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#1 Bjorn Kjer

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Posted 04 May 2010 - 17:36

I have been told Bentley was racing in 1948 , I must have missed out something ??

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#2 Vitesse2

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Posted 04 May 2010 - 19:11

There was a vaguely planned entry for a Bentley in the 1948 Monte Carlo Rally, to be driven by Mike Couper. However, this was not by any means a works entry, although it would have received some works support. The rally was of course cancelled, but Couper did drive a Bentley in the 1949 Monte.

See Chapter 3 of Couper's book "Rallying to Monte Carlo".

#3 taylov

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Posted 04 May 2010 - 19:32

There was a private "Bentley" entry at Le Mans in both 1949 and 1950.

In 1949 HSF Hay and Tommy Wisdom drove to 6th place on distance in car #6, entered as a "Rolls-Bentley". Hay was back in 1950 with Hunter as his co-driver and car #12 finished in 14th place. Ref. "British Cars at Le Mans by Dominique Pascal (1990)

Tony

#4 arttidesco

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Posted 04 May 2010 - 19:44

Eddie Hall racing his 4.2 litre Bentley in South Africa 1948 check the link and scroll down the page, I get the impression before the war he received some support to compete from Bentley which had just been sold to Rplls Royce, however i do not believe his post war efforts were works supported though as always I'll stand to be corrected :-)

BTW is this vehicle up for sale or something it seems to have a facebook page ?

Or am I just being cynical ?

Best



#5 D-Type

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Posted 04 May 2010 - 19:47

The Barnato-Hassan ran in the 1948 Spa 24hrs but failed to finish

#6 Allan Lupton

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Posted 04 May 2010 - 19:47

Soltan Hay had owned the Embiricos Bentley (FXW 6) since 1939 and more than likely raced it if there was anything going. He raced it at le Mans in 1949 of course, finishing 6th and in 1950 (14th)
Eddie Hall was still racing his TT Bentley and came 2nd on scratch (3rd on handicap) in the Fairfield Handicap at Durban on 24 January 1948. He was also at Le Mans in 1950

Edited by Allan Lupton, 04 May 2010 - 19:50.


#7 Vitesse2

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Posted 04 May 2010 - 19:49

There was of course also Eddie Hall, who was racing his works-built "Rolls-Bentley" in South Africa in 1948:

http://forums.autosp...showtopic=79191

#8 Terry Walker

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Posted 05 May 2010 - 04:37

Rolls-Royce bought Bentley in 1931, not in the 1950s. They introduced their own new Bentley in 1933, often called at the time the Rolls-Bentley by the public. WO Bentley himself liked it, but left R-R because he was predominantly an engine designer, and R-R already had their own team of engine designers. He went on to design the V12 Lagonda engine prewar, and also the twin-cam 2.6 litre six used in the small postwar Lagonda and quickly taken up by David Brown for the Aston Martin.

R-R assembled several 4 1/2 litre vintage "WO" Bentleys from parts in the mid-1930s. It's actually possible to own a vintage "WO" Bentley manufactured in 1936!

A number of Bentley Mk 6 specials have been built since the 1960s by throwing away rusted-out late 1940s sedan bodies, moving the engine back a foot or so, and adding simple open sports bodies. They handle well, the 4.2 litre engines have a lot of torque, and the 4 speed box is very slick. They appeared in VSCC or similar club racing.

As a kid I remember reading a novel about a guy and his son resurrecting a vintage Bentley just after the War, and taking to Le Mans, where if I remember right, they won.

#9 RTH

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Posted 05 May 2010 - 05:51

This Terry ?

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#10 Tim Murray

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Posted 05 May 2010 - 07:24

... in which Johnny and Blackie, ably assisted by Mervyn the Welsh engineering wizard (who fits the Bentley with water-cooled disc brakes (!) and downdraught Webers) triumph against all odds, including the evil scheming of the wicked Atlantic team manager/number one driver. Jolly wizard stuff. I loved that book when I first read it as a boy.

#11 packapoo

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Posted 05 May 2010 - 07:32

This Terry ?

