[LokiLopez]

I do believe some qualities of a bike may not show up in paper. But is definitely the exception and not the rule. Or else you wouldn't need engineers, you would need luck.


Oh, and you actually can't tell everything about a man from the contents of his resume.

 

[ÆX]

What's annoying me is that the discussions are being lodged on a bunch of non-scientific explanations of what people THINK it does as a result of their either having briefly looked at the bike or briefly ridden it. Most of the people involved in the scientific discussion about why the design can't work have only seen a couple of photos, that in reality only imply what is mechanically going on. As such, its merely a bunch of speculations based upon speculations. Hardly scientific, unlike the conversations on tried-and-true designs that have been disected by engineers globally. It the end, the only person with a scientific and engineering background to have seen the bike (other than those involved with Sinister directly) is Zedro, and he's actually supporting most of the claims made. As we know, in math and science, the smallest changes can equate to the most massive changes. Remember that the VPP and DW-link systems went throught literally thousands of minute changes before reaching the market to find the ideal configuration. A millimeter here and a millimeter there can completely change a system. Who do you expect most people to believe. Oh, and I'm not really scared of either math or physics, it's just that you really need to adhere to the scientific method when practicing physics.

i know what you mean.

someone show me the range of axle area it travels in.

thit is what i want to see.

 

[thaflyinfatman]

The point is, so many sit and and blabber on and on about how the thing is going to ride, all the time ignoring the simple and indeniable fact that no matter how much you dissect the frame and pivots nad blah blah, there are some qualities of a bike that WILL NEVER SHOW UP ON PAPER.

For example, Kona leant Dropmachine a Stuff hardtail to try out. By all accounts on paper, the bike stunk. Alivio drivetrain, some ass marzocchi fork, and absolutely nothing spectacular about it. But i swear to god everybody that rode that bike loved it, and it performed better then most of the rest of the hardtails we got in. And nobody could figure out why.

Another good example is the Mountain Cycle 9.5. On paper, that bike is a complete cluster****. 15.75" bb, steep headtube, short TT, and more. It hsoudl ahve ridden like a garbage truck on stilts. But it bloody well railed everything, pedalled like a fiend and one rider here just boosted MASSIVE stuff without any issues at all.

I can understand questioning things around you, but what bugs the hell out of me is that it seems many on here have only ridden bikes on the internet, and can't seem to understand that some things on bikes are just unquantifiable. Some things just are, and you should STFU and just ride it. Or, wait till its available and then ride it.

See my point?

Let me prefix my rebuttal with this statement: learn to read. That includes putting whole sentences, and maybe even paragraphs one day, together to obtain a meaning and a message out of a group of individually defined words.

Nobody is bagging the bike. Nobody has said it'll be a POS. We're trying to make sense of a system that doesn't make sense AT THE MOMENT because the explanations so far have been crap (no offence SuspectDevice). There is obviously SOMETHING that makes a theoretically unrideable bike rideable here, but short of saying "OMG IT HAS A BUMPER" and stuff, nobody has actually pointed out WHY that is, and various people have made incorrect statements as to why it can work (the incorrect part being the WHY, not the fact that it can).

As far as scientific goes, uhh sorry this is what they call science. Dissecting ideas, working out the theory behind the reality, and applying it to an otherwise disprovable hypothesis so that you can PREDICT (yes that's right PREDICT) what something will do. For example, if I make a singlepivot suspension system, will the axle move in a straight line relative to the rest of the frame? HOW DO YOU KNOW, YOU HAVEN'T RIDDEN IT OMG OMG JESUS GET OFF YOUR INTERNET AND STOP MASTURBATING ABOUT YOURSELF BECAUSE YOU'VE NEVER RIDDEN IT SO HOW WOULD YOU KNOW BLAH BLAH. See how ridiculous it sounds?

If the theory doesn't line up with the reality, it's because the theory is wrong (or you're measuring reality with poorly calibrated instruments). At the moment, the 5-bar theory (and trust me, I have modeled this) DOESN'T line up with the reality which is that they've made the bike rideable when it otherwise should not have been. What they've introduced to the system (the bumper somewhere, or geometric constraints caused by two links becoming colinear at some stage, which is a dangerous thing to do) to make it rideable is WHAT WE'RE TRYING TO WORK OUT and it's only tools like you that are getting in the way. Kindly piss off out of this thread because I am genuinely interested in the bike and how it works, if you think I'm just having an e-wank then add me to your ignore list because I just could not give less of a **** about idiots who criticise others over the internet FOR CRITICISING STUFF OVER THE INTERNET.

