcycle engines
00:47:08are around a quarter of an inch spacing.
00:47:12And at one point when Suzuki were trying to enter Grand Prix racing and make their bikes reliable,
00:47:23uh, they were the first company to win a world championship with a two-stroke engine.
00:47:29And that was, uh, the 50 CC.
00:47:31Um, but if you look at any of the great radials, you will see that the cylinder fin spacing is much, much closer.
00:47:46I'm going to try to do this right now, uh, wheel this thing out for you.
00:47:54Sorry, Spotify-ers, but we are doing, uh, show and tell.
00:47:58Here we go.
00:48:00Oh, look at those cylinders.
00:48:01Look at that.
00:48:02That, that, well, that reminds me of GSXR 750 when they did the close, the very close fin pitch when they were air-oil-cooled.
00:48:08Wow, that's remarkable.
00:48:09Now, well, you talked to me about this before where, uh, there was a, a form, uh, like a guide
00:48:18and they were cutting those with blades because you couldn't cast it so fine.
00:48:24Well, this was a desperation move.
00:48:27Yeah.
00:48:27Because as we noted at the beginning of this podcast, uh, it's cut and dry.
00:48:32Anyway, and when they got the, uh, 1820 engine, which powered all those B-17s, what, 14,000 something of them.
00:48:42It's a lot of B-17s.
00:48:45Um, of course, every time the takeoff power and cruise power are increased by development,
00:48:54there's more heat to get rid of.
00:48:57And so you have to have more fin surface area.
00:49:00Well, they were able to cast down to about two, two hundred thousandths fin spacing.
00:49:11And that was rough because in making a 2800 cylinder that way, they had to set about 1200 core pins
00:49:21to support the, the cores that, um, simulated the airspace between the fins.
00:49:28A lot of work there and it couldn't be automated.
00:49:34Could not be automated.
00:49:37Somebody had to, oh, look, that's, get the supervisor over here.
00:49:42I did it wrong.
00:49:43Well, pattern making is it's, is it's really its own art.
00:49:46And a lot of motorcycle designers relied, I don't know how it is today, but the guys I talked to who were doing this stuff 20, 40 or more years ago,
00:49:58were really relying on the pattern makers at the casting place.
00:50:02At the founder, yeah.
00:50:03At the foundry to actually make it right.
00:50:06Yes.
00:50:06The dimension, the radius, all that stuff was art.
00:50:10Yeah, because you're sitting around, right.
00:50:13I mean, you know, whatever, uh, Dr. Taglioni is sitting around drawing it.
00:50:20He's not, he's not in the radius of the finning and saying that it needs to be a radius of one and a half millimeters or something.
00:50:28That's the foundry guy.
00:50:29And even in porting, even in the way, the, the design of the ports and the chamber, the final finished chamber, if it's not machined, was really a foundry thing.
00:50:41Yep.
00:50:42And they were, yeah.
00:50:44What Suzuki did when they needed more fin area was they made, went to a finer spacing.
00:50:49With aircraft engines in the early days, the cylinders just stuck, stuck out of the, uh, housing around the crankcase into the airstream.
00:51:00Tremendous drag and bad cooling because the front of the cylinder was cooled well and the back of the cylinder wasn't cooled at all because the air doesn't want to go through those tiny fin spaces.
00:51:14There's a boundary layer on everything that says, stop shoving on me.
00:51:20I'm sleeping here.
00:51:21Well, and what are we trying to attain with cooling, right?
00:51:24When, when we were talking earlier, when we were discussing this podcast, the fining on the cylinder head is long and big.
00:51:32And as it tapers down to the bottom of the cylinder, it's quite short because it's not as hot as where the, the rings are at the top.
00:51:38Where the fire is.
00:51:39Where the fire is.
00:51:40And that you're cooling, you know, if your air oil cooled, which everything, you know, everything was also oil cooled.
00:51:46If it had oil circulating at all, we just didn't say it, but it was air oil cooled.
00:51:51You're looking to homogenize the temperature as much as is reasonable.
00:51:55And you're taking that oil and pumping it up into the cylinder head to lubricate the stuff, but also to cool it and to take the heat back down in the crankcase, which puts it up at a temperature that's closer to what the cylinder head is doing.
