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Most Experts Aren’t. That's something the late Smokey Yunick said
back when I was a seaman deuce. Every month my mail delivers one or two messages saying it's still true. The messages usually come from some superbly experienced fellow who has literally spent his life working on cars or trucks. He is the Local Guru when it comes to engines for homebuilts and he's taking the time to let me know that the automotive engineers I like to cite in my articles aren't quite as bright as I seem to think they are, offering an experience-based example to prove his point. Unfortunately, the offered example invariably deals with cars or trucks, things in which the fellow has a life-time of experience, whereas automotive in the sense used here, does not, although it could include them. To an engineer, automotive means something that can move under its own power. Like an oil tanker, the Space Shuttle, or a gold dredger. My usual reaction is to hit the delete key. I get more mail than I want, most from people with real problem, some of whom I can help. But it's always sad to hear smart people say dumb things. And on the whole, these are smart people, even though a life-time of experience hasn't tipped him off that we're taking about two different meanings for automotive. We all start out pretty dumb. As we age we gather information and gain experience and, assuming a fair share of native wit, we end up a bit smarter than when we began. Mebbe all this guy needs is a nudge in the right direction. So you say hello and the odds are the fellow is having the same problems as everyone else except he was a bit too proud to say so. With this type of Expert you'll often discover his life-time of experience has been with just one type of engine or perhaps one type of car and he has been trying to transfer that experience to a Corvair or a Volkswagen and isn't having much luck. I mean, who ever heard of a head torqued to only eighteen foot-pounds! That has to be wrong... right? If the fellow hasn't figured out the meaning of automotive there's a good chance he won't have any idea in the blue-eyed world about Class of Service but a good understanding here is the real key to a successful conversion so you give it a shot. A car or light truck uses a variable speed, high-rpm, low-torque engine whose nominal output approximates 25% of its peak output. Nominal output is defined as the amount of power the engine was designed to deliver for approximately 98% of its service life. The only time it’s expected to produce more… that wayward 2%… is when accelerating or climbing a hill. Once on the flats -- once you've reached a Stable State of cruise -- the figures are a good match. For hilly regions vehicle manufacturers offer different ratios for the rear-ends. Economy takes a hit but over-all, the figures match up. Respect an engine's Class of Service and you'll be rewarded with 2,000 to 5,000 hours between overhauls. You can always demand more output from either type of engine but doing so will reduce it's service life. With a converted VW, for example, your Mean Time Before Failure will typically fall from about 2,000 hours in vehicular service to about 200 hours when powering a plane. By comparison, an aircraft engine is a single-speed, low-rpm, high- torque engine whose nominal output approximates 75% of its peak output. Peak output may be defined further as maximum sustainable output, and as Peak-sub I, meaning an instantaneous value or dyno blip, something you might use to impress the newbies. Since our goal is to produce thrust throuigh the rotation of a propeller, our primary interest is in the amount of torque that appears in the crank, and in the propeller's efficiency at a given rpm. The measurement of thrust is quite simple and articles describing different types of homebuilt thrust stands have appeared in the literature and on the internet. You will note that horsepower, which serves no useful function at this stage, has not been mentioned. It usually takes an exchange of half a dozen messages or thereabouts to arrive at this point, if in fact we arrive at all. In the overwhelming majority of cases the Local Expert simply vanishes. Which is doubly unfortunate because the best is yet to come. When we convert an auto engine for use in an airplane we are trying to convert it from one Class of Operation to another to make it more suitable, usually in the area of mechanical reliability. By comparison, the typical flying Volkswagen starts out as a marginally suitable auto engine that is then made even less suitable for aircraft use by turning it into a hot-rod enigine. Why? Usually because the person doing the conversion has little understanding of an aircraft powerplant. Indeed, most such experts are merely the local Guru grown old, selling dune buggy engines to the kiddies. And after all, it does fly the plane, right? So why even bother. Well.... because we should. A properly built engine is more efficient. It produces the required torque at a lower rpm and wear increases exponentially with rpm. That means a properly built engine uses less fuel to deliver the same thrust and last longer, too. But a properly built engine is also a lot less expensive to build and nowdays that's becoming a critical factor. See that chart down there? The one title BORE VS STROKE? (It's embedded in the article in the blog; you guys on r.a.h. will have to go dig it out and print yourself a copy.) The chart shows the bore & stroke combinations for most