Home » Issues » April 1946 » Observations on the Gregoire
Observations on the Gregoire
It was apt that when we journeyed to Grantham to test the Gregoire prototype we used a Fiat 500. The Fiat was a 1937 Cabriolet and had the C.R. raised to 7 1/2, thereby improving engine efficiency, apparent in superior performance. and m.p.g. figures. It was a good example of this successful model and revved briskly, giving, on all but the straight stretches, a feeling of possessing ample power for reasonably snappy travel. The hydraulic brakes were of the usual high standard of this system and roadholding and cornering of a high order. For the 112 miles we computed the petrol consumption as nearly 55 m.p.g. We achieved Grantham with little fatigue and looked forward to our testing on the following day. The Fiat had gone so well and impressed us so much that we were due to be severe judges of the Gregoire.
The premises of the Grantham Productions Co., Ltd., are modern, well built and spacious. One gains admission via a guard room and is carefully scrutinised by factory police. We asked Mr. Bleeney (Publicity Manager) if he would tell us more about the company's views on producing a sports car. He replied that they definitely intend to produce a sports model. The Gregoire chassis, he stated, does not depend for its rigidity on body-work. A light open two-seater body could be fitted and this would possibly give a weight saving of 40 lbs. He thought it possible that the company might sponsor a team of trials cars. Anyhow, Mr. Kendall is "Sport-minded," bemoaning, as he did recently, the loss of Brooklands. Then came our opportunity to test the Gregoire. This car is now so well known that a detailed specification would be tedious to readers. The all-independently sprung chassis follows Austin Seven layout, having two transverse springs for the front wheels. The rear wheels being controlled by single light alloy trailing links, each one tensioning a coil spring. The aluminium alloy castings (Alpax) used extensively are "the aluminium caster's dream of delight."
The suspensional problems of an ultra light vehicle are extremely delicate. With a weight of 10 3/4 cwt. and one up,approximately 4 1/2 cwt. will be carried on the rear wheels, but this figure may rise to 7 1/2 cwt. with three passengers on board. To produce a system of suspension capable of dealing with such a large load fluctuation and giving the required rate at either extreme was solved by the use of a coil spring in tension placed below and at a small angle off the longitudinal line of the trailing link. This angle off increases with loading and gives the desired spring rate.
The 4-seater bodywork had a cabriolet top. There were two entrances, the doors having a wooden frame covered with light alloy which was padded for sound damping. The windows, as on the Fiat, slid horizontally. The interior of the Gregoire is reminiscent of a light aircraft. The front seats had tubular frames and were of the simplest possible construction; none the less, they were comfortable. There is ample space in the back seats to accommodate our 6 ft. 2 in. The only parcel space provided was a small shelf behind the rear seat squab, available when the top is erected. A demonstrator drove for the first mile, explaining the controls. We then took over, getting away smoothly with the unaccustomed clutch. However, at first we did not have the same brilliant success with the gear box. From bottom to second gear one tends to grate on the reverse cog. Furthermore, the ratio spacing between first and second gear seemed too great and the difference between second and third ratios too small. The gearbox ratios were: First 0.325, second 0.64, third 1, overdrive top fourth 1.28.
With a 7 x 40 back axle and using 400 x 15 tyres 12.2 m.p.h. represents 1,000 revs, in third gear. The tickover was surprising, it being hard to discern if or not the engine was running.
In revving for "get away" a period is passed (some 600 revs.) which causes unpleasant vibration. This, however, is momentary and it is not experienced at any other rate of turn, though the engine does get somewhat rowdy if revved over 3,000 in bottom gear. Compared with the Fiat the engine pulls with a feeling of woolliness, unlike the brisk, free sensation obtained when a few revs. are indulged in with the Fiat.
In the Gregoire one has the impression of going slower than one really is. The Fiat gives the impression of being snappier than the Gregoire but is in actual fact considerably slower on acceleration, 10-30 m.p.h. requiring 21 secs. with the Fiat but could he achieved in the Gregoire in 15 sees. This, of course, is due to the fact that the Gregoire is a full cwt. the lighter of the two cars and develops two more b.h.p.
Best roadholding and cornering were found in the Gregoire. Its ability, to get round corners in front-wheel drive style with one's foot hard on the accelerator was incredible. The ride was comfortable but not sloppy, if anything a little on the taut side. In spite of encountering some bad road surfaces there was at no time any evidence of loss of tyre adhesion to the road. The hydraulic front/ mechanical rear braking system was both smooth and powerful.
Here we thought was the ideal basis for a perfect sports car for the impecunious enthusiast. It is stated that the power of the flat-twin engine is limited by the diameter of the inlet manifolding to 15 b.h.p. at 4,000 revs. Assuming that the crank and reciprocating parts have a customary high safety factor, it is reasonable to suppose that, with a 7 lb. boost, 25 b.h.p. would be forthcoming with reliability. Such a modified engine, in conjunction with 2-seater body-work having a total weight of, say, 10 cwt. with driver, should give a fairly creditable performance, being capable of 0-50 m.p.h. in 18 seconds with a top speed approaching 70 m.p.h.
Unless superchargers are soon to be manufactured at a price considerably less than their pre-war figure, it is unlikely this car will be marketed so equipped. It would be incongruous for a supercharger to cost more than half that of the rest of the engine.
A more practical suggestion would be to "hot-up" the standard unit, using two carburetters and the usual aids for increased power. In this fashion 20 b.h.p. should be obtainable without much difficulty at, say, 5,000 revs.
It is thought that the construction of the Gregoire should lend itself to the partial use of plastics. Some of the cast members could probably be formed in a laminated plastic (having a relative density of 1.3 against 2.67 of aluminium).
In considering this remarkable little motor car one is apt to forget, by virtue of its many finenesses, the fact that it is to be marketed at a price nearing £120 less than the standard Ford Eight.
Whereas we have great faith in the reliability and longevity of the air-cooled flat twin, we feel that eventually the Americanised populace of the island race will demand the added smoothness of, at least, one extra cylinder. — D.P.
[I find the argument for three cylinders against flat-twin unconvincing. Does D.P. mean a radial or an in-line 3-cylinder and has he his balance data ready to offset the technical readers? — Ed.]
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