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 Post subject: Re: 1966 Volvo 122
PostPosted: Fri Sep 04, 2015 9:38 pm 
Somehow completely sideways in 4th

Joined: Mon Aug 06, 2007 10:27 am
Posts: 209
Location: edm
Ugly Duck wrote:
Another way of looking at it is that a car with a high roll center will have some of the cornering forces go towards lifting the car. Force vector diagrams will show this. A car that lifts up as it rolls can be seen to roll from a higher point than a car that sinks down when it rolls, I think.


Yes, there are some pics of 2CV's racing that seem to show the very low roll centres actually sucking the car to the ground. That was interesting. And yes the force vectors suggest that would actually occur.

Since I'm on a quoting people jag, here's Greg K from the locost forum, casually speaking of that, and I saved it, as his explanation had me finally getting it clear.
Quote:
GregK:
Tire forces act on the sprung mass along a line of action from the tire contact patches to the roll center and through the magic of physics, geometry, and math you can consider it a single force acting at the roll center creating a torque around the cg (which is what your link is talking about). But if your roll center is anywhere other than ground level the forces being exerted on the roll center aren't purely lateral, part of that force is vertical. Remember the force is acting along a line of action, if that line isn't perfectly horizontal then neither is the force. Mathematically, when you apply that non-horizontal force at the roll center you have to break it down into two separate forces. The one causing a torque around the CG is perpendicular to a line from the CG to the roll center, ie: horizontal. What's left is a force acting along the line between the roll center and the CG, ie; vertical.

If your roll center is above the ground that vertical force lifts the sprung mass (Jacking). If your roll center is high enough, the jacking force created will lift up the sprung mass of the car to the point that the increased weight transfer will cause the car to roll over. This is part of why Ralph Nader loves Corvairs so much.



Ugly Duck wrote:

A car with low roll center doesn't generate as much camber gain


Not sure that's true... in fact, with double a-arms the opposite is more likely. (Note effects in my sample suspension linked in the last post of the Locost thread. I'm sure it's flawed, but it's build to my current level of understanding. I'll try to link it here, My link

I know picking at low hanging fruit, as far as advancing the discussion. Sorry.


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 Post subject: Re: Suspension Discussion
PostPosted: Sun Sep 06, 2015 12:44 pm 
Haha, I just built a W24 Octo-Turbo, now what?!
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Joined: Wed Dec 21, 2005 8:40 pm
Posts: 3413
Location: Calgary, Ab
You're right, Ian - that last bit isn't the type of generalized comment I want to be known for.


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 Post subject: Re: Suspension Discussion
PostPosted: Wed Sep 09, 2015 7:53 pm 
Somehow completely sideways in 4th

Joined: Mon Aug 06, 2007 10:27 am
Posts: 209
Location: edm
Sorry- didn't mean to take it out of context, just checking you weren't seeing something I wasn't, and that I was fairly sure wasn't "as I understood it to be".

The V-susp program, and my info entered there in the link, were/are to build in a front end swap on a Suzuki Sidekick.
It's what I've been driving the last several years. It's been that long since I had a second car insured. :(

It has some handling quirks and a reputation following it around. The Samurai's tended to fall over in a strong wind, if you believe Consumer Reports, and Suzuki NA were idealistic enough to fight that to the bitter end. Contrast that with say Toyota who threw billions of dollars away just to ... anyway don't get me started.

I put in springs from a 2dr non-AC veh from the wrecker, it being a 4dr with AC. Lowered it not much more than an inch, but got rid of the buckboard ride empty. It's never rolled much in corners, before or after (slightly more after) the spring change. But I did a bit of an emergency maneuver shortly after putting in the softer lower springs and it really felt like the outside front corner was digging in. Not sure how else to put it.

Compared to the 544 with the IPD bars, it still rolls way less. So it has a much higher roll center. I learned a bit about that and got an understanding of the compromise made. I've had the idea to go to a mostly Lexus IS250 AWD front end. Still using the Suzuki LCA's and springs, swaybar, and steering. This would result in a lowered roll center and I'd set it up with significant camber gain, vs the none of the present Mac strut. That's the V-susp model. May need a doubled sway bar after, too.

