Yes sad to say there was once a British make that was banned from competing at the TT because it was too technologically advanced. After that the word 'barred' was used in their advertising.
What make was it and why was it so advanced?

Zenith was the British manufacturer banned from the 1912 TT. The motorcycle was fitted with a 'gradua' or infinitely variable gearing system which the organisers felt would give the machine an unfair advantage.

Aha! Glad to see that woke you up, Kestrel, and got you posting. Knowledgeable person.... how about having a look at our quiz section and flummoxing our stalwarts in there?

Yes it was the Zenith and its Gradua drive.
I would like to see one and exactly how it worked. From what I have heard so far it had a primary belt and a secondary belt to the rear wheel. Just how the rear wheel could be adjusted for and aft is not too clear. One thing I read was that the primary pulley could be adjusted while in motion but the overall ratios could only be changed by adjusting the position of the rear wheel in the forks.
I suppose it meant that when you arrived at a circuit the bike could be set up for the conditions then the primary pulley could be varied during the race to maintain the optimum engine revs.
Anyone who knows may correct this understanding.
Makes you wonder if one of the current makers came up with a revolutionary transmission would it be barred.

Don.

The Gradua system was designed by Zenith engineer Freddie Barnes, and manufactured for Zenith by the Advance Motor Manufacturing Company in Northampton.

Essentially the system worked by using an adjustable front pulley, the diameter of which could be varied by moving the tapered cheek plates closer together or further apart. As the front pulley diameter varied then obviously the belt tension changed and this was compensated by simultaneously moving the rear wheel fore and aft in the axle slots, this was achieved by means of a linked worm drive system.

I read somewhere that the effective gear ratio at the back wheel was infinitely adjustable between around 8:1 and 3.5:1

Ah, we have large grinding machines that have this type of gearing.

My other half has a Micra auto and it runs the same way.

http://auto.howstuffworks.com/cvt2.htm

Was there not a Daf car that used this type of gearing :?:

The name Variomatic come to mind :?: :?:


http://en.wikipedia.org/wiki/Variomatic

Or was that a sewing machine!

Yes, I remember the DAF ? 55?

You may be thinking of Pfaff sewing machines MV.
The 'P' is silent as in sea bathing.

Did Honda make a CB400 with a system along this line, abet for only a short period?

Or am I barking up the completley wrong tree!

It was called Hondamatic and was a two speed automatic or maybe only semi automaitc..................a complete bundle of scrap IMHO

Honda have made "auto" transmission motorcycles, however not with belt drives but with atorque converter set up.

Honda started with the Hondamatic CB750/4, which first appeared in 1977, with a foot-operated gear lever to select neutral, low or high ratios. Low ratio would carry the rider smoothly to 60mph before switching to the high ratio - although you could pull away in high ratio with no problem although progress was leisurely. The bike was detuned from 65bhp to give 47bhp at 7500rpm, and ran lower compression (down from 9:1 to 7.7:1) than the standard model. There was no hand-operated clutch and instead a torque converter, very similar to the one used in the Civic, shouldered the load. A centrifugal hydraulic pump was driven by the engine and threw streams of oil at a veined turbine wheel. This wheel in turn drove the gearbox shaft and the oil drained back to the centre of the pump to be re-circulated again.

Effectively the 750 was a semi-automatic because the rider still needed to shift manually between high and low ratios, but it was more hampered by a lack of overall oomph than any problems with the transmission. It cost as much as a standard 750 but topped out at around 105mph at a time when its competitors were nudging 120. Around 9000 CB750 automatics were sold when the model was discontinued in 1978.

Honda had another bash at the same scheme with an automatic version of their CB400 parallel twin. This also used a torque converter and offered the rider a choice of two ratios. The motor wasn't detuned this time but the transmission sapped the standard 400's 43bhp to such an extent that the bike's performance suffered. The twin was never light on its feet and the lardy 400A could be outpaced by a commuter 250 - and so once again the public weren't tempted to turn automatic.

The high price of automatic motorcycles when new combined with their mass, complexity and poor fuel economy to make them thoroughly unappealing to exactly the audience they were supposed to attract.

Honda have thought about CVT bikes and had a prototype at the 2005 Tokyo Motor Show. I chose this photo at random. Article is below:


"October 24, 2005 One of the surprises of the 39th Tokyo Motor Show 2005 which opened on saturday was Honda's showing of a large-size sports motorcycle concept model dubbed the DN-01. The motorcycle is equipped with a continuously variable automatic transmission (CVT) and a water-cooled, 4-stroke, OHC, V-twin, 2-cylinder, 680cc engine. Most significantly, Honda stated that it "will continue the development of DN-01 with the goal of introducing it to the market in the near future."

