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On 11/14/2017 at 12:09 PM, Collimatrix said:

 

I haven't found the capacity of that rear tank, but yes, by all accounts the pony was... squirrely until it was empty.  Late model FW-190s had a similar fuel tank behind the pilot, and I would bet they emptied that one first too.

 

On 11/14/2017 at 11:07 PM, Jeeps_Guns_Tanks said:

85 gallons. 

 

P-51D-fuel-tanks.png

 

On 11/14/2017 at 11:26 PM, Collimatrix said:

So that's about 500 pounds placed about four feet behind the CG.  Yep, that could cause some issues.

 

 

Not as bad as you'd think, the CG on the '51 was fairly flexible and trimmable. In addition to that 85 gallon tank, the battery of radios would sit above it, and they were not small either.  Then there was the Radiator...

 

Later, folks would remove the tank and radios and fit a second seat there, with little change in performance. 

 

The Collings foundation has a twin seat P-51 B/C.

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8 hours ago, Collimatrix said:

I think even with a seat and oxygen equipment, a passenger would weigh less than 85 gallons of fuel.

Depending on the conversion (and passenger) it often weighs more.  The one owned by the Collings foundation for example, has full dual controls and instrumentation.

Profile-

cockpit-

 

10 minutes ago, Jeeps_Guns_Tanks said:

Do civy planes warbirds have to have working oxygen systems if they can get that high?

Yes, but modern O2 systems are much lighter than the old LP systems used in WW2 aircraft. 

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3 minutes ago, Meplat said:

Depending on the conversion (and passenger) it often weighs more.  The one owned by the Collings foundation for example, has full dual controls and instrumentation.

Profile-

cockpit-

 

 

 

Interesting.  Do they have to put any ballast in the front of the aircraft to offset that?

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4 hours ago, Collimatrix said:

 

Interesting.  Do they have to put any ballast in the front of the aircraft to offset that?

Never got a straight answer. 

I also assume there was a bit of alteration to the horizontal stab to account for the change in arm, since the bird is also slightly longer than stock in that config. 

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On 12/1/2017 at 6:12 PM, Collimatrix said:

 

I figured you probably weren't a stranger to 'em.  How do they compare to modern setups for cars and the like?

Oh, completely different. Turbines were HUGE. Like 8~12" across, so spool up was slow. For a plane mill, not a huge deal,

since you were turning a huge prop, not a  30 odd inch wheel/tire.

 

Also, the biggest difference is the vast majority of WW2 era turbosuperchargers were intended to suppliment an already 

existing supercharger. As in "provide sea level atmosphere at 30K feet" and from there the existing blower would do the rest. 

Some, like the GE's on the P-38 could do far more, raising upper deck pressures to dangerous levels at sea level, much to the detriment of the 1710,

the maintenance crew, and the amusement of the pilot (My grandad told me about pilots doing this, running absurd levels of boost at TO to get to altitude fast).

 

Lastly is the size of the install. To start, you're not feeding 1500+ cubic inches in a car. So the plumbing, intercooler, turbo, wastegate, etc can be a lot smaller. 

 

Case in point, note how much space this install takes up. 

Jug Huff

 

iEZpLMy.jpg

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Big-Chief-CrowMod-Turbo-Install-Lutz-Rac

Here's a pic of a Turbo setup, on a iron block Pontiac Mill that makes more than 2500 HP from 468 cubic inches of Pontiac motor goodness. 

 

(Street Outlaws being my favorite show is my dirty little secret.)

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Modern cars have all sorts of ways of sidestepping turbo lag.  There are twin turbo setups, comprex superchargers, variable geometry, etc.  I suspect, but don't know for sure, that modern consumer car turbo metallurgy is beyond the wildest dreams of WWII turbo designers, since it's probably piggybacking on several decades of jet engine turbine development.

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I've noticed that on a lot of Western Allied radial engines, most all being of Wright and Pratt & Whitney making, there is a lack of a large nose cone or cover on the end of the propeller shaft. 

 

id_fighters_p47_06_700.jpg 

 

 

 

Meanwhile, everyone else has one

 

ww2kanin1k1j-0.jpg        

 

 

Is there a reason for this design choice?  Is it something to do with the propeller shaft?

