23 replies to this topic

[m9a3r5i7o2n]

Darracq V-8 Compression Ratio. 1904 engine.
I’ve been looking all over the Internet for the compression ratio
of this engine even using the 100 hp four cylinder but to no avail.
Using a 4.5 to 1 C.R. this engine has more cubic inches in the
combustion chamber than some engines have total piston displacement.

A lot of old aircraft V-8 engines didn’t have 1551cubic inches
especially with such a short stroke. This is the size of engine that the
French needed in World War-1 It may be unfortunate that this wasn’t used
instead of the one of the de Dion-Bouton in the Hispano-Suiza. This may
have been due to E. Henri who may have been working on both engines.

M.L. Anderson

[Allan Lupton]

Originally posted by m9a3r5i7o2n
Darracq V-8 Compression Ratio. 1904 engine.
I’ve been looking all over the Internet for the compression ratio
of this engine even using the 100 hp four cylinder but to no avail.
Using a 4.5 to 1 C.R. this engine has more cubic inches in the
combustion chamber than some engines have total piston displacement.

The 200hp Darracq has quite a large engine, but not of very special design, so the CR would be as you say, 4 to 4½ to 1, as typical of its time. It was not common to quote CR at the time, so period references probably won't help. Even Pomeroy, when discussing 1906-onwards GP cars 50-odd years later, has no information on CR.

PS Why do you need to know, by the way?

[robert dick]

The contemporary press quoted the exact compression ratios in a few cases only. I could not find the exact ratio of the Darracq.
In general, the compression ratio of the 1905 Bennett and 1906 Grand Prix cars was between 4.5 and 5 to 1 - with 4 to 1 in some conservative cases.
Examples - between 1901 and -16 :
4.5 to 1 was the compression ratio used in the 1901 Mercedes for the race from Paris to Berlin,
4.7 to 1 was the ratio of the 1906 Grand Prix Mercedes,
5.5 to 1 was the ratio of the 1912 Grand Prix Peugeot,
4.7 to 1 was the ratio of the WWI Hispano V-8 aero-engine in original form, later 5.3 to 1.

Revival of the Darracq :

and

[wheelock]

Thanks for posting those video links!
That engine looks and sounds great.
I would love to seen it on the move.



Mark

[Boniver]

www.darracq-v8.co.uk

[m9a3r5i7o2n]

My guess of 4.5 to 1 is as close as I am going to get on this one. The reason for the desire is that I was drawing a sketch of what I believe the combustion chamber may look like. Using a 4.5 to one it is one huge combustion chamber compared to others.

170mm = 6.6929”.
140mm = 5.5118”.
1551.33 cubic inches.
V1= 193.9164 cubic inches.
V2 = 55.4047 cubic inches.
V1 + V2 = 249.3211258 cubic inches/V2 = 4.5 to 1 Comp. Ratio.
Height of V2 = 1.5748”.

After drawing the sketch I believe that the intake and the exhaust were around 2.000” diameter and absolutely not more than 2.770”.

Also since we haven’t a picture or any details of the cam lobe or the valve lift we haven’t any idea of the actual valve action.

What is also sad is we haven’t any idea of the full nature of the 100 hp four cylinder engine either or at least on the Internet. This since the V-8 was supposedly an enlargement of the four cyl. If we had a lot of details of the four cylinder it would answer a lot questions.

M.L. Anderson

[David Beard]

Originally posted by robert dick


Revival of the Darracq :

and

Wonderful. Not a laptop computer to be seen!

[robert dick]

Originally posted by m9a3r5i7o2n
... the intake and the exhaust were around 2.000” diameter... a picture or any details of the cam lobe or the valve lift...

According to the photo "looking up into the twin cylinder pot" :
http://www.isdm.co.u...nders/index.htm
valve diameter was around 44 mm or 1.75 inch.

