Which Steering Hub?

[badmad]

Hey

i try to build a height adjustable front suspension. But i run into a problem by using the steering arm 32495c01. The problem is when i lift or lower the axle the arms of the steering arms will expand or contract so that the wheels will not stay straight. 

I build 3 different axles but the result still be the same. 

Maybe i don't see the solution. Any idea? Maybe an other steering arm/hub? 

[Void_S]

Well, all the setting hubs have the same steering arms mount point: at the center of the wheel/axle. Your situation is called "bump steer" and is not about the hubs themselves but arms location: all three arms (lower+upper+steering) must be in a parallel and have the same length. Otherwise, the one with the shortest length and/or the farthest mount point will pull the steering hub when the suspension moves.
Do you have any photos of your suspension? I think we may help you here with a better placing of the arms.

Edited October 21, 2019 by Void_S

[badmad]

I have pictures of the second version. 

The first wasn't good. 

 

[letsbuild]

Are you building with Lego? 

To answer the question, as you rotate the suspension arms up and down, it follows a circle where the center is your rotation point.

https://upload.wikimedia.org/wikipedia/commons/7/71/5link-rear1-small.gif

A brief example. Look carefully and you can see the wheel move in and out slightly.

EDIT: 

https://en.wikipedia.org/wiki/Multi-link_suspension 

This wikipedia page has some great gifs demonstrating this effect. 

There's no way around the problem of the wheels moving in and out UNLESS you raise and lower the whole axle assembly, including the wishbone mounting points.

Edited October 21, 2019 by letsbuild

[brunojj1]

 

2 hours ago, badmad said:

 

What scale are you trying to build in? However, I have reservations concerning the mounting points of the springs, only 1 per side, if they can hold the weight of the finished car..

The steering hubs / arms are not the problem. The steering links need to go parallel to the arms if you want to avoid toe in / toe out while compressing the suspension.

You will soon find out it´s difficult to make the height adjustable. Forget about the mini LA´s – most likely they cannot hold the stress at the end, loose synchronisation after „klicking" on one side or the other. Once I came up with the following solution with 8-tooth gears operated by worm gears which was reliable and strong enough, connected/synchronised and routed to the middle of the car:

I don´t recommend anything particular of the given setup, but maybe it helps to get any fresh idea. The big disadvantage of the shown axle were the wheels wobbling due to the used hubs and custom steering arms enhancing the effect, but the priorities were others.

Another inspiration to your particular needs could be something like this:

 

 

 

Edited October 21, 2019 by brunojj1

[Erik Leppen]

1 hour ago, Void_S said:

all three arms (lower+upper+steering) must be in a parallel and have the same length. 

This is the key. Your (dark gray) steering arms are 2x6, but the linkages connected to the gear-rack are 9L. This makes the cirular movements (while moving up and down) different, and the wheels will turn inwards or outwards (i.e. not parallel, when seen from above) when the arms are not horizontal.

Fortunately, 6L steering links exist. https://www.bricklink.com/v2/catalog/catalogitem.page?P=2739a&idColor=11#T=C&C=11 

As a side node, I personally often try to make the suspension arms approximately horizontal on average. Then, most of the movement range of ball-joints and CV joints (for driven axles) can be used for steering. Also I often try to keep suspension travel (= vertical distance between highest and lowest point) relatively little. Yours is 2.5 studs, which I would find quite a lot. The longer the travel, the stronger the springs you need to hold a certain weight. Also, you need somewhat larger wheel arches. But, this is personal taste. I think many builders use larger suspension travels than I do.

By the way, I quite like the setup with the linear actuators. However, I didn't realize that they might run into "click" as per @brunojj1's remark. For my Chiron rebuild, I used a solution with worms and 24t gears. You need to beware of twisting axles though, and keep the worm as close as possible to the lever that holds the springs. (In brunojj's setup I'd personally worry about the 8t gears cracking or the dark-gray 8L axle twisting...)

 

[badmad]

1 hour ago, letsbuild said:

Are you building with Lego? 

Some parts are not lego but the most (90% of all, 100% of technic parts) are lego. Thx for your explaination.

23 minutes ago, brunojj1 said:

What scale are you trying to build in?

1:8

I calculated a complete width of 28 studs for the Battista. Thx for your pic. It looks like an awsome axle. Miles away from my rookie setup 

3 minutes ago, Erik Leppen said:

By the way, I quite like the setup

Thx 

I try to bring the car a show and drive suspension which should move visible. 
 

Maybe i think i could make a wedge chassis where just the rear will be adjustable. But I do not want to give up finding a good solution for the front 

10 minutes ago, Erik Leppen said:

This is the key. Your (dark gray) steering arms are 2x6, but the linkages connected to the gear-rack are 9L.

Oh damn. I did not think about that at all.

[brunojj1]

1 hour ago, Erik Leppen said:

(In brunojj's setup I'd personally worry about the 8t gears cracking or the dark-gray 8L axle twisting...)

The 8t gears didn´t crack so far, being extensively loaded and after long use, whether in the manual nor the RC version of my McLaren. I don´t care about slightly twisting axles as long they´re not breaking or twisting irreversibly, as long the heavy duty mechanism does it´s job, but that indeed could be the case.

 

1 hour ago, badmad said:

1:8

Then you probably might consider to use the Porsche or Chiron parts, use appropriate wheels & hubs and build the axle 29 - 33 studs wide total. That requires more engineering and more parts. On the other hand it opens a wider range of possibilities.

[nicjasno]

They're all bad unfortunately.

[Gray Gear]

I myself think of this when developing an axle: Would i feel comfortable putting a 1.5L Waterbottle on top of this?

If the anser is no, then your axle is too weak.

If  the answer is yes, then actually putting a 1.5L Waterbottle on top of the axle is also a good strength test, to see if there is any flex that you dont want.

[nicjasno]

Weight is always a good measure. If your suspension can handle 1.5kg per axle, it can certanly handle less and will feel very strong.