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On 12/3/2017 at 7:40 PM, Scolopax said:

I've noticed that on a lot of Western Allied radial engines, most all being of Wright and Pratt & Whitney making, there is a lack of a large nose cone or cover on the end of the propeller shaft. 

 

id_fighters_p47_06_700.jpg 

 

 

 

Meanwhile, everyone else has one

 

ww2kanin1k1j-0.jpg        

 

 

Is there a reason for this design choice?  Is it something to do with the propeller shaft?

 

 

The piece you're looking at is called the "spinner," and yes, it is aerodynamically important.

 

There were various attempts to improve the streamlining of the spinner on radial engines.  The most radical approach was the ducted spinner used on the FW-190 prototype:

440px-Fw190V1.jpg

 

Something similar was tried on some experimental Tempests, although those had in-line engines:

EkCteWR.png

I don't know specifically why the spinner was so small on most R-2800s, but I suspect that it had to do with cooling.  The R-2800 had some pretty formidable cooling requirements.  When it was first developed it had one of the highest horsepower to cylinder count ratios of any engine in the world.  It was also the first engine from P&W with machined cooling fins.  Previously, it had sufficed to forge or cast the cooling fins surrounding the cylinders.  On the R2800, Pratt and Whitney had to finely machine each fin so they could make them as thin and densely packed as possible, for maximum cooling surface area.  Obviously, this is expensive and an enormous pain in the ass, so it gives you an idea of how hard it was to cool the monster.

 

I think ducted spinners, like V-tails did reduce drag by a measureable amount, but introduced so many other problems (the FW-190 prototype had engine cooling issues) that the juice was not worth the squeeze.

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On 12/3/2017 at 8:40 PM, Scolopax said:

I've noticed that on a lot of Western Allied radial engines, most all being of Wright and Pratt & Whitney making, there is a lack of a large nose cone or cover on the end of the propeller shaft. 

 

id_fighters_p47_06_700.jpg 

 

 

 

Meanwhile, everyone else has one

 

ww2kanin1k1j-0.jpg        

 

 

Is there a reason for this design choice?  Is it something to do with the propeller shaft?

No spinner makes for easy prop swaps, that's for sure.

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On the topic brought up previously about push-pull configurations, but sadly off topic for the thread, why didn't four engined bombers use push-pull configurations to reduce drag? They wouldn't have the bailing out, take-off, center of gravity, navigation, and vibration problems that fighters had, and the 4 engine nacelles on a bomber look like they would cause a lot of drag that could have been reduced with just two push-pull nacelles. Just not worth it on a heavy bomber compared to a fighter?

 

There seem to have been quite a few 4-engined push-pull aircraft in the Interwar but their designs cease almost entirely by 1935 after having trailed off after 1930.

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There's not a whole lot of surviving documentation on WWI aircraft, but supposing the Fokker Dr.1 represents engine horsepower (at 110HP as one source cites) of WWI aviation engines in general, I'd guess the biggest issue would be cooling. Advances in engine design, engineering processes, and material technology allowed rated power on engines to soar by the time we reached WWII. While it's possible to dump more fuel and air at once into larger and more numerous cylinders, thermodynamics aren't on vacation and you need to dump the waste heat overboard if you don't want your pistons to take a forever break. The Wright 1820 which saw use on B17s developed something like 700 rated HP depending on your model. I'm not sure waste heat scales linearly to HP but it seems intuitive to say it should, and at any rate that's a lot more waste heat than you saw in WWI planes in which could probably get by on a single cooling intake for both engines without a huge increase in front profile. So the issue for me seems to be that you just need more space in your frontal profile for cooling, which is made easy by having a full pod for each engine. There are some ways to mitigate cylinder heat, like running rich of peak and having oil coolers, but you can only mess with your F/A ratio so much before your engine can't burn fuel anymore, and oil coolers still take up some of your front profile so you're still canceling out some of your lift to cool the oil.

 

Some other things could have had an impact as well; assuming your design doesn't have the crank running through the rear of the engine so that both propellers are powered by the same engine (which means you've lost the HP of an extra engine), you need more engines, and more cylinders means the engines need more cooling air. You could run ducting for ram air into the nacelle , but that means a bigger nacelle, which probably already got bigger when you stuffed the second engine into it. Push engines in push pull configurations already lose some efficiency from operating in the disturbed airstream from the puller props, and the efficiency you gained by losing an engine pod is rapidly being reclaimed by the inescapable tendency of this world to hate fun. I'm not sure where the lines cross and whether you've gained or lost efficiency, but I'd guess the complexity you add to the system makes it easier, if not more efficient to just make the thing with four nacelles after the previous downsides have already been added up.