Posted Image



That's the one.
Lost mine some years ago :(

#12 elansprint72

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Posted 05 May 2010 - 07:36

... in which Johnny and Blackie, ably assisted by Mervyn the Welsh engineering wizard (who fits the Bentley with water-cooled disc brakes (!) and downdraught Webers) triumph against all odds, including the evil scheming of the wicked Atlantic team manager/number one driver. Jolly wizard stuff. I loved that book when I first read it as a boy.


They got the downdraught Webers to work with that blower on the Speed Six?!!!! :rotfl:

I say!

#13 Tim Murray

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Posted 05 May 2010 - 07:44

Sadly, the supercharger is a figment of the cover artist's imagination. :drunk:

#14 Terry Walker

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Posted 05 May 2010 - 08:06

Blimey, that's it!

#15 RTH

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Posted 05 May 2010 - 08:15

... in which Johnny and Blackie, ably assisted by Mervyn the Welsh engineering wizard (who fits the Bentley with water-cooled disc brakes (!) and downdraught Webers) triumph against all odds, including the evil scheming of the wicked Atlantic team manager/number one driver. Jolly wizard stuff. I loved that book when I first read it as a boy.


Me too Tim, aimed I suppose at a 15yr old boy....... and 45 years later it is still a very good read .

First published in 1953 the jacket says it was 8s 6d quite a bit in those days.
Sam was the mechanic who could make the 20 year old Bentley ( called Diane ) be competitive it was a six cylinder and it had a supercharger.No mention in the book of discs or webers. Their garage was called "The Twenties and Thirties " located on a disused airfield with their own runway test track ( I wonder if Colin Chapman read it ! )

Barnaby James was the evil criminal rival team owner of Atlantic Motors who had trouble with their cooling system (shades of the low drag C-Type ? ) There was a criminal sub plot as well.

Edited by RTH, 05 May 2010 - 08:20.


#16 Tim Murray

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Posted 05 May 2010 - 08:44

First published in 1953 the jacket says it was 8s 6d quite a bit in those days.
Sam was the mechanic who could make the 20 year old Bentley ( called Diane ) be competitive it was a six cylinder and it had a supercharger.No mention in the book of discs or webers. Their garage was called "The Twenties and Thirties " located on a disused airfield with their own runway test track ( I wonder if Colin Chapman read it ! )

Barnaby James was the evil criminal rival team owner of Atlantic Motors who had trouble with their cooling system (shades of the low drag C-Type ? ) There was a criminal sub plot as well.

Well I never. My copy is the 1966 paperback (Puffin) edition, and I've just found that it says 'Rewritten specially for this edition'. So Sam has become Welsh Mervyn, the supercharger has gone, and watercooled disc brakes and triple downdraught Webers have appeared. The garage is called 'Eds and Vins'. The Atlantic cooling system problem is described as having happened at the previous year's race. I wonder what else 'Bruce Carter' (Richard Hough's nom-de-plume) rewrote.
:confused:



#17 VAR1016

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Posted 05 May 2010 - 10:17

Me too Tim, aimed I suppose at a 15yr old boy....... and 45 years later it is still a very good read .

First published in 1953 the jacket says it was 8s 6d quite a bit in those days.
Sam was the mechanic who could make the 20 year old Bentley ( called Diane ) be competitive it was a six cylinder and it had a supercharger.No mention in the book of discs or webers. Their garage was called "The Twenties and Thirties " located on a disused airfield with their own runway test track ( I wonder if Colin Chapman read it ! )

Barnaby James was the evil criminal rival team owner of Atlantic Motors who had trouble with their cooling system (shades of the low drag C-Type ? ) There was a criminal sub plot as well.



I love threads like this!

And the book mentioned reminds me of another example of the genre: it was called "Four-Wheel Drift". Here the young hero had built a racing-car with a "Durham" flat-twin engine, presumably based on the Jowett Bradford! At the end of the story our hero was driving a rich entrepreneur ,who had supported him and brought off a four-wheel drift in the big limousine. Years later I read a story about Peter Collins doing something similar with David Brown in Northern Ireland.

As for the low-drag C-type, at the English Car meeting at Morges last year, there was a chap who has built a perfect replica of the '52 C-type, which was there. He told me that the cause of the over-heating was the water-pump pulley fitted, which was too small causing the pump to cavitate.