00:52:08And really your design is saying like, yeah, we ended up in a temperature range that was good for the oil and it was good for the metallurgy and it didn't overstress the things.
00:52:19And the front of the cylinder wasn't super hot and the back cylinder isn't super cold and we don't have dimensional stress and things that are happening.
00:52:27Like it's, it's kind of an art.
00:52:30When they, when they needed more cooling fin area, one way to get it was to make the fins deeper and there are limits to that because aluminum is not the best conductor of heat.
00:52:50Silver is pretty good.
00:52:52Copper is sort of in between there, but aluminum is lightweight and it was discovered during World War I.
00:52:58That the ability to move heat per pound of material doing the moving was best with aluminum.
00:53:10So that's why cylinder heads are not silver.
00:53:17Also the, of course, the tremendous weight.
00:53:19So eventually you could get to the point where the fins are so deep that the air can't reach the bottom of them.
00:53:28So the NACA, the National Advisory Commission for Aeronautics, did a 10-year study on how best to cowl radial air-cooled engines and how to cool them.
00:53:48And they found out that having the cylinder sticking out in the plain old air stream was the worst way to cool.
00:53:59And that what they ended up with was that if this is a slice through the cylinder and the air is coming this way,
00:54:09you had to have a baffle that fit right tight against the cylinder fins and went round to the back and only let the air out through a narrow passage.
00:54:21So it was open in the front for over 100 degrees.
00:54:27And the baffle wrapped tightly around so that the air had to pass through the hot fins at the back of the cylinder,
00:54:35just as it had passed through the hot fins at the front.
00:54:37And when you arrange the cylinders, so in a, in a, like a two-row or a three-row radial,
00:54:43the reason they look like corn cobs, they don't look like corn cobs, is because the cylinders are offset.
00:54:50So the first set of cylinders, they're ducted and that's keeping the heat.
00:54:55It's extracting the heat from the cylinder here and the cylinder here.
00:54:58And then the next one in the row is isolated.
00:55:01It's not getting those hot cylinder air circulating.
00:55:05It's baffled so that every cylinder gets cold air.
00:55:08Fresh air, yeah.
00:55:10Now, AJS built a V4 in the 1930s and it was air cooled.
00:55:17And it was a V4 with the crankshaft transverse.
00:55:23So the aft cylinders overheated.
00:55:26And they got hot enough to encourage detonation and detonation said, I'm your buddy.
00:55:35And so in order to stop losing the top piston ring land and getting material eroding from the cylinder head,
00:55:44they had, the first thing was they reduced the compression ratio.
00:55:48And they kept reducing it until they finally stopped the detonation at about five and a half to one.
00:55:56And then some wiseacre in the company said, well, in our last test, the V4, it's a 500,
00:56:07is barely any faster than our 350 single.
00:56:11Why are we doing all this complicated work?
00:56:13So eventually, they had to give up the idea of letting air come through the front fins and get heated up.
00:56:23And then that hot air trying to, in quotes, cool the rear cylinder.
00:56:27This is why parade mode exists.
00:56:30If you're stuck in traffic on a big V-twin, and it's one of those horrible summer days,
00:56:39just turn off the rear cylinder, turn off the spark, turn off the fuel injection,
00:56:46and just let it be itself.
00:56:50No combustion at all.
00:56:51And the front operates as a big single.
00:56:54There's a tut, tut, tut, tut.
00:56:55You can keep up with traffic perfectly well and stop and go.
00:56:58You hardly even notice.
00:57:01Yes.
00:57:01I'm not kidding.
00:57:03You hardly notice.
00:57:05It's good.
00:57:06So that's one of those things that there have been several engines,
00:57:13motorcycle engines, that tried to cool the rear cylinders with hot air coming off of the front cylinders.
00:57:18Square four, buddy.
00:57:19Yep, the aerial square four and that Silverhawk, strange V4 that was built earlier.
00:57:33It just, it's a bad idea.
00:57:36Well, we're going to talk about the Silverhawk because that's a Mecham.
00:57:39That's a bike that's coming up for auction.
00:57:41And there's a, there is a Silverhawk V4 30s era.
00:57:45And it's, it's a very interesting motorcycle.
00:57:49Well, we'll talk about that on the podcast where we talk about the auction bikes.
00:57:54Sure enough.
