Kinematics

Linkage is like a game of whack-a-mole at times and the inability to lock in the dimensions of different components is frustrating. If you're designing a bike has a flip chip, you will have to have a working CAD model first and plug in the numbers from that CAD model into Linkage to see how it changes. 

This, yes. 

You can lock in only the wheel travel and let the shock stroke be derived from the current pivot positions. So when you first make a model it might shownup as 220 x 70mm so you know there's some errors in there. If you want to just look at AS and AR you can just ignore that to begin with. It's one of the ways we normally check if a model is accurate enough - if the points and wheel travel entered give a shock stroke within .5mm of true then it will be good enough to use.

I seem to remember the i-track software being intended for defining the kinematics you wanted and would generate the pivot points for you

Recent article from Pinkbike on an interesting suspension design. Anyone able to further distill the explanation Chris is giving around anti squat and IC. I can understand why this design would have higher antisquat values without the chain tension due to IC locations, but I’m getting lost in his explanations after that. I’m genuinely curious as it seems like this design could have some real merit in the right applications. 

https://www.pinkbike.com/news/first-ride-ljb-suspension-all-of-the-pivo…

Yeah I don't know where to even start with this 🙃

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stoicbear (4 hours ago)
@G-Sport: I'm not surprised what I'm describing sounds like nonsense to you. You have to abandon what you know about mountain bike suspension design and kinematic theory to understand what is going on. You have to do a statics analysis, and determine the Moment about the IC due to the chain tension force vectors when the rear triangle rotates about the front triangle, and when the front triangle rotates about the rear triangle. What you will find is when the rear wheel rotates about the front triangle, chain tension has almost no leverage on the front triangle, which is why chain tension does not affect rear suspension movement. If you determine the moment about the IC when the front triangle rotates about the rear triangle, there is very little leverage to lift the rider.

When the rear suspension compresses, other designs deal with chain growth by rotating the pedals backward or stiffening the suspension. The other thing that can happen is the rear wheel can rotate forward. All other bikes have enough leverage between the front and rear triangles to have some sort of interference of suspension action due to chain tension (pedal kickback or stiffening the suspension). (That's why high pivot bikes exist; they reduce the amount of chain tension and allow the rear suspension to move more freely.)

With my bikes, your leg/foot has more leverage on the cranks than there is to rotate the pedals backward or stiffen the suspension. It is easier to push the bike forward by rotating the rear wheel forward than it is to rotate the cranks backward or stiffen the suspension.

My bikes are designed with the correct theory for mountain bike suspension. Anti-squat is similar to "everything revolves around the earth". It holds up for general/typical observation, but falls apart in the details, just like early astronomy. Using Anti-squat theory is why people say different bike suspension designs are why there are differences in suspension performance. When you analyze what's going on with mountain bike suspension using Statics, it's like the "the heliocentric theory of stellar motion", where the earth rotates about it's axis and orbits around the sun. It explains everything properly. Using Statics for mountain bike suspension design explains everything about every single suspension design. It's all about leverage.

For example, Ellsworth bikes put the IC fairly far forward of the suspension linkage. Putting the IC far in front of the linkage results in less leverage to rotate the rear suspension, making it less impacted by chain tension. You can do similar analysis for every single rear suspension design, including 6-bar designs, and you will find that every bike design that pedals well and has minimal interference from chain tension also has low leverage to rotate the rear suspension due to chain tension. Every. Single. One.

..............

My first thought when reading though that article and the comments was "okay then, help me understand".  For instance if you think traditional AS and AR concepts are meaningless, show some alternatives that convey what you're trying to say.

I'm just some guy, but also it isn't quantum mechanics.  It should be easy to explain to anyone who isn't an idiot, surely.

If everything we think we know is wrong, and he's redefining suspension kinematics, you know what would be super cool? A graph. Or a force diagram. You know, what you learn in the first year of an engineering program. Please show us a graphical representation of why everything we think we know is wrong.

I especially loved the "it's all in linkage! Look at these graphs!" Yet they didn't post the kickback graphs in particular despite the no kickback claims.

He's so full of shit.

I’m intrigued by the design and concept. I still can’t wrap my head around it, but I do respect Matt Beer as a rider and tester and he says that it does have merit.   

The comments section on the article is heating up though. “ Sorry Chris- This design infringes on the CBF patent. You won't be able to sell it in the US. I bet it rides amazing though. But if your Center of Curvature is on the chainring- It is a CBF.” -post by Chris Canfield 

There's drama in the World of Kinematics and I've been missing it? Man, I hope to become a 6-Bar snake oil salesman too one day.

