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Profanity does not help your case, Meplat.

 

Denial/dIsmissal of listed merits - presented by a distinguished design engineer - as ad hype, like-wise.

 

Gear drives, once set - keep time, like clockwork, & make regular pushrod OHV valve clearance checks - redundant.

 

 

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8 minutes ago, M.B-5 said:

Profanity does not help your case, Meplat.

 

Denial/dIsmissal of listed merits - presented by a distinguished design engineer - as ad hype, like-wise.

 

Gear drives, once set - keep time, like clockwork, & make regular pushrod OHV valve clearance checks - redundant.

 

 

It defeats your earlier parroted nonsense about it being "simpler", for fuck's sake.

Regular inspection is needed regardless, because there is no place to pull over.

 

Fuck it, here-

I present to the jury, a cutaway of the supposedly "simpler" sleeve valve engine.

 

https://i.imgur.com/LxvuThc.jpg

 

And here is the timing gear for a 2800.

 

https://i.imgur.com/iVm2ocL.jpg

 

And to further illustrate the level of "gears for gear's sake"  involved with the two row sleeve valve radial, here is a

cutaway of a Wright turbocompound.

Note that even it's construction is simple, compared to the Bristol offering.

https://i.imgur.com/O03ByZW.jpg

 

Sleeve valve radial aircraft engines are hard evidence of "TANSTAAFL" in operation. You may have some very pretty looking jugs, but your belly is a watchmaker's wet dream.

 

 

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Link to download for Tempest V pilot's manual; https://www.dropbox.com/s/d00qe9vl3sdkdxj/TempestV PilotNotes.pdf?dl=0

And an R-2800 maintenance manual, which is a bit more comprehensive; https://www.dropbox.com/s/y820691i8di5zwl/Pratt Whitney Maintenance Manual_ Double Wasp R-2800 CA Engines.pdf?dl=0

Also, if you can't handle some profanity, well, this might not be the best place for you.

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No LC, I can "handle" them bad words.

 

Shit, I've heard 'em all before, but the point is, Meplat's emotive response aint a substitute for understanding.

He still has to grasp the difference between arrangements of multiple gear sets & the concept of "complexity".

 

Yes, the gear set complex looks "busy",

but compared to lifters/pushrods/rockers/poppet valves 'n' springs all bouncing around, jerking out of adjustment,

- it is an accurate, durable, trouble-free set-up.

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Just now, M.B-5 said:

Shit, I've  heard 'em all before, but the point is, Meplat's emotive response aint a substitute for understanding.

He still has to grasp the difference between arrangements of multiple gear sets & the concept of "complexity".

 

Yes, the gear set complex looks "busy",

but compared to pushrods/rockers/poppet valves 'n' springs all bouncing around, getting out of adjustment,

- it is an accurate, durable, trouble-free set-up.

It looks busy, because IT IS.

You are attributing all  kinds of mechanical doom and gloom to to a series of aircraft engine that has a superb operational record,

while dismissing the problems associated with the sleeve valve designs with a wave of the hand.

 

Like "Oh, we need to change a cylinder assembly in a hurry, lest the wily Nipponese bomb our airstrip".

Or why having two reciprocating assemblies in the cylinder of an internal combustion engine is a bad idea.

 

"Bouncing around".. the days of atmospheric intake valves were long dead by the time the first 2800 left the line.

They are STILL" bouncing around" while sleeve valve engines are at best, museum pieces.

  Huh, maybe the old 2800 (and other mere poppet valve radials) are not as bad as you're inferring..

 

But hey, don't mind me, I just used to work on them.

 

 

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9 minutes ago, Xlucine said:

A minor benefit, but a sleeve valve engine with the timing wrong is probably not going to start. A poppet valve engine, OTOH, will make expensive jangling noises when you turn it over.

 

It'll run, but you'll have a dead jug(s).

 

On the other hand it takes a concerted effort to get the lash so far out on a Pratt to get the piston to hit the valves. 

As in you REALLY have to be special.

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22 hours ago, M.B-5 said:

 

"...drop tanks behind the pilot..."

 

Yeah, sorry to be a grammar Nazi, J_G_T, but that's a real lousy sentence.

 

& sleeve-valve engine oil-consumption was certainly better than the big US radials, with their loose clearances

plus a multitude - of leaky joints...

 

The P-51 was not only much more fuel efficient/aero-slick than the R-2800 powered gas-hogs,

_ its cruise speed was ~ 100mph faster.

 

Funny that both the P-51 & P-47 were deemed worthy of significant revision (despite being in high demand),

but the P-38 wasn't, - due to the Lockheed being fairly close to being past its 'best by date' - by USAAF appraisal/reckoning.

 

& the German forces were a far more effective/dangerous enemy than those of Hirohito,

just as the USAAF losses lists - clearly show.

 

 

 

Oh, so we should treat you like an idiot who can't read English very well, granted the sentence wasn't the best, but any normal person with second-grade education should have no issues?  The picture should have helped you out as well,  maybe you should slow down and actually read a thread before you jump in acting like your some kind of authority, then your posts might not generate so much disdain.  Another thing that would help you out, would be instead of acting like a douchebag and using the G-nazi thing to dodge admitting your error, you could have just said, 'my bad', I misunderstood.  

