[HELP] Need a suspension for these two axles.

[Mechbuilds]

Hey guys! 

I'm currently trying to build either a T ford or something old vintage car/truck like that. 
So far i've been stuck with trying to build a working suspension for these axles. I've tried leaf springs and all sorts of things but they always have issues. 
Either the axle tilts diagonally when suspension is compressed, axle gives itself caster, springs bend and stick because of wrong geometry.. All sorts of issues. 


https://www.mediafire.com/file/0cbm836eart98fw/T+rear+axle.lxf/file 
https://www.mediafire.com/file/zxy7sg6oiaubepr/T+front+axle+updated.lxf/file

Note: The axles can be modified for better link placement. 


I've been stuck with these axles for a while now. Asked for help from many experienced users with no avail. 
If anybody knows how to attach these two axles into a frame/chassis so the suspension works, please give it a shot! 
What i was looking for is a working suspension with good flex for offroad. 

[johnnym]

Can't you make something out of the chassis of the original? From watching the video (from here):

...I'd say you could achieve that by "connecting" front and rear axle with two extra-long axles or a concatenation of long axles.

[Mechbuilds]

Already tried that. Couldn't get it to work. 

[johnnym]

Maybe the links have too much play. What about "fixing" them on the axles (e.g. with axle through pin hole) and only use towball connections on the other ends (e.g. with the new flip-flop-beams)? For the springs I could think of something like that:

...but maybe this is to wobbly.

[Mechbuilds]

2 hours ago, johnnym said:

Maybe the links have too much play. What about "fixing" them on the axles (e.g. with axle through pin hole) and only use towball connections on the other ends (e.g. with the new flip-flop-beams)? For the springs I could think of something like that:

...but maybe this is to wobbly.

This is a pretty cool idea.. Sadly when i built it, it still was too wobbly and too soft for the suspension. 

Was thinking about a pushrod suspension style so i can pretty much hide the springs in the chassis so the axle is visible without coil springs.. 
I'm still having issues with the suspension geometry so the axle keeps tilting weirdly when it compresses. 

Would love to see somebodys solution to this issue. 

I've tried: 3 link suspension, 4 link suspension, leaf springs, normal springs, longer springs.. 
Also a big issue is that i want a fake engine on top of the axle. So space is very limited. 
Also an issue with the steering is that if the suspension flexes, the steering tends to steer when the axle is tilted sideways. 
Steering rack will give more percise steering but it has issues with suspension flex because the axle tends to stay in place while the suspension flexes so the steering rack naturally moves. 

Having a ball joint and servo setup instead of steering rack would eliminate this issue but it's next to impossible to have it behind the axle so it must be connected to the front of the axle. 
Which is different than the T ford has it.. Also servo placement would be a nightmare with the fake engine being in the way. 

[gyenesvi]

I think first you need to sort out the geometry of the axle/links without springs or any dampening. A proper design should not move sideways or let the axle tilt forward/backward. You can achieve that in various ways, but in general you need to restrict all unwanted directions of movement. For example, in your image with the 4 link setup, the four links are parallel, and hence it does not provide any restriction for sideways movement. In order to achieve that, either the links must be triangulated, or alternatively the chassis end of the links could be rotating on a pin, not a ball-joint, only allowing minimal movement sideways (for that it must be built from a regular liftarm and a towball socket liftarm or A-arm, which also has the advantage that you can simply attach a spring to the link itself). Another alternative is to use a panhard rod to prevent sideways movement. One more trick that is often used on rear axles in smaller scale lego builds is to have the driveshaft provide one more fixed point, by removing the U-joint at the axle end, and that way limiting its movement (this is similar to what a ball-joint does, and was actually used in cars of this era, it was called torque-tube suspension if I recall the name properly).

