Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: earl1937 on October 11, 2013, 02:06:27 PM
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:airplane: I ran across a couple of u-tube video's of WW2 type radial engines which I thought you guys might enjoy seeing.
http://www.youtube.com/watch?v=EyPvpdy4dgg This is the same engine which is in the F4U series of aircraft. A good explanation of the working parts and etc.
The next video shows how the radial works, when viewed from the front. See if you can figure out which is the "master" cylinder and which are the slaves.
http://www.youtube.com/watch?v=HGKXdYCksAQ
Some may ask, "well, what is the benfit of this info in Aces High? My answer would be: If you are a aviation nut, the more you learn, the better the pilot you would be, both in RL and AH!
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is that a planetary reduction gear at the front end?
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is that a planetary reduction gear at the front end?
:airplane: All radial engines had a reduction gearing system in the nose section. The props never turn the same as the RPM, except fixed pitch props, and the only one of those in this game is the Storch.
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Why did Great Britain go with the sleeve valve when we were getting good results with poppet valve? Or is that like asking why we drive on different sides of the road?
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Why did Great Britain go with the sleeve valve when we were getting good results with poppet valve? Or is that like asking why we drive on different sides of the road?
left is the right side !
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left is the right side !
I thought I read somewhere that's biologically due to right eye dominance.
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Why did Great Britain go with the sleeve valve when we were getting good results with poppet valve? Or is that like asking why we drive on different sides of the road?
In England it was mainly Harry Ricardo's work on this is design. The first British tank had one of his sleeve-valve engines in it. We weren't getting good results with poppet valves, they were all plop back then. It's a Betamax / VHS thing. The poppet valves just ended up having more development work and once you reach that certain tipping point other designs, even arguably superior ones, tend to get abandoned.
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One of the reasons for going with sleeve valves before the war was to prevent knocking associated with poppet valves. As it turned out the development of high octane fuels helped cure this problem for conventional engines anyway, but the designers weren't to know this at the time. Sleeve valve engines gave very good performance and were eventually made reliable too. Their main hassle was in mass producing them, a problem that wasn't given sufficient attention in Britain pre-war.
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One of the reasons for going with sleeve valves before the war was to prevent knocking associated with poppet valves. As it turned out the development of high octane fuels helped cure this problem for conventional engines anyway, but the designers weren't to know this at the time. Sleeve valve engines gave very good performance and were eventually made reliable too. Their main hassle was in mass producing them, a problem that wasn't given sufficient attention in Britain pre-war.
:airplane: One main reason the U.S. engine producers used the valves in their engines was one of "cooling"! They found it was easier to cool the poppet valves and was less a problem with warping filling the insides of the valves with "sodium". Might be other reasons as well, but that is what I was always told by AF engineering officers. I am not sure, but I think the sleeve type valve had a solid stem, which if the engine over heated just a little, they would warp!
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:airplane: One main reason the U.S. engine producers used the valves in their engines was one of "cooling"! They found it was easier to cool the poppet valves and was less a problem with warping filling the insides of the valves with "sodium". Might be other reasons as well, but that is what I was always told by AF engineering officers. I am not sure, but I think the sleeve type valve had a solid stem, which if the engine over heated just a little, they would warp!
Earl,sleeve valve engines don't have valve stems,they use ports in the sleeve,much like you find on a 2stroke engine. The sleeves usually move up and down but can also rotate,depends on the design and application.
The sodium not only cools the valve it also reduces the weight over a solid stem,I always wondered why no one made a desmonic drive valve train in aero engines!
:salute
PS: maybe they did and I'm just not aware of it!
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http://www.youtube.com/watch?v=_vrvep_YOio
Bristol Hercules sleeve valve radial animation
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Especially the exhaust poppet valves are a problem. Actually poppet valves are pretty cack if you look at the gas flow, but you can see how much superficial development has been done if you look at the revs of a modern formula 1 car.