 

You also like to bounce around and avoid directly addressing peoples questions about what you've posted, and you've not posted much in the way of sources, and your posts have a real arrogant-know-it-all flare to them, that won't fly with some of the questionable opinions you've posted. Your Fanboying an engine that went nowhere and had a pretty limited effect on the war is doing you no favors.  Who gives a shit the RAF limped along with some WWII fighters because their nation was to broke to fully upgrade to jets? That doesn't make your Napier Sabre any more relevant to WWII.  I really hope the men restoring the Tempests with sabres in them take very seriously how complicated and unreliable the Sabre could be if not maintained properly, and no one restoring these aircraft qualifies as an expert, since the motors how been out of use for decades, before they actually take to the air in one. I'm not overly worried though, most knowledgeable people don't go around trying to beat people up with their knowledge, like people with self-esteem issues do, and are smart enough to not fly an airplane until they are sure the grenade in front still has the pin in...

 

Your opinion of what a gas hog is, well it seems a little off, this makes you seem like fanboy, and this is another place where you changed your argument from GPH to cruise speed. ..  The Corsair could land on Carriers and the Mustang couldn't, so you're wrong, see how that doesn't work?  Try actually answering a question. If you look at the GPH ratings and compare the Merlin the R2800 on test stands, they have very similar min and max GPH, and the Corsairs higher GPH consumption at higher power makes sense in it was a lot bigger. If you want to talk about who had the speediest and most fuel-efficient cruise then the Mustang wins, but you still don't because of your argument changing ways. 

 

No one gave a shit about mustang production until the Merlin got put in it. You can harp all you want about how the Brits loved the MK1, but the US wasn't overly concerned about a cheap replacement for the P-40, the P-38 was just fine at the time. Later, when the Merlin woke the design up, and it was more the supercharger than the Merlin since the Merlin was fairly mediocre V12, but still the Merlin in the Mustang was the savior the 8th Needed to save them from their own stupid ideas and incompetence. When the Merlin Mustang went into production, they built a second factory but other than the B to D changes the Mustang didn't need a lot of major upgrades. The reason for this wasn't that the P-51 was some super design, it was it benefited by all the planes made before it, and all the lesson learned on the early model 51s.  The P-47 was not as much of an Orphean, but it had to be forced on the 5th Air Force.  The 5th, when the got them, were concerned about the range and designed and manufactured drop-tanks locally to make the P-47 more useful in the long-range campaigns in New Guinea. Because it was not in high demand either, production line changes were less of a concern, and the early P-47s had some issues and needed the upgrades.

 

What really impresses me, is that an aircraft designed in the final years of the 30s, was so technologically cutting edge, and in spite of some serious problems with compressibility, stayed in production, from before the US entered the war, right up to the end, and still remained competitive to anything the Germans produced, with relatively minor upgrades. Sure the intercooler changes were big, but not so big the War Production Board refused to allow it. The P-38 played a major part in figuring out what compressibility was and how to solve it. It also stayed in front-line service to the end of the war and many pilots did not want to trade it in for the Spam Can, mostly in the Pacific, but it still a fact. Had they put the K into production, nothing the Nazi's had could have done anything but run away from it. The War Production Board refused this massive update because the secondary factory was not up and running yet, and the P-38 was deemed too important to the war effort to slow down, and good enough.  I guess you think they were wrong too huh?

 

At this point, I don't really care about your opinions on how the Nazi supermen were the bestest enemy and those subhuman Japs were just clowns and easy kills.  

 

Quote

No, the 109/190 readily exceeded the P-38's Vne in the dive, & like the P-51, didn't need 'dive flaps' to regain control.

 

The thick-winged Typhoon was still cleared to dive at a 525mph EAS limit, though the Tempest's 'high speed wing ' profile allowed a later onset of drag/extra control capability & gave another ~25mph advantage - across the flight regime , by comparison.

 

P-38 'buffet' - bad enough to cause structural damage - was noted by the USAAF as a fundamental problem.

 

The Tempest was very robust though, with an ultimate stress rating of 14G, rather more than the USAAF design max.

 

See: period drag/structure documents; http://www.ww2aircraft.net/forum/threads/structure-weight-data-and-drag-analysis.42716

2

 

I'll leave it to Coli to cover your first two 'points'

 

It's funny you cherry picked that out of your own source(the one below for the slow readers) but ignored the reports overall positive nature. It's also amusing you post this report since it blows your silly "but it didn't have a blown canopy" argument out of the sky. Very few P-38s broke up in compressibility dives, it was well known if you throttled back and waited until you got back down into thick air you could use the trim tabs to pull it out.  Structural damage from trying to force the controls when locked into a compressibility dive was not a P-38 only problem, a number of Mustangs had their tails rip off due to it. It also amusing the people doing the test and maintenance work struggled with the P-38, since they couldn't get it back together right. It's ok though, all the good P-38 mechanics were int he Pacific and MTO. The real reason the Air Force got rid of the P-38 as quick as they could when the war ended was that they were very expensive and complicated, and required more men and hours to keep in top flying shape. The Army Air Force faced the same budget cuts as the rest of the services and had to settle for the P-51 when the P-47N was a better aircraft. These are the reason the F-14 was killed off as well, not because it was no longer viable. Granted by the end, there were better airframes but no other airframe but the Spitfire was still relevant, and the Spitfire was feeling it's age much more than the P-38 was. 

