Rear control arm bush alignment

[ToolBoy]

Aaaah. . . The forensic aspect of obsessively restoring and ultimately understanding a 50 year old sports car. Will be a real thrill to finally drive this sucker with what I'll  know by the time she's road worthy. 

[grannyknot]

I haven't tried this yet but some guys have started using 5/8" x 12-14" bolt instead of a $40 spindle pin. Using the rubber and steel washers as usual but with no need for the anchor/tapered bolt in the center.

[zKars]

 

16 minutes ago, grannyknot said:

I haven't tried this yet but some guys have started using 5/8" x 12-14" bolt instead of a $40 spindle pin. Using the rubber and steel washers as usual but with no need for the anchor/tapered bolt in the center.

Many of the after market control arms that use 5/8 heim joint ends use a bolt like this. It’s a slightly loose fit in the stock application (stock pin is 16mm), just make sure you use a self locking nut and check it often. With no lock pin, if that nut falls off..... 

Edited July 11, 2020 by zKars

[Captain Obvious]

9 hours ago, ToolBoy said:

The forensic aspect of obsessively restoring and ultimately understanding a 50 year old sports car.

LOL. I think I do a lot of that. Probably more than I should. Haha!

Good luck with the project and hope it turns out well. My PO installed suspension was a total mess when I got my Z. I've since redone everything, and man.... Is it 1000 times better than before. Other than some steering wheel vibration at highway speeds (comes and goes), it's a pleasure to drive! 

[Captain Obvious]

4 hours ago, grannyknot said:

I haven't tried this yet but some guys have started using 5/8" x 12-14" bolt instead of a $40 spindle pin. Using the rubber and steel washers as usual but with no need for the anchor/tapered bolt in the center.

I've heard peopled talking about that in the past, and I'm not going to throw my body in front of anyone's train, but I think it's a bad idea.

Clearance (gaps) are an enemy, and Carroll Smith says that bolts are strictly for clamping, not for anything else.

I'm not a ME or a suspension expert, but I wouldn't do it. I've been known to substitute and modify stuff all over the place, but that isn't one of them.

[ToolBoy]

Yeah, I think I'm in agreement with Captain Obvious on this one although I'm clearly a much less developed, lower life form that resides way down on the food chain . That very tightly fitted, locked in spindle pin is screaming "I'm done this way for a reason". If I ever need a new one I'll fork out the 40 clams and pack my lunch for a week.

[ToolBoy]

. . . note to Captain Obvious. . . In my opinion (and my very, very personal, personal experience) the forensic analysis is what elevates it from 2D to 3D chess.  Identifying what the PO did and what aspects of that did or didn't work. ( and you get to berate him for it and be righteous which is always fun). The fact that you would imagine that Japanese conversation in 1969 is so awesome!!  I'm a finish carpenter and cabinet maker by trade and I've done a fair bit of structural wooden boat repair ( frames, planks, decks, garboards, shaft logs etc) and my favorite part is that analysis. I bought a 33 foot sailboat and when the glue-line broke on the 48 foot box constructed fir mast the PO stitched it up with stainless steel screws rather than ripping out the glue-line, cutting a spline and re-gluing. Potential point loading with a screwed joint on a flexible spar / bad idea. Figuring that all out is the fun part. (my opinion again)  

[ETI4K]

I am always averse to changing an engineer's decision unless I know everything that went into the taking of that decision.  The problem is usually understanding all the loads and in this case, knowing how the spindle was specified, metallurgically. 

If one were to remove the head and threaded end of the 5/8 bolt, they'd have a pin.  Could be a pin for a shear application, as most pins are.  It's fair to say, I think, that the failure mode for the spindle pin would be a double shear, or maybe a single shear with a moment.  Exactly the kind of loads pins are made for.  You can select the grade of that bolt/pin, 3, 5, 8, etc., and if you know the strength of the spindle pin, can do so to match.  Other than that you have to rely on anecdotal evidence, and the problem with that is you never know all the facts such as static loads, impact forces, installation details, etc. that the part has experienced.