 

[Smelly]

the links move in opposing directions.

Sure looks to me like they move in the same direction- counterclockwise under compression. Am I missing something?

Question- How often will those little rubbber stoppies have to be replaced? I image they take quite a beating and would wear out sometimes given that they're exposed to massive amounts of dirt. Are they an off the shelf item (ie found in a hardware store), or would someone who owned this bike just buy a sackful from Sinister?

Pretty nifty bike you guys got

 

[no skid marks]

Due to the longer leverage,it appears to me that the top link is the weakest link,so you could picture that sitting on it only and similer style loading(donward thrust) that it will behave like a Stab Primo,with the bennefit of a rearward axle path if a square edged hit is incountered or when the primo links have reached a leverage force that overides the lower links lesser leverage. Is this right flyinfatman as you see it?Just genralising here as there's to many outside variables I've not included. So this would also work in reverse although if you'd hit a square edged hit it that would in effect compress the rear triangle the rear triangle would expand before the bottom link had returned,possibly helping to uinsettle the rear and push the tyre out whilst cornering instead of maintaining the longer wheelbase.
Wait a second,if you hit a square edged obstacle(gutter)wouldn't the bottom link go up pushing the top link up and therfore the rear wheel down???
Is that annother bumper behind the top of the shock???
Ha ha ha,so much fun.

 

[thaflyinfatman]

haha I don't know man, to me it still looks like the wheel can move backwards and forwards without moving the shock. I don't know exactly where the bumper is, where it engages, or how else they've constrained it.

 

[dsotm]

Hmmmm, I'll try an explanation. I do see what you are saying. I think (from the pictures of the fram and drawings) that the way they are keeping that from happening is by having different linkages at each link to keep the compression at each link different. I could be wrong though.
Also, ffman, it might help to post a definition of 2 dof, so everyone is arguing about the existence or nonexitence of the same thing.

 

[binary visions]

haha I don't know man, to me it still looks like the wheel can move backwards and forwards without moving the shock. I don't know exactly where the bumper is, where it engages, or how else they've constrained it.

The bumpers are clearly shown in this post:

http://www.ridemonkey.com/forums/showpost.php?p=2299961&postcount=58

I'm still not sure where it achieves any significant kind of area travel. Still looks to me like it's going to travel mostly in a wheelpath of some kind, with some potential for forward/back movement durings its travel.

 

[bballe336]

haha I don't know man, to me it still looks like the wheel can move backwards and forwards without moving the shock. I don't know exactly where the bumper is, where it engages, or how else they've constrained it.

The bumpers are on the lower link. They engage at the sag point. The bike acts like and rides like a single pivot (the pivot being off of the lower link) until the wheel is pulled back by some sort of square edged hit. Then the bike can use it's "area travel" to absorb this hit before settling back to it's single pivot wheel path.

 

[Shepherdwong]

haha I don't know man, to me it still looks like the wheel can move backwards and forwards without moving the shock. I don't know exactly where the bumper is, where it engages, or how else they've constrained it.

Looks to me like moving the wheel backward will cause compression on the shock through the lower link and possibly a little extension through the upper link.

 

[WheelieMan]

Looks to me like moving the wheel backward will cause compression on the shock through the lower link and possibly a little extension through the upper link.

The upper link cannot extend because of a bumper...

 

[Shepherdwong]

I think the upper link has to extend for the wheel to move back. The bumper eventually stops it, but with the rear wheel into its travel the upper link will be off the bumper until it extends back too far.

 

[WheelieMan]

I think the upper link has to extend for the wheel to move back. The bumper eventually stops it, but with the rear wheel into its travel the upper link will be off the bumper until it extends back too far.

If one link "extended" the shock and one compressed the shock, then there could be free play at topout.

 

[Shepherdwong]

If one link "extended" the shock and one compressed the shock, then there could be free play at topout.

I'm assuming there is more compression than extension on the shock as the wheel travels straight back.

