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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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#7 · (Edited)
You disappoint me Drew.

At the very least, bamboo legs. :)

I've had the same idea, I've dismantled my Girvins with the same purpose, but stopped when I realised that I was just doing it to see if it could be done. (I don't really want suspension - just another thing to maintain).

If I was going to do it, I'd do it to my Fournales too.

If it was the Girvin, I'd change the lengths of the links to alter the suspension path.

EDIT: Forgot to congratulate Wickedlite on a neat conversion.
 
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#6 ·
Noleen top links should be cheaper to get machined up. The hardest part you might have is cutting and extending the legs since they are not round stock. You could clear a 24" fat tire without adding height. But then again.... you can machine a height spacer, just not the cheaper mill process.

I cut and added a 1.5" gap in the legs with .75" overlap each way.
 
#13 ·
Those pics are the newer version Fournales which you can see are more 3D machining and they have bearings which are replaceable. I have the new ones too but thought the machining to match would cost more but I did lengthen them for one of my 29ers. The ones I fattened are the older version with flatter machining and unreplaceable bushings.

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I'm gonna tear it down and do a weigh in today. I'm not a weenie but definitely a gram counter. I will get some pics side by side so you can see diff.

And I tell ya after riding all winter with out suspension and going for a ride last night with...I forgot how great suspension was and I was gigglin the whole way. Smooth, fun, long ride it was.
 
#18 ·
Those pics are the newer version Fournales which you can see are more 3D machining and they have bearings which are replaceable. I have the new ones too but thought the machining to match would cost more but I did lengthen them for one of my 29ers. The ones I fattened are the older version with flatter machining and unreplaceable bushings.

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I'm gonna tear it down and do a weigh in today. I'm not a weenie but definitely a gram counter. I will get some pics side by side so you can see diff.

And I tell ya after riding all winter with out suspension and going for a ride last night with...I forgot how great suspension was and I was gigglin the whole way. Smooth, fun, long ride it was.
What's with the wheels covers?
 
#17 ·
Ok... so weights as far as I can get them.

I didn't weigh forks before or after mods. I didn't weight the fork tube spacer before I bonded them on but they are extremely light.

Note: bushings are out of old links and in new links as well as oil ports.
Original top link 84.7g (wo bushings), New top link 145.9g(w bushings)= +61.2g
Original bottom link 101.8g (wo bushings), New bottom link 162.7(w bushings)= 60.9g
New wider face plate 33g+16g nuts and bolts= 49g

So that's 171.1g more weight(give or take because of bushings)
This does not include leg spacers.

I know I can drop weight in the nuts and bolts and still drill/cut out some weight.
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The new face plate is longer and bolts to old face plate and the legs. This was a cheaper route than machining the old face plate with shock mount
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Small Fournales originally weigh 1230g. G-Dang, I shoulda weighed in before I put them back on. I rush to put back on because I hate down time on riding so bare with me. I will get complete weight soon.
 
#22 ·
Speaking more as a gadget-guy, could you tell us the length of the two links, and the distance between their pivots on the steer tube and the fork legs? Basically the lengths of the 4 sides of the linkage. Also, the fork leg length from top pivot to center of drop out?

I have an old spreadsheet built to analyze these linkages, and I'd like to see the curve produced.

Thanks.
 
#25 ·
Make your own ehh?

Fork legs from center top pivot to dropout center: 21.5"

Top link:
Front center pivot to rear center pivot: 4"
Top link front width: 5"
Top link rear width: 3.228"

Bottom link:
Front center pivot to rear center pivot: 4.5"
Front width: 4.316" (approx because of O-Rings)
Rear width: 3.233"
 
#32 ·
Much like the Whyte PRST-1

View attachment 780245
The Whyte is a superior design IMO - it separates the suspension from the steering.

....I adapted a Girvin Vector fork to my bike.

...The ideas of maintaining trail, and anti-dive have value but haven't caught the attention of the users....
I'm not surprised that they haven't become popular, although I think it's a shame. Properly designed they have many advantages.

In my opinion the problem was that the linkage forks used for bicycles totally ignored the lessons learned from motorcycles. A girder fork on the likes of a Velocette (usually a Webb fork) or a Girdraulic on a Vincent all worked well, and at speeds we can only dream of (on a bicycle).

It is important to stop the travel of the linkages before the fork reaches the point where there is dramatic change of direction of the wheel path - none of the bicycle forks I have (5 different types of linkage fork) have long enough links (IMO) and so are suitable for short travel only. Wadester's Girvin fork demonstrates the dangers of this nicely.

