Blooze Own: An F355 Six Speed N* Build Thread (Page 78/126)
FieroJimmy AUG 31, 06:37 PM
Don't forget to consider the inverse load as well. That would wind up pushing the upper mounts toward the center of the car. The extra reinforcement might be warranted factoring the leverage of the mount arm to the frame rail.
Bloozberry AUG 31, 07:14 PM
True, but the load direction you suggest will only ever occur on the side of the car that's on the inside while going around a corner, and given the weight transfer the loads will be considerably less than those generated by the outside tire.

I'm also trying to argue my way out of reinforcements because I have precious little room for them between the inside edge of the frame rail and the transmission in that area.
bubbajoexxx SEP 01, 01:07 PM
the reinforcement is only needed where the upper brackets are welded in and will not affect the trans space it is just to prevent tearing of the base metal and increase the load area

Bloozberry SEP 02, 10:19 PM
OK, I see what you mean. I actually show flanges on these mounting ears in my drawings to do as you say... spread the load over a greater surface area of the rail. That was back when I thought I'd be able to "bend" these ears to have flanges. The trouble is the parts are just way too small and made of steel that is way too thick to bend with any accuracy given the tools I have on hand. I did have a closer look though to see what I could do about giving the mounts a greater area where they meet the rail and think it will be worthwhile to weld some flanges onto the ears. That'll follow after I mock up all the parts to be sure everything fits and aligns.

I've made some progress on the forward upper link mounts over the last couple days. I needed to locate these mounts 252 mm further forward of the centerline of the aft rod end so I measured along the sheet metal and made an access hole in the sheet metal to expose the top of the frame rail:



I also needed to make a small slit in the weld flange to gain some clearance for the aft mounting ear which overhangs the inside edge of the frame rail by a couple mm's:



Creating the templates for these mounts was a little more difficult that I expected. They have to position the rod end so that when the link is installed and the rod end is centered, the link will sit at 42 degrees to aft upper link, AND a line drawn through the centers of both the front and rear upper rod ends has to be parallel with the car's longitudinal axis. To make matters more complicated, the frame rail runs at 7 degrees from the longitudinal axis of the car (when viewed from the top). I have to admit there was a little head scratching but I got the templates figured out.

Actually fabricating the mounting ears went quickly because all I had to do was trim up some ears I had screwed up earlier while making the aft link mounts.



I use my belt and disk sander to square up all the edges and fine tune the final dimensions of the mounts:



And once built up, you can see why it wasn't a straight forward task to imagine what they would look like.



This is the top view of the driver's side frame rail with both upper link mounts mocked up. It's a nice clean installation.



And this is the view from the wheel well. I'll refine the size and shape of the window in the sheet metal once I get the proper rod ends. I've gotten an email from Jegs saying they should arrive by Friday... Yay!

Bloozberry SEP 04, 09:18 PM
Well... this project seems to be about taking one step forward and two steps back. I ran into a rather significant snag yesterday after making the templates for the upper links at the top of the knuckle. The rod end on the forward upper link doesn't clear the wheel. I could've sworn there was plenty of clearance in my drawings so I had to go back and see what went wrong. It didn't take long to realize that I hadn't drawn the inside diameter of the wheel but rather the outside diameter of the wheel lip, to which I made the suspension components fit. After doctoring up the drawing with the correct ID of the wheel (red circle), the interference became apparent. To make matters worse, the drawing doesn't include the head of the bolt running through the rod end, which would dig even further into the rim. Drawing all this stuff out was supposed to eliminate these kinds of errors!



So ever since then, I've been trying to find a solution that minimizes having to go back to the drawing board. I tried every conceivable way to package the rod end differently and keep the same configuration of the links but it doesn't look like it's possible. So the next thing I tried was to swap the angled link to the back and the true lateral link to the front. This would work since the upright part of the knuckle is offset towards the front of the car giving me the room I need for the angled link towards the back, like this:



That looked very promising until I realized that it would adversely impact the direction of toe gain under jounce, effectively making the car oversteer. I didn't want that after all the effort to make this car handle correctly.