 

[SuspectDevice]

The bumpers are on the lower link. They engage at the sag point. The bike acts like and rides like a single pivot (the pivot being off of the lower link) until the wheel is pulled back by some sort of square edged hit. Then the bike can use it's "area travel" to absorb this hit before settling back to it's single pivot wheel path.

Exactly dude, thanks for putting that more eloquently than my sleep deprived brain has been able to put it recently!

 

[bballe336]

Exactly dude, thanks for putting that more eloquently than my sleep deprived brain has been able to put it recently!

I think it's funny that all the engineers couldn't figure this out...


(kidding)

 

[thaflyinfatman]

Hmmmm, I'll try an explanation. I do see what you are saying. I think (from the pictures of the fram and drawings) that the way they are keeping that from happening is by having different linkages at each link to keep the compression at each link different. I could be wrong though.
Also, ffman, it might help to post a definition of 2 dof, so everyone is arguing about the existence or nonexitence of the same thing.

2 degrees of freedom: the axle can move in any direction within a plane (1 DOF = along a line, 2 DOF = within a plane/area, 3 DOF = within a volume, ie in 3 dimensions). Basically it's the number of orthogonal (perpendicular) directions that the axle can move in from any given point.

 

[thaflyinfatman]

The bumpers are on the lower link. They engage at the sag point. The bike acts like and rides like a single pivot (the pivot being off of the lower link) until the wheel is pulled back by some sort of square edged hit. Then the bike can use it's "area travel" to absorb this hit before settling back to it's single pivot wheel path.

Yeah it's slowly making more sense (cheers for the pics BV, sorry I hadn't read that thread) especially with that top bumper, what I still struggle with is, what makes it settle back against the bumper (after it's hit a rearwards/square edged bump or whatever)? What causes the chainstay/lower link to tend to fold (so that the bumper is engaged) rather than simply wallowing around at the extended point (until you pedal or something)? The seatstay link can only be in compression, you can apply a point load in any direction at the lower link/chainstay pivot, and the moment about the axle applied by the seatstay link line of force looks to be SFA, so it's not gonna be a compressive moment (on the chainstay) generated by the seatstay link. Also, is there a physical topout prevention bumper on/under the lower of the two links?

Zedro, you got any explanation here? Cos it seems that once it takes a hit that moves it off the bumpers (utilising the 2nd degree of freedom) there'd want to be some kind of restoring moment/force that tries to bring the chainstay back against the bumper, I just can't see where it's from. Oh and whilst it's using that 2nd degree of freedom (both bumpers disengaged), I STILL can't see how it will actually move the shock... unless the top link is rotating backwards and hitting the TOP bumper, which then makes it a single DOF again (temporarily)... haha what a headf**k.

 

[dsotm]

2 degrees of freedom: the axle can move in any direction within a plane (1 DOF = along a line, 2 DOF = within a plane/area, 3 DOF = within a volume, ie in 3 dimensions). Basically it's the number of orthogonal (perpendicular) directions that the axle can move in from any given point.

Ok, so with any constraints on the system(other than the spring rate), by that definition, you wouldn't have a 2 dof bike. I see. In that case a true 2 dof bike doesn't sound particularly feasible or desireable. Thanks for clearing that up.

 

[bballe336]

Cos it seems that once it takes a hit that moves it off the bumpers (utilising the 2nd degree of freedom) there'd want to be some kind of restoring moment/force that tries to bring the chainstay back against the bumper, I just can't see where it's from. Oh and whilst it's using that 2nd degree of freedom (both bumpers disengaged), I STILL can't see how it will actually move the shock... unless the top link is rotating backwards and hitting the TOP bumper, which then makes it a single DOF again (temporarily)... haha what a headf**k.

The reason it is pulled back to it's 1DOF wheelpath is fairly simple. The bumper engages at the sag point, after the hit or impact the bike will settle back to it's sag point (as with any suspension design). Therefore you get the single pivot, 1DOF, wheelpath again. And unless there are very close consecutive square edged hits the wheel will settle back to 1DOF.