CVT has already been introduced into the market in a range of scooters with Suzuki's futuristic Burgman scooter the most obvious shining example. Honda's version of the CVt is being touted as different to other CVTs and is described as an hydraulic mechanical continuously variable HFT (Human Fitting Transmission) system featuring two automatic modes and a 6-speed manual mode which the rider operates through buttons on the handlebars.

Moreover, this is the first hydraulic mechanical continuously variable transmission system in the world to be equipped with a lock-up mechanism, which improves the fuel efficiency while offering a smooth ride without feeling the shock normally associated with gear shifts, even when cornering. With the HFT, the DN-01 achieves more easy-to-operate and comfortable riding than currently available sports model motorcycles."

This is the most 'informative' site. I am privileged to belong to it. Nice to hear your 'voice' Malcolm.
Jan

I wonder why Honda never went with the oval cylinders that they had on the one off special. Would have thought a bigger area would get rid of the heat better and so reduce wear and tear of the cylinder... or would that much heat because of the extra surface area not be disperced properly using the normal liquid cooled cylinders?

Interesting problem for them though, so maybe this is why, the figures just don't add up.

Over to you Cargo matey.

Seems the Honda NSR500 had more than it's fair share of valves

The NR500 was an innovative racing motorcycle developed by Honda HRC in 1978 to compete in Grand Prix motorcycle racing. The NR stood for New Racing.

The motivation behind the NR500 was company founder Soichiro Honda's desire to compete using four-stroke engine technology since the majority of motorcycles manufactured by Honda used four-stroke engines. When the FIM announced new regulations for the 1968 Grand Prix motorcycle racing season that limited the 500 cc engines to four cylinders, this gave an advantage to teams using two-stroke machinery. Honda decided to withdraw from motorcycle racing to concentrate on Formula One racing.

In November 1977 Honda announced it would be returning to motorcycle Grand Prix racing using four stroke technology. Even though two-stroke engines dominated motorcycle Grand Prix racing in the late 1970s, Honda felt bound by their convictions to race what they sold and thus decided to compete using a high-technology, four-stroke race bike. Since a conventional four-stroke, four-cylinder engine could not produce the same power of its two-stroke rivals, Honda had to increase the valve area in order to be competitive. The rules at the time allowed up to four combustion chambers so honda designed a 32 valve v8 with four pairs of linked combustion chambers. This then evolved into an innovative engine with oval-shaped cylinders. The oval cylinders allowed room for 32 valves and eight spark plugs, the same as that of an eight-cylinder engine while staying within the four cylinder rules limit. Another innovation used on the NR500 was its monocoque body which wrapped around the engine like a cocoon and helped reduce weight. In an effort to reduce wind resistance, the bike also used 16-inch wheels instead of the mainstream 18-inch versions.

Honda overcame significant manufacturing problems to develop its oval cylinder technology and by late 1979 the bike made its much-anticipated debut at the British Grand Prix ridden by Mick Grant and Takazumi Katayama. Both bikes retired, Grant crashing out on the first turn after the bike spilled oil onto his rear tire. Katayama retired on the seventh lap due to ignition problems. Honda persevered for two more seasons but never managed to make the bike competitive. The monocoque frame had to be abandoned because it made it too difficult for mechanics to work on the engine during races. The 16-inch wheels also had to be abandoned for 18-inch wheels. American Freddie Spencer was able to reach 5th place at the 1981 British Grand Prix before the bike broke down. The NR500 never managed to win a Grand Prix, a thirteenth place by Katayama at the 1981 Austrian Grand Prix being its best showing.

Honda decided to abandon the project and designed the NS500 two-stroke bike to compete in the 1982 season. Spencer would ride the NS500 to Honda's first 500 cc world championship in 1983. Ultimately, what doomed the NR500 project was that Honda had tried to develop too many technologies at one time. The NR500 did experience a few successes. Freddie Spencer rode the NR500 to a heat race victory at Laguna Seca in 1981 and Kengo Kiyama won the Suzuka 200 kilometer race that same year.


For More Information - Honda Racing History

The oval pistons did make into one road bike the NR750









That makes doing the shims on my 400 look easy :roll:

I always thought that the NR750 road bike was as much an engineering exercise as anything else, just to prove they could. I guess most of the limited number they made never saw a road. I've never seen one.

To answer DCLUICE first question the reason they never really went anywhere with it was cost. For the relatively small performance gains it gives you over a conventional round piston the extra production coats are huge.

There are also a lot of technical difficulties with oval pistons, it's easy to make a round piston ring that expands and seals evenly but it is very hard to do it with an oval piston ring. Same with pistons, round things expand much more evenly than oval things.