Steely Dane
The long-lived inline-four from Denmark, made for 25 years in largely unchanged form, is a quirky but practical classic.
Barry Winter, the keeper of this 1939 Type C Nimbus 750, stood next to me as I first contemplated the blue bike. After a long silence, the best I could come up with was: “It’s like… it’s like… it’s not like anything else at all!”
When introduced in 1934, the Type C had been technically innovative in many ways. The inline four format was more familiar then, with Belgium’s FN produced in the 1920s, and the US Henderson, which morphed into the Indian Ace, in the 1930s.
But a motorcycle with an overhead camshaft engine, built in unit with a car-type single plate clutch and gearbox, with horizontally split cases, coil electrics, shaft drive and telescopic forks – that was going some. And where Indian Ace production petered out after 1942, the Type C, little changed, had continued to be made until 1959. I gazed on the Nimbus with bewilderment, awe... and a touch of fear. After all, I was going to have to ride the thing.
Winter is coming
Barry Winter is a capable engineer with a good collection of classic machines, several of which have featured in TCM (see July 2018 for his superb AJS Model 20 twin). He had started to pay attention to the Nimbus marque while attending an invitation-only classic rally in the Auvergne, France. This was the biannual ‘Terrot Endroit’, organised by Pascal Bouculat.
Pascal puts in thousands of miles on his Type C, scouting the rally routes as well as thrashing it all over Europe, two-up. Also at that rally were a couple more of the fours from Denmark, one from England and another owned by a married pair that had been ridden up from Spain. These distinctive machines appeared to be capable classic tourers.
Barry started looking around, and eventually bought his Type C through H and H auctions, paying a bit over the odds as the Nimbus was in nice condition, having been rebuilt and thoroughly renovated in Belgium. It was badged a Sports model, with the latter’s highlevel exhaust. The 22bhp Sports variant featured 5.7:1 compression pistons, against the standard 18bhp model’s 5.4:1 type. However, Barry believes that his bike has had a new engine (one with no engine number) fitted during the restoration. He hasn’t stripped the 746cc engine to find out which kind it is (if it ain’t broke…)
What he does know is that his Type C is on sidecar gearing. Many Nimbuses (Nimbi? Nimbae?) were attached to chairs – the company built its own – as the four cylinder engines’ combination of power and flexibility suited that function. That included quantities of those sold to the Danish Post Office, police and armed forces, which represented about a third of the 12,715 Type C machines produced.
These motorcycles, despite their advanced features, were workhorses, and today about half the total production is thought to have survived. The public service element is believed to have contributed to the Type C’s relative absence of post-Second World War development, as it was felt that the fleet buyers, Army
“It’s like… It’s like… It’s not like anything else at all!”
etc, would not welcome the need to purchase new lots of different spares.
The gearing can be altered by changing the greasepacked spiral-bevel final drive of the Cardan-type shaft drive. Barry may do that. “The sidecar gearing means it revs a bit high. At 50-plus mph it’s revving higher than you’d want, though it can still cruise happily at 50.” Pascal Bouculat has been Barry’s helpful guru with his Nimbus, reassuring him about the model’s reliability. Visually one of the most noticeably ‘unreconstructed’ features of the engine is the exposed valve gear, done to promote engine cooling, and from experience Pascal could confirm that though the valves – on each side of the enclosed overhead camshaft – run dry, he has found no need to oil them more than occasionally. Pascal also said that their clearances should be set differently than the manual advises; and that 20-50 oil is fine for the wetsump engine’s 4.5 pint capacity, though Barry favours straight 50.
Something the Frenchman can’t help with is the way the rear end of the flat-steel, bolted-up chassis bounces off-line vigorously over bumps. “It does jump around a bit,” said Barry. “I don’t carry a pillion on it, so I’ve made the sprung rear saddle rigid with a couple of brackets – I was using it for a parcel rack, and packages were getting bounced loose! But overall the Type 3 handles well.”
Another quirk is the Jawa-type kickstart pedal, which folds out sideways from the near, left side. To use this the bike has to be on its centre-stand, and a combination of its 408lb catalogued weight (only
7lb lighter than a Fastback Commando), and a stand design which means the machine has to be lifted up rather than rolled onto it, makes this a chore. Luckily Barry is a strong guy, but for an easier life parking up or manoeuvring, he’s fitted a side-stand.
Barry pointed out one further feature of the fab four. The left-foot gearchange is for a box which remained three-speed – and which required a very, very deliberate change to avoid graunching and false neutrals. “There’s a guy in Denmark who does a four-speed conversion, I believe,” said Barry. “I think that couple from Spain at Pascal’s rally had fitted it.”
Nimbus: There is nothing like a Dane
The Nimbus motorcycle came from an unlikely source: Nilfisk, a very extensive Copenhagen factory which manufactured Europe’s first vacuum cleaners. Cofounder Peder Anderson Fisker, a skilled mechanical engineer, decided to broaden the product line for 1919, with a perfected motorcycle.
He looked closely at FN’s inline four, and came up with an air-cooled ioe (inlet-over-exhaust) 750 with separate cylinders. This engine was housed in a frame where the long tubular top member doubled as the petrol tank, and gave the machine its ‘stovepipe’ moniker. Boasting swinging-arm rear suspension,
1252 of the famously robust Stovepipes in Type A and B versions were made before 1928 when production ceased. This was partly due to a swingeing Danish government tax – how do you like 180%? – imposed on motor vehicles in 1924.