The two downfalls of the 544 toward the end of the time I was driving it were lack of straightline stability (lack of rear axle location accuracy, and the body catches winds and the narrow track catches road grooves like crazy) *plus* extreme harshness over frost heaves.
Dropping roughly 30% out of the rebound damping of the rear shocks, and redoing all the bushings, were the next steps. Unfortunately I can no longer jack it up safely, so it's parked.

The 122's may have better straightline stability, and even the 544 was pretty damn good at one point. The OE replacment bushings sold by most vendors are black crap cast in someone's basement with no knowledge of proper automotive rubber. I'm a little bent on that, as in their own way they were what took the car of the road.

Anyway not too much theory on my mind tonight. I do want to go back and reread, still.


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 Post subject: Re: Suspension Discussion
PostPosted: Thu Sep 10, 2015 7:30 am 
Haha, I just built a W24 Octo-Turbo, now what?!
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Joined: Wed Dec 21, 2005 8:40 pm
Posts: 3413
Location: Calgary, Ab
I didn't take it poorly, Ian - you were keeping me honest there, thanks.

My 122 isn't the best down the road either, the rear end seems to take a while to "set" and once it does it seems to take a conscious effort to get the car to stop steering. I haven't figured out if this is a trait from the earlier '66 suspension, I don't really want to have this in my '67. I've rebushed mine, Olof sent me a bunch of bushings in sealed Volvo bags, so these should be less than crap. The lower arms are all poly, being custom parts built out of necessity. The panhard rod is also poly bushed, and had to be lengthened to get the axle centered. From what I understand, typically the panhard rod needs to be shortened in these cars, so something may be bent (the panhard rod was one bent component when I got the car). If the axle is slightly bent (I haven't checked) that would account for the slight instability. That's another thing I should probably do this winter...

The sidekick sounds like a pretty strange windmill to tilt at. You're not exactly a normal guy, though. You're still building that half-Boss engine for this?


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 Post subject: Re: Another 242 project
PostPosted: Thu Oct 29, 2015 12:55 pm 
Haha, I just built a W24 Octo-Turbo, now what?!
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Joined: Wed Jun 14, 2006 4:19 pm
Posts: 3045
Location: Lethbridge, AB
I just talked to Bilstein USA and after some checking they will revalve my DeCarbons and will not revalve the Suburban rear shocks. They need make/model/year/spring rates (wheel rates probably and frequencies), suspension mods and intended use and they'll contact you and discuss what they're doing. So now I have to find another set of rear HD's - let me get this done and then I'll report back so you have some idea how much fun this is in reality.

I'll be going with 350/200 for my front and rear spring rates and will have roll correctors etc just like your set-up.

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 Post subject: Re: Another 242 project
PostPosted: Thu Oct 29, 2015 1:33 pm 
Haha, I just built a W24 Octo-Turbo, now what?!
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Joined: Wed Dec 21, 2005 8:40 pm
Posts: 3413
Location: Calgary, Ab
Why won't they do the Suburban shocks?


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 Post subject: Re: Another 242 project
PostPosted: Fri Oct 30, 2015 10:12 am 
Haha, I just built a W24 Octo-Turbo, now what?!
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Joined: Wed Jun 14, 2006 4:19 pm
Posts: 3045
Location: Lethbridge, AB
Ugly Duck wrote:
Why won't they do the Suburban shocks?


They just won't - according to JVAB, the tubes are swaged not clipped and they also don't want to touch OEM stuff. Aftermarket stuff is OK. So everyone's now been warned.

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 Post subject: Re: Another 242 project
PostPosted: Fri Oct 30, 2015 11:30 am 
Haha, I just built a W24 Octo-Turbo, now what?!
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Joined: Wed Dec 21, 2005 8:40 pm
Posts: 3413
Location: Calgary, Ab
*confused*

ALL of their shocks are aftermarket, except for ones that come on TRD off-road packages and things like such. Or I guess by "aftermarket" you mean things like coilover bodies and racing shocks.

I guess that nails down what I will be doing for rear shocks on the 122, if that's the case. Shitty, they were one company who seemed to give a damn about servicing and customizing their own product, but I'd heard whisperings of this decision being made and never researched it for myself.

It seems to me that the Suburban rear shocks are still suitable for a lowered 240 - maybe not perfect, but a stiffer tuning option for (all) your cars... no?