At the moment I believe the easiest way to fix the problem is to make both upper links parallel to each other and make them both true lateral links, like the lower ones. I'll keep them the same length as the original upper aft link so no other parameters except toe gain should change. I'll lose toe gain throughout the suspension's travel, but that's better than having the toe go negative. Also, having one upper link angled was a way to triangulate the upper portion of the knuckle over a larger area, making it less susceptible to unwanted movement at the top of the knuckle. Having the upper links parallel to each other will impact that characteristic somewhat, although I don't think it's that critical since the top of the knuckle in the stock Fiero only has the single strut mounting point, plus whatever side to side resistance there is in the spring to keep it from moving or twisting. Anyone see things differently?

Tomorrow I should get my rod ends in the mail... that'll help me mock things up so much more easily. I'll work up a new drawing showing my latest concept and post it tomorrow.
bubbajoexxx SEP 04, 09:41 PM
why not lower both links 3/4 of an inch using 2 plates bolted to the upper part of the spindle upper mount and pick up the spring rod at the same time
Bloozberry SEP 04, 10:20 PM
Thanks for your suggestion Bubbajoe, but lowering them 3/4" would have a significant impact on the roll center movement and a smaller, but important impact on camber change throughout the suspension travel. I need to keep all of the pivot axes in the same locations and orientations to keep my nearly perfect theoretical performance characteristics. All I'm willing to do is slide the rod ends along their current axes to find better packaging otherwise I'll end up throwing all that work out the window.
Will SEP 04, 10:27 PM

quote
Originally posted by Bloozberry:

So ever since then, I've been trying to find a solution that minimizes having to go back to the drawing board. I tried every conceivable way to package the rod end differently and keep the same configuration of the links but it doesn't look like it's possible. So the next thing I tried was to swap the angled link to the back and the true lateral link to the front. This would work since the upright part of the knuckle is offset towards the front of the car giving me the room I need for the angled link towards the back, like this:



That looked very promising until I realized that it would adversely impact the direction of toe gain under jounce, effectively making the car oversteer. I didn't want that after all the effort to make this car handle correctly.

At the moment I believe the easiest way to fix the problem is to make both upper links parallel to each other and make them both true lateral links, like the lower ones. I'll keep them the same length as the original upper aft link so no other parameters except toe gain should change. I'll lose toe gain throughout the suspension's travel, but that's better than having the toe go negative. Also, having one upper link angled was a way to triangulate the upper portion of the knuckle over a larger area, making it less susceptible to unwanted movement at the top of the knuckle. Having the upper links parallel to each other will impact that characteristic somewhat, although I don't think it's that critical since the top of the knuckle in the stock Fiero only has the single strut mounting point, plus whatever side to side resistance there is in the spring to keep it from moving or twisting. Anyone see things differently?

Tomorrow I should get my rod ends in the mail... that'll help me mock things up so much more easily. I'll work up a new drawing showing my latest concept and post it tomorrow.



A) Lower the knuckle end of the problem link so that it bolts to the knuckle via the lower bolt instead of the upper. Can you keep sufficient anti-squat with that configuration?

B) Having the upper links AND lower links set the toe complicates adjustment. Are you sure that the upper link can affect toe in jounce while the lower links remain rigid? VAG uses a 5 link front suspension on the B5 and C5 (and maybe newer, I don't know) bodies. The configuration results in enormous caster change over the range of steering travel. Look up info on that design, as it's conceptually similar to what you're doing. Also, here's some Honda discussion regarding a similar rear suspension: http://world.honda.com/news/1997/t970702b.html

C) Having the upper link behind the axle as drawn will result in poor anti-squat at ride height and divergent (meaning it gets worse) anti-squat as the suspension compresses.

D) With the two upper links parallel, the knuckle will be free to flop fore and aft around the aft pivot of the lower trailing arm.
RCR SEP 05, 07:36 AM
I suppose a bigger wheel is out of the question...

Bob
ccfiero350 SEP 05, 08:24 AM
Have you thought about just swapping left and right knuckles? It would move the strut centerline back and give you more room for the upper fore link.

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yellow 88 GT, not stock
white 88 notchie, 4 banger