But Fisker’s son Anders had been given a Stovepipe for his 18th birthday in 1926, and graduating as a mechanical engineer, from 1932 developed the new machine. Aided by his father, the Type C was ready for production in 1934. With their own foundry, almost everything for it was made in-house. The engine was still a 746cc (60 x 66 mm) inline four, but now an ohc design, and with the iron cylinder block and upper crankcase cast as one, permitting a horizontal joint with the upper cylinder block. Inside, a very substantial crankshaft ran on two large ball races. A geared pump supplied oil from the wet sump to the crankshaft, the camshaft and the gearbox.
The dry clutch was a single-plate car type, and the gearbox featured straight-cut teeth. Initially handchange, conversions to foot-shift were available from 1937.The slim final shaft drive was via a Cardan shaft, that is one with universal joints at each end. All this sat in a chassis fabricated from flat steel bar, riveted together. It wrapped protectively around the 2.75 Imp gallon petrol tank. The frame no longer featured any rear suspension – weight, or price, or both, may have been considerations – but at the front now were slim telescopic forks, at first undamped, but with hydraulic damping following for 1938. The wheels on Barry’s Type C are 3.50 x 18, and the seven inch brakes front and rear were entirely adequate for the C’s modest output.
The engine rarely leaked oil. Part of this was due to a steel breather tube running down from the suction side of the bronze carburettor to the sump, which promoted negative crankcase pressure. Inside the pipe there was an oil trap to send most of the oil and mist back to the sump, while letting small proportions of oil mist into the carb, to then lubricate the valve guides and stems. The breather tube also affected the motor’s
tickover. The pistons acted as an air pump in the sump; they had to balance with the incoming air through the carb, hopefully in complete alignment with the air slide. Adjustment is not always easy, but Barry has had no problems so far.
The Type C featured six volt coil ignition, with the coil an integral part of the distributor’s cap. The bottle-shaped dynamo sat ahead of the cylinders with the distributor above it, both on the same drive. The regulator relay was housed in its own circular steel case beneath the saddle. The lighting was controlled by the left-side twistgrip, giving four positions. The pressed steel instrument panel over the handlebars carried the switch for the ignition key, and at the centre of a stamped steel circular plate bearing the frame number, a red ignition warning light. The kph speedo and an ammeter completed the picture.
In sum, the engine’s low output and excellent torque made for a practical, durable, user-friendly machine rather than a roadburner. By the end in 1959, the Type Cs with their 75mph absolute top speed were no longer good for the police as a pursuit vehicle. But their unique character and reliability have made them a minor cult today.
Since I’d never started or ridden a Jawa, Barry did the business, easily, with the knurled sideways kickstart on the Type C’s warm engine. If we’d been starting from cold, we’d have snapped the twistgrip open two or three times, as there was a pump on the carb which this operated, to supplement the three-position choke lever incorporated into the carb.
Climbing aboard the 28 inch high driver’s saddle was easy, and we were away. The clutch was light but the down-for-first gearchange had proved crunchy to the point of graunch. I was relieved to get up into second, and on narrow village roads get to grips with the feel of the Nimbus.
Road surface was not the best but we weren’t going fast enough yet to provoke the bouncing back-end. Everything else was positive; the engine ran smoothly, the plot seemed well balanced, and with the weight down so low – that massive sump – felt firmly planted
on the road. The front end was reputed to bottom out over-easily, but what I noticed was how it didn’t whiteline, steering very satisfactorily over the uneven surfaces. This was okay.
Approaching the junction with a busier throughroad, the brakes pulled us up well, but I kept the engine nervously revving so as not to stall; hauling it up on that stand could mean a trip to Hernia Gulch. Several bish shots at changing it down into first meant that eventually I pulled away in second, which on this gearing the Nimbus was happy to do. In among slow traffic the Type C was perfectly composed, with a smooth twistgrip running on ball-bearings and the engine delivering solid, reassuring mid-range power; it certainly felt like the new, low mileage engine that Barry supposes it to be. The Type C was known as ‘the Bumblebee’ due to its buzzing exhaust note, but from the saddle the sound was a subdued, friendly growling whir, which when we’d (eventually) got into top and throttled on, was supplemented by the higher singing whine from the straight-cut cogs in the gearbox.
The gearchange did continue to be a pain – how can a neutral appear above top/third gear? – so I was happy to settle down in top for a few miles and literally just enjoy the ride. We did get one big rear-end buck from a pothole, but the Nimbus remained composed; the roadholding felt very reliable, and an indicated 80kph, around 50mph in top, though busy, gave no sense of stress from the engine. I even got a little better with the change, recalling pre-1950 car experiences, and double de-clutching.
You could easily get used to the Type C’s unflustered running. I was still on the nursery slopes, but the way the plot handled turns and roundabouts suggested that, with more familiarity, the Nimbus’ reputation for excellent cornering would be justified. It was a very satisfying machine to ride.
When I was riding in Africa, there was internet news of a couple of Scandinavians going round the world on a brace of Type Cs. Admittedly short acquaintance with Barry’s bike suggested that this could have been a End viable venture. I hope they made it.