 

 

If Tempest was so robust why were the elevators modified to reduce the forces they inflicted on its airframe? It's a good thing they had all those shitty typhoons to work out the bugs out of the airframe on, er never mind...

 

 

Quote

 Yet they sure did prove useful for the F4U & P-51 et al...

Lockheed didn't use the P-38's multi-framed canopy on their next fighter, the P-80, did they.

 

 

The USAAF deemed the P-38 as effectively passe`, & rather than 'polish the turd' - ordered the P-82, instead.

 

In fact, the USAAF had major concerns about the P-38's shortcomings as a fighter, in the intense combat ETO.

Summarized as:

 

"...airspeed limitations are low... ...tail buffeting... ...cause structural failure...

...definitely objectionable & hazardous.."

 

See full report here: http://www.wwiiaircraftperformance.org/p-38/p-38-67869.html

 

 

 

WARNING WARNING I covered some of the problems with this post on the P-38 above!!!! The REPORT linked in this quote is the one that talks about how great a plane the P-38 was.  WARNING WARNING!

 

(Put in place for the slower readers)

 

I can't fucking believe you're still going on about the P-38 needing a bubble. For fuck sake dude, learn something, or at least shut the fuck up about it. Your own source proves your stupid opinion on this wrong. How old are you? No one will respect you, not on this forum or in real life if you can't admit you're wrong when the truth is looking you right in the eye and giving you the middle finger. 

 

And of course the P-38 was dropped at the end of the war, the design was 6 years old you twat.  That you don't get that the P-38 was competitive to the end when it was a late 30s design makes you look like one of those people who just can't ever get the truth through their heads once they have convinced themselves their ideas are brilliant. Oh and hey, did you know the P-82 dropped the Marlins and put V1710s in, and they put out more horsepower than the Merlin by a large margin? And no, it's not because of Merlin licensing costs or other such bullshit, the Allison V1710 was a better V12. 

 

 

And yeah exaggerate the report to back you own bullshit while ignoring the shit that proves your other arguments wrong lol 

You earned the snark in this post by walking in like an arrogant little prick and picking a fight.  You want a civil conversation, try removing the brick from between your ears and stop reading shit to confirm you own retarded opinions and pick an actually relevant airplane to fanboy over, or just actually learn something. 

 

 

 

 

 

 

 

 

 

 

 

 

 

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The 1710 also had a much stouter lower end, and used a pent-roof head, so tended to breathe better than the Merlin and Griffon.

 

It also has a really well thought out, modular valvetrain.

Image related-

1710 sectional

 

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Jeeze J_G_T, you've gone from a "2nd grade" incoherent sentence, to a veritable wall of inchoate blather! What a "twat".

You're "bouncing round" like a broken off valve head - on top of an R-2800 piston, it must be your "self-esteem issues", huh.

 

If anyone needs to "shut the fuck up" about the P-38, its you... 'polishing the turd' - simply serves no purpose.

& ranting abuse is no real substitute for actual primary source links, either, y'know.

 

Didn't you know that North American Aviation didn't want Allison engines in the P/F-82, but yeah, didn't get a choice in it..

GM ( who owned Allison) saw to that, & the Allisons never worked as well in the Twin Mustang, as the Merlin had, as it happens.

 

& the USAAF bosses, who'd invested so much into expensive turbo'd fighter powerplants were forced to admit it was a blind alley.

 

Neither P-38, or P-47 could catch an early P-51 at low level, let alone those diabolical Nazi V1 cruise missiles,

but Tempests could, & they stopped 800+ V1's - from crash diving into long-suffering Londoners.

 

Tempests went on to shoot down every type of FW longnose & LW turbo-jet - in service, & P-38's  didn't...

 

 

 

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28 minutes ago, Meplat said:

The 1710 also had a much stouter lower end, and used a pent-roof head, so tended to breathe better than the Merlin and Griffon.

 

It also has a really well thought out, modular valvetrain.

Image related-

1710 sectional

 

True Meplat, in those ways, & others, the Allison was a much better design,

& a smoother running, stronger, more durable engine, ( & in TBO) - in service.

 

R-R it appears, was very fortunate in having some excellent development engineers ( & sales team, as always) aboard,

to get that old-fashioned 'sows ear' of a typical old school 'nuts 'n' bolts' British engine - to work ( & sell) - as well as it did.

 

R-R's more innovative engines - like the Vulture, never got anywhere, by contrast.

