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  #21  
Old 12-15-2017, 11:50 AM
gills gills is offline
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I measured mine up quickly, but they're modified OEM arms with rod ends on the inner pivots. They should be close.

Forward pivot to BJ: 14"
Rear Pivot to BJ: 12.5"
BJ center from upright surface: 1.125-1.25"

And I checked inner pivots center-center and it matches the dimension on the S14 subframe that 2_Liter_Turbo shared.
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  #22  
Old 12-15-2017, 01:47 PM
gills gills is offline
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trac rod on my car is actually 8.5" as well so I set mine to that.

I've got a working kinematic model now. The RUCA and toe inner pivots are slotted, but I centered spheres at all the pivot locations. Initial observation is that I see that with an OEM toe rod length centered in the inner pivot the upright is toed out with the dimensions we're using. Would you like me to share in your drive?




Determining ride height is important here obviously. People typically measure from hub center to to fender lip, which is ok for an individual, but many of us have rolled and pulled or completely cut stock fenders so using that to compare isn't the best.

When I set ride height, I'm measuring link angles (LCA near BJ in front, toe rod in rear) with a digital angle finder. I *think* for a s-chassis without the subframe all the way up against the chassis shouldn't have the toe rod much passed parallel at right height. Mine is above parallel at ride height by a few degrees.
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Last edited by gills; 12-15-2017 at 02:19 PM..
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  #23  
Old 12-15-2017, 08:46 PM
Stingy49 Stingy49 is offline
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Very cool! Please do share it in the drive. Do I need to give you permission? If you wanna pm me your email I can go ahead and add you.

Also looking at the geometry it makes sense that we would be toed out given that we're using the extended trac rod length.

Yeah finding a reliable way to reference ride height is always tricky. I'll pick up a digital angle finder and then we can be on the same page. Can you only adjust the subframe to frame spacing when you have solid bushings, like the ones from spl?
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  #24  
Old 12-16-2017, 03:26 PM
gills gills is offline
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I'm not sure actually, but you'll probably need give permission. I didn't try because I didn't want to spoil your own fun, but I'll throw it in there on Monday. I'll pm you.

I set my rear ride height during my last corner balance with the toe rods at 6 degrees above parallel. They are straight toe rods. That's with my subframe tucked to chassis. Yes on the bushings.

Anyway, in the model with the camber rod at 12.25 centered in the inner eccentric and and everything else as discussed with the toe rod at my ride height, it was showing crazy camber. Like -3 or -4*, but my actual camber is -1.7. I went to check my links and it turns out the eccentric is pushed out all the way so hopefully that will make the model jive with my setup.

My toe rod is 14" with the eccentric centeted, which I also need to set in the model.
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  #25  
Old 12-17-2017, 12:16 AM
Stingy49 Stingy49 is offline
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Yeah I'll model my own also. Probably when I scan in my s13 subframe. I just wanted to see the linkage move correctly on my screen :P.

I'm interested to hear how well it matches your car once you correct the link position and length.

EDIT: I made a LCA based off your measurements. How did you do the offset joint for the lca ball joint? I've been googling it a bit and I can't find out why the "Gap" field is greyed out.

Last edited by Stingy49; 12-17-2017 at 10:47 PM..
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  #26  
Old 12-18-2017, 10:31 AM
gills gills is offline
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OK, I added my inventor assembly into your folder.

I need to confirm that the S14 subframe model that was shared can accurately simulate the UCA and toe rod inner pivot eccentric adjustment. Right now they are just slotted in a single direction and I'm not even sure the slot range jives with what the actual eccentric can do. I'm sure they are close.

So with my link lengths at what I think my ride height should be around, I'm showing -3.75* of camber and a wicked amount of toe out.

In reality I am total toed out 1/16" at static ride height as per my last alignment (much to my disdain) and -1.7* camber. Something is off with the model and my setup, just need to determine where.

So on the surface here, the model does toe-in slightly under bump which matches what Jason M had measured along a host of other things with his setups: http://www.nissanroadracing.com/showthread.php?t=2674

I still need to delve into using dynamic simulation to actually create some meaningful graphs with respect to differing link lengths.
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  #27  
Old 12-19-2017, 12:58 AM
Stingy49 Stingy49 is offline
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I spent some time tonight and got the model to not be over constrained in the dynamic simulation environment. I also have it swinging a reasonable arc through the suspension travel. Now I just need to figure out how to get the output grapher to show what we want. It seems to only show information on the different joints or individual points (if you add them with the trace tool). Ideally I will figure out how to display plane vs a ref plane information.

To be fair we haven't confirmed the subframe model yet. I will be scanning mine in sometime next week once the turbo build is done. Buttttttt it is a s13 subframe so that doesn't really help you.

Yeah we should probably verify the actual factory adjustment range.

Always good to hear the model is behaving somewhat appropriately . As someone who has never made a moving assembly before it's pretty satisfying to see it all moving and looking realistic in Inventor.

As I was trying to figure out where to mount my td04 on the log manifold I made I was thinking how useful this 3d scanning would be for routing hoses and just figuring out how well stuff fits in the engine bay. For the turbo it's not really worth the time but it could be worth it for more space constrained setups. I've seen vibrant performance scan in an engine bay to build headers on the Speed Academy youtube channel. Pretty neat stuff. Could be neat to scan in an interior for roll cage design...
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  #28  
Old 12-19-2017, 09:02 AM
gills gills is offline
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Nice work.

Yea, not sure you'll be able to monitor plane angles. Points may just have to be sufficient enough. It seems that you can make plots based on user derived functions of multiple points/traces, i.e.-derive some trig function to get you toe and camber angles plots with respect to time. Just need to make sure your reference origin has the principal axes aligned with the toe and camber planes.

As for my mechanism, I've got it much closer and it's probably just error now. I remeasured my links to try and be more accurate. My toe rod is 14.25, my RUCA is more like 12.3125 and my Trac rod is 8.625. Putting the RUCA at full positive on the eccentric and the toe rod eccentric slightly outboard gets me as close as it's going to get to my actual alignment.

As for the weird angle on the RUCA eccentric slot on the S14 subframe model, it's because the point on the subframe RUCA clevis where the eccentric bolt "pushes" off of is off centered like that. Makes more sense.
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  #29  
Old Yesterday, 10:32 PM
Stingy49 Stingy49 is offline
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So I made a small rectangular piece to sit on the knuckle where the wheel bearing would go. The idea being that I could keep it aligned with the toe and camber planes throughout the suspension movement, like you were mentioning.

I've been struggling these last few nights trying to figure out how to constrain this added piece so it does that. Have you had any luck with this? It's weird because I can't tie an edge plane of that "wheel" piece to one of the planes on the subframe mounts as it would constrain either the toe or camber depending on where I did it.

The piece in question.



I could make a "wheel" piece with a degree of freedom for each camber and toe respectively and then appropriately constrain each section of the piece. Seems like an overly complex solution though.
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