NSU 250 Sportmax

NSU Sportmax 250 1955

Late in 1954 NSU announced that it was withdrawing from world championship racing. As justification for its decision the company cited the complete success of its sports program and the evident superiority of its motorcycles. From that time on, both the Rennfox and the Rennmax disappeared from the racing scene. But in 1955 NSU prepared, in an unofficial manner, a sports model based on one of its production motorcycles. It was called the Sportmax 250.

In the Sportmax version the NSU technicians got 29 h.p. from the engine, while the production model was less than 20 h.p. The Sportmax 250 had a fine chassis and bell fairing that made it comparable to the Rennmax. The Sportmax was highly ma-neuverable and stable, thanks in part to its light weight—about 240 pounds. Herman Muller rode the motorcycle to the 250-class world championship in 1955. This was the first time in the history of motorcycle racing that a vehicle not specially built to compete for a title had the speed and endurance to win a world championship.

NSU did not return to racing in 1956. But for some time individual German and British racers—John Surtees and Mike Hailwood among them—continued to compete with the Sportmax, riding against the Italian MVs, Mondials, and Guzzis.

Motorcycle: NSU Sportmax 250

Manufacturer: NSU Neckarsulm

Type: Racing, derived from production
Year: 1955
Engine: NSU single-cylinder, four-stroke, with single overhead distribution shaft, controlled by connecting rods.

Displacement 246.8 cc. (69 mm. x 66 mm.)
Cooling: Air
Transmission: Four-speed block

Power: 29 h.p. at 9,600 r.p.m.

Maximum speed: About 130 m.p.h. (with bell fairing)

Chassis: Single-bar in stamped plate, with engine projecting and suspended.
Front wheel: Swinging-link suspension;
Rear wheel: Telescopic suspension

Brakes: Front and rear, central drum with double cam

NSU Sportmax 1958

1958 NSU. "SPORTMAX". Although N.S.U. had been so successful with their "works" racers in both the 125 and 250 c.c. classes, the machine they used was far too specialized ever to be a practical proposition for a private owner to maintain.
However, the factory did realize that they would gain valuable publicity by some private owners racing their products and accordingly they released a few "Sportmax" models.

These machines were based on the standard production "250s", the "Max" and "Super Max", and in the years following the factory's sale of real racers there were a good many private-owner conversions of the roadsters into pseudo-racers. They didn't go as quick!
The cycle parts of the "Super Max" were very similar indeed to those of the "works" twins, with a spine-type frame made from a pair of deep pressings placed back to back and welded along their edges, a method of frame making that has been extensively used by European factories, especially for ultra-lightweights and mo-peds. Pressings welded together were also used for the rear swinging-fork and for the front fork main members.

 The photograph shows this quite well.
Alloy rims were employed and the hubs were altogether more massive than the roadster pattern.
Surprisingly, the engine, at any rate externally, did not differ in any major way from "standard". The operation of the overhead camshaft was by means of rods and eccentrics.

A pair of rods, rather like connecting rods with a "big-end" at each end, fitted over eccentrically mounted, thick discs on the half-time pinion and on the end of the camshaft so that, as one was rotated, the other had to follow suit. This method of camshaft operation was not new, for it had been employed in the twenties on Bentley cars.
A few of the "Sportmax" machines reached England and with one,

John Surtees achieved a great number of successi —before his M.V. days. With the same model, Mike Hailwood followed in John's shoes, winning at almost every short circuit in England during j the 1958 season. Later he acquired other, faster] "250s" and the success of the N.S.U. waned.

SPECIFICATION
Engine: single-cylinder 250 c.c. o.h.c; drive to ca
by eccentrics and rods. Ignition: coil.
Transmission: primary gear train to four-speed gearbox;
final drive by chain. Frame: welded-up pressed spine type; swinging-fo1*
rear suspension. Forks: leading link.

The Rise and Fall of the NSU Empire

From Knitting Machines to World Championships and Finally, Obscurity
By Dave Tharp, Virtual Museum Curator

Lightweight street motorcycles just never caught on in the Americas -- except for a brief time in the late 1960s when you could meet "the nicest people on a Honda." However, in Europe, bikes displacing under 500cc have always been the workhorses, providing economical transportation, serious sport and touring capabilities, and even towing sidecars.

In 1910, NSU set a US coast-to-coast "cannonball" speed record.

Because of this big-bike myopia, many riders have consistently overlooked the excellent European lightweights, including the NSU -- arguably the best of them all.

At the turn of the 19th century, the small factory town of Neckarsulm, in southern Germany, was the home of a company that manufactured automatic knitting machines as well as a successful line of "safety" bicycles (bicycles with two small wheels and a chain drive, as opposed to the "penny-farthing" big-wheeled types). This company went by Neckarsulm Strickmaschinen Union (Neckarsulm Knitting-machine Union), a name that described their business accurately enough, but is quite a mouthful for the non-Germanic. Hence, they eventually adopted the initials NSU.

Before the name change, their bicycle subsidiary's name -- Neckarsulmer Fahrradwerke -- was just as difficult to pronounce, but it did appear on the tanks of their first motorcycles. These appeared in 1901 (two years before the first Harley-Davidson), and consisted of a 1.5 HP Swiss-built Zedel engine (another copy of the DeDion-Buton) clip-mounted on the downtube next to the crank assembly of one of their standard bicycles. Final drive was accomplished via a flat leather belt that connect a pulley on the crankshaft to a pulley on the rear wheel.