One of Harry Ricardo's motivations for working on the sleeve valve was the upper limit of output he foresaw with the poppet valve. The ports of the sleeve valves make for much easier aspiration. With modern materials you could make a really nice engine. But no one's going to bother now, the end of the piston engine is arguably in sight. :cry
I've got a very rare book somewhere hereabouts entitled 'Some Unusual Engines'. Took me seven years to track a copy down and cost a lot of money. I can post some of the material if anyone's interested. Went out of print years ago.
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Please post. I'd never seen sleeve valves like the ones in that animation until now.
How well did they seal? I would have thought that the interstitial space would be subject to scorching and loss of effective lubrication. Also does the piston block the valve port on part of its stroke.
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If sleeve valves were better, i think that they'd be used predominantly.
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See if you can figure out which is the "master" cylinder and which are the slaves.
I give up. Which one and why. :bhead
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The one connected to the master rod. Earl I have a vague memory that the master rod was a late night stroke of genius on the part of an engineer at p&w or wright but I can't remember, any info?
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If sleeve valves were better, i think that they'd be used predominantly.
Define better. That can often just mean cheaper. The only thing that really replaced the Bristol series of aero engines was gas turbines. Compared to 'standard' radials they had a higher BMEP, lower fuel consumption at higher power settings and a service life three times longer.
Sure they had their drawbacks, so do poppet valve engines. There was possibly a point where it could have gone either way but the poppet valve won out.
Please post. I'd never seen sleeve valves like the ones in that animation until now.
I wrote a sort article in the Bristol Beafighter thread.
http://bbs.hitechcreations.com/smf/index.php/topic,255408.msg4388164.html#msg4388164
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Here is a clearer video of a cutaway engine running in demo:
http://www.youtube.com/watch?v=Liqqo8Cdb68
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The one connected to the master rod. Earl I have a vague memory that the master rod was a late night stroke of genius on the part of an engineer at p&w or wright but I can't remember, any info?
:airplane: You real close and I am not sure which engine producer, Wright or P&W were the ones to finally produce a smooth running, very reliable radial engine first.
If you will look at the front view, showing the cylinder's and pistons moving up and down, the cylinder at 12 O'clock position is the master rod and all the others are slaves. If the cylinders and rods were arranged like a 6 or 8 cylinder auto engine, with a "crankcase" "throw" for each cylinder, the thing would be huge! But when Wright or Kinner or P&W finally came up with the Master cylinder arrangement, a lot of size problems went out the window. Then to make a more powerful engine, they just added another "bank" of cylinders, again one with a master rod and you had the makings of a lot of the more powerful, yet small size engines, suitable for aircraft applications. They, the engine manufacturers, all settled on the 7 cylinder bank as the most desireable. The P&W R-4360 was the largest of the radial engines ever mass produced. They were used in the B-36, C-97's, KC-97", B-50's, C-119's and one model of the F4U aircraft. I am sure I have missed some that had that big old engine, but don't come to mind right now.
(http://i1346.photobucket.com/albums/p684/earl1937/800px-Pratt_amp_Whitney_R-4360_Wasp_Major_1_zps35929bd4.jpg) This is a pic of the R-4360
(http://i1346.photobucket.com/albums/p684/earl1937/220px-Ranger_L-440_zps9f96ceb6.jpg) This is a pic of the old Ranger inverted engine, which had a crankcase throw for each cylinder.
(http://i1346.photobucket.com/albums/p684/earl1937/Aircraft20Engine20Cutaway_zps49cf537b.jpg) This is a "see through" of a R-2600, twin row, (2 banks of 7 cylinder's each), and the difference in this and the R-2800 in the F4U's and many other fighter aircraft produced by Grumman, the cylinder's were a little larger, hence the difference in 2600 cubic inches cylinder displacement and 2800 cubic inches of cylinder displacement. Now, there were certainly a lot of other differences in the two engines, but the basic crankcase, nose section, and accessory sections were very similar in their layout.
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Here is a clearer video of a cutaway engine running in demo:
http://www.youtube.com/watch?v=Liqqo8Cdb68
:airplane: Not sure what kind of cylinder that is shown in this video, but it is not a aircraft engine which I am familiar with, as it has a moving sleeve inside the cylinder!
