Mobile Dockside Crane

[doug72]

My next MOC is a freelance version based on a Liebherr 120 Crane but will only have four caster steering units instead of six.

Following the build of my mobile ship loading conveyor, a number of problems arose and were solved & almost all due mainly with the various steering modes.


For my new MOC initial thoughts were to have a mechanical solution to control the steering using only one M motor and a selector gear box (see image)
Black = M motor input.
Red = output to caster units 1 & 2 with direct drive from M motor.
Yellow = output to caster units 3 & 4 via selector gear which can either turn units in same direction as 1 & 2 or in opposite direction, plus stop the units turning.

Result: selector unit too large and complicated and suffers from the excessive backlash due to the red gear clutches, about 90 deg. lag when reversing drive to units 3 & 4 resulting in caster units out of step.

REJECTED.

For the the previous build I used the small c/o switches on the PF controllers to set the steering modes but found this to be confusing to get right.


Reverting to a two motor solution for steering as per Mobile ship loading conveyor, except I will use PF switches this time to select the required mode for each M motor. 


This will allow for 3 steering modes:

1/.    Normal steering using only 2 caster units with other set in straight position.
2/.    All caster units turn together same way for straight, crab & sideways movements.
3/.     Pairs of caster units turn in opposite directions to give radius steering.

A 4th function is possible if used an M motor for each uint plus four PF switches.
I but don’t plan to install this due space constraints.

The build so far:
"

MOC will have these functions:-

1/. Drive travel - XL or L motor.
2/. Steering - two M motors.
3/. Drive outriggers - ( may be HOG ), depends on space in the under carriage. M motor with PF switch.
4/. Slewing of crane - M motor
5/. Luffing of jib - L motor.
6/. Hoisting - M motor.

PF receiver and battery in the undercarriage & the two PF Rx & battery in the rotating structure.

Edited February 10, 2018 by Doug72

[suffocation]

Looks good!

How will you keep the caster units from going out of sync?

[doug72]

50 minutes ago, suffocation said:

Looks good!

How will you keep the caster units from going out of sync?

Both steering motors now installed along with two PF switches. Tested and functions OK for all three steering modes.

To keep in sync. you need to return all caster units to the fore & aft position, before changing to next desired steering mode.

Mode 1: Could get away with one PF switch but with two it allows for either end of the under carriage to steer.
Mode 2: Performs well at all positions of caster unit and can change direction on the move from fore & aft to crab to sideways..
Mode 3; Performs OK as long as do not try too tight a turn, should be better once drive is connected and iall wheels are powered.

Next step is to installed the wheel drive to each caster unit, may need some adjustment of the differentials to ensure alll wheels run the same way.

Under carriage is 23L wide x 37L long.

Edited January 3, 2018 by Doug72

[KikoTube]

Nice Project!

But don‘t you think you should use smaller wheels?

[doug72]

3 hours ago, KikoTube said:

Nice Project!

But don‘t you think you should use smaller wheels?

Thanks, I have been thinking about fitting smaller wheels, current size is 49.5 x 20, but can fit 43.2 x 22ZR tires on the same hubs.
I will also see if it is possible to have 4 wheel caster unit bogies.

Update:

Drive now installed and initially used a worm drive giving an overall reduction of 12:1 using  20:1 worm gear and & 20:12 step up gears which proved too slow.
Now changed to direct drive via 12/20 reductiongears.

Under carriage unit tested for drive and steering functions.

Steering: a new problem has appeared not identified in previous tests !!

Currently using two M motors to turn each pair of caster units.

The problem is the speed of each motor is sightly different causing units 1 & 2 to get out of sync. with units 3 & 4 especially if a lot of turns are performed !!!

So I may revert to a single motor for steering but dispense with trying to get mode 3 radial steering.
I.e. just have mode 2 for straight, crab & sideways motion with maybe a way to lock the caster units at each end for mode 1 steering.

Probably means reconfiguring the drive and steering shaft / gear paths..

