Following on from my first post looking at the pioneering engines of the pre war period, this week it is time to turn attentions to those engines that were developed during the war. Much like the aircraft designs of the period engine design developed quickly as well.

A number of designs and manufactures featured in Part 1 played important roles during the conflict.

Anzani: 

Anzani was most famous in the years before the war for his three cylinder design which powered Louis Bleriot on his trip across the channel in 1909.

Anzani’s later “Y” shape engines were often referred to as radials, though they certainly don’t match up to what we would see as radial engines today. This notable difference was addressed in 1910 when the Anzani 6 Cylinder was first run, this engine gives a much more familiar look, with the 6 cylinders forming a circle around which the exhaust is attached.

The engine was built by combining two of the 3 cylinder units onto the same crankshaft.

Early versions of this engine provided 45 horse power, with subsequent models providing 75. The early response to the engine wasn’t great as more faith was placed in rotary designs rather than radials at the time.

Anzani radials did find success shortly before the war began however. By 1912 the design had been developed to a 10 cylinder model. This engine could produce up to 110hp which was over what many of the rotaries of the time were putting out.

This design was a two row engine, with 5 cylinders on each row. Oil was distributed through the engine through the crankshaft into the crankpins. From here the centrifugal force would distribute the oil around the rest of the engine.

As well as production lines in France the 10 cylinder was also built in Britain. It was the British built variants which could output an impressive 125hp. In 1914 one of these engines went through an intensive testing program at Farnborough.

A number of types made use of the 10 cylinder engine, though many were one offs or limited production runs. However the Caudron G3 and G4 were major users of the type and were where it found much success, replacing the earlier La Rhone rotaries and radials which powered the types before.

Around the same time as the 10 Cylinder was being developed Anzani also created the very impressive 20 cylinder radial, which could output 200hp, an extraordinary figure for the time. Unsurprisingly only a select number of these engines were used.

These pre-war radials proved to be Anzanis last designs, though the 6 cylinder model did go on to be used in the years following the war on a section of designs.

Gnome & Oberursel: 

Gnome built on the designs they had been working on before the war, paticularly the Mososoupape, which of course was used on a wide range of aircraft throughout the war.

The basic design of the Gnome rotary changed very little throughout the war, eventually becoming part of the La Rhone compnay in any case.

What is an interesting part of Gnomes history is the partnership they formed with German manufacturer Oberursel.

The German firm had been given permission to produce liscened copies of the design under their own name in the years before the war and as such were in a position to continue using these designs throughout.

The first engine that Oberursel came out with was the U.I, which was essentially a copy of the Gnome Delta. This engine produced 100hp and would go on to power a large number of Germany’s aircraft throughout the war including the Fokker Eindecker, the design behind the Fokker Scourge of 1916.

La Rhône joined forces with Gnome for much of the war, with both companies producing their famous pre war rotary designs.

Beardmore: 

While the rotary designs for much of the war were of French deisgn, though in some cases british built, a large number of inline and V engines were designed in britain.

One such design was the Bearmore 160hp, though even this was a development of foreign design.

Starting off life as the Austro Daimler 6, the basis for this engine design began in 1910. The six-cylinder design was always going to be an aero engine from the start, not always a given in this era of development. The engine proved to be very popular and was copied by many companies across Europe.

The first British adaption of the design came in the form of the 120hp Beardmore, which first appeared in 1914. The engine had cast iron cylinders and tell pistons. This engine was used to power a number of British first world war tyes including the Airco DH.3, Armstrong Whitworth FK.8 and some of the RAF FE2s.

Bearmore’s most succesful design however, came in the form of the 160hp adaption, which was first run in 1916 and remained in production until just after the war came to an end. Though providing more power than its predecessor it was ultimately found to be lacking in the reliability department.

For many years there were no running Beardmore engines and the type remains incredibly rare to this day, however The Vintage Aviator Ltd did manage to find an original engine in good condition in Uruguay and were able to rebuild it to airworthy condition. This original engine powers the collections RAF FE.2b replica, with a second aircraft powered by a new build engine.