00:57:54So what did they find when they, when they made the pitch of the cylinder fins closer and closer?
00:58:02They couldn't cast it.
00:58:04So then they said, okay, we've talked about this a lot of times.
00:58:08Now we actually have to do it.
00:58:10They began to forge the heads out of solid aluminum.
00:58:17And then they machined the fins.
00:58:20They machined the ports.
00:58:22They machined the valve pockets.
00:58:27They, everything was machined.
00:58:30And they claimed that it was a savings of time over positioning 1200 core pins.
00:58:37I laugh because I'm a home machinist and I have a lathe and I have a mill and I do things.
00:58:42And I build little tools and stuff.
00:58:44And I'm very proud and satisfied if I can make a dimensionally accurate top hat bushing out of bronze.
00:58:51You know what I mean?
00:58:52And to machine an entire cylinder head at a time when we didn't have 3D printers and we didn't have CNC five axis mills and CAD and everything.
00:59:02They did have cam operated automatics, however.
00:59:05And that's how they were made.
00:59:06Not by elderly machinists in octagonal metal framed spectacles holding up the micrometer.
00:59:18Well, make the next cut 1.2 thousandths deeper.
00:59:22Yeah.
00:59:24So it was a set it and forget it.
00:59:27The casting, the big forgings came off the machine.
00:59:31They got rough machined.
00:59:32And then what did they find?
00:59:36The reason that Suzuki's little motor with very closely spaced fins was never seen again is because it wouldn't cool.
00:59:44The bike went too slow to force air through those fine fin spaces.
00:59:50So on these machines with forged and machined heads, another reason for all those baffles to be there is to make sure that of all the air that's let into the front of the nacelle has to pass through fin space.
01:00:11Every cable, every cable, every hose, every bundle of wiring had to be sealed through those baffles so that it didn't produce a leak.
01:00:25And then they could cool these huge engines, making as much as 3,700 horsepower, 3,800 horsepower for takeoff at the very end.
01:00:39And they could do so by making sure that they had the highest possible pressure in front of the cylinders and baffle arrangement.
01:00:54And that's why B-29 crews were required to not climb for some time after takeoff.
01:01:12If they were carrying a maximum load of fuel and ordnance because it would be too laborious for the engine and the climbing speed would be reduced such that it would reduce the flow of cooling air through the cylinders.
01:01:28So all of this material was not taught to young farm boys to become flight engineers.
01:01:35It got converted into a bunch of slide rules that would enable you to compute how to stay on the safe side with these monsters.
01:01:45And it's quite a wonderful thing to imagine taking thousands of people who never dreamed of flying, much less being a flight engineer, and making them able to do a fairly good job.
01:02:01There were some exceptions, of course.
01:02:03Yeah.
01:02:05I love the manuals of those of that era when I read.
01:02:10Like I have a Jacobs kind of engine maintenance and repair manual.
01:02:15And it's not a huge, thick thing.
01:02:16You know, Jacobs is a seven-cylinder.
01:02:19It was on Cessna 195s for sure.
01:02:22Oh, yeah.
01:02:23In a 300 horse, typically.
01:02:25They had one that was a little bit less power than that, but typically a 300 horse.
01:02:28And it's beautifully written, and it's – the clarity is something else.
01:02:35You know, this is not artificial intelligence.
01:02:37It's not 60% accurate.
01:02:39It's 100% accurate.
01:02:40And it's beautifully done by humans, and it's great.
01:02:46We've talked about this before, and we did a podcast on books and talking about particularly like the technical writing of the 40s, 50s.
01:02:54This stuff was very, very well done, beautifully constructed language, very clear, easy to understand.
01:03:02Because if they didn't, people wouldn't understand it.
01:03:04They wouldn't understand it because we're just like, hey, I'm – you know, you're out there doing whatever you're doing as a 19-year-old in Iowa,
01:03:11and you're, you know, driving the tractor, or you're doing whatever your job is as a 19-year-old,
01:03:16and then you've got to go get in a B-17 or a B-29, and here's your book.
01:03:22And you've never done it before.
01:03:23One of my favorites is that if you look at the pistons that Shoichiro Iremadri put in the 50cc Honda Twin Grand Prix engine, 1965,
01:03:38the skirt height in relation to the bore is about 60%.
01:03:43And when that era started, the skirt was like 1.3 times the bore.
