The Automotive Inventions of Ettore Bugatti

Extracts from a Paper read before the Newcomen Society by H. G. Conway, M.A., M.I.Mech.E.

(Continued from the May issue)

160439/1921. This is related to 1358/14 and claims the resilient mounting of the outer bearing.

195392/1923 (Nothing filed in 1922 in Britain and only seven cases in France! Perhaps Bugatti was busy with the racing cars). This specification describes the slotting of a ball or roller bearing outer ring to allow oil to be pumped in to oil the bearing. It is difficult to believe that this was novel but the idea was used on the roller bearing crankshaft of the racing engines.

197922/1923. The preoccupation with crankshafts and lubrication continues. As the diagram (Fig. 18) shows the idea was a means of feeding oil into a crank through large-diameter close-fitting rings (which do not however touch), and then out to the big-ends. The loss of oil at these diameters would have been enormous, especially as the clearance would be large to deal with crank deflection; one would have supposed that the jet scheme used on earlier cars would have been preferred; in this, the oil is squirted from jets in the crankcase sideways into grooves in the circular crank webs and thence outwards to the big-end bearings.

197928/1923. This describes (as illustrated in Fig. 19) a detachable cambox with means of getting a reasonable water circulation, although it is not clear from the specification exactly why the water should follow the direction of flow shown by the arrows in the lower diagram. This is basically the construction used on the 1924-30 Grand Prix racing engines and other single-cam types, a practical and convenient arrangement allowing speedy removal of the whole top assembly.

201160/1923. This shows a worm and worm wheel steering box with the worm wheel mounted on an eccentric shaft. By turning the shaft round with its flange, the meshing of the worm wheel can be adjusted. This seems an excellent construction.

205088/1923. Bugatti was prepared to design carburetters. This specification describes a carburetter with a circular barrel throttle valve, rotating around the choke and throttling the inlet to and outlet from the choke at the same time. The whole valve and carburetter body is water-cooled. Most of Bugatti's engines at that time and subsequently had water-cooled inlet manifolds in order to warm the incoming gas. His exhaust pipe was always on the opposite side from the inlet pipe and he was not able to use what is now common -- an exhaust heated hot-spot on the inlet manifold. This undoubtedly would be more effective than water cooling the carburetter or inlet manifold.

205488/1923. This describes a front axle construction where the axle proper is a hollow casing surrounding the chassis front cross-member and connected to it by a series of coil springs. The axle is co-axial with a chassis frame. The interest of this specification lies in Bugatti's description of the defects with conventional springs. He describes the geometric errors which are caused by the ordinary type of spring shackle, where the driver must be continually moving the steering wheel to correct for spring deflection in order to follow a straight line. Bugatti cars were famous for their excellent roadholding and steering, and it is not surprising that there are no signs of Bugatti having actually used the invention. No doubt he found it better to persevere with conventional laminated springs in spite of their geometric defects.

211877/1924. This shows a transverse leaf spring arrangement for the rear axle of a car, the spring being split and diamond shape to give it a base where it is attached to the chassis to help it deal with fore and aft loads.

212221/1924. This is an improvement to 205488 replacing the coil springs with a transverse spring. It is curious how Bugatti has been preoccupied over the years with transverse springs but there is no sign of him ever having actually used one on a car.

220284/1924. This specification illustrates the water cooling of the main bearings of an engine by extending the cylinder jackets down to the main bearings. This construction was used on the largest Bugatti engine which was produced in small numbers for cars (the Royale) and later adopted extensively for rail-cars in France.

218236/1924. This is an improvement to 205088 and shows the use of a shaped cam over the top of the carburetter jet to vary the area and thus the flow of petrol.

222475/1924. This shows the cage of a roller bearing with the outer edges of the cage itself running on small balls or rollers -- that is, a roller mounted roller cage. This patent is void and no doubt has been anticipated. It appears to be an unnecessary refinement for a cage.

222476/1924. This illustrates the principle of mounting the gearbox and clutch of a car under the passenger seat so that the pedals can be carried nearer the engine and the front seat moved further forward. While the novelty in this seems questionable, the construction was used for at least one Bugatti car design. Most people would not like sitting on top of a flywheel.

