[moc] Citycrane in Demag AC40 City Style

[efferman]

My CityCrane in miniscale is a little cute thing, but for some technical ideas it is to small.

An example: The front and rear Axles steers counterwise and steering in the same direction. To try this, i have started a moc who is inspirated by the Demag AC40 City (PDF).

Th first attempt results in the following short video

Counterwise Steering is no problem, but the dogwalk is a little bit critical. With its one Gear more on the front axle, it comes not exact back to center, when the rear axles are in center. When i switching to normal Steering i must adjust the front axle to have a correct steering angle. Currently i have no idea how i could solve this problem.

any critics, ideas or questions?

p.s. this will become not an rc model. I think with its 15 studs width, it is to small to add a drivetrain to the steering system.

[Zerobricks]

This may sound funny, but what about using a kind of a clutch that can engage at a right angle to disenagage and engage at same positions, so there is no desync? Clutch could be as simple as a pulley wheel with few pins and a half 2L beam (++).

[efferman]

That sounds absolutely not funny. At first i had the same idea. The problem with the clutch gears is that they have more play between sync.ring and the clutch gear . in my humbly opinion thats not usable at a steering system.

Edited August 15, 2010 by efferman

[Zerobricks]

Not clutch gears.... Self made clutch using beams and pulley wheels with no air.

[efferman]

sorry, it seems my brain is currently not in condition to understand this without a picture. is it this what you mean?

Edited August 15, 2010 by efferman

[Zerobricks]

I meant a clutch like this:

There should be a second pulley wheel, and you can add 2L beams for less air.

[efferman]

thanks for your suggestion, but i think it is a little bit to big for the space which i have. And its no solving for my main problem

Counterwise Steering is no problem, but the dogwalk is a little bit critical. With its one Gear more on the front axle, it comes not exact back to center, when the rear axles are in center.

edit:

I think i have a solution for my problem. for every direction the same number of gears. only the trackwidth is one stud wider and the Ackerman Geometry is lost in the modification.

I hope the idea works better, with the complete chassis, than the old version

Edited August 16, 2010 by efferman

[dhc6twinotter]

Efferman, I really like how you designed the steering on this! One of my long term projects is an AC700, and I've been trying to figure out how to do a crab/steer setup as well. I've got some sketches for the steering mechanisms, but I'm not sure it would work as well as yours. I'll have to do some experimenting, and may end up borrowing your idea. Nicely done!

[efferman]

thanks

feel free to use it, if it works

[efferman]

the redesign of the steering system is complete. Double bevel gears make the switching, between the dogwalk and normal steering, easier. A lever holds the switch axle on its position. here some pics (thumbnails)

more pics at the Brickshelf folder when it is online.

If one of you wants to rebuild it, make sure that all axles are in the same direction, to make the switching possible.

Here is a little movie

comments, critics or suggestions are welcome.

Edited August 22, 2010 by efferman

[Milan]

Is there a difference between "Normal steering" and "Small turning cycles" as you described.

I mean, it has two steering modes, not three, right?

[efferman]

In this point the description is a little bit inaccurate. There are two modes:

Normal steering with the small turning circle and the dogwalk, which let shows all wheels in the same direction.

[Zerobricks]

Good job! Crab steering might be a better word?

[efferman]

maybe, english is not natural for me and "dogwalk" is imho the direct translation of "Hundegang". That is the only (so far as i know) description in germany, what are used by the owners of mobile cranes in my bussines enviroment.

Edited August 22, 2010 by efferman

[roamingstop]

LEO does not have a direct translation - so searching (in meine schlechtes deutsche) I found the following PDF - which indicates a picture of 'Hundegung' in the bottom.

My link. Same as Crab Steering.

Basically 4 wheel steering in the same direction - so allowing diagonal movements, with a wide turning circle (e.g. when dragging other objects).

Edited August 22, 2010 by roamingstudio

[shimon]

Great idea, i like it

Would it have other interesting functions?

Question: how are you going to operate the boom if the steering is being controlled from the turntable, or is it just temporary?

Looking forward seeing it finished!

[Milan]

Regarding steering:

On Mobile cranes there are often multiple steering modes, in Liebherr cranes for example there are up to 5 different steering modes.

Three modes are most common:

1 Front wheel steer (for road use).

2 All wheel steer (for best manoeuvrability).

3 Crab steer (for sideways motion).

[efferman]

Would it have other interesting functions?

good question, maybe it will become only a simple city crane. maybe it becomes some strange functions. i dont know at this time. Currently i think about how i could make the outriggers to fit them in scale and let it work properly.

Question: how are you going to operate the boom if the steering is being controlled from the turntable, or is it just temporary?

The final place for the steering wheel is (hopefully) in the drivers Cab and rather sure at a flashing light at the superstructure. the boom will be probably lifted by four pneumatic cylinders, or four linear actuators.

[Sam42]

Great moc, can't wait to see some of your solutions for things like the outriggers and boom.....

btw i've heard the term dog-walk used in english to describe this type of steering,

Edited August 23, 2010 by Sam42

[efferman]

Great moc, can't wait to see some of your solutions for things like the outriggers and boom.....

btw i've heard the term dog-walk used in english to describe this type of steering,

thanks for the info

btw, i have some pics from my outrigger concept. Sorry for so many colors, first it must work

more pis in the folder when it is online again.

actually the complete stabilizers have the dimensions 7x6x15 studs. With extended outriggers the length is 31 studs. The "stabilize cylinders" expands nearly 4 studs and they are locked by the axle connector with the 2L axle in it.

comments, questions and suggestions are welcome

ciao

[Milan]

I am always looking for a new outriggers concept.

It would be perfect if one could invent fully RC outriggers, which are compact for 1:20 scale.

This is RC and, IMO, the best so far:

http://www.brickshelf.com/gallery/Zoli/6x6Ginaf/gcv024.jpg

[efferman]

It would be perfect if one could invent fully RC outriggers, which are compact for 1:20 scale.

RC complete Mechanical or with pneumatics?

[Milan]

RC complete Mechanical or with pneumatics?

BOTH.

Look at the picture I have provided.

This concept has mechanical extension of the outriggers (via gear racks and 20tooth gears), and autovalve for pneumatics UP-DOWN. So it is RC.

[efferman]

BOTH.

Look at the picture I have provided.

This concept has mechanical extension of the outriggers (via gear racks and 20tooth gears), and autovalve for pneumatics UP-DOWN. So it is RC.

i think this is easy. give me time till tomorrow

[Milan]

i think this is easy. give me time till tomorrow

It is easy, but make it 5 or 6 stud wide, including bracing so it wont brake when pneumatics start lifting the crane. That may not be so easy.

I am going to work on it tonight, too.

OK, We will meet tomorrow with the results.

If we come to the good solution, then maybe we can both use it on our WIP cranes.