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 Post subject: Re: Another 242 project
PostPosted: Fri Oct 30, 2015 3:12 pm 
Haha, I just built a W24 Octo-Turbo, now what?!
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Joined: Wed Jun 14, 2006 4:19 pm
Posts: 3045
Location: Lethbridge, AB
Ugly Duck wrote:
*confused*

ALL of their shocks are aftermarket, except for ones that come on TRD off-road packages and things like such. Or I guess by "aftermarket" you mean things like coilover bodies and racing shocks.

I guess that nails down what I will be doing for rear shocks on the 122, if that's the case. Shitty, they were one company who seemed to give a damn about servicing and customizing their own product, but I'd heard whisperings of this decision being made and never researched it for myself.

It seems to me that the Suburban rear shocks are still suitable for a lowered 240 - maybe not perfect, but a stiffer tuning option for (all) your cars... no?


If it is an HD made by Bilstein they will service them. No problem. If it's a Delco made with their technology and painted yellow and has a black instead of a blue boot and sort of looks like a bilstein and probably is, then they won't touch them. Like the stock shocks on a C4 Corvette. If you bought a set of HD's for the car, you're fine - but the stock "Bilstein" shocks are Delco's and have a top that they can't remove easily. I've also read that they don't tinker with this stuff as they are a race shop and don't really want a bunch of stock junk. Their HD's are rebuildable for life, the Delco's are use and toss technology.

We could move this out of Jordan's thread maybe.

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 Post subject: Re: Another 242 project
PostPosted: Fri Oct 30, 2015 3:32 pm 
Haha, I just built a W24 Octo-Turbo, now what?!
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Joined: Wed Dec 21, 2005 8:40 pm
Posts: 3413
Location: Calgary, Ab
Ohhhh, that clears it up. I didn't know GM offered such a thing, and that you ended up with a pair.


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 Post subject: Re: Suspension Discussion
PostPosted: Thu Jan 24, 2019 10:55 am 
Haha, I just built a W24 Octo-Turbo, now what?!
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Joined: Wed Dec 21, 2005 8:40 pm
Posts: 3413
Location: Calgary, Ab
In an attempt to revive this topic a little, I'll submit a few videos.

Everyone knows you need to start at the tire, so start at the tire:

https://www.youtube.com/playlist?list=P ... puoavxGT3I

Suspension stuff:

https://www.youtube.com/playlist?list=P ... u0hl_Cs82g

I ran across these this morning: a really good trio of suspension/steering basics that don't go into such a deep level - really well explained:

https://www.youtube.com/watch?v=VbReLNi2JP4
https://www.youtube.com/watch?v=oh535De4hKg
https://www.youtube.com/watch?v=YVisLuiU-Oo


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 Post subject: Re: Suspension Discussion
PostPosted: Tue Jan 29, 2019 10:53 am 
Haha, I just built a W24 Octo-Turbo, now what?!
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Joined: Wed Jun 14, 2006 4:19 pm
Posts: 3045
Location: Lethbridge, AB
The tire ones must have been early Kyle videos before YT went to longer format. It all makes sense except a little at the end. He lost me there when he got all engineer and went off explaining how an equation explains a force. It's just a pet peeve - equations don't do that - they express physical relationships, they have no understanding on their own.

Tires are also the biggest black box because you can't get or derive most of these data. I've even called up BF Goodrich and had a chat with a tire tester/engineer about autocross tires. That's when I learned why I had to run very high pressures and that getting heat into a street tire isn't a "thing" as they have max grip from cold (assuming ambient isn't 5°C or something) - they wash away due to heat sooner than a race tire would.

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Coburn Performance - OCD comes naturally.


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 Post subject: Re: Suspension Discussion
PostPosted: Tue Jan 29, 2019 1:09 pm 
Haha, I just built a W24 Octo-Turbo, now what?!
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Joined: Wed Dec 21, 2005 8:40 pm
Posts: 3413
Location: Calgary, Ab
I'll admit I haven't watched the whole of either of his series on suspension or tires, I have watched a few of each and unlike the Engineering Explained guy, Kyle actually seems to know what he's talking about so I assume the rest of them are good.

And yes, it's pretty frustrating how secretive the tire manufacturers are. I've had a conversation with the Goodyear folk and they won't release any data even on obsolete tires. Even rudimentary data would help immensely, but we're left to work within generalizations. Fortunately from a practical sense we don't really need that data, and some experimentation will give results that satisfy our requirements. I would just like to understand things better.

*begins dreaming about building a tire test rig*


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