Paul

Edited by VAR1016, 05 May 2010 - 10:18.


#18 P.Dron

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Posted 05 May 2010 - 10:54

Might the cover illustration of Speed Six! have been by Richard Hough's then wife, Charlotte (nee Woodyadd)? She was an illustrator of children's books (and later, not that it's relevant, rather unfairly did time at Her Majesty's pleasure for involvement in the 'assisted suicide' of an old woman).

I have a book by Richard Hough, A History of the World's Sports Cars. The frontispiece is a photo of the Speed Six of Carl E. Mueller, reg GF 8507. It's a fine-looking car. Who owns it now? And what is that component on the Speed Six that protrudes from below the radiator, exactly in the position of the Villiers supercharger on Blower Bentleys (and on the car in Speed Six!)? It strikes me that this Speed Six might have been the inspiration for the novel.



#19 VAR1016

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Posted 05 May 2010 - 11:08

Might the cover illustration of Speed Six! have been by Richard Hough's then wife, Charlotte (nee Woodyadd)? She was an illustrator of children's books (and later, not that it's relevant, rather unfairly did time at Her Majesty's pleasure for involvement in the 'assisted suicide' of an old woman).

I have a book by Richard Hough, A History of the World's Sports Cars. The frontispiece is a photo of the Speed Six of Carl E. Mueller, reg GF 8507. It's a fine-looking car. Who owns it now? And what is that component on the Speed Six that protrudes from below the radiator, exactly in the position of the Villiers supercharger on Blower Bentleys (and on the car in Speed Six!)? It strikes me that this Speed Six might have been the inspiration for the novel.



That component looks like a "Dynastart" an optimistically-conceived part that aimed to combine the functions of a dynamo and starter-motor. I imagine that in the case of the Bentley that it was a dynamo, since unless there were subtle gearing inside, I cannot believe that a motor of the period could provide sufficient torque to turn the vast masses of metal inside the Speed Six's engine!

Edited by VAR1016, 05 May 2010 - 11:09.


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#20 Tim Murray

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Posted 05 May 2010 - 11:19

According to Darell Berthon, in the Profile publication on the 6½ litre Bentley, it's the dynamo, a Smith 5 brush Type 2 DAC 5. The separate starter motor was usually a Smith 4LSA, although some 1930 examples had Bosch starters.

#21 VAR1016

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Posted 05 May 2010 - 11:20

According to Darell Berthon, in the Profile publication on the 6½ litre Bentley, it's the dynamo, a Smith 5 brush Type 2 DAC 5. The separate starter motor was usually a Smith 4LSA, although some 1930 examples had Bosch starters.


Thanks Tim, so my suspicions were correct!

#22 Tim Murray

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Posted 05 May 2010 - 11:37

Paul :up:

I have a book by Richard Hough, A History of the World's Sports Cars. The frontispiece is a photo of the Speed Six of Carl E. Mueller, reg GF 8507. It's a fine-looking car. Who owns it now?

This car was being offered for sale by Christie's in 2004:

http://www.classicdr...00.asp?id=12107

and there are recent and period photos of it here:

http://www.vintagebe...ages/gf8507.php

but I can't find any mention of the current owner.

#23 VAR1016

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Posted 05 May 2010 - 12:28

Eddie Hall racing his 4.2 litre Bentley in South Africa 1948 check the link and scroll down the page, I get the impression before the war he received some support to compete from Bentley which had just been sold to Rplls Royce, however i do not believe his post war efforts were works supported though as always I'll stand to be corrected :-)

BTW is this vehicle up for sale or something it seems to have a facebook page ?

Or am I just being cynical ?

Best


Yes I have read this somewhere and would be very interested to know if any details are available of the modifications which I presume were carried out by R-R.



#24 RTH

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Posted 05 May 2010 - 13:50

I love threads like this!

And the book mentioned reminds me of another example of the genre: it was called "Four-Wheel Drift". Here the young hero had built a racing-car with a "Durham" flat-twin engine, presumably based on the Jowett Bradford! At the end of the story our hero was driving a rich entrepreneur ,who had supported him and brought off a four-wheel drift in the big limousine.