Not satisfied with the Zedel, NSU introduced their own singles and V-twins in 1903. This rapid pace of development continued, and the factory introduced a liquid-cooled single in 1905, and a revolutionary swing-arm rear suspension motorcycle in 1914 (still belt-drive, though).

The NSU V-Twin engine, circa 1905. Note the "atmospheric" intake valves, opened by the suction of the piston going down. Photo by W. Conway Link, Deutsches Motorrad Register.

During this period, racing success for the NSU factory led to fame and a greatly-increased export market. It's likely that the unpronounceable name lead to the reduction of the tank emblem to the initials "NSU," or perhaps there was a paint shortage.

NSU was heavily involved in war production during W.W.I. After the-war-to-end-all-wars, demand was very high for motorcycles and they responded with a wide range of models. These included sidevalve and OHC 250's, sidevalve 500 singles, and V-twins of 500, 750, and 1000cc displacements.

In 1929, NSU hired Walter William Moore away from Norton, where he had recently completed the design of the CS1, a towershaft-driven OHC 500cc single (also known as a "bevel drive," as in bevel-drive Ducatis -- a bevel gear on the crankshaft drives another bevel gear on a driveshaft that parallels the cylinder. At the top of the cylinder, another bevel gear drives a fourth bevel gear on the overhead camshaft), the forerunner of the fabulous Norton Manx. By 1931, NSU was producing excellent towershaft-driven OHC singles that were highly successful. NSU became one of the largest producers of motorcycles in the world in the 1930s. Starting in 1937, Moore and Albert Roeder designed supercharged DOHC GP twins in 350cc and 500cc flavors. These bikes were unsuccessful before the war due to reliability problems, but performed well after the war when the bugs were worked out.

Unlike the Allies, the German Army had a great deal of faith in motorcycles as weapons of war. Motorized rifle regiments equipped with heavy BMW and Zundapp sidecar rigs were present in every armored division. Meanwhile, NSU produced one of the weirdest military vehicles ever conceived.

The Sd. Kfz 2 Kleines Kettenkraftrad half-track-- Who thought this up, anyway?

The Sd. Kfz 2 Kleines Kettenkraftrad (Small-Tracked Motorcycle) was a light armored vehicle with the front end of a motorcycle attached to the rear end of a half-track. The handlebars operated differential brakes on the tracks as well as turning the front wheel. Powered by an 1500cc 4-cylinder Opel engine, it was produced by the thousands to equip Wehrmacht Panzer units.

More-or-less undamaged in the war, NSU immediately switched back producing consumer motorcycles. In 1950, a towershaft DOHC 4-cylinder 500 was designed for the GP circuit, but it was decided to campaign 125 and 250cc machines based on single- and two-cylinder slices of the 500. These smaller machines, the Rennfox and Rennmax (the Fox and the Max were NSU's 125 and 250 streetbikes) were world-beaters, repeatedly winning world championships until NSU officially withdrew from racing in 1954. The streetbikes weren't exactly slouches either. The Fox and the Max were SOHC singles of moderate output, high durability, and excellent fit and finish. The engines had a unique cam-drive system consisting of two reciprocating connecting rods driven by eccentrics on a reduction gear, and driving eccentrics on the end of the camshaft. If you can picture the driving wheels on a steam locomotive, or the pedal rods in a kiddie car, you can almost get the picture. This system was silent, efficient, trouble-free, and so compact that the top end of the engine can easily be mistaken for a two-stroke. The motor could spin to then-astronomical revolutions that destroyed chains and formerly could only be achieved by towershaft drives.

This fact was not lost on the racing department, who fiddled with a Max engine until it produced nearly the same power as the DOHC twin: 30 hp at over 9000 rpm.

In spite of having officially withdrawn from racing, the engine was installed in a Max streetbike frame, fitted with aluminum bodywork and a dustbin fairing, and given to Herman-Peter Mueller, the 1954 250cc World Champion. Named the Sportmax, the bike was ridden by Mueller to another World Championship in 1955, making it the only streetbike-based motorcycle to ever win a world GP title.

The 1955 semi-works, World Championship-winning Sportmax 250

During the 1950s, NSU also produced vast quantities of 50 and 100cc Quicks and Quicklys, as well as Lambretta scooters under license and their own Prima scooter. But motorcycle production was doomed by the success of their small car, powered by a 4-cylinder engine based on the Max design, still with the eccentric/pushrod cam drive system. In 1957, NSU sold the entire motorcycle facility to the Yugoslavians, who moved it all to Sarajevo.

In the 60's, NSU obtained the sole license for Germany to the Wankel rotary engine. They developed a highly successful version of it, and produced large numbers of compact cars with it. For this reason, they were absorbed by VW-Porsche-Audi. Although NSU no longer produces cars, they still manufacture a fair number of small Wankel engines for utility applications.

Today, the former NSU motorcycle factory in Neckarsulm is now a museum housing one of the finest collections of bikes on the planet.

Source home.cogeco.ca