"Detail of a camshaft lobe" :
http://www.isdm.co.u...shaft/index.htm

The layout of the 4-cylinder Bennett and Grand Prix engines was the same.
The original 1905 OHV 4-cylinder had the dimensions of 150/140 mm, the 1906 Grand Prix engine the dimensions of 180/150 mm.
The 4-cylinders had two ignition systems, a spark plug ignition via high tension magneto, and an additional low tension/wipe contact ignition with small vertical rods operated by the camshaft.
It seems that the V-8 retained only the high tension/spark plug system and used the mounting points of the wipe contacts as connection to the water pump/radiator.

[Hans Etzrodt]

1906 Benoite hill climb won by Darracq?

The French Benoite hill climb on November 4, 1906 was won by the 200 hp Darracq racecar. I found this information on the website http://www.darracq-v8.co.uk/ , mentioned above by Boniver. I would like to hear more about this obscure event, like nearest town, length of course and then obviously the driver, who on that day set the fastest time with the 200 hp Darracq racecar. Did other meetings take place at Benoite and if so, when? What magazines had reported about this little hill climb? I found nothing in my copies of Omnia, AAZ or AUTOMOBIL-REVUE.

[robert dick]

Course d'Origny Sainte-Benoite - 4th November 1906 - near Saint-Quentin - distance = 2 km = 1 km hillclimb + 1 km sprint - organized by the newpaper Les Sports.
54 starters
results :
voitures de 650 à 1000 kilos
1) Lee Guinness (Darracq) - 1 min 0 sec 2/5
2) Cecil Edge (Napier) - 1 min 6 sec 4/5

voitures légères de 400 à 650 kilos
1) Demogeot (Darracq) - 1 min 8 sec 2/5
2) Villemain (Bayard-Clément) - 1 min 20 sec

voiturettes de 250 à 400 kilos
1) Vivet (Darracq) - 1 min 44 sec 1/5

Source = La France Automobile
It is not explicitly mentioned that Guinness was at the wheel of the V-8 - as it is the case in the results for Dourdan (Darracq 200 ch 8 cyl) and Gaillon (200 ch).
The V-8 was heavier than 1000 kgs - possible that Guinness drove a Grand Prix 4-cylinder - or the class was open (La France Automobile wrote "650 à 1000 kilos").

[m9a3r5i7o2n]

# 1. 150mm x 140mm by four cylinders = 931.718 cubic inches or 15.269 liters.
# 2. 180mm x 150mm by four cylinders = 603.891 cubic inches or 9.897 liters.
The camshaft lobes are very rudimentary as would be expected of engines at
that time. Were you able to measure the two dimensions from across the lobe,
that is 90 degrees to the lobe and the one across the lobe itself? This would give
us the camshaft lifts and as the rocker arms look as if they are equidistance
C/L to C/L the lift should be the same as if they were pushing the valve itself.

There are a lot of interesting things about this engine such as the rocker arms being on
studs like a Chevy V-8 only without the ball rockers. Also the odd offset of the valves
instead of being straight inline with the longitudinal axis of the engine.

I don’t know if anyone has considered the large coolant tank and its purpose, but it looks
a lot like the idea of the 1930 Oakland V-8 radiator, the idea was the coolant tank outlet
from the engine was to condense the steam particles from the coolant before they got into
the radiators pipes themselves and conserve alcohol. If you notice the pipes appear to be
only about half way up the side of the cylindrical tank and their thinking maybe somewhat
similar to that of Oakland altho for a slightly different reason. The tank on the Oakland was
much smaller than that of the Darracq.

I haven’t figured just why the valves are offset the way they are but it may have something to
do with the shortening of the exhaust passages in the block. Ford in 1932 should have looked
into this engine.

The ignition doesn’t seem to have any automatic advance or ******, but did it have a method
of doing this by hand such as dash mounted cable controlled advance and ******? If it didn’t it
must be hell to start and overheating would be a problem in the ******** position also with a
bad effect on the hp output.