Unless anyone has a fix for this problem.

PS I think this may have also been an unidentified problem with the Mobile Ship Loader Conveyor.

Top side view.

Underside view.

Edited January 4, 2018 by Doug72

[BrickbyBrickTechnic]

Looks nice so far! Though it would be a good idea to secure the gears in the drivetrain better. Seems like there's some potential for slipping.

[doug72]

1 hour ago, BrickbyBrickTechnic said:

Looks nice so far! Though it would be a good idea to secure the gears in the drivetrain better. Seems like there's some potential for slipping.

There is no slippage in the drive to steering for each unit, the slippage is between the two units due to un-eqaual motor revolutions.

Now tested a one motor set up with all units hard coupled together, just need to sort out best location for the Steering motor.

Its hard to see in the images due to balck beams & gears. ( using up my over stocked of black parts ).

The drive for wheels runs down each side of the undercarriage and is cross link on the centre line from the L motor.

Steering drive is across the ends of the under carriage and cross linked on the centre line, had to dog leg the cross link axles so one passes below the other. 

Smaller tires now fitted and looks much better. Will try and re-design the caster units to a 4 wheel bogie verision.

Edited January 4, 2018 by Doug72

[doug72]

This is the drive path for steering (Green line) and drive to wheels (Red line)
L = drive motor / M = steering motor.

As it stands will only be able to steer the undercariage in straight - crab - sideways directions.

Looking for a way to disconnect aand lock a pair of caster units at either end so other pair of casters can turn independently for steering
The change over clutches have too much backlash, possible sliding gears mind work.

Anyone got ideas how this can be achieved ?

 

Edited January 4, 2018 by Doug72

[Wolf_Zipp]

Hello Doug72

Interesting Project.

For the steering Problem : Change one Z12 wheel to the other side (both inside) and you can drive an curve.

Because the wheels : they are very wide, would it better done by my solution ??

OK, I´v no diff inside. It´s  only 7 L wide with 62,4 wheels.

EDIT: For curve drive you need a diff in the red path.

 

Edited January 4, 2018 by Wolf_Zipp

[doug72]

11 hours ago, Wolf_Zipp said:

Hello Doug72

Interesting Project.

For the steering Problem : Change one Z12 wheel to the other side (both inside) and you can drive an curve.

If do that then OK to steer in a curve but not in straight, crab or sidways.

 

11 hours ago, Wolf_Zipp said:

Hello Doug72

Because the wheels : they are very wide, would it better done by my solution ??

OK, I´v no diff inside. It´s  only 7 L wide with 62,4 wheels.

Diff required as when caster unit turns on the spot wheels rotate in opposite directions.

 

11 hours ago, Wolf_Zipp said:

 

EDIT: For curve drive you need a diff in the red path.

For my mobile ship loader coveyor MOC I did have diffs in the drive system and there is space to fit them where the the drive splits fore & aft each side.

When I used two M motors for steering both were control from one PF channel and due to slight differences in RPM for each M motor that caused the out of sync problem
May revert to that, but use separate cPF channels to control them. First I an going to test a clutch unit that will dis-engage one pair of caster units and lock to prevent turning and allow steering from one end only.

Edited January 5, 2018 by Doug72

[suffocation]

Jeroen Ottens devised a locking method using Bionicle teeth to ensure that steering modes could be switched only when the gear racks were aligned - not sure it can work for you (not even sure how it works!) but here it is, ten posts down:

 

 

[doug72]

2 hours ago, suffocation said:

Jeroen Ottens devised a locking method using Bionicle teeth to ensure that steering modes could be switched only when the gear racks were aligned - not sure it can work for you (not even sure how it works!) but here it is, ten posts down:

Thanks - had a look but like you found it hard to figure how it works, think it would be too large to use anyway.

I have devised a c/o unit to dis-engage and lock the output but its to large in fit into the drive train !!

See image, it might be usefull for to someone. One drawback is the slackness in driving ring clutches - almost1/4 turn slack in the output.

