HOSSACK 1
The story behind the first bike
Description:
The HOSSACK front suspension system consists of 2 wishbones, an upright and steering linkage. Similar components are found on the front of all racing cars, the only significant difference being in the upright which has its geometry rearranged.
The wishbones look and work exactly like their racing car equivalents. The upright performs the same task as its racing car equivalent but has its axle rotated through 90 degrees and is over hung. There are few restrictions on how the upright is made or what it's made from; it could be fabricated, cast or laid-up. The steering link is a little clever though, as it has to pivot on roughly the same axis as the upright. There is a handlebar pivot but this carries none of the suspension loading and only has to handle the weight of the rider's upper half. Norman has run the spring/damper element in several different positions to achieve different conditions as is also common in the racing car world.
In all but HOSSACK 1 (and thirty years later in the Ducati Hossack), the upright has been made of welded pressed-steel profiles making a very strong and light shell structure. Detailed stress analysis later showed the upright could not have been made much lighter even if it was made in aluminium. Further analysis done in Germany for the demanding TUV testing which the HOSSACK BMW was awarded, showed that Norman got his numbers a little wrong because the axle structural stiffness was five times stiffer than a standard BMW (over kill)! TUV approval was duly awarded.
Theory:
Before Norman left McLaren he raced a 350cc Yamsel at club level. He found that when braking very hard into Druids hairpin at Brands Hatch for example, the bike could be made to judder. This he attributed to flex so Norman set out to stiffen up the front end of the motorcycle. His first design (1974) was a braced telly which he never built because it became clear that an additional and real weakness was the steering head structure itself. He knew that there had to be 'triangulation' in the structure, only in that way could he achieve the stiffness-to-weight ratio he wanted; so wishbones on bikes were GO. Back then telescopic forks were very flexible and no match for today's upside-down units but even the best telescopic forks could never come near the stiffness-to-weight ratio this design could achieve. Once you have real stiffness inherent in a design you can both soften and direct that stiffness by using rubber bushes; the reverse is not possible.
Geometry:
Here the design opened up new opportunities that others could only dream about.
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It could have a constant wheelbase
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It could have constant trail
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It could have a constant head angle
It was possible to juggle with these options and even have non dive, anti-dive, or pro-dive or all three in one set up. It was even possible to imitate the geometry that telescopic forks provide. By choice Norman ran the axle path near to vertical to limit dive but soon discovered that this can cause a 'newcommer' problem - riders who have always ridden with tellies can struggle to get used to bikes that don't 'nod' on braking, this is how they have learned to judge how hard they are stopping. However after some exposure to this non-dive characteristic the gains become apparent.
Hossack 1 made an appearance on the BBC's Tomorrow's World TV programme in 1981. Norman had track-tested it early in 1980 and raced it in1981 and 82. Later a friend introduced Norman to Vernon Glashier who became its owner and then, thanks to his skills, things began to happen. Glashier won the BMCRC (Bemsee) single championship in 1983 and in the same year the next HOSSACK a 250cc Rotax engined machine won the Bemsee 250cc championship. Two out of two! Vernon went on to win the British Single Cylinder Championship in 1986, '87 and '88 and set lap records everywhere. The 500cc bike won its last championship when it was almost ten years old! Vernon retired Hossack 1 when the class changed to 600cc- a bigger engine would just not fit.
The Story:
Designed in the mid-70's from ideas worked out with a bent coat hanger nailed to a piece of wood, the first parts were made just to test the function. Later Norman found a pair of wheels in a scrap yard and made his creation modile so it could be pushed down a hill to see what it would feel like.
Much later a friend bought the project an engine, a Honda XL500 single. It took some cunning but Norman managed to squeeze it into the frame and made it a runner. It first ran up and down the roads of a Slough trading estate late 1979 - it worked!!
At that time the only other innovation on bike front ends was the Defazio hub center steering system which deserved much more credit than it got. Later came , the single-sided ELF steering project, which Norman blames for the demise of the 'alternative suspension movement'.
Why, people asked, with all their budget and influence could ELF not match the performance of the conventionally steered race bikes that they were up against which, in later grand prix versions used the same Honda engines? Normans answer: "crap design".
Next in the Hossack 1 development came some proper wheels from Tony Dawson: Astralites. Eventually it became a racer, which it had to be if it was going to go any further. It took time because Norman had no way to fund it properly and what funds there were, were stretched to cover three patents at the same time. It appeared in Motor Cycle News in 1980 after it had been round Brands Hatch a few times.
The Design:
The frame design started with some observations then some theory.
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Observation 1 - the McLaren M23 had a front wheel weight of approxiately. 250lbs on each front wheel and the structure which held that wheel (top and bottom wishbone) weighed only 3lbs yet provided huge stiffness. Now the front end of a bike had similar weight but the forks were heavy and worse, they were not very stiff.
NOTE: Why this preoccupation with stiffness? Answer the other side of the same equation is low weight! So Norman set out to design a system that could be triangulated and just as importantly be symmetrical. -
Observation 2: the essence of a good wishbone is that metal goes directly between the load points in straight lines, the curvy devices on the front of the ELF for example are not wishbones.
NOTE: the ELF, the Yamaha and Tony Foale's machines were all single sided so non symmetrical - this means more metal is required to achieve the same stiffness.
HOSSACK 1's frame as a whole almost obeys Norman's rules of what a wishbone should be; the only compromises were that direct lines between the load points could not be achieved. Still the frame design was good enough to win a championship 10 years later, so though Norman claims he could have made it lighter there was no need. The bike weighed 215lbs in race trim, the engine contributing to close on half that total.