Two other examples of the engine can be found on display, both in the UK. One example is installed in the FE.2 at Hendon, while the other can be found in the Airspace hangar at Duxford.

Mercedes

As mentioned above, Beardmore where not the only company to draw inspiration from the Austro Daimler 6, the other side were at is as well.

The key design feature the Austro-Daimler had, that makes the Mercedes origins clear is that both engines were built up from an aluminium crankcase. This was connected to steel cylinders which were bolted on to the crankcase. Finally steel sleeves were welded on to allow the cooling system to keep the engine temperature under control.

The D.II was not a massive success, though it did power some early Fokker and Albatros designs it was soon superseeded by Mercedes next product, the D.III.

The first versions of the D.III were completed in 1914 and could produce 160hp, though a number of developments in the years that followed saw that figure rise to 180hp by the middle of 1918.

Whilst the engine would eventually become a mainstay for fighter designs, in 1914 the dimensions were simply too large for this to be a practical application so the engine was kept back for bombers and recanassaince designs.

The D.III eventually came into its own as the aircraft “grew into it”. Where the engine really started to gain a reputation was in the Albatros D.I, the first of what would become one of the most famous German designs of the war.

By the middle of 1917, the early 120hp version of the D.III was phased out of production, soon to be replaced by the 170hp D.IIIa.

In intial versions of the engine the tops of the piston were concave, in this higher power example they were flat topped. This change allowed maximum compression in the cylinders, producing more power. The “a” model only saw a short service run, providing the Albatros D.III with a suitable power-plant.

By late 1917 a more extensive re-design was launched. This time it was named the D.IIIaü, which could produce 180-200hp. The piston shape was changed once again, this time to a domed profile, which allowed yet more compression. A new carburettor provided improved performance at the higher altitudes at which air combat was now taking place.

Widely regarded as the best fighter of the war, the Fokker D.VII was powered by a Mercedes D.III as was the Albatros D.Va, no doubt the engine played a key part in the success of these types.

The final version of the D.III came in late 1918 when the D.IIIav was introduced, this engine was rated at 200-217hp and was possibly the first production engine to use aluminium cylinders. These new cylinders were also longer which increased the compression yet again. The lighter weight meant that these pistons could move faster as well. All of these factors also allowed the maximum rpm rating of the design to move up to 1600, which provided much of the performance increase.

Airworthy D.IIIs are inclreasingly appearing, at least in new build form, with the continued production of  Albatros reproductions being put together down in New Zealand by the Vintage Aviator team.

While the Mercedes was no doubt an impressive engine it would have without question have been phased out by the BMW IIIa, had more examples of the type been available during 1918.

BMW IIIa

Long before BMW became the car building multi-national we all know today they built aero engines. The first product to ever come out of the BMW works was the IIIa. It proved to be a very popular design with great performance.

The engine was quite a late entry into the war, with the design first being registered in May 1917. The basic principals and design were kept inline with what Mercedes had done with their D.III. This was chosen as it was known to be a reliable and fairly powerful design. BMW followed Mercedes’ lead and opted for as high a compression as they could achieve.

The engine was an impressive design from the start but it became even better when Max Friz, the designer, installed a throttle butterfly into the high altitute carburettor. This small change meant that the engine could provide full power even at high altitude.

This allowed the engine to produce 200hp all the way up to 6,500 feet.

Such was the strength of this engine, particularly at higher altitudes, that it really gave whichever aircraft it was attached to superiority. The Fokker D.VIIs that were fitted with the BMW were able to out climb basically anything they came across.

Clerget

As briefly discussed in the first part of this series, the engine company clerget announced their presence, as discussed they were unique at the time in that a lot of their engine components were made of aluminium alloy. They also featured a throttle and were considered to be more reliable than other rotary designs.

Before the war the company had seen success with the 7Z engine, having been used in certain versions of the Avro 504.

However the company’s shining light was to be the 9B. This engine may have run in 1913, but it did not see any service until the war began.

