[HELP] 2 Link vs 4 Link Live Axles

[__________________________]

Why would someone use 4 links when 2 will make an alright live axle?

Is it just a matter of budget and 4 link is better? If so is that why 9398 is a 2-link setup on both axles?

[nastystage]

9398 is a false 2 links....don't forget the pivot ball (steering axles)

with 4 crossed links you don't need pivot and suspension works better

[__________________________]

9398 is a false 2 links....don't forget the pivot ball (steering axles)

with 4 crossed links you don't need pivot and suspension works better

Can you explain? what does the pivot ball do, how do you get rid of it.

[JJ2]

"2-Link" suspension is not as good as a 4-Link one because it has less travel, introduces a negative caster angel on the axle because when compressed it follows an arch making steering have more bump steer. 4-Link is much better because it can have MUCH more travel, and it does not follow and arch when compressed eliminating the variable caster.

I believe Lego used the "2-Link" suspension because it is much easier to build, and has less side to side movement.

Here are tow prime examples of the two different suspension types.

and

Hope this helped.

[nastystage]

Can you explain? what does the pivot ball do, how do you get rid of it.

2 links are not enough to set the suspension. You need something that prevent suspension from moving sideward.

The solution in real life cars is the panhard bar (something like 8110).

I really don't like 9398 setup , try to check some rc scaler

[__________________________]

"2-Link" suspension is not as good as a 4-Link one because it has less travel, introduces a negative caster angel on the axle because when compressed it follows an arch making steering have more bump steer. 4-Link is much better because it can have MUCH more travel, and it does not follow and arch when compressed eliminating the variable caster.

I believe Lego used the "2-Link" suspension because it is much easier to build, and has less side to side movement.

Here are tow prime examples of the two different suspension types.

and

Hope this helped.

2 links are not enough to set the suspension. You need something that prevent suspension from moving sideward.

The solution in real life cars is the panhard bar (something like 8110).

I really don't like 9398 setup , try to check some rc scaler

I had no idea about this, I took apart my 9398, I am rebuilding it.

You posted the same video twice.

How is 4 link harder to build?

Edited March 13, 2016 by TheLegoExpert

[Pego]

How is 4 link harder to build?

Because you have to attach 4 links onto both the axle and the chassis, taking up space and making the axle more complicated.

With the ball joint piece it's very easy to attach everything to it, and it doesn't take much vertical space.

Still 4 link suspension is always worth it for the realism and to avoid negative caster

[__________________________]

Because you have to attach 4 links onto both the axle and the chassis, taking up space and making the axle more complicated.

With the ball joint piece it's very easy to attach everything to it, and it doesn't take much vertical space.

Still 4 link suspension is always worth it for the realism and to avoid negative caster

can you link a picture of 4 link? would love to see. thanks

[JJ2]

You posted the same video twice.

You might want to check again

can you link a picture of 4 link? would love to see. thanks

Heres one

IMG_5270 by JJ2Sam, on Flickr

You can clearly see the top LBG beams and the Black Bottom ones.

[Sylvian]

Perhaps interesting,. I dont know if it qualifies as a triangulated 4link,.

Anyhow, i have used it quite alot. It works really well for me as its pretty compact, rigid and allows enough suspension travel/articulation.

the ones that use balljoints are better imo,.

Edited March 14, 2016 by Sylvian

[nastystage]

Try to check in the internet something like axial ax10

[__________________________]

You might want to check again

Heres one

IMG_5270 by JJ2Sam, on Flickr

You can clearly see the top LBG beams and the Black Bottom ones.

Perhaps interesting,. I dont know if it qualifies as a triangulated 4link,.

Anyhow, i have used it quite alot. It works really well for me as its pretty compact, rigid and allows enough suspension travel/articulation.

the ones that use balljoints are better imo,.

So if I am looking at this right, the higher up set of links point inward, and the lower set of links go out? Edited March 14, 2016 by Blakbird
: Removed quoted images.

[Pego]

The system Sylvian showed is teoretically not 4 link, but it functions the same

The upper links are narrow at the axle, the lower ones wide at the axle. (4 link)

The lower links don't actually have to be triangulated, but it helps for sideways stability

[AndyCW]

Four links can come in two varieties.

Triangulated and non triangulated.

Here is a link to some triangulated four links on a Lego rock crawler. (The pics are too big to post here.) The links are of the 9l type with upper links narrowing on the axle and lower links narrowing on the chassis.

http://imgur.com/a/5wB1X

Non triangulated four links need panhard bars or a watts linkage to center the axle.

The suspension in 9398 is a torque arm suspension.

[sacm93]

From personal experience, when building a double triangulated four-link setup, it's a whole lot easier to build using upper and lower links of:

-The same length,

-The same angles outward from the longitudinal axis of the vehicle, and

-The same length as the drive shaft and/or steering shaft running from the chassis to the axle.

Having said this, however, one can achieve a more authentic visual and behavioral effect by using shorter upper links than lower (a good ratio is upper=60% of lower length). One would think that doing this would make it impossible to include drive/ steering shafts (because the very characteristic that this design is aimed at achieving requires the use of a plunging drive/steering shaft; one that uses a sleeve to change length through the cycle of the suspension) however I have found that there is a "sweet spot" where you can position the shaft(s) such that they travel along an independent arc where the axle cycles through the suspension so that the distance between the drive/steering output at the chassis and the input at the axle remains the same throughout the entire suspension cycle, or at least enough of the cycle for a reasonably sized shock absorber (9.5L) to be then built into the design.

As soon as I have permissions, I will upload my "Rock Bouncer" MOC to illustrate the above concept. I used 16L lower links and 9L uppers. :)

I hope this helps anyone looking to build their own crawler/4x4/bouncer type buggy as I know they're a popular concept.

[__________________________]

From personal experience, when building a double triangulated four-link setup, it's a whole lot easier to build using upper and lower links of:

-The same length,

-The same angles outward from the longitudinal axis of the vehicle, and

-The same length as the drive shaft and/or steering shaft running from the chassis to the axle.

Having said this, however, one can achieve a more authentic visual and behavioral effect by using shorter upper links than lower (a good ratio is upper=60% of lower length). One would think that doing this would make it impossible to include drive/ steering shafts (because the very characteristic that this design is aimed at achieving requires the use of a plunging drive/steering shaft; one that uses a sleeve to change length through the cycle of the suspension) however I have found that there is a "sweet spot" where you can position the shaft(s) such that they travel along an independent arc where the axle cycles through the suspension so that the distance between the drive/steering output at the chassis and the input at the axle remains the same throughout the entire suspension cycle, or at least enough of the cycle for a reasonably sized shock absorber (9.5L) to be then built into the design.

As soon as I have permissions, I will upload my "Rock Bouncer" MOC to illustrate the above concept. I used 16L lower links and 9L uppers. :)

I hope this helps anyone looking to build their own crawler/4x4/bouncer type buggy as I know they're a popular concept.

You should make a separate post about this. I have seen a lot of people like me totally mystified about this concept.

[Victor Imaginator]

One more 4-link setup example. Best, that i can achieve at this moment.

[__________________________]

One more 4-link setup example. Best, that i can achieve at this moment.