common conversions and for everything using 88mm jugs or larger, or a 78 mm or longer crank, is going to have to machine the crankcase & heads to match. What they'll end up with is a dune-buggy combination -- a high-rpm engine that produces most of its torque up high. Itty-bitty toothpick of a prop. Not very efficient at all. Lots of machining to do. Lots of tricky bits to go wrong during assembly... which is why some folks don't even offer the thing assembled. But it's all a bit of a joke because no matter HOW BIG the engine, it's MAXIMUM SUSTAINABLE OUTPUT is going to be between 35hp and 45hp. Yeah, I know -- everybody is selling 80hp and up. Which is a dyno blip, not a steady output. Lotsa cubes is going to get you out of the weeds quicker but once you get the puppy cleaned up you're flying behind your basic 40hp engine, depending on the local atmosphere. The limitation has to do with the heads, not the displacement. The cylinder heads only provide enough fin-area to manage the waste-heat from about 40hp. Unless its nice and cold or you are nice & high. But the dune crowd only knows how to build big-bore strokers. Now go take anohter look at that chart. Limit your jugs to the stock 85.5mm.s and your cranshaft to a 78mm. At those sizes there's NO MACHINING REQUIRED. Your displacement is 1791cc, your maximum SUSTAINABLE output is about 45hp and your peak torque is going to come in at about 2800rpm. Did I mention that no machining is required? You've altered your cam timing but you're running a stock cam or a Schneider 'chugger,' the one used in the orchard-blower engine. You're running SINGLE PORT HEADS... because you're now an airplane engine, not a hot-rod. Your Volumetric Efficiency is pushing 70% and you're about a $1000 dollars ahead of the game because you haven't had to buy all that machining and you're using a higher percentage of stock, off the shelf parts. You're also running a longer, more efficient prop -- hopefully one you've carved yourself. The thing starts on the first flip because it has an efficient ignition system, one that automatically adjusts itself to the load and a 20A. electrical system. But no starter, please. As it is, it weighs about twenty pounds less than any engine offered by anyone else. But of course, it's not a dune-buggy engine. And the Instant Experts will stand in line to damn it with faint praise for that fact alone even while it flys circles around them and is still going strong when they're doing their second valve job of the year. In my opinion, this is the perfect engine for an aerodynamically clean single-seater, like Bruce Kings little beauty. Had fate dealt me a different hand, that's what it would be going into. It would also be a good match for a KR-1, the early Jodel, Druine, the Teenie Two and similar designs. Kill the parent, you got orphans. And that applies to engines, too. -R.S.Hoover |
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On Sat, 19 Jul 2008 20:05:36 -0700 (PDT), "
wrote: The thing starts on the first flip because it has an efficient ignition system, one that automatically adjusts itself to the load and a 20A. electrical system. But no starter, please. As it is, it weighs about twenty pounds less than any engine offered by anyone else. the local vw powered Druine D3 turbulent has a starter. there is a light weight ring gear added to the front of the engine. it is a lightweight one welded to a disc that bolts in behind the prop. the ring gear is from a japanese car, I forget which one. the starter mounts in a simple bracket that bolts in place of the car engine fuel pump. the starter turns over the 1600cc engine quite easily. the starter motor is a replacement for a large bmw motorcycle. the overall weight of the setup isnt much. it has been quite reliable so far. Stealth Pilot But of course, it's not a dune-buggy engine. And the Instant Experts will stand in line to damn it with faint praise for that fact alone even while it flys circles around them and is still going strong when they're doing their second valve job of the year. In my opinion, this is the perfect engine for an aerodynamically clean single-seater, like Bruce Kings little beauty. Had fate dealt me a different hand, that's what it would be going into. It would also be a good match for a KR-1, the early Jodel, Druine, the Teenie Two and similar designs. Kill the parent, you got orphans. And that applies to engines, too. -R.S.Hoover |
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Adding a starter is a trivial chore but on a properly assembled engine
there is no need to do so unless the engine is mounted on a pylon, geared, or the prop is otherwise remove from easy access. With a suitable ignition system the engine starts as easily as a lawn-mower and will continue to run so long as their is fuel and air, unless it is shut off.. Some conversions, such as the Aero-vee, use an ignition system having a single, fixed firing point. The engine will not start unless rotated at about 300rpm, making a starter motor a necessity. Others use a belted or geared drive having such a high ratio that hand- propping is impractical.. When all elements of an electrical starting system are included, the weight can be as much as forty pounds more than for a hand-propped engine. |
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PING Phlsti
Please contact me with a valid email address. Your question(s) need clarification in one area but are generally too long to justify a general post. -R.S.Hoover |
