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DW Split Pivot Suspension System

16K views 119 replies 35 participants last post by  rick watts 
#1 · (Edited)
Just saw this posted up on Pinkbike, a new DW suspension ...

http://www.pinkbike.com/news/2007-Dave-Weagle-launches-new-suspension-system-SPLIT-PIVOT.html or right to the Dave's new site: www.split-pivot.com

Not sure what this will do to the existing DW Link bikes or whether it will be a next-gen type suspension linkage. I wonder if this linkage system will be picked up by Iron Horse or other bike mftrs...

Perhaps those with the engineering knowledge can post up their thoughts.

Check it out.

Hey Dave
I am available to test ride some prototypes, as would anyone who has been on any of the DW-Link bikes.
 
#52 ·
TacoMan said:
Getting a patent and having it hold up in court are two different things. Examiners do not know everything about everything, but the two parties in court will know more about the invention in question.
Ding ding ding...we have a winner!

Moral of the story, ill gotten patents are no good. Be honest with the PTO and you will most likely have an iron clad patent when all is said and done. No sense in going to court just to loose. Set-up your defense and offense foundation correctly and it'll be fun squashing your opponents in court.
 
#54 ·
derby said:
So in conclusion, IC ahead of the wheelbase above ground is bad geometry for bike handling and reduces braking traction.
Just like ICT... :yesnod:

derby said:
IC always within the wheelbase, above the ground, and moving rearward during bump compression is far better, which complements bump compliance and traction.
Like "true" FSR, DW, Maestro, and others.

When I went from a single pivot to my true FSR, I could clearly feel this effect... I felt like going over the bars and had to add a bit of compression damping to the fork.

I don't even what to think how an ICT would feel like in braking on a steep! :eek::nono:
 
#55 ·
SCUBAPRO said:
Ding ding ding...we have a winner!

Moral of the story, ill gotten patents are no good. Be honest with the PTO and you will most likely have an iron clad patent when all is said and done. No sense in going to court just to loose. Set-up your defense and offense foundation correctly and it'll be fun squashing your opponents in court.
Exactly, this is the very bottom line here. I expect to have a full utility patent covering the Split-Pivot design in the future, and I expect to help design bikes using the split-pivot technology so that more riders can get out and have fun.

Dave
 
#56 ·
_dw said:
Exactly, this is the very bottom line here. I expect to have a full utility patent covering the Split-Pivot design in the future, and I expect to help design bikes using the split-pivot technology so that more riders can get out and have fun.

Dave
Sounds like you have good counsel working for you. :thumbsup: Good luck with getting the Patents.
 
#57 ·
Quote:
Originally Posted by derby
So in conclusion, IC ahead of the wheelbase above ground is bad geometry for bike handling and reduces braking traction.


Just like ICT...



Quote:
Originally Posted by derby
IC always within the wheelbase, above the ground, and moving rearward during bump compression is far better, which complements bump compliance and traction.


Like "true" FSR, DW, Maestro, and others.

When I went from a single pivot to my true FSR, I could clearly feel this effect... I felt like going over the bars and had to add a bit of compression damping to the fork.

I don't even what to think how an ICT would feel like in braking on a steep!
__________________

Yes, anti-dive is rather benign near sag with the current ICT having a floating brake focus point (IC) very far in front of the bike, probably less than 50% anti-dive allowing much inertia induced rear extension and exaggerated fork dive. Bump hits reduce the mild anti-dive to near nothing and the dynamic may actually launch the rider forward, resisting deeper bump compression while braking.

My experience riding ICT is limited to a few of the early and mid model Truths and ID. And I found them so poor handling compared to every other bike I've ridden, that I have had no desire to waste my time trying the even more awkward handling geometry and further devolution from FSR in later model versions.

I found from riding that FSR, Horst link, and especially the dw-Link and copies such as Maestro are much better handling and braking. The anti-dive geometry is much more bump complementary and stable handling. Monopivots are better handling than ICT too, braking is more predictable and consistent, with far less instability.
 
