Help With Crane Steering

[Saberwing40k]

I am attempting to build a nine axle mobile crane, and I want it to be able to achieve all modes of the real thing, including crab steer. I know that Liftingbricks has done this with his crane, but I can't figure it out.

The constraints I'm working under are as follows:

I have only two motor channels to work with.

I want the axles, except for one, to steer proportionally in normal steer mode. One axle will be locked.

I only have short, new gearracks in the required quanity.

The crane has suspension, with live axles.

Any help and suggestions are welcome.

[Hrafn]

I am attempting to build a nine axle mobile crane, and I want it to be able to achieve all modes of the real thing, including crab steer. I know that Liftingbricks has done this with his crane, but I can't figure it out.

The constraints I'm working under are as follows:

I have only two motor channels to work with.

I want the axles, except for one, to steer proportionally in normal steer mode. One axle will be locked.

I only have short, new gearracks in the required quanity.

The crane has suspension, with live axles.

Any help and suggestions are welcome.

So you have one channel for driving, and one for steering?

Are you trying to get Ackerman steering in the normal mode? That will make it more difficult to also do crab steering.

[Alasdair Ryan]

My rotary telehandler will have three mode steering in it via a gearbox, after the gearbox each out put to the axle will go through a worm gear to help stop any play.

[Zerobricks]

Ackermann is out of question here... Also when steering normally each axle has a different angle, but in crab mode all angles are the same.... You got a pickle here...I cant think of a simple solution besides just making a 4x4 rough terrain crane :)

[BiohazardRacer]

First of all, in wich class is your crane supposed to be ?? 500 tons 900tons or 1200tons (on scale of course). I think that a 9 axled crane doesn't have crab steering because of the weight of the crane and the fact that not al axles steer on such a big crane. Maybe this could help you further http://lowlug.nl/forums/93/11053.html?hilit=mammoet. this guy build a gigantic liebherr LTM 11200 mobile crane. You probably need to translate the site because it's dutch. I hope this would help you . I'm very inquisitive about your crane

[Milan]

First of all, in wich class is your crane supposed to be ?? 500 tons 900tons or 1200tons (on scale of course). I think that a 9 axled crane doesn't have crab steering because of the weight of the crane and the fact that not al axles steer on such a big crane. Maybe this could help you further http://lowlug.nl/for...l?hilit=mammoet. this guy build a gigantic liebherr LTM 11200 mobile crane. You probably need to translate the site because it's dutch. I hope this would help you . I'm very inquisitive about your crane

9 axle cranes have crab steering. They need it more than smaller crane.

There are very few 9 axle cranes existing, most notable LTM 11200 and Demag AC700, both having crab steering.

[allanp]

Sounds awesome. What wheels are you using? Do you know what will be the distance between wheels/axles? Which axles will be driven?

Edited November 23, 2013 by allanp

[BiohazardRacer]

9 axle cranes have crab steering. They need it more than smaller crane.

There are very few 9 axle cranes existing, most notable LTM 11200 and Demag AC700, both having crab steering.

I dont think so mate, if you look at the LTM11200 than axle 6 and 7 are solid non steerable axles so it can't have crab steering. otherwise i would like to know where you got the information that it can crabsteer, Liebherr's own website doesn't confirm your pronunciation. Crab steering is more common on the lighter 2, 3 and 4 axled cranes.

[Milan]

I dont think so mate, if you look at the LTM11200 than axle 6 and 7 are solid non steerable axles so it can't have crab steering. otherwise i would like to know where you got the information that it can crabsteer, Liebherr's own website doesn't confirm your pronunciation. Crab steering is more common on the lighter 2, 3 and 4 axled cranes.

They are non-steerable for normal steering modes, and when vehicle speed is under 30 km/h.

Otherwise, every LTM has crab steer, even the mighty 11200.

From Liebherr LTM11200 brochure:.

[BiohazardRacer]

All right didn't know that

[KirTech LAB]

As far as i know, some cranes in the crab steering have not equal steering angles (so, some wheels have to slide) - the questin is "will it crash model steering mechanism, or not?"

[Milan]

All right didn't know that

Glad to clear this up, friend!

As far as i know, some cranes in the crab steering have not equal steering angles (so, some wheels have to slide) - the questin is "will it crash model steering mechanism, or not?"

That is correct, some axles on cranes in crab steering mode do slide a bit (due to inability to achieve full steering angle), usually only the central one(s). But that is not big problem since crab steering is used just for parallel parking.

On the LEGO model, I would make that all axles steer equally when performing crab. On my earlier crane with crab mod engaged, there were problems with parallel parking.

[Bricktrain]

The big difference is real cranes use electrically controlled hydraulics for steering not full mechanical systems. For my six axle crane I am using individual steering motors for each axle group but wont have any ackerman angle possible.