As I recall, the turbocharger on the P38 took up a lot of space on top of each nacelle/tail fork. . It would have needed a large bulge on a P51, which was a much smaller plane.
Flintlock76 Overmod Although I confess it would have been interesting to see how the Allison engine might have fared if it had been properly supercharged for actual use in the aircraft it was intended for... Oh they tried, from what I've read they really tried, but it just didn't work out.
Overmod
Although I confess it would have been interesting to see how the Allison engine might have fared if it had been properly supercharged for actual use in the aircraft it was intended for...
Oh they tried, from what I've read they really tried, but it just didn't work out.
One reason is that the Allisons were more conservatively rated in that USAAF regulations required that the engine produce rated power for a longer period of time than the RAF. The book I have on Allison engines also stated that Allison was behind RR is dealing with backfires - not preventing them but limiting damage caused by the backfires.
Note that the P-38 DID have lots of high altitude power, but it was the turbocharged version of the Allison engine. A P-51 with a turbocharged Allison would have had 1/3rd more range/combat radius than the Merlin equipped P-51. The ultimate Allison would have been the turbo-compound with an sfc even lower than the Wright turbo-compound used on the DC-7s and later Connies. Take-off power would have been close to 3,000HP.
The Allison had fewer parts, something like 7,000 versus 12,000 for the Merlin and also had substantially fewer unique parts.
BALT:
The parts in the Packard built Merlins were required tobe interchangeable with the parts for the RR built Merlins, so the Packard built Merlins did not use SAE hardware.
From what I've learned, the Packard people used the RR plans and made improvements wherever they could both for performance and production. They had the capacity to build them quickly and reliably, better than Rolls-Royce could do. Remember that Packard was a mass production plant and Rolls built every car pretty much to order and they were not set up to mass produce like the American automobile companies could do.
Murphy Siding Overmod And damn right that it was the Packard, and not the Rolls-Royce, version of the engine that was cited. There are reasons... What are those reasons? Weren't they building off the same specs and blueprints?
Overmod And damn right that it was the Packard, and not the Rolls-Royce, version of the engine that was cited. There are reasons...
And damn right that it was the Packard, and not the Rolls-Royce, version of the engine that was cited. There are reasons...
What are those reasons? Weren't they building off the same specs and blueprints?
I think one set of blue prints was SAE and another was British Standard.
Never too old to have a happy childhood!
Thanks to Chris / CopCarSS for my avatar.
OvermodAlthough I confess it would have been interesting to see how the Allison engine might have fared if it had been properly supercharged for actual use in the aircraft it was intended for...
No matter, for certain applications the Allison worked out just fine, for example the P-38's and P-39's used in the Pacific where high-altitude performance wasn't a must, or the P-39's shipped to the Soviet Union as Lend-Lease aid. The Russians made very good use of those Allison engined P-39's as low-level ground attack aircraft. Russian pilots liked those P-39's, a lot!
Flintlock76Damn right.
I do think the 12-567/645 is up there too, and perhaps overall the 12-710 and its GEVO counterpart. Just in the 'attacked' and not 'attacking' column...
54light15 They had a survey a year or two ago that asked people what was the best V-12 ever made. The consensus was, the Packard-built Merlin.
Damn right. Nothing succeeds like success, right?
Those would have been Allison powered- notice the air intake above the prop-the later Merlin powered versions didn't have that.
You may be interested in a website called "Bring a Trailer" which is an auction site for vintage and newer cars. They had a survey a year or two ago that asked people what was the best V-12 ever made. The consensus was, the Packard-built Merlin. I totally agree with that.
54light15 Hermann sure liked to live large, didn't he? I've seen the Blue Goose at a show in Michigan. It's unrestored and painted a blue metallic with one-inch thick windows, one of which has a bullet mark. Likely someone from the 101st Airborne who captured the car and wanted to see just how bullet proof it was. There are stencils from the 101st on the bumpers too. Also, the car at 6:06 (and later on) is a 1937 Buick convertible sedan.
Hermann sure liked to live large, didn't he? I've seen the Blue Goose at a show in Michigan. It's unrestored and painted a blue metallic with one-inch thick windows, one of which has a bullet mark. Likely someone from the 101st Airborne who captured the car and wanted to see just how bullet proof it was. There are stencils from the 101st on the bumpers too. Also, the car at 6:06 (and later on) is a 1937 Buick convertible sedan.
Dr. Felton's got a video on "The Blue Goose" as well.
https://www.youtube.com/watch?v=sAf1fYawXNo
Interesting newsreel featuring those RAF Mustangs! I wonder if they still had the Allison engines or had been upgraded to the Rolls Royce Merlin by that time?
Here's a good one with Mustangs:
https://www.youtube.com/watch?v=AmShtLOmwrA
BEAUSABRE The code name for Hitler's train was, believe it or not, Amerika !
