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Posted: May 11, 2021 at 9:16 Quote
R-M-R wrote:
But can you model my bump steer and steering ratio?

I am choosing to interpret this as a joke, hahaha, noice.


R-M-R wrote:
That would be true if the links were pre-fabricated and they were being positioned on the plane. For a clean-sheet design, the typical process is to design to Cartesian coordinates and create the links to meet those points. It can happen, though, that a design uses existing or off-the-shelf components, in which case the polar coordinates would be useful. Maybe you could offer either mode.

I think you misunderstand, that do be how it is, in a slightly removed sense. Also, I guess I can clear things up a bit, this tool designs the linkage almost entirely on it's own, the user should not need to be adjusting pivot locations manually.
That being said, what you mentioned about being able to design around existing links is indeed an intended benefit of the system. We evaluated designing an inverted horst suspension à la Darkmatter using the spare chainstay and seatstay that we had from our bike. Doable, not great, but doable.


R-M-R wrote:
The ideal inputs would be:
• Bump or droop
...

Outputs:
• Compliance ratio
• Shock piston speed
...

We'll get working on the bump response, the other inputs are already incorporated or in progress.
I'm not familiar with the term compliance ratio, could you explain it or provide a link to relevant info? My searches have not churned up anything relevant.


R-M-R wrote:
I was rather annoyed when Seb Stott referred to that as a "six bar".

Agree, before posting I had it written as "SiX bAr" but felt the sarcasm was a bit too much. But to his credit, he's just mimicking the language used by Polygon (I leave this as an exercise for the reader to interpret the significance as to the state of journalism). And to Polygon's credit, they at least know that New Zealand exists... somewhere.
(ignore the red circle, the mistakes are everywhere but there)
At least New Zealand is included in this mess.

Posted: May 11, 2021 at 11:19 Quote
Fueniker wrote:
R-M-R wrote:
But can you model my bump steer and steering ratio?

I am choosing to interpret this as a joke, hahaha, noice.

Only somewhat. It's clearly outside the scope of a typical kinematics program. These were particularly tedious challenges when designing that front end.


Fueniker wrote:
I'm not familiar with the term compliance ratio, could you explain it or provide a link to relevant info? My searches have not churned up anything relevant.

The alignment between bump force vector and axle path. Perfect alignment would be 100%; orthogonal movement would be 0%.

Posted: May 14, 2021 at 22:54 Quote
Damn, you guys are waaaaay over my head. I have to learn more about this from the ground up so my head doesn't explode.

Heres what I know:

1):Bottlerocket pedal okay.

2):Newer bikes pedal better.

3):No like how new-to-me Old DH/Freeride bike pedal? firmer spring.

If you guys don't mind, I would eventually like to ask you questions about supension layouts either here or in a more appropriate thread and learn about horst/single/4-bar6-bar (etcetera...) links/suspension.

If I get enough info, I would like to start writing blog posts with everything I have learned in a way confused Noobs like me will hopefully understand, and all in one place instead of running all over the internet to find the info.

Funnily enough, I unerstand why the virtual pivot point works but everything else I can't understand. I get why chain growth can limit things, and can kind of see how a high pivot helps, and damn, hardtails are so simple...

Thanks!

Posted: May 14, 2021 at 23:06 Quote
There are lots of good textbooks that cover these topics for automotive design and several good online resources for bikes. Please start with the following resources:

Andre Santos on YouTube
Hugh McLeay on YouTube
Hugh's website

Posted: May 14, 2021 at 23:09 Quote
R-M-R wrote:
There are lots of good textbooks that cover these topics for automotive design and several good online resources for bikes. Please start with the following resources:

Andre Santos on YouTube
Hugh McLeay on YouTube
Hugh's website

Awesome! I will certainly do. Thank you.

I am not sure if this is the best place to ask this either, but I cannot for the life of me find out how fork stanchions are made. Does anyone have any info on this? I can make educated guesses but would love to find a video or article. Maybe I need a different search engine.

Posted: May 14, 2021 at 23:10 Quote
Oh, Hughs website is already awesome and I am like four seconds in. tup

Posted: May 14, 2021 at 23:16 Quote
Hugh is one of the few good kinematics designers in the industry. The one point on which we disagree is stability vs. instability of a decreasing anti-squat curve. Other than that, definitely listen to him! If you get deep enough into this to want to discuss stability of anti-squat curves, I'll be happy to oblige.

Posted: May 14, 2021 at 23:19 Quote
R-M-R wrote:
Hugh is one of the few good kinematics designers in the industry. The one point on which we disagree is stability vs. instability of a decreasing anti-squat curve. Other than that, definitely listen to him! If you get deep enough into this to want to discuss stability of anti-squat curves, I'll be happy to oblige.