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17 minutes ago, Domus Acipenseris said:

Nice opinion piece there D.A., but can you post a real in-period Service Evaluation - which validates that "400mph" P-38 claim?

 

Here's one from late 1941, which can, & does - present an actual 400+ mph fighter, the Hawker Typhoon.

No wonder the RAF rejected the P-38...

 

http://www.wwiiaircraftperformance.org/typhoon/Typhoon_AFDU_Tactical_Trials.pdf

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28 minutes ago, M.B-5 said:

Jeeze J_G_T, you've gone from a "2nd grade" incoherent sentence, to a veritable wall of inchoate blather! What a "twat".

You're "bouncing round" like a broken off valve head - on top of an R-2800 piston, it must be your "self-esteem issues", huh.

 

If anyone needs to "shut the fuck up" about the P-38, its you... 'polishing the turd' - simply serves no purpose.

& ranting abuse is no real substitute for actual primary source links, either, y'know.

 

I'm curious: In the hypothetical event that I had to choose one of you to ban permanently from this forum, which of you do you think I would ban?  You, who've been here a day, or Jeeps, who is a founding member?

Tough one, I know. I'll let you think about it for a little bit.

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Hey boss, if you want to disregard your own "guidelines" - on behalf of your good ol' buddy, & purge me, for quoting him...

...its your call, for sure, even if it does stink of 'old boy priviledge' , & 'abuse of power',

- but yeah, I guess its the Trump era now, for sure, too - huh.

 

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2 minutes ago, M.B-5 said:

Jeeze J_G_T, you've gone from a "2nd grade" incoherent sentence, to a veritable wall of inchoate blather! What a "twat".

You're "bouncing round" like a broken off valve head - on top of an R-2800 piston, it must be your "self-esteem issues", huh.

 

If anyone needs to "shut the fuck up" about the P-38, its you... 'polishing the turd' - simply serves no purpose.

& ranting abuse is no real substitute for actual primary source links, either, y'know.

 

Didn't you know that North American Aviation didn't want Allison engines in the P/F-82, but yeah, didn't get a choice in it..

GM ( who owned Allison) saw to that, & the Allisons never worked as well in the Twin Mustang, as the Merlin had, as it happens.

 

& the USAAF bosses, who'd invested so much into expensive turbo'd fighter powerplants were forced to admit it was a blind alley.

 

Neither P-38, or P-47 could catch an early P-51 at low level, let alone those diabolical Nazi V1 cruise missiles,

but Tempests could, & they stopped 800+ V1's - from crash diving into long-suffering Londoners.

 

Tempests went on to shoot down every type of FW longnose & LW turbo-jet - in service, & P-38's  didn't...

 

 

 

 

 

You may as well just leave. 

 

You can't be bothered to source your bullshit.  You have pissed off just about everyone on the forum and still refuse to admit you were wrong, on ANYTHING! You whine when people are mean to you, after you start it, and then act like an asshole when people give you advice on how to be an adult.  You came onto a forum, frankly where the general aviation knowledge is over your head, poked a bunch of people in the eye with your attitude, made a reading comprehension mistake, no one else made, then acted like a child when it was pointed out,  said some more opinion based crap, with a few sources that do no back your own claims and then acted like an ass when it was pointed out. If you can't take people being snarky, learn to be polite, and for fuck sake, learn to admit your wrong. 

 

 

Playing up the "I don't understand the post" bullshit, is lame since I responded point for point, if you can't figure it out, you really are an idiot. Of course, that's the play you're going with, you think it makes you clever, but everyone else understood the posts just fine, so they conclude you are a drama queen who can't admit when he's wrong.  You are amusing though, Meplat and I haven't had fun batting around squeaky toy like this in years! I know you can't admit you are wrong, it's clear, you've got a Trumpian Ego,  but maybe after you've burned bridges here and on other forums you can take the advice to heart and actually improve yourself, you know so people can stand to be around you, and you might even be able to get laid without paying the Shepard for the best of his flock. 

 

 

What I'm saying is, you don't have to go through life being a douchebag, get that ridiculous ego in check, and stop acting like a know it all, when you really don't know much, and you might do ok in life. 

 

At this point, without posting a source for each of your outlandish or even credible sounding claims, you won't be taken seriously here, you've damaged your credibility with your behavior and I'm not sure you'll ever get it back if your not just outright banned for your antics in this thread when the Sturg checks back in. I'd almost say you were a troll, but your stuff is so, not clever, that would just be sad. 

 

All this assumes you are not actually mentally handicapped if that's the case, sorry bro, I don't like beating up on handicapped people, but it's really hard to tell, with your admitted reading problems and other mental issues.  

 

 

 

 

 

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Here's a question for the tech-heads.

 

The Merlin-powered P-82 'Betty Jo' - flew non-stop from Hawaii to New York, & in record time.

 

Could the Navy's R-2800 powered equivalent, the F7F - beat that time-to-distance record, or even fly that far, non-stop?

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J_G_T now thinks he's the big boss fish here! He claims to be the 'spokesman' for 'everyone' & is itchin' to wield the ban stick.