My favorite example.  Please bear with me a moment: We used to ship very expensive equipment upright, which meant it had to go by 747 freighter, which was expensive.  Manufacturing wanted to ship it on its back, something it was never designed for.  So one day they laid one on its back and shipped it somewhere and back again.  It came back fine (looking) and so they declared the equipment could now be shipped flat, since they'd proven it worked.  Scary.

I believe we've all done things where we thought this will probably work, and it did!  Does that mean it's a good idea?  You'll never know.  All you can say is, "Well, it hasn't failed yet."

Purely for the fun of it, I am making new pins on the lathe.  I too will be holding my breath for the first few miles. ?

Edited July 12, 2020 by ETI4K
Added a point

[Namerow]

21 hours ago, Captain Obvious said:

Lead Engineer says : "Crap (in Japanese).  I really want to keep those washers. Make the bushings asymmetric and make sure you let documentation know about the change because they'll have to describe how to put the bushings in correctly!"

And that last part never happened. I wasn't there for any of it, but that's how I see the whole thing.   

Interesting that the section-view drawing of the installed bushing remains unchanged in the FSM's all the way from the 240Z through to the 280Z (i.e. shows a symmetric bushing and a rubber washer on both the inner and outer sides of the control arm pivots, making for a total of 8 rubber washers in the design).  The Parts Manual, on the other hand, shows the rubber washer only on the outer sides of the control arm pivots and states the number of rubber washers as '4'. 

Given that disassembly of the rear suspension would have been a relatively common (and time-intensive) job for Nissan dealers' service departments, it seems curious that the service techs were apparently left to discover the asymmetric bushing design on their own and then correctly interpret the implications for correct installation.  I wonder if anyone has a photo of the Nissan OE part that would help verify that the bushing was assymetric right from the start. 

[Captain Obvious]

9 hours ago, ToolBoy said:

and you get to berate him for it and be righteous which is always fun.

No, not at all. I'm imaging a conversation like that because I've heard it a thousand times in the engineering department. You're rushing around near the end of a project and some little issue raises it's head... You have to make quick judgment calls between project schedule, cost, and result quality. It happens and I'm not berating anyone. I've been there many times!

The only thing that really went wrong (in my imagined scenario) is the memo to the documentation group informing them of the change didn't make it. Or maybe even that did, but they decided that since they already had 10,000 books printed up, they would fix it in the next rev. And maybe THAT didn't happen.  

[Captain Obvious]

2 hours ago, ETI4K said:

My favorite example. 

Haha!!  "He hates these cans!!"

[zKars]

I’m not so concerned about the slightly sloppy fit of a 5/8 bolt as remember the strut and bushing core tubes are torqued together by the bolt/pin and locked solid to one-another.  The bushing rubber provides ALL the rotation at this joint. That’s why you torque this together with the car on the ground and driver weight in the seat. You want the rubber at its neutral position most of the time in use.  The locking cross pin provides a way to prevent the spindle pin from rotating while torquing (you can do either end independantly without using the other end as a backup) and is a fail safe in case all the nuts fall off.

I also just inspected a half dozen old crusty control arms that still have the bushings installed to see where the center bushing tubes have come to roost left/right offset wise after years of use, to see if the initial offset made any difference other than assembly with the strut housing ease. What I found was a bit surprising.

The front bushing clearly shows the center tube still offset toward the outside of the control arm, but the rear bushing tubes where all darn close to centered now, maybe just a tad offset to the outside. Not sure if 6 controls arms is a representative sample..... A testament to the dominant direction of travel and forces applied differently? 

One set of new bushings I have laying around has the offset center tubes. No clue as to vintage. I have a set to install today, I’ll use the advice and experience detailed above. Thank you.

 

Edited July 12, 2020 by zKars