 

A few other possibilities; a lot of WWII bombers were conventional geared and their props already came fairly close to the ground; with the pusher props located behind the pullers, there could have been some risk for prop strikes, which would probably be the easiest engineering hurdle to fix. The mounting points would have had to have been reinforced to probably slightly less than twice their original strength to hold the new engine and all of its accessories, which may have been too much put at one location on a spar with WWII engineering (decent chance that this is bullshit!). 

 

Of course the easiest answer is that push pulls were unconventional and they may not have wanted to push something untested into production when the convention was already well tested.

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For efficient propulsion you want to throw lots of mass of air backwards at lowish speed1 ([mass per second * speed it's pushed out the propeller] gives the thrust, whereas [mass per second * speed it's pushed out the propeller ^2] gives the energy used which should correlate to the fuel used). The rearward prop is pushing on air that's already moving backwards, so needs more power to get the same thrust as the front prop. Same reason high bypass turbofans are more efficient than turbojets.

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On 12/12/2017 at 8:53 PM, AdmiralTheisman said:

On the topic brought up previously about push-pull configurations, but sadly off topic for the thread, why didn't four engined bombers use push-pull configurations to reduce drag? They wouldn't have the bailing out, take-off, center of gravity, navigation, and vibration problems that fighters had, and the 4 engine nacelles on a bomber look like they would cause a lot of drag that could have been reduced with just two push-pull nacelles. Just not worth it on a heavy bomber compared to a fighter?

 

There seem to have been quite a few 4-engined push-pull aircraft in the Interwar but their designs cease almost entirely by 1935 after having trailed off after 1930.

 

This is a good question, and I don't know the definitive answer offhand.  If I had to guess though, cooling was the biggest problem.  The HE-177 did not have a push-pull configuration, but it did have four engines with only two engine nacelles.  Each nacelle had two engines in tandem, driving a common driveshaft and propeller.

 

Cooling was evidently a problem, as the HE-177 had, according to Bill Gunston, probably the greatest propensity of any aircraft ever mass produced for catching on fire during level, cruising flight.

 

Another issue is maintenance.  WWII high-output piston engines were very maintenance intensive, and stuffing the engines together in common nacelles would have made service trickier.

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On 12/2/2017 at 9:33 PM, Collimatrix said:

Modern cars have all sorts of ways of sidestepping turbo lag.  There are twin turbo setups, comprex superchargers, variable geometry, etc.  I suspect, but don't know for sure, that modern consumer car turbo metallurgy is beyond the wildest dreams of WWII turbo designers, since it's probably piggybacking on several decades of jet engine turbine development.

 

Late to this, but "turbo lag" is a non-issue in aviation.   Modern aviation turbosuperchargers would likely blow the heads/intake of a modern car. They are simply huge, and prone to overboost ASL.  

The downside is that they are slow to drop boost.  When you design to supply sea level atmosphere at 30K feet, with few rapid throttle changes,  you divorce yourself from what is needed for automotive use. 

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On 12/12/2017 at 9:53 PM, AdmiralTheisman said:

On the topic brought up previously about push-pull configurations, but sadly off topic for the thread, why didn't four engined bombers use push-pull configurations to reduce drag? They wouldn't have the bailing out, take-off, center of gravity, navigation, and vibration problems that fighters had, and the 4 engine nacelles on a bomber look like they would cause a lot of drag that could have been reduced with just two push-pull nacelles. Just not worth it on a heavy bomber compared to a fighter?

 

There seem to have been quite a few 4-engined push-pull aircraft in the Interwar but their designs cease almost entirely by 1935 after having trailed off after 1930.

"Propwash". 

 

Running one big swirly bit in the wake of another big swirly bit yields all kinds of unfun.  This level of unfun increases with the size of the mill, and the size of the prop.

 

The Pfiel/Do335 (for example) was prone to pitch oscillation caused by the two blade-discs interacting.  It bordered on unmanageable. 