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:airplane: Not sure what kind of cylinder that is shown in this video, but it is not a aircraft engine which I am familiar with, as it has a moving sleeve inside the cylinder!
It's a Bristol Hercules. The Beaufighter used these ones (also).
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:airplane: Not sure what kind of cylinder that is shown in this video, but it is not a aircraft engine which I am familiar with, as it has a moving sleeve inside the cylinder!
The title says Le moteur Bristol Hercules
http://www.youtube.com/watch?v=_vrvep_YOio (http://www.youtube.com/watch?v=_vrvep_YOio)
From Wiki, a/c that used the Hurc
Armstrong Whitworth Albemarle, Avro Lancaster B.II, Avro York C.II, Bristol Beaufighter, Bristol Freighter, Bristol Superfreighter, Breguet 890 Mercure, Fokker T.IX, Folland Fo.108, Handley Page Halifax, Handley Page Hastings, Handley Page Hermes, Nord Noratlas, Northrop 8A (One Swedish 8A-1 was bought by Bristol to test the engine), Northrop Gamma 2L, Saro Lerwick, Short S.26, Short Seaford, Short Solent, Short Stirling, Vickers Valetta, Vickers Varsity, Vickers VC.1 Viking, Vickers Wellesley, Vickers Wellington
sleeve valve engines , Crecy (2 stroke v12) and Sabre (4 stroke h24)
http://www.youtube.com/watch?v=LgiPv5uPX-M
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Being interested in different valve designs I find the sleeve valve an interesting exception since the engine business tends to stick with cheapest and on the other hand technologies which offer best performance and the poppet valve is in many ways an optimal design -yet not necessarily the most optimal performance wise.
When the four stroke engine was young the valve technology was give some serious thought:
http://www.douglas-self.com/MUSEUM/POWER/unusualICeng/RotaryValveIC/RotaryValveIC.htm#crs
More recent application:
http://home.people.net.au/~mrbdesign/PDF/AutoTechBRV.pdf
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Define better.
More specifically what I mean is that if sleeve valves were any of these on average -- cheaper without regard to performance, higher performance without regard to cost, or lower in cost/performance -- they would be used a lot. Lots of piston automobile engines, boat engines, aircraft engines, lawnmower engines, generator engines, pump engines, and motorcycle engines are made under any of those metrics. Take just a couple of these categories -- cars and motorcycles. There are many examples of those made to be as cheap as possible, ones made as high performance as possible without regard to cost, and ones made with cost/performance in mind, and none or nearly none of them have sleeve valves, and that includes the whole range of engine sizes from radio-controlled airplanes to lawn mowers to motorcycles to cars to construction/excavation equipment to ships to enormous ships.
It also is not a result of design inertia, I can tell you from having worked for several years at Chevy Engineering (the portion of Chevy that was responsible for, among other things, engine design for commercial vehicles, speculative future designs, and for some racing applications such as, depending on the time period, Indy, Grand Prix, and Nascar). There was not huge design inertia -- if it provably worked better for engines, it could get adopted. That's how historically things went from push rods to overhead cam, from 2 valves per cylinder to four, from carburetors to fuel injection, from steel to aluminum, etc. All sorts of engines have been tried out historically in just cars alone -- two stroke, diesel, otto, turbines, electric, hybrid, steam, sterling, inertial energy storage, 8 cylinder, 4 cylinder, V, opposed, Wankel, air cooling, liquid cooling, superchargers, turbochargers, etc., using steel, aluminum, ceramics, plastics, and various other alloys. What we have today is the result of a huge amount of experimentation and optimization.
If sleeve valves were on average better in some way (take your pick of any way at all), I think they'd be used a lot more. If they were better somehow in performance (regardless of cost), you'd see them in racing engines for cars, boats, or motorcyles. If they were cheaper (even if crappy in performance), you'd see them in some car engines or at least some lawn-mower engines or some pump engines. If they were better in cost/performance (where performance could be HP or emissions or weight or gas mileage, etc.), you'd see them in car engines.
