Were the Rolls-Royce Vulture & Packard X-2775 Horrible Failures? — Transcript

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1. 0:00The interwar years delivered arguably the  most interesting aircraft and piston engine
2. 0:05development in history it is often referred to as  the Golden Age of Flight. While piston engines for
3. 0:11aircraft peaked during World War II most of that  is a result of the wild engine development that
4. 0:17happened during the interwar years. While there  are various ways to increase a piston engine's
5. 0:22horsepower to drastically increased horsepower at  the time, more cylinders were needed this led to a
6. 0:29lot of interesting engine layouts with 18 or  more cylinders one of which was the X engine
7. 0:36only about a handful of different X layout  aero engine designs ever got built most of
8. 0:42which never got past the prototype stage and  none are generally considered to have been  successful
9. 0:47that is arguable so let's look at  two X engines with different levels of promise
10. 0:53and success the Packard X-2775 and the Rolls-Royce  Vulture and you can judge its success for yourself
11. 1:09During the 1920's air races were  the proving grounds for military fighter
12. 1:13aircraft concepts the most popular being the  Schneider Trophy air race often erroneously
13. 1:19called the Schneider Cup Mario de Bernardi  had just won the 1926 trophy in a Macchi M.39
14. 1:26powered by a Fiat AS.2 V-12 engine producing  801 horsepower setting an average speed of 246.49 mph
15. 1:36when a group of enthusiasts announced they will build a plane and participate in the next race in 1927
16. 1:43with US Navy pilot Al Williams to pilot it this was  a private venture since the US government
17. 1:49declared it wouldn't officially send a team to  compete but indirect support from the US Navy
18. 1:55would be offered which was to cover the cost  of engine development American engine company
19. 2:00Packard was asked to design and build an engine  and the airplane would be built by Kirkham Products
20. 2:06Corporation and was to be called the Kirkham- Williams Racer since there was limited time
21. 2:11to develop the new engine for the 1927 race  Packard looked at what engines they already
22. 2:17had and homed in on their 1A-1500 500 horsepower  V-12 that they designed in 1924 even though it
23. 2:26had a reputation for being unreliable Packard  decided to use as many components from their
24. 2:31V-12 as possible to create the new design called  the 1A-2775 with military designation being X-2775
25. 2:41Since a quick way of massively increasing  engine horsepower was to double the amount
26. 2:45of cylinders they did just that by virtually  stacking an upright 1A-1500 V-12 a top an inverted
27. 2:53one connected to a common crankshaft to  create an X configuration engine
28. 3:03The angle between the top two cylinder banks and  the bottom two banks of inline sixes remained
29. 3:0860° as it was in the 1A-1500 V-12 this meant the  bank angle between the top and bottom banks on
30. 3:16the sides of the X engine was 120° 24 individual  steel cylinders were mounted to a single piece
31. 3:23cast aluminium crank case to keep weight as low as  possible while giving maximum strength the engine
32. 3:29was liquid cooled and cylinders each had four  valves two inlet and two exhaust and were operated
33. 3:36by a single overhead camshaft per cylinder bank  in an attempt to improve exhaust valve cooling
34. 3:41the valves had hollow stems to allow cooling  by oil the valve covers of the bottom cylinders
35. 3:47also acted as a sump for oil collection the  ignition system was battery powered and had
36. 3:52four distributors at the rear of the engine  the crankshaft had six crankpins phased 120° apart
37. 4:00like found in an inline 6 as well as a V-12  assuming the build adhered to the design drawings
38. 4:06the crankpins didn't have the standard inline  six crank throws with the usual mirroring of two
39. 4:11inline threes where the center two crank pins were  at the same position same as the middle and outer crankpins
40. 4:18In my opinion this would be a strange design decision which I don't quite understand as
41. 4:23it discards the perfect balance of the inline  six this engine consisting of four of those
42. 4:30this would likely have resulted in a slight  imbalance in the form of a rocking couple the
43. 4:35whole point of using six inline cylinders for  each bank instead of seven or five is because
44. 4:40of the inherent perfect balance of the inline  six but when changing the crank throws that