#59 ·
[quote='size]i was curious dave if you could chime in about the following explanations from trek regarding their ABP and full floater setup and their comparison to dw link, fsr and vpp...[/quote]

I've read this, and its obvious that the person who wrote this piece has a good deal to learn about anti squat, wheel rates, how they tie in, and requirements for bikes.

Their graph for the mojo leverage rate curve is inaccurate, and their conclusion for how the bikes is obviously based on a guess rather than actual data. One ride on a Mojo proves their discussion wrong.

A major underlying issue is that their bike design is still stuck using an obsolete single pivot location that requires additional spring rate and damping early travel to mask poor acceleration performance. dw-link doesn't suffer from this issue, and therefore can use lighter springing for a more compliant ride without power loss. This results in more comfort, more traction, and more efficiency for the dw-link versus the systems described.

Dave
 
#61 ·
_dw said:
I've read this, and its obvious that the person who wrote this piece has a good deal to learn about anti squat, wheel rates, how they tie in, and requirements for bikes.

Their graph for the mojo leverage rate curve is inaccurate, and their conclusion for how the bikes is obviously based on a guess rather than actual data. One ride on a Mojo proves their discussion wrong.

A major underlying issue is that their bike design is still stuck using an obsolete single pivot location that requires additional spring rate and damping early travel to mask poor acceleration performance. dw-link doesn't suffer from this issue, and therefore can use lighter springing for a more compliant ride without power loss. This results in more comfort, more traction, and more efficiency for the dw-link versus the systems described.

Dave
Yeah, sounds like marketing bogus to me...

This quote is laughable...

Dave, I know you may not answer this question for obvious reasons... But I think the Trek floater is covered by one of your patents, especially if used in jointly with the Split Pivot??

At any rate, if that's the case, I hope you can get them.

Oh, and congrats on your alliance with Chris!!! I'll be looking forwards to get one of those bikes! :thumbsup:
 
#62 ·
Warp said:
Yeah, sounds like marketing bogus to me...

This quote is laughable...

Dave, I know you may not answer this question for obvious reasons... But I think the Trek floater is covered by one of your patents, especially if used in jointly with the Split Pivot??

At any rate, if that's the case, I hope you can get them.

Oh, and congrats on your alliance with Chris!!! I'll be looking forwards to get one of those bikes! :thumbsup:
Hey if Trek wants to subject their own technology to their own theories etc... that's great. I'm totally OK with that.

The second second that people get me involved they are going to get the truth, in this case probably more truth than they bargain for.

Thanks a lot for the kind words about Pivot. I've really enjoyed working with Chris and Kevin, true professionals and great guys. The bikes are going to be sweet, a great mix of Chris' design philosophy and ride requirements and the latest advances in dw-link mixed with Kevin's design flair. I'm excited.
 
#63 ·
_dw said:
I've really enjoyed working with Chris and Kevin, true professionals and great guys. The bikes are going to be sweet, a great mix of Chris' design philosophy and ride requirements and the latest advances in dw-link mixed with Kevin's design flair. I'm excited.
Who's Chris and Kevin?
 
#70 ·
_dw said:
AAHHAHAHAHAHA

I just read the part on ABP. "Contact patch rotational factor"???!!!! That's rich. I love it when people try to rewrite Physics. Damn its so much simpler than that...

wow
"The lower or smaller the amount of (contact patch) rotation, the more active the suspension will be under braking." - Dylan Howes, Trek

http://trekmountain.typepad.com/king/2007/08/abp-explained.html

I think he's equating this to: the closer to parallelogram rear brake geometry (the closer the rear brake's effective brake force center - IC or monopivot - is to infinity), which would produce 0 degrees of "patch rotation"; then the more freely active the suspension is under rear braking. This is the same as Ellsworth brake theory implies. And this may be true if only interested in maximum suspension activity for a soft feel hitting bumps, but not concerned with handling and traction.

