Enduro/AM - The Weight Game

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Enduro/AM - The Weight Game
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flag mtbman1980
O+
Posted: Oct 5, 2020 at 14:22 Quote
B650wagon wrote:
Still online and doing Bible of Bikes...?

looks like total shut down from the comments from the PB article.
flag seraph
Posted: Oct 5, 2020 at 16:55 Quote
Can someone help me figure out how the DW6 suspension design works? Looks like a Horst link but obv there's something extra going on near the BB/lower shock pivot.
flag heinous
O+
Posted: Oct 5, 2020 at 17:03 Quote
Here you go.

https://www.pinkbike.com/news/robot-bike-co-r160-custom-review-2016.html

Looks like a horst with a rocker, with a counter rotating link at the bb.
flag R-M-R
Posted: Oct 5, 2020 at 17:17 Quote
Picture it as a Horst with a main (chainstay-main triangle) pivot that moves mostly rearward as the suspension compresses.
flag badbadleroybrown
Posted: Oct 5, 2020 at 17:30 Quote
seraph wrote:
Can someone help me figure out how the DW6 suspension design works? Looks like a Horst link but obv there's something extra going on near the BB/lower shock pivot.
Looks like there's just a secondary pivot at the bb so there's two compact links there. Guessing extra stiffness and maybe axle path control vs a single pivot or link there. Looks like some needless extra complication vs standard dw.
flag R-M-R
Posted: Oct 5, 2020 at 17:46 Quote
Some people say anything more than a single pivot is needless complication. Six-bar systems give additional control over the kinematics, albeit with diminishing returns. There's a reason most suspension designs are four-bar.

For a given weight and general layout, more pivots will reduce stiffness. The extra mass of bearings, axles, and frame profiles could've been used to make a huge, single pivot at that location (i.e. a four-bar with a huge main pivot) that would be stiffer than a forest of small, closely spaced pivots.
flag seraph
Posted: Oct 5, 2020 at 17:50 Quote
R-M-R wrote:
Picture it as a Horst with a main (chainstay-main triangle) pivot that moves mostly rearward as the suspension compresses.

So the wheelbase lengthens as it compresses?Does that equate to the chain getting tighter and pulling on the derailleur cage?
flag R-M-R
Posted: Oct 5, 2020 at 17:55 Quote
Every bike's chainstay lengthens as it compresses. That's the nature of anti-squat, without getting too detailed about it (designs with an idler are a whole different conversation). That doesn't necessarily mean the rear wheel is moving rearward, mind you, it's just transitioning to a larger radius than would be the case if the pivot was concentric with the BB - i.e. rearward relative to a constant arc.

The moving location of the virtual pivots does not necessarily imply additional lengthening. We're just talking about the point of rotation moving, not the rear wheel.
flag seraph
Posted: Oct 5, 2020 at 17:56 Quote
R-M-R wrote:
Every bike's chainstay lengthens as it compresses. That's the nature of anti-squat (designs with an idler are a whole different conversation). That doesn't necessarily mean the rear wheel is moving rearward, mind you, just transitioning to a larger radius than would be the case if the pivot was concentric with the BB.

The moving location of the virtual pivots does not necessarily imply additional lengthening. We're just talking about the point of rotation moving, not the rear wheel.

I'm gonna need a diagram. Someone do it. It will be wrong if I try.
flag R-M-R
Posted: Oct 5, 2020 at 18:07 Quote
Below is a hasty sketch of how the the virtual chainstay pivot moves throughout the travel. The virtual pivot of the chainstay is found by drawing lines through the pivots and finding the intersections. Starts with the green lines (instant centre of rotation, or "vitual pivot point", circled) and ends with the blue (instant centre circled again).

Note this is the instant centre of the chainstay. The instant centre of the whole linkage would be found by repeating this process of drawing lines through the pivots using the other physical links and this instant centre in place of the usually static chainstay pivot.

Very rough drawing of how the main pivot of a Robot R160 with dw6 suspension moves throughout the travel.
flag nubbs
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Posted: Oct 5, 2020 at 18:56 Quote
isaacschmidt wrote:
Circe wrote:
RIP Bike Mag
sad day indeed. I don't know how many of those I have on my shelf...

Super sad day! Dang.
flag heinous
O+
Posted: Oct 5, 2020 at 20:07 Quote
seraph wrote:
R-M-R wrote:
Every bike's chainstay lengthens as it compresses. That's the nature of anti-squat (designs with an idler are a whole different conversation). That doesn't necessarily mean the rear wheel is moving rearward, mind you, just transitioning to a larger radius than would be the case if the pivot was concentric with the BB.

The moving location of the virtual pivots does not necessarily imply additional lengthening. We're just talking about the point of rotation moving, not the rear wheel.

I'm gonna need a diagram. Someone do it. It will be wrong if I try.

There's a video in the review showing it in action.
flag skerby
Posted: Oct 6, 2020 at 6:31 Quote
I was at a motocross track the other day and saw someone setting tire pressure with one of those digital shock pumps that RS and fox sell, I felt dumb for never thinking about that before. Now I just need tubeless valves that come in schrader.
flag riish
Posted: Oct 6, 2020 at 7:04 Quote
Shock pumps have a range up to 300-350psi. They're not going to be as accurate in the range of 15-35psi as an analog gauge that operates only in that range, even if it's a digital readout.
flag Tsoxbhk
Posted: Oct 6, 2020 at 7:28 Quote
They are also low volume high pressure so it would take forever to fill a 2.6 tire.

 


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