Definetly, but right now I couldn't tell you what any of that^ meant lol I would guess anti-squat has something to do with how much the suspension lowers with the weight of the rider as opposed to the objects on the trail? My eyes are burning...

Posted: May 14, 2021 at 23:28 Quote
I'm afraid that's not it at all.

Squat, in this context, is the amount the suspension compresses due to either braking forces ("brake squat", which is the same as "brake anti-rise") or pedaling forces ("pedaling anti-squat", usually just called "anti-squat").

Pedaling anti-squat uses the chain tension to squeeze the suspension and reduce the amount the rear compresses due to acceleration. Think of how you do a wheelie: pedal hard and shift your weight back. A milder version of that happens during normal pedaling, but it's not enough to get the front wheel off the ground. A frame with rear suspension allows the frame do "pop a wheelie" internally, by rotating around the pivot point. Anti-squat uses chain tension to counteract this force and prevent this internal wheelie, keeping the chassis stable.

Posted: May 14, 2021 at 23:33 Quote
R-M-R wrote:
I'm afraid that's not it at all.

Squat, in this context, is the amount the suspension compresses due to either braking forces ("brake squat", which is the same as "brake anti-rise") or pedaling forces ("pedaling anti-squat", usually just called "anti-squat").

Pedaling anti-squat uses the chain tension to squeeze the suspension and reduce the amount the rear compresses due to acceleration. Think of how you do a wheelie: pedal hard and shift your weight back. A milder version of that happens during normal pedaling, but it's not enough to get the front wheel off the ground. A frame with rear suspension allows the frame do "pop a wheelie" internally, by rotating around the pivot point. Anti-squat uses chain tension to counteract this force and prevent this internal wheelie, keeping the chassis stable.

Ah, so it is a problem of pedalling effeceincy? (pretty sure I spelled at least one of those wrong) it almost sounds like one of those ethereal problems we know exist but only someone who has been riding a long time would notice. Not trying to bash the idea, I just wouldn't notice something like that unless someone pointed it out to me.

Posted: May 14, 2021 at 23:37 Quote
Pedaling and braking. Separate properties, though. People mostly discuss, and mostly notice, pedaling anti-squat. Brake squat (AKA brake anti-rise) is the kinematic parameter I worry about least when designing a bike.

Yes, pedaling anti-squat is related to efficiency. It's what gives one bike a "squishy" pedaling feel, another bike a "firm" pedaling feel, determines the amount of pedal kickback, and is related to the axle path. I'm sure you would notice these things if you were guided on what to look for.

Posted: May 14, 2021 at 23:40 Quote
R-M-R wrote:
Pedaling and braking. Separate properties, though, and people mostly discuss pedaling anti-squat.

Yes, pedaling anti-squat is related to efficiency. It's what gives one bike a "squishy" pedaling feel, another bike a "firm" pedaling feel, determines the amount of pedal kickback, and is related to the axle path. I'm sure you would notice these things if you were guided on what you're looking for.

Definetly felt the squishy pedalling feel.

The first 'real' mountain bike I ever rode was at the United bicycle Institute in Ashland, Oregon. There was an older mechainc their who was taking the same class I was who is a foes fan and had his suspension super-skwishy.

I don't know if you have ever been to a trampoline park but it felt like stepping onto one of those trampolines and sinking six inches.

Posted: May 14, 2021 at 23:46 Quote
I know what you're saying, though some of what you felt may not have been due to anti-squat.

The Foes DHS (assuming that's what you rode) does have somewhat low pedaling anti-squat, so that's not helping the pedaling efficiency. It also has a lot of travel, so even if the chain tension balances the "wheelie" forces, vertical inputs from the rider's pedaling style won't be balanced. If you were standing and sprinting with a sloppy motion like you were trying to climb a Stairmaster, the bike has a lot of soft suspension that you would've been bouncing around on.

Another factor is low-speed compression and low-speed rebound damping. These are properties of how the shock has been tuned for a given bike, and are effective tools to minimize bobbing due to the rider's body movements.

Posted: May 14, 2021 at 23:49 Quote
R-M-R wrote:
I know what you're saying, though some of what you felt may not have been due to anti-squat.

The Foes DHS (assuming that's what you rode) does have somewhat low pedaling anti-squat, so that's definitely not helping the pedaling efficiency. It also has a lot of travel, so even if the chain tension balances the "wheelie" forces, vertical inputs from the rider's pedaling style won't be balanced. If you were standing and sprinting with a sloppy motion like you were trying to climb a Stairmaster, the bike has a lot of soft suspension that you would've been bouncing around on.

Another factor is low-speed compression and low-speed rebound damping. These are properties of how the shock has been tuned for a given bike, and are effective tools to minimize bobbing due to the rider's body movements.

Theres something I know about. I have to scram and o catch some Z's, but will definetly read the website and those videos. I will have to go read the article you sent me again on frame material, too. Thanks!


 
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