But more active rear braking does not produce more traction while braking. In fact very active rear suspension while braking is very unstable due to extending suspension-jacking reaction to bump induced compression (as my models posted above show occurring when the IC or brake force center is outside the wheelbase). Dive and wallow is increased and rear braking traction is reduced compared with more balanced rear brake design. High traction rear braking requires balanced and stable anti-dive with complementary bump angle compliance for high rear braking traction.

The Trek version of split-pivot is not very near the poorly balanced handling range of the lowest "patch rotation amount", parallelogram geometry. The Trek geometry is actually very good, being near but not quite as well balanced as the FSR style of rear braking geometry.

To be honest I'm not sure if the more stable (greater anti-dive) but slightly less active (less wallowing) dw-Link rear braking tire traction is much better than the FSR balance in a straight line over consistently deep bumps. But dw-Link sure brakes overall at least as good in traction as FSR with the same travel, and handles sudden handling change in direction or unexpected bumps and dips even better with even less drama, with less change needed in rider position and brake modulation.
 
#71 · (Edited)
derby said:
After viewing more illustrations in Tony Foale's book, Motorcycle handling and Chassis Design, and modeling some more, adding CM inertia effect, I now at least semi-understand the "anti-dive/pro-dive" analysis of classic Vehicle Dynamics.

My mistake was that I thought braking force and linked mechanical reaction was greater than any other.

Basically under braking there is no force greater than the CM inertia, which can counteract against the lesser brake force mechanical reaction.

So even though the wheel rotation would always jack the frame in extension when IC is outside of the wheelbase as my test models clearly show in all cases, the greater force of the CM's momentum and it's mechanical reaction can counteract the mechanical brake reaction when they are not complementary.

The friction or wheel traction of rear braking is never more than the force of the inertia in relation to the rear wheel contact point. That inertia force counteracts with a greater strength against the mechanical extension of the outside of wheelbase IC. If there was 100% traction with wheel locked the point of the IC is effectively locked momentarily via the frame with the anti-dive line, from rear contact point though the IC "force center". And the frame rotates about the front wheel contact point. So if the CM is higher than the momentary fixed point where the triangulation of the rear wheel contact point, frame and point crossing the front wheelbase line, then their is net compression, flattening the links of anti-dive lines - counteracting the rear wheel and floating brake link's rotation.

I also see that when the IC is forward of the wheelbase and above ground the anti-dive increases when the suspension is compressed by bumps. This would cause reduction in traction due to the inertia of the CM pushing down the rear wheel in the relative decrease in anti-dive (less compression rate) or increase in pro-dive (increased extension rate).

So in conclusion, IC ahead of the wheelbase above ground is bad geometry for bike handling and reduces braking traction. IC always within the wheelbase, above the ground, and moving rearward during bump compression is far better, which complements bump compliance and traction.
And upon further reflection, the anti-dive rate used by classic vehicle dynamics is an average or net compression or extension percent rate. And it is based upon HORIZONTAL input of CM inertia to the frame and suspension on a flat and smooth surface. The motorcycle examples in Tony Foale's "Motorcycle Handling and Chassis Design" all refer to smooth flat paved surface. When anti-dive is aligned at 50% of the CM height above the front wheel patch, near sag, then applying only the rear brake to decelerate will allow extension and increase frame dive (in addition to weight shift induced dive) at a 50% rate less than 0% anti-dive. Only when there is 100% (or greater) alignment of anti-dive, will there be no dive input from rear brake mechanics on a smooth and flat surface.

The dw-Link has roughly 80 - 90% anti-dive rear braking geometry near sag. So very little net frame dive is induced by the mechanical reactions to the horizontal inertia of the CM. The dw-Link is among the most stable along with monopivots in this factor, considering only net horizontal anti-dive effects.

Horst-links, and monopivot floaters such as the Kona Dope or the Trek Fuel's new Split-Pivot type suspension, have lower percent of anti-dive rear braking, roughly 10 - 15% less anti-dive, allowing more noticeable net frame pitch or fork dive input from rear braking.

But in Foale's book, and any other vehicle dynamics literature I have read, I have never seen any frame pitch or dive reactivity calculation due to bump input reaction to the VERTICAL inertia of the CM.

