Alternative motorcycle front suspension systems. 3

[thegardener]

I am researching alternative front suspension design on motorcycles. If anyone has any good links to sites, or can recommend any literature or contacts, please get in touch.
I'm particularly interested in contacting designers.
Thanks

 

[mburgess]

Do a search for Tony Foale (check surname spelling) he has written a number of articles & I believe published a book on motorcycle chassis design. Examines girder, sax trax, elf & other alternate designs.
Happy Searching.
MB

 

[R1100S]

Foale's books are an excellent place to start.

Start asking around BMW forums, or go to there web page. They currently have a telelever front end in production and are coming out with a doulever. Norman Hossack(probably misspelled) is the inventor of the Hossack or doulever front end and has some interesting things to say on his website, sorry no link.

If you are looking for center steer hubs, Bimota and Yamaha have produced working designs, I beleive the firm ELF did a lot of engineering on these many years ago.

 

[finman]

You'll find a guy called Difazio actually developed the Hub centre steering system, whilst Foale & Bimota utilised them in road going bikes.

Royce Creasey built a car engined (reliant) motorcycle, called a Quaser, that was a semi enclosed, Feet forward riding position deal that had hub centre steering around 20 odd years ago, somewhat earlier than BMW and Honda.

Hub centre steering does seperate the suspension and steering forces but give a very limited lock.

MZ had a bike that had a swing arm front end, looked appalling but actually worked very well, a system that has been employed by many sidecar firms as a retro fit for solo bikes being fitted with chairs.

Most of BMW's offerings are gimmicky and don't actually address the problem of seperating the forces and movements of suspension and steering.

 

[R1100S]

No, BMW's telelever does not seperate steering form suspension. What it does do is prevent the forks from diving during braking. There is still weight transfer, but the braking forces travel through the A-arm rather than causing the forks to compress.

 

[magnograil]

There are many ways to prevent dive during braking and the telelever design can be set up for rise, neutral or dive. I am not familiar with how BMW set theirs up. However, one reason for wanting front end dive is so the trail and steering castor angle decrease to lighten the steering effort under braking.
Elf's centre hub demonstrated a weakness to the design, leaning into the swingarms often caused them to ground and resulted in a crash. Ask Ron Haslem how often he crashed from this.
Modern telescopic forks use coatings on the stanchions to reduce stiction, titanium nitride or "carbon like diamond", and decouple the braking effects from suspension.

 

[mburgess]

In addition to the whole argument, you need to reprogram the rider to base their 'feel' onto a new sequence of events. The engineer can tell the rider that that it is better but if it goes against 15 - 20 years of riding experience the rider will not feel comfortable with the action. I think this is why BMW have designed a certain amount of dive into their geometry.

 

[finman]

I totally agree with mburgess, after years of riding conventional bikes I had a Yamaha GT with HCS, the feel of the front end was totally different especially during corner braking it took ages to loose the habits of 20 years of riding.

IMO the ELF bike had a design flaw (comprimise!) in the front swingarm, but you're pretty well stuck with ungainly arms due to the angle of the wheel on full lock. Bimota have achieved the best looking solution to the difazio design although the Yam came pretty close. Can't comment on the Bimota from a riders view (I'm on an engineers salary).

 

[spalders]

Have a look at

http://www.tonyfoale.com/

and you'll find you can order direct.. very good stuff..

The original designers seemed to want to limit a motorcycles pitch, and therefore weight transfer under braking; current racing front tyre design relies on this weight transfer to squash the tyre and increase the contact patch.

What we need to do now is review the various designs and work out what other benefits they brought..I would suggest a new variation of the Hossack design would allow full 'dive', but would not have any stiction, would allow tunable flex in the assembly and have better aerodynamic section.. (it cant be a lot worse than the two massive great outer fork tubes they are currently using!!)

 

[tejas1]

Just my $0.02, John Britten designed a marvelous bike from scratch. He designed the whole machine including an advanced front suspension. If you search his name at the very least you'll see an amazing machine.