“Kinematic Beef” sounds like a high end steakhouse

Can someone break down what’s happening with the linkage in real simple terms? Like why does the dual link version look more like a Horst link? Is the ebike a linkage driven single pivot? 

He was mentioning there is no pedal kickback because it’s easier for the wheel to spin than the pedal to rotate, because leverage. Is there logic to that?

Or an army term for canned beef.

I’m not an engineer, just a fan of outside the box thinking. What catches my ear is the way they say the front moves around the rear or rear moves around the front. Sure it could just be words but I’m not going to discredit the idea, the builder, the product or the test rider without knowing more or trying it.

 As Matt is riding up the hill he says, “it feels like the bike is standing still, but the Suspension is moving underneath me”

After short downhill, Matt says ”chainless effect, sensitive and calm, almost Erie” “ you don’t have the same sort of feedback you expect from a regular full Suspension bike”

 I’m not saying that this will be the world‘s best bike or that it’s perfect. Just totally intriguing to me and love to see this kind of stuff!
 

Sounds a lot like a bike with a lot of sprung mass, like an e-bike with no motor? They didn't mention weight and it looks to be steel or maybe titanium so I am guessing it contains a fair bit of gravity......

apparently pinkbike has all the photos labelled incorrectly. 

apparently pinkbike has all the photos labelled incorrectly. 

Just gonna leave this here.

Figured I'd include something with low AS (giga) as well as high AS (SB160). Chose the yeti to show how pointless it is to drop AS at the end of the travel to limit kickback. What part of the travel are we using when we're smashing over chop again? Oh yeah the bit where it's happening at a consistently high rate. The Pincher is higher but then continues to the moon.

Suspension is all really simple geometric calculations. There's no magic. Dude is doing the equivalent of telling us that triangles have four sides if he says there's a special sauce that he's using statics for to avoid these effects. Not sure how that works. Maybe he means that there's no kickback when the bike is completely static.

Matt Beer can ride a bike but he has said some bafflingly wrong shit in the past when talking about how bikes work. He's not a great resource for technical stuff IMO.

edit: and if you disagree then go and read his "article" about fork offset and compare it to how steering geometry actually works. It's confused and mostly backwards.

The problem is not his design but his explanation of why it works. There's a lot of common things that should always ring alarm bells in any technical discussion and generally indicate that the person making them doesn't understand what's going on.

1) He discredits an established theory that has logical assumptions, is based on basic principles and has been proven through countless designs.

2) He's invented his own language to describe technical concepts.

3) His arguments are not consistent, e.g. he states there is no kickback and then says instead the chain force rotates the wheel forward.

4) He compares the problem to something completely unrelated (the solar system!).

5) He presents opinions as facts with language that is designed to manipulate, e.g. "every bike design that pedals well and has minimal interference from chain tension also has low leverage to rotate the rear suspension due to chain tension. Every. Single. One."

All that said a lot of good inventions have happened by chance without the inventor understanding why, so it may be that the bikes do ride well. Personally I don't immediately see anything special but suspension kinematics are complex, particularly for sprinting where there is a lot of dynamic movement of the rider and tilting of the bike.

I forgot one:

6) He believes people cannot understand his idea, despite supposedly being based on basic mechanical principles.

To be fair, Matt isn’t trying to explain anything. He’s letting the guy say his own piece and he’s not pushing him on it. But he is riding the bike and comment on its characteristics. As you said, he's good at riding bikes. 

I’m reading the comments from the designer on PB, here’s some more info. The guys brain is working on a differently than mine, so you have to bear with it. Like some amazing artists I’ve met, they are just thinking outside of the box. Until proven wrong, we should happy he is doing what he’s doing. It’s always much easier to say “what’s wrong” with what someone is doing, rather than patting him on the back for what he did right or tried to do….

“ What happens with all of my bikes with regards to chain growth is different than other bikes. Instead of pedal kickback or stiffening the rear suspension, my designs force the rear wheel to rotate forwards. It's what gives the bikes amazing traction, because the rear wheel's contact patch stays in the static friction regime. These bikes find traction other bikes can't.”

“When the rear suspension compresses, other designs deal with chain growth by rotating the pedals backward or stiffening the suspension. The other thing that can happen is the rear wheel can rotate forward. All other bikes have enough leverage between the front and rear triangles to have some sort of interference of suspension action due to chain tension (pedal kickback or stiffening the suspension). (That's why high pivot bikes exist; they reduce the amount of chain tension and allow the rear suspension to move more freely.) 