01:03:53They were real old-time tractor pistons in those early Honda 4s.
01:03:59So here was Iremadri trying to take friction out, and he thought to himself,
01:04:04contact between the piston and the cooler cylinder wall is how the piston stays alive,
01:04:10so I can't do away with all of that contact.
01:04:14How much can I – how much can I cut away and still survive?
01:04:24Air-cooled aircraft engines suffered the same problem.
01:04:31Because this is about 60% of this.
01:04:37What's your piston out of?
01:04:39This is out of a 3350.
01:04:45Yeah, this is from a B-25.
01:04:48Okay, that's a 2600.
01:04:512600. It's six and an eighth of a bore.
01:04:55Well, they used one basic cylinder arrangement for the 1820, the 2600, and the 3350.
01:05:04In fact, when the 3350 was being developed, they used 1820 cylinders for, you know, as a first try.
01:05:13And they had to go through five different iterations of cylinder design because it is cut and try.
01:05:19Well, there's a real – I mean, this is what happens in motorcycle development.
01:05:24You take a company like Polaris, who's making all kinds of different engines for different wheeled things,
01:05:29side-by-sides and, I don't know, buggies and all that, and then motorcycles.
01:05:35And they've done the work on the combustion chamber.
01:05:37They know that this combustion chamber works.
01:05:41And so when they're starting out with a new engine, it's like, yeah, let's put that and use this valve arrangement, and away we go.
01:05:47This is what nature does.
01:05:49Nature is very economical.
01:05:51Anything that's working well is continued in the next model.
01:05:55Indeed.
01:05:58Well, I want to get – we're kind of getting close to a time where we normally say we're moving on.
01:06:05But I want – so we've talked about cooling and all these other things about oil and cocaine and things that happened in aircraft engines that helped us in motorcycling.
01:06:16If it's at all possible, let's briefly, ha, ha, ha, ha, he says, talk about the evolution of metallurgy because it was really what drove the possibility of everything.
01:06:31And that what we got out of a 1936 knucklehead was really a result of some development in aircraft and the metallurgy that allowed us to get into the modern era.
01:06:46Well, they started to use roller tappets, which are in every big radial.
01:06:54And they go back to Manley's engine that he was building for Langley's aerodrome, which was his effort to get into the air before the Wright brothers.
01:07:04Not that he knew that they were working.
01:07:06They were quite secretive.
01:07:07But Manley saw that this cam ring that he decided to use, which had cam profiles every few degrees all the way around it, it had concave places, which meant that a flat tappet couldn't work.
01:07:27So he thought to himself, I'll use a roller because it will fit in a concavity, provided that its radius is smaller than that of the concave place.
01:07:40Good thinking.
01:07:41And so in the 1920s, around 1925, Harley adopted roller tappets in their racing singles.
01:07:53And those roller tappets appeared in production in 1929 on the D model flathead and then the W and then the K model and finally the Sportster.
01:08:09And in the Sportster, it has four cams all geared together, just like in the D model.
01:08:18Those roller tappets come straight from aviation.
01:08:22All those rotary engines, a good chance if you look at one that it has roller tappets.
01:08:29So these similarities are not by accident because similar solutions to similar problems.
01:08:38Now, motorcycle engines started out with cast iron flywheels because the complicated shape of the counterweights and all the rest of it was easy, easier to cast than it was to machine from solid.
01:08:53And when they ran those engines fast enough, the crank pin wallowed out.
01:09:00It became loose.
01:09:03So, oh, we'll make the flywheels out of steel.
01:09:07Well, RPM kept going up and Robert Iannucci notes that there are a lot of G50, G50 flywheels, which are soft, mild steel, holding doors open all over England because their crank pins wallowed out.
01:09:29So they had to go to alloy steel.
01:09:33And this kind of thing took place intensively through the 1920s and 30s.
01:09:44Metallurgy had been an art.
01:09:47It had to be turned into a controllable science so that when you design a new engine,
01:09:52you could rely on the qualities of the materials you were using.
01:09:58It wouldn't be the result of somebody had a big argument with his wife on the weekend, came in Monday and did a batch of bearing steel that just failed all over the world.
01:10:10That won't do.
01:10:11You have to have these standards that are adhered to.