More to follow!

M. L. Anderson

[Tim Murray]

Originally posted by m9a3r5i7o2n
If it didn’t it must be hell to start . . .

This may be of interest. It is taken from the book Under My Bonnet by Neville Minchin (referenced in the Darracq website linked to by Boniver in post 5 above) :

Starting the 200 was quite a ceremony. Push starting on one block was the method employed, the other block being on half compression. Someone had to run alongside to slam down the half compression lever as soon as she fired, at the same time having to jump quickly out of the way of the rear wheel. If one achieved this without either falling or being knocked over, one had done very well.

[Hans Etzrodt]

Originally posted by robert dick
Course d'Origny Sainte-Benoite - 4th November 1906 - near Saint-Quentin - distance = 2 km = 1 km hillclimb + 1 km sprint - organized by the newpaper Les Sports.
54 starters...

Robert - thank you for your clarification, which enabled me to amend the Hill Climb Winners list with the forthcoming February update. So, "Benoite" stood for the Origny-Sainte Benoîte event, about 15 km east of St. Quentin.

[Ray Bell]

Marion...

I'd very much like to see a diagram of the valve layout.

Hans...

How come you've let Robert get away with witholding this information from you for so long?

Robert...

Your resources are amazing!

[m9a3r5i7o2n]

One thing I failed to mentioned is the camshaft and the need of extra lobes only on a 90 degree
Crankshaft engines therefore this engine only needed the same amount of lobes as a four cylinder
engine. One must remember that a 180 degree crankshaft V-8 is actually two four cylinder
engines operating at 90 degrees to one another and it only needed 8 lobes on the camshaft.

I am somewhat surprised to hear that it even had quieting ramps as one must remember that
camshafts were pretty crude even up to the 1930’s, very large manufacturers to the contrary
due to less of a money/time factor. The main example I have of this is the Buick camshafts
which used 270 degree duration cams when the usual timing was about 230/240 degrees. At the
time of the Darracq V-8 the use of straight line flanks were being used, as this also seems to be
evident on the pictures of the engine labeled, “Looking along the Camshaft”. Even the camshaft
of the 1939 V-8 Tripoli Mercedes were still using lobes made up of a series of radii with offset
swing points and very good ones at that and even straight line flanks of small length.

The next thing I would like of Robert is just how they adjusted the valve lash; it is likely at the top
of the push rod but isn’t very clear. The ends of the push appear to be spherical,
therefore a little bit of an angle could be tolerated on either or both of the two vertical planes.

Ray; I am trying to get the sketches on the Internet but will keep trying as I would like to have a
critique of my work to see if it even looks like the original, angle of the valves may be 30 degrees .
Having no picture of the cylinder directly from the top is a distinct disadvantage, altho I believe
that it is very very likely 30 degrees after drawing both. Also the sparkplugs are inserted at about
15 degree angle all of these are of the top view.

M.L. Anderson

[m9a3r5i7o2n]

Question just what does this phrase imply? Two blocks of the l'Auverne type.

Is it the valve system or is it the separate blocks without removeable cylinder heads as I have never seen this phrase anywhere but here. If it similar it should have stated Four blocks.

http://www.v8darracq.co.uk/car.htm

M. L. Anderson

[robert dick]

The 1905 Bennett Cup and the French elimination race were run on the Circuit de l'Auvergne (or Circuit d'Auvergne) near Clermont-Ferrand.
The Auvergne is the name of the region.

So "two blocks of the Auverne type" = the V-8 was composed of two blocks as used in the 1905 Bennett cars during the French elimination on the Circuit de l'Auvergne.

[m9a3r5i7o2n]

To Robert Dick; When I ran up the word it gave me all the information about the region but it did not occur to me that it is as you say but it does make sense.
Thank you, Yours, M.L. Anderson

[m9a3r5i7o2n]

Here is the Darracq combustion combustion chamber as best I can do. The top view is fairly good but the side part is not so good except it does show the size of it at 4.5 to 1 compresstion ratio but without radii and other stuff! Now if it just works???

https://home.comcast...ION_CHAMBER.JPG

M.L. Anderson

[Ray Bell]

It works, Marion...