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On Sun, 20 Jul 2008 07:03:32 -0700 (PDT), "
wrote: Adding a starter is a trivial chore but on a properly assembled engine there is no need to do so unless the engine is mounted on a pylon, geared, or the prop is otherwise remove from easy access. With a suitable ignition system the engine starts as easily as a lawn-mower and will continue to run so long as their is fuel and air, unless it is shut off.. Some conversions, such as the Aero-vee, use an ignition system having a single, fixed firing point. The engine will not start unless rotated at about 300rpm, making a starter motor a necessity. Others use a belted or geared drive having such a high ratio that hand- propping is impractical.. When all elements of an electrical starting system are included, the weight can be as much as forty pounds more than for a hand-propped engine. But to run a starter, no electrical "system" is required. Just a battery capable of cranking the engine over a few times. Recharge it when you park the plane. ** Posted from http://www.teranews.com ** |
#6
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![]() But to run a starter, no electrical "system" is required. Just a battery capable of cranking the engine over a few times. Recharge it when you park the plane. --------------------------------------------------------------------------- Well, let's see now. You've still got the battery onboard so that means a battery box & cables. Then the cables need some kind of control... even a knife switch will do but you gotta have one... unless you're planning on just rubbing the cable against the battery post. From the switch at least one of the cables has to run to the starter motor which of course has to be held in position so as to mate with the ring-gear, which you still need too. So it looks alike you've still got everything in the average electrical 'system' except the dynamo & regulator/rectifier. And if you're using the coaxially installed jobbie I've described in previous articles you've just saved yourself the grand sum of 7.36 pounds, ending up with 90% of an electrical system that can't produce any electricity. With logic like that I'd be ashamed to sign my posts too :-) -R.S.Hoover |
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On Jul 20, 5:05*am, " wrote:
Most Experts Aren’t. *That's something the late Smokey Yunick said back when I was a seaman deuce. Every month my mail delivers one or two messages saying it's still true. The messages usually come from some superbly experienced fellow who has literally spent his life working on cars or trucks. He is the Local Guru when it comes to engines for homebuilts and he's taking the time to let me know that the automotive engineers I like to cite in my articles aren't quite as bright as I seem to think they are, offering an experience-based example to prove his point. Unfortunately, the offered example invariably deals with cars or trucks, things in which the fellow has a life-time of experience, whereas automotive in the sense used here, does not, although it could include them. To an engineer, automotive means something that can move under its own power. Like an oil tanker, the Space Shuttle, or a gold dredger. My usual reaction is to hit the delete key. I get more mail than I want, most from people with real problem, some of whom I can help. But it's always sad to hear smart people say dumb things. And on the whole, these are smart people, even though a life-time of experience hasn't tipped him off that we're taking about two different meanings for automotive. We all start out pretty dumb. As we age we gather information and gain experience and, assuming a fair share of native wit, we end up a bit smarter than when we began. Mebbe all this guy needs is a nudge in the right direction. So you say hello and the odds are the fellow is having the same problems as everyone else except he was a bit too proud to say so. With this type of Expert you'll often discover his life-time of experience has been with just one type of engine or perhaps one type of car and he has been trying to transfer that experience to a Corvair or a Volkswagen and isn't having much luck. I mean, who ever heard of a head torqued to only eighteen foot-pounds! That has to be wrong... right? If the fellow hasn't figured out the meaning of automotive there's a good chance he won't have any idea in the blue-eyed world about Class of Service but a good understanding here is the real key to a successful conversion so you give it a shot. A car or light truck uses a variable speed, high-rpm, low-torque engine whose nominal output approximates 25% of its peak output. Nominal output is defined as the amount of power the engine was designed to deliver for approximately 98% of its service life. The only time it’s expected to produce more… that wayward 2%… is when accelerating or climbing a hill. *Once on the flats -- once you've reached a Stable State of cruise -- the figures are a good match. *For hilly regions vehicle manufacturers offer different ratios for the rear-ends. *Economy takes a hit but over-all, the figures match up. Respect an engine's Class of Service and you'll be rewarded with 2,000 to 5,000 hours between overhauls. You can always demand more output from either *type of engine but doing so will reduce it's service life. With a converted VW, for example, your Mean Time Before Failure will typically fall from about 2,000 hours in vehicular service to about 200 hours when powering a plane. By comparison, an aircraft engine is a