My Car So Far...

motoTrooper said:
Very clear and well articulated, thanks Steve!
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Thanks for that. And you are welcome. :)

One thing I failed to note with regard to the reason the X's rear control arm bushings are not in the same axis:

In this photo is is obvious that the control arm and radius arm bushings, on the OE MR2 control arm/radius arm are perpendicular.

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You can see in the photo of the installed units I made that the radius arm is close to inline with the centerline of the chassis. And that the control arm is close to perpendicular to the centerline of the chassis. The radius arm bushing, is positioned perpendicular to the front/rear load for maximum resistance. The control arm bushing is perpendicular to the lateral load for maximum lateral load resistance.

This separation of directional load makes for good load management by the bushing but compromises its range of motion compared to the Fiat design. The MR2's bushings distort more as the suspension moves. Toyota tried to reduce this effect by adding a bushing that permits rotation where the radius arm connects to the control arm. The control arm divides the twisting motion between the radius arm/control arm bushing and the control arm inner pivot bushing. That helps somewhat but Toyota used three bushings where Fiat used two. And the Fiat two bushing solution, in practice, provides for better articulation and resistance to load than the Toyota.

My design, using spherical bearings at the chassis mounts eliminates the need for articulation at the intersection of the radius arm and contorl arm.
 
I've always thought it would be nice to have a "spherical" type joint (allowing movement in multiple planes) with a vibration absorbing material within it (something similar to urethane). Therefore the best of both words; free movement in all desired directions, with better control of the movement, but no metal-to-metal contact to transmit the vibration/harshness. The challenge of the concept would be having a special material strong enough to hold up to the loads and wear, yet soft enough to offer the needed compliance. One thought might be to make the overall size of the joint larger than typical metal heims to distribute the load to a greater area. But even better would be a different design of joint all together that is better suited to this. Much in the way the CV-joint replaced the U-joint.
 
Dr.Jeff said:
I've always thought it would be nice to have a "spherical" type joint (allowing movement in multiple planes) with a vibration absorbing material within it (something similar to urethane). Therefore the best of both words; free movement in all desired directions, with better control of the movement, but no metal-to-metal contact to transmit the vibration/harshness. The challenge of the concept would be having a special material strong enough to hold up to the loads and wear, yet soft enough to offer the needed compliance. One thought might be to make the overall size of the joint larger than typical metal heims to distribute the load to a greater area. But even better would be a different design of joint all together that is better suited to this. Much in the way the CV-joint replaced the U-joint.
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I made such a joint for a Porsche. The rule book prohibited the replacement of rubber bushings with any metallic material (so no spherical bearings). Poly bushings were quite legal but on the Porsche, much like the X1/9, the bushings were not on the same axis. The OE bushings were quite large and had a lot of deflection. So I made a poly bushing but tapered the OD from the center of the cross section to each end. This permitted the bushing to rotate and behave in a similar fashion to a spherical bearing. Binding was reduced significantly. This worked extremely well but the bushings didn't last very long.
 
I would think there must be a joint design of some type that is akin to the CV joint (but not literally the same), offering the movement without all the "play" and yet smooth/quiet. It might be easy to say, "if there was then the car makers would be using it". However that may not necessarily be true. It could just be impractical or too costly for mass production, but still good for limited custom installations. Race car designers do not need such a joint because the metal heim/spherical ones are best for that application. But for a performance street vehicle...
 
I would say that Steve's setup probably took a great deal of consideration and expertise on his part to setup correctly, that he may not be emphasizing. Most heims do not allow for a high degree of misalignment- think about it - you have a rod passing through the center that will hit the “hub” - allowing more or less movement depending on size of said bolt/rod and the cross section of the Heim center. Some joints require offset spacers which allow for a greater degree of misalignment. I think your average ball joint has greater degree of axial (correct term here?) movement simply because the “bolt” only comes out one side.

I think heims are often used simply because of the increased adjustment flexibility they offer for varying conditions, no?
 
Dr.Jeff said:
I would think there must be a joint design of some type that is akin to the CV joint (but not literally the same), offering the movement without all the "play" and yet smooth/quiet. It might be easy to say, "if there was then the car makers would be using it". However that may not necessarily be true. It could just be impractical or too costly for mass production, but still good for limited custom installations. Race car designers do not need such a joint because the metal heim/spherical ones are best for that application. But for a performance street vehicle...
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Hmmm, now I need to go off and design something and patent it. ;)

There are a bunch of interesting bushing designs. All intended to provide varying degrees of compromise on NVH and control. I am sure that smarter engineers than me have invested a lot of time in that pursuit.
 
lookforjoe said:
I would say that Steve's setup probably took a great deal of consideration and expertise on his part to setup correctly, that he may not be emphasizing. Most heims do not allow for a high degree of misalignment- think about it - you have a rod passing through the center that will hit the “hub” - allowing more or less movement depending on size of said bolt/rod and the cross section of the Heim center. Some joints require offset spacers which allow for a greater degree of misalignment. I think your average ball joint has greater degree of axial (correct term here?) movement simply because the “bolt” only comes out one side.

I think heims are often used simply because of the increased adjustment flexibility they offer for varying conditions, no?
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I did spend a lot of time on the design. Most of the effort went in to the chassis geometry. Articulation was actually worked out by testing components. They do make "high miss-alignment" spherical bearings. Fortunately, the suspension's range of motion was within the operating range of standard Aurora bearings.