45. 4:45perfect balance goes out the window each of the  six crankpins moved four pistons which were all
46. 4:51aligned and conrod moving through the same plane  of rotation like on a radial engine meaning like
47. 4:58a radial engine it necessitated the use of a  connecting rod assembly made up of a master
48. 5:04rod and articulated rods all conrods couldn't  be articulated since this would allow the rod
49. 5:10assembly a certain degree of freedom to rotate  around the crankpin bearing which then affects
50. 5:16the position of the pistons in the cylinders  this would be problematic and would quickly
51. 5:21lead to catastrophic failure to prevent this  one of the conrods needed to be fixed to the
52. 5:26rod assembly to prevent rotation around the crankpin  the other conrods were articulated the articulated
53. 5:33conrods were shorter in length than the master  conrod and the reason for this is the position
54. 5:38of the big end of the articulated rods unlike the  master conrod which rotates around the center of
55. 5:44the crankshaft the articulated rods each rotate  around a point slightly offset of the center of
56. 5:50the crankshaft which was positioned towards its  cylinder this not only resulted in an elliptical
57. 5:56rotation rather than a perfectly circular rotation  like the master rod but it would also result
58. 6:02in the piston moving higher up in the cylinder  towards top dead center and thus the articulated
59. 6:07roads need to be shorter but we have not yet  gotten to the weirdest part of this engine
60. 6:13The engine's crankshaft was not placed in the center  of the crank case but around 38 mm above center
61. 6:21To accommodate this the two lower articulated rods  had to be 38 mm longer than the top articulated
62. 6:28rod meaning of the four conrods of each row  of cylinders only two were identical this also
63. 6:35meant that for each row the four cylinders did  not have the same displacement the cylinder
64. 6:40with the master conrod had a stroke of 127 mm  and the cylinders with articulated conrods had
65. 6:47a longer stroke of 130 mm which was due to the  elliptical motion of the big end and the shorter
66. 6:54length of the articulated rods cylinder bore was  obviously identical at 136.5 mm the cylinders
67. 7:02utilizing a master corod had a displacement of  1.86 L and the cylinders with articulated rods
68. 7:09had a displacement of 1.91 L and so the  total displacement of the engine was 45.5L
69. 7:23Despite the seemingly crazy engine  design the engine worked and even passed
70. 7:28acceptance testing at 2,700 RPM the direct drive  engine produced 1,250 horsepower at a weight of
71. 7:37686 kg and gave the Kirkham-Williams racer a good  max speed of around 270 mph however early
72. 7:47indications were that the competitors in the 1927  Schneider Trophy race would be faster than that
73. 7:53In response to that information an attempt was made  to make the Kirkham-Williams racer faster before
74. 7:59the race so a second X-2775 engine was built this  time with a Roots type supercharger however due to
75. 8:07time constraints it was hastily assembled and the  supercharger created less than four PSI of boost
76. 8:14and increased engine power output to only 1,300  horsepower at a penalty of making the engine about
77. 8:21100 kg heavier this was disappointing and instead  the designers thought that the additional weight
78. 8:28of the supercharger could would be better spent  being replaced by a propeller speed reduction
79. 8:32unit geared to a 0.677 to1 ratio by slowing down  propeller speed propeller blade efficiency could
80. 8:42be increased however with the engine and overall  plane development still ongoing by the time of
81. 8:47the air race the Kirkham-Williams racer did not  compete in the 1927 Schneider Trophy race
82. 8:54The race was won by the Supermarine S.5 at an average  speed of 281.66 mph more than 10 mph faster than
83. 9:03the Kirkham-Williams racer could do the X-2775 was  further improved by increasing compression ratio
84. 9:10by replacing the battery ignition system with  magnetos and by installing a ram-air induction system
85. 9:17This upgraded engine was installed in a  new racer called the Williams Mercury racer with
86. 9:22Al planning to use it to compete in the 1929 race  although looking like a monoplane version of the
87. 9:29Kirkham-Williams racer the Williams Mercury racer was  a completely new design and right from the
88. 9:35start had issues with being overweight mostly unrelated to the engine and the seaplane was unable to takeoff
89. 9:43Some work was done to the  aircraft and seemingly to the engine as well
