Renault 80 hp and RAF 1a, A Structural Comparison and a Question

[MerlinV]

Greetings,

I have been collecting references of both the Renault 80 Hp Aero engine and the RAF 1a in order to scratch build BE Aircraft powered by both examples.

I am of the understanding that the RAF 1a was developed from the Renault. It would certainly seem to be the case at first glance.

My question involves the positioning of the cylinders. All of the drawings and images that I am able to find of the RAF 1a show the cylinder banks slightly offset... In fact, I know from the RAF manual that this is the case. I am surprised then, to find all references to the Renault showing the cylinder banks aligned with no offset.

Can anybody confirm for me that this is the case?

Thanks,

Hugh

['14-'18aviationcollector]

Hi Hugh,

I do not specifically know the answer to your question, and I hope I am not showing my ignorance by replying! I have thought about this too, but originally regarding car engines. Still, I think the principle would be the same. I think all V8 engines have offset cylinder banks, don't they? I imagine they must have offset cylinder banks, unless some manufacturers figured out a way to have the conrods connect to the crankshaft along the same centreline with some sort of intermeshing bearing system at the crankshaft end of the con rod. As far as I am aware, most manufacturers simply place one conrod in front of the other, which results in slightly offset cylinder banks. I hope this helps!!!!

[Ransom E. Olds]

There are a number of clever ways to produce a vee-type engine in which the cylinders are directly opposite one another--blade and fork is one; also the rod of one cylinder can be slaved to its opposite number in the other bank. Since the RAF had offset cylinders I'd think the Renault did too, but the pics I've been able to bring up are infuriating in their visual ambiguity: the cylinders seem to be offset but perhaps the camera has lied. Maybe someone with a Renault near at hand can be persuaded to climb up directly above it for a non-perspective image. Ransom

[YavorD]

As much as I know, air-cooled 90-degree Renault V4 (25 hp), V8 (70/80 hp) and 60-degree V12 (100+ hp) were designed with asymmetric con rods and non-staggered cylinders.
An illustration of a latter engine can be found here.

Regards,
Yavor

[m9a3r5i7o2n]

Greetings, Hugh
The first V-8 of record was the Levavasseur-Antoinette of 1903 which had fork and blade connecting Rods.

Much of this below is gleaned from the book of Glenn D. Angle, “Airplane Engine Encyclopedia”, First Edition 1921.

Renault V-8 80c.v. engine.
The Connecting Rod assembly of the Renault is somewhat of the same type as the Sunbeam-Arab, that is it was articulating. A miserable failure for the Arab on this type of engine, far worse than the side by side (cote a cote) connecting rods of most V style engines. Both articulating and fork and blade connecting rods also produce cylinders that are directly opposite from one another. Side by side connecting rods produce a cylinder block that is staggered from side to side by the width of one Connecting Rod. For example if the Connecting Rod is nominally one inch wide the cylinders on one side of the block are nominally one inch in front or back of the opposite side cylinders.
On page 414 as follows:
The 80 c.v. model had a 105mm (4.134”) bore, 130mm (5.118”) stroke and 6.067 liters (549.67 c.i.) piston displacement. This engine had a compression ratio of 4.1 to one. This was said to actually develop 88 c.v. at 1800r.p.m. The fuel consumption was reported to be .772 lbs. c.v. hour. And the oil consumption as .007 lbs per hour. Other than dimensions, the only other important change was the use of articulated connecting rods. As a result, corresponding cylinders on each row were arranged directly opposite. The weight was said to be 463 lbs (210.455kg) or 5.78 lbs. per rated c.v.
Just why this design didn't get the vibration of the Sunbeam Arab I don't know but I suspect that it was due to the fact the Renault didn't have the stroke increase on one side for some reason or another as did the Sunbeam-Arab. This due to the fact that the offset of the Knuckle joint may have been at 112.5 degrees instead of the different angle of 106.903 degrees of the Arab connecting rod.
This arrangement of Connecting Rods has nothing to do with the bank angle which is 90 degrees!

Side by side connecting rods in French are sometimes referred to as, “côte à côte .
As closely as I can tell the crankshaft had 5 main bearings, the same as the 70 and 75 C.V. models. This same picture, 70 and 75 c.v. shows the side by side con rods but the text for the 80 c.v. engine is as stated above, articulated con rods, a mistake for a V-8 engine.


