great poster. i was really hoping sunn bikes would come out with an 0))) model.
DW's new suspension design. the split pivot.
- Thread starter dhkid
- Start date
What I'm saying, in case it wasn't clear is that most FSR bikes are basically single pivots in terms of acceleration performance. CC change (axle path center of curvature) on most FSR bikes is basically nonexistent. That linkage software, although not uesful for performance comparison can show this quite easily. Dave Turner (Turner Bikes) and Chris Cocalis (formerly of Titus) both realized this years ago and their product lines reflected that.
The bearings aren't under any more load than a typical FSR bike, and the Split-Pivot bikes use some pretty trick 17mm ID bearings that are custom sized to the load requirements. Stiffness is no different than from a faux bar bike.
It can be used from XC bikes all the way to DH bikes. There is no travel limit, high or low.
Emphasis added. I took that to mean this particular frame isn't the be-all, end-all design, and that different bikes for different purposes will be built with different pivot placements.dw said:
Point being, of course, that it should have an extremely similar axle path to an FSR whose BB pivot is in the same place.
Hell yes! That is what I prefer but that market just has not matured yet.
haha
This is a beer bike:
Negative on the Coors light.
I think BV is correct about that frame being just one example of pivot location, you can see here that Trek's is slightly different, and I don't see why you couldn't run a high-forward pivot for longer travel versions/bigger hits. Between the split pivot and the floating shock mount I'm definitely curious to ride one of these Treks. Seems like an evolutionary improvement to a very popular design, and one that can easily reach the masses. Nice work Dave!
DW LOVES his coors light.This is a beer bike:
Negative on the Coors light.
dood! JM_+Zedro! Roboty goodness!oh man... Jm_'s back
Well, I would agree with pretty much everyone that it's a good idea. Simple, but good. It's simply the stiffness benefits of a ventana-style rear end with the braking benefit of a horst link, so all in all pretty neat. That's mostly why I've said little in this thread, just not necessary, it's straightforward and easy to understand...well, for most people. Some people seem to have trouble understanding that it's a single pivot.
Kona Sales Manager to Kona Lead Designer "Doood, why didnt you think of that?"
Kona Lead Designer "Doood, I was too stoned bra, eh"
Kona Lead Designer "Doood, I was too stoned bra, eh"
It'll pedal well in the front gear that is inline with the pivot(probably largest),and have minor lockout(good for climbing)in the lower gears. So it'll be active in the DH(large/fast gear)and less active in the climbing gear.
Yes an FSR can have a similer axle path to this bike,but as it was written I just thought it was loose and taking advantage of a percantage of correctness. An FSR has a wider range of wheel path options.
By the end of 07, DW might need a two line signature
So, with the Trek design, does the chainstay / main pivot / lower shock mount design mean that you can get more travel from any given length stroke shock with excessively high ratios? It would seem that the lower shock mount would drop as the chainstay revolved around the main pivot.
so when the rear wheel is removed.... do the CS and SS separate, or do the axle-recepticles act as clevis pins? Be super cool if that could be arranged to be in double shear rather than single.
Nice solution though.
Nice solution though.
That was my whole point; it doesn't. An FSR design has an extremely similar axle path to a single pivot, and performs virtually identically with the exception of certain braking characteristics. I don't know what those Giant frames were like, since the pivot was located so far from the rear axle, but they practically locked out when you pedaled them, so there are other issues there.
Thus, his statement was accurate. This or that frame may not perform the same because the BB pivot may not be located in the same spot, but overall, there was nothing wrong with what he said. Map out the axle paths of your favorite FSR frames and they'll be the same as the axle path of a similar single pivot.
it just changes the actuation ratio curve, maybe as a side result you could bring the overall leverage ratio up but its not the itention behind the design i think.
Due to it's high pivot you have a valid debate,I thought the FSRs had a higher VPP,and possibly more rearward. I just thought it was an inacurate and possibly misleading but not really dishonest statement.
I'm to lazy to map the axle paths and don't care enough,so I'll just say for arguments sake that I stand corrected.
I may be wrong but I think the leverage ratio would go down, not up with that floating shock mount. The lower shock mount is moving down as upper mount is compressed, effectively keeping the shock from geting compressed fully until later in the stroke. No?
yes but travel is still the same so that means the top shock mount is closer to the seat tube pivot than what it used to be, basically less leverage because of the lower shock mount, more leverage because of the top shock mount, netting the same travel.
