The TX650 Tracker Concept

beatpoet · Full Member Joined: Jan 05, 2008 Posts: 33

I did my bobber concept over in the bob section; now here's my tracker concept.

Low-weight wheels, anti dive/squat suspension, duolever front, cradle frame, 2:1 'Y' rear-exit exhaust, monoshock rear swing.

Any comments/suggestions?

KYLEPRESTON · Posted: December 30, 2008, 5:29 pm Post subject: Re: The TX650 Tracker Concept

very interesting I would like to see it not so dark to get a little more detail
but I have to ask why?

beatpoet · Full Member Joined: Jan 05, 2008 Posts: 33

It's easier to model when the surface detail is low. The surfaces are easily smoothed, but rendering takes a long time.

Why? Why not. A bike built like this should probably easily outperform any chop job or hardtail. Yet, people still chop.

Even though this is only a fantasy bike, it has the makings of a functional performance cycle. The telelever telometry is probably inaccurate: as it stands the camber would be vertical under heavy braking.

The tires are 16-17" with alloy or carbon fibre rims. With the updated tires, brakes, and alloys I would think that one could at least break even unsprung weight-wise.

The brakes are hinged in order to incorporate a dive sensor, and an anti-squat cylinder is also incorporated into the rear.

A cradle-style frame would probably feel a bit stiffer also.

beatpoet · Full Member Joined: Jan 05, 2008 Posts: 33

from the front suspension wishbone frame mounts a and b.

The distance between the wishbone mounts above the front wheel will be the distance between 2a and 2b at rest.

When stressed, the suspension moves from 1a to 1b.

The angle and distance appear to remain the same assuming the wishbones are of the same length.

Just workin' it out.

beatpoet · Full Member Joined: Jan 05, 2008 Posts: 33

I suppose if I raked the whole thing over 20 degrees, the concept is the same.

beatpoet · Full Member Joined: Jan 05, 2008 Posts: 33

If I make one arm smaller than the other, the smaller arm's angle will change more because more of the circular motion will be traversed for the same distance travelled by X.

Angles a and b are congruis, angle c is the additional portion of the circle that is travelled by the shorter arm. I'm guessing that the ratio of this angle travelled corresponds to the ratio of the arms/ ratio of circle diameter.

beatpoet · Full Member Joined: Jan 05, 2008 Posts: 33

Now I see my mistake - my upper arm is on an extending portion of the arc (pointing down), so the front wheel would push towards the frame when braking. The bottom arm's length from the frame is getting shorter, while the top arm's length is getting longer.

Both arms probably should be near horizontal or pointing slightly upwards when loaded - at least near the same angle.

beatpoet · Full Member Joined: Jan 05, 2008 Posts: 33

OK...

beatpoet · Full Member Joined: Jan 05, 2008 Posts: 33

One More:

xsleo · Posted: December 31, 2008, 4:12 am Post subject: Re: The TX650 Tracker Concept

your front end will work like a girder fork. the arms from the frame to fork will have to be the same lenght. if not you will get a binding in the travel. when it binds something will bend and break.

metalredneck · Full Member Joined: Aug 04, 2008 Posts: 308

Are you going for an unequal length control arm setup like an old car front end, or am I missing something here?

beatpoet · Full Member Joined: Jan 05, 2008 Posts: 33

metalredneck wrote:

Are you going for an unequal length control arm setup like an old car front end, or am I missing something here?

That's exactly what I was going for. I saw BMWs duolever and realized that it was just like an automotive dual wishbone turned sideways. Why not use different variations of auto suspension?

I'm tempted to put a couple of four-wheeler front swingarms on a small bike to test the waters.

beatpoet · Full Member Joined: Jan 05, 2008 Posts: 33

thorshammer · Full Member Joined: Dec 12, 2008 Posts: 58

Hi you can use different length control arms just realize that no matter what you do there is always an effect. I had a book on motorcycle design if I can find it again I pass on the name and ISBN #., it covers all different suspensions and how they interelate. Some heavy reading but it goes with the territory.

metalredneck · Full Member Joined: Aug 04, 2008 Posts: 308

The point unequal-length on cars is to keep camber consistant during suspension travel. Camber is not an issue here, so I'm curious what the advantages are in this situation.

