Front Flex

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Peter Connan
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Front Flex

Post by Peter Connan » 18 Jan 2013 18:46

Pretty much ever since I got my Patrol, I have been thinking of/investigating ways of increasing the front flex to compare more equally with the rear, on the basis that more of a good thing must definately be a good thing.

Effectively, and as I am sure most of you already know, front flex is limited by the two bushes in each lower control arm fighting against flex all the time. This is bad for flex, but at the same time probably a large contributor to the Patrol's relatively good road manners when compared to the Wrangler, which is about the only production live-axle, coil-sprung 4x4 with a different front suspension layout offering markedly more flex.

Pretty much all the othrer live-axle 4x4's currently on the market have the same type of front suspenios layout, and fairly similar flexability on the front axle (there may be minor variations, but nothing spectacular).

So far I know of four systems that could offer substantially more flex, some of which are relatively simple modifications while others are a lot more complex. These are, in no particular order:
1) Superior Ingineering's Superflex arms.
2) Five-link suspension system.
3) Four-link suspension system.
4) Dobbin Xlink.

My thoughts on each are as follows:
1) Superflex:
This is the simplest system to install, and requires no permanent vehicle modification at all. It works by effectively moving the bushes closer together, thus reducing the deformation of each bush for a given flex angle. It also allows caster correction without the need for special offset bushes. A full installation (with superflex arms on both sides) will probably out-flex any shocks mounted in the standard mountings and assuming a lift of 100mm or less. However it is relatively expensive, particularly if you import it, and it is patent-protected.
Furthermore the road handling is affected to a degree (although most users claim it's not too bad), and I am a little bit concerned about axle tramp.
2) Five-links:
This effectively is modifying the front suspension into a similar layout to the rear suspension. It will allow massive amounts of flex (assuming you find a way of fitting long enough shocks) and is fitted on many competitive rock-crawlers. However I have not come across a bolt-on kit for the Patrol, and from what I can see substantial vehicle modifications are necessary, including welding brackets onto both the chassis and axle. Also, since there is very limited room on a Patrol for this, and most of these systems are home-made lashups, they frequatly result in a vehicle that handles terribly on the road. This will definately require a fairly beefy anti-sway bar to keep the car reasonably road-worthy, sort-of negating the whole exercise unless quick-disconnects are used)
3) Four-links:
I have only ever seen these on competitive pipe-car type vehicles. The system consists of two lower control arms running approximately paralel, and two upper control arms converging sharply. The convergence effectively negates the need for a panhard rod, but the joints need to be close-tolerance ball joints and rubber bushes will not work. In terms of performance and flexability, nothing (except maybe the torque-tube setup on the Unimog) will touch this, but the penalties are severe. Due to the relatively solid joints, maintenance is high and a lot of road noise is transferred to the car. Also there is limited space in a Patrol for this, and particularly so since the entire steering system needs to be re-designed if bump-steer is to be kept within reasonable limits.
4) Xlink:
Apart from Superflex arms, this is the only system I know of that is available in kit form. It works by removing the two front bushes's mounting points from the axle, and instead fitting a bar linking them together. This bar is pivoted to the axle in the middle. Thus when one arm moves up, the other is pushed down. Flex thus occurs with very little deformation in the bushes, and thus the axle flexes very easily. However, total flex is limited (to about 20 degrees) as the arm will eventually interfere with the panhard rod. Fitting the current commercially available kit is a matter of welding the arm's pivot pin to the front axle, in the correct place, and then grinding off the current front bush mounting holes from the axle. The current commercial kit can also be ordered with a lock-out pin which will lock the arm in the horizontal position, and when this is fitted road handling will not be affected at all. If the lockout pin is not used, body roll wil increase but there should not be any effect on axle tramp. By carefull placing of the pivot pin (or special arm geometry) the use of caster-correction bushes can also be avoided on lifted cars.

However, there is another factor limiting suspesion flex, and that is the amount te front shocks can extend. From extensive fiddling with a 3-d model I have developed, I suspect that the standard shocks will not allow much more flex than the standard control arm bushes, and I have no idea yet what effect standard suspension kits (such as OME etc) will have on that, although it seems that the OME shocks are only about 16mm longer than standard and have about 5mm more travel. However I suspect that any of the systems described above will out-flex any normal shock that can be fitted to the standard mounting points. Thus to gain the full advantage will probably require further modification.
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Re: Front Flex

Post by Peter Connan » 19 Jan 2013 12:05

:rolling: I tried to flex my car this morning to measure how much room I have for longer shocks, and to this end tied the high-lift jack to the front wheel (like a wheel-buddy). I have the long 60" hi lift jack, and jacked it up all the way to the top, but still had three wheels on the ground... :rolling:

Anyway, watch this to see what an X-link can do: http://www.youtube.com/watch?v=W2ZxbfIPgIY
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Re: Front Flex

Post by Aries66 » 20 Jan 2013 12:45

Peter
Nogals baie insig gewende artikel. Het self ook al gewonder hoe gemaak meet die voorste as.
Die link na die youtube sukkel wil nie oop maak nie.

