A Simple Method of Converting the Braking System on Frazer- Nash Cars from Cable to Hydraulic Operation

A Simple Method of Converting the Braking System on Fraer-Nash Cars from Cable to Hydraulic Operation

DURING the past two years I have effected a conversion of the braking system on my ” Nurburg ” FrazerNash from cable to hydraulic operation which promises to be very satisfactory. The conversion, after a good deal of consideration, trial and error, has proved so simple that I put it forward as a solution to some of the braking problems which exist with the earlier Frazer-Nash models. On my own car, circa 1932, these problems came under three headings :—

(1) The brakes, which were 12-in, diameter in front and 10-in, diameter at the rear, at their best had only been adequate and had never inspired confidence. Bands shrunk over the outside diameter of the drums to prevent distortion had produced a slight improvement, but I remained far from happy behind large American cars, and could never be sure, particularly in the wet, that a sudden application of brakes would produce deceleration in a straight line.

(2) The entire braking system required overhauling.

(8) I intended supercharging the engine, which automatically threw the defects outlined in paragraph (1) into greater prominence.

The system I favoured was the Lockheed, which operates on the principle that “pressure exerted upon any portion of a fluid enclosed in a vessel is transmitted undiminished equally to all surfaces.” This type, inherently selfcompensating, primarily solves the difficulties of ensuring straight-line braking ; it has the minimum of parts to wear, is light, powerful, easy to maintain, and has the added advantage that the whole ‘Nash brake pedal and cross-shaft assembly can be dispensed with and the master cylinder operated by a second pedal mounted on the clutch cross-shaft. From a blitzed Triumph ” Gloria ” I obtained, for 50s., the entire brake layout, comprising front-brake assemblies with stub axles, splined hubs and Timken taper roller bearings, and the rear-brake assemblies. All drums are 12-in, in diameter. Front Assembly.—The Triumph front stub axles, in common with the ‘Nash’s, are covered by Rubery patents and the king-pins and bushes are luckily interchangeable. The taper keyed locations for the track rod arms are identical, but the location for the steering arm is, unfortunately, machined the opposite way round, and this means either fitting the steering arm with the ball end hanging downwards—not a pleasant sight to contemplate—or twisting the straight shank of the arm through 1800, thereby bringing the ball end to the top. The second alternative was chosen, and the arm was twisted hot and afterwards magna-fluxed and normalised to relieve stresses. Thus the entire Triumph front assemblies–stub axles, brakes and hubs-

P. McCormick describes here a very practical modification to his blown ” Nurburg ” Frazer-Nash.

were fitted, and attention turned to the rear.

Rear Assembly (Bach plates).—The sheet metal backplate rivetted to each of the ‘Nash radius arms was removed and the centres of the Triumph backplates were turned out—about f-in. on diameter being removed—to locate on the spigot formed by the outside diameter of the protruding bearing housing on the outer face of each radius arm. Each backplate was then secured by four conveniently placed bolts, positioned as follows : two were the h-in. bolts which act as stabilisers and pass through the top and bottom of the radius arms, the third was a *-in. bolt replacing the ‘Nash brake shoe-cum-shock-absorber fulcrum pin, and the fourth a Fin. bolt replacing the ‘Nash brake-operating camshaft. At this stage it is worth stressing three points :— (1) Packing pieces may be necessary on the four securing bolts to line up the backplates and prevent fouling by the drums. In the case of this conversion these were made by hand, to suit, each

of the eight pieces being shaped differently. The maximum width of any one was h-in.

(2) It is essential to fit the backplates with the wheel cylinders uppermost to permit of bleeding the lines through the valves in the top of the cylinders.

(3) It is necessary, with the singlebrake-shoe, fulcrum-type radius arms, to tilt the backplates (taking the centreline as a vertical line passing through the centres of the plates and the wheel cylinders) backwards through an angle of about 70 in order to provide clearance over the side of the radius arms for the brake-shoe cam adjustment nuts. This clearance can be obtained and a sufficient space left under the side of the radius arms through which to pass the cables which provide the auxiliary hand operation of the rear brakes.

Rear Assembly (Brake Drums).—The one real snag of the layout is the method of fitting the rear drums. The original rear drums of this car were the old saucer-type with short-reach hubs, and thus it meant packing the flat-faced Triumph drums inwards to meet the backplates. In order to do this, spacers had to be devised which would also act as adaptors between the eight h -in. bolt holes in the flange of the ‘Nash hubs and the Fin, diameter holes in the Triumph drums. These were duly designed and machined from the solid (M.S.), providing the most expensive item in the whole layout (23). The drums were secured to the adaptors not by Fin, bolts, but by fin, bolts passing through short fin. diameter sleeves. A refinement of this design might have been the fitment of studs in the flanges of the adaptors in place of the bolts described, but in that case the flanges would have to be wider and the saving in weight is problematical. Anyway, the result achieved is most satisfactory in spite of having to remove the hubs in order to inspect the internal brake mechanism ; this should be a rare necessity. Fitment of Master cylinder. —Fitting the master cylinder presented no difficulty. A right-angle bracket was fabricated from k-in. M.S. plate, to carry the master cylinder, and the whole assembly was bolted snugly into the channel section of the side-member at a convenient distance from the brake pedal. This pedal, a second ‘Nash (‘hitch pedal, mounted on the same cross-shaft, provides the thrust to the master piston through the normal adjustalac-type, ballended connecting rod. The reservoir is placed above the master cylinder on the bulkhead. The pipe layout is a matter of taste, and it is not proposed to lay down any hard-and-fast scheme other than to emphasise the necessity of fitting four flexible pipes—one from each wheel cylinder, it was found desirable in this Continued on page 85

CONVERTING JIIE BRAKING SYSTEM—continued from page 70

particular case to fit a fifth flexible pipe from the master cylinder to the main transverse gallery pipe which feeds all four wheel cylinders separately. After all, ‘Nash chassis do flex a little! Any Morris, Wolseley or Triumph handbook devotes a chapter to the care and maintenance of Lockheed brakes, so any notes on this subject would be redundant. For a total expenditure of about £6 the whole conversion may easily be effected, and this sum, viewed as 80s. per wheel, compares very favourably with the alter native cost of relining shoes and probably fitting liners to the old drums. The only essential concomitant of the conversion other than. those already mentioned is a wife who will sit for hours on end patiently operating the brake pedal, while you, with the aid of box spanners, sticky fingers, and horrible language, lie on your back underneath and bleed the wheel cylinders one by one !