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4 link v 3 link

Posted by tdrrally 
tdrrally
edward mucklow
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4 link v 3 link
May 23, 2016 11:29AM
long term planning aon the mustang

i'm looking at a parallel link ie some many volvos 240s mod or a 3 link.

the 3 link looks to have better articulation, but the 4 link seems to be very popular with the rally crowd.

any thoughts?



I would rather drive a slow car fast as a fast car slow!
first rule of cars: get what makes you happy, your the one paying for it!
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tdrrally
edward mucklow
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Re: 4 link v 3 link
May 23, 2016 11:51AM
i find this quite inspiring

http://www.motorsport-tools.com/ford-escort-parts-mk1-mk2/rear-suspension/4-link-kits.html



I would rather drive a slow car fast as a fast car slow!
first rule of cars: get what makes you happy, your the one paying for it!
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john vanlandingham
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Re: 4 link v 3 link
May 23, 2016 12:02PM
Quote
tdrrally
long term planning aon the mustang

i'm looking at a parallel link ie some many volvos 240s mod or a 3 link.

the 3 link looks to have better articulation, but the 4 link seems to be very popular with the rally crowd.

any thoughts?

Yeah.
I only see people advocating 3 link only in America and only from America V8 heroes..

The entire rest of the world seems to struggle by ---and go waaaaaaaaaaaay faster and harder somehow---with simple 4 link plus panhard...



And where rules allow it---and that varies---using as long a link as can be fitted...

(One glaringly obvious problem that the V8 hero advocates of 3 link never seems to address is making room for the shit on top of the diff......evidently chopping up the trunk floor and figuring out where to secure the car end --which just happens to be in the middle--right where the propshaft is----is of no concern)

So one is a well proven design used with startling success world-wide from the late 1960s to present, the other a claimed "brilliant solution" that by all evidence obvious only to a select few guys in one region of the world by a subset of people making other choices also unique and also clearly ineffective--V8s..


Go find results from last year's New Zealand Rally Championship round at Otago. Run concurrently same roads same stages and full length was NZRC for Historic cars..
a carburettoed 1,6 liter RWD car driven by Haydon Paddon, a young guy, won the event OVERALL.
4 link + Panhard (and leaf springs)

Beat every single modern long travel turbo 4wd car..

Proof that it is do-able and good enough..
An astute person would just scale up what he had.



John Vanlandingham
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john vanlandingham
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Re: 4 link v 3 link
May 23, 2016 12:05PM

Yeah, but bear in mind that that is for a car with a 94.5" wheelbase

As an example if you look in the shelves above the washer/dryer those links there for a car with 104" wheelbase are 28" long bar + the ends..

This is what has been done on quite a number of cars out here in the PMW going back almsot 30 years which work shockingly well--and are even "comfy" to drive on stages and work.



John Vanlandingham
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Pete
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Re: 4 link v 3 link
May 23, 2016 12:52PM
If you're starting from scratch, sure do a 4 link.

If you're working with a car that already has two 19" long parallel links and a Watts in front of the axle that would get in the way of four links, the three link makes sense. Especially if you want to play with antisquat because you're not interested in going fast, just getting good acceleration hook-up on rough shit and no waiting for axle tramp to die down before applying power.

MRTE went to "outboard" parallel upper links on the Group B RX-7, to get out of the way of everything else, which is also an option *for that chassis*.



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1978
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hoche
Michel Hoche-Mong
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Re: 4 link v 3 link
May 23, 2016 01:05PM
I have no idea which is actually better for rally (I lean toward 4-links myself), but I suspect people tend to go with the 3-link when they've got a car that already has a 2-link setup with angled-out trailing links, and a 4-link when they're converting from leaf springs.

The 4x4 crowd seems to like 3-links because it allows for some massive articulation, and the circle track guys seem to use 3-links for reasons I don't know but which probably relate to weight.



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mekilljoydammit
Daniel DeRosia
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Re: 4 link v 3 link
May 23, 2016 01:35PM
Parallel 4 links seem to work great on rally stuff, but if they're not parallel there's potential trouble. 3 links you can adjust in ways such that the upper link isn't parallel without it binding in roll, but whether messing with antisquat is worth the trouble is up for debate and not something I'm going to touch.

On some tube chassis thing where there's no concern about packaging, 3 links work pretty good, and on some specific unibody things too. Otherwise, whatever's easiest to package, which seems like usually a parallel 4 link with boxes and move on with your life, yaknow?
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Robert Culbertson
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Re: 4 link v 3 link
May 23, 2016 01:39PM
I like a 3-link for the simplicity (no need for Watt's or panhard bar), and it can accomplish the same squat as a 4-link (but suffers with anti-squat if that's what you want). Downsides are they require more room above the diff, and they generally have less adjustment than a properly thought out 4-bar. They also place the top center point in massive bending so it needs to be up-sized accordingly (off-road trucks are using 1in+ heims). You will also need a mount on top of the 8.8 case, so that's going to be either welded or a bolt-on gizmo.

With the lack of room under a fox-body, a long-link 4-bar or a long 3-bar could work. The floor needs to be modified either way.
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hoche
Michel Hoche-Mong
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Re: 4 link v 3 link
May 23, 2016 01:48PM
Which 3-link design doesn't need a panhard/watts?



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mekilljoydammit
Daniel DeRosia
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Re: 4 link v 3 link
May 23, 2016 01:52PM
If one of the "links" is a triangle.
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hoche
Michel Hoche-Mong
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Re: 4 link v 3 link
May 23, 2016 01:58PM
I don't get it. If you have an A-arm with two mounts on the frame and one on the pumpkin, I can see that you'd have no left-right tramp, but wouldn't it bind up under roll? If you have it the other way, with one mount on the frame above the driveshaft and the other two on the axle each side of the pumpkin, how would that prevent axle tramp?



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Robert Culbertson
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Re: 4 link v 3 link
May 23, 2016 03:03PM
You'll need rubber bushings so it doesn't bind, unless you can get all the links to pivot around the same point... which is near impossible and a terrible from a packaging standpoint.

Edit: This may actually be incorrect. You can use heims, but you get more rear-steer with the diff in one wheel bump. I think desert trucks get around this by running SUPER long links.



Edited 2 time(s). Last edit at 05/23/2016 03:19PM by Robert Culbertson.
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Robert Culbertson
Robert Culbertson
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Re: 4 link v 3 link
May 23, 2016 03:13PM
You can also do a triangulated 4-link, or a 3-link. Similar to desert racing trucks.
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john vanlandingham
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Re: 4 link v 3 link
May 23, 2016 03:31PM
Quote
hoche
I have no idea which is actually better for rally (I lean toward 4-links myself), but I suspect people tend to go with the 3-link when they've got a car that already has a 2-link setup with angled-out trailing links, and a 4-link when they're converting from leaf springs.

The 4x4 crowd seems to like 3-links because it allows for some massive articulation, and the circle track guys seem to use 3-links for reasons I don't know but which probably relate to weight.

Acceptable movement ---is a function of the length of the link..
ARCS!!!
they all move in arcs and the shorter the link the steeper the arc--think arcs and plumb bob the lengths horizontal then swing 'em up..
Length is everything..

And all the 4 link shit I get and supply comes from


CIRCLE TRACK where all I see is 4 link +panhard.



John Vanlandingham
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Remember! Pacific Standard Time
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hoche
Michel Hoche-Mong
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Re: 4 link v 3 link
May 23, 2016 04:37PM
So what do you do if you start out with this:





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