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Mongo's rear suspension


MONGO510

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Hey fellows, I have removed the rear suspension from my totaled Z and I thought you may like to see it in its totality.

A few of you were having some trouble picturing how it worked so here are some pics of it.

This is exactly how it is as installed in the vehicle. The only thing missing is the floor of the rear deck to bolt it too.

Study the pics and its operation should be self explanitory.

 

This setup worked really well. It was overly built and in its next rendition it will be much lighter.

Here are some pics.

 

Mongo

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I am sorry to hear about your car, but I am glad that your son was not hurt.

 

I really like your rear suspension, but damn those are some huge heim joints at the top of the strut housing :blink:

 

 

Yeah, It is overkill to say the least.

 

Mongo

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Always good to see someone trying something but from what I can see if the suspension upright was made into a coil damper unit then all the other parts above it, except the upper control arm, would be superflous. Basically it looks like a over complicated double wishbone setup. Thanks for showing though :)

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Always good to see someone trying something but from what I can see if the suspension upright was made into a coil damper unit then all the other parts above it, except the upper control arm, would be superflous. Basically it looks like a over complicated double wishbone setup. Thanks for showing though :)

 

That wouldn't work...

 

Mongo, that is such a sweet setup!

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I applaud Mongo's efforts on this rear suspension set-up. The entire thing is over-built, but that was intentional on his part because this was a prototype. If you notice, he has built adjustability into every part of it so that the optimal design could be attained through trial and error. I would love to build a similar set-up based on his design that has been optimized for weight.

 

There are things that I would like to know:

 

What does the camber curve look like (how much gain per inch of bump and inch of droop)?

 

Where is the roll center?

 

If you don't know these, then perhaps I can help you determine them based on dimensions.

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That wouldn't work...

 

Mongo, that is such a sweet setup!

 

If it has inner and outer pivot points for the upper and lower suspension arms, which it looks like it has, of course it would work. A double wishbone suspension. But I'm not knocking what's been done, would like to know why it was done though and what are the advantages.

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If it has inner and outer pivot points for the upper and lower suspension arms, which it looks like it has, of course it would work. A double wishbone suspension. But I'm not knocking what's been done, would like to know why it was done though and what are the advantages.

I think the way you worded it initially you're basically saying you want to make the upright the spring. That doesn't work. You could put a spring in from the lower control arm (or base of the upright) to the frame like a Miata, I'm guessing that's what you meant, but your upright cannot be your spring in a LCA arrangement, because it would have to go to full bump on one control arm or the other before the spring would do anything at all.

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I think the way you worded it initially you're basically saying you want to make the upright the spring. That doesn't work. You could put a spring in from the lower control arm (or base of the upright) to the frame like a Miata, I'm guessing that's what you meant, but your upright cannot be your spring in a LCA arrangement, because it would have to go to full bump on one control arm or the other before the spring would do anything at all.

 

Exactly.

 

 

As 74_5.0L_Z points out, the rear suspension becomes fully adjustable and the camber curve is redesigned as well.

 

Plus, it's cool as hell! :2thumbs:

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SLA has (potentially) better camber control. It also has less stiction as the suspension moves in a turn, because the shock itself isn't side loaded like our struts are. By making his own pushrod linkage, Mongo has effectively made the rate adjustable, so he can make the spring and damper stiffer or looser by changing the size of the lever acting on it, and he can make the system digressive or progressive in function as well.

 

How much better is it? Well, if you get the geometry wrong it could easily perform worse. This certainly looks a lot heavier than the stock suspension too, so weight is another important factor. I'd be curious to know if the car was faster with struts or with this SLA pushrod setup and whether the difference was really noticeable from the driver's seat, or whether it could be discerned at all.

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From Mongo's build thread:

 

 

Mongo stopped by with his Mona Lisa today. He kindly offered the keys, so BRAAP and I took it for a short trip. A little more tuning and this car is gonna rip. But... but... but... the intriguing part is the rear suspension. An unfamiliar car with a prototype suspension demands some discretion, ergo the drive was decidedly cautious. However, I will say this... the only Z's I've driven that ride this good and deliver this much power, squat excessively... and Johns car does NOT. Definitely keeping an eye on this Z's future.

 

Two thumbs John! :2thumbs:

 

 

 

...The rocker arm rear suspension is wicked cool to watch in action. Must get a video of that. I spent most of the ride in the passenger seat staring at the rear suspension doing its thing through the bumps and turns. Ride quality was quite nice. Very little if any squat under hard acceleration in the lower gears.

 

Very cool ride, thanks for bringing it over John. :2thumbs:

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The Datsun suspension doesn't have any pro or anti squat, and neither does the SLA that replaced it since the control arms are still parallel to the ground, unless I'm missing something. So if the squat geometry is the same, then the lack of squat is probably due to the spring rate or compression damping on the shocks, which are two things you could change on the original strut setup without any trouble.

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Jon, I agree with you regarding the anti's. The connection I was trying to make (in my quoted post) was the relationship between ride quality and stiffness. Normally, a Z that holds itself up well, doesn't ride so well. I'm guessing the improvement that I felt had more to do with the dampers than geometry.

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My choice for a S30 would be along the lines of converting the existing strut suspension to a double wishbone setup. It has ben done before, it would not be much heavier and the design could incorporate whatever adjustable setup was required. Done reasonably well it would outperform the rest of the car.

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Jon, I agree with you regarding the anti's. The connection I was trying to make (in my quoted post) was the relationship between ride quality and stiffness. Normally, a Z that holds itself up well, doesn't ride so well. I'm guessing the improvement that I felt had more to do with the dampers than geometry.

 

I would see a couple of advantages to this. It should keep the tires flatter on the ground and if done correctly would have a roll center that moved with the car in a 1:1 relationship. Unlike the strut that moves at a different rate. I could see this making the car feel more stable in corners when putting power down or when trail braking. And I could see that making the car quicker just because the driver feels more confident.

 

Cary

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It's a pity that the designer is not here to explain the concept, makes it a bit of a dry argument. Anyway, from the pics it looks to me basically like a double wishbone suspension with bits on top to support and operate springs and dampers. If that is correct, then it's the alignment of the wishbones in relation to the chassis which determines the roll center and all the other alignment specs, the bits on top have no bearing on that.

 

If the designer would correct any misconceptions inherant in the above than I would happily try again :)

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