With my bikes, your leg/foot has more leverage on the cranks than there is to rotate the pedals backward or stiffen the suspension. It is easier to push the bike forward by rotating the rear wheel forward than it is to rotate the cranks backward or stiffen the suspension.”

 

Everyone can take what they want from product tests and reviews. I always suggest finding test riders or editors that you respect or take little bits from all of them and make your choices on what you feel fits your style.

I'm sorry, I can't help it:

An impact that "forces the rear wheel to rotate forwards" is the same thing as an impact that "deals with chain growth by rotating the pedals backward or stiffening the suspension." 

In the above diagram, the red force is the impact at the rear wheel. As the rear wheel is being held back by the red impact force, the rear center is growing, which is creating chain tension, which also stiffens the suspension. The suspension can't compress and absorb the bump until the increasing chain tension is relieved, and the chain tension can only be relieved in one of two ways: either the rear wheel has to roll forward (black arrow), or the cranks have to rotate back (green arrow).

If your wheel wheel is stuck in a hole, like a braking bump or a series of ugly rocks, there's too much grip for your rear wheel to rotate forwards. It would have to slip, which isn't happening, because again the tire is pinned in a trap. So your cranks have to move backwards to relieve chain tension in the top half of the drivetrain enough for the suspension to compress more and go over the bump. [Because this is a discussion specifically about the pedal kickback values of the new Pinscher bike, I'm talking about impacts that are occurring so fast that the rear hub is engaging and locking the cassette and freehub, so the chain tension can't be relieved by the cassette rotating forward independent of the wheel (i.e. freewheeling) which would allow the derailleur cage to allow chain growth on the top and bottom halves of the drivetrain]. 

I'm not judging his suspension design at all, in part because there hasn't been enough information provided to make an educated guesstimate, but the way he's describing things is frustrating. When Chris from Pinscher says "other designs deal with chain growth by rotating the pedals backward or stiffening the suspension" but "my designs force the rear wheel to rotate forwards," it's like he's saying "My soup isn't hot. Its molecules are just highly active." 

Matt said there was a bigger difference in the dual link design and that was the one that had the “Erie interesting feeling” he said the Horst link did have more noise and feedback.

Do you think the lower link would help give this rotation feeling and reduce the pedal feedback?

I have not yet had a chance to open up Linkage and look at his design and compare what's happening. It's an interesting design and concept. The way I read it is that he's found a linkage layout that redirects traditional chain tension that is resolved at the cranks and moved it to his forward rocker link. The force is going to resolve in the place of least leverage, his layout the cranks are a higher leverage point than his forward lower link. 

Need to dig futher into this comment of his. 

" When looking at how a rear suspension performs WRT chain tension in Statics, there are two common Regimes, which I call "Balance of Torque" and "Mono Torque". A third is "Pincher". There's a fourth, but I only know of one bike that is in that Regime.

A Balance of Torque rear suspension occurs when the IC is located between the two pivots on the front triangle (in the vertical direction), and chain tension puts both pivots on the front triangle in compression. This regime results in two First Class Levers in series, which usually results in a multiplication of the chain tension force vector. The Balance of Torque regime is becoming scarce, and was common when Horst Link bikes had the Horst Link pivot below the rear axle. The further the Horst Link pivot is below the rear axle, the more the chain tension force vector acts through the upper pivot on the frame.

A Mono Torque rear suspension occurs when the IC is located at the same elevation or lower than the lower pivot on the front triangle. Chain tension puts the lower pivot on the front triangle in compression, and the upper pivot in tension. This is epitomized by the DW-Link suspension design. (Luke Beal of leveloneengineering.com designed the first Horst Link Transition Patrol with the Horst Link pivot close in elevation to the rear axle, creating the first popular Mono Torque Horst Link bike.) A Mono Torque bike has less leverage between the front and rear triangles compared to almost all Balance of Torque regime bikes.

A suspension design in the Pincher Regime puts both pivots on the front triangle in compression due to chain tension, but the IC is located at the same elevation or above the pivots on the front triangle. This is how all my bikes are designed, and the Pincer regime has the lowest leverage between the front and rear triangles. The Norco Range is a Pincher design, as well as their new downhill bike. Another Pincher bike design is the variation of Dave Weagle's Orion suspension design as used by eskercycles.com. However, my Pincher designs are the lowest leverage configuration (because the front triangle (Frame Link) is over center to chain tension when the rear wheel rotates about the front triangle, resulting in the best suspension performance."