The code name for Hitler's train was, believe it or not, Amerika !
Hermann Goering had a train of his own, called "Asien," or "Asia."
Have a look:
https://www.youtube.com/watch?v=nMc3Kw9aNEs
Flintlock76Bringing this thread back for a bit. Remember the B-17 crash in Windsor Locks CT back in 2019? I found a video giving the "whys and wherefores" of the event. It's a little bit dry, runs about 20 minutes or so, but does a good job explaining what went wrong and why. "The holes in the Swiss cheese all lined up." https://www.youtube.com/watch?v=y3p-hGR3ZyY
Remember the B-17 crash in Windsor Locks CT back in 2019? I found a video giving the "whys and wherefores" of the event. It's a little bit dry, runs about 20 minutes or so, but does a good job explaining what went wrong and why.
"The holes in the Swiss cheese all lined up."
https://www.youtube.com/watch?v=y3p-hGR3ZyY
Bringing this thread back for a bit.
https://www.youtube.com/watch?v=wVmMd2BnbJ4
Overmod: Found the engine starting sequence very reminding. Have no experience of the 3350s. For first start of R2800 was 5 complete rotations first ( 15 blades ) and for 4360s again 5 rotations ( 20 ) blades. Then ignition boost, prime, throttle, mixture. You always knew who was a new Captain or first officer on the Convairs or engineers on the Connies by the backfires you heard when starting those engines! It was a co-ordination exercise that just had to be learned. I was lucky. Had more than one Captain who would never start an engine but just count the blades.
You have no idea how busy the flight engineer on a Connie was during starts. In fact an engineer was considered not baptized until his first time sliding off the wing of a Connie while dip sticking the fuel tanks. Happened a lot during winter times. There were some ground persons who would follow you while you dip sticked.
Erik_MagPicture a standard turbocharger with an extension shaft from the compressor end. This shaft is then geared to a fluid clutch or torque converter which then is geared to the rear of the crankshaft. The second stage supercharger was also geared to the rear end of the crankshaft.
The problem is, try as I might, I can't find any reference that says the exhaust turbine used on the compounded V-1710 had an actual compressor installed on it; one reference says the turbine came from a turbosupercharger design but was explicitly reduced to producing torque only.
I will now have to find a copy of Vees for Victory and see what the detail actually is. This is not so bad as I can get the poop on the yet more interesting V-3420-B (and the possibilities of its turbocompounding!) in the same place...
The Wright TC had three PRT's, each of which was good for ~300 hp for a total of 800 to 900 hp. The PRT's were spaced 120 degrees around the rear of the engine and power was transmitted through a fluid coupling and then some sort of 90 degree gearing to the crankshaft.
For those of you who are engine-porn aficionados, here is something of interest: the magic starts around 3:56. The key here is to listen for the turbine lag as the power comes on and off...
Overmod Erik_Mag Unlike the Wright TC's, the turbine was connected by a shaft to the impeller of the first compressor stage. Can you be a bit more specific (or link to drawing(s) or specific sources?
Erik_Mag Unlike the Wright TC's, the turbine was connected by a shaft to the impeller of the first compressor stage.
Can you be a bit more specific (or link to drawing(s) or specific sources?
Source: pg 388 of "Vees for Victory!" by Daniel D. Whitney (c) 1998, Schiffer Publishing Company.
Picture a standard turbocharger with an extension shaft from the compressor end. This shaft is then geared to a fluid clutch or torque converter which then is geared to the rear of the crankshaft. The second stage supercharger was also geared to the rear end of the crankshaft. Note that a good fraction of the V-1710 production was used in P-38's where one engine was turing in the opposite direction of the other. Allison used the same cranshaft for both, flipping the fore/aft cranshaft ends between the two engines.
Development of the Allison TC was dropped partly because of the limited market for liquid cooled aircraft engines as well as the supplier of the exhaust turbine, GE, wasn't putting much effort into development.
The "low sfc" project for the R4360, was the Variable Discharge Turbine. The gist was that "throttling" was done by using a nozzle to constrict the flow from the exhaust turbine. Some rather spectacular claims were made for range and service ceiling improvements for the B-36, but the increase in cooling fan power negated much of that. Would have been interesting to see what it could have done in the Republic Rainbow.
Liquid cooled engines will often have a low sfc as the liquid cooling allows for lower cylinder head temperatures which then allows for a higher compression ratio. Note that the Allison V-1710 had 4 valves per cylinder.
CSSHEGEWISCHAlthough the gearing worked to allow turboprop operation at higher speeds, the propeller blades were so long that the tips were supersonic (noisy).
I wonder if the blade configuration used for the Starship would produce lower noise if scaled appropriately for 'one of four' geared turboshafts of appropriate shp?