Paul


Now I remember reading that book another great read., very well written and a great storyline. I do not have a copy of that but I really would like to get one.


#25 VAR1016

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Posted 05 May 2010 - 14:14

Now I remember reading that book another great read., very well written and a great storyline. I do not have a copy of that but I really would like to get one.


You are fortunate indeed to remember so much! I cannot.

All I recall is the benefactor saying "Order six new Durham engines!" and of course the four-wheel drift I mentioned above.


#26 RTH

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Posted 05 May 2010 - 14:44

You are fortunate indeed to remember so much! I cannot.

All I recall is the benefactor saying "Order six new Durham engines!" and of course the four-wheel drift I mentioned above.


Do we think this is the book ?

http://www.bookfinde.....wheel%20drift


#27 elansprint72

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Posted 05 May 2010 - 15:23

According to Darell Berthon, in the Profile publication on the 6½ litre Bentley, it's the dynamo, a Smith 5 brush Type 2 DAC 5. The separate starter motor was usually a Smith 4LSA, although some 1930 examples had Bosch starters.


Can anyone explain what a 5 brush dynamo is?

My wiring diagram for the six cylinder Bentley engines only shows three terminals, positive, field and earth.

#28 arttidesco

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Posted 05 May 2010 - 16:41

I read the paper back which featured a photograph on the front cover, does any one have a scan of it ?

#29 Tim Murray

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Posted 05 May 2010 - 17:24

Yer tiz:

Posted Image

The cover design is credited to 'Bryan Dunn, using a photograph from the Montagu Motor Museum, Beaulieu'. It looks as if it might have been taken on a hillclimb - anyone recognise the venue?

#30 Allan Lupton

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Posted 05 May 2010 - 17:30

Can anyone explain what a 5 brush dynamo is?

My wiring diagram for the six cylinder Bentley engines only shows three terminals, positive, field and earth.

Quite a lot of starter motors are (were) four-brush (with one terminal and frame return like any two-brush machine). I expect (but do not know) that a five-brush dynamo is a three brush machine with an extra pair of brushes like the four-brush starter. I presume that the four-brush jobs have twice as many field poles as two-brush.
The third-brush dynamo (and therefore the five) uses the extra brush and armature reaction to control the field current which therefore controls the output current. A full desertion on the subject is not appropriate here, but in the 1930s the constant-current device gave way to a constant voltage one which improved battery life and system reliability generally.

#31 Allan Lupton

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Posted 05 May 2010 - 17:33

The cover design is credited to 'Bryan Dunn, using a photograph from the Montagu Motor Museum, Beaulieu'. It looks as if it might have been taken on a hillclimb - anyone recognise the venue?

Most likely to be Firle as BDC ran there for several years just post-war and it has that South Downs look to the background

#32 VAR1016

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Posted 05 May 2010 - 17:36

Yer tiz:

Posted Image

The cover design is credited to 'Bryan Dunn, using a photograph from the Montagu Motor Museum, Beaulieu'. It looks as if it might have been taken on a hillclimb - anyone recognise the venue?


I suspect that it might be Firle in Sussex - the Bentley Drivers' Club used to run hillclimbs there; I went once - in 1964 - a great day out. I still have the programme somewhere. The event was sponsored by WD & H Wills. I recall the prizes included an oak presentation cabinet containing a substantial quantity of Embassy cigarettes.

Paul

Edited by VAR1016, 05 May 2010 - 17:46.


#33 VAR1016

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Posted 05 May 2010 - 17:48

Do we think this is the book ?

http://www.bookfinde.....wheel%20drift


I suppose it must be - it seems that Carter specialised in "Boy's Own" motor-racing adventures!

#34 Tim Murray

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Posted 05 May 2010 - 18:26

Eddie Hall racing his 4.2 litre Bentley in South Africa 1948 check the link and scroll down the page, I get the impression before the war he received some support to compete from Bentley which had just been sold to Rplls Royce, however i do not believe his post war efforts were works supported though as always I'll stand to be corrected :-)


Yes I have read this somewhere and would be very interested to know if any details are available of the modifications which I presume were carried out by R-R.

