Mobile Ship Loader Conveyor

[doug72]

Conveyor modular construction:

Uses multiple 11L units designed to give a smooth surface for track belt to prevent snagging in loaded direction or sagging on the return
direction. Each unit linked by beams along top edge.

Edited November 2, 2017 by Doug72

[doug72]

Progress update:

First stage of conveyor built, used small sprocket wheels to lessen the angle the track has to bend backwards.

Guide rails keep track belt in place for outward along top of boom and the return along the underside to prevent sagging.

As per my BCE a track tensioning device added at head of the conveyor boom to ensure track stays tight and drive functions at all boom positions when raised or lowered. 

Each pair of blue pins can hold 3 balls at a time. 
Main issue was stopping balls falling off the sides at the top of the boom.

An L motor drives the conveyer via 8:1 reduction gearbox.
Ball hopper arrangement is only temporary and to be improved.
A lot of bracing required to the hopper and drive unit to prevent droop.

Next step is to build the conveyor extension with a rotating spout from top of the boom

Edited November 5, 2017 by Doug72

[doug72]

Conveyer now almost completed apart from improved loading hopper.

Close up of conveyor drive motor & reduction gearbox

Close up of conveyor adjustable discharge shoot with rotating spout.

Manual angle adjustment of shoot using a small L.A.
Manual rotation of  discharge spout to for even trimming of cargo in the ships hold..

I

Next need to decide which of my MOCs to remove PF receivers from to operate the steering caster wheels !

Edited November 6, 2017 by Doug72

[mocbuild101]

1 hour ago, Doug72 said:

Close up of conveyor drive motor & reduction gearbox

What is that grey part? I've never seen it before... 

[doug72]

57 minutes ago, mocbuild101 said:

What is that grey part? I've never seen it before... 

https://www.shapeways.com/product/WK3HCKVSK/wormgear-case-3x3x3

Available in white & other colours but not in grey.

[mocbuild101]

29 minutes ago, Doug72 said:

https://www.shapeways.com/product/WK3HCKVSK/wormgear-case-3x3x3

Available in white & other colours but not in grey.

Oh, why didn't you make it out of original Lego parts? - I can think of at least one way to make it...

[doug72]

3 minutes ago, mocbuild101 said:

Oh, why didn't you make it out of original Lego parts? - I can think of at least one way to make it...

So can I but not as compact or neat & provides better support for the gears under heavy load.

 Takes for 8T & 24T gears with old style worm gear & to get grey colour I use a paint pen.

Edited November 6, 2017 by Doug72

[mocbuild101]

11 hours ago, Doug72 said:

So can I but not as compact or neat & provides better support for the gears under heavy load.

I can:

Its only 1 stud longer, and perfectly capable of supporting the gears under heavy load - in fact, if you added 2 more 1x4 half-beams, it would make it even stronger!

[Lakop]

Interesting.

H

[doug72]

PF receivers fitted and cables connected ready for testing

Speed contoller used for drive to wheels and conveyor.

Basic controller used for steering the caster units.

 

Had to ensure all caster units were driving in same direction otherwise the drive to wheels fights would each other.
So far so good then problems !

 

Testing drive & steering:

The MOC is quite heavy and when driven the gears for the right angle drives to each caster unit started to skip and pull apart.
Had to revised the right angle drive by using  four LEGO Black Technic Connector Toggle Joint Smooth Double with 2 Pins (48496)

I managed to change these without a major strip down !

 

Now re-tested and runs smoothly, the steering takes some getting used to for the various steering modes.
Straight, sideways, crab, radial & normal as the caster units have to be adjusted in pairs to suit steering mode.

Now have to devise an automattic loading for thr conveyor input hopper.

 

Edited November 10, 2017 by Doug72

[jotta93]

I really like this Doug 

But I have a doubt: a single XL motor drives all wheels right? How did you do that? I assume that when turning the caster units on each side have different radius and thus different turning speeds 

Maybe you have explained this before and I missed it. If so I apologise

[doug72]

17 minutes ago, jotta93 said:

I really like this Doug 

But I have a doubt: a single XL motor drives all wheels right? How did you do that? I assume that when turning the caster units on each side have different radius and thus different turning speeds 

Maybe you have explained this before and I missed it. If so I apologise

Mentioned this possible problem earlier:

"Another problem yet to be tested is when doing radius turns the wheels on the two caster units need to run at different speeds or the tires will scuff - at the moment all wheels driven at same speed by one motor. When wheels are parallel to each other there is no problem.

So I  will test by removing drive to the smaller caster unit or install a differential somewhere in the drive chain but no space to do this !"