01:10:15You've probably heard about dreadful quality control in early Chinese motorcycles and scooters.
01:10:26It was a sort of a joke in Southeast Asia where they made big marketing efforts.
01:10:34But they didn't yet have these rigid industrial standards so that when you picked out a ball bearing, let's put a 6305 in there, we'll want a snap ring.
01:10:51That tells you, it gives you the beginnings of the part number.
01:10:55And do you want standard internal clearance or do you want C3 clearance, which allows you to press fit the bearing onto something so that that causes the inner race to swell?
01:11:08Or you clamp the outer between crankcase halves.
01:11:12That compresses it and does away with some of the internal clearance.
01:11:14Well, and that, that, that, that press is a, is a spec and you can hear, you, you will hear a bearing.
01:11:22I experienced this on an early prototype, uh, not an early prototype, but a prototype motorcycle I was riding before it was released.
01:11:31And I was getting to ride this thing and I, you know, I'm making notes, a motorcycle tester.
01:11:36And I came back in and I said, uh, there's a sound coming from the rear wheel.
01:11:40And the engineer said, like, I was talking to the guy who was running the program and he's like, Steve, get over here.
01:11:45And Steve comes over and he says, he's picking up a sound out of the back, you know, back wheel, kind of a sound.
01:11:52And the guy's like, oh, Steve's like, yeah, we're changing the press on that bearing.
01:11:56It's making noise right now, but we'll change, they'll change the bore ever so slightly.
01:12:00So when the bearing goes in, it isn't squeezed quite as hard and the bearing, the bearing will be to spec.
01:12:06It has, it has internal clearance.
01:12:08So there's room for oil between the rolling elements and the races and everywhere you go in making parts for machines.
01:12:19You run into materials that aren't up to the work, castings that crack, uh, hardened materials that fall, inadequate tensile strength, connecting rods that break near the small end.
01:12:35BSA gold stars were famous for this.
01:12:38Rod breaks, the piston goes up and pounds the valve shut, whether the camshaft will let them happen or not.
01:12:47And it ruins the head.
01:12:49The short end of the rod is whirling around, jabbing holes in the crankcase as it goes.
01:12:55It may even damage the frame because there's a place where the frame is, is woggled to make, to clear the crankcase.
01:13:04If one of the holes forms there, the frame could be damaged.
01:13:07People used to say, when I, when I stopped sliding, I thought maybe I can save the Magneto.
01:13:14So, uh, but that's the, that's the, the, the, um, the one horse shape poem about the vehicle that was made so artfully that all the parts had the identical lives, which is ideal.
01:13:32Of course, you'd want all the parts to last equally.
01:13:35So you're not having to constantly take your car apart.
01:13:38Oh, the steering shaft that's timed out.
01:13:40Let's, we can't go on vacation.
01:13:42I have to change it.
01:13:43The one horse shape, uh, in the last second of the hundredth year, it all fell into a pile of dust.
01:13:52Every part failed completely at the same time.
01:13:56Sure.
01:13:58So, uh, in design, you're having to, to work out the lives of the lives of these things.
01:14:05One tuner said, um, I had some crankshafts that cracked.
01:14:10I took them to the metallurgist.
01:14:11The metallurgist said, these are wonderfully hardened journals.
01:14:16This thing will run a hundred thousand miles.
01:14:18No problem.
01:14:20Provided you don't exceed the manufacturer's recommended RPM.
01:14:24But he said, inside the material is pudding.
01:14:30In other words, why are we going to put chromium and molybdenum and who knows what all else into this part when it doesn't need it?
01:14:39Nowadays, there's a rev limiter.
01:14:41Which helps.
01:14:44So, you give the problem a solution that is no more, no better than it needs to be.
01:14:53Because to do otherwise is to pay for something you can't use.
01:14:57Well, having a cast, yeah.
01:14:59Having a cast crankshaft in your Jaguar 3.8 liter, uh, inline six that you run to, you know, 5,500, maybe 6,000 for special occasions if you take care of the rods.
01:15:11But really, 5,500 is what they rev to.
01:15:14And, uh, they'll do that a long time.
01:15:16Very long stroke.
01:15:18Um, but if you want to make a lot of power and you want to make a race motor out of one of those and really rev them up, it's, it's, um, we're going to machine a crankshaft out of billet steel.