Also just by vizualizing it you can tell how it compresses the shock while moving rearward in it's 2DOF state. The seatstay is connected to the chainstay and upper link with pivots. So when the wheel is moving rearward the seatstay can "float" so it doesn't actually move the top link at all. If the wheel happened to move upwards while going rearwards (which it always will in this application) it would compress the shock by moving the top link, otherwise the seatstay link is inactive during rearward motion. When the wheel is moved rearwards it pulls the lower link out, and because it's on a pivot it moves in a path which is up and back, which allows the shock to compress. Now I know it seems like if the top link is inactive or neutral during this then the links would just flail around and there would be no damped travel, but you are NEVER going to have a movement that is just rearward. Because to have total compliance with a square edged hit the wheel needs to move up and back. So there is always going to be pressure applied to the uper and lower links on square edged hits so the travel is always damped instead of free travel.

That is my take on the VST system from looking it at, I have not had the chance to ride these bikes nor has the system been explained to me in much detail.

 

[verticult]

wow, thanks for looking in and commenting on the bike. I am not an engineer and can't explain this system clearly enough to satisfy the engineers. I do know this to be fact. We are building prototypes and testing a concept that so far has shown to offer superior performance in several areas important to myself and other enthusiasts.

To answer some questions

We are not even remotely settled on locations of pivots or any other critical dimensions.

This is new and not like any other system. I am excited by that prospect alone, but it also means that the learning curve will be steep and expensive. George Costa of Rennen Design group is going to help Sinister get through the next phases by providing much needed "reality" in the form of engineering and analysis.

If you are interested in this design and want drawings so you can play with it, I would be happy to send you the pivot and stop locations I am using now. Naturally, conditions will exist. Any engineer or pundit with modest skills and the desire can pick it off the photos anyway so what is the difference.

We have begun the patent process and am not releasing any of that information yet.

With all due respect to the other brand represented in this thread, this is not like your design and based on your own comments, you may not fully understand it. Take another look, it's pretty interesting.

 

[no skid marks]

bbale36 I think missed something,when the swingarm moves back the chain stay gets longer and so it pulls down on the seat stay,and the shock pushes up on the top link both making the top link squash into the top bumper.

verticult is there any freeplay point where the suspension is floppy or not sprung or resting on a bumper?

 

[bballe336]

bbale36 I think missed something,when the swingarm moves back the chain stay gets longer and so it pulls down on the seat stay,and the shock pushes up on the top link both making the top link squash into the top bumper.

verticult is there any freeplay point where the suspension is floppy or not sprung or resting on a bumper?

Yeah, I didn't word that right, I think the way I looked at it is wrong. I'm sure it has no significant amount of freeplay. After riding a significant number of Sinisters they all feel amazing and I know that FTW wouldn't allow there to be undamped travel.

 

[jvnixon]

balle has it pretty much right
more interbike sinister here

 

[no skid marks]

So either the Kona style suspension is working or it's resting on one of the bumpers(if the chainstay links being used or not)?
I can't really see the top bumper in that pic but it doesn't appear to be touching,hmmm

 

[SPDR]

Looks like the top bumper is just for top out in this pic

and doesn't effect the motion of anything as the link will always be away from it at the sag point.
I think bballe has it in his description from what I can tell looking at the pics (and we all know how reliable that is - eEngineering at it's best)

Would be interesting to get DW's take on this as I feel it's gonna be one of those designs that works (if it does) just because it does (dumb, if educated, luck) rather than because of hours spent calculating the physics models.

I'd be most interested in how it manuals, cos high pivot bikes (lengthening effective chainstay) are awkward in that respect - in my experience.

G

 

[WheelieMan]

The reason it is pulled back to it's 1DOF wheelpath is fairly simple. The bumper engages at the sag point, after the hit or impact the bike will settle back to it's sag point (as with any suspension design). Therefore you get the single pivot, 1DOF, wheelpath again. And unless there are very close consecutive square edged hits the wheel will settle back to 1DOF.

Also just by vizualizing it you can tell how it compresses the shock while moving rearward in it's 2DOF state. The seatstay is connected to the chainstay and upper link with pivots. So when the wheel is moving rearward the seatstay can "float" so it doesn't actually move the top link at all. If the wheel happened to move upwards while going rearwards (which it always will in this application) it would compress the shock by moving the top link, otherwise the seatstay link is inactive during rearward motion. When the wheel is moved rearwards it pulls the lower link out, and because it's on a pivot it moves in a path which is up and back, which allows the shock to compress. Now I know it seems like if the top link is inactive or neutral during this then the links would just flail around and there would be no damped travel, but you are NEVER going to have a movement that is just rearward. Because to have total compliance with a square edged hit the wheel needs to move up and back. So there is always going to be pressure applied to the uper and lower links on square edged hits so the travel is always damped instead of free travel.