90. 9:46but the weight issues couldn't be resolved to  a satisfactory degree and the plane could not
91. 9:52compete in the 1929 race further attempts  were made to improve the plane but problems
92. 9:58persisted and with support from the US Navy  faltering it never got close to competing in
93. 10:03a race before the Schneider Trophy races ended  in 1931 the engine was further developed in
94. 10:10the mid-30s into the 2A-2775 and some sources  claim the engine produced an impressive 1,900
95. 10:18horsepower at 2,800 RPM despite the problems with  the Williams Mercury racer the X-2775 engine itself
96. 10:27didn't have any major problems and and was quite  reliable however with the US especially the Navy
97. 10:34investing heavily into radial engines around  this time the Packard X-2775 engine faded into history
98. 10:48Surprisingly the X-2775 wasn't to be the  last of the X configuration aero engines
99. 10:54Around the mid-30s the British Air Ministry anticipated  that a 2,000 plus horsepower engine would be
100. 11:01required by the early' 40s Rolls-Royce who was  quite specialist with V-12 engine design by this
101. 11:08time decided to try their hand at the X-24 engine  to meet this 2,000 horsepower requirement the
102. 11:16X-24 in theory should have been able to roughly  double the power of their best V-12 at the time
103. 11:23which was the Peregrine the ultimate version  of the Kestrel. Fast forward a few years the
104. 11:29Rolls-Royce Vulture ended up as the only X-24 aero  engine to have entered large scale production in history
105. 11:44Like the X-2775 before it the Vulture  design started out as two V-12s sharing a
106. 11:50common crankshaft Rolls-Royce initially used  the inline cylinder banks of the Peregrine but
107. 11:56as the engine developed fewer Peregrine parts  used and eventually it shared no parts with
108. 12:02their V-12 unlike the X-2775 from Packard the 60° V  bank angle was not retained and the angle between
109. 12:11all four cylinder banks was 90° a six throw  crankshaft was installed in the center of a
110. 12:18two-piece crank case and was supported by seven  main bearings each cylinder had four valves two
111. 12:25intake and two exhaust with the exhaust valves  being sodium filled to improve cooling
112. 12:31The valves were driven by a single overhead camshaft on  each six-cylinder bank the 127 mm bore and 140 mm
113. 12:40stroke gave the Vulture a displacement of 42 L  and the liquid cooled engine's drive weight was
114. 12:461,111 kg propeller speed was reduced by a 0.35:1  reduction ratio compound gear reduction unit
115. 12:56With its two-speed single stage supercharger early in  indication showed that the engine should produce
116. 13:01around 1,750 horsepower at 3,200 RPM like Packard's X-24 before it the Vulture used a master and
117. 13:11articulated conrod setup and here is where much of  the Vulture's trouble manifested the engine first
118. 13:18ran in 1937 but had problems with main bearings  due to cooling problems lubrication problems or both
119. 13:26Even so many hundreds of hours of testing  had been done on the engines and Rolls-Royce
120. 13:31was confident the problems could be resolved I  couldn't find any official record of the Vulture's
121. 13:36firing interval it seems to be a slightly debated  topic on forums with some saying a cylinder was
122. 13:43fired every 30° of crankshaft rotation others are  saying no two cylinders were fired at the same
123. 13:49time meaning it was fired in intervals of 60° of  crankshaft rotation others saying it was 90, 30, 90, 30
124. 13:58and so on the only official reference I could  find was in regards to firing order cylinders
125. 14:04were numbered by a row starting with number one  on the propeller end to six towards the rear and
126. 14:10the banks were numbered A to D starting top left  going clockwise assuming this sequence is correct
127. 14:16firing interval must have been in 30° intervals  and eliminates any other possibility
128. 14:22If it was fired in 60° intervals or 90, 30, 90, 30 then it would  need to fire two cylinders at the same time since
129. 14:3260 times 24 - the amount of cylinders - is 1,440 which  is two four stroke revolutions same for 90, 30, 90, 30
130. 14:43and if two cylinders were fired at the same time  then the way the firing order is written makes no sense
131. 14:49To test this I created a 2D simulation  to see if the firing orders work out with 30° intervals
132. 14:56And it does! That meant the Vulture  had an even firing interval after all I also
