Honda NR 750

The NR 750 is a motorcycle with an oval piston engine from the Japanese motorcycle manufacturer Honda , 300 of which were built in 1991 and 1992.

history

development

The story began in February 1978 with the Honda NR 500 Grand Prix model . At that time, the performance advantage of two-stroke engines over four-stroke engines in the 500 cc class of Grand Prix racing increased more and more. Since every cylinder fires once per crankshaft revolution in a two-stroke engine, but only every second in a four-stroke engine, a two-stroke engine has twice as many work cycles at the same speed and thus an advantage in terms of liter output compared to a four-stroke engine. Honda was also unable to increase the rated speed of its engines with smaller, but more, cylinders because the number of cylinders was limited to four in the regulations. That is why the Honda engineers designed the oval piston engine. So to speak, two cylinders have been merged into one with a superelliptical basic shape. We succeeded in satisfactorily solving the problem of the piston seal. It had eight valves and two spark plugs per "cylinder". This enabled the desired short stroke with a high maximum speed. Despite an output of 115 hp at 17,500 rpm, it was inferior to the competition with the two-stroke engines.

Honda made a new attempt in 1987 with the further developed NR 750 at the endurance race in Le Mans . With almost 160 hp at 15,500 rpm, it was superior to its competition (approx. 130 hp) and thus achieved second place on the grid. In the race she was eliminated due to a defect, but was able to demonstrate the superiority of the concept. Shortly afterwards, oval piston engines were banned by the FIM .

The roadworthy NR 750 resulting from the 750 racing version still had 125 hp at 14,000 rpm and a weight of 230 kg in series production. Despite its factory abbreviation RC40 , this is more of a sports tourer than a racing machine.

marketing

300 pieces of the super sports car were offered worldwide , the price at that time was 100,000 DM .

technology

engine

Oval piston engine

In the 90-degree V-4 stroke engine four oval piston collaborating with the dimensions 101.2 x 50.6 mm (corresponding to a bore of 75.3 mm) and a stroke of only 42 mm on each of two connecting rods made of titanium .

landing gear

The chassis consists of an aluminum bridge frame, an upside-down fork with a 45 mm standpipe diameter at the front and a single-sided swing arm made of cast aluminum with a central nut at the rear.

Rims: 3.5 × 16 inches at the front, 5.5 × 17 inches at the rear
Tires: 130/70 ZR 16 inches at the front, 180/55 ZR 17 inches at the rear
Brakes: double disc brake 310 mm at the front, single disc brake 220 mm at the rear

Remarks

↑ Stefan Zima differentiates in his book Unusual Motors (Vogel-Verlag, Würzburg, 3rd edition 2010, ISBN 978-3- 8343-3140-3) between oval pistons and the arena-shaped pistons of the Honda NR; accordingly, the arena cross-sectional shape corresponds approximately to a centrally cut circle, the semicircles being drawn out and connected in a straight line; In the article Superellipse this corresponds roughly to the green case n = 5 in the drawing. Oval pistons (shape: ellipse with axis lengths 76.5 mm and 99.95 mm) were tested at VW in a diesel test engine with 2.3 L displacement (Auto, Motor and Sport 14, 1990).

literature

Alan Cathcart: Final: Honda NR 750 - Retrovision . In: motorcycle . No. 5 , 2012, ISSN 0027-237X , p. 126-130 .

Individual evidence

^ Organizing the NR Block: Preparing for a Comeback. Honda Motor Co., Ltd., 2012, accessed on December 9, 2012 (English): "The project was officially launched at HGA in February 1978."

↑ http% 3A% 2F% 2Fwww.grandprixengines.co.uk% 2FEgs_69_70_71_Honda.pdf

↑ Honda NR 750 with oval piston engine. Motorrad Online , February 15, 2012, accessed December 13, 2012 .

↑ Data Honda NR 750 (RC 40). (No longer available online.) Motorrad Online , February 28, 2008, formerly in the original ; Retrieved December 13, 2012 . ( Page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2

Web links

Commons : Honda NR 750 - Collection of pictures, videos and audio files

All tests for "Honda NR 750". Motorrad Online, January 14, 2011, accessed December 6, 2012 .

[4] Stefan Zima differentiates in his book Unusual Motors (Vogel-Verlag, Würzburg, 3rd edition 2010, ISBN 978-3- 8343-3140-3) between oval pistons and the arena-shaped pistons of the Honda NR; accordingly, the arena cross-sectional shape corresponds approximately to a centrally cut circle, the semicircles being drawn out and connected in a straight line; In the article Superellipse this corresponds roughly to the green case n = 5 in the drawing. Oval pistons (shape: ellipse with axis lengths 76.5 mm and 99.95 mm) were tested at VW in a diesel test engine with 2.3 L displacement (Auto, Motor and Sport 14, 1990).

[HRC_1978-1] Organizing the NR Block: Preparing for a Comeback. Honda Motor Co., Ltd., 2012, accessed on December 9, 2012 (English): "The project was officially launched at HGA in February 1978."

[2] ttp% 3A% 2F% 2Fwww.grandprixengines.co.uk% 2FEgs_69_70_71_Honda.pdf

[Motorrad_2012-3] Honda NR 750 with oval piston engine. Motorrad Online , February 15, 2012, accessed December 13, 2012 .