Groete
Louis

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Re: Front Flex

Post by Peter Connan » 20 Jan 2013 18:17

Louis, it works on mine? Anyway, go to youtube and search for "daves gq flexes and drives..."

Groete
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Re: Front Flex

Post by Marino4x4 » 21 Jan 2013 08:58

Hi Peter

Very interesting. As you know, with a suspension configuration it got it's advantages and disadvantages. You will win flex, but will loos road holding ability. It is the balance between thees two elements that one need to get to have the perfect suspension setup for your car. The guys with the mega flex, like the one in the video, probably uses their cars just for playing around in the rough stuff. It is not a car for driving from Jhb to Cape Town, on or off-road. My feeling is that they will never drive more than 80Km/h with a car like that. On the other hand the standard configuration of the Patrol is for fairly rough stuff and on road driving at speeds more than the speed limit, safely.

I am not to familiar with all the configurations you mentioned. The advantages of all off them is more flex, but at what price? Will you still be able to use you car as an over-landing vehicle, or will it just be a rock crawler type car. It is a bit of an expensive experiment.

Just my :mytwocents: :mytwocents:

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Re: Front Flex

Post by Peter Connan » 21 Jan 2013 19:08

Marinus, the car on the video has the so-called Xlink. One of the nice things about this particular setup, is that this device now comes with a lockout pin. When the lockout pin is engaged, the link is efectively disabled, and then the suspension react exactly like the standard suspension. In other words, roadholding is not compromised at all when the link is locked.
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Re: Front Flex

Post by Kagiso II » 21 Jan 2013 19:22

Hou die flex wat dit is -- sit 'n diff lock voor in ??
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Re: Front Flex

Post by Peter Connan » 21 Jan 2013 19:25

Ok, I finally managed to find a place where I could flex my suspension to maximum, and then take some measurements.

Firstly, the specs: my car is fitted with OME suspension of unknown specification. However, the two shocks that OME fit to the front of the Patrol are identical in terms of length and stroke, and are 16mm longer in the extended position than standard shocks, and have 5mm longer stroke than standard shocks. I also do not have an anti-sway bar on the front axle.

With the suspension flexed as far as it wants to go under vehicle weight alone, the extended front shock is within 5mm of it's maximum extension, while the compressed shock is 40mm from being fully retracted. IT is also fairly solidly in contact with the bump stop.

In other words, without changing the shock absorbers, I would gain virtually nothing in terms of flex. Also, I have so far been unable to find shocks with a longer stroke that are not longer when compressed (and thus risking damage from solid contact). Therefore, to fit shocks with a longer stroke, I would have to move the top shock mounts.

I have therefore decided not to do anything further to my car until such time as I need to replace the shocks anyway.

For referance, the front end of my car flexes about 8.5 degrees, and the rear end flexes about 17 degrees. Total wheel travel (the difference between ground level on the two sides) was about 740mm.
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Re: Front Flex

Post by Peter Connan » 21 Jan 2013 19:35

Kagiso II wrote:Hou die flex wat dit is -- sit 'n diff lock voor in ??
Oom Mac, that's another discussion with lots of pros and cons. This is my opinion, and only mine: Even flex at front and rear results in a better balanced vehicle that is less likely to roll over on a steep but uneven downhill, such as for example coming down the rock at Moegatle. More even traction also means more even driveline loads and thus less risk of breakages. Thirdly, it will not affect your turning circle. And lastly, you don't have to remember to switch it on.

The main advantage of a front locker over added flex is that more flex doesn't really help when the lack of traction is due to factors other than uneven terrain, such as when one wheel is in a mud pool or on ice.

But the slammer is this: I reckon building an x-link (not including the cost of new shocks, but including the cost of extended shock mounts) will cost less than a quarter of the cost of the only selectable locker available for the Patrol.
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Re: Front Flex

Post by Wheels » 22 Jan 2013 07:27

Yes the only way to extend the shocks is by increasing the shock towers, and that also has its limitations.

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