133. 15:02checked to see if it could fire two cylinders  at the same time with this firing order and it
134. 15:08can not as every second piston is not in the  correct position to be fired when the first one
135. 15:14is the simulation does not allow two cylinders  to be fired at the same time with the stated
136. 15:20firing order this assumes my cylinder numbering  is correct anyway I spent a few hours trying to
137. 15:26figure this out and it will take me about 10  minutes just to explain what I did here and
138. 15:32I'm not going to do that feel free to replay my  simulation and work it out if it's important to you
139. 15:38If you do find a different result than I did  leave a comment below for the rest let's carry on
140. 15:49By 1938 the Vulture successfully produced  the targeted 1,750 horsepower and in 1939 engine
141. 15:58production was given the green light but the  aforementioned reliability problems meant the
142. 16:03engine had to be de-rated by limiting max RPM to  3,000 to avoid power loss at the lowered max RPM
143. 16:11supercharger boost was increased from 6 PSI to 9  PSI the Vulture was set to power the twin engine a
144. 16:19Manchester bomber which first took flight powered  by two Vultures in 1939 several hundred vultures
145. 16:26were then ordered for Manchester production  the the Vulture was also set to power a new
146. 16:31fighter aircraft the Hawker Tornado which too  first flew in 1939 testing went quite well and
147. 16:38again several hundred Vultures were ordered  for Tornado production an updated prototype
148. 16:43powered by the Vulture V achieved an impressive  398 mph at 23,000 ft Tornado production was
149. 16:52delayed during the Battle of Britain with Hawker  understandably prioritizing Hurricane production
150. 16:58which was crucial for the defense of the nation  to make matters worse vulture development also
151. 17:04had to be halted to allow Rolls-Royce to focus  on the Merlin engine which of course powered the
152. 17:09pivotal Hurricanes and Spitfires this halt in  development meant that the Vulture later went
153. 17:15into production with many of the reliability  issues still present this contributed greatly
154. 17:20to the problems on the Avro Manchester bomber with  a very high engine failure rate and the bomber
155. 17:26which in most circumstances were unable to maintain  altitude on one engine after the other failed
156. 17:33led to the demise of a high number of Manchester  crews because of this the bomber was grounded
157. 17:38several times engine failures were attributed  to cooling issues and main bearing failure also
158. 17:45caused by cooling and lubrication issues among  a few other problems max engine RPM was again
159. 17:51lowered this time to 2,850 RPM in an attempt  to lower engine failure rate after many more
160. 17:58modifications eventually engine reliability  improved drastically however it seemed to be
161. 18:05too little too late by this time the Merlin was  approaching horsepower numbers not far off the
162. 18:10Vulture and Rolls-Royce decided to focus on Merlin  and Griffon development and production and cancel
163. 18:17Vulture production the Vulture powered Tornado  fighter which surprisingly didn't experience
164. 18:23engine issues to the same degree as the Manchester  bomber was cancelled shortly after Rolls-Royce
165. 18:29stopped Vulture production and Hawker instead  focused on the Napier Sabre powered derivative
166. 18:35called the Typhoon the Manchester bomber was  subsequently redesigned by replacing the two
167. 18:40Vultures with four trusty Merlins and became the  Lancaster a very successful bomber in World War II
168. 18:48Was the Rolls-Royce Vulture a failure then? In my  opinion yes but I think it would likely have been
169. 18:55successful if development continued there also  doesn't seem to be any inherent problems with
170. 19:00the X layout but ill-timed events that caused  development disruptions as well as other 2,000
171. 19:07plus horsepower engine layouts that were more  advanced at this stage like the Napier Sabre the
172. 19:13Rolls-Royce Griffon and Bristol Centaurus pretty  much made the Vulture redundant and of course with
173. 19:20the advent of the turbo jet engine which made  all high power piston aero engines redundant
174. 19:25there was no reason to later find out if the  X layout could have been successful or perhaps
175. 19:31even superior to other layouts I hope that was  informative and perhaps even enjoyable if it was
176. 19:38then you will probably like these two videos as  well thanks for watching see you in the next one