That is my take on the VST system from looking it at, I have not had the chance to ride these bikes nor has the system been explained to me in much detail.

I think your analysis is off. What makes you think the design has a "normal" single-pivot wheelpath, and a "square edge wheelpath"? A 2DoF design with shock actuating links that have anywhere close to the same leverage on the shock(s) will have infinite wheelpaths.

A design can't go back and forth between 1DoF and 2DoF, either it is one or the other.

 

[bballe336]

I think your analysis is off. What makes you think the design has a "normal" single-pivot wheelpath, and a "square edge wheelpath"? A 2DoF design with shock actuating links that have anywhere close to the same leverage on the shock(s) will have infinite wheelpaths.

A design can't go back and forth between 1DoF and 2DoF, either it is one or the other.

Take another look. My analysis is correct for the most part according to SuspectDevice who has ridden this bike as much as anyone else out there. Also there are bumpers that prevent the bike from staying at a true 2 DOF system all the time.

 

[Bicyclist]

It will still ALWAYS be a 2 deg of freedom system, even when acting similar to a 1 deg of freedom system.

 

[no skid marks]

It can use the 1d path(Kona style) then a 2d path(chain stay link).
Either the Kona style suspension is working or it's resting on one of the bumpers(if the chainstay links being used or not),there's no freeplay un sprung travel. Now to work out the chain pull affects and flyingfatmans moment effects,oh and braking effects,and how the shocks dampening will cope and the different leverage ratios that can be put on the shock at any point in it's travel(what a nighmare to dial in). To complex.
BBale36 look at two sides of a triangle,you can't lengthen one and not the other,hence the chainstay lengthens the seat stay must come down. Suspect was refering to your later comment I think not your annalysis. Your comment concludued no undamped travell etc.

 

[thaflyinfatman]

The reason it is pulled back to it's 1DOF wheelpath is fairly simple. The bumper engages at the sag point, after the hit or impact the bike will settle back to it's sag point (as with any suspension design). Therefore you get the single pivot, 1DOF, wheelpath again. And unless there are very close consecutive square edged hits the wheel will settle back to 1DOF.

Also just by vizualizing it you can tell how it compresses the shock while moving rearward in it's 2DOF state. The seatstay is connected to the chainstay and upper link with pivots. So when the wheel is moving rearward the seatstay can "float" so it doesn't actually move the top link at all. If the wheel happened to move upwards while going rearwards (which it always will in this application) it would compress the shock by moving the top link, otherwise the seatstay link is inactive during rearward motion. When the wheel is moved rearwards it pulls the lower link out, and because it's on a pivot it moves in a path which is up and back, which allows the shock to compress. Now I know it seems like if the top link is inactive or neutral during this then the links would just flail around and there would be no damped travel, but you are NEVER going to have a movement that is just rearward. Because to have total compliance with a square edged hit the wheel needs to move up and back. So there is always going to be pressure applied to the uper and lower links on square edged hits so the travel is always damped instead of free travel.

That is my take on the VST system from looking it at, I have not had the chance to ride these bikes nor has the system been explained to me in much detail.

That just says WHAT it will do, not WHY it does it. I understand THAT the bumper engages at the sag point, I just don't get what makes it return to the bumper-engaged boundary of the travel area. As we both agree, there will be a direction in which there is no damping/spring return force (close to being purely rearwards by the look of it), but if the spring can't have any effect along that path, then what DOES make the axle return to the most forward position (other than pedalling forces - I'm talking about when you're coasting).

Frank/Verticult: could you please email me that layout, to gravatomik AT hotmail.com ? Cheers.

 

[thaflyinfatman]

I think your analysis is off. What makes you think the design has a "normal" single-pivot wheelpath, and a "square edge wheelpath"? A 2DoF design with shock actuating links that have anywhere close to the same leverage on the shock(s) will have infinite wheelpaths.

A design can't go back and forth between 1DoF and 2DoF, either it is one or the other.