I have re-tested a two motor solution but with each motor on seperate PF channels. Seems to work better.

For Modes 1  only one channel operated.

For Mode 2 steering both channels used with small c/o switches on basic controller in the same position and all caster units turn in same direction.

For Mode 3 steering one switch has to be change to other position and when both levers moved together each pair of caster unit rotate in opposite directions to each other.

To re-align pairs of caster if get out of step then each caster pair is turned individually.

Next step is to re-build the under carriage to allow two differentials to be installed in the drive train to wheels.

 

Edited January 5, 2018 by Doug72
Image file name removed

[doug72]

Drive for steering and wheels revised:
It took quite a while to get all eight wheels rotating in the same direction !!!

Underside view
Differentials are now used for drive to caster wheels.
All motors for steering and drive grouped together, but this leaves little space for a large battery box . May shift steering motors or battery top side.


Two Steering motors now installed top side as per an earlier image.

 Large battery box now installed inside under carriage.
Out riggers will probably be operated by HOG or PF switches.

Note: Caster wheels are correctly aligned, image distorted by camera.

Top side view
Turntable gear ring installed.which is supported at 8 locations.
 Had to raise this by 1L to clear differential Z28 gear to prevent slewing gear fouling it.

Rotating base for crane structure:
Four sets of double wedge wheels are used for support, 12T slewing gear in position which will be driven by an M motor.

I have since found that Liebheer make a rail mounted version of this crane which is mounted on a portal structure, much eaiser to build as no steering would be required.

Edited January 6, 2018 by Doug72
deleted image file text / inserted correct image / update.

[Wolf_Zipp]

Hello, I´ve tested the clutch 2 reply before. I think it´s a fail inside:

It works better together with a differential :

IMG_20180106_173907 by Wolf Zipp, auf Flickr

Clutch left: left axle blocked

IMG_20180106_173943 by Wolf Zipp, auf Flickr

Clutch right: Diff blocked, both axles same turn

Clutch Center: Diff free, force on both axles, but maybe not same turns.

Force incoming to the diff or the right axle.

 

@Doug72

When you will drive a curve, you need a diff in the drive System, because every Corner get a other distance to drive.

[doug72]

Thanks for your input.

Unfortunately its too large to fit in space available.

I tried three differentials  before in drive train on my Mobile Ship Loader Conveyor but it failed.

See topic on page 2
 

 


If any wheel loses contact with the ground it starts spinning at full speed and ALL other wheels stop turning.
The under carriage is quite rigid, no easy way to give them independent suspension.

IMG_5112 by Doug Ridgway, on Flickr

Probably ony workable solution would be MIndstorms EV3 with each caster unit powered and steered individually. 

As it is now I am happy with steering for modes 1 & 2 and mode 3 if limit the degree of turn.

[doug72]

2 hours ago, Wolf_Zipp said:

When you will drive a curve, you need a diff in the drive System, because every Corner get a other distance to drive.

As you rightly pointed out when radial turning, the wheels on the larger outer radius have further to travel and hence have to run faster.

I think I have been ambitious in trying to have all powered / steered caster units.
With my current set up this does not seem achievable.

Going to try powering only one pair of casters at one end of under carriage with a single differential between sides, this along withe the differentials in the caster units should ensure all wheels rotate at correct speeds.

Just done a quick trial by disconnecting the drive to one pair caster units with a tempoaray lock on the redundent drive axles.

A big improvement and should be even better once I add  a central diff.

Drive will be "U" shape with the L motor driving the diif. - then splitting to left & right powered caster units.
The other pair at other end of under carriage will run freely with thier own diffs. to allow for turns.
All caster will still to be steered by two motors. 

One other possibity is two independent drive systems for each pair of casters but controlled by one PF channel.

Will be re-configuring and testing tomorrow.

Edited January 6, 2018 by Doug72

[doug72]

Steering issues fixed at last !