In the Profile publication on the Bentley 3½ & 4¼ Litre, George A. Oliver wrote:

... and [Hall] was able, by means best known to himself, no doubt, to secure official backing for entry of his 3½ in the 1934 Ulster Tourist Trophy Race. As the last time Derby had taken an official part in competition was as far back as the Alpine Trial of 1913, the magnitude of Hall's achievement may be the more clearly judged.


This backing continued in 1935 and 1936. The modifications to the car are detailed as follows:

1934: Compression raised to 7.35 to 1 and straight-through exhaust fitted, giving 131 bhp. Hartford friction shock absorbers supplemented the existing hydraulics. Fuel tank capacity increased to 26 gallons, and an extra oil tank fitted.

1935: Compression ratio up to 8.35 to 1 plus larger inlet valves, inlet manifold and carburetters, giving 152 bhp. Larger diameter tyres.

1936: Tuned 4¼ litre engine fitted, giving 163 bhp, which had been endurance tested at full throttle for 24 hours.

In 1936 Hall 'had been given permission' to enter Le Mans (hence the engine endurance testing) but the race was of course cancelled that year. There is no mention of any works support for his subsequent efforts.

Edited by Tim Murray, 05 May 2010 - 18:29.


#35 VAR1016

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Posted 05 May 2010 - 19:20

In the Profile publication on the Bentley 3½ & 4¼ Litre, George A. Oliver wrote:



This backing continued in 1935 and 1936. The modifications to the car are detailed as follows:

1934: Compression raised to 7.35 to 1 and straight-through exhaust fitted, giving 131 bhp. Hartford friction shock absorbers supplemented the existing hydraulics. Fuel tank capacity increased to 26 gallons, and an extra oil tank fitted.

1935: Compression ratio up to 8.35 to 1 plus larger inlet valves, inlet manifold and carburetters, giving 152 bhp. Larger diameter tyres.

1936: Tuned 4¼ litre engine fitted, giving 163 bhp, which had been endurance tested at full throttle for 24 hours.

In 1936 Hall 'had been given permission' to enter Le Mans (hence the engine endurance testing) but the race was of course cancelled that year. There is no mention of any works support for his subsequent efforts.



Thanks, excellent stuff.

152BHP on a CR of 8.35/1 from a three-and-a-half was pretty fair going for that engine; my father ran one of these and it went pretty well. Looking back I wish it had had a 152HP engine!

Paul

#36 Bjorn Kjer

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Posted 06 May 2010 - 13:40

Thanks for the infos , did answer my quest.
Now , as some of you might have guessed this thread is also a bit about transporters. The works Bentleys were driven to the tracks (before WW2) , and after with private teams ? Do you have any ideas , did they also drive them to the races or had any of them perhaps a transporter ?

A bit off topic perhaps , but I have been told that around 1945 a 6,5 litre Bentley was converted to a stationcar , and this car was used by the HRG team at the SPA 24 hoours in 1948 , can anyone confirm this. ? If, perhaps a link to a picture ?

Edited by Bjørn Kjer, 08 May 2010 - 07:44.


#37 Ralf Pickel

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Posted 06 May 2010 - 13:51

As far as I know, Eddie Hall also always drove the car to the races on its own wheels.
Even so on its last appearance in Le Mans 1950, where the team achieved a very remarkable 8th overall, then with reputedly already more than 120000 miles on the odometer of the 16 year old, much raced car ! (I have read this information somewhere some time ago, but cannot find at the moment...age...)

#38 Vitesse2

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Posted 06 May 2010 - 14:43

In Sammy Davis' "A Racing Motorist" he tells us that the cars were driven on the road. In 1925, Davis' car cracked a side member on the way, causing Segrave to drive his on to Paris to get his chassis strengthened. The Davis/Chassagne car went there by lorry. The book also implies that the Duff/Clement and Kensington-Moir/Benjafield cars were driven to Le Mans.

The cars were also driven to the circuit in 1926, Davis remarking that it was surprising that they had not received a summons for noise on the way to Newhaven. There was also a support lorry, make not mentioned, but said to be French.