For example the Vincent fork worked quite well until people realised it could be made longer travel by tweaking the fork and shock for more travel. Then followed tales of the fork topping out and stuttering when the brakes were applied at speed, nearly always in twisty stuff. Eventually it was shown to be a combination of the brakes being applied immediately after a period of hard acceleration (ie racing). The fork was already in the top position and because of the extra travel the linkages were too high and the forces actually tried to push the fork higher - in other words it acted like a rigid fork at high speed! Usually followed by tankslappers, expensive grinding noises and cursing. (There was no problem with an unmodified fork)
 
#31 ·
Back in my skinny 26er days, I adapted a Girvin Vector fork to my bike. Suspension wise, it was better than the lame telescopic the bike came with - despite the elastomeric spring (at least it had a hydro damper).

Point being, the one bad behavior it had was from the "J" shape at the beginning of travel. If you unexpectedly hit an obstacle, the wheel would travel backward while you and the rest of the bike traveled on forward, then instead of coming to a sudden stop - the fork would rebound and flip the bike out from under you. Land flat on your back with your head just past the obstacle and the bike upside down back up the trail. This happened 3 times over the four years I had that setup. My spreadsheet showed a more pronounced "J" - or more backward movement in the initial travel than implied by factory literature.

I still have that fork, as well as an AMP F1 that I've never ridden. I think that one of the reasons that girder/linkage forks have never caught on is that altho they offer many possible/theoretical advantages - they all have different paths and are not really comparable. Moving backwards initially was supposed to cushion the hit - but look at the tradeoff {flip}. The ideas of maintaining trail, and anti-dive have value but haven't caught the attention of the users. Either that or they just look too funny :thumbsup:
 
#33 ·
Well I have head over bars on many different forks but I ride pretty hard on stuff xc forks and bikes aren't made for. I love the look and feel of links and I do have girders on my Triumph Bonnies too. They are pretty chopped out so no over bars there.
 
#36 ·
According to Dirt Rag Whyte PRST-1 | Dirt Rag Magazine that is all true:

"There is a story behind all of this. If you know your mountain bikes, then right away you see the similarity between the rear triangles of the Whyte and Marin's full suspension models. The two British fellows responsible for Marin's monocoque design are Jon Whyte and Adrian Ward, both of whom are Formula One engineers, so their expertise in suspension designs speaks for itself. But during their work with the Marin bikes, they discovered what they saw as inherent weaknesses in traditional telescopic forks: a lack of torsional stability (flex side to side) and a steepening of the head tube angle as the fork compressed.

In response to these perceived flaws, the two came up with their own fork design, the one you see on the Whyte bike, called the Plus Fours (for its 4" of travel and increased stability). The story goes that the fork was too radical in design for Marin to embrace, so Jon and Adrian set out to make their own bike."
Also -
"I see the Whyte PRST-1 bike as an over-designed, over-built bike that performs well at the expense of mechanical simplicity-and at the expense of your wallet! Most of the "solutions" that the Whyte offers are to problems that don't exist, at least not in this writer's opinion."
 
#37 ·
I'd buy a Whyte PRST like a shot at the right price - just to keep in my collection.

I suspect any problems with the Whyte PRST will be down to the shock used or simple wear items like pivots and ball joints, rather than a design flaw.
 
#39 ·
No problem. I was really taken by the Whyte PRST-1 when it came out. Such an elegant front suspension - and a crappy low-forward single pivot rear. I recall that they finally came out with the "Quad Link" two-link rear suspension along with the "Plus Four" front - but I never could afford (or find) any of them.

Looking at the Plus Four, in the light of Velobike's comment on short links giving too much curvature to the travel path - look at the length of the lower link compared to all of the available linkage forks. I haven't located my spreadsheet as yet - but I don't think I ever mapped the Plus Four system.

For an available fat-moddable linkage system, the girder style "short" links are gonna be the place to go since longer involves a proprietary frame.

The fournales is:
___4"___
6" 6.5" F->
___4.5"__
 
#40 ·
Woot! Found my old spreadsheet, and I've done -
Girvin Vector - up to 2.5" travel!
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The Whyte PlusFour
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Now I just have to remember how to set up a new geometry! The two gridded graphs show the linkage in initial and final positions - but for some reason I set it up so the calculations have the things layed over, then rotated to true head angle.

I actually had a linkage fork laid out with similar curve shape to the Whyte, and 4.5" travel.
___3.5"___
8.5" ___8" F->
___5.75"__

Fournales:
___4"___
6" ____6.5" F->
___4.5"__
 
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