Can it be - his "self esteem/ego" has been so smalled-out by his own inability to back up his bullshit - or provide valid primary sources? 

 

Seems likely, well either that, or maybe - he's just a mean-as drunk...

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6 minutes ago, M.B-5 said:

J_G_T now thinks he's the big boss fish here! He claims to be the 'spokesman' for 'everyone' & is itchin' to wield the ban stick.

Can it be - his "self esteem/ego" has been so smalled-out by his own inability to back up his bullshit - or provide valid primary sources? 

 

Seems likely, well either that, or maybe - he's just a mean-as drunk...

 

 

You need a cross to nail yourself on?  

 

M.B-5 is going to crucify himself on the cross of the Napier savior to save the denizens of Sturgeon's house from the evil and demented JeepsGunsTanks!!!  All praise the new savior!!

 

In seven days he will rise to smite Trump with his mythical 3500 horsepower Sabre+3!!

:ridethebomb:

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Jeeps understands the temperament of the forum admin, as do I. We're fine with shit talking as long as you back your shit up. You obviously failed to read the forum guidelines on how to manage to fit in here.  IE, provide documents and quality content without commentary at first and ease your way into posting until you have a handle on how this place operates. Coming in and arguing with long time posters who have first hand knowledge of the topic isn't the way to make friends. or even quality enemies.

 

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20 minutes ago, M.B-5 said:

Hey boss, if you want to disregard your own "guidelines" - on behalf of your good ol' buddy, & purge me, for quoting him...

...its your call, for sure, even if it does stink of 'old boy priviledge' , & 'abuse of power',

- but yeah, I guess its the Trump era now, for sure, too - huh.

 

You think you're Han fucking Solo, but you're really Jar-Jar, buddy.

 

What you don't know is that Jeeps is the only reason you are still allowed around here. So maybe you should be nice to him, or at least keep him entertained.


 

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No, he's just echoing what everyone else is thinking and not saying.

 

Speaking as one of the members here who isn't a world war 2 everything expert, yet gets along just fine in this forum because I KNOW and accept that i don't know shit compared to these guys! I can safely say that this is an amazing place to pull up a chair and actually learn some stuff from people who know their stuff. They have happily answered my dumb questions on more than one occasion in very friendly ways, so it's safe to say that if you're triggering this sort of response it's because you're being a fucking douchebag.

 

 

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Just now, Belesarius said:

Jeeps understands the temperament of the forum admin, as do I. We're fine with shit talking as long as you back your shit up. You obviously failed to read the forum guidelines on how to manage to fit in here.  IE, provide documents and quality content without commentary at first and ease your way into posting until you have a handle on how this place operates. Coming in and arguing with long time posers who have first hand knowledge of the topic isn't the way to make friends. or even quality enemies.

 

Yeah fixed that for you.. L.O.L...

 

Actually boss, I tried to find your "guidelines" at your suggestion, using the 'search function' - but nothing doin'...

However, aint the whole 'grandmasters/mean-girls' clique, bend-over for initiation newbie,  schtick - kinda last decade, already?

 

I'll take the good ol' 'Pepsi Challenge' on the veracity of the sources I've linked - any day of the fungin' week.

 

(& how is it - that the likes of J_G_T gets to vent an angry abusive tirade, rather than actually try to debunk my assertions?

Is it because he's tried/failed, but can't admit it?) 

 

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      There are three BARS designs of note from Russia:

      AK-107/AK-108
       


      The AK-107 and AK-108 are BARS rifles in 5.45x39mm and 5.56x45mm respectively.  These rifles are products of the Kalashnikov design bureau and Izmash factory, now Kalashnikov Concern.  Internally they are very similar to an AK, only with the countermass and synchronizer unit situated above the bolt carrier group.


       

      Close up of synchronizer and dual return spring assemblies

      This is configuration is almost identical to the AL-7 design of the early 1970s.  Like the more conventional AK-100 series, the AK-107/AK-108 were offered for export during the late 1990s and early 2000s, but they failed to attract any customers.  The furniture is very similar to the AK-100 series, and indeed the only obvious external difference is the long tube protruding from the gas block and bridging the gap to the front sight.
       
      The AK-107 has re-emerged recently as the Saiga 107, a rifle clearly intended for competitive shooting events like 3-gun.
       

       
      AEK-971

      The rival Kovrov design bureau was only slightly behind the Kalashnikov design bureau in exploring the BARS concept.  Their earliest prototype featuring the system, the SA-006 (also transliterated as CA-006) also dates from the early 1970s.



      Chief designer Sergey Koksharov refined this design into the AEK-971.  The chief refinement of his design over the first-generation balanced action prototypes from the early 1970s is that the countermass sits inside the bolt carrier, rather than being stacked on top of it.  This is a more compact installation of the mechanism, but otherwise accomplishes the same thing.


       

      Moving parts group of the AEK-971

      The early AEK-971 had a triangular metal buttstock and a Kalashnikov-style safety lever on the right side of the rifle.