Nothing specific then until 1930, although I doubt there was any change, since their arrival at Le Mans was "in every way most satisfactory to the inhabitants, who thoroughly appreciate anything that looks like a battle cruiser and makes a noise like a fifteen-inch salvo." :lol:

#39 VAR1016

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Posted 06 May 2010 - 15:57

In Sammy Davis' "A Racing Motorist" he tells us that the cars were driven on the road. In 1925, Davis' car cracked a side member on the way, causing Segrave to drive his on to Paris to get his chassis strengthened. The Davis/Chassagne car went there by lorry. The book also implies that the Duff/Clement and Kensington-Moir/Benjafield cars were driven to Le Mans.

The cars were also driven to the circuit in 1926, Davis remarking that it was surprising that they had not received a summons for noise on the way to Newhaven. There was also a support lorry, make not mentioned, but said to be French.

Nothing specific then until 1930, although I doubt there was any change, since their arrival at Le Mans was "in every way most satisfactory to the inhabitants, who thoroughly appreciate anything that looks like a battle cruiser and makes a noise like a fifteen-inch salvo." :lol:



That's right: my memory is awful - I have a copy of Davis's book from I think 1932, kindly given to me by a friend (it was his late father's). In its way a wonderful "period" read - as indeed is Tim Birkin's "Full Throttle" And that comment about the "fifteen-inch salvo" reminds me of the Brockbank cartoon featuring what looks like a four-and-a-half driving past a sign which reads "Beware sudden aircraft noises"

And I am sure that everyone here knows that the works Jaguars were driven to Le Mans in the 1950s.

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#40 David Birchall

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Posted 06 May 2010 - 18:41

Thanks, excellent stuff.

152BHP on a CR of 8.35/1 from a three-and-a-half was pretty fair going for that engine; my father ran one of these and it went pretty well. Looking back I wish it had had a 152HP engine!

Paul


That sort of power output would make a standard Derby Bentley very interesting to drive!
I acquired an Eaton blower on ebay to fit to my 1935 3 1/2 but so far my friends have talked me out of fitting it...

These blowers -from Ford Thunderbirds- are available for $150 on ebay complete with intercooler-great value.

#41 VAR1016

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Posted 06 May 2010 - 19:29

That sort of power output would make a standard Derby Bentley very interesting to drive!
I acquired an Eaton blower on ebay to fit to my 1935 3 1/2 but so far my friends have talked me out of fitting it...

These blowers -from Ford Thunderbirds- are available for $150 on ebay complete with intercooler-great value.


Yes, as I said my father's car went very nicely and it was far from its first youth; a 152HP version would have been very snappy I should think - at least so long as one could get it into second gear!

Since the rev-limit on the Derby Bentleys must be scrupulously observed, a blower is probably a nice idea. From what I remember (it was a long time ago) I should think that one would have to keep an eye on the temperature gauge - and make sure that those thermostatically-operated radiator shutters are working properly!

#42 Bauble

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Posted 06 May 2010 - 20:16

Many, many, many years ago I had a similar book to Speed Six, set in the 1920's (?) a young lad takes on Black Bart at Le Mans and sundry other circuits. He is, of course inexperienced, but leaps into a works car of some sort and is an instant success, at one stage when a car crashes on some narrow track and blocks the road, following drivers simply tip it over the edge of the cliff!!!

Anyone remember this epic tome?

Maybe he was driving a Wilson???????

Bauble

#43 Terry Walker

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Posted 07 May 2010 - 01:53

Yes, you have to watch the rev limit very carefully in a Derby Bentley. The crankshaft is long, and in it's lengthy (1922-1958) career that 6-cylinder engine revved just below the critical revs all in-line sixes are afflicted with. R-R used a number of ploys to move the critical rev band upwards over the years. One of the R-R engineers wrote a long paper on the subject, which included the daunting piece of mathematical formula used to calculate the critical frequency and hence the revs which must not be exceeded or the crankshaft vibrates itself to pieces. Many modern Derby owners have an electrically operated overdrive installed to keep revs down on the open road.

