Captain J. S. Moon, now with the Middle East Forces, has let loose his slide-rule on Mr. Pomeroy’s articles. For the sake of accuracy and as a matter of interest, we publish his remarks and Mr. Pomeroy’s reply. – Ed.
I have read with very great interest the first and third parts of Mr. Pomeroy ‘s series of three articles on Racing Car Evolution – unfortunately one issue of Motor Sport has apparently been sunk, but I hope that an eagerly awaited replacement is now on its way.
While studying the two tables of Engines Statistics, I happened to spot one or two apparent discrepancies, and was led to work through Mr. Pomeroy’s figures. While I found in general fair agreement, there are one or two points on which I should like Mr. Pomeroy’s comments.
Dealing first of all with the table on page 202 of October, 1942, concerning the 1921 engines, the b.h.p. per litre figures quoted appear a little low due to the unusual capacity in litres being used as a divisor. (Incidentally, from the bore and stroke quoted the Monroe has a capacity of over 3 litres – 3,046 c.c. – and should have been disqualified, presumably.)
I calculated b.m.e.p. by nitiltiplying h.p. per litre per 1,000(X) r.p.m. by 12.97 (which is a deduction from the standard formula) for 4-stroke engines, and this gives figures within a few per cent. of Mr. Pomeroy’s, except for the 1921 Ballot, which develops 10.9 h.p. per litre per 1,000 r.p.m., giving the excellent b.m.e.p. of 142 lb./sq. in.
The piston speeds for the Ballot and the Fiat respectively should be 2,420 ft./min. and 3,380 ft./min. for the engine speeds at maximum power.
The two remaining errors are probably attributable to the printer – the stroke/bore ratio of the Peugeot should be 1.84 and the h.p. per sq. in. inlet valve area of the Fiat should be 9.8.
Coming on to the statistics of the 1 1/2-litre engines, I reproduce below the table with the figures as I have calculated them, with those that differ widely from Mr. Pomeroy’s printed in bold type, and with, in some cases, my comments underneath.
NOTES. – (a) It appears that the printer is at fault here.
(b) Both in the table and in the text 57.5 x 75 min. dimensions are given.
(c) Only a slight discrepancy, but in view of the great interest attached to his engine it should be given due credit.
(d) Discrepancy may be due to maximum speeds not being speed at peak h.p.
(e) This, I believe, is an error repeated from the “Milestones of speed” article in The Motor, dealing with the Bugatti engine, in which the areas quoted for the inlet and exhaust valves do not agree with the diameters which are given as 0.9 in. and 1.4 in. respectively. Sealing from The Motor sectional drawing indicates that the diameters are correctly quoted and that the areas should be 1.27 and 1.54 sq. in. per cylinder.
Having now finished with my criticism of Mr. Pomeroy’s articles, may I add one or two further comments and questions.
Firstly, can Mr. Pomeroy definitely confirm that what he quotes as inlet valve areas are the cross-sectional areas of the valve throats? It appears that this is so from the drawings, but as scaling is inaccurate, I should like this point confirmed.
It is rather interesting to note that the 3-litre Ballot and the 1 1/2-litre Aston-Martin with nearly identical Henri-designed heads give much the same h.p. per litre, but at very different speeds, and with widely differing b.m.e.p.s at peak speeds. It would be interesting to know if the Aston-Martin’s b.m.e.p. approached that of the Ballot at lower speeds.
It appears from the cross-sectional drawing of the 1 1/2-litre Delage that in its original version the radiator was mounted behind the front axle and not in front. Perhaps Mr. Pomeroy has some definite information on this point.
Finally. what a car we should have had in 1927 if M. Lory had combined his own genius with the ability to produce a car with the super roadholding of Bugatti. It would not have met its master until 1939, I think.
To these comments Mr. Laurence Pomeroy replies:
To get out a considerable number of figures for articles of this nature is a difficult task which is by no means improved by not having a mathematician handy to check over the figures, and not having printer’s proofs for correction before the article appears. The latter item accounts for the discrepancy in the Ballot figures, where the maximum r.p.m. should be 3,800 in both text and table, which results in tbe piston speed and m.e.p. qtioted. A further example of a printing error is the bore of the Talbot-Darracq (as surmise), but repeated calculations on the slide rule give me 3,200 ft. per minute, not 3,300 as the maximum piston speed of the Aston-Martin, and on the Fiat 39.2 for the piston area, and 4.42 for the b.h.p. per sq. in.
Turning now to the Delage, I regret the error made in the bore and stroke, and this, of course, affects the other figures.
As Capt. Moon surmises, the differences for the Bugatti are a legacy from “Milestones of Speed,” to which he has already drawn my attention.
Answering Capt. Moon’s queries, the valve areas are quoted on the basis of the valve head, but I am afraid I cannot answer the point regarding the relative r.p.m. of the Ballot and Aston-Martin at low engine speeds, as I have no power curve for the latter.
As far as the Delage is concerned, the radiator was, as Capt. Moon surmises, mounted behind the front axle in 1926, as in this version the blowers were at the side of the engine.
A ‘correspondent has sent in a letter for publication in which he suggests that, as a gesture of appreciation of MoTon SPORT, each reader should send in a photograph of his or her present car, thus enabling an album of readers’ ears of the war years to be compiled. Our first reaction to this suggestion was to ignore it, ‘lest it smacked too strongly of an ” Editor’s benefit.” However, our correspondent goes on to remark that as such an album would be unique it might be commenced now, added to from time to time, and loaned to the secretaries of those clubs which still hold meetings, for handing round at war-time gatherings. As this aspect would confer pleasure on others besides the Editor, he has decided to make known this idea and, should it develop, to compile the proposed album-he would certainly regard it as a most pleasant souvenir of the war years. Presumably, photographs would be either of readers’ present wartime cars, or of sports cars now in storage or process of rebuilding, and if the owner features in the picture, or signs it, so much the better.
It is not difficult to visualise the kind of thing our correspondent has in mind, and if a reader owns a number of ears, as so many do, no doubt the favourite one, or a group embracing them all, would be most suitable. It would not seem necessary to send anything larger than postcards or half-plates. 1Ve shall be quite unable to acknowledge receipt of any photographs sent, but it should be possible to include lists of contributors in these columns from time to time, to let club members know how large an album to anticipate. And after time war it might be possible to make the album generally accessible, to remind our grandchildren that even a major war does not subdue enthusiasm for the Sport.
If anyone wishes to send photographs, kindly address to, W. B., 129, Fleet Road, Cove, Farnborough, Hampshire, and please accept assurance of the Editor’s appreciation in advance.