Somehow, I don't think that the turboprop design of the Tu-95/Tu-114 would have made the cut in Western airline service. Although the gearing worked to allow turboprop operation at higher speeds, the propeller blades were so long that the tips were supersonic (noisy).
BaltACDTry uBlock a extension for Chrome.
I've been resolutely trying not to jump on the Adblock Bandwagon in what is probably a misguided and laughed-at attempt to allow Kalmbach as much technical compensation for providing the forums free as possible. It is almost at the point that I give up, since within the past three weeks or so ... seemingly from right after the mysterious lapse in being able to access the ability to post while being logged in for everything else (specifically including ad serving) ... it has become impossible not to click on one ad or another from time to time when pulling up threads. The content bounces up and down, ads bloom from overhead without warning, they pop up below and then balloon if moused over, and there is no mechanism for editing out 'mistaken clickthrough' to particular sites, or reviewing exactly what content is supposed to be "interesting" to me based on back-end extraction of the things I 'click to visit' (as opposed to things I'm tricked into clicking) or the texts of things I post. I am not deceived, I have made a point of understanding SEO evolution and the various fun abuses of cookies since the early '90s when much of the cookie handling was largely undocumented function, and I am neither unaware of or amused at heavy-handed attempts to monetize "free" resources or communities.
I'm waiting as long as I can for the promised Brave New World of the revised 'community experience', where one way or another we'll see if Kalmbach 'gets it' for this formerly-important segment of their far-flung and successful media empire concept. But I'm not comfortably accepting the devolution in the meantime without comment, either.
OvermodI am beginning to really dislike how this site, and its dancing ads, and its delayed loading and page buffering, works with Chrome.
Try uBlock a extension for Chrome.
Moon man Borman was way after that. Maybe after 1976? The last recips were the Convair 440s that were gone by ~1971. Near the last year of CV-440s EAL had to expand their jet engine overhaul facility displacing the recip overhaul to a contractor. That really change our attitude when flying those contract engines. Never had 2 contractor engines on the CV-440s always checked if engine was a contractor engine to be nurse maided. As for the Connie freighter's engines unknown. With very little use probably had enough Connie engines until 727QCs retired the Connies.
EDIT AS for the Cs, 3350s and 1649s have no knowledge.
Yes the operating practices that were not in the airplane flight manual but were just bulletins often gets lost in the history books.
This is the kind of pure-gold information that would be hard to find anywhere else ... and will be increasingly hard as the edge of history sweeps across those who remember the era, and when the technology was cutting-edge...
I thought there were some Connies that got compounded 3350s, including the L1049C and 1649 Starliner, after 1953.
blue streak 1Told EAL had the highest recip MTBF of all the airlines.
I believe this is the approach proposed for 'turbocompounding' on the R-4360:
https://external-preview.redd.it/eAbL99dur5rCnxZrq_rW2IhKtGonaZCyP7XHwHh2XBg.jpg?width=960&crop=smart&auto=webp&s=41d75aa37a2a4faaebaad4add008fa1c21112e5d
.
I am beginning to really dislike how this site, and its dancing ads, and its delayed loading and page buffering, works with Chrome.
I was often told that the turbo compounding of the DC-7s caused some problems with overheating. They said that the -7s never could cool properly and often would swallow certain charger parts. Told that was the reason EAL retired their -7s before their -6s. Delta also did the same thing.
On the Connies the R4360s did not have that problem . When EAL started using the Connies on the shuttle the altitudes they usually operated were at no more than 13,000 or 14,000 feet. EAL actually operated them at lower BMEPs than their ratings for take offs, climb, and cruise except for emergencies. Also they used ADI for take offs. That also saved the engines. -7s only stayed on the shuttles for a couple months.
Those Connie power plants were very reliable with few failures. Never had a recip failure. EAL maintained their own recip engine overhauls for Connie R4360s and the R2800s for Martin 404s and Convair 440s. Told EAL had the highest recip MTBF of all the airlines.
Erik_MagUnlike the Wright TC's, the turbine was connected by a shaft to the impeller of the first compressor stage.
A turbocompound is a mechanical device, as you noted one that provides additional torque directly to the engine mainshaft. Why would the turbine providing this be coupled to an 'impeller' of a 'compressor' unless the torque were being transferred hydraulically rather than through planetaries and clutches -- something that to me makes little engineering sense in terms of what turbocompounding on aircraft is supposed to provide? My current understanding of the arrangement is that the turbine shaft ran through the first-stage supercharger impeller (i.e. through a hollow shaft) to reach physical connection with the crankshaft, as in this quote from an online reference:
The shaft from the turbine ran through the centre of the first stage supercharger impeller, back to the engine and put its power directly into the crankshaft. The turbine could not be connected to the supercharger impeller because the supercharger was driven by a variable speed transmission, which did not run at a fixed speed ratio with respect to either the crankshaft or the turbine.
