# Adjustable ride height with actuators



## arklan (Dec 10, 2012)

Might be the wrong place for this but...
What do u guys think of pushrod suspension with a linear actuator as the push rod to adjust ride height.
Except swap the shockie and "push rod" around so the shockie takes the shock first, some will be transferred to the chassis so theres a bit less shock on the actuator.
The hypothetical car would weigh 700-800kg and the actuators can push 400kg so they would usually be pushing half their rated weight for when a speed bump is coming up. 1 actuator per wheel.
When cornering the weight would shift but still not more than their rating. And they can hold a lot more weight without being able to push it so thats not an issue.

Thing that has me is the vibration, say i drove for 20 000km, thats a lot of vibration for the actuator to take without ever having been used, let alone if it was extended..
I think it might wear the teeth out on the worm gear.

I was trying to think of a way to do it where the actuator provides the pushing force but doesnt take the weight, but i dont think its doable without getting out of the drivers seat and using a locking pin or something..

Ps. This is a thought exercise


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## Overlander23 (Jun 15, 2009)

I haven't seen it done in a production vehicle. Most systems use air for ride height, hydraulics for cornering stabilization, or megnetorheological dampers for handling. 

I don't know of any production vehicles that use electromagnetic, linear actuation. But it can be done. I love the idea.

Skip to about 1:15 on this clip for the design: 
https://youtu.be/IQ1eKddstxM?t=76

And this system works on huge military trucks:
https://www.youtube.com/watch?v=seDAMnJZOEw


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## MalibuMan (Feb 28, 2015)

Interesting idea. Not for ride height, but for body leveling or even leaning into corners.

I am building a single-person light electric vehicle with wishbone suspension on all 4 wheels. If I can pump up the left suspensions and lower the right suspensions on a right corner, the body of the car will lean into the corner like a bicycle.

On that video they showed half of the BMW trunk filled with computers. I want to use the steering wheel to drive the amount of leaning. If I can raise the left 5 cm and lower the right 5 cm, that would be already enough to have effect.

I live near the TUe in Eindhoven, do you have a name I can contact?


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## Duncan (Dec 8, 2008)

Hi Malibu

If you want to build a "leaning machine" then you don't need an active suspension system
You need
Tonnes of wheel travel
And zero roll stiffness
You then drive it like a bike - leaning into the corners
You may want a method of introducing some roll stiffness for very low speeds/parking

I looked at doing this a few years ago - I was going to raise the suspension when moving and drop it onto some bump stops at low speed

Wheel travel - you need enough so that you don't hit the limits while cornering - that would be bad!

So with say 1.5m track you would need about 750mm wheel travel (375 up - 375 down)


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## MalibuMan (Feb 28, 2015)

Duncan, I see what you mean by 'some roll stiffness for low speed', hahaha.

As the center of gravity is lower when leaning, the cart will immediately fall over into maximum lean position with zero roll stifness.

I want the cart to be 1 m wide, with a 60 cm body which leaves 20 cm for each wheel arm. If the wheel arms are 45 deg up/down, then the track will be 60 + 2 * 20 * 1/2 * sqrt(2) =~ 88 cm and the height difference is 2 * 20 * 1/2 * sqrt(2) = 28 cm. This results in a 17.6 deg angle (0 deg is up).

If I narrow the chassis where the wheels are (still a 60 cm body where the driver is) to 40 cm I can use 30 cm wheel arms. Then my leaning angle becomes a 27 deg angle (0 deg is up).

I would like something electrical that without power does not tilt at all, so it has max roll stiffness getting in and out of the vehicle. Then to avoid nervous body roll on slight direction changes like following the road keeping your lane it has to be progressive with almost no lean around straight forward +/- 5 deg. For bigger steering actions the leaning should slowly increase. I think the progressive action is best accomplished with electrical actuators?

PS: Arklan, if you think I'm hijacking your thread please let me know. I will be glad to open a new topic, but think the actuator technology keeps it on-topic.


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## Duncan (Dec 8, 2008)

Hi Malibu

I was looking at a human powered thing at the time - a reverse trike

The idea was to have the body down at the front when stationary and on the bump stops
The control column - handlebars would be "up" - to make it easy to get in 
It would be possible to ride off in that configuration

One you get rolling you pull the handlebars back and downwards - this moves the front suspension up off the bump stops and the trike body into the horizontal position

You then click the handlebars into the comfortable operating position

If you have to slow down you move the handlebars back up - lowering the front suspension

_Then to avoid nervous body roll on slight direction changes like following the road keeping your lane it has to be progressive with almost no lean around straight forward +/- 5 deg.
_You DO NOT want this that would feel wrong - if you ride a bike it does lean a little for small direction changes and it feels "right"
The amount of lean is controlled by the steering movement 

Look up RC bike models - better yet borrow one and operate it for a bit


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