222477/1924. This illustrates the principle of engines designed slab-like and able to be mounted close together in multiple units with geared crankshafts. Again there seems to he little novelty in the idea.

222478/1924. This patent is of interest although void. It illustrates what was probably not novel -- namely a double tyre with an inner high-pressure cover whose sole purpose was to keep the outer low-pressure cover in position. The tyres shown were the beaded-edge type which were common at that time and the date of the invention (September 28th, 1923) is of interest because it was known that Bugatti was in serious tyre trouble with his racing cars at that time.

223212/1924. This patent is an addition to 222478 and is also void. It discloses more ideas for using one tyre to keep another in place.

223213/1924. This describes the hollow engine valve with a tulip-shaped end, the head plug being brazed in position. The patent was not accepted no doubt due to lack of novelty.

223545/1924. An oil-cooled valve. The valve has a hollow stem and there is a fixed tube with small piston head pinned in position from the valve guide. As the valve moves up and down, oil is pumped in and out of the head. It is difficult to see how a pin of adequate size could be fitted in the slot through the valve stem; the construction does not appear at all practicable.

232228/1925. Bugatti was using at this time a built-up roller bearing crankshaft on his racing cars. He had always seemed to avoid the use of pressure-fed bearings and had relied on jets or drip feed. It is not impossible that he went over to roller bearings to get over the deficiencies of his lubrication system, although it would be cheaper to use conventional pressure feed than roller bearings. However, bearing materials at that time were not as good as they are today and the technique of bearing design was not so advanced. The invention illustrates one means of holding the built-up crankshaft together by means of clamp bolts on the split webs of the crank. There is no sign of this invention having been used in place of the common construction covered by Patent 235541 (below).

233324/1925. A cast wheel with vane-like wide blade spokes is described, to promote cooling flow over the brake drum. The wheels are handed. Cast aluminium alloy wheels were a Bugatti feature but not with vanes.

233673/1925. This shows a further means of damping on a beaded-edge tyre to a wheel but the patent is void and probably was not novel. The patent illustrates various means of removing one flange of a rim and retaining it with a circlip or a screwed ring but none is particularly ingenious.

234783/1925. A patent of addition to the previous one and also void.

235168/1925. This illustrates what since 1924 has been one of the great novelties of the Bugatti car -- a solid one-piece forged axle with a hollow centre section. The specification illustrates (Fig. 25) how this was carried out, by boring a hole through the axle and punching square slots for the springs, and then forging the axle to shape afterwards. Since the loads on a front axle are a combination of bending and torsion the hollow tubular construction is logical. The mounting of a spring in a hole through the axle is also an elegant refinement.

235541/1925. This case describes the famous Bugatti built-up crankshaft used on his racing cars. The alignment of the crankshaft is achieved by cross cotter pins on the crank webs and the construction, in practice (using case-hardened parts throughout), is surprisingly effective and extremely rigid. It is possible to align a crankshaft to within about 0.001-in, dial gauge reading merely by selecting cotter pins of slightly different angle. The patent was never accepted -- no doubt the Patent Office decided that the principle of the invention was no more than the principle of the cotter on a bicycle crankshaft. Reference is made in the specification to the use of the central hole for alignment during assembly. This is not present in fact on the production crankshafts, it being as easy to use a surface plate and centres for alignment.

235854/1925. This shows more beaded-edge tyre clamping systems with detachable flanges: The patent is void and was obviously not accepted.

236585. This was a patent of addition to the previous one and is also void.

240826/1925. This illustrates (Fig. 27) an excellent little detail from Bugatti cars -- the front brake-cable swivel. Bugatti carried his cables over the top of the king-pin down to a lever mounted on the front of the brake. He used a pulley the circumference of which intersected the king-pin axis, and was carried on a swivelling lever so that the pulley could at all times bisect the angle between the incoming brake cable and the length of cable going to the lever. The mounting of the cable in this manner gives a servo action when the brake twists the axle when the brake is applied. This makes Bugatti front brakes extremely effective. The converse of this arrangement always made the brakes on an Austin Seven very ineffective since the more the axle twisted the more the brake was let off.

