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mttpekin

Adjustable Lower Control Arms

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10 hours ago, mttpekin said:

I put a e46zhp rack in my last e30 325is and might need to find a way to slide one of those into this thing... we'll see. I will make work with stock config first. 

 

 

Z4 electric assist rack in manual mode.  The only rack that's quicker is the z3 1.9.  And the Z4 rack is smaller and lighter with no hydraulic anything as it was designed to be electric assist.  This will be the route I go on my car, but my car already has a steering rack so it's a bit simpler...

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56 minutes ago, TobyB said:

Sorry, Matt, that didn't make any sense without the attachment.  Which MIGHT be below...

 

What I MEANT and said poorly was that the clevis will transfer a rolling motion to the LCA where it attaches

at the outer end.  The LCA will then need to roll as it goes up, needing a pivot at either orange circle below.

What I was trying to say was that the crank- shaped stock tension arm rotates at both ends in the rubber bushings.

 

And the green- circled connection to the subframe- is that a needle bearing?

 

try 4.jpg

 

 

 

 

Gotcha gotcha. OK. Toby got me de-rusting the trig.. This is what I came up with. I think it's close. 

 

Disparities in effective length lead to the 'roll' along the axis of the LCA tube during travel. According to my chicken scratch, over the entire travel (5.5in) that total axial roll value is 20deg. The stock suspension picks that misalignment up in 3 places. The LCA bushing, and the two tension arm bushings. Mine limit that to two. That 'roll' will be picked up by the LCA bushing and tension arm to subframe bushing. Cycling the stock suspension on car just now and watching front tension bushing definitely shows a good amount of compliance made by that rubber.

 

When parts are bolted to car in a few days I will cycle both the stock and these and photo/video the deflections achieved at all points. 

 

The green circle is the radius on the bushing carrier. They are designed to 'capture' the LCA bushing just like the stock ones do. The bushing 'ears' kinda catch within those radius'd edges. 

 

LCA chassis mount.JPG

 

where the green is a cross section of the bushing carrier.. 

bushing.JPG

 

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17 hours ago, mttpekin said:

Tommy,

 

Let me know.

 

Matt 

 

Allrigh since you ask :) First, I like that original geometry is retained. That's easy way to avoid mistakes making it worse. I also like that there is no modification needed to subframe.  

 

Build quality and attention to detail looks great.

 

Target group for such setup must be racing or serious track day use. There's no sense just for street IMO. With track suspension setups you usually want to get rid of flexible rubber bushings by replacing them with something stiffer or better yet with spherical bearings. I don't see sense in making such a nice adjustable setup but using the original rubber that let's the angles go all over in dynamic situation. I would at least like to see planned solution to go to uniballs/spherical bearings, whatever to call them, if and when wanted. (basicly same what uai wrote).

 

I like utilization of e30 ball joint. Effective and simple. I don't know if there is some flexible element inside or no. If yes, is there a stiff option available that would fit?  

 

Reliability? You sure seem to be qualified making such designs but still I'm a bit suspicios about reliability and strength. What's the size of thread in those eye bolts? Are you sure they can handle fatique in long term? With slicks over curbs?

 

Longevity? How long will those plastic bushings live before they are loose as hell? In water and dirt? There's quite many joints and lashes tend to stack.

 

Eariler I didn't see the plan using spirolocks on the pins. I guess they can be trusted, though I lack personal experience on those.

 

  BR, Tommy

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(edited)

@Tommy said about what I was thinking - as non native my english is not so well.

But the standard 2002 Setup is two rods three joints perfectly balanced no open questions. In this setup I see 4 "Rods" with 5 joints.
That won't work as you have rubber components in it. So your geometry is not defined.
The bolts that are screwed in the arms are not only stressed for push and pull but also for torsion and bending.
As much as i like the idea of the e30 lower ball joint it is of interest for people with 13" rims how far up in the casing the rotation center of the ball is. It should be as low as possible to compensate for rollcenter issues when the car is lowered. As well as dimensional if it interferes with 13" rims when you add the distancers.

I'll try to explain Parts are 1-4 (cyan) Joints are 1-5 (purple)
Joint 1 and 5 are Rubber and may be viewed as 6 degrees of freedom- if they were simply rotational  (1 degree of freedom) the concept would work. as there wouldn't be any under or over defined positions.
By eliminating joint 4 and 2 and it would work again with rubber in 1 and 5 - but then we're again at a standard suspension setup.
Joint 4 has 1 degree of freedom this means the axial (not torsional or bending) force is in direction of the rod (2) making part 1 a lever as the blue dotted line (direction of force) is far from the center of Rubber joint 5.
At joint 1 the force is more through the center of the rubber therefore part 4 is not that much of a problem compared to part1
Rubber bearing 1 is stressed in a whole different manner than in the standard setup - where it is torsion and axial no it is also rotation with the vertical axis - the rubber bearing is not made for that type of stress.
I hope that's understandable.

 

top.thumb.JPG.8b54022392cbdff778f64a07aeb21082.JPG

Edited by uai
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(edited)

@uai great explanation! I couldn't see all the issues related to rubber bushings before but totally agree with you. 

Edited by Tommy

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Tommy & uai (being able to speak technical talk in another language is super impressive), 

 

You're both right and I'm happy smarter guys than I are looking at this. 

