5" Travel on Crosslink EXP's?

[will]

Since these forks are on the workbench, and I'm thinking about a new shock to replace the ODS/Spring combo, I decided to measure the travel and the "maximum travel."

With the right amount of shock travel and a reasonably short headtube, there's a full 5" of travel available on these forks. No kidding!

I measured the angular distance from the dropout center to the lower crown at both extremes and found slightly more than 5" of difference.

One issue is if any kind of a beefy shock (like an air shock) is applied, the clearances will quickly become a problem.

Hmmm... If I can get a decent shock in there and keep 100mm of travel (w/ disk brakes!), it sure would be better than any sliders I know of. You can't beat crosslinks for stiffness and steering response.

On the other hand, if crosslinks are not sprung and damped exactly right, they either break your wrists or sag and dive.

It could be a long and heartbreaking project to launch into, but they sure do look good.

...and the 856 doesn't look natural with the Marzocchi forks!

[Frankd3000]

Well, there goes that surprise. [smiley=laughing.gif]

Two things to look out for, Will, if I may because i've been looking into this for a couple of months now...

1) 5" of travel means you'll need clearance with the stem and the downtube. The stem is one issue. However, the downtube is another (bigger) issue. Unless you can do something to drop the lower pivot. You can raise the lower bearing race on the steerer tube, but you've only got so much room to play with.

2) good luck finding ONE (rear type) shock to support that much travel (i'm not saying any more than that - primarily because i'm still trying a few things out and not sure yet).

One solution for the 5" travel/clearance - make new links. [smiley=nod.gif] This will only help so much, but you get the idea. With new linkage pieces you can tailor the entire fork to what you want - more travel, more clearance, different travel arc, different shock orientation. See where i'm giong with this?

I was shooting for 4" myself. The amount of headtube angle you would loose would need to be accomodated for in the rear .... unless you want to reduce it purposefully. On my bike 1" of front rise is equal to about 1* headtube angle lost.... if I calculated properly. My set-up only shows an absolute maximum travel (no shock in place) to be 3 1/4". This is due to you having a shorter ULM, and me having the longer one.

Now you see the whole point of the MULA. This is only the beginning... remember? MOHAHAHAHAH! Oh, sorry, getting carried away again.

I agree with your points on linkage forks over telescopics. I've said it before and i'll say it again - linkage forever. I want more travel and i'll do what it takes..... but linkage travel.

[rapiddescent]

I was just going to say that the way to do this is to put a stiffer spring in (I can help here) and then put an extended eccentric link into the bottom link.

think along the same lines as the old RDI long travel kits or Simons modd'd 856 to put a 3 bar link in.  It'll have to be really small though!

callum
rd /s

[will]

Callum,

The only factor preventing my Xlinks from swinging farther is the shock. As is, the linkage has full capability of 4.5" and still leaving headtube clearance.

And since no one here wants my linkage forks, I guess I 'll keep trying to get them set up properly.

Anyhow, are you back in biz?  I sure hope so...  [smiley=nod.gif]
I could really use a 225 - 235# front spring and a 325# rear spring for my ODS units.

What do you think?

Also, can you do business across the pond?

Will

[Tom_A.]

A word of warning....changing ANYTHING on a crosslink (linkage lengths, critical distance, etc.) can have dramatic effects on both the fork geometry (i.e. trail) and also the travel path.



After playing around with various "what if" scenarios using a CAD program, I came to the conclusion that the only way to get more travel out of a x-link is to make longer links...but then, in order to keep the travel path reasonable, that would require new legs since the mounting locations of the links would need to be spaced further apart...oh yeah, the axle mounts at the bottom of the fork would need to be extended backwards to keep the trail correct.  Basically, you'd need an all new fork.



Not worth it IMHO.

[rapiddescent]

X-Links,
the problem with shocks and coil springs is that a shock *has* to have more travel than the spring otherise you're asking the spring to collapse down beyond its natural length.  

Some springs can do this; but the ones that noleen used are really quite string springs for their size and have to use fairly exotic materials to work properly.  I just can't see that a coil spring will be able to cope with that amount of travel as a %age of its height but I'll ask my spring_nerd_manufacturer about it!

yes.
we are just about back in business.  I unpacked all the old RDI stuff the other weekend and am currently getting a new website produced and also am setting up the endless-uk-bureacratic nightmare of starting a small business.  We are selling stuff through paypal to get started again and we have a full stock of HammerHead with some new product lines coming soon.  the one I've mentioned a few times is the new spring kit.

I have a box of old springs. none of them have labels on them so I don't know the lbs per inch ratings.  (which were mostly not that accurate by the way!)

callum
rd /s

[proflex252]

It is possible to have more travel!