256615/1926. This illustrates the idea of an extended skirt round the valve stem on the normal abutment washer which carries the split cotters on an engine valve. This sleeve was used on most Bugatti car engines and prevented oil dripping through the spring and down the valve stem. The patent is void and was no doubt not accepted as novel.

270700/1927. This illustrates a split rocker which is supposed to silence valve noise on an engine. It is difficult to see how such a construction could be given an adequate fatigue life.

271435/1927. A rear spring is described with additional leaves coming into play as the spring deflects to give an increased rate. This is a common feature on many cars today.

279116/1927. This describes Bugattis brake compensating system which used a pair of cables running between front and back wheels on either side over the pulley arrangement described in the next case. The particular feature of the invention was the use of a transverse floating link between the two side cables, used to balance up the loads between the two sides. In practice, what Bugatti used was a small bevel differential on the brake pedal operating two cross shafts, to either side of the car, which then operated the brake cables. The brake pedal itself operated the planet bevel and distributed the load equally between the two halves of the system.

283206/1928. This shows how the brake cable system on either side of the car can be taken over a pair of pulleys, carried on the brake lever, and arranged to pull both ends of the cable in opposite directions. This invention describes the use of a stop between the two pulleys so arranged that if .one end of the cable breaks the other end can still operate.

289193/1928. Bugatti refers to the fact that a conventional shock-absorber mounting on an axle could not restrain axle twist, being sensitive only to vertical movement of the whole axle. The invention proposed to mount a pair of shock-absorbers on the axle itself and so arranged that they would damp axle twist as well as vertical movement of the whole axle. It is not likely that this device would be at all effective since the torsion loads on axle from braking are very much greater than the vertical forces created by a conventional spring damper.

301065/1928. This illustrates the use of a non-return valve on a float in the header tank of the radiator system of a car. When a car is braked the water in the radiator tends to flow down the overflow pipe, and this invention uses the flotation effect of the valve to close the escape passage down the overflow.

301375/1928. This describes a further shock-absorber mounting with a lever connecting the shock-absorbers to the axle so arranged that the action of the shock-absorber is the least when the axle is in its normal position and increases progressively (to give a non-linear law) as the axle deflects.

335797/1930. This shows the carriage of a crankshaft of an engine on bearing blocks bolted to the underside of the cylinder block and located accurately off one side of the abutment face. The other side is split and clamped up by screws to make the assembly tight. This seems a simple and effective arrangement provided the bearing mounting blocks can be manufactured with a sufficient degree of accuracy. Normal practice is to line-bore the bearing holes.

342390/1931. This illustrates (Fig. 30) an ingenious and simple automatic brake-adjusting device. There are many known constructions for this but the one illustrated in the diagram is certainly ingenious and simple. Normally the brake cam can move over an arc determined by the slot in the small adjusting washer. This washer is serrated on one face and engages with corresponding serrations on the brake back plate. The serrations are spring-urged together to stop the washer rotating. Normally, therefore, the brake lever will only return by the amount determined by the elongated slot, but when brake wear takes place and the travel of the cam becomes excessive the washer will be moved round one further notch. A minor criticism of the construction as shown is that normal movement takes place between the cam and the washer and thus the springs would have to slide.

349353/1931. This shows the idea of mounting the flywheel on the end of a crankshaft by means of a series of rubber cylinders.

264074/1932. This invention, although void and merely an improvement on the previous one, has the surprising title "Improvements in systems of mounting a flywheel on the shafts of thermic engines, especially of multi-cylinder explosion engines for propelling land, sea and aerial vehicles." Instead of rubber "congealed oil" is used as an elastic or flexible connection between the hub and the outer rim of the flywheel.

386949/1933. This relates to hydraulic tappet arrangements and is void. It is probable that the invention was anticipated as many engine designers were working on hydraulic valve-lifting means about that time, including many engineers in the U.S.A.

386954/1933. This illustrates a differential piston system for vehicle brakes but was not accepted as it was undoubtedly not novel. Two-stage braking systems were well known even at that time.