But what are the red and blue sections?

And from that site, does 'four throw crank' possibly mean they used a 90° crankshaft?

[m9a3r5i7o2n]

Quote from Ray Bell;
It works, Marion...
But what are the red and blue sections?
And from that site, does “four throw crank”, possibly mean they used a 90° crankshaft?



Ray; the Red is the exhaust valve, Blue is the intake valve, very small compared to the
2.272” diameter area that seems to have been available for the valve sizes.
The four throw crank is just the four throws on a regular four cylinder. a picture of it
is shown on one of the posts which I have, or will post. It is defiantly not a 90 degree
crank.
I have also changed the diameter to 1.750” from the 1.440”
A picture of the crankshaft is shown at a place in the upper section of the first page
called the “Gallery”.

http://www.v8darracq.co.uk/car.htm

http://perso.orange....etromobile4.htm

http://www.isdm.co.u...racq/technical/

http://www.isdm.co.u...rracq/index.htm

M.L. Anderson

[m9a3r5i7o2n]

The large tank at the top of the engine is a hangover from the early engine and was there when

the coolant system was without a coolant pump and using only thermo-siphon for the water movement.
If one analyses the tank and tries to visualize the water flow it looks to me as if the inlets are
misplaced in the middle of the tank instead of in the bottom of the tank. Also is there
a barrier to prevent hot water from going too quickly to the outlet pipes into the engine and
not having time enough to stop steam from forming as the hot water comes into the tank?
All of the above indicates that the tank should have been a horizontal radiator and leaning at
about three times the thickness of the radiator.

Shouldn’t the inlet pipes go into the bottom of the tank at the opposite end from the outlet to
help this natural thermo-siphon flow pattern? Also one must remember that after the coolant
pump was installed the tank may not have been needed. They were experimenting we know.
The original radiator was made up of what appears to be round tubes when flattened tubes,
and more of them, would have been more effective. Also wouldn’t making the tank lean down
slightly on the outlet (Front) end help the natural flow of the water? If it had a barrier on that
end making it lean. Since this was basically an experimental engine, somewhat proven by the
various changes, they shouldn’t have needed an extra radiator. Altho radiators at this time were
still in the very experimental stage also.

http://home.comcast....OLANT__TANK.JPG

M.L.Anderson




http://home.comcast....OLANT__TANK.JPG

[m9a3r5i7o2n]

Just finishing the camshaft lobe sketch and it is not as radical time wise as it
looked at first as it appears to be about 220 degrees, if it is as I believe the flaw is in the
flank angles instead of in the timing. A lobe of this type is usually accompanied with followers
of radius contour to help it follow the lobe without excessive jump. One picture shows a group
of odd shaped objects near the cam but as they weren’t removed from the engine it is difficult to
tell if they are the followers or not and especially if they are radiused at the contact points.
Without radii on either the lobe or the follower this would make the valve system very abrupt
and affecting the engines smoothness.

My sketches would be with a very odd shaped large diameter follower, on which the follower end
that would have an offset radius and a grooved Outside Diameter as to prevent rotation whereas a roller might be somewhat easier to purchase or machine. Of course it also might be easier to just
grind a new camshaft lobe with the proper radii.

https://home.comcast...BE_FOLLOWER.JPG

https://home.comcast...MSHAFT_LOBE.JPG

M.L. Anderson

[ice man cometh]

Originally posted by wheelock
Thanks for posting those video links!
That engine looks and sounds great.
I would love to seen it on the move.



Mark

Mark see my post re darracq and beast of turin to appear at saltburn on 26th june 2009 100yrs since world land speed record email smerc190e@gmail.com for more info