For the steering, if it’s linkage based, it comes down to proper geometry again. To minimize bump steer, the longer the steering link, the better, and it should be positioned such that the link should be horizontal when the suspension is halfway compressed. That way, the divergence from horizontal will be as small as possible in all positions, and will result in small ‘lengh reduction’, and hence unwanted steering. In case of rack based steering, if you are using two CV joints to route the steering to the axle, as then it should be okayish, true that as  the axle tilts, in theory it would effect the steering, but the wobbliness of the joints should actually accomodate the amount of rotation, so it should be negligable.

For dampening of this type of car’s suspension, I’d try either flex axles (pre-loaded in a curved shape), or torsion bars (maybe with a push-rod like extension). These could give it some sort of authenticity.

You maybe want to check out my Toyota FJ40 alternate of the Ford Raptor, it has a linkage based steering behind the axle with unnoticeable bump steer, and also a fake engine above it (but it uses springs). It has links both behind and in front of the axle and the front ones are fixed to the chassis, that prevents sideways movement. I have other builds on my rebrickable for example with triangulated rear suspension. 

[Leonardo da Bricki]

I would suggest that you mimic this sort of linkage used by the legendary Madoca. I will allow for the same sort of articulation, but with good stability.

https://rebrickable.com/mocs/MOC-8863/Madoca1977/jeep-wrangler/#details

[Jurss]

Maybe leafsprings can be replicated with some rigid hoses?

[Mechbuilds]

12 hours ago, Leonardo da Bricki said:

I would suggest that you mimic this sort of linkage used by the legendary Madoca. I will allow for the same sort of articulation, but with good stability.

https://rebrickable.com/mocs/MOC-8863/Madoca1977/jeep-wrangler/#details

I do need up and down movement as well.. The madocas wrangler only has flex but no up and down. 

6 hours ago, Jurss said:

Maybe leafsprings can be replicated with some rigid hoses?

i've gaven up on leaf springs. Either torsion axle or normal springs and preferably normal springs. 

[Mechbuilds]

Got really close with this one but sadly it also has problems.. 



It tends to stick like that and keep the bodywork and chassis tilted.. 


This is why i'm going with springs or pushrod. 

Independent suspension is childs play to make. But solid axle suspension is damn near impossible.. 

Also the axle is giving itself caster upon compression which is also bad. 

I've looked for inspiration on this. The pushrod suspension is much better because you can hide the springs inside the bodywork.. 
Sadly i can't just copy this suspension for this and even this suspension has issues since the long beams are connected via axle/stud so parts tend to bend when the suspension flexes. 

[1gor]

On 4/13/2022 at 6:17 AM, Jurss said:

Maybe leafsprings can be replicated with some rigid hoses?

Actually plates can act as leaf springs. https://brickshelf.com/cgi-bin/gallery.cgi?i=3682224

[Nazgarot]

Long axles mounted right also make for good leaf springs.

Using a 12 L axle with two 6 L axles connected to it could work. I've used something similar for a heavy load truck with a leaf spring setup, and that worked nicely.

The lime parts are 2 L  liftarms with cross and hole, cross down to the 12 L axle. This should allow for quite a bit of flex as well as some actual suspension, but the flex will be pendular... That is however very close to the actual thing.

PS: You should swapp the 6 L axles for 5 L to allow for more pendular motion. For more flex the 12 L axle could be replaced with two 6 L axles without connection between, but this needs more of the red parts to keep it in place.

Edited April 15, 2022 by Nazgarot

[2GodBDGlory]

So I take it that this solution works except for the high friction in those axles sliding. I think something similar with sliding beams instead of axles could work, but it would get bulky.

... Pneumatic cylinders could maybe be used to stabilize it, simply for their relatively low friction extension? Even ignoring the ports on it, maybe some brace could be made? What else allows low friction extension? That's all I can think of.

Maybe putting more beams on that O-frame to keep the axle straighter would help?

[Mechbuilds]

Interesting solution indeed. I might use that leaf spring on the rear axle instead. 

For the front axle though, it's acceptable to use springs.