      In this guise the rifle competed unsuccessfully with Nikonov's AN-94 design in the Abakan competition.  Considering that a relative handful of AN-94s were ever produced, this was perhaps not a terrible loss for the Kovrov design bureau.

      After the end of the Soviet Union, the AEK-971 design was picked up by the Degtyarev factory, itself a division of the state-owned Rostec.



      The Degtyarev factory would unsuccessfully try to make sales of the weapon for the next twenty four years.  In the meantime, they made some small refinements to the rifle.  The Kalashnikov-style safety lever was deleted and replaced with a thumb safety on the left side of the receiver.


       
      Later on the Degtyarev factory caught HK fever, and a very HK-esque sliding metal stock was added in addition to a very HK-esque rear sight.  The thumb safety lever was also made ambidextrous.  The handguard was changed a few times.



      Still, reception to the rifle was lukewarm.  The 2018 announcement that the rifle would be procured in limited numbers alongside more conventional AK rifles is not exactly a coup.  The numbers bought are likely to be very low.  A 5.56mm AEK-972 and 7.62x39mm AEK-973 also exist.  The newest version of the rifle has been referred to as A-545.

      AKB and AKB-1


      AKB-1


      AKB


      AKB, closeup of the receiver

      The AKB and AKB-1 are a pair of painfully obscure designs designed by Viktor Kalashnikov, Mikhail Kalashnikov's son.  The later AKB-1 is the more conservative of the two, while the AKB is quite wild.

      Both rifles use a more or less conventional AK type bolt carrier, but the AKB uses the barrel as the countermass.  That's right; the entire barrel shoots forward while the bolt carrier moves back!  This unusual arrangement also allowed for an extremely high cyclic rate of fire; 2000RPM.  Later on a burst limiter and rate of fire limiter were added.  The rifle would fire at the full 2000 RPM for two round bursts, but a mere 1000 RPM for full auto.

      The AKB-1 was a far more conventional design, but it still had a BARS.  In this design the countermass was nested inside the main bolt carrier, similar to the AEK-971.

      Not a great deal of information is available about these rifles, but @Hrachya H wrote an article on them which can be read here.
       
       
    • By Collimatrix
      Tank design is often conceptualized as a balance between mobility, protection and firepower.  This is, at best, a messy and imprecise conceptualization.  It is messy because these three traits cannot be completely separated from each other.  An APC, for example, that provides basic protection against small arms fire and shell fragments is effectively more mobile than an open-topped vehicle because the APC can traverse areas swept by artillery fires that are closed off entirely to the open-topped vehicle.  It is an imprecise conceptualization because broad ideas like "mobility" are very complex in practice.  The M1 Abrams burns more fuel than the Leo 2, but the Leo 2 requires diesel fuel, while the omnivorous AGT-1500 will run happily on anything liquid and flammable.  Which has better strategic mobility?  Soviet rail gauge was slightly wider than Western European standard; 3.32 vs 3.15 meters.  But Soviet tanks in the Cold War were generally kept lighter and smaller, and had to be in order to be moved in large numbers on a rail and road network that was not as robust as that further west.  So if NATO and the Warsaw Pact had switched tanks in the late 1950s, they would both have downgraded the strategic mobility of their forces, as the Soviet tanks would be slightly too wide for unrestricted movement on rails in the free world, and the NATO tanks would have demanded more logistical support per tank than evil atheist commie formations were designed to provide.
       

       
      So instead of wading into a deep and subtle subject, I am going to write about something that is extremely simple and easy to describe in mathematical terms; the top speed of a tank moving in a straight line.  Because it is so simple and straightforward to understand, it is also nearly meaningless in terms of the combat performance of a tank.
       
      In short, the top speed of a tank is limited by three things; the gear ratio limit, the power limit and the suspension limit.  The tank's maximum speed will be whichever of these limits is the lowest on a given terrain.  The top speed of a tank is of limited significance, even from a tactical perspective, because the tank's ability to exploit its top speed is constrained by other factors.  A high top speed, however, looks great on sales brochures, and there are examples of tanks that were designed with pointlessly high top speeds in order to overawe people who needed impressing.
       

      When this baby hits 88 miles per hour, you're going to see some serious shit.
       
      The Gear Ratio Limit
       
      Every engine has a maximum speed at which it can turn.  Often, the engine is artificially governed to a maximum speed slightly less than what it is mechanically capable of in order to reduce wear.  Additionally, most piston engines develop their maximum power at slightly less than their maximum speed due to valve timing issues:
       

      A typical power/speed relationship for an Otto Cycle engine.  Otto Cycle engines are primitive devices that are only used when the Brayton Cycle Master Race is unavailable.
       
      Most tanks have predominantly or purely mechanical drivetrains, which exchange rotational speed for torque by easily measurable ratios.  The maximum rotational speed of the engine, multiplied by the gear ratio of the highest gear in the transmission multiplied by the gear ratio of the final drives multiplied by the circumference of the drive sprocket will equal the gear ratio limit of the tank.  The tank is unable to achieve higher speeds than the gear ratio limit because it physically cannot spin its tracks around any faster.
       