01:15:26Something that is...
01:15:274340.
01:15:284340.
01:15:28That's going to be significantly stronger.
01:15:31Yep.
01:15:32And have excellent fatigue properties as well.
01:15:35And replace the rods at the same time.
01:15:37And it is the job of metallurgy to tailor materials to the applications.
01:15:43And if there's a sufficient market for it, a new standard will be written for that material and it will join the inventory.
01:15:53And this is, this is how an industry can exist because they're all of these givens.
01:16:00All they have to do is put their finger on that key and they know the note that will play.
01:16:07It reminds me of the lessons that we keep on learning.
01:16:10You know, we've talked over the years where Ricardo, uh, high speed internal combustion engine by, um, Harry Ricardo.
01:16:17It's a great book.
01:16:18Go find one.
01:16:20Don't, you don't need a first or second or fifth or just find any one, buy it as cheaply as you can.
01:16:25It's also on the internet.
01:16:26It's on the internet.
01:16:27Yeah.
01:16:27Just read it, read it on the web.
01:16:29Why not?
01:16:29It's non-mathematical.
01:16:31It's a very good book and it, it codified so much.
01:16:36And it was not read by people in the fifties who were still making engines that had terrible cylinder heads, terrible breathing, terrible combustion chambers.
01:16:46It just wasn't read.
01:16:47It was like the lesson that needed to be learned over and over again.
01:16:51And it reminded me of the era of Indian long before Polaris got it.
01:16:56It was sort of recycled and kicked around and people would buy the name and then they would try to do something or they would take a Bella set like climber did at the climber Indians where you had a velo that said Indian on it.
01:17:09And one of the versions that we got was like Gilroy CMC era, somewhere around that time.
01:17:17And they were, they got the name and they were basically like custom bikes and they would call, you know, Baker drive train, but they didn't have a spec.
01:17:26They were just saying like, okay, I'm going to get that engine.
01:17:30We're going to redesign these cylinder heads to make them look like this, even though it was a 45, like a Harley, basically a clone.
01:17:36And then the transmission we're getting from that guy and the primary cases here, and there was no spec and nothing would really go together.
01:17:46Talk about tolerance stacking where, you know, the spec is that it has to be somewhere in this range, but then it's this much.
01:17:52And then down the line, everything spreads out and it just doesn't bolt together.
01:17:57And it's just every, give every station on the production line a stack of shims.
01:18:01Yeah.
01:18:02And so, you know, there they are learning and they learned the lesson.
01:18:05And they, I know about this because the people who were doing it said, hold on a minute.
01:18:10They got in some manufacturing expertise and that's where the story came from.
01:18:15Yeah, they were doing it this way, but now we have a spec.
01:18:18And so when we give that to the transmission maker, it has to match this and we check it.
01:18:23And then it, you know, then it bolts together.
01:18:26Yep.
01:18:28Well, that's it folks.
01:18:29That's it for aircraft 101 versus motorcycles.
01:18:34How did we get here?
01:18:35We hope, we know it's, you know, off the beaten path.
01:18:39It's not, it's not your TZ 750 podcast or your RD 350 or whatever.
01:18:45But it's something near and dear to us.
01:18:47We loved aircraft.
01:18:48We do love aircraft engines and we, you know, Kevin's been studying this stuff and he's got big note cards, thousands of pages of notes about metallurgy and where.
01:18:57Sort of embarrassing.
01:18:58Well, you know, an embarrassment of riches, let's say.
01:19:04I've heard that before.
01:19:05Let's hear it for that.
01:19:07But we, we thank you for listening.
01:19:10We also thank Meekam once again for sponsoring the podcast and a couple more coming up.
01:19:15Tune in.
01:19:17Go to the auction if you can make it.
01:19:19And it's late January, January 27th through the 31st.
01:19:22It's, it's a wonderful experience.
01:19:24You can see everything.
01:19:26You can stream it afterwards.
01:19:27You can watch it and bid remotely and all that.
01:19:30It's, it's exciting to be on the floor, to be honest.
01:19:33It was great.
01:19:34We watched a bike cross the block for more than a million dollars at the end of that auction.
01:19:40It was really something.
01:19:41So, uh, very exciting and also some bargains.
01:19:45So, um, thanks for listening and we'll catch you next time.
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