394877/1933. For the first time we see Bugatti's son Jean protecting an invention -- in this case for a railway bogie.

396263/1933. This invention (again in the name of Jean) illustrates a four-wheeled drive system for a vehicle with a slipping clutch between the fore and aft axles to allow for errors between the two. This does not seem a very good method for getting over the known difficulty, usually catered for by another differential between front and rear axles.

396578/1933. A gear housing for a light aero-engine is described. The casing, of sandwich or hollow construction, is full of rubber to damp unwanted vibrations -- or so the invention says.

396584/1933 -- (Jean Bugatti). This is a rail-car detail showing the mounting of the main king-post in a rubber housing.

405205/1934. This illustrates several means of splitting an ordinary front axle on the centre line and holding together by means of flanges or a screwed sleeve so that each half of the axle can twist to a small degree without twisting the other half. Each half is located by means of a radius-arm which prevents it from twisting; the freedom to rotate as between one half and the other is thus essential. Many European engineers were working on independent front suspension about this time and although Bugatti himself never produced a car with full independent suspension in front, he did his best to improve the conventional front suspension. The split axle construction was used on the lost car he designed before the war.

409968/1934. The device is really a railway buffer; the specification describes its application to vehicle suspension.

409990/1934. The flexible mounting of a motor-car engine had been developed in the United States by Chrysler and Citroen in France. Bugatti describes a similar arrangement where the damping is provided by mounting the magneto or other accessory in the dash in a friction mounting. Chrysler had used damping at the side of the engine.

411019/1934. A wheel is described where the spokes are purely radial and dogs at the edge of the hub or brake drum engage notches in the wheel rim to take torsion. The spokes deal only with radial loads. A very elegant realisation of this wheel was used in the later G.P. racing cars. The keys on the brake drum, being radial, can expand in the slots in the rim without restraint when the brake drum gets warm.

419029/1934. A radiator-core system is described where the vehicle axle passes through the core. Above it is a separate water header tank, the whole system producing a very compact and low-mounted water-radiator system suitable for use in a racing car.

434907/1935. Another radiator system is described where jets are used in the header tank to direct the water at high velocity down through the cooling tubes to promote heat transfer. A reasonable pressure from the water pump in the header tank is obviously needed.

437911/1935. A ventilated brake drum for a vehicle is described. The outer edge of the drum is slotted and air is supposed to be sucked across the brake drum and thrown outwards through the slots by the rotation of the wheel. The brake drum is complicated and would not have withstood the thermal stresses which it should support.

446148/1936. An engine cylinder construction made up of numerous elements all clamped together and welded.

450347/1936. This describes a pump mechanism intended primarily for a fuel pump of variable stroke. This mechanism (an intermediate sleeve with one straight and one helical spline) is a favourite of Bugatti. He used it to vary magneto timing on his wartime aero-engine and on later racing cars.

451752/1936. This shows another method of holding together a built-up crankshaft with a single cotter pin instead of the two previously described.

457279/1936. Ettore's son Jean was now protecting many ideas, several related to improvements to ordinary engine valves. Here he proposed to use the common steam "double-beat" valve for a petrol engine, and got over the inherent difficulty of seating both valves at once by slitting the body of one valve. An exhaust valve of this type could surely not have been made to work.

461573/1937. An elegant valve and rocker design with anti-friction rollers on the cam follower.

472242/1937. This described a means of swaging a tube into a casing or fitting by means of an internal conical thimble. The specification suggests its use on boilers, but Bugatti for many years had used swaged tubes through his engine crankcases, to cool the oil.

473580/1937. A flexible swivel joint for piping.

478893/1937. Passing over several inventions by the son, we come to a particularly interesting one wherein he describes a high-pressure steam engine. It is possible that the family had begun to think of applications of steam on rail-cars, although the specification hints at an application on an ordinary road vehicle.

481339/1938. A method of stopping diesel knock on an engine is described, by elastically-mounting the separate cylinder heads so that they can lift slightly against rubber buffers. In practice the inertia of the cylinder block would have prevented adequate damping. The adjacent patent specification describes a camshaft drive system for an engine of this type, where each cylinder has its own separate camshaft, the whole being coupled together by central splined coupling shafts to allow for the small vertical freedom involved. An almost identical design was used by Bugatti in 1907 on one of the Deutz cars.

