NS F355 Project (Page 64/73)
Yarmouth Fiero JAN 20, 07:11 PM
Hi Don. I am having a hard time visualizing your idea. Perhaps a side view would clear it up for me.

I saw your drawings in a thread from 2012 zkhennings and it certainly inspired my current design. I have some concern regarding your idea of pinching the ball joint pinch point though. If the piece restricts the clamping force on the ball joint shaft at all because of the extra stiffness of the additional material, it could possibly allow the ball joint to pull out due to reduced clamping load on the ball joint shaft. The OEM spindle design relies on the material deforming to provide the clamping force on the ball joint shaft. Even in my current arrangement I have concerns that the ball joint clamp is restricted on one side causing the casting to be deformed more on one side of the ball joint than the other. With regard to having the bolts in double shear, I think having the assembly bolted to the ball joint shaft as well as up at the tie rod connection should be adequate considering the most significant force on the tie rod is compression or tension as the spindle ( wheel assembly) tries to pivot about the ball joint axis. Like your earlier design, I will add a gusset between the horizontal and vertical parts of the assembly. I'll try to update the drawing accordingly tonight

Edit to add: as seen in the drawing below, is there a concern that the additional structure will prevent the green side of the ball joint clamp from deforming as much as the red side, causing the red side deform more and possibly crack under load? The spindle casting is machined to an specific thickness to allow the correct deformation when the ball joint bolt is torqued.

Input on this always appreciated.

[This message has been edited by Yarmouth Fiero (edited 01-20-2015).]

Bloozberry JAN 20, 09:12 PM
Doesn't the ball joint stud have a groove for the pinch bolt? That would positively hold the two together.
Yarmouth Fiero JAN 20, 09:27 PM
Indeed it does Blooz. So theoretically, they shouldn't come apart regardless of the clamping force applied.

I guess that's my green light to proceed.
355Fiero JAN 21, 08:09 PM
Yarmouth Fiero;

Hopefully this crude drawing shows more of what I am talking about. Looks like you are going down a solid path though so good luck.

Cheers
Don
Yarmouth Fiero JAN 21, 08:39 PM
Thanks for the great drawing Don. Its not crude at all. Your design is very clear to me now. Its an interesting concept and has great merit as a functional and practical solution to the common problem many of us have been contemplating. I think in the end, we all recognize what has to be achieved and there are certainly many ways to catch this mouse. I think the key thing to recognize is that any changes to the suspension of a car need to be well thought out and the solution / design needs to take into account the extreme forces that each component of the suspension will experience. In the end, we have to be comfortable with our design and our construction techniques because its us who will ultimately drive it and enjoy it......... someday

Thanks for sharing your design.
Yarmouth Fiero JAN 23, 10:39 PM
Continuing on with the design of the rear suspension, I ordered a set of rear poly bushings from TFS, a set of QA1 spherical rod ends with jam nuts and a length of 1 1/4" x 0.120" and a length of 1" x 0.120" DOM mechanical tube for my lower control arms. I got a new set of rear ball joints from Blooz in exchange for some FRP supplies last weekend and he also has a spare set of 9" tie rod swaged tubes that I hope to purchase.

I worked on the control arm design this week and made a few changes to get the tie rod aligned with the ball joint to minimize toe in change. I also realized that my new engine cradle deign was 0.6" too low so I raised it up to give a true 5" of ground clearance. This changed my static control arm angle from 3.64 deg to 6.23 degrees below horizontal. I think I can live with this but I'll see how the geometry performs.

With these suspension updates, I proceeded to plot the kinematics of the rear suspension. This is quite new to me so I started with plotting the camber vs the suspension travel. Here are the results in tabular and graphical form. I also borrowed the stock suspension data from Blooz's page 16. I guess its really comparing apples to oranges considering my suspension is '85 and his is '88 but atleast it gives some idea where my design stands. While I was at it, I recorded the amount of strut travel and the amount of lateral travel of the spindle. For the most part, it was less than 1/16" until the car becomes airborn......... and then I'll be smiling too much to really worry about it.





The next step will be to measure body roll and calculate the effect on the suspension geometry. That is a whole other can of lobster.

Edit: to swap graph axis and correct units

[This message has been edited by Yarmouth Fiero (edited 01-24-2015).]

Yarmouth Fiero JAN 24, 04:13 PM
Just so you don't think you're seeing things, I have updated my camber data and corresponding graph. It was pointed out that my graph appeared too linear so I collected the data a second time. This time I used my actual 3D model to calculate the results and the new data does seem to be significantly different...... hopefully in a good way. As I had mentioned above, I had to raise my cradle 0.6" to give the proper 5" ground clearance. This altered the static control arm angle and while I thought I had originally allowed for this, it's likely that I made a mistake. So the new results are posted above by replacing the original table and graph. Sorry for the change.
Yarmouth Fiero JAN 24, 07:21 PM
Here is a quick view of the roll center as generated by my current suspension configuration. Can anyone offer a layman's interpretation for the "suspension challenged" ie: me



Edit: To add a second view showing what is going on behind the wheel.

[This message has been edited by Yarmouth Fiero (edited 01-24-2015).]

85-308 JAN 24, 08:06 PM
what software are you using? I think, likely knowing less than you (or anyone) about suspension.. that the next step is to see what happens when you redraw it with varying degrees of body roll and see how far laterally (and vertically) the roll centre moves at increasing body roll amounts.
If I understand the science in this, the less movement the better - in any direction - .. it is almost ike you start your dwg/design WITH body roll and try to minimize movement, and see where things end up at 'normal' (ie no roll situation).

As one book explains it, you don't need great geometry when the car is on the straight-away or at rest ( ) but you really want stability (as in minimal, sudden, roll centre changes!) when you're half-way thru the corner etc!
My unqualified 2 cents.... if you don't mind!
GP
Yarmouth Fiero JAN 24, 08:26 PM
I'm just using my 3D modeling program Rhinoceros. I am reading up on body roll at the moment and then I'll get to rolling the model and shoot some new suspension projection lines. I think the 18" high CG is a pretty good estimate. Thanks Blooz.