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Messages - Julian

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1
29er / Re: Carbonda FM 1003 / Flybike FM 1266 180mm "Super Enduro"
« on: November 27, 2022, 05:52:31 AM »
Quote from: Andrew Burns on November 26, 2022, 04:38:22 PM
I see that Sherpa appear to be selling this frame as the Olympus and some build options use a coil shock. Looking at the linkage plots in the first post I would have thought that this frame wouldn't suit a coil shock as the leverage ratio drops pretty linearly throughout the travel, wouldn't a frame designed for a coil shock have a progressively increasing leverage ratio throughout the travel?

Not at all. You can find plenty of heavy hitting frames with pretty linear leverage drops fit for running coils, including VPPs like the Santa Cruz V10/Nomad or horst links the Specialized Demo/Enduro.

And then you have frames with decreasing progressivity like the YT Capra or the Canyon Sender, perfectly fine running coils as well.

Increasing progressivity will mean diving through the mid travel and lower dynamic ride height, so definitely not only beneficial.

But as ever, it all depends on your personal preference and riding style. Numbers will only take you so far :)

2
29er / Re: FM1001 / FM1156 - 135mm frame
« on: November 09, 2022, 03:17:08 AM »
No, you're right. Smaller frame = (usually) shorter rider = lower CoG. I just used 650mm to make the results comparable :)

Edit: btw, the size M frame will even have a slightly higher anti squat. Small difference though.

3
29er / Re: FM1001 / FM1156 - 135mm frame
« on: November 09, 2022, 01:31:29 AM »
Quote from: veeTee1Pah on November 08, 2022, 01:54:40 PM
Kinematic analysis and "corrections" to the geometry chart.
https://insanityofgravity.blogspot.com/2021/02/8-linkage-check-fly-bike-fm1156.html

Suggestion for shock
https://insanityofgravity.blogspot.com/2021/02/17-linkage-welch-art-von-luft-oder.html

Found these browsing the interweb so not my analysis. Not sure if this has been posted here already.
TLDR:
  • Pretty flat leverage curve.
  • Relatively low antisquat.
  • The blogger suggests Megneg shock
  • Geo chart isn't quite accurate.

Not sure if you can trust this one... He seems to use the diagram from the geo chart, which would be very unreliable.

I used the vector graphic sent to me from carbonda and got very different results, especially concerning anti squat and head angle.

Here's a screenshot. I put in a 30t chain ring as well and the same Center of Gravity at 650 above the BB, since that affects the anti squat greatly.


4
29er / Re: Tideace 2022 New Enduro Mold FS838 Being Production
« on: February 21, 2022, 05:18:16 AM »
Quote from: graved1gger on February 21, 2022, 04:46:47 AM
This is kinda odd, since norco specifically states that new range is something like coil shock specific. Had Haideli screwed up kinematics?

Well, if the screenshot named "test.jpg" is based on the final design, then yes. But as I said, I'm hoping that it isn't.

The leverage ratio could be easily made more progressive simply by moving the shock yoke mount.

Right now, the progression from SAG to full travel is at 6,5%. Changing the position of the shock yoke mount by just 10mm would make it 24%. The Norco Range has about 22%.

5
29er / Re: Tideace 2022 New Enduro Mold FS838 Being Production
« on: February 21, 2022, 02:50:11 AM »
Quote from: FullCarbonAlchemist on February 21, 2022, 01:37:44 AM
One thing I noticed in the renders is that there seems to be an extra piece between the reverser link and the shock, a shock extension from what I can tell. It’s highlighted blue-green in the 3D renders. Maybe that alters the kinematics somewhat? Was it included in the Linkage X3 calculations?

You're right, it's a common shock yoke. The eye to eye without this part would be about 260mm, the yoke reduces that to 205mm. It has no effect on the kinematics though since there is no additional link (which wouldn't work anyway, it would just collapse in on itself).

The one effect it has is that there is no movement in the rear shock eye, meaning that the rotation is done by the bearing in the yoke instead of the bushing of the shock. So with the trunnion design, both ends run on bearings.

6
29er / Re: Tideace 2022 New Enduro Mold FS838 Being Production
« on: February 17, 2022, 01:09:10 AM »
There seem to be two different designs. Pics 2 - 4 show a link between chain stay and rear axle, the 3D renders and the one from Linkage X3 see the rear wheel directly attached to the chain stay. Pretty sure the latter is the correct version, since that's the same as the Range and the other one gives horrible results in the X3 analysis.

So I used the screenshot from Linkage X3 to look at the leverage ratio. Not quite as progressive as one might want, definitely not coil shock compatible since it's completely flat towards the end. Leaves room to hope that this screenshot is not the final design.

7
29er / Re: Carbonda FM 1003 / Flybike FM 1266 180mm "Super Enduro"
« on: January 31, 2022, 01:48:20 AM »
Quote from: zooky on January 30, 2022, 11:25:55 PM
Anyone have an idea what bike this frame is roughly based on?

I haven't seen any other bike like this. There might be some resemblance to the Nukeproof Giga which also uses a linkage driven single pivot design.

