ROAD TEST: 1928 WINDHOFF 4-CYLINDER

A drying barn mimics the bold finning of the Windhoff's 750cc oil-cooled OHC 4-cylinder motor

The creations of Hans Windhoff began in Berlin with radiator production for cars, trucks, and aircraft. In 1924, he entered the burgeoning motorcycle market with water-cooled two-stroke machine of 125cc - an excellent although expensive creation, with the engine built under license from a design by Hugo Ruppe, whose ladepumpe (an extra piston used as a supercharger to compress the fuel/air mix) design was used most successfully by DKW in their GP bikes.

From Tragatsch's 'Illustrated Encyclopedia of Motorcycles' - the bible! And as full of omissions, but it has a ton of great information, and is still the best general reference on old bikes.

Windhoff had much racing success with these smaller two-strokes, although enlarged racers of 493cc and 517cc were less reliable. By 1926, a totally new machine was offered; the 746cc overhead camshaft, oil-cooled 4-cylinder. Only Granville Bradshaw (creator of the ABC) had successfully used an 'oil boiler' engine in a motorcycle, and the new Windhoff was a technical tour de force.
The engine, designed by Ing. Dauben (later to join Mercedes to work on their legendary W194 - 196 racers) had no external 'plumbing', using only internal oilways to keep everything cool, with the engine finning acting as a giant radiator, and recirculating oil the cooling agent.

A period drawing of a Windhoff engine and gearbox, showing the valve cover removed, and the OHC mechanism clear.  The low-overlap camshaft lobes are also visible - not race tuned! 

With all major castings in aluminum (barring the iron cylinder head), the massive engine is impressive and aesthetically pleasing, with an advanced single camshaft up top, very much like the best automobile practice of the day. No other 4-cylinder production motorcycle of the period had an overhead camshaft. The 63x60mm short-stroke engine produced 22hp at 4,000rpm, which gave an 80mph+ top speed. This engine performance is on par for other 750cc V- or flat-twin machines, and about the same as American 1000cc or 1200cc F-head 4s.  An engine came up for sale in Las Vegas back in 2010, which I wrote about here.

The Windhoff chassis is as radical as its motor, with no ‘frame’ to speak of, and no need for one, as the massive engine casting is far stronger than bent or lugged tubing.  It predates the Vincent in this concept by nearly 20 years, but the Windhoff is a true 'frameless' machine, as the forks and rear subframe (4 parallel tubes) bolt directly to the engine/gearbox unit. The trailing-link forks use double leaf springs for damping, and there’s no rear suspension; the rear frame tubes emerge straight out of the gearbox casting, and hold the final drive housing for the shaft drive, and rear hub and brake. Despite its massive appearance, the total weight of the machine is only 440lbs. The price when new was 1,750DM, a bit more than the 1,600DM of a BMW R63. A bit expensive, a bit unconventional, and a bit slow on sales, nonetheless the machine ranks as a landmark of vision and development, and is understandably very sought after these days.

While technically and aesthetically the Windhoff is extremely advanced, the overall engine design suffers from a lack of development which would have made it the smooth, quiet, and powerful sports tourer it deserved to be. Sadly, it suffered the fate of a launch at the worst possible moment, when world economic calamity sent incomes spiraling downward, and global motorcycle sales into the ditch. Like most other manufacturers of the late 1920s, Windhoff gave up the ghost, but their legacy is yet fantastic and speaks to a a visionary designer with an excellent idea. On price alone, the Windhoff was considered a luxury sport-touring machine, a category of motorcycling which no longer exists, as anachronistic as wearing a necktie in a Grand Prix race.

The camshaft drive chain enclosure is up front, and a timed breather alongside.  The single, rather anemic carb restricts performance, but it goes well for the period. The bolted-on gearbox is clearly seen, as is the depth of those footboards! 

But therein lies its attraction today; a cutting-edge machine with its gorgeous styling born equally of an engineer’s and designer’s eye. The stack of horizontal engine finning is the centerpiece of the motorcycle, and the paired steel bars stretching to the rear hub continue the theme. There’s very little tinware for shape, the machine is almost all mechanical business, barring a shapely fuel tank capping the motor, and the rearward sweep of the handlebars. All else is practical, even ordinary; the fenders are simple C-section with no valence, and the ancillary components are bought-in from the usual suppliers like Bosch.

Smooth handling from the leaf-sprung front forks of short-trailing-link design

The magnificence of the engine, and the strong lines of the rear frame tubes, are key to the Windhoff’s visual success; it’s a stunning motorcycle, among the finest designs of the 1920s. Four cylinders of 187cc make for an easy kickover, and a slightly ‘gear-y’ kick brings the bike to a surprisingly sporty exhaust note. The 2-into-1 exhaust has little baffling, so the power is delivered freely, and the engine revs free too. The 3-speed hand shifter lies about at knee level, and a lack of a shift gate isn’t a problem as the internal indexing of the gears is apparent by feel. The clutch works easily on the left hand inverse lever, and getting off in gear is a simple matter of balancing the revs on the right handlebar throttle lever with a gentle clutch release. There’s plenty of urge from the motor, which sends the rider singing along quickly, accompanied by an audible engine gear symphony, not all of which is sweet music.

Hans Windhoff

The engine feels rougher than might be imagined, and it’s clear – confirmed by the experts – that the Windhoff could use more development to become the machine it wants to be. Canting the machine through bends is easy, and the handling is solid, inspiring confidence…too much confidence it seems, as the footboards are enormous hollow castings meant to hold the tool roll, and aren’t sprung or flexible. I was thoroughly enjoying the bends of the Schwabian countryside, and approaching a tighter corner I looked forward to feeling the chassis challenged a bit. But the bike would have none of it, grinding away valuable footboard aluminum before I rapidly modified my riding position to ‘hang off’ and keep the bike more vertical, taking it a little easier on the remaining bends. I know what I’d change, if the bike were mine!

I've been acquainted with the road test bike for many years; this was a first encounter in 2010

The Windhoff is elegant and sporty to ride, with a glorious aircraft-like bark from the exhaust, and a bit of gear noise between your legs.  There’s no forgetting you’re aboard a real machine with lots of moving parts inside, and riding the bike is a machinist’s erotic joy.  It’s my understanding that long-term riding ownership means keeping after the motor, but nobody’s putting a big mileage on such a rare beast today.  In fact, it’s entirely possible the machine I test rode is the only Windhoff actually in use in the world, the others being fixed into mausoleums and static collections.  More’s the pity, as everyone who sees the Windhoff is curious, and enthusiastic about its amazing appearance.  Would that more people could sample its riding pleasures.

What Windhoff tried after the 750cc 4; a big sidevalve flat twin of more conventional construction in 1929.  In the end, they made a few more small two-strokes with Villiers-licensed motors, then vanished. 

A Windhoff at the Bonhams Quail Lodge sale in 2013

Rear end detail; a massive aluminum casting keep the rear frame tubes in line.

...and the final drive casting, with a lug for a sidecar fitment.  Never seen a chair with a Windhoff, though.

The inside of the 4-cylinder 750cc Windhoff motor; a 3-main bearing crankshaft, with a wet sump and oil pump on the left. 

The cylincer head top and bottom, showing the passages through which oil circulates, and the flat combustion chamber tops, as per automotive practice. The two large holes at bottom are the exhaust passages; the inlet manifold bolted on.  This and the photo above are from the book 'Pluricilindriche' by Ing. Stefano Milani.  A remarkable, and unobtainable book.

At the end of their tether, the Villers-licensed engine produced for other German manufacturers.  From 'Motorräder Aus Berlin', by Karl Reese.