MERLIN HERITAGE AND TECHNICAL DEVELOPMENT

The famous Rolls Royce Merlin was probably the most developed engine in the World. The Merlin's development began back in the 1930's with the Schneider Trophy Race winning aeroplane powered by the Rolls Royce "R" Engine, from which the Merlin was developed.

The Merlin would be in the same league as the Offenhauser (the famous lndy 500 Oval Racing engine in the U.S.A.) and the Formula 1 Cosworth DFV engines, being developmental miles stones in there own right.                              

The Merlin is still under development to this day, being used in Thunderboat racing and unlimited aeroplane racing (Reno Pylon Racing) To this end we have opened new dimensions with specialised fuel injection. 

P51 MUSTANG 1750 BHP                     

Many of the principles developed in the Merlin by Rolls Royce, formed the basics for the modern racing engines.

The Merlin evolved from delivering 790 HP in 1933 to 2,620 HP at 3,150 RPM with 36 Ibs/sq in boost and water injection in the mid 1940's(this engine ran for only 15 minutes) It  was produced in various forms for use in many aircraft including fighter Bombers and civil variants.  

The aero racing engines produce in excess of 3,500 HP- remembering that the aeroplane must stay in the air for over 20 minutes, in itself an achievement in reliability, and the main reason we are using them. 

The thunder boats produce much more than this delivering upwards of 4,000 HP. Being more modified running turbo charging and methanol for many years now, and so acquiring more horsepower and higher RPM. Unfortunately these engines were eventually overtaken by the Allison Jet Turbine, some die hard boats still run the Merlin in U.S.A. and Australia with moderate success against the turbine.

I must note that the turbine was the only engine to beat the Merlin and Allison engines in boat racing- a credit to the engines and its designers. 

DESIGN AND CONSTRUCTION OF WOOMERA 1

The wind tunnel testing was carried out in the Royal Melbourne Institute Of Technologies Wind Tunnel with a 1/6th scale model by Daniel and Greg

The vehicle DRIVELINE design evolved from a progression of ideas in solving problems associated with design parameters that were already set.

These were:-

Speed 500 mph

Wheel Diameter 30" (762mm)

Wheel Speed 5,600 rpm

Engine Horse Power 2,500 (approx) per engine

Engine Torque 2,000 Ibs (approx) per engine

  The main design parameter was the relationship between the speed of the vehicle and the maximum rpm of each engine.

To obtain a speed of 500 mph at 3,500 rpm with a wheel diameter of 30", the wheels would need to spin at 5,600 revolutions per minute. The Drive would need to be stepped by 1-1.6.

These limitations assessed with the help of Allison Transmissions both here in Australia and the U.S.A. culminated in the selection of two Allison HT 741 Automatic Transmissions both having four forward gears and one reverse. The vehicle is four wheel drive with one transmission driving the front wheels and the other driving the rear wheels. Both transmissions are linked with Allison's latest computerized transmission technology A.T.E.C. (Allison Transmission Electronic Control)

With each Rolls Royce engine and Allison transmission accurately mounted in the tub section, the basic Driveline layout showed the gear box centre-line to be above the engine centre line requiring the Drive to each gear box to be stepped by the ratio of 1 - 1.6. This task was achieved by designing a series of transfer cases. The first being the Engine Transfer Cases mounted between each

engine and gear box. In order to spin the gear box at the same speed as the engine, these Engine Transfer Cases have a 1 - 1 ratio. This was also to make sure that we were working within the 4,000 rpm range and gear box revolution limitations. Since both the engine and gear box rotate in the same direction as each other, an idler gear was placed in the Engine Transfer Case between the engine input driver gear and the driven transmission gear. These three gears being 30 Tooth and 4 DP (Diametric Pitch)

To transfer the power from the gear boxes to the Final Drive it was then necessary to design a second pair of transfer cases. The Final Drive Transfer Cases contain two gears. The first is a 42 Tooth 4 DP Driver Gear and is mounted on the output shaft of the gear box. This gear drives the second gear mounted on the pinion shaft which is 26 Tooth 4 DP giving the required step up ratio to the Final Drive of 1 - 1.6.

The design criteria meant that these transfer cases needed to be designed and custom built and it was decided to fabricate them from aluminium plate with steel bearing carriers thus making them light but strong. Their basic construction consisted of a 20mm outside shape of the transfer case. Each transfer case was then totally machined in a CNC machining centre, bolted together and line bored for precision bearing alignment. All of the tapped holes in the transfer case side plates were fitted with recoils (steel threaded inserts) to give a strong thread in the aluminium. The bearing carriers are held in with 7/16" UNC cap screws and the side plates fixed to the spacers with 3/8" UNC cap screws.

 Oil is pressure fed to each transfer case by dry sump pumps through stainless steel hoses. It is scavenged from the bottom of the Transfer Case by a scavenge pump fed back into a de-aerating tank where it is then pressure fed through an oil cooler and filtered back into the Transfer Case. 

· The Final Drive Gear Cases have been fabricated from steel plate. Housed inside are the two bevel gears, crown wheel and pinion (the pinion being the driver) which are 1 - 1 ratio. The crown wheel (on the rear axle centre-line) and carrier are supported by two Timken tapered roller bearings. These bearings can be adjusted for pre-load and are also pressure fed with oil from the Transfer Case Dry Sump System. The steel bearing carrier is housed between aluminium end plates that have been cast, heat treated and CNC machined.

· Both engines have a unique inlet manifold system. Custom designed and handcrafted from 3mm aluminium sheet the Rolls Royce Merlin inlet manifold features for the first time direct port fuel injection. Each manifold has no less than forty-eight (48) individual injectors, two for each valve, two valves per cylinder.

In Summary, this is the first time a Driveline such as the one outlined has ever been designed and assembled for an attempt on a World Land Speed Record. The driveline function and purpose make it unique in Automotive Engineering terms, the development of which has taken four years and many thousands of man hours.

DRIVELINE LIMITATIONS

The present wheel driven speed record stands at 428 m.p.h., this speed must be broken by 1% which means a two way average of at least 435 m.p.h. must be obtained. It is planned eventually to obtain a speed of 500 .m.p.h. which will require a maximum engine speed of 3,500 r.p.m. It will be our intention to work on a limit of 3, 100 r.p.m. in all gears to break the existing record, this will give us a speed of approximately 442 m.p.h. After which we will assess the information acquired during these runs, and on that basis the r.p.m. range may be gradually increased. This will be done to minimize tile strain on components until the vehicle design limitations are reached, where necessary modifications can be put into effect.

ENGINE TO GEAR BOX RATIO 1 - 1

GEAR BOX TO DIFF RATIO 1.6 - 1

DIFF RATIO 1 - 1

ENGINE: SPEED TO MILES PER HOUR

RATIO

NOTE: It is intended to move the vehicle from a standing start under its own power. beginning. The tapered roller bearings are one of the major keys to the high speed of Woomera 1 giving enough reliability, the lowest life bearing being 113 hours. The vehicle has 56 tapered roller bearings in its drive line.

A large number of these bearings were hand picked from production batches, from which five of the best sets were selected and hand finished quality, giving one set of bearings in the car and four spare sets.

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