      Most spec sheets don't actually give out the transmission ratios in different gears, but such excessively detailed specification sheets are provided in Germany's Tiger Tanks by Hilary Doyle and Thomas Jentz.  The gear ratios, final drive ratios, and maximum engine RPM of the Tiger II are all provided, along with a handy table of the vehicle's maximum speed in each gear.  In eighth gear, the top speed is given as 41.5 KPH, but that is at an engine speed of 3000 RPM, and in reality the German tank engines were governed to less than that in order to conserve their service life.  At a more realistic 2500 RPM, the mighty Tiger II would have managed 34.6 KPH.
       
      In principle there are analogous limits for electrical and hydraulic drive components based on free speeds and stall torques, but they are a little more complicated to actually calculate.
       

      Part of the transmission from an M4 Sherman, picture from Jeeps_Guns_Tanks' great Sherman website
       
      The Power Limit
       
      So a Tiger II could totally go 34.6 KPH in combat, right?  Well, perhaps.  And by "perhaps," I mean "lolololololol, fuck no."  I defy you to find me a test report where anybody manages to get a Tiger II over 33 KPH.  While the meticulous engineers of Henschel did accurately transcribe the gear ratios of the transmission and final drive accurately, and did manage to use their tape measures correctly when measuring the drive sprockets, their rosy projections of the top speed did not account for the power limit.
       
      As a tank moves, power from the engine is wasted in various ways and so is unavailable to accelerate the tank.  As the tank goes faster and faster, the magnitude of these power-wasting phenomena grows, until there is no surplus power to accelerate the tank any more.  The system reaches equilibrium, and the tank maxes out at some top speed where it hits its power limit (unless, of course, the tank hits its gear ratio limit first).
       
      The actual power available to a tank is not the same as the gross power of the motor.  Some of the gross horsepower of the motor has to be directed to fans to cool the engine (except, of course, in the case of the Brayton Cycle Master Race, whose engines are almost completely self-cooling).  The transmission and final drives are not perfectly efficient either, and waste a significant amount of the power flowing through them as heat.  As a result of this, the actual power available at the sprocket is typically between 61% and 74% of the engine's quoted gross power.
       
      Once the power does hit the drive sprocket, it is wasted in overcoming the friction of the tank's tracks, in churning up the ground the tank is on, and in aerodynamic drag.  I have helpfully listed these in the order of decreasing importance.
       
      The drag coefficient of a cube (which is a sufficiently accurate physical representation of a Tiger II) is .8. This, multiplied by half the fluid density of air (1.2 kg/m^3) times the velocity (9.4 m/s) squared times a rough frontal area of 3.8 by 3 meters gives a force of 483 newtons of drag.  This multiplied by the velocity of the tiger II gives 4.5 kilowatts, or about six horsepower lost to drag.  With the governor installed, the HL 230 could put out about 580 horsepower, which would be four hundred something horses at the sprocket, so the aerodynamic drag would be 1.5% of the total available power.  Negligible.  Tanks are just too slow to lose much power to aerodynamic effects.
       
      Losses to the soil can be important, depending on the surface the tank is operating on.  On a nice, hard surface like a paved road there will be minimal losses between the tank's tracks and the surface.  Off-road, however, the tank's tracks will start to sink into soil or mud, and more power will be wasted in churning up the soil.  If the soil is loose or boggy enough, the tank will simply sink in and be immobilized.  Tanks that spread their weight out over a larger area will lose less power, and be able to traverse soft soils at higher speed.  This paper from the UK shows the relationship between mean maximum pressure (MMP), and the increase in rolling resistance on various soils and sands in excruciating detail.  In general, tanks with more track area, with more and bigger road wheels, and with longer track pitch will have lower MMP, and will sink into soft soils less and therefore lose less top speed.
       
      The largest loss of power usually comes from friction within the tracks themselves.  This is sometimes called rolling resistance, but this term is also used to mean other, subtly different things, so it pays to be precise.  Compared to wheeled vehicles, tracked vehicles have extremely high rolling resistance, and lose a lot of power just keeping the tracks turning.  Rolling resistance is generally expressed as a dimensionless coefficient, CR, which multiplied against vehicle weight gives the force of friction.  This chart from R.M. Ogorkiewicz' Technology of Tanks shows experimentally determined rolling resistance coefficients for various tracked vehicles:
       

       
      The rolling resistance coefficients given here show that a tracked vehicle going on ideal testing ground conditions is about as efficient as a car driving over loose gravel.  It also shows that the rolling resistance increases with vehicle speed.  A rough approximation of this increase in CR is given by the equation CR=A+BV, where A and B are constants and V is vehicle speed.  Ogorkiewicz explains:
       
       
      It should be noted that the lubricated needle bearing track joints of which he speaks were only ever used by the Germans in WWII because they were insanely complicated.  Band tracks have lower rolling resistance than metal link tracks, but they really aren't practical for vehicles much above thirty tonnes.  Other ways of reducing rolling resistance include using larger road wheels, omitting return rollers, and reducing track tension.  Obviously, there are practical limits to these approaches.
       
