Both, but the linkage fork concept is a lot cooler, and potentially stands to be lighter (whereas adding the floating brake can only ever be heavier) with the possibility of altering the suspension rate. A floating brake would be a bit of a pain to mount, I'm not sure just how well a stanchion clamp would work, but it could definitely be done.
Not going to lie, I'd love to see what kind of a linkage fork your mind comes up with. I love the idea of bearings and a happy little CCDB vs. two giant tubes and giant springs and giant dampers....
As do I. I've never had the money/opportunity to build it, but as I said before, if anyone out there is willing to do the building, I'm more than happy to do the designing.
Evrac - sorry for hijacking your thread! If you're up for it, would you mind walking us through your design intent/processes? I'm interested to hear your goals with the design, and how you went about calculating the geometry of the thing.
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I've actually been thinking the opposite...how awesome would it be to have a 2012 Fox 40 mounted on the back of my bike...
Just kidding. I actually think the fork performance these days is so amazing that I'm surprised you guys think a linkage fork could do better. These days stiction is down, fork dive is handled well by LSC, small bump is good (better than could be achieved by linkage fork unless you had a crazy leverage curve IMO), maintenance issues aren't too bad, they are light as stink...what more could you want?
Just kidding. I actually think the fork performance these days is so amazing that I'm surprised you guys think a linkage fork could do better. These days stiction is down, fork dive is handled well by LSC, small bump is good (better than could be achieved by linkage fork unless you had a crazy leverage curve IMO), maintenance issues aren't too bad, they are light as stink...what more could you want?
Seals that don't blow every few weeks? Leverage rate control? Brake characteristic control?
I agree that fork performance these days is excellent, but IMO it's also taken a long time for telescopic forks to overcome the inherent issues with the design (mainly friction and sealing). Every issue has been overcome individually, but nobody has really put together an entire package where anybody's gone "yep, that's pretty well flawless" yet. Every year we get a bit closer but there is definitely room for improvement. Look at the ridiculous amount of technology involved in a bicycle fork just to get it to run smoothly - extremely precise tolerances, expensive surface coatings (eg kashima), fancy slotted, teflon-coated bushings, high precision low porosity thin wall magnesium castings, blah blah. Structurally a telescopic fork is a bit of a nightmare, but decades of refinement of incredibly similar structures (thanks to the limitations placed on steering geometry and axle path by a linear telescoping design) has eventually gotten us somewhere. Had the same effort been put into developing linkage forks with the same constraints on axle and steering axis motion, I think it's entirely possible that we'd actually be further ahead than where we are now!
Of course, I could be totally retarded, but I think there is some merit in the idea.
EVRAC, great project, hope that you will keep on.
Did the PARAFORK guy, Christian GUSIC, tell something more about this DH/FR version that didn´t make it into poduction (yet) or some news about their future production portfolio?
Not intended for DH use, and not a Norman HOSSACK design, but yet a funny
parallelogram fork (commuter):
Some years ago (2004-2005) a then student of mechanical engineering (Schrau-Bär) from Lower Franconia (the Northwestern area of Bavaria/Germany) designed an MTB with a linkage fork from the scratch and built it with the support of the bike manufacturer ALUTECH as his diploma project. There is a respective thread in the ALUTECH manufacturer subforum of mtb-news.de. Indeed, the bike was not designed for DH/FR use. In addition it has a geometry adjustment as a special feature for better climbing. The looks needs getting used to. Some pics:
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It has to be an outside hosting site, IE photobucket or imgshack or something, the forum probably doesn't allow hotlinking.
I'm with socket...how many times a month do you have to take apart your shock to regrease the seals and oil the shaft? Why does a fork on a bike weigh close to the same as a frame? Add in variable leverage for nice ramp up, an anti-dive linkage, and you've got some potential...even without getting into freaky axle paths. Plus, additional LSC is not really a "fix" for brake dive, but more of a band-aid. Imagine being able to tune LSC separate of any brake function...
I'm with socket...how many times a month do you have to take apart your shock to regrease the seals and oil the shaft? Why does a fork on a bike weigh close to the same as a frame? Add in variable leverage for nice ramp up, an anti-dive linkage, and you've got some potential...even without getting into freaky axle paths. Plus, additional LSC is not really a "fix" for brake dive, but more of a band-aid. Imagine being able to tune LSC separate of any brake function...
If you're going to cure brake dive using a linkage, it will be at the expensive of other rather important things. I don't think the trade off would be worth it.
I think LSC is the best way to cure brake dive because you can keep a straight, conventional axle path. And it's completely tuneable to blow off when you want it to.
I think LSC is the best way to cure brake dive because you can keep a straight, conventional axle path. And it's completely tuneable to blow off when you want it to.
Well, my preference would be to keep a normal fork, but add a brake linkage to it, like a USE fork, kind of....only double sided, and not necessarily with the axle path moving.
