Rear control arm bush alignment

[Patcon]

Ahhhh, Jim's emporium. I will have to make a pilgrimage one day....

[ToolBoy]

12 hours ago, ToolBoy said:

. . . note to Captain Obvious. . .   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).   

I wasn't suggesting you would think of "berating" anyone in this situation but rather was referring to the many times I've uncovered repairs that were done without common sense or due diligence and were potentially unsafe, ticking timebombs. Structural boatwork, house remodel construction, both boat and house electrical among others.

[Captain Obvious]

Haha!! Gotcha. Well I would be happy to berate my PO.....

Here's a pic of the kind of PO handiwork I found on my car when I dug into the suspension.  Yes, those are huge gouges of missing and upset metal on the precision bushing surface. I'm thinking he split and drove the old bushing out with an air chisel. And heat. Lots of heat. Enough heat to blue the ends of the control arms.

 

[ToolBoy]

WOW!! . . .  reminds me of the old adage. . . . . "If brute force isn't working, it just means you're not using enough"   

[ToolBoy]

. . . or, turn it as far as it'll go. . . and then two more. . . . 

[ToolBoy]

Since you got to share. . .  now it's my turn. . . . This is what the inside of a water pump looks like when you park a Z for 17 years with the fluids left in. I can't wait to see the electrolysis between the head and the block. So exciting!  

[Captain Obvious]

Gross. Congrats, I think that's the worst I've ever seen.

Here's hoping the block and head don't look as bad!!   

[siteunseen]

Wow! That looks like a crustacean family has been living in there.

Can't wait to see pictures after you get the block's core plugs out, I like to get grossed out.

 

[LeonV]

On 7/11/2020 at 6:57 AM, Captain Obvious said:

Yeah, I think someone missed a detail somewhere. Everything about the whole situation would make much more sense for the bushing to be symmetric. Assembly process would be foolproof because you wouldn't need to pay any attention to which direction it went in. and the documentation wouldn't have to mention anything about it because it just didn't matter.

On the prototyping floor... "Hey Boss. I'm putting these bushings in and when I do that, I can't get the strut casting in between them. What are we going to do?"

Boss says : "Hmmm... I'll let engineering know."

Engineering says : " Oops. We'll need to either:"

a) Change the strut housing design to reduce the width.
b) Change the rear control arms to increase the span between the bushings.
c) Change the bushing so things fit together without interference.

And "changing the bushing is way cheapest and easiest to change, so lets do that."

Draftsman/Designer says : "I can't shorten the outsides of the bushings because we need that length for the rubber washers. Should we eliminate the rubber washers and make the bushings symmetric, or should we make the bushings asymmetric and keep the washers?"

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.   

It doesn't sound too far-fetched but I'd still be surprised if that were the reasoning behind the decision. How much are those bushings offset by? If it's a few mm's, my call would be to just machine the strut housing a tiny bit more and not worry about retooling bushings and having them become asymmetric. Perhaps the cost analysis showed otherwise.

It's not uncommon to offset bushings to account for pre-load or uneven travel but I don't see that being the case here. Especially because the bushings are offset in opposite directions when installed.

Edited July 13, 2020 by LeonV

[Zed Head]

Doesn't having the offset to the outside leave a gap for that little rubber seal/washer?  And keeps the nut off of the outer edge of the control arm.

Nissan spent a lot of time avoiding metal to metal contact.  If you look at all of the components in the rear you'll see that they're all suspended in rubber, separated from the body.  Just an extra view...

http://www.carpartsmanual.com/datsun/Z-1969-1978/axle/rear-suspension/69

 

[Captain Obvious]

4 hours ago, LeonV said:

It doesn't sound too far-fetched but I'd still be surprised if that were the reasoning behind the decision.

Haha! Yeah, we'll never know for sure. And of course, all this chatter about what we think was a mistake may have all been perfectly intentional from the very beginning for reasons we don't know. 

[ToolBoy]