My cardboard model, pictured in my post just above, clearly shows there is frame pitch (extension or compression) reaction depending if the IC is outside or inside the wheelbase from a forward rolling wheel that is braked or locked with the linkage. The inertia of the rear wheel alone to the linkage is very little, but it is also conditioned by traction with the ground. The inertia of the ground is very high. And the higher the rear wheel traction, the closer the closer the rolling wheel's forward rotation reaction with the links and frame approaches a high factor of input.

So when a bump compresses the suspension there become greater than 100% gravity force input to the CM vertical inertia change with the ground, binding the wheel traction and rolling wheel input affecting the frame reactivity. When the wheel becomes unweighted on the backside of a bump or depression, the traction is reduced or lost so that rolling wheel input effect is reduced.

Overall or net horizontal CM inertia anti-dive is important to weight transfer and stability. The bump-hit reactivity is equally if not a greater factor of the ability of anti-dive geometry to be very effective when bumps affect traction.

So on bumpy terrain the placement of the IC outside or within the wheelbase becomes the most important factor to traction and stability. IC well within the wheelbase to produce compressing reaction during bump-induced compression is best to maintain more consistent traction and stability with bump induced vertical CM inertia change.

The more compatible mechanical frame pitch (extension or compression) reaction from wheel rotation inertia is to produce compressing effects when hitting bump faces, in contrast to extending effects which fight the bump induced compression and bind the suspension into hardtail-like bouncing when hitting bump faces. And the bump backside traction is maintained by stored rebound spring reaction from the more bump compatible more deeply compressed spring.

The dw-link IC is always well within the wheelbase moving rearward during bump induced compression for even greater compatibility and stability and traction. And the high compatibility of bump compliance maintains very consistent traction and so complements its high rate of overall anti-dive stability. The high rates of traction and stability enhance direction change and "flickability" while in bumpy and loose terrain.
 
#72 ·
I have a note to add to this topic. I just receieved my new copy of Bike magz and on page 045 there is an ad by Trek describing a new technology call "Active Braking Pivot" ABP. They use the words "rear pivot concentric to the rear axle" Patent Pending. Where does this put our friend DW with his Patent Pending design? Is it a race to see who filed it first? Are they differnet? DW?

I don't need a an engineers answer I just want a straight one please.

:confused:
 
#74 ·
Except the problem is the US patent examiners don't seem to keep track of applications on "first to invent" stuff, so they'll likely award patents within days of one another to both applications. US Patents on obvious inventions are so easy to get as long as you fill out the forms correctly, and pay all your fees on time. That's really the crux of the matter... the fees... the USPTO loves to collect fees and doesn't bother to really investigate patent applications if the checks clear.
 
#75 · (Edited)
DeeEight said:
Except the problem is the US patent examiners don't seem to keep track of applications on "first to invent" stuff, so they'll likely award patents within days of one another to both applications.
You're mixing apples with oranges here. First to invent only comes into play when there is an interference. Otherwise patentability based, in part, on the filing date and prior art, among others.

Awarding a patent on the same exact invention rarely happens but it's not isolated to the US; also happens in EU and the rest of the world too. (BTW, there are mechanisms in place to fix this.) How is an examiner to know about another pending application by another on the same subject matter if both were pending at the same time. This is where the USPTO or any foreign patent office relies on the honesty of the inventor to disclose such info material to patentability of one's invention, if known. Concurrent conception of an invention is very common. People come up with similar ideas all the time.

DeeEight said:
US Patents on obvious inventions are so easy to get as long as you fill out the forms correctly, and pay all your fees on time. That's really the crux of the matter... the fees... the USPTO loves to collect fees and doesn't bother to really investigate patent applications if the checks clear.
LOL, that's very funny!!! Doesn't that statement contradict what you've been saying about the KSR v. Teleflex decision?
 
#76 ·
SCUBAPRO said:
You're mixing apples with oranges here. First to invent only comes into play when there is an interference. Otherwise patentability based, in part, on the filing date and prior art, among others.
And you accuse me of contradicting myself... LOL...
 
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