As the name suggests the 9B was a 9 Cylinder rotary, it was manufactured in both France and Britain like a number of the Great War engines.

two versions of this engine were made, the started 9B (1913) put out 130hp, while the extended stroke 9Bf (1915) which could put out 140 horsepower. There were 1,300 and 600 examples built of these engines respectively.

One company Clerget had a long running relationship with one particular British company during the war, Sopwith. The 9B was used as early as the Sopwith Baby, right through to the Camel, including the Triplane and 1 1/2 Strutter. The Bristol M1c Monoplane also made use of this high power rotary.

The longer stroke 140hp engine was used on later versions of the Camel.

Bentley

While the Clerget was an immensely powerful engine and very important to the British war hopes, it was very expensive to licence produce and they could be prone to overheating.

W.O Bentley arrived on the scene at this point, being brought in to create a new design which would be more reliable and hopefully cheaper.

What came out of this design was the BR1, an engine of aluminium cylinders, with cast iron liners. Another new feature for this engine was the introduction of dual ignition, providing a much more reliable engine than many rotaries. The end product had 150hp when it was first run, a 10hp increase over the 9bf currently being used for the Camel.

Though the BR1 was clearly a better option for the Sopwith design, it was never really built in the numbers required to replace it, Clerget production continued.

W.O Bentley followed up this design in 1916 with the BR.2, this engine was another 9 Cylinder rotary, it is claimed by many to be the ultimate development of rotary engine design. It put out an impressive 230hp!

This initial version was followed by a 245hp version of the engine was introduced in 1918.

The main aircraft the engine was used for was the Camel’s replacement, the Sopwith Snipe. The engine was used to power the aircraft until 1926.

This engine ultimately marked the peak of rotary engine design. From this point on it would be radial engines and inline power-plants which would supply much of aviation power in the future.

Below is a video of a BR-2 engine running in a Sopwith Snipe at Old Warden:

Liberty

On the subject of inline engines, on important example which first ran in 1917 was the Liberty V12 engine. This came about from the United States wanting to build an engine that would be just as reliable if not surpass the engines currently being built in Britain.

The first prototype of this new design was assembled as an eight cylinder in July 1917, by August this design had been successfully run in 12 cylinder form. It wasn’t long before the War Department had ordered 22,500 engines.

This engine certainly showed the way that aero engines would be heading, it could put out an impressive 449hp.

The main application for this engine was the DH4, which was largely used post war as a mail and touring aircraft in the United States, though a few engines saw service during the war while being used in the type.

A few of these engines remain on display in museums around the world, one even remains airworthy. Once again in the hands of The Vintage Aviator Limited powering their DH4 reproduction which flew late last year.

Rolls Royce Falcon

Rolls Royce played a huge part in aviation power-plants during the Second World War and while there were less rolls royce engines during the war they were no less impressive.

The most impressive of these is the Falcon, an engine which first joined production in 1916 and had a huge production run right through until 1927. The Flacon provided 288hp from its 12 Cylinders and is best known for powering the Bristol F2B, in fact many of these engines can be seen powering bristols around the world.

The engine runs quite slow and is incredibly quiet, making the Bristol F2b a wonderfully unique sight.

Post War Power: 

As can be seen above, engine development came on in leaps and bounds during the war, as so often is the case with technology in a conflict, in many ways it had reached such a peak that for the years after the war many of the engines developed in 1917 and 1918 remained in general use for years to come.

The Liberty V12s remained in regular use with the DH4 designs and Sopwith Snipes flew on well into the 20s, finally being retired in 1926, so even rotary power remained a viable option for some years. Of course we all know how well BMW did in their post war career.

I undoubtedly will have missed out some manufacturers in this post, Gnome and La Rhône notably, this is largely because there designs did not take huge leaps in the war years from what they had pre war and were also subject to the German Licence copies post war.

The next post in this series will look at how things geared up during the interwar years as the roaring V12s and rumbling radials of the Second World War started to take shape.