Here you see my long travel girvin fork with 105 mm (a bit more than 4 inches) travel.
It was just a try. Smoth performance. I'll try to produce longer links made of carbon or having it cnc made in the future.

http://idriders.com/cgi-bin/album_k2.pl?photo=proflex252/frher_mit_spinergys_und_long_travel_girvin_gabelk.jpg


CU

[shovelon]

AWESOME!



Got me thinking. Each link lenthened  in ratio excluding the lower link shock mount distance would not alter the "J" path much. Is that what you did? Very nice indeed.



Terry

[proflex252]

yes, that's what I did.

And if you look in my gallery aou can see that I did some CATIA work to make cnc milled alu links in long version.

The travel with that links should be about 115 mm because they are a little longer than my try some years ago.

Just need to have time to build them.

[will]

I'm truly impressed with that linkage design. Simple, strong, light, and well thought out. (And, yes, I've got some CAD experience in my past.)

This board is full of some amazingly talented designers, fabricators, dreamers, and folks who just appreciate good design.

A steady flow of inspiration. Wow.

[Frankd3000]

proflex252 - when you came up with your link lengths did you keep the rake and wheelbase the same? It's hard to tell from the pic you have, but to me it looks a bit longer. Nice stuff, btw. Kinda looks familiar. Also, did you raise the rear at all to compensate the lost headtube angle?

Will - something tells me your CrossLinks aren't for sale anymore, eh. teeheehee

[Simon]

This all fascinating stuff
though having experianced vector2's with
elastomers and sprung version
also tried X-links I can't say I'm a fan,
however modding them to suit is what I like to see,
one issue I'm having (maybe unfounded but I thought I'd bring it up)
longer links will increase the fork rake
this in turn will slow down the steering making
single track less responsive,
also under braking the rake will increase much further,
if your going to the trouble of manufacturing new
links could you not keep the links the standard
length but angle the shock ie the lower mount
further out or even on the otherside of the lower
link pivot angled back,that would mean a longer
lower link but still mounted as standard but with an extension out to the front for the lower shock mount,unfortunatly you would also need a longer stroke shock to achieve more travel,
just an idea and a major redesign,
thought I'd share,its a bit out of the box but I'll think on it,
Simon.

[Frankd3000]

Simon - that's exactly why I asked about the upper and lower link lengths. If you just add the same amount to each you alter the rake, as you pointed out. I'm VERY fond of the responsiveness of my bike's steering and i'm not willing to change it.

My complete thought was to make new links, but the rake would inevitably be altered. Reason? Link lengths AND leg length (among other things). So, get some aluminum tubing, machine a new pair of drop-outs, disc tabs, V-brake bosses (one, the other or both if you're not sure) and link mounts. If we all remember Terry's recommendation then you can even weld it all. Piece of cake. In my specific case i'd need new legs because of my ULM and it's associated travel limitations. Also, the extra travel would easily put my pieces in encroachment of the bottom of the steerer tube and the down tube.

Back all this up with carefull measuring and an extended rear shock adaptor and the result should theoretically be lots of travel, with taller BB height and.... un-altered bike responsiveness (notice I didn't say handling). Again, unless you want to change things.

The shock travel issue? Linkage. It makes sense for a linkage fork. Use a long stroke shock (my version of "long stroke" is the one I have now @ 2") and use a solid strut from the ULM, where the shock attaches. That travels down to a "swingarm" that attaches also to the lower link. The shock sits between the two mounting to where the upper link attaches to the ULM (remember MULA 1 design?) and it all sticks out of the front. A little measuring and you put the shock where it will get you what you want. I figure that a 2:1 leverage ratio shouldn't be "too hard" on any of the current shocks out there. Probably a bit less than what most are designed for.

Now you see why I never said anything untill now. It all looks good in my head and works out reasonably well on paper, but untill I get out to the metal supplier I don't know. Comes with being a dreamer I guess. [smiley=laughing.gif] Think I should go for it?

Sad thought - maybe I should'a ordered a longer stoke shock for the rear afterall. [smiley=blankstare.gif]

Sorry, Will - I certainly don't mean to hi-jack!!!! Just share thoughts and ideas. Maybe we can all think up something and come out ahead, right? Crossbow's and all. [smiley=laughing.gif]

[shovelon]

I think a few of us have a disease called Proflexia- dementia. Or as my wife says,"if you love it so much, why don't you marry it?".

Terry

[Simon]

I think a few of us have a disease called Proflexia- dementia. Or as my wife says,"if you love it so much, why don't you marry it?".

Terry

Your wife as well,it must be catching  

Simon.

Frankd3000
I know from experiance it all looks good in your head and even when you've drawn things up you can't see any problems,
however when you actually make things and try to put it together things just don't fit as expected and can be very frustrating,
however once you've overcome these obsticals there's a great deal of satisfaction on acheiving what you had setout to do,
SO GO FOR IT.
Simon.