Can we compare the Vickers Venom and the Roussel 30? (1 Viewer)

[yulzari]

Both have similar small engines yet have period adequate performances in prototype form.

Vickers Venom - Wikipedia

en.wikipedia.org

Roussel R-30 - Wikipedia

en.wikipedia.org

Gnome-Rhône 14M - Wikipedia

en.wikipedia.org

Bristol Aquila - Wikipedia

en.wikipedia.org

I note that the Roussel has both a heavier engine and armament (in both senses of 'heavier') and that the Vickers had an almost one off engine.

 

[YavorD]

Somehow I like the Vickers Venom. It can be an excellent advanced trainer if there is a production facility somewhere with daily output of at least 10 Aquila sleave-valve engines

 

[tomo pauk]

Both aircraft were mnasterclass in the 'how to hide my guns' category
Russel was at least powered by an engine that was in series production. Both aircraft might've received the T-W Junior if they survived as production aircraft by 1940-ish. How much of firepower and protection they would've gotten by that time is everyone's guess.

 

[yulzari]

Both aircraft were mnasterclass in the 'how to hide my guns' category
Russel was at least powered by an engine that was in series production. Both aircraft might've received the T-W Junior if they survived as production aircraft by 1940-ish. How much of firepower and protection they would've gotten by that time is everyone's guess.

An extra 150kg is a lot of weight to put right on the front for such small aeroplanes but the power is going to be useful to carry any extra weight. The Gnome-Rhône 14M might be a better swap into the Venom being lighter than the Twin Wasp Junior and ideal for Alvin's to build under their existing licence arrangements and production facilities.

The Kawasaki Ki27 looks very much like a big wing version of the same class. Naval versions of the two types could fit existing lifts and hangers. For the Royal Navy it would bridge the gap between the Nimrod and Seafire as a fleet fighter and leave the Fulmar for strike, reconnaissance and CAP and be infinitely more useful than the Blackburn Roc. Essentially it mirrors the later successful pairing of the Seafire and Firefly. A single speed supercharger is adequate for the naval rôle. The 14M got to 750 bhp on 87 octane so a 100 octane optimised version could reasonably be expected to achieve @825 bhp.

The fly in the ointment for the Roussel is not technical but timing. The Venom was a 1936 prototype whilst the Roussel prototype was first flown in 1939. It flew with a 695 bhp engine and was going to be fitted with an 800 bhp version but the BoF intervened. I am not aware of French fuel octanes in 1939 but I suspect it to have been 87.

 

[tomo pauk]

An extra 150kg is a lot of weight to put right on the front for such small aeroplanes but the power is going to be useful to carry any extra weight. The Gnome-Rhône 14M might be a better swap into the Venom being lighter than the Twin Wasp Junior and ideal for Alvin's to build under their existing licence arrangements and production facilities.

Another option for the Venom might've been the Mercury. We add some extra drag and weight, but the engine power gets a substantial increse; with 100 oct fuel and the late 1930s versions, it will do close to 1000 HP.

Idle musing: Aquila would've been an interesting tank engine.

The 14M got to 750 bhp on 87 octane so a 100 octane optimised version could reasonably be expected to achieve @825 bhp.

Germans state: 1min rating for take off is 700 HP @ 1.50 ata. At 4000m, it was good for 650 HP for 30 min, at 1.25 ata; Mercury did some 200 HP more there.
How much extra boost the 14M can withstand when fueled with 100 oct fuel?

 

[Elan Vital]

Idle musing: Aquila would've been an interesting tank engine.

Same ballpark as the R-975.

Germans state: 1min rating for take off is 700 HP @ 1.50 ata. At 4000m, it was good for 650 HP for 30 min, at 1.25 ata; Mercury did some 200 HP more there.

How much extra boost the 14M can withstand when fueled with 100 oct fuel?

I don't know if this helps answer your question, but the 1939-40 14S (which was a 14R-ed 14M) required 100 octane fuel.

The takeoff manifold pressure of the 14M became the overcharge pressure of the 14S (1100mm Hg or 1.447 ata), giving up to 910 hp at 1000m and generally over 800hp below 4000m.

The 14S also introduced a 1250mm Hg setting (1.65 ata) at takeoff giving 1000 hp.

Now, without the deep structural and supercharger modifications of the 14S, would a 14M with 100 octane fuel be able to use that fuel?

 

[Shortround6]

Both have similar small engines yet have period adequate performances in prototype form.

And very little growth potential.
Also comparing a plane with a variable pitch prop to fixed pitch is starting to stack the deck.
The people pushing the Aquila engine had drunk of the sleeve valve Kool-Aid that was of the syrup variety and far beyond the normal liquid variety.
A 15.6 liter engine may have sounded good to the accountants (penny pinchers in Whitehall) but it rather depends on your opponent's building cheap, low powered aircraft.
Building fighters using an engine not much different in power to the P&W Wasp used in the P-26 or the Harvard trainer was not going to end well.

 

[YavorD]

Aquila IV (1938 spec), source Neil Stirling , a set of engine charts from late 1930s

 

[tomo pauk]

Same ballpark as the R-975.

Yes indeed.

I don't know if this helps answer your question, but the 1939-40 14S (which was a 14R-ed 14M) required 100 octane fuel.

Was the 14S available in 1939-40?

Now, without the deep structural and supercharger modifications of the 14S, would a 14M with 100 octane fuel be able to use that fuel?

A point I was trying to make

Aquila IV (1938 spec), source Neil Stirling , a set of engine charts from late 1930s

The power at 15000 ft is "interesting" - about half of what the Mercuries on the Gladiator or on the Bleneim I and IV were making.

