Front Flex

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Grant
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Re: Front Flex

Post by Grant » 01 Feb 2013 14:57

What would you want,

ARTICULATION OR LOCKERS

http://www.youtube.com/watch?v=QDwBER_HBBA
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Re: Front Flex

Post by Alex » 17 Jun 2014 13:30


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Re: Front Flex

Post by davidvdm » 24 Sep 2017 19:45

Cam I bump this thread please.... I am investigating "upgrading" my leafs to a coil setup. You could say I can start with a fairly clean slate with all the various control arm, and various multi link setups as options. But I have to keep in mind that I am driving mostly on road, but of course I would like some flex as part of the package.

This X-link looks like a nice option if you lock it up for road use. But I also see that the Patrol needs it because of the limitations of control arms. A three kink with panhard would give more flex. A four link takes up too much space and I think is too extreme for my needs.

I am leaning toward the 3 link, but the length of the arms take me right over my rockslider mounts, unless I go past the mount and add another 150mm to the lower arms length. Then I also need to decide on rubber bushes, or Heim Joints.

Whats the Patrol men have to say??
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Re: Front Flex

Post by Peter Connan » 26 Sep 2017 05:16

Heim joints will be a pain to live with. It makes a car extremely loud, clunky and harsh-sounding, and I don't think it's suitable for anything other than a racing vehicle or weekend toy.

And because a four-link setup is only accurate enough if heim-jointed, to my mind that excludes that setup for this application.

Which leaves three links (with or without the various modifiactions already mentioned), or five.

Three is easiest to package, five is better in terms of available flex (although a three-link with X-link will provide just about as much as you could reasonably want).

MAke sure you spend a fair amount of time on the drawing board to see what your chosen setup does to propshaft angles and lengths, and even more importantly bump-steer.

And I also want to say, please get any mounting points professionally welded. They will take much greater loads than mounting points for leaf springs.
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Re: Front Flex

Post by davidvdm » 26 Sep 2017 07:26

Thanks for the info Peter.

When I talk about a three link, I mean two lower arms, one upper and a Panhard bar, and not the radius arm setup like the Patrols. From what I have been able to find out/learn, the ideal setup is to get the instant center of the upper and lower arms to be just above the rear bumper, for my type of application. This gives fairly nice anti squat characteristics, but keeps the arms close enough to horizontal to limit bump steer. I think the limit is 7deg on the lower control arms. That is what Jeep uses.

Ideal chassis mounting would in line with where the propshafts leaves the transfer case. This would keep propshaft lengths fairly constant through it's dropout arc (depending on how the upper control arm causes the diff to twist). But I think that is very long, and leaves me with very heavy duty control arms, that could be vulnerable to rock damage.

Will rubber mounts not destroy themselves to quickly compared to Heims?

My biggest reasons for wanting to get away from the leaf springs, is the present harsh and unstable ride I have, and the lack of adjustability of castor angle. The spring guys are saying that to carry the weight of the Sani, I need to add another blade, and have the existing military wrap blade re done with bigger eyes that allow the movement of the second blade without binding as I now have.

Forces on the attachment points should not be mush different to what I have at present. A leaf pack carries forward and rearward forces on the chassis attachment point, with very little on the shackle besides the weight of the vehicle. (I'm open to be proven wrong of course).
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Re: Front Flex

Post by Peter Connan » 26 Sep 2017 09:26

Heims have no movement. Every shock load is transferred directly through the chassis. I think on off- road racers they are replaced vdry frequently. Rubber, on the other hand, is practically immune to shock loads. Assuming enough rubber is used, and used correctly to handle the maximum forces. This is converse to metals and polyurethanes.

Bump steer has nothing to do with the respective orientation of the lower and upper arms, and everything to do with the relationship between the panhard rod and the steering linkage.

Leaf springs absorb fore-and-aft loads far better than solid arms, because they are seldom exactly flat and even if the are, the roll on the end can flex.
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Re: Front Flex

Post by davidvdm » 26 Sep 2017 11:17

Again, some great information, thanks. I realise that the "bump steer" of big angle control arms are limited to situations where you are going very slow, and thus won't have affect.

What in the geometry could cause death wobble? That is my biggest fear, and I want to steer clear of that pitfall.
David - Bfreesani
1997 Nissan Sani MK3 2.7TD - Hillbilly (SAFANI)
MQ C200 SFA
MQ H260 LSD Rear
MQ Transfer as second low range
5" Lift
33"x12.5x15" tires on 8.5J rims - Want 35's
DIY rock sliders
DIY Snorkel
Madman EMS

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Peter Connan
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Re: Front Flex

Post by Peter Connan » 26 Sep 2017 15:00

Any un-controlled motion effectively has the potential to cause death wobble or similar symptoms.
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