      To calculate power losses due to rolling resistance, multiply vehicle weight by CR by vehicle velocity to get power lost.  The velocity at which the power lost to rolling resistance equals the power available at the sprocket is the power limit on the speed of the tank.
       
      The Suspension Limit
       
      The suspension limit on speed is starting to get dangerously far away from the world of spherical, frictionless horses where everything is easy to calculate using simple algebra, so I will be brief.  In addition to the continents of the world not being completely comprised of paved surfaces that minimize rolling resistance, the continents of the world are also not perfectly flat.  This means that in order to travel at high speed off road, tanks require some sort of suspension or else they would shake their crews into jelly.  If the crew is being shaken too much to operate effectively, then it doesn't really matter if a tank has a high enough gear ratio limit or power limit to go faster.  This is also particularly obnoxious because suspension performance is difficult to quantify, as it involves resonance frequencies, damping coefficients, and a bunch of other complicated shit.
       
      Suffice it to say, then, that a very rough estimate of the ride-smoothing qualities of a tank's suspension can be made from the total travel of its road wheels:
       

       
      This chart from Technology of Tanks is helpful.  A more detailed discussion of the subject of tank suspension can be found here.
       
      The Real World Rudely Intrudes
       
      So, how useful is high top speed in a tank in messy, hard-to-mathematically-express reality?  The answer might surprise you!
       

      A Wehrmacht M.A.N. combustotron Ausf G
       
      We'll take some whacks at everyone's favorite whipping boy; the Panther.
       
      A US report on a captured Panther Ausf G gives its top speed on roads as an absolutely blistering 60 KPH on roads.  The Soviets could only get their captured Ausf D to do 50 KPH, but compared to a Sherman, which is generally only credited with 40 KPH on roads, that's alarmingly fast.
       
      So, would this mean that the Panther enjoyed a mobility advantage over the Sherman?  Would this mean that it was better able to make quick advances and daring flanking maneuvers during a battle?
       
      No.
       
      In field tests the British found the panther to have lower off-road speed than a Churchill VII (the panther had a slightly busted transmission though).  In the same American report that credits the Panther Ausf G with a 60 KPH top speed on roads, it was found that off road the panther was almost exactly as fast as an M4A376W, with individual Shermans slightly outpacing the big cat or lagging behind it slightly.  Another US report from January 1945 states that over courses with many turns and curves, the Sherman would pull out ahead because the Sherman lost less speed negotiating corners.  Clearly, the Panther's advantage in straight line speed did not translate into better mobility in any combat scenario that did not involve drag racing.
       
      So what was going on with the Panther?  How could it leave everything but light tanks in the dust on a straight highway, but be outpaced by the ponderous Churchill heavy tank in actual field tests?
       

      Panther Ausf A tanks captured by the Soviets
       
      A British report from 1946 on the Panther's transmission explains what's going on.  The Panther's transmission had seven forward gears, but off-road it really couldn't make it out of fifth.  In other words, the Panther had an extremely high gear ratio limit that allowed it exceptional speed on roads.  However, the Panther's mediocre power to weight ratio (nominally 13 hp/ton for the RPM limited HL 230) meant that once the tank was off road and fighting mud, it only had a mediocre power limit.  Indeed, it is a testament to the efficiency of the Panther's running gear that it could keep up with Shermans at all, since the Panther's power to weight ratio was about 20% lower than that particular variant of Sherman.
       
      There were other factors limiting the Panther's speed in practical circumstances.  The geared steering system used in the Panther had different steering radii based on what gear the Panther was in.  The higher the gear, the wider the turn.  In theory this was excellent, but in practice the designers chose too wide a turn radius for each gear, which meant that for any but the gentlest turns the Panther's drive would need to slow down and downshift in order to complete the turn, thus sacrificing any speed advantage his tank enjoyed.
       
      So why would a tank be designed in such a strange fashion?  The British thought that the Panther was originally designed to be much lighter, and that the transmission had never been re-designed in order to compensate.  Given the weight gain that the Panther experienced early in development, this explanation seems like it may be partially true.  However, when interrogated, Ernst Kniepkamp, a senior engineer in Germany's wartime tank development bureaucracy, stated that the additional gears were there simply to give the Panther a high speed on roads, because it looked good to senior generals.
       
      So, this is the danger in evaluating tanks based on extremely simplistic performance metrics that look good on paper.  They may be simple to digest and simple to calculate, but in the messy real world, they may mean simply nothing.
    • By Walter_Sobchak
      I realized that we have a thread for transmissions and final drives, but not for engines.
      I'll start with this post about the Japanese 10 ZF engine from the Type 74 tank.  As far as I know, not much has been published in English about this engine.  It's a rather interesting one in that it's an air-cooled 2 stroke diesel.  


    • By Scolopax
      First official render of Northrop Grumman's LRSB is out.  We have a designation, but the Air Force is still looking for a name.
       

       
      Still not much other info out yet.
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