Same book only about the R.A.F.-1A pages 397 to page 399. This engine was also made in 1B,1C,1D and as best as I can tell even a 1E model using cylinders from another engine apparently a 12 cylinder version, R.A.F.4E.
105h.p. Weight 440 lbs. 4.2 to 1 c.r.
The propeller speed was reduced by plain type reduction gears which, together with the cowling employed for directing the air against the cylinders, gave the engine the appearance of the well known Renault design of which it was a development. The pictures of this engine show it to be an “F” head design with intakes in the lower part of the combustion chamber and the exhaust in the upper part of the cylinder head area.
Both the Renault and the R.A.F. 1 series engine have reduction boxes but the pictures I have are almost completely different in appearance.
Page 414. Partial Quotes for the R.A.F. 1A. Development of the R.A.F.1 was undertaken in 1913. An air-cooled V-8 at 90 degree bank angle, 100mm bore (3.937”) & 140mm stroke (5.118”) rated at 90 h.p. 8.796 liters (537.44 c.i.) piston displacement.

The valve system is of the “F” head design overhead exhaust rocker arm actuated and in-block intake valve direct action from camshaft.

Five main bearing crankshaft.

Outside of the fact that these two engines being air-cooled V-8 engines the front view of the gearbox area has little in common.

Of the two engines the R.A.F.1D at a claimed 150 h.p. is the most interesting as it used an aluminum cylinder head but used overhead valves unfortunately it hasn't a picture.
The only air-cooled V-8 engine worth anything was the German Argus used in WW-2. Oddly one of the things that are in the Odd Things Happening is the use of the 130mm stroke of the original Levavasseur -Antoinette V-8 engine. Unfortunately they didn't use the same 130mm bore.

I have rambled in this but when I saw the articulated rods and comparing it to the Sunbeam-Arab was inevitable. This engine had to have a 180 degree crankshaft just like the Arab, Hispano-Suize and all other V-8s until 1923.

Yours, M.L. Anderson

[MerlinV]

Thanks Yavor,
that is the conclusion that I have come to as well.
It is the same configuration (Con Rod wise) as the Hisso and Wolseley Viper.
That is, Assymetric Con Rod ends and Aligned Cylinder banks.

Thankyou all for your input.

Cheers,

Hugh

[MerlinV]

Thankyou Mr Anderson for your very informative response.
Am I right in thinking that the Valve Cam was driven from the Reduced Gear of the Gear box in BOTH cases?

Thanks again,

Hugh

[m9a3r5i7o2n]

Hugh; April 2 Wednesday,
The only picture I have of the R.A.F. engine shows the Pinion wheel in a position that very well could be on the same centerline as the camshaft but this in on the R.A.F.-1A engine. This is on a ¾ view of the front left hand side. This view is completely different from the one on the other page which is a direct rear end view of a R.A.F. 1A engine. I will have to study it some more to see if I can make a better determination of the whole layout by comparing it to the text as thoroughly as I can.

The book by Alec Lumsden, “BRITISH PISTON AERO-ENGINES”, pages 221-223 has some information but the pictures are of little value as they are in the aircraft and not very informative. The statement is made that the 90 h.p. engine is based on the 90c.v. Renault engine and the propeller ratio was .5 to 1. Camshaft in the vee, 90 degree vee engine. Engine turns counter clockwise pilots view.

After studying this for about an hour or more and comparing it to the picture of the French Renault engine picture I would say that the camshaft was driving the propeller on both of these engines.
Of the 1A version about 2860 were delivered.
Of the 1B version about 114 were delivered.
Of the 1C, 1D, 1E version none were delivered.
With the above information one can conclude that the it is most likely that both engines had the propeller driven off of the camshaft. Also that the one picture I have of the R.A.F. 1A engine is of the rear view and not the front view. Also this picture has the carburetors in full view which I believe were definitely on the rear and the reduction box was on the front!

Image:Renault 80.jpg - Wikimedia Commons

Yours, M.L. Anderson

[MerlinV]

Yes,
the RAF 1a had the twin Claudel Hobson Carbies slung below the rear of the engine. The fuel air mix was transfered up through pipes integrated into the casting of the rear cover plate and then into the induction pipes that ran between the V of the cylinder banks.
I will have to pour over the references I have for the RAF engine again and try to glean for sure the matter of the cam shaft and Prop shaft.
One of the references I have for the Renault, which is basically an operating manual, shows a cross section which seems to indicate for sure that it is in fact the case that the Prop shaft and the cam shaft are linked.
This would confirm the 0.5 to 1.0 (1:2) ratio indicated.

Cheers,

Hugh

[m9a3r5i7o2n]

Hugh; I don't know it you have seen these or not but might be worth a try.
M. L. Anderson

Fact Sheets : R.A.F. 1A : R.A.F. 1A

Image:Renault 80.jpg - Wikimedia Commons

B2540 Aero engine, Renault , V8, type A52, 85hp, metal, made by Wolseley Motors, Birmingham, England, 1915 - Powerhouse Museum Collection