axle paths
- Thread starter _*sTiTcHeS*_
- Start date
Moto GP is not relavant at all to DH bikes in this discussion.
Moto GP bikes are most of the time on flat realtivly smooth surfaces and are either on the power or engine braking.
Your credibility was never in doubt.You've got a lot of people having a blast on bikes you designed.
We're talking DH and traction. DH is,well downhill,on an angle most of the time,this transferres your centre of traction forward and therefore lessens the effect of rear wheel travel direction.As can be seen in BCDs drawing.
A high pivot with an idler or equivalent,and a floating brake,will be more active under any circumastances than a Sunday,it can have anti squat dialled in with chain line(vertical plane) if desired.
Shock set up and amount of linkages is irrelivant also here,so is tyre pressures,we're focussing on wheel paths and their pros and cons,nothing else.
DW please post up some facts from test results that you claim to have done. Also please post up the Sundays wheel path.
I want to learn,I want my ideas proven wrong,I need straight up facts.
Moto GP bikes are most of the time on flat realtivly smooth surfaces and are either on the power or engine braking.
Your credibility was never in doubt.You've got a lot of people having a blast on bikes you designed.
We're talking DH and traction. DH is,well downhill,on an angle most of the time,this transferres your centre of traction forward and therefore lessens the effect of rear wheel travel direction.As can be seen in BCDs drawing.
A high pivot with an idler or equivalent,and a floating brake,will be more active under any circumastances than a Sunday,it can have anti squat dialled in with chain line(vertical plane) if desired.
Shock set up and amount of linkages is irrelivant also here,so is tyre pressures,we're focussing on wheel paths and their pros and cons,nothing else.
DW please post up some facts from test results that you claim to have done. Also please post up the Sundays wheel path.
I want to learn,I want my ideas proven wrong,I need straight up facts.
^i am pretty sure it applies in moto gp too, just because the wheel doesn't visibly leave the ground like how the dh bike does when hitting a bump doesn't mean it doesn't apply.
dw- does this center of traction in any way help explain why people say a bike like the tuner dhr corners well? the center of traction doesn't move much? and not so much because the wheel base shrinks?
dw- does this center of traction in any way help explain why people say a bike like the tuner dhr corners well? the center of traction doesn't move much? and not so much because the wheel base shrinks?
exactlly short wb bikes are quicker and turn easier.
you are right.
I wasn't implying it would or wouldn't work for moto's,I was saying it is errelivant and proves nothing really,and was not worth mentioning.For the sake of it,Moto GP bikes don't have high pivots anyway,so the centre moving as in the high pivot case is not the same.Please don't derail this thread and open another avenue for discussion that will avoid the topic,that was my point. Please show the Sundays axle path DW,and show evidence of better performance over a high pivot.
That's fantastic, I still don't see how you working with a dozen world-championship-winning cars, bikes and aeroplanes gives you the ability to read the minds of every other person on earth!
For what it's worth, I personally have discussed axle paths, cornering traction, and centre of mass balance (as you refer to it, centre of traction) with Aaron of Lahar bikes. I don't know that either of us fully understand it (to be fair, I haven't really spent that much time thinking about it let alone mapping it out with real numbers), but for you to come out and say that "certainly" nobody else in the bike industry even cares about this information IS arrogant. You MIGHT be right that nobody understands it, but you sure as hell can't prove that one and IMO it's a blemish on your usually high standard of PR to claim otherwise.
Also, I really disagree about your comment regarding axle paths and bump compliance (maybe not really small bumps, like 1" high or less). Ride a low-pivot bike and a high-pivot bike back to back through rough terrain, especially anything with sharp hits, and there is a VERY noticeable difference. For example, a Turner DHR is constantly hanging up on anything sharp, yet jump on a Balfa or a Lahar and it's incredible what the limit of "stuff I can ride straight through without a problem" changes to. I am well aware that the wheel is a lever in and of itself - even a hardtail will roll/bounce over certain size bumps before it hangs up badly. However, when considering how the displacement of a bump is going to be transmitted to the suspension, there are two components relative to the wheel: radial and tangential. Tangential components obviously don't try to compress the suspension (they would simply attempt to spin the wheel up to whatever speed is necessary to keep that point on the wheel at the same point on the ground, which I'm going to go out on a limb and claim is the same as your rolling speed), but the radial component multiplied by the cosine of the angle between that radius and the axle path determines how much force/displacement will be attempting to compress the suspension (with resistance only from friction/spring/damper), and how much of it will be a purely deceleratory ("hangup") force acting perpendicular to the direction of suspension movement.