I think the reason anti-dive works for that fork is because the axle path is more vertical at the sag point.Well, my preference would be to keep a normal fork, but add a brake linkage to it, like a USE fork, kind of....only double sided, and not necessarily with the axle path moving.
I think having a crazy axle path on one end of the bike is enough...imagine two!
You may be right. BTW, I agree with Socket too.
Did anybody hear something more about the weird WATSON Bikes prototype since the write-up in NSMB in 2008?
I've been talking about linkage forks for what seems like forever and anytime I ever mentioned it to anyone they looked at me like I was insane...
I've got hundreds of photos of alternative linkage fork designs. Britten, Fior, Hossack, McKagen, SaxTrak, Telelever, etc.
The biggest problem I've always had is beating the unsprung weight of a telescopic fork. I do think the Motoczysz 6X Coaxial monoshock fork has a lot of merit. It's a really sweet design. You would have to design a very interesting linkage to make it work in a long travel bicycle application though.
I've got hundreds of photos of alternative linkage fork designs. Britten, Fior, Hossack, McKagen, SaxTrak, Telelever, etc.
The biggest problem I've always had is beating the unsprung weight of a telescopic fork. I do think the Motoczysz 6X Coaxial monoshock fork has a lot of merit. It's a really sweet design. You would have to design a very interesting linkage to make it work in a long travel bicycle application though.
this.
That's pretty interesting. I think it works on at least a partially different principle from the USE shock, since the axle is mounted on the lowers in this case. From what I can tell from the picture, it works like a floating brake arm, which I didn't realize would be useful on a fork. IMO, it wouldn't counter the pitch motion or change the component of the stopping force that goes into the fork due to the head angle geometry.
this.
I wouldn't mind reading the article...the dude was probably smarter than me! (EDIT: Then again, his idea didn't really take off did it...)
http://www.oldrice.com/nodive.htm
I guess it does work. The concept is the same or similar to a rear brake arm. That's what I was getting at with the USE concept. You don't necessarily have to get rid of the telescopic design...for better or worse, people are used to that and it works well. However, mountain biking is a different sport than road or motocross, where you're often riding steep, rocky, varied terrain. Then you get your weight all over the front, and have to constantly trim speed here and there, and suddenly a brake bar becomes a decent idea. It should only add a small amount of weight....the kind that non-weight weenies wouldn't notice.
I don't know...I think it's worth prototyping. I'd love to give it a shot. It's just a matter of getting one on a bike.
I guess it does work. The concept is the same or similar to a rear brake arm. That's what I was getting at with the USE concept. You don't necessarily have to get rid of the telescopic design...for better or worse, people are used to that and it works well. However, mountain biking is a different sport than road or motocross, where you're often riding steep, rocky, varied terrain. Then you get your weight all over the front, and have to constantly trim speed here and there, and suddenly a brake bar becomes a decent idea. It should only add a small amount of weight....the kind that non-weight weenies wouldn't notice.
I don't know...I think it's worth prototyping. I'd love to give it a shot. It's just a matter of getting one on a bike.
Cheers for the link, very interesting. Sounds like it was effective, although I can definitely see how not having the fork compress as much would lead to front end wash out when getting on the brakes...at least until you were used to it.
The question is, why didn't it catch on? If it was a better design, surely the motocross world would have embraced it?
Another interesting concept bike with a linkage fork and many more funny approaches was designed by Adrian GRIFFITHS at TopTrail Ltd. (CEng MIMechE), a professional engineer with over 25 years experience in automotive chassis engineering, and built by Dave WRATH-SHARMAN of Highpath Engineering as a functional prototype: The "Interconnected Suspension Bicycle Project", an all terrain concept bike.
Technical paper
Pics:
Videos technology:
Videos performance:
Technical paper
Pics:
Videos technology:
Videos performance:
Actually designing one for a client at the moment and it will be prototyped in the coming months..- its not for a MTB though - but same principals..
Good job, man. That is really cool.
Thanks Wilhelm, very interesting.
What will it be at the expense of? LSC is most DEFINITELY compromising optimum bump absorption if you're having to crank it to reduce brake dive. What if I told you that you could have a linear axle path (or extremely close to, like within a couple of mm), less dive under brakes, the ability to run your fork softer and more tractable without suffering on the steeps, and a progressive spring/damping rate that eliminated the need for heavy/sudden bottom out resistance that telescopic forks have?
Realistically the big factors IMO, given that a linear axle path/appropriate leverage rate are entirely feasible, are:
1. Weight. A linkage fork could be made around the 3kg mark for sure, but it'd require some pretty solid engineering. No matter what, unsprung weight is likely to increase no matter what, it's hard to find much that's lighter than a magnesium lower casting. Not saying it'd be a big difference or that it's entirely impossible to make something with a LOWER unsprung weight, but it would be a tricky task.