Unfortunately he passed away a few years back.

 

[spalders]

Now of course we have the Crysz machine (Cycle World Mag January 05). It took an architect to see the paucity of ideas in the current MotoGP pit lane, and a well monied one to do something about it. Little on his machine is totally new but all the 'alternative' (old and forgotten?) ideas are very good solutions to current problems.. flex from the front 'forks', single shock controlling the front; offset adjustable at the axle; counter-rotating cranks (now that is new!!), inline crank for narrow sides (the new bit being the tilt forwards and the counter-rotation; therefore better frontal area.. and feet out of the wind. I am not quite so sure about the concentric swingarm sprocket but there you go...

Bravo Mr Crysz; now maybe the majors will try something (anything?) new...

Neil

 

[finman]

Take a look at this one, 2 wheel drive and 2 wheel steer.

http://home.mira.net/~iwd/2x2x2/intro.html

BTW The concentric sprocket swingarm deal has been out since the seventies, a British company called Spondon Engineering had that for public use utilising the Kawasaki straight 4 900's and 1000's

 

[magnograil]

Mr. Csysz' team had some good ideas and reused old ones. Counter rotating cranks have been around on the square and V4 two strokes for a long time. Not much point in making the bike narrower than the rider though. Looks like the riders feet will cook with the radiator exhausts pointed at them.
The concentric swingarm sprocket was done long ago as an idler for wider tyres than the engine normally allowed. The only detraction of its use here is the chain cannot be used to pull the rear wheel down into the road while accellerating giving less traction. Ducati has had a big problem with their swingarm bolted through the engine cases design.
The external front spring/damper unfortunately increases the metal required to enclose it instead of serving double duty.

 

[finman]

I believed that the drive chain sprocket concentricity with the swing arm pivot was to keep the tension in the chain consistant regardless of the position on the rear suspension.
I see little point in utilising the chain to "pull" the rear wheel down when to suspension could absorb the force and surely the drive chain is rotating in the wrong direction to do this.

 

[spalders]

Chain pull is designed into all bikes. Stand alongside a dyno and watch the rear of the bike rise as the rider accelerates.

Racing bikes have adjustable height swingarm pivots to allow this effect to be tuned according to rider feel during a race meeting.

The effect is like having a broken twig (the swingarm and pivot) and putting an elastic band round it (the chain), if the swingarm is straight there is no effect. if the swingarm is bent then the band will try to bend it more. Typical swingarms pivot centres are 7mm to 12mm higher than the output shaft centre

 

[finman]

Spalders, I stand corrected. I recall Spondons sales blurb during the early eighties regarding the concentric sprocket deal. It appealed to me then but maybe things have moved forward.

 

[spalders]

Bimota did a chassis as well; what is surprising is the number of racebikes that dont allow SA pivot adjustment. Honda Racing cut and reweld the chassis of the RC211V at least once a year to use a diferent position......

Now, what do you think of the Czysz front end..?

 

[finman]

Maybe wieght is an issue I know the big boys are mega wieght concious. We build radiators and oil coolers for F1 teams and I can't believe what they expect! But I would have thought some amount of adjustability would be prudent.

Must admit, I havn't come across the Czysz front end, got any links. This is getting interesting.

 

[spalders]

Yup it is, have a look at

http://www.motoczysz.com

Good stuff..but I suspect there is rather a large gulf between some brilliant design thnking and actually racing Motogp.....

 

[magnograil]

Too bad they did not leap frog everybody and build an electronically variable damper. There exist rheonomic fluids that when used with magnetic coils, the flow restriction can be changed dynamically. They already have suspension position sensors. All they have to do is add the software and driver circuits. Then they do not have to compromise between the fully loaded and light fuel weights.
The suspension tube does not have to be round since it is not sealing in oil. Even though the track needs to be metal for the hardness, the surrounding shape can be made of anything such as carbon fibre to tailor the side flex.