Interested in hearing your thoughts... since apparently you can hear mine
Also, my understanding of centre of traction: bike sliding or cornering. Each wheel has a certain tractive force vector (though from my understanding this would really be called a "grip" force? I thought traction was generally referred to as longitudinal acceleration... doesn't matter anyway) which have a resultant force applied between the two contact patches, at the point you call the CT. The position of this force relative to the centre of mass can provide either no yaw moment (two wheel slide perhaps) if the centre of mass is longitudinally in the same position as the CT, or if there is an offset, the inertia of the CoM will not be "exactly" balanced by the tractive force resultant at the CT and a yaw moment will result (since you now have effectively a couple moment). Your belief is that the distance between CT and CoM should remain as constant as possible in order for the yaw moment not to vary too much, because that would create more disturbances for the rider to deal with.
Am I correct with this understanding or am I missing something?
Am I correct with this understanding or am I missing something?
I think you're correct up to this point - my take on what DW is saying is that the CT should not move around too much, too quickly. The CoM will change quite a bit as the rider moves, but the variation in position of the CT should be at a rate the rider can respond to/predict.
8" forks throw the geometry out and the center of traction very fast,especially if braking in an unforseen bumpy corner,yet we manage to predict the worst case scenario and be ready to respond to it.
Does a sundays suspension work differently over the same bump if pedalling,braking or neither? Wouldn't this have a large effect in comparisson to a riders performance on a high single pivot? Especially one with fixed gears at both ends of the suspension and a floater.
Does a sundays suspension work differently over the same bump if pedalling,braking or neither? Wouldn't this have a large effect in comparisson to a riders performance on a high single pivot? Especially one with fixed gears at both ends of the suspension and a floater.
dave w: what does your axle path look like on the sunday?
if my body rode a high SP bike for a month, would it not get used to the CT movements in the bumpy corners, and landings, and stuff?
and howcome yeti is boasting rear wheel axle paths yet theirs is vertical? what a bunch of goons!
if my body rode a high SP bike for a month, would it not get used to the CT movements in the bumpy corners, and landings, and stuff?
and howcome yeti is boasting rear wheel axle paths yet theirs is vertical? what a bunch of goons!
I think his point is that if the CT moves a lot when the suspension moves, rapid suspension movement from bump absorption will result in a CT movement that is too fast for any human to be able to react to.
Dunno where DW went though, maybe I scared him off by calling him arrogant... still waiting for his input on this!
of course the pertinent question is - is the amount of ct movement really detrimental (or discernible, for that matter). there's no question a high pivot feels subjectively different than a low in corners, however (using my state of the art built in seat of the pants data acquisition system) i don't feel cornering speed suffers comparatively (actually, the high pivot levels nasty braking bumps better, so entrance speed may be higher in some circumstances).
I would imagine he has been celebrating thanksgiving with Family. And not sure if it answers some of you questions about axle paths and such but have you visited www.dw-link.com ?
haha yes, I've read the full DW-link site, as well as pretty much everything DW has ever said regarding suspension on this site (as well as a bit on other sites such as MTBR). And I'm not seriously having a go at him, I just thought one comment he made was unjustified and pointed that out. I'm not part of the OMG LETS KILL DAVE WEAGLE club just yet 
xy9ine: That's been my experience too. In fact one of the best drift photos I've ever seen was of Miles Mead on a BB7, at the bottom of the Mt Buller fireroad (ftr top speeds recorded down there by yours truly are about 65km/h... and not everyone is braking hard for the corner). Not that that really proves anything though.
xy9ine: That's been my experience too. In fact one of the best drift photos I've ever seen was of Miles Mead on a BB7, at the bottom of the Mt Buller fireroad (ftr top speeds recorded down there by yours truly are about 65km/h... and not everyone is braking hard for the corner). Not that that really proves anything though.
FINALLY...found the thread that started a thousand YAW jokes on Ridemonkey over the years.
Hey DW, did that moto design ever become a reality?
Hey DW, did that moto design ever become a reality?
finally ventured back over from the vital forums i see
Someone reported here that it did not. Vaguely recall seeing it in the background of his workshop a decade+ ago.
Anything happens on vital forums? Last time I checked it was like a mix of mtbr and pb.
must have been a long time ago. team rumors dude.
So is there anything interesting? Or is it just dead? My brain is slow today due to zoom overexposure
their team rumors thread is pretty much the go one in the offseason. they have a thread on new tech of basically spy shots. stuff pops up there before it shows up on pb or anywhere else. not hugely active but the content is generally good.
Judging by how insightful, relevant, and hilarious this necrobump was... no.
Sup yaw?