#44 VAR1016

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Posted 07 May 2010 - 06:51

Yes, you have to watch the rev limit very carefully in a Derby Bentley. The crankshaft is long, and in it's lengthy (1922-1958) career that 6-cylinder engine revved just below the critical revs all in-line sixes are afflicted with. R-R used a number of ploys to move the critical rev band upwards over the years. One of the R-R engineers wrote a long paper on the subject, which included the daunting piece of mathematical formula used to calculate the critical frequency and hence the revs which must not be exceeded or the crankshaft vibrates itself to pieces. Many modern Derby owners have an electrically operated overdrive installed to keep revs down on the open road.


Perhaps a modern damper would help? I remember reading that Prince Bira was an early customer and had to have one or two new crankshafts! The engine, I recall, used to rev quite freely - I think that the flywheel was relatively light for a car of the period; certainly the flywheel in my 1934 Alvis was like that of a bus in comparison!

Surely the post-war straight-sixes were quite different, being based on the R-R series of "B" military engines?

Finally I suppose that there must be a solution as there have been numerous reliable straight sixes, some, e.g. XK, being long stroke. Perhaps Talbot's Georges Roesch with his seven very narrow bearings and short engine had the answer!


#45 Terry Walker

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Posted 07 May 2010 - 10:01

Yes, the postwar engine was a new design, but it kept the old bore spacing and stroke, and was eventually enlarged to 4.9 litres by relentless boring-out. The original 1920s engine was 3.1 litres, and the first of the Derby Bentleys was 3.5, hence the car's model designation. All capacity increases - 3.5, 4.25, 4.5, 4.9 litres were achieved by increasing the bore, so that the final version had siamesed cylinders, and had to go to F-head to allow large enough inlet valves.

A crankshaft damper was one of the many methods RR used to prolong the engine's life. You'll find that Jaguar's crankshaft was a lot shorter, had a shorter stroke, and could therefore rev higher in safety. If you can find the original article or paper, I think it was "The Magic of a number" by Harry Grylls, or perhaps "the Story of a Number"; it's an interesting read, but way over my head technically. The "number" was the original bore spacing of the 1922 original engine, which remained the same through numerous iterations and re-designs right to the end.



#46 VAR1016

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Posted 07 May 2010 - 10:49

Yes, the postwar engine was a new design, but it kept the old bore spacing and stroke, and was eventually enlarged to 4.9 litres by relentless boring-out. The original 1920s engine was 3.1 litres, and the first of the Derby Bentleys was 3.5, hence the car's model designation. All capacity increases - 3.5, 4.25, 4.5, 4.9 litres were achieved by increasing the bore, so that the final version had siamesed cylinders, and had to go to F-head to allow large enough inlet valves.

A crankshaft damper was one of the many methods RR used to prolong the engine's life. You'll find that Jaguar's crankshaft was a lot shorter, had a shorter stroke, and could therefore rev higher in safety. If you can find the original article or paper, I think it was "The Magic of a number" by Harry Grylls, or perhaps "the Story of a Number"; it's an interesting read, but way over my head technically. The "number" was the original bore spacing of the 1922 original engine, which remained the same through numerous iterations and re-designs right to the end.


Thanks Terry, most interesting, I had never realised that it was basically the same block all the way through - a bit like the Austin Ten engine that lasted until about 1996!

As for the stroke, well it was 114mm whilst the Jaguar's was 106mm. Mind you some of Jaguar's rev limits were quite low - 5000 I think on the 4.2s, but I don't think that the Jag cranks broke if one exceeded the limit - well a bit at least. I have heard of racing 3.8s running up to 6500, but I suppose they have EN40B crankshafts. The piston speed must have been eye-watering!

Meanwhile, looking up Grylls, I found this lovely piece which is a great read.

Paul

#47 Terry Walker

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Posted 07 May 2010 - 11:31

Length of crankshaft - the Bentley had a remarkably long engine for what was a modest size six originally - is a big factor. What the formula does, apparently. is predict the "natural" resonance frequency of the particular crank and convert it to RPM. This was, apparenty, why Henry Ford wouldn't have anything to do with 6-cylinder engines after the failure of his luxury 6-cylinder Model K - it broke cranks. I doubt he knew the science but he understood the rule - long crankshaft six cylinder engines explode without warning when they rev. Ford didn't have another six until WW2, when they brought in a very good flathead inline six which was almost as powerful as the V8 but had less torque.