 

[Shortround6]

There are two problems using 100 octane fuel.
1. Will the engine survive making the higher power for more than a few seconds (not break the crankshaft and con-rods),
2. Will the engine survive making the higher power for 3-5 minutes without melting down/overheating due to lack of cooling (lack of fins on air cooled engines).

I have questions about the power charts. A better supercharger can do a lot. but this engine seems to be a miracle. Same power at the same altitude or a little higher while turning 10% slower?
Or making 27% more power while using 22% more intake manifold pressure? Which is paid for how? how much power is being used up in the supercharger to get the higher pressure?
granted a lot of 1930s superchargers were not efficient, but this is a huge improvement.

100 octane fuel as the same BTUs per gallon, it just allows you to cram more fuel into the cylinders without detonating before the sparkplugs fire.

 

[Shortround6]

The power at 15000 ft is "interesting" - about half of what the Mercuries on the Gladiator or on the Bleneim I and IV were making.

So the Venom with Hamilton Standard variable pitch prop and around 500-540hp available can out climb, at low altitudes, a Spitfire I using a wooden fixed pitch prop and using around 650hp? Can only use 2100-2400rpm and 6lbs boost to keep from over speeding the prop below 6000ft.
Wonder how the Venom does climbing at 15-18,000ft?

 

[YavorD]

The power at 15000 ft is "interesting" - about half of what the Mercuries on the Gladiator or on the Bleneim I and IV were making.

Mercury XX (1939 spec) : about 600 hp / 2750 rpm / 15000 feet (no RAM). Not half but about 2/3.

 

[yulzari]

Another option for the Venom might've been the Mercury. We add some extra drag and weight, but the engine power gets a substantial increse; with 100 oct fuel and the late 1930s versions, it will do close to 1000 HP.

The Mercury is surely a mass too far for the Venom airframe. Not to mention needing more wing area. You need a new airframe to carry it. Not to mention being significantly wider.

What we do know is that the Venom came from a large aviation manufacturer. We know what it could do with the best Aquila engine and carried the full x8 .303 Brownings on its maiden flight in 1936. We do know that Alvis sought to make licenced Gnome Rhône 14s which is a feasible fit to the Venom so there is an outline for the performance and the industrial back up to make it if ordered and to do so in time for the war. The Roussel looks promising but too late to make. Ratier should be able to do a constant speed propellors for the engine. Certainly the Venom airframe must be far cheaper, easier and faster to make than a Spitfire and Alvis is an additional maker not impinging upon Rolls Royce nor Bristol. The engine was IOTL developed up to 820 bhp even if the Germans were content with the standard 695 bhp in the engines made for them.

An Alvis engined Venom would make a better candidate for the F5/34 Air Ministry requirement and a Nimrod replacement for the Fleet Air Arm.

Vickers Venom fighter

www.dingeraviation.net

 

[Elan Vital]

Was the 14S available in 1939-40?

Only in testing. The management of the G-R factory at Genevilliers stated on June 5th 1940 to an American mission that "the 14R engine would be available before the end of the year" (2 prototypes were being tested), so no earlier than that for the 14S of similar technology.

 

[Shortround6]

The Mercury is surely a mass too far for the Venom airframe.

Mercury was about 1000lbs (455kg)
G-R 14M was around 410kg?
Aquila was 376kg (?)

What we do know is that the Venom came from a large aviation manufacturer. We know what it could do with the best Aquila engine and carried the full x8 .303 Brownings on its maiden flight

Except that no photo of the Venom with guns seems to exist?

No cartridge slots in the bottom, no patches on the wing leading edge, no visible hatches on top or bottom to load ammo or service guns.

Ratier should be able to do a constant speed propellors for the engine.

As it turned out Ratier could not supply enough propellers for the French Air Force once the war started.

 

[tomo pauk]

Mercury XX (1939 spec) : about 600 hp / 2750 rpm / 15000 feet (no RAM). Not half but about 2/3.

The Mk.XX was not on the Gladiators nor on the Blanheims; the Mk.VIII was, and the Mk.XIV was about to be installed on the Blenheim IV.

The Mercury is surely a mass too far for the Venom airframe. Not to mention needing more wing area. You need a new airframe to carry it. Not to mention being significantly wider.

If Vickers want the RAF to buy the Venom, Mercury is their best bet. It will not be the 1st nor the last aircraft to get a heavier engine.

What we do know is that the Venom came from a large aviation manufacturer. We know what it could do with the best Aquila engine and carried the full x8 .303 Brownings on its maiden flight in 1936.

Yes, it came from the large aviation manufacturer. No, there were no guns, nor ammo, nor any kind of protection.
And yes, I don't believe the manufacturer's figures any single bit.

We do know that Alvis sought to make licenced Gnome Rhône 14s which is a feasible fit to the Venom so there is an outline for the performance and the industrial back up to make it if ordered and to do so in time for the war.

What engine does not gets made and bought in order that 14M is made and bought by the Air Ministry?

The Roussel looks promising but too late to make. Ratier should be able to do a constant speed propellors for the engine. Certainly the Venom airframe must be far cheaper, easier and faster to make than a Spitfire and Alvis is an additional maker not impinging upon Rolls Royce nor Bristol.

Looks can be deceiving. Expecting that it will be able to duke it out vs. the Emil on the even basis requires putting some heavily-rose tinted glasses on.
Spitfire was more than worth the money and effort, and will keep the pilots live longer than either the Roussel or the Venom - and the pilots were what was needded.

The engine was IOTL developed up to 820 bhp

I'd very much like to see some sources backing that up.