Shannon60 · Posted: January 2, 2009, 11:52 am Post subject: Re: The TX650 Tracker Concept

Umm... rake.

beatpoet · Full Member Joined: Jan 05, 2008 Posts: 33

There are mixed reviews on the BMW duolever suspension.

The bars are not in (nearly) straight-line contact with the road, so some people think that they have no 'feel' to them. Just as many people like them.

BMW has calculated the angles so that the rake never changes, even under heavy brake diving. No more wobbling on the front wheel at a nearly vertical rake under heavy braking.

The second point would be to try to just get the unsprung weight as low as possible. I would think that this setup would at least be break even with forks weight-wise. Look at the size of the the duolever's shock.

The shock sits in the interior of the pivot points for the levers, so a couple inches of shock travel further down the lever equals more than twice that on the wheel axis - less spring/damper weight.

Less spring/damp weight, no change in camber under diving = probably a good thing. For those who say the suspension lacks 'feel' I propose mounting the bars somewhere near the pivot point on the actual top suspension wishbone. That would give some feel back without adding a lot of weight to the suspension.

metalredneck · Full Member Joined: Aug 04, 2008 Posts: 308

I'm planning to build an Akira bike starting this spring, so keep me posted on this setup, it looks like it may fit my needs. Cheers.

Tomterrific · Posted: January 2, 2009, 5:28 pm Post subject: Re: The TX650 Tracker Concept

Never ever call the BMW front suspension a duolever. The Englishman that invented this suspension is named Hossack and the suspension design is termed Hossack. BMW stole his design since the patent had expired and chose to give the man no credit. The Hossack was well reviewed in the lay motorcycle press many years ago with the inventor winning many club races with his prototype.

Obviously I believe Hossack should be given credit for his invention.

Tony Foale wrote the book on frame and suspension design back in the 80's. Best get this book and read it. I've got an original copy and it is the best eye opener possible. In the book Mr. Foale covers the dificulties the ELF GP bike had with it's hub steering design (late 70's early 80's). They ended up removing most of the natural anti dive of the suspension. The riders used the dive of the suspension to intuitively judge the rate of decent.

If all you want is anti dive for the brakes there is an easy and clever way to get it with the standard forks. The caliper mount must be free turning on the axle, rear mounted. A compression sturdy bar is run from the outer caliper mount to the lower triple tree (fork clamp) to position the caliper. Any braking that would dive the front end is compensated by the free turning caliper mount pushing upward from the drag on the turning rotor.

Tom Graham

jayel · Posted: January 2, 2009, 9:15 pm Post subject: Re: The TX650 Tracker Concept

Tomterrific wrote:

Obviously I believe Hossack should be given credit for his invention.
Tom Graham

thoses schweinhunds

pumps · Posted: January 2, 2009, 11:22 pm Post subject: Re: The TX650 Tracker Concept

I was moved to read about Mr. Hossack from his site.

www.hossack-design.co....ge.php?p=1

yamaman · Posted: January 3, 2009, 4:37 am Post subject: Re: The TX650 Tracker Concept

this is a front end, made in a old stable in John Brittens back yard, out of then untried carbon fibre, worked pretty good for him! (the first one snapped in half, after that he had it sussed)

www.diseno-art.com/enc...V1000.html

pumps · Posted: January 3, 2009, 8:34 am Post subject: Re: The TX650 Tracker Concept

Tom Terrific: Is the Tony Foale book
otorcycle Handling and Chassis Design: the art and science
or
otorcycle Chassis Design: The Theory and Practice

I'm guessing #2 as the pub. date I saw was Nov. 84'.Might be an interesting read. They are not cheap are they?

beatpoet · Full Member Joined: Jan 05, 2008 Posts: 33

Tomterrific wrote:

If all you want is anti dive for the brakes there is an easy and clever way to get it with the standard forks. The caliper mount must be free turning on the axle, rear mounted. A compression sturdy bar is run from the outer caliper mount to the lower triple tree (fork clamp) to position the caliper. Any braking that would dive the front end is compensated by the free turning caliper mount pushing upward from the drag on the turning rotor.

Tom Graham

I can't for certain identify this bike: I was searching for the P&M F1 Kawasaki. Same front suspension though- you can just make out the two linkages attached to the hinged front calipers.

What Happened to 650rider.com?

Yamaha xs650