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"If they were better somehow in performance (regardless of cost), you'd see them in racing engines for cars, boats, or motorcyles."
Well, see what happened to BRV application -FIA banned its use. Usually racing and war technology go hand in hand and those technologies tend to pave way to consumer use, unless somebody forcibly decides otherwise.
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"If they were better somehow in performance (regardless of cost), you'd see them in racing engines for cars, boats, or motorcyles."
Well, see what happened to BRV application -FIA banned its use. Usually racing and war technology go hand in hand and those technologies tend to pave way to consumer use, unless somebody forcibly decides otherwise.
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True -- racing rules can ban otherwise superior technologies, but there are lots of different types of racing, all with different rules bodies. Something banned in Formula 1 is just one venue, and I still think that history is on the side of superior applications tending to make it into commercial applications. It can take some time, of course.
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The 1 advantage a sleeve valve engine has over a poppet valve is pre-ignition.
You can use higher MAP's with lower quality fuels and not have to deal with overheat exhaust valves igniting the mixture. I suspect that was the reasoning behind using it in aero engines.
The design is to complicated and complex to warrant use in automobiles,add in fuel development and computer controlled engine management and it just isn't cost effective,whether it's superior or not.
:salute
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Cool videos. :aok
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At Udvar-Hazy Center in Dulles, there is a cutaway of a Pratt & Whitney Wasp Major R-4360-59B http://airandspace.si.edu/collections/artifact.cfm?object=nasm_A19790005000 (http://airandspace.si.edu/collections/artifact.cfm?object=nasm_A19790005000) I am pretty sure it moves like the video you posted. Talk about a mean engine for the time.
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At Udvar-Hazy Center in Dulles, there is a cutaway of a Pratt & Whitney Wasp Major R-4360-59B http://airandspace.si.edu/collections/artifact.cfm?object=nasm_A19790005000 (http://airandspace.si.edu/collections/artifact.cfm?object=nasm_A19790005000) I am pretty sure it moves like the video you posted. Talk about a mean engine for the time.
:airplane: That cutaway is also on Pratt & Whitney's web site as a historical display! You know, I was thinking of all the "brain" power that went into the design of this great engine, 28 cylinders, 4 master rods and 24 "articulating" rods, 112 valves, a carburetor which as big as most 2 PC's put together, with 5 decks and pressurized to boot. I got to prowl over one of these big engines one day at Biggs AFB in El Paso, Tx, and curiosity, I had to look at every thing I could! Fuel lines was big as 1 inch in diameter going to the engine, magneto's big as 2 metal lunch boxes and spark plugs as big as a small flash light! Wow, to bad they had to go and invent the jet engine! :O At any rate, was a great engine and :salute to the guys and gals who made it happen! :cheers:
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Hey Earl I seem to remember reading a display placard on a big multi row radial at Evergreen's museum that said that you could shut down a perfectly good engine and next time you went to start it there'd be something wrong with it. Also it said or implied that the cost per hour was really high compared to turbines. Got any comparisons between the last and biggest piston engines and the early turbojets or turbo props?
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Hey Earl I seem to remember reading a display placard on a big multi row radial at Evergreen's museum that said that you could shut down a perfectly good engine and next time you went to start it there'd be something wrong with it. Also it said or implied that the cost per hour was really high compared to turbines. Got any comparisons between the last and biggest piston engines and the early turbojets or turbo props?
:airplane: I just don't know, I just know that we flight planned the 29 at 300 gal per hour, just for flight plan purposes, but we always had plenty of fuel left when we would rtb. I would hate to guess what that R-4360 burned per hour, but had to be at least 80 gal per hour times 6 is 480 gal per hour. Then you throw in the J-47 jets on the B-36, wow, don't have a clue. I know on the 29, we had around 16 hours maintenance for each hour flown, but that counted regular sch maintenance as well as on demand when parts broke.