You still need to increase the length of the top arm to compress the shock that amount. I think that I built the first example of this type of layout (floating shock in front of the seat tube with a digressive lower link) on the IF Tungsten Electrode dw-link bike. I did it more for manufacturing purposes than anything, in my experience using this layout you can make a slightly less expensive bike and you can vary leverage rate, but nothing overly complex is possible as far as leverage rate goes. It does look cool.
Dave, what do you call this design? Rear shock mounts to the lower swingarm.
not sure what dw calls it, but i call that thing the definition of hideous.
i think it's the camo rims....
Dave, what do you call this design? Rear shock mounts to the lower swingarm.
its a horst link, shock is also floating but is not digressive as dw called the one on the tungsten, on this one, both shock mounts "meet"
i think its a very sound solution to the horst links biggest drawback (rear end flex) and a lot cleaner than specializeds version (the demos) as here they can concentrate more material on the swingarm that now bears the shock mount, which helps to stiffen the rear end better.
so what would a cowan ds with a split pivot ride like?
I'd hope it doesn't have all the braking characteristics of an FSR bike. Like the way most FSR bike's lift up in the ass under braking.
Whoops!! What I meant to write was "more travel from any given length stroke shock without excessively high ratios?You still need to increase the length of the top arm to compress the shock that amount. I think that I built the first example of this type of layout (floating shock in front of the seat tube with a digressive lower link) on the IF Tungsten Electrode dw-link bike. I did it more for manufacturing purposes than anything, in my experience using this layout you can make a slightly less expensive bike and you can vary leverage rate, but nothing overly complex is possible as far as leverage rate goes. It does look cool.
Seems my query raised a few monkeys heads, and I am grateful for the response. Thanks.
DW with the Independant bike pictured on the previous page how much load is taken off the top rockers main pivot bearings by having the shock mounted to the lower pivot rather than the frame? I can understand for a few reasons it may have not been ideal to use,but I was just curious if you'd looked at that at all.
there arent any more variables to shock ratio than travel and shock stroke, so you are essentially answering "no" to your own question there.
more travel given the same shock = higher ratio
no matter how its actuated.
then again, some ways of actuating shocks are better when you have a highly leveraged application, sideloading is a factor, and also having a progressive leverage curve means you can use less spring rate or air pressure and thus get away with a higher leverage rate.
Similar but pretty different. This works like an old Chumba, or like the very first Sunday frames where you have the shock compressing from both ends. The IF bike actually decompresses the shock at the bottom as the suspension compresses, and therefore uses a longer top link to achieve the desired overall leverage rate than if the shock was just mounted to the frame. This fusion bike uses a shorter top link to achieve the same overall leverage ratio as if the shock was mounted to the frame on one end, Make sense?Dave, what do you call this design? Rear shock mounts to the lower swingarm.
Dave
I did look at this, there was really not much advantage or disadvantage here IMO, kind of a wash. The biggest advantage was just that we didn't have to fabricate or weld more ti.
why not just put the disc tab on the seatstay of a kona style suspension,then you would get very good braking behavior IC far in front without the complexity of cocentric rear pivot.
Kind of the floating of late bb7's were the floater mounted on top of the rear axle.
Kind of the floating of late bb7's were the floater mounted on top of the rear axle.
That is a great observation. This all has to do with instant center placement. The more forward the IC, the more the bike's/rider's center of mass will pitch forward during rear braking. The more rearward the IC, the less the bike's/rider's center of mass will pitch forward. I personally design for less pitch than more in the bikes that I work on. This is something that is rider preference entirely, but I find that more riders prefer less forward pitch than more, especially as you get into the higher levls of downhill racing.
I was actually just attempting to explain this to someone on MTBR this AM.
Dave
Just like a regular cowan DS but with improved braking characteristics. You also could change main pivot location to anywhere your heart desired to achieve whatever acceleration response you want without screing up braking.
Dave
so how does moving the pivot change the pedalling? is it because of chain torque? i have a single pivot and an fsr and the single pivot likes to get stiff when i pedal and the other one does not... only difference that i can feel.