2. Strength/stiffness. Lower weight makes this harder to achieve, but you do have the massive benefit of not having to try to transmit torsional loads through a pair of cylindrical, lubricated interfaces which means stiffness should be a no-brainer.
3. Packaging. This is the REALLY big one. Leading link forks are obviously the easiest to package but then you can either have a linear axle path or desirable anti-dive characteristics, but not both. Trailing link forks have issues with the links colliding with the frame itself, and if you put the links underneath the height of the down tube, you have other issues with where to put the shock (hence Honda's 6 bar arrangement).
I'd say sounds awesome, I wish the brilliant engineering minds among us also had the time and money to do stuff like this!
I'll admit to not having the best working knowledge of anti-dive (faint memories of double A-arm suspensions in vehicle dynamics class about 14 years ago). But I also know that many brilliant minds have crossed through the two wheeled world, and the telescopic fork is still king. Refinement is an amazing thing. But so is creative thinking. I'd love to see someone have a go...this is one reason I love bikes
My interpretation/opinion, and it's my own, is that motocross is so refined a sport that a dramatic change like this would upset the handling that riders are used to....representing a hindrance rather than benefit initially.
I think it has potential in the MTB world, with proper tuning. One could tune the fork to have "less" dive than no dive, and with a proper amount of pro-dive in the back, you could potentially get a bike that, under braking, slackens out so you can completely dive into corners. Plus, with less dive under braking up front, you could potentially run a steeper HA with less impact on handling.
I suggest a all carbon version
Let´s roll ...I'd say sounds awesome, I wish the brilliant engineering minds among us also had the time and money to do stuff like this!
I'll admit to not having the best working knowledge of anti-dive (faint memories of double A-arm suspensions in vehicle dynamics class about 14 years ago). But I also know that many brilliant minds have crossed through the two wheeled world, and the telescopic fork is still king. Refinement is an amazing thing. But so is creative thinking. I'd love to see someone have a go...this is one reason I love bikes
... at least the mechanical engineering master minds among us ...
Seems like a good way to punch yourself in the face.
Just a bike for tough guys, in particular in the rough terrain.
So would you then prefer a carbon linkage fork with a rather lacy style like the $96,000.00 RENARD Motorcycles "GT"I suggest a all carbon version
or the rather compact and always brute looks of the $92,500.00 CONFEDERATE Motorcycles "B120 Wraith"
or instead the CONFEDERATE Motorcycles "Renovatio" concept?
Besides, the alloy-made linkage fork of the $75,000.00 CONFEDERATE Motorcycles "P120 Fighter" ...
... resp. the "Black Flag" editon looks not so bad ...
What about this
With a vertical rail(thanks Yeti)a couple of inches back from were conventional stanchions would be to stiffen the lower linkage. Or just ditch the lower linkage, and use the rails with the shock between them. The linkage would be more durable with the rails and have less stiction though.
With a vertical rail(thanks Yeti)a couple of inches back from were conventional stanchions would be to stiffen the lower linkage. Or just ditch the lower linkage, and use the rails with the shock between them. The linkage would be more durable with the rails and have less stiction though.
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Yeah, or instead of an exposed rail system, you could even run a sealed, oil lubricated telescoping tube system...What about this
With a vertical rail(thanks Yeti)a couple of inches back from were conventional stanchions would be to stiffen the lower linkage. Or just ditch the lower linkage, and use the rails with the shock between them. The linkage would be more durable with the rails and have less stiction though.
And have the bottom linkage continue past it's pivot, and counter lever onto a shock to get the weight centralized in the frame and off the front.Yeah, or instead of an exposed rail system, you could even run a sealed, oil lubricated telescoping tube system...
Right next to the gearbox and rear shock
Like some air shocks?Yeah, or instead of an exposed rail system, you could even run a sealed, oil lubricated telescoping tube system...
Are you taking the piss?
Isn't the point to make it work with existing frames?
...
On the opposite end of the scale is the 18"-20" wheeled mini bike "Colossus" by Toshiyuki KIMORI that was unveilled at NAHBS 2010:
Martin WIMMER designed a funny 29er bike with a patented front suspension (US 7,140,627 et al., licensed by BLACK HAWK Patents Inc., Iowa) that seems to show some similarities with the BMW Telelever concept and has a weird looks, which was unveilled at Interbike 2008 but is not (yet?) in production (1,2):
There was even a hardtail with the WIMMER front suspension in the makes but I didn´t recover the URL.
I remember an interview with Jeff JONES of JONES Bikes where he was telling that he had a totally new conception of a bike suspension from the scratch in the mind. Unfortunately I did not find any further informations about this idea.
However, I don´t anticipate that the leading manufacturers of bike suspension will seriously deal with linkage forks as long as they can still sell their telescopic forks with little improvements every year again and again. But I am confident that the situation will change sometime, the latest when the function will be almost perfect and aesthetic issues as well as personal preferences in design more and more come to the fore, as is already the case e.g. in the chopper scene for some time.
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