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Fatty Look Fournales Suspension Fork

31K views 73 replies 23 participants last post by  deuxdiesel 
#1 ·
Just had my Look Fournales machined up with just enough room for a 5.0 if I want. 3.8 Nate on there now.

I love link forks and just couldn't go Lefty. I think I'm under their weight too. Unverified, I added about 200g to the already light fork. I was too excited and had to get them on. I will get to weighing in soon.

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#41 ·
I took a peek at Whyte's website and It looks like they've abandoned th radical linkage forks a while back in favor of standard telescopic ones. They are also getting rid of the twin link rears in favor of standard 4 bar setups. Nice bikes though.

As an extreme technophile myself, I am always looking for innovative and elegant solutions that are quite different from the standard setups everyone has, even if they work great as is.

I do see the value in going to extremes in radical designs to get even a small advantage in performance or practicality.

It seems though, that as promising as linkage forks are technically, both the motorcycle, and bicycle designers, as hard as they've tried haven't come up with one that works better than the best telescoping forks, at least as far as winning races.

I do think my AMP fork was significantly better riding than a rockshox of the same vintage, but I probably never rode the top end shocks the racers used.

Is Answer winning any races yet with their Kilo design?
It seems to be the best overall effort currently.

I think the same could be said about the twin short arm linkage rear suspension, except that they have won quite a few races. It seems all the reviewers in the press at least consider the old 4 bar Horst link to have less pedal bob, and feedback though. Isn't the twin arm's strong point supposed to be those points? When you add rocker arms to a Horst link, it should be able to get the same kind of wheel/spring rate curves, so if the twin link setups can't beat the 4 bar in pedal bob/feedback what is their advantage?
 
#45 ·
I took a peek at Whyte's website and It looks like they've abandoned th radical linkage forks a while back in favor of standard telescopic ones. They are also getting rid of the twin link rears in favor of standard 4 bar setups. Nice bikes though.

As an extreme technophile myself, I am always looking for innovative and elegant solutions that are quite different from the standard setups everyone has, even if they work great as is.

I do see the value in going to extremes in radical designs to get even a small advantage in performance or practicality.

It seems though, that as promising as linkage forks are technically, both the motorcycle, and bicycle designers, as hard as they've tried haven't come up with one that works better than the best telescoping forks, at least as far as winning races.
Oh yeah. Linkage forks do have potential advantages over telescopic - but teles are cheap, work well enough, and are what the non-technophile expects. I note that BMW motorcycles have not one, but two different linkage based front suspensions -
The "R" model TeleLever, which uses telescopic legs, but has spring and damping on an "A" arm that takes all the load.
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And the "K" model DuoLever, which is a girder - but with the links on the frame and ball joints for steering.
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I note that both of these look conventional, so you can sell them to the clueless as well as technophiles. Can't get away with that on bicycles.

I think the same could be said about the twin short arm linkage rear suspension, except that they have won quite a few races. It seems all the reviewers in the press at least consider the old 4 bar Horst link to have less pedal bob, and feedback though. Isn't the twin arm's strong point supposed to be those points?
Gonna disagree on this one. Read between the lines on reviews and find that twin link systems don't require "platform" - whereas 4 bar/faux bar systems do. Until you stand and start bouncing around - then they all do. Every rear suspension system I have looked at (with the exception of Lenz Milk Money and others with a BB concentric pivot - all 4/faux types) change chain length with travel. This will cause some bob or feedback between suspension and pedalling. The twin link bikes I have owned (R88, ETSX, RIP9) didn't have any noticeable amount of either - and my best reasoning says it is because the "instant center" (the equivalent simple swingarm pivot point for the "normal" link position) is out around the front axle. Why should this matter? Well, the line between that point and the rear axle is nearly parallel to the chainline/force vector, and the leverage of the chain force vs that equivalent long swing is very low.
DW link trys to align that leverage to counter squat, VPP uses its "pocket" of inflection to try to keep the suspension there under chainload. Set the sag wrong on any twin link and things don't line up so well.

When you add rocker arms to a Horst link, it should be able to get the same kind of wheel/spring rate curves, so if the twin link setups can't beat the 4 bar in pedal bob/feedback what is their advantage?
I'm not sure what you're trying to say here. A Horst link is a 4 bar with the rear axle on the seatstay. The 4 bars are seattube, swingarm, seatstay, rocker(with shock). Faux bar puts the rear axle on the swing arm - where the linkage doesn't affect it's travel at all.

Twin link, the 4 bars are seattube, lower link, rear triangle, upper link.

Spring rate curves are set by the upper link/rocker vs the shock.
 
#42 ·
I think the biggest problem linkage forks have to overcome is racing.

They have a completely different feel and if you have a top level racer who has invested years in getting the skills to handle a bike that dives under brakes, one that doesn't (ie a properly designed linkage) is going to feel all wrong. If you set up a linkage fork to dive like a tele, then you have removed one of its virtues.