single-speed, low-rpm, high- torque engine whose nominal output approximates 75% of its peak output. Peak output may be defined further as maximum sustainable output, and as Peak-sub I, meaning an instantaneous value or dyno blip, something you might use to impress the newbies. Since our goal is to produce thrust throuigh the rotation of a propeller, our primary interest is in the amount of torque that appears in the crank, and in the propeller's efficiency at a given rpm. The measurement of thrust is quite simple and articles describing different types of homebuilt thrust stands have appeared in the literature and on the internet. You will note that horsepower, which serves no useful function at this stage, has not been mentioned. It usually takes an exchange of half a dozen messages or thereabouts to arrive at this point, if in fact we arrive at all. In the overwhelming majority of cases the Local Expert simply vanishes. Which is doubly unfortunate because the best is yet to come. When we convert an auto engine for use in an airplane we are trying to convert it from one Class of Operation to another to make it more suitable, usually in the area of mechanical reliability. By comparison, the typical flying Volkswagen starts out as a marginally suitable auto engine that is then made even less suitable for aircraft use by turning it into a hot-rod enigine. Why? Usually because the person doing the conversion has little understanding of an aircraft powerplant. *Indeed, most such experts are merely the local Guru grown old, selling dune buggy engines to the kiddies. *And after all, it does fly the plane, right? So why even bother. Well.... because we should. *A properly built engine is more efficient. *It produces the required torque at a lower rpm and wear increases exponentially with rpm. *That means a properly built engine uses less fuel to deliver the same thrust and last longer, too. But a properly built engine is also a lot less expensive to build and nowdays that's becoming a critical factor. See that chart down there? *The one title BORE VS STROKE? *(It's embedded in the article in the blog; you guys on r.a.h. will have to go dig it out and print yourself a copy.) *The chart shows the bore & stroke combinations for most common conversions and for everything using 88mm jugs or larger, or a 78 mm or longer crank, is going to have to machine the crankcase & heads to match. *What they'll end up with is a dune-buggy combination -- a high-rpm engine that produces most of its torque up high. *Itty-bitty toothpick of a prop. *Not very efficient at all. *Lots of machining to do. *Lots of tricky bits to go wrong during assembly... which is why some folks don't even offer the thing assembled. But it's all a bit of a joke because no matter HOW BIG the engine, it's MAXIMUM SUSTAINABLE OUTPUT is going to be between 35hp and 45hp. Yeah, I know -- everybody is selling 80hp and up. *Which is a dyno blip, not a steady output. *Lotsa cubes is going to get you out of the weeds quicker but once you get the puppy cleaned up you're flying behind your basic 40hp engine, depending on the local atmosphere. The limitation has to do with the heads, not the displacement. *The cylinder heads only provide enough fin-area to manage the waste-heat from about 40hp. *Unless its nice and cold or you are nice & high. But the dune crowd only knows how to build big-bore strokers. Now go take anohter look at that chart. *Limit your jugs to the stock 85.5mm.s and your cranshaft to a 78mm. *At those sizes there's NO MACHINING REQUIRED. *Your displacement is 1791cc, your maximum SUSTAINABLE output is about 45hp and your peak torque is going to come in at about 2800rpm. Did I mention that no machining is required? You've altered your cam timing but you're running a stock cam or a Schneider 'chugger,' the one used in the orchard-blower engine. You're running SINGLE PORT HEADS... because you're now an airplane engine, not a hot-rod. *Your Volumetric Efficiency is pushing 70% and you're about a $1000 dollars ahead of the game because you haven't had to buy all that machining and you're using a higher percentage of stock, off the shelf parts. *You're also running a longer, more efficient prop -- hopefully one you've carved yourself. The thing starts on the first flip because it has an efficient ignition system, one that automatically adjusts itself to the load and a 20A. electrical system. *But no starter, please. *As it is, it weighs about twenty pounds less than any engine offered by anyone else. But of course, it's not a dune-buggy engine. *And the Instant Experts will stand in line to damn it with faint praise for that fact alone even while it flys circles around them and is still going strong when they're doing their second valve job of the year. In my opinion, this is the perfect engine for an aerodynamically clean single-seater, like Bruce Kings little beauty. *Had fate dealt me a different hand, that's what it would be going into. *It would also be a good match for a KR-1, the early Jodel, Druine, the Teenie Two and similar designs. Kill the parent, you got orphans. *And that applies to engines, too. -R.S.Hoover Hello Bob Nice article as per usual. How about something more on the Type 4? Most info on this engine seems to be " That is what the VW engine should have been" or " yeah, the type 4, now that`s a different story" etc. I am sure I am not the only one with an interest in the "bigger" veedub, and an in-depth discussion on what can be done with it and to it, written by an expert like yourself, would be hugely appreciated. It is heavier than the T1, less available, and parts are more expensive, but it is still a flat-4 aircooled VW, ain`t it? Thank you and regards, Erik Snyman. PS. Have you perhaps got something written on the T4 on your blog? If so, a link, please. |