Seems I made an error previously with drive train differentials in the wrong place, with them placed between fore and aft caster units on each side of under carriage.

This caused a problem when Mode 3 steering required.
i.e Radial steering as wheels on the outer radius could not run faster than those on the inner radius causing gears etc. to grind and skip.

Now revised as per schematic layout shown:

L motor drives central differential with outputs to the left hand and right hand sides of the under carriage.

Right angle gear box drives the wheels to each caster unit.
Each caster unit still has a differential.

Tested and functions well in all steering modes, and can perform tight turns without gears grinding or skipping now.

Managed to re-configure without a major strip down and the steering system remains unchanged.

Battery box now installed centrally under the turntable gear ring.

Next step: install four riggers.
 

Edited January 7, 2018 by Doug72

[Aventador2004]

Interesting, why so many topics?

[doug72]

7 hours ago, Aventador2004 said:

Interesting, why so many topics?

To show WIP, the problems encountered and seek comments / suggestions and solutions found.

[Wolf_Zipp]

17 hours ago, Aventador2004 said:

Interesting, why so many topics?

Oh, sorry, is it not allowed to get a technical discussion ??

I see only 1 Topic with some answers. That other is not the same building -> other Topic.

When it´s not ok, I hold me back with commends in future

Edit : I see also 3 Topics to 1 MOC  in a few days

Edited January 8, 2018 by Wolf_Zipp

[Aventador2004]

6 hours ago, Wolf_Zipp said:

Edit : I see also 3 Topics to 1 MOC  in a few days

Sorry, that sounds bad, but it seems like a long topic can allow answers too...

[1gor]

This is normal for such complex mocs and drive for perfection  or at least for acceptable compromise is in human nature 

@Aventador2004 you don't see such cool crane project every day so enjoy and follow development.

@Doug72 as you can read between lines I found it is a great challenge and the same way great project.

@Wolf_Zipp you are right with differenrials. Years ago I was watchig development of 4wd vehicles and they mentioned for turning and drive on solid surfaces exactly the same suolution with differentials. (I use it whenever creating AWD moc with unequall tires)

[Aventador2004]

I know, but it seems 3 is a bit much.

[doug72]

13 hours ago, I_Igor said:

This is normal for such complex mocs and drive for perfection  or at least for acceptable compromise is in human nature 

@Aventador2004 you don't see such cool crane project every day so enjoy and follow development.

@Doug72 as you can read between lines I found it is a great challenge and the same way great project.

@Wolf_Zipp you are right with differenrials. Years ago I was watchig development of 4wd vehicles and they mentioned for turning and drive on solid surfaces exactly the same suolution with differentials. (I use it whenever creating AWD moc with unequall tires)

Thanks for the comments - its a difficult build and learning process.

7 hours ago, Aventador2004 said:

I know, but it seems 3 is a bit much.

I find your comments about 3 post confusing !!!

Almost stopped any further work on this MOC.

Post 1 Mobile Dockside Crane

Post 2 Outriggers, posted seperatley as wanted to reach a wider range of veiwers to obtain help, which was quicky provided allowing progress with the build.

Post 3  where ??????

If you are refering to the mobile ship loader converyor that was an seperate  topic and MOC which is now dis-assembed to allow buiding this MOC. 
It also had unresloved issues with steering but was a good learning curve as it allowed me to not hit as many dead ends during this build especially with the steering.

Edited January 10, 2018 by Doug72

[doug72]

Update:

Outriggers now being installed usings a design based on mocbuild101,s suggestion. (see outrigger help post)
Feet are raise & lowered by M motor, still working on a way to swing out outriggers using an M motor, at present only by hand.

May build the upper rotating part of the crane as per this Kone Cranes example, much easier to build a square tower than Liebheer version with its round tower.

I also like the outriggers which could either use the the gear rack (18940) with housing (18942) or use the outrigger system on the 42009 mobile crane, but no space in under carriage for either without a full re-build of the under carriage.

Edited January 10, 2018 by Doug72