The fuel-economy advantage of turbosupercharging over mechanical supercharging has been well-established almost since the first use of exhaust turbines for the purpose, and as you know is readily established from practical equivalents of the Carnot cycle for internal combustion. To my knowledge the use of pressure charging in that era was more to maintain 'sea-level' engine performance at higher altitude, much as GM actually did with the turbo on the 6.5TD in stock configuration, with performance retention rather than 'power adding' being the criterion (this certainly seems to be the rationale behind two-speed supercharging of the Merlin as designed). Just as the ihp of steam engines increases with altitude, so does the advantage of exhaust-gas turbine compression of intake air relative to decreasing required back pressure across a turbine compared to mechanical shaft drive providing an equivalent mass flow of combustion air.
I won't pretend to second-guess engineers who, calculating a given amount of recoverable heat in engine exhaust, prioritized augmented physical torque as a 'first stage' followed by turbosupercharging, as opposed to using just the amount of gas energy to 'make up' combustion reuirements moment-to-moment and then recovered 'the rest' as torque (as in some of the roadgoing exhaust-turbine approaches). But I would like to see if the turbocompounded V-1710 in particular used staged or sequential expansion in one order or the other, and how much available energy was recaptured in each 'part' in different operation regimens.
I suppose I'd settle for a readable copy of the 1949 SAE report on 'compound powerplants' (my reference says #490226) which covers both the detail design and specific reasons why it was not pursued (likely more bang for the buck in straight turboprop combustion turbines). I have some access to JSTOR but cannot find this particular paper digitized and accessible through them.
(Incidentally, when I first looked at the specs for the turbocompound engines in late airliners, the contribution from the exhaust turbine unit was supposed to be around 300shp. The modern references show a much larger amount -- approaching 800shp but with substantial flown-weight increase per engine. Which is correct?)
Overmod Erik_Mag Getting back to the origins of the Connie: The 300+ mph cruise speed was made possible by the Wright engines developed for the B-29, though one interesting "what-if" was the turbo-compound Allison V-1710 good for almost 3,000hp at take-off. The sfc of the tubocharged V-1710 wasn't much higher than the Wright turbo-compounds, so a non-stop NY to LA flight would have been easy Did Allison develop a turbocompound V-1710? It doesn't seem to me there is any good place to put the required transmission (at either end of a V-16 driving a propshaft) while maintaining the required exhaust-header balance to use, say, the arrangement in a Wright turbocompound (which is easier and more direct on a radial). I suspect you mean 'turbosupercharged' and not 'turbocompounded' which is a very different thing. I do confess it would be interesting to see the effect of crankshaft-coupled exhaust compounding on the sfc of an (otherwise correctly pressure-charged at altitude) V-1710...
Erik_Mag Getting back to the origins of the Connie: The 300+ mph cruise speed was made possible by the Wright engines developed for the B-29, though one interesting "what-if" was the turbo-compound Allison V-1710 good for almost 3,000hp at take-off. The sfc of the tubocharged V-1710 wasn't much higher than the Wright turbo-compounds, so a non-stop NY to LA flight would have been easy
Did Allison develop a turbocompound V-1710? It doesn't seem to me there is any good place to put the required transmission (at either end of a V-16 driving a propshaft) while maintaining the required exhaust-header balance to use, say, the arrangement in a Wright turbocompound (which is easier and more direct on a radial). I suspect you mean 'turbosupercharged' and not 'turbocompounded' which is a very different thing. I do confess it would be interesting to see the effect of crankshaft-coupled exhaust compounding on the sfc of an (otherwise correctly pressure-charged at altitude) V-1710...
Allison started looking into turbo-compounding ca 1940 and built a prototype in 1945. Coupling between the exhaust turbine and crankshaft was at the rear of the engine, with a fluid clutch and reduction gear. Exhaust plumbing would have been similar to the P-38. Unlike the Wright TC's, the turbine was connected by a shaft to the impeller of the first compressor stage. SFC at ~1400hp and 26,000' was 0.365 lb/hp-hr, which I believe was better than the Wright TC engines (0.38 - 0.39lb/hp-hr??)
On a somehwat related note, had the P-51 been equpped with a turbocharged V-1710, it would have had about 30% more range than the Merlin powered P-51's. Top speed may have been slightly less as both the Allison powered and Merlin powered P-51's used exhaust energy to provide thrust.
The above data is from the book "Vees for Victory", which covered the history of Allison up to ca 1948. I got my copy late January from Karen's Books, been wondering about the story behind the V-1710 versus the Merlin for the Mustang - first read about that ca 1964 in the American Heritage book about the Air War over Germany.
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