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Technic Builder

Suspension / steering geometry of large multi wheel cranes?

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Hey everybody, I'm back from the dead (not like anybody really knows me).

I made this thread months ago:

http://www.eurobricks.com/forum/index.php?showtopic=88838

Then I had to put my legos in storage for a few months while my wife and I sorted out a move (and I sorted out a new job)

Legos are back out now and I'm working on my crane again.

I'm completely overhauling the steering setup I had before - it was just a bad design. I realized just how much space is necessary in the main body of a crane and the suspension arms were taking up way too much room. The new wheel hub I'm working on (ditching portal axles) should free up 2-3 studs on either side of the center line giving me far more room to put features in. I was about to give up on the idea of multiple speeds, but that would just be lame heh.

My question to the lego community is if anybody has any resources on the steering / suspension geometry of real multi-wheel cranes (let's say 10 wheels and up). I know that I CAN include features such as kingpin axis inclination, appropriate castor, akerman geometry etc, but I'm not really sure how necessary those features are on a lifesize crane, much less a lego version.

So even though I've looked at tons of .pdfs from Liebherr and Manitowoc mobile cranes, I have not yet found a resource that really breaks down the exact wheel alignments. Does anybody happen to know how these companies set up the wheels on their cranes? I know most of them use pendicular axles, but I don't want to do this on my lego version (for a number of reasons).

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Do these cranes even have suspension? There must be some information on google somewhere, or try wikipedia for a desciption on crane suspension. Good luck with it.

H

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Do these cranes even have suspension? There must be some information on google somewhere, or try wikipedia for a desciption on crane suspension. Good luck with it.

They have unsprung suspension, in general. That is, they have a system to keep all the wheels on uneven ground and distribute load more or less evenly.

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Do these cranes even have suspension? There must be some information on google somewhere, or try wikipedia for a desciption on crane suspension. Good luck with it.

Yes, road permitted cranes always have suspension, and as noted, they have adjustable suspension, per axle, to distribute the weight, limited to 12t per axle on the road. Also, they can lower itself down to pass through low hangar doors, for example.

IMG_7132.jpg

OP,

On every pdf there is steering modes section, where it is showed how the steering works in different modes.

Example:

552_vid_m.jpg

If that is what you are asking?

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I think he wanted to know the specific attach points of the steering arms which would allow you to calculate caster, camber, and toe.

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The steering in most large mobiles is computer controlled, in road mode they will all pivot around a central point so if you drew a line perpendicular to each wheel all the lines would cross at the same point. In other modes they can all be steered independantly to manouvre around obstacles. I dont worry about the geometry too much in my cranes when I am adding other steering modes, I have crab steer and road mode in mine.

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I should have made my question clearer.

Does anybody know what settings most mobile cranes use for kingpin axis inclination, castor angles, and camber? Some of these possible alignments seem less necessary in such a large vehicle that is designed for slower speeds (sub 50 MPH).

The only one that seems particularly useful in a Lego model is a little kingpin axis inclination. It will reduce the scrub radius and help the wheels return to center. A reasonable castor angle MIGHT help wheels clear objects but in a vehicle with 18 to 20 wheels if one wheel is going over an object there's 17 or 19 other wheels still tracking straight and thus making the vehicle drive straight.

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