482315/1938. Bugatti invented large things and small things. This specification describes an expanding bolt which could be expanded over its centre diameter to make it fit snugly in the holes of two parts being clamped, the better to take shear loads.

483669/1938. A roller-chain construction is described where there are small rubber bushes between the pins and the links to give a degree of elasticity, although obviously at the expense of size.

524128/1940 (Filed 1938). A bearing shell is described wherein the surface of the shell is machined with a very coarse thread, the cavities being filled with white metal so that if this wears, contact and bearing can take place on the tops of the threaded shell.

About this time the number of patents which deal with things other than motor vehicles are becoming greater -- several relate to aeroplanes and boats.

543389/1942 (Filed in 1939). This illustrates an excellent valve-rocker construction with the rocker inserted from the outside of the cam box.

590854 (Filed in France in 1943). This refers to Bugatti now as a French citizen and gives his full name as Ettore Isodoro Arco Bugatti. A multiple valve system is described for an engine. There seems little to commend this idea as applied to a conventional petrol engine.

591521 (France, 1943). This shows an excellent centre bearing design for the main bearings of a crankshaft to allow the crankshaft assembly to pass through the crankcase.

592565/1946 (France, 1943). This shows several engines coupled by means of hydraulic couplings to a common casing which acts as a reservoir for the oil in the couplings and enabling one or more couplings to be drained to uncouple that particular engine.

595773/1947 (Filed 1943 in France). This describes a built-up version of Bugatti's classic axle, designed with the two ends of the axle made from forgings and joined together by a brazed tube. Bugatti's pre-occupation with rigid axles as late as 1943 seems strange. This case is the last recorded invention applicable to motor vehicles in the name of Ettore Bugatti. The other 13 cases in his name relate to machine tools or boats.

632723/1946 (In France). Although this case was filed about a year before the death of Ettore by Roland Bugatti, his son, it seems probable that it describes an engine that the father had been working on. It is a square engine with two pairs of two cylinders operating with two crankshafts geared together. A rotary valve distributes to and from the cylinders by means of a rotating assembly rubbing on the top of the four cylinders. The design is ingenious and typically Bugatti, although one would have supposed that the friction of the large-diameter valve would have prevented it operating reliably.

This review of Bugatti's published specifications has been made with a background of some knowledge of his car designs. Many of the inventions described appear impracticable and, indeed, some are ridiculous; but even without allowing for the crudeness of some of the specification drawings they do show considerable mechanical creative ability.

Few of the inventions could be judged as fundamentally important. The patent structure which Bugatti built up around himself seems frail and a little like a house of cards. It may have had more value for prestige than commercial protection.

Bugatti's car engines were characterised throughout the whole of his design experience up until about 1930 with two major defects. Firstly we may note his almost complete inability or stubborn reluctance to design an engine with pressure-fed hydro-dynamically lubricated bearings, and, secondly, his retention of a valve layout which, if it gave plenty of area for the incoming and outgoing gases, did not allow for adequate valve-seat cooling, and was thermodynamically inefficient.

The aero-engines of the first world war and the fine results achieved after it, during the Schneider Trophy races in the 1920s, showed that engine design had reached a high degree of perfection at the time when Bugatti was winning races by the hundreds with engines which, to the engine expert, were 20 years out of date. But for sheer artistry and interest, the Bugatti engine and car had few peers. Character, even if occasionally bad, is seen at every corner.

But few of the published inventions give the key to his engineering design quality, which was based upon simple and straightforward forms which could be machined on the centre lathe or the horizontal boring machine without involving complex angles, and yet could be multiplied into multi-cylinder engines of slab-like appearance. And coupled to this was an atmosphere in the factory, dominated by the Patron, of good workmanship, cleanliness, and "doing the job properly."

This paper has been concerned only with Bugatti's inventions; it suffers from the obvious defects of having been written in Britain without contacts in France with those who could relate published specifications to practical realisation.