 

I'm going to think about this and get back to you. The first revs of this were more traditional and utilized heims. I'll revisit those ideas & move that direction if that's what a majority seem interested in. That's also less $. It's easy for me to get lost designing for designing's sake. 

 

3 hours ago, uai said:

Rubber bearing 1 is stressed in a whole different manner than in the standard setup

My understanding is that the original designs forces are thru the center of both the bushings on the tension arm, in line with the imaginary line connecting those two points. This design moves that imaginary line 45mm rearward on that front connection point, invoking that moment. Is adding a moment to that bushing actually that bad? 

 

I just drew a pic of part1 (clevis) and threw numbers at it. Assuming 1000lb tension force down the axis of the tension arm in my design (34deg from axis of clevis), that 45mm offset invokes an 82.5 ft*lb moment on that bushing [[(45mm/25.4mm/in)*sin(RADIANS(34deg))*1000lb/12in/ft]]. That's acting in conjunction with that 1000lb force. hmm 

 

4 hours ago, uai said:

Joint 1 and 5 are Rubber and may be viewed as 6 degrees of freedom- if they were simply rotational  (1 degree of freedom)

if 1 & 5 were strictly rotational, I don't know how the 'roll' down LCA axis could be handled. 

 

I am going to get creative on that front attachment. I don't want to make something where people need to cut subframes. Rear rose joint seems like a solid idea. More later. Thanks.

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(edited)
41 minutes ago, mttpekin said:

I am going to get creative on that front attachment. I don't want to make something where people need to cut subframes. Rear rose joint seems like a solid idea. More later. Thanks.

Why not make part 1 (joint 4) a solid attachment point for a rosejoint that doesn't need welding at the subframe.

Or just copy the parts  of the Photo I've attached. I'ts simply an adaptor for a rosejoint to attach it to the OE arm in the place where otherwise the rubber would be. This would raise the need for eliminating joint 4 (bending the tube)
This rubber always has been a weak point in the 2002 front axle design.

Best practice since the 70s is to add a "Vorspannring" in the front and/or use Turbo rubber or Polyurethane that are stiffer to restrict flex under braking and allow for less toe-in to improve responsiveness of the front.
As I am restricted here in germany to tüv and historic approval my tweak is to replace the rubber at the front and at the inner side of the control arm with a rosejoint. Camber/caster is done at the top of the strut, but I modded the footwell when I did my front cleanup as I wasn't sure if I'd use 7" or 5.5" wheels back then.


vorspannringe02_015a.jpg

 

Edited by uai

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I just wanted to say. This thread makes me very happy.  

People from around the world collaborating and the OP open to feedback and insight. Thanks to all. 

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(edited)

I've spent the last 20 hrs brainstorming, drafting, and now I have this. Similar to the model back in March. 

 

This is rigid. My machinist is going to kill me / make me broke. The connection at chassis/tension bar is trick. No subframe mods necessary. 

v2.001.JPG

Subframe stock bushing carrier is transparent in all of these  

 

v2.002.JPG

v2.003.JPG

bottom collar is a tube welded to the cnc'd bar piece. Will provide the clamp surface that interfaces w/ subframe bushing carrier. Top clamping piece is a circular 1/4" plate steel w/ bolt circle 8x M6 cap head in gr 12.9. 

 

v2.004.JPG

more low tolerance pins. left side is captured by welded ring & bushing carrier. right side has little plate fastened to retain pin. pin sees virtually no axial force so it should be good. little bit of red loctite. m5 gr 12.9. 

 

v2.006.JPG

retaining plate. 

 

v2.005.JPG

 

this is w/ a 2000lb load on the pin. will be refined 

 

what thinketh. happy friday!

Edited by mttpekin
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(edited)

You could even remove the joint where the two rods meet and just make a simple lash and bolt them together.

Adjusting for length can be done on the other end with an internal thread on the tubing and an intermediate part between tubing and rosejoint either lh/rh thread or differential pitch.

But a much more appealing design.

Edited by uai

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Oooo, now you're starting to get downright sexy....

 

t

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Looking good now! Does the tension rod limit turning, I mean touch the wheel before oem?

I was also thinking if the tension rod mounting could be  assembled from front so that braking force would be carried by solid piece instead of bolts....but it would need large thread around and big nut to tighten which maybe isn'that appealing. 

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(edited)

controlarm.jpgTommys concerns are valid

Also the rear balljoint may face an issue.

Most period setups have the balljoint set at an angle

 

 

 

Edited by uai

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Been a little busy. Plan on finalizing the cad this week and start figuring how much it'll take to build that new tension mount piece. That kink for LCA heim will either be coped per uai model above or bent. Will have more in a few days. Thanks!

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(edited)

I'm getting close and learned an expensive lesson: dont design in a bubble and don't make prototypes before consulting the faq. I have some very expensive wall ornaments.. Like I could have rebuilt my motor.. Live n learn. 

 

The angled heim pickup looked hard and expensive to build. This one can be done on lathe in hopefully 1 operation. (UAI suggested this on p1...)

 

The tension rod mounting point doesn't give you too much room to play. Currently brg is 14mm ID like stock, might have to bump down to 1/2in ID. Brg w/ specifically high axial loading capacities.

 

Pin w/ retaining rings is now a stripper screw. 

 

Will be adding camber adjustability to the LCA & cleaning stuff up over the next few days. 

 

Best

 

MP

 

v3.001.JPG

Edited by mttpekin
uai props
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