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On 12/12/2017 at 11:36 PM, Vanagandr said:

There's not a whole lot of surviving documentation on WWI aircraft, but supposing the Fokker Dr.1 represents engine horsepower (at 110HP as one source cites) of WWI aviation engines in general, I'd guess the biggest issue would be cooling. Advances in engine design, engineering processes, and material technology allowed rated power on engines to soar by the time we reached WWII. While it's possible to dump more fuel and air at once into larger and more numerous cylinders, thermodynamics aren't on vacation and you need to dump the waste heat overboard if you don't want your pistons to take a forever break. The Wright 1820 which saw use on B17s developed something like 700 rated HP depending on your model. I'm not sure waste heat scales linearly to HP but it seems intuitive to say it should, and at any rate that's a lot more waste heat than you saw in WWI planes in which could probably get by on a single cooling intake for both engines without a huge increase in front profile. So the issue for me seems to be that you just need more space in your frontal profile for cooling, which is made easy by having a full pod for each engine. There are some ways to mitigate cylinder heat, like running rich of peak and having oil coolers, but you can only mess with your F/A ratio so much before your engine can't burn fuel anymore, and oil coolers still take up some of your front profile so you're still canceling out some of your lift to cool the oil.

 

Some other things could have had an impact as well; assuming your design doesn't have the crank running through the rear of the engine so that both propellers are powered by the same engine (which means you've lost the HP of an extra engine), you need more engines, and more cylinders means the engines need more cooling air. You could run ducting for ram air into the nacelle , but that means a bigger nacelle, which probably already got bigger when you stuffed the second engine into it. Push engines in push pull configurations already lose some efficiency from operating in the disturbed airstream from the puller props, and the efficiency you gained by losing an engine pod is rapidly being reclaimed by the inescapable tendency of this world to hate fun. I'm not sure where the lines cross and whether you've gained or lost efficiency, but I'd guess the complexity you add to the system makes it easier, if not more efficient to just make the thing with four nacelles after the previous downsides have already been added up.

 

A few other possibilities; a lot of WWII bombers were conventional geared and their props already came fairly close to the ground; with the pusher props located behind the pullers, there could have been some risk for prop strikes, which would probably be the easiest engineering hurdle to fix. The mounting points would have had to have been reinforced to probably slightly less than twice their original strength to hold the new engine and all of its accessories, which may have been too much put at one location on a spar with WWII engineering (decent chance that this is bullshit!). 

 

Of course the easiest answer is that push pulls were unconventional and they may not have wanted to push something untested into production when the convention was already well tested.

Oil cooling works VERY well, in a very small range..

 

The 1820 was very understressed.  They could push/exceed the 1000 HP mark easily when feed decent fuel and cammed/timed properly.

 

Waste heat can be used.  I/E P-51, or NACA cowls. 

 

 

Also, my job sucks.

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Hi y'all.

 

Some interesting views put forth, here in this thread.

Do allow some corrections, though, won't you fellas...

 

1,The rear "Aux" fuselage tank in the P-51 wasn't actually a "drop tank" - it was for transit flying & was used 1st,

rather than in combat.

2, P-38 did ok against the lesser forces of Nippon, but could not technologically* hack the pace in the ETO,

  & was replaced by the P-51.

3, P-47, like the other P&W R-2800 powered fighters  - was a real gas-hog,  even at a slow cruise speed,

& like the P-38, was dumped by the 8th AF, on the advent of the P-51 - arriving in numbers.

4, P-51 did not need the "dive flaps" belatedly attached to both P-38 & P-47 to recover control,

& pull out safely - from 'Mach crit' high speed dives.

5, Victory stats collected by the USAAF in the ETO, confirmed their top choice of the P-51 as air-superiority fighter,

- was the right one**.

 

* P-38 was a real handful of control complexity to simply fly, let alone operate in combat - esp' against the faster diving 109/190, whose pilots could spot the big twin-boom Lockheed from a distance,

& then choose an attack profile - to suit themselves. 

 

**The RAF wanted all the Mustangs they could get, (even the Allison powered ones, which they used 'til war's end),

but didn't want P-38's, & relegated the hundreds of lend-lease P-47's they received - solely to combat against the lesser forces of Nippon, too. 

 

 

 

 

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      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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