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![]() "erik" wrote Nice article as per usual. How about something more on the Type 4? Most info on this engine seems to be " That is what the VW engine should have been" or " yeah, the type 4, now that`s a different story" etc. I am sure I am not the only one with an interest in the "bigger" veedub, and an in-depth discussion on what can be done with it and to it, written by an expert like yourself, would be hugely appreciated. It is heavier than the T1, less available, and parts are more expensive, but it is still a flat-4 aircooled VW, ain`t it? --- new post starts he ---- As far as that goes, how about a small blurb on the type 1, 2, 3, 4, 5, and how many other types there are? g About the time I think I am understanding VW's, someone brings up "type 1, only," and my eyes start to glaze over. ;-) Like just basic, like what years, cars they were used in, and the main differences between them. I had a 72 convertible bug for a while, and don't even know what type it had! I wish they had made a 6 cylinder bug engine, with decent heads. That would be a much better aero engine, me thinks. I'm afraid that 40 HP is not going to ever be enough for what I want to build. -- Jim in NC |
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On Jul 21, 12:58*pm, "Morgans" wrote:
As far as that goes, how about a small blurb on the type 1, 2, 3, 4, 5, and how many other types there are? g ---------------------------------------------------------------------------- Types? They number in the low HUNDREDS, from the basic beetle or Type I to some NATO aviation support vehicles, Type 338 and higher. Volkswagen has ALWAYS reserved 'Type' to define the CHASSIS. Volkswagen engines have ALWAYS been defined by a number approximating their displacement: 1100, 1500, etc. What Ami-Ricans refer to as the 'Type 4 engine' is actually three engines, the 1700, 1800 and 2000, which was installed in about a dozen different vehicles, not counting the applications from the Industrial Engine Divsion. --------------------------------------------------------------------------------------------- About the time I think I am understanding VW's, someone brings up "type 1, only," and my eyes start to glaze over. *;-) *Like just basic, like what years, cars they were used in, and the main differences between them. ----------------------------------------------------------------------------------------- Variations to the basic VW engines probably number in the thousands; you can line up at least a hundred variations in the heads alone. Since the changes were incorporated within production runs you will need a full set of Factory Service Manuals to learn the serial numbers of when such changes started and stopped. Since the Type 1 used SIX different engines over the years, and ALL of those included variations, the type vs displacement thingy is a handy way to determine if a person is just running their mouth or if they actually know something about VW engines. But that has little to do with converting a VW engine for flight since you should base your build on all new, universal replacement parts. ---------------------------------------------------------------------------------------------------- I wish they had made a 6 cylinder bug engine, with decent heads. *That would be a much better aero engine, me thinks. ---------------------------------------------------------------------------------------------------- They did. It's called the Corvair :-) -R.S.Hoover |
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On Jul 21, 11:47*am, erik wrote:
How about something more on the Type 4? ------------------------------------------------------------------------------------ Mostly because I don't consider myself qualified on them. I've converted a couple for flight and done my share of repairs on 411's and the like, but I've never had access to enough cores to do much in the way of experimentation. ----------------------------------------------------------------------------------- Most info on this engine seems to be " That is what the VW engine should have been" ---------------------------------------------------------------------------------- True enough. It incorporates all of the HVX mods, for example. Plus hydraulic cam-follwers. And it has already been converted & certified as an aircraft engine by Porsche. But it fails the test of Critical Mass: There aren't enough of them to trigger the investment & experimentation that leads to a race-winning combo. Mark Stephens devoted a lot of time to the engine's initial short-comings (bad valve seats, head seals, sodium-filled valves, etc) and fielded a number of race-winning cars with this engine. But having tooled-up to produce reliable heads and so forth, found the market simply wasn't there. My conversions of this engine were limited to the aviation-specific items: The engine mount, prop-hub, cooling system and so forth. For the mechanical components, I simply bought the parts from Stephen. The be fully qualified on the engine I would have tooled-up to do ALL of the engine-work in-house. That's the only way you can certain of the quality of the work. -R.S.Hoover |
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