If the axle is moving along one of the BOUNDARIES of the area (because it is pushed up against that boundary for some reason) then it will have a defined axle path (because obviously the boundary of the travel is defined by lines). When the lower bumper is engaged, I believe this is where the "forward" boundary of the axle travel area is, and what they're saying is that only a rearwards hit will move the axle back off that forward boundary and make use of the 2nd degree of freedom. This part I can deal with, what I don't get is how they make it return to that boundary given that there is obviously a (largely horizontal) direction in which the axle can move, where the shock can't move it forwards or backwards. If the front boundary of the area is a path that is slightly rearwards then maybe the unsprung direction would have a small vertical component (since it's presumably perpendicular, or close to, to that path), and the vertical force on the axle (normal reaction force from the ground) could have a tendency to make use of that vertical component and slide it forwards as well. But if you've already got that rearwards axle path (and it'd have to be fairly significant to have enough of a restoring tendency on the suspension, to move the axle back towards the bumper), then is the 2nd degree of freedom really going to have that big an effect?

 

[bballe336]

Travel is always damped because the upper link has bumpers to stop it from allowing undamped travel. Also my best guess about it settling back to it's 1 DOF wheelpath is that when it returns to it's sag point that's where everything settles.

Also no skid mark- kona style is called a linkage assisted single pivot.

 

[no skid marks]

It returns from chainstay growth(2d travel)because the shock extends whilst pushing on the top bumper,the top bumper is what puts it back to the 1d travel(Kona style,less letters).

 

[thaflyinfatman]

If that top link is fixed in place though (ie pressed against the bumper), it's 1DOF. All links need to be moving to utilise the 2nd degree of freedom, otherwise it only has 4 bars...

 

[no skid marks]

Yes when a whack that will cause both dimensions to act then the shock will be compressed and off both bumpers and the wheels interaction or the leverage ratios will control it's return to a bumper.But yes when the shocks compressed it would appear that there's nothing to control the swingarms dirrection,and I guess therefore temporarily un damped.
I had it and you took it from me flyinfatman,I'm going for beer.

 

[WheelieMan]

If the axle is moving along one of the BOUNDARIES of the area (because it is pushed up against that boundary for some reason) then it will have a defined axle path (because obviously the boundary of the travel is defined by lines). When the lower bumper is engaged, I believe this is where the "forward" boundary of the axle travel area is, and what they're saying is that only a rearwards hit will move the axle back off that forward boundary and make use of the 2nd degree of freedom. This part I can deal with, what I don't get is how they make it return to that boundary given that there is obviously a (largely horizontal) direction in which the axle can move, where the shock can't move it forwards or backwards. If the front boundary of the area is a path that is slightly rearwards then maybe the unsprung direction would have a small vertical component (since it's presumably perpendicular, or close to, to that path), and the vertical force on the axle (normal reaction force from the ground) could have a tendency to make use of that vertical component and slide it forwards as well. But if you've already got that rearwards axle path (and it'd have to be fairly significant to have enough of a restoring tendency on the suspension, to move the axle back towards the bumper), then is the 2nd degree of freedom really going to have that big an effect?

Ok, I think I see what you are saying now. bballe said that the bumper would be engaged at the actual sag position instead of THROUGH the sag. Big difference.

I too would like to view the bike data. email is: papawheelieman at comcast.net

 

[no skid marks]

So if the shock was compressed from a 1D(kona suss)hit(drop off)then before shock rebounded a square(2D)hit then there's no dampening or spring till the top bumper is reached by the top link.Is this correct?

 

[SPDR]

Where does this idea of no damping come from? If the shock is moving there is damping - simple. Surely the only way there can be undamped movement is if the system is able to move to any degree with a rigid body in place of the shock?

I can see that there would be "uncontroled" movement in terms of the axle having no defined path to return on but that's the nature of the system, to say it is undamped is just wrong, isn't it?

 

[no skid marks]

The system seems to have a possible scenario where the suspension with the shock compressed and no bumper being touched can have a breif uncontrolled(no dampening)actuation,bascicaly the damping will only work if a bumper is touched otherwise neither end is in contact with anything. This is just a point I'd like explained both technically (for peace of mind)and from a riders perspective, I'm uncertain with what I say and am just trying to undertand both the logic and the extent of the effects. I'm first to admit,I've been wrong before. I'll shut up now.