Spherical bearings and rod ends are typically used to do things like; reduce friction, reduce deflection, reduce weight, provide for a wider range of adjustment. All things that can easily be done with rod ends or spherical bearings.
 
lookforjoe said:
Most heims do not allow for a high degree of misalignment
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But keep in mind, the primary direction of movement is along the pivot axis of the joint. The off-axis movement is not that much, so a spherical joint can easily handle it. Its not like we are asking it to go 90 degrees in two dimensions. Plus there are some tricks to allow a heim joint to handle quite a bit of misalignment (relatively speaking).
 
Just to throw in another idea regarding NVH
Manufacturers of carbon road bike frames have over the years experimented with frame inserts tuned to absorb the most common vibration and ‘noise’ frequencies. They’ve been used in everything from chainstays to bike seats to forks. My point is that all your vibration damping doesnt have to come from the bushings but rather (I dont know how you would configure this on a car) could be handled ‘upstream’ of the suspensions movement, maybe incorporated into the body mount tabs or control arms themselves. Many people think these are a form of suspension for stiff road bikes but really they are designed to absorb road frequencies. I believe Zertz (a common marketing nomer) is a play on words between Hertz and inserts. The word is out if they actually work but Specialized has incorporated them for years and still does on thier top of the line bikes.

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Do You mean like that in picture from BMW e36 front ?swingarm?, they have two tipes of them, without bushing in middle and with that are softer. In picture is with.
 
Ben Louis said:
Just to throw in another idea regarding NVH
Manufacturers of carbon road bike frames have over the years experimented with frame inserts tuned to absorb the most common vibration and ‘noise’ frequencies. They’ve been used in everything from chainstays to bike seats to forks. My point is that all your vibration damping doesnt have to come from the bushings but rather (I dont know how you would configure this on a car) could be handled ‘upstream’ of the suspensions movement, maybe incorporated into the body mount tabs or control arms themselves. Many people think these are a form of suspension for stiff road bikes but really they are designed to absorb road frequencies. I believe Zertz (a common marketing nomer) is a play on words between Hertz and inserts. The word is out if they actually work but Specialized has incorporated them for years and still does on thier top of the line bikes.

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Auto makers have used NVH counter weights and dampeners for years in all kinds of applications. My daily driver is an '04 Toyota Celica GTS. Toyota did a remarkable job on this car. Two weeks ago I put a new clutch in it and replaced the front and rear motor/transmission mounts. The rear has a rather large appendage that is tuned to cancel engine vibration.

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There are also similar thing employed on some cars, bolted directly to the chassis, for the purpose of canceling chassis NVH. So it has been done and is one of the reasons behind modern cars being smoother and quieter than previous generation models.

Also, note that many larger displacement 4 cylinder engines, which are vibration prone by nature, now employ balance shafts to help cancel the engine's natural harmonics.
 
Steve Hoelscher said:
Auto makers have used NVH counter weights and dampeners for years in all kinds of applications.
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Another common location for these is brake calipers.
To me this somehow always seemed like a "band aid" rather than a proper re-engineering of the problem. Like the way modern medicine targets symptoms rather than the actual cause of the disease.
 
Goldman sachs just put together a report detailing the long term buisness models of cure vs managment. Guess which one was more profitable?
 
Ok so now that we’ve moved the suspension talk elsewhere I actually have a suspension question or two but its related to my car so its ok I guess to circle back around again

So my springs are:
700.225.400 Rear
600.225.425 Front
+ Front sway bar

Tires are 185 w/ 5mm spacers
They dont rub Ive checked prob due to 2.25 springs
Staggered wheel spacing beneficial? That is wider rear track?

It seems like given the weight balance of the X you would want a stiffer spring in the rear not the front. I realize these are stiff springs and Im going to keep them but would it be worth swapping them front to back? Theres more than enough thread to adjust for the ride height diff between 700 and 600 spring lenghts so thats not an issue.

Also, next week I will be taking apart the front suspension. So any recomendations before I do? We don't want another poly bush type warning after its already been done again :confused:

**by recomendations I mean any pitfalls, no no’s, good fixes, beneficial adjustments etc...

Edit:
After looking at Dr.Jeffs comments below I think outlining my intentions for the car would be helpfull here.

1- Id like to get the car done and off stands sometime soon.
2- For now this will be a street car even though I am going for a racer/performance vibe mechanically and aesthetically. I would like some comfort where I can get it but this is intended to be a canyon carver 75% of the time. So call it 7/10ths of a race car, thats where I want it for now with room to grow in the future.
3- Im inclined to fix things mechanically to get a good runner as opposed to ‘getting them perfect’ adding in a little extra effort where budgeting and time permits (see #1)
 
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There was a lot of discussion about this a few years ago. I think Mark Plaia was the main contributor, but there were many others with lots of good input. Seems like a major factor was the addition of a front sway bar; with one vs without one changed the bias of front to rear stiffness. I'd have to review those old posts to get the facts straight though.

One thing to keep in mind is the intended use of the car; track or street or a compromise of both, and more comfort or performance oriented. Also what other changes are being made; different type struts/mounts, level of damping, sway bar(s), bushings, geometry alterations, wheels/tires, etc.

The stock springs are stiffer in the rear, but naturally they are a LOT softer than your current ones (I believe around 120-130 lb ?). But that is for a street application with comfort in mind. As I recall the typical aftermarket "sport springs" (usually lowered a bit and a little stiffer, and intended for a street car with normal struts) are around 150-175 lb, and also with the rears stiffer than the fronts (they tend to follow the factory design).

Others can better respond about track applications. But try searching for some of those earlier discussions, there was a lot of interesting info in them.
 
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