8
29er / Re: FM1001 / FM1156 - 135mm frame
« on: December 15, 2021, 03:14:33 AM »
So the effects of a 2mm offset bushing are:

- BB higher by 3mm
- head angle steeper by 0,3 degrees
- leverage ratio slightly less progressive
- 1mm more travel :D

9
29er / Re: FM1001 / FM1156 - 135mm frame
« on: December 15, 2021, 01:26:17 AM »
A friend of mine is running the offset bushing to bring up the BB, I think so long as the spacing is perfect and all the tightening force goes to secure the bushing, it should be fine.

But putting it on a rotating part has the side effect of changing the leverage ratio.

10
29er / Re: Carbonda FM909
« on: December 13, 2021, 04:51:26 AM »
This should visualize the different progression characteristics of the FM936 and FM909.

The blue line is the overall force needed to go from 0 to full travel.
The red line is the force needed to get the next 1mm of travel at any given point.

Both shocks are the same except for a slightly bigger volume spacer in the FM936 to match the overall bottom out resistances.

As you can see, the FM909 has a more pronounced "dip" in the late mid stroke whereas the FM936 is more evenly progressive. So with the same SAG and bottom out force, the FM936 will offer a better mid stroke platform and sit higher in its travel. Maybe the soft mid stroke of the FM909 has its advantages for an XC bike, but for down country, the FM936 should be better suited - also because of the 10-15mm extra travel.

11
29er / Re: Carbonda FM909
« on: December 13, 2021, 01:08:13 AM »
Quote from: lukwy on December 11, 2021, 02:56:05 PM
Hi Julian, take a look at attached vector PDF. Is it enough? I can export it to CAD format (DXF or DWG) if needed.

EDIT: According to my "CAD analyze" 165x45 damper leaves about 1mm clearance between seat stays and seat tube, but I didn't take into account the flexibility of rear triangle, so 45mm travel is very risky. Besides it is only the drawing.

Thanks! I used your vector PDF and got pretty much the same numbers. 45mm stroke is definitely too much.

If my model is correct, it has less travel than claimed though:

40.0mm stroke = 96mm of travel
42.5mm stroke = 101mm of travel
45.0mm stroke = 107mm of travel and a broken frame :)

12
29er / Re: Carbonda FM909
« on: December 13, 2021, 01:01:59 AM »
Quote from: numberzero on December 11, 2021, 02:09:23 PM
What do you mean by a "modern" leverage ratio.
How the suspension of this one will work compared to the FM936 if they're buillt with the same shock?

I mean it's not as progressive as one might want. Doesn't mean that it's bad of course.

My take: The biggest difference to the FM936 is not the overall progressiveness, but the way the progression changes throughout the travel. The FM936 is more progressive in the midstroke and basically linear at the end of the stroke. The FM909 is linear at SAG point, then becomes slightly progressive in the mid stroke and more progressive at the end of the stroke. Now air shocks generally lack progressivity in the mid stroke and are very progressive at the end of the stroke. Also, with volume spacers you can even increase the progressivity at the end of the stroke. But you can't really change the mid stroke. And so with the FM909, those similar characteristics enhance each other, making it more likely to fly through its travel and offering less mid stroke support. With the FM936, the opposing curves add up to a more linear overall lev ratio, giving more mid stroke support. The lack of bottom out resistance can be countered with volume spacers.

But please take this with a pinch of salt. I could be wrong :)

13
29er / Re: Carbonda FM909
« on: December 11, 2021, 12:17:35 PM »
Quote from: the.Capt on December 11, 2021, 11:55:49 AM
Thank you Julian. 

It looks like this frame has a old VPP leverage ratio.  Not sure if that is good or bad. - https://linkagedesign.blogspot.com/2016/05/santa-cruz-tallboy-2017.html

Are you able to tell if this frame would fit a longer 45mm stroke shock for a bit more travel?

True, the leverage ratio is all but modern. It seems that the older FM936 is more up to date there.

Both have the same suspension design though, single pivot with flex stays.

I tried a 45mm in the software and it seems that the rear triangle will collide with the seat tube at full travel...

But again, all this is based on a not perfectly accurate diagram.

14
29er / Re: FM1002 / FM1166 - 150mm frame
« on: December 11, 2021, 12:11:55 PM »
Quote from: Massey on December 11, 2021, 08:53:14 AM
Do have long legs not sure they are that long thought! haha.

From the middle of the bb to the seat clamp is 79cm on my current bike

That should even work with a OneUp V2 210mm.

If my diagram is correct, you'll have about 330mm of space between saddle clamp and seat clamp. The 210mm OneUp V2 will stick out about 60mm and has a stack height of 33mm, so 320 - 60 - 33 = 227mm possible dropper travel. The OneUp is pretty compact though, so a different brand might give you a lot less.

15
29er / Re: FM1002 / FM1166 - 150mm frame
« on: December 11, 2021, 08:27:37 AM »
Quote from: Massey on December 11, 2021, 08:13:51 AM
Looking to buy my first Chinese frame and 99% sure I'm going to buy FM1002 in XL, I was wondering if anyone knew what the biggest dropper you could fit? would love to get 200mm drop but would still be happy with 180/175mm. Any help would be appreciated!

You could fit any dropper post, so long as your legs are long enough :D

The XL has a 470mm seat tube and a 220 max insertion as far as I know. All dropper posts with that much travel have longer max insertions, so they won't go in all the way. You'll have to take that into account.

If you tell me your saddle height (BB to middle of saddle clamp), I can do the math for you.

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