These manufacturers are interesting - Henry Ford owned a Derby Bentley, while at one stage Henry Royce used a Bugatti as an everyday car.

#48 VAR1016

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Posted 07 May 2010 - 11:44

Length of crankshaft - the Bentley had a remarkably long engine for what was a modest size six originally - is a big factor. What the formula does, apparently. is predict the "natural" resonance frequency of the particular crank and convert it to RPM. This was, apparenty, why Henry Ford wouldn't have anything to do with 6-cylinder engines after the failure of his luxury 6-cylinder Model K - it broke cranks. I doubt he knew the science but he understood the rule - long crankshaft six cylinder engines explode without warning when they rev. Ford didn't have another six until WW2, when they brought in a very good flathead inline six which was almost as powerful as the V8 but had less torque.

These manufacturers are interesting - Henry Ford owned a Derby Bentley, while at one stage Henry Royce used a Bugatti as an everyday car.



More excellent information, thanks again. Yes I recall reading that the Model K was an expensive disaster, and as I remarked certainly Georges Roesch understood; the six-cylinder Talbot engines look very compact - especially for the time.

Another thought, the Alvis six-cylinder engines were a fair length; do you know if they suffered from crankshaft problems like the Bentley? I always liked in principle at least the Alvis habit of placing the timing gear next to flywheel, which on a long "six" probably helped!

Interesting about Royce having a Bugatti; I have read that late in life, he wanted to design a straight-eight sports car. That would have been a torsional challenge unless his Bugatti experiences had helped!

Edited by VAR1016, 07 May 2010 - 11:55.


#49 Terry Walker

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Posted 07 May 2010 - 13:30

The Alvis engine is quite a bit shorter than the Bentley. I doubt you could stretch it to 4.9 litres by boring it out!

The only thing I know about the Alvis engine is that there is an Alvis special of prewar vintage racing in Historics here, using the biggest SUs I've ever seen, and it doesn't seem to break cranks.

I don't have my reference within easy reach, but I recall the prewar R-R-Bentley engine having a cast aluminium crankcase, two blocks of 3 cylinders in cast iron for the cylinders/water jackets, and a one piece aluminium pushrod ohv head. It's a loooong engine, much like the contemporary Phantom 1 - Phantom 2 engine. It was originally meant to be torquey and smooth and genteel, rather than sporty. The final postwar version was a cast-iron monobloc with alloy head, based on the late 1930s military engine available as a modular 4, a 6 or a straight 8. Lots of Dennis fire engines used the straight-8. So did the royal Phantom 4s.

#50 VAR1016

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Posted 07 May 2010 - 15:06

The Alvis engine is quite a bit shorter than the Bentley. I doubt you could stretch it to 4.9 litres by boring it out!

The only thing I know about the Alvis engine is that there is an Alvis special of prewar vintage racing in Historics here, using the biggest SUs I've ever seen, and it doesn't seem to break cranks.

I don't have my reference within easy reach, but I recall the prewar R-R-Bentley engine having a cast aluminium crankcase, two blocks of 3 cylinders in cast iron for the cylinders/water jackets, and a one piece aluminium pushrod ohv head. It's a loooong engine, much like the contemporary Phantom 1 - Phantom 2 engine. It was originally meant to be torquey and smooth and genteel, rather than sporty. The final postwar version was a cast-iron monobloc with alloy head, based on the late 1930s military engine available as a modular 4, a 6 or a straight 8. Lots of Dennis fire engines used the straight-8. So did the royal Phantom 4s.


Well of course Alvis made the 4.3, perhaps that might have "stretched" to 4.9? Bore and stroke were 92 x 110, making it pricey to tax at the time 32 RAC HP). there was a seven main bearing crank and Alvis claimed 137HP - at only 3600 rpm!. Certainly the Alvis engine doesn't look too long, but the absence of the timing gear at the front might be deceiving.

The block on the Bentley was I am certain, one piece - at least it certainly looked like it! And of course the best thing Bentley did was to introduce overdrive. Had Alvis added overdrive to its excellent gearbox, the 4.3 would have been even more impressive I think.

Edited by VAR1016, 07 May 2010 - 15:08.