i remember you working on a project like this. how did it turn out?
BTW, John i love my roller perches!!!!!!!
I was thinking that when doing the math. But I thought there was some other advantage to mountng to the LCA instead of the UCA.,,,,,,I just looked back at the 'load transfer' thread on CC. That thought in my head must have come from the first half of that thread discussing a desire to move the load to the LCA . That thread ended with your adjustable UCA. Been 2yrs, where is it?
cool, i'll shoot you an email when i get it home and get started on it. gotta sell the stang first though, so i'm not real sure how long it will be before i can do it.
when i saw that setup with the yellow parts i immediately thought about you, it looks like your kind of project.
i've been thinking about this for a while myself and another thing i thought of would be to use a spherical bearing in the upper shock eye instead of rubber (you've got me thinking roller everything
well it wouldn't let me attach the pic so here's a link
http://www.classicperform.com/NewProducts/2006/6267TCA-K-Large.jpg
i was thinking about using this lower arm kit (or somethinglike it; wink.wink) with your upper arms and that coilover deal i posted earlier. what do you think?
http://www.classicperform.com/NewProducts/2006/6267TCA-K-Large.jpg
i was thinking about using this lower arm kit (or somethinglike it; wink.wink) with your upper arms and that coilover deal i posted earlier. what do you think?
I think there is more to it than just those two things, and I'll try to explain: With the spring and shock mounted on top of the upper arm, and the upper arm mounted halfway up the shock tower, all of the forces are acting on the shock tower between the upper arm and the top of the shock tower. This results in a lever arm of several inches above the frame rail, where ALL the forces act on the upper half of the shock tower and in just two directions (up and inboard... no wonder they crack). In addition, because the shock is mounted near vertically and the upper arm is both short and the shock is halfway down it, it goes through a relatively large arc for a given amount of vertical travel, so the shock gets into bind precisely because the rubber bushings resist that motion, but just eliminating them will not result in the same motion or the same transmission of loads.
In comparison, the lower arm is much longer and therefore travels through a much smaller arc for the same amount of vertical travel, more closely approximating linear motion. Virtually all the dirt and circle track cars based on street cars use this design layout (where the rules permit). Placing the shock at the outboard end of the lower arm allows a lower spring rate to control the motion, and it can most certainly be felt. With the more linear motion of the lower arm, the lower spring rate and the rod end to allow free movement, the motion is predictable and smooth.
Additionally, some portion of the load is now carried at the LCA pick up below the frame rail and exerting a force acting in opposition to the force at the top. Imagine if you push in below the frame rail, the rail becomes a pivot point, pushing the top out. The load is distributed all the way to the top of the shock tower, so there are opposing forces (although not equal in magnitude) that help stabilize the shock tower. This reduces the flexing of the shocktower.
Without putting strain gages on both a C/O suspension and a "stock" layout for comparison I can't say how much difference can be seen in the loads, but if you're just dying to get some numbers, get a freshman college physics book and draw all of the force vectors and make some baseline assumptions (e.g. weight, acceleration, coefficient of friction for the tires etc) and you'll get some idea.
As for me, after I drove the new suspension I don't really care what the numbers turn out to be... it's a huge improvement I can feel. Not everyone wants to go fast through turns though, and if you drive slow enough and mostly display your pride and joy at car shows, I'm sure the stock suspension is just fine.
As a side note, most of the improvement of the C/O mounted on top of the arm will be realized by the bearing on the bottom where the arc of the upper arm connects to the vertical motion of the shock. The top can utilize a rubber or poly bushing and provide some isolation. This is the exact same combination in the roller spring perches/stock shock layout that Open Tracker advocates.
Sorry for the tome.
no problem, i think that explains a lot more than my basic knowledge can relay, i can see it but i can't say it.
The advantage of a cantilever suspension is you can engineer it for any spring rate rise you want. The cantilevers initial movement is close to a 90 degree intersection of the arms which gives the arms a mechanical advantage over the spring/shock and as it comprresses it moves away from that and this causes an increase in the spring/shock rate. It has nothing to do with the hardness of the F-1 cars as it was first used on dirt bikes that need miles of suspension travel and soft-to-harder springs to control wheel movement over all that junk in the dirt.
And as far as not being able to make a soft suspansion with good geometry throughout its range Mercedes-Benz would argue that with you. I've owned them and they work very well even when leaned over as far as they will go. MUCH better that that damned McPherson POS that BMW uses. Which, BTW MUST be kept from very much movement to get it around a corner quickly.
I believe Formula type cars use cantilever setups to increase spring/shock travel, rather than to reduce it. With their stiff suspensions, these cars have very little wheel travel.
I'm not an expert on this, but I can imagine that precise shock absorbtion becomes difficult to achieve with very little travel and high damping forces. Increasing the travel with a cantilever increases shock travel and reduces the necessary damping forces for a certain amount of wheel travel.
Another advantage is that the shocks can be mounted inboard in the nose section, rather than outside, where it upsets aerodynamics, among other things.
The freedom of the mounting position is probably also a reason for the use of a cantilever system on bikes. Additionally, only one (bigger) shock/spring is needed, which is lighter than two smaller ones.
I'm not an expert on this, but I can imagine that precise shock absorbtion becomes difficult to achieve with very little travel and high damping forces. Increasing the travel with a cantilever increases shock travel and reduces the necessary damping forces for a certain amount of wheel travel.
Another advantage is that the shocks can be mounted inboard in the nose section, rather than outside, where it upsets aerodynamics, among other things.
The freedom of the mounting position is probably also a reason for the use of a cantilever system on bikes. Additionally, only one (bigger) shock/spring is needed, which is lighter than two smaller ones.
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