If the racers don't use it, then the rest of the market isn't interested either.

Wadester - thanks for the graphs :)
 
#43 ·
most of the linkage forks look like they would have a pro-dive tendency for the first half or so of the travel, then go towards anti-dive. I assume this was to try and keep some of the dive feeling of a telescopic fork, as well as making the first part of the travel be more responsive to small bumps.

the Kilo is an exception. It looks to have anti-dive as the overall tendency throughout the travel.

I would like to see someone build an anti-dive telescoping fork. All you would need to do is mount the caliper to a bracket that can rotate about the axle, and has a link going up to the crown, or upper leg, just below the crown. You could even have multiple mounting holes on the bracket to adjust how much anti-dive by moving the link rod closer or further from the axle centerline.
 
#50 ·
Here are some numbers I calculated to to compare the changes in Rake/offset at the axle with 3" lower link moving +/-20 degrees giving 2" of travel and a 2.5 and 2.375 upper link the pivot points where 5" apart. (Ignore the 71.xxxxdeg numbers).

2.5” upper link, 3” lower link, 2” Travel

70deg 1.4330Offset 71.4508deg (compressed)

75deg 1.4608Offset 71.2454deg

80deg 1.4823Offset 71.1066deg

85deg 1.4956Offset 71.0263deg

90deg 1.5000Offset 71deg (upper and lower links perpendicular to H.T. Angle)

95deg 1.4958Offset and 71.0263deg

100deg 1.4842Offset and 71.1066deg

105deg 1.4675Offset and 71.2454deg

110deg 1.4491Offset and 71.4508deg(uncompressed)


2.375” upper link, 3” lower link, 2” Travel

70deg 1.4701Offset 71.5977deg(compressed)

75deg 1.4811Offset 71.3241deg

80deg 1.4912Offset 71.1405deg

85deg 1.4978Offset 71.0346deg

90deg 1.5Offset 71deg (upper and lower links perpendicular to H.T. Angle)

95deg 1.4981Offset 71.0346deg

100deg 1.4937Offset 71.1405deg

105deg 1.4899Offset 71.3241deg

110deg 1.4915Offset 71.5977deg(uncompressed)
 
#52 ·
The fork legs will probably be 1.125dia by 035wall 4130. I might do carbon fiber like Look used. The rest will be 7050 aluminum. The model I posted pictures of is just to test the geometry of the linkage. I am going to use a air spring and put a enertia valve in the oil compresion/dampening system to stop pogo affect when climbing. I modeled the head tube and King headset and the upper pivot will be built into the stem. I may machine the King base plate on to the 4130 steer tube.
 
#59 ·
Old thread, I know, but the Look Fournales is a LOT more along the lines of what I'd think of as an acceptable fatbike fork, as compared to the inverted taiwan-mass produced thing floating around now. Linkage forks aren't great for every application, but they make a lot of sense here IMO.
 
#63 ·
yes to me too. But i can't do it myself and they said they havent got a mold/clamp to welt wider legmounts .. My best guess is that its more of a warranty issue then anything else. Maybe their new Revolution fork comes wide too as successor of the flame but i have my doubts about that too.
 
#64 ·
Thanks for answering that Scalty.

Getting a guy to cnc up new brackets is a bit. But cheaper than a new fork. I think Kilos would be cheaper than the Fournales when comparing brackets. I have both.

Here are the guys you want to talk to if you want the lightest. I'm gonna suggest a fat bike fork from them. If more people do maybe they will make it.

Carbon Lite Leaf Spring Sweetness: Lauf Forks - The Lauf Trail Racer 29 - The lightest suspension fork on the market
 
#68 ·
I love link forks.

I do look at the Lauf fork and see a strong possibility of side to side play. Even moreso done as a fatty. I don't know how they can compensate for it as is.

I also like neat stuff and lite stuff. Lighter fat bike parts are welcoming.

I will stick with my Kilo No.1s for my xc race bike. Love that thing. Rides like butter
 
#71 ·
My Necromancer with Fournales. I'm going 9 zero 7 this year to drop a ton of weight.
My 17lb Voodoo Kalfou Rocket with Kilo No 1
Very nice. I'd got myself confused between the German-A and the Parafork which is why I thought it could be spaced out. I can see why it would be a bit more difficult than that.

Don't know why I got confused - I've got a German-A fork on one of my bikes. :)

That's a nice light bike you have there.
 
#73 ·
...I think it would make a good fork for winter riders who spend time on trails with a snow-base of significant thickness in temps below 20f...it would also be interesting to hear from Mikesee re: his soft-tail/Actiontec ELS that made like one or two appearances here quite a while back...now where was that Square, I hope I'm not too late...
 
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