-----------------------------------------------------------------------------------------------------

Travels OK forwards, backwards, sideways & crabbing as long as all caster units are parallel and tire rotation all same way.
Possible when they are not parallel that when turning on the spot or for  radial steering the tires will drag, if it does then I will remove drive from the smaller caster unit and test again.
Another possibility is to insert a differential into the drive where it splits to the two caster units.

Had now developed a standard compact caster unit using 49.5 x 20 tires, with drive and steering inputs all mounted on a 5 x 7L frame.

Only mod required is to shorten 5.5L axles to 4L - could be used for a mobile dockside crane with the BWE gear ring  for the turntable.

[doug72]

A re-think has highlighted that when turning on the spot or using radial steering the wheels on each of the caster units need to rotate at different speeds.

OK when all caster unit wheels are parallel but not when radial steering required.

Due to the different positions of each caster unit and the different radius from turning centre point the wheels need to rotate at different speeds to prevent the tires from scuffing.

Solution:

Insert three differentials into the drive chain.
This will mean a re-build of the lower structure with differentials positioned correctly to ensure all wheels turn together in same direction.

Does anyone have alternate suggestions on how to resolve this problem ?

Existing Drive layout:




Proposed Drive layout with three differentials:

Steering modes:

Test build:


Edited November 11, 2017 by Doug72
Remove image file text and insert correct image

[BrickbyBrickTechnic]

Everything is looking good, but one question that might be a bit dumb: why is radial steering not ok?

 

[doug72]

3 hours ago, BrickbyBrickTechnic said:

Everything is looking good, but one question that might be a bit dumb: why is radial steering not ok?

 

At the moment all wheels rotate at the same speed driven by the XL motor.

To prevent scuffing the wheels have to rotate at different speeds as they are are on different radii.

At the moment caster units C1 & C2 are paired and C3 & C4 are paired and C1 & C2 have a larger wheel base compared to C3 & C4 .

When cornering C2 is further out than C1 from the theoretical centre of the turning circle - likewise C4 is further out than C3.

Therefore C2 & C4 have further to travel than C1 & C3 and have to rotate faster to achieve this.

By using diffs. it should be self regulating - in the same way as a steered axle with 2 wheels,  the outer wheel turn faster than the inner wheel when cornering.

Re-build will take a while.

If the two caster paired units were the same size probably would not required the centre diiferential.

Edited November 11, 2017 by Doug72

[doug72]

Mark 2 Drive system:

Re-built using three differentials all driven by one XL motor.

Successful in that now able to perform shallow radial turns but a new problem then occurred !

When on a hard surface, if one wheel loses contact with the ground it spins freely and all other wheels stop rotating. On a surface such as a carpet functions better but still issues.
Rejected !

Therefore decided to replace the single XL motor with two M motors and split the drive.

Each motor drives via a single differential each paired caster unit.
This allows for each caster unit in the paired units to run at different speeds when turning.

As an M motor runs at 272 rpm & XL motor runs at 146 rpm the drive had to be geared down.
Space was quite tight to locate & also gear down the M motors. but keep overall width the same.

 This was achieved by using an 12T gear meshing with the 20T double bevel gear that drives the differential, giving a slightly faster speed.
The upper M motor drives the larger paired caster unit. 
The lower motor is positioned underneath drives the smaller caster paired unit.
Had added advantage of strengthening the connecting frame between the two paired caster units.

Tested and control now is much better when performing radial turns and all the other steering modes. Also able to steer just using the larger paired unit for wider radius turns.

Two basic PF controllers are used for for steering and drive functions with a PF switch to stop  & run the conveyor.



Top view:

Underside view:



Side view:



Edited November 12, 2017 by Doug72

[BrickbyBrickTechnic]

So now radial steering will work just fine, right?

[doug72]

5 minutes ago, BrickbyBrickTechnic said:

So now radial steering will work just fine, right?

Yes,

[doug72]

Radial Steering:
Although radial steering was possible with the original asymmetrical wheel arrangement it proved difficult to control especially if attempted a too tight a turn when one pair of casters would lock up.


So back to the drawing board and a total re-build !

Resolved the problem by eliminating the asymmetrical wheel arrangement.
Re-built using two caster units which have the wheel base of 19L for both front & rear wheel units.
Distance between paired units is 27L for a more stable platform.

I found real machine on YouTube of a Mobile Dockside Conveyor which has such a wheel arrangement.

It is now much easier to steer in all modes. 
Tested and can steer normally with only one set of wheels turned or for tighter turns all wheels are turned but in opposite directions.

Conveyor boom to replace and extend by 11L and try and locate the loading hopper nearer the ground.

Edited November 14, 2017 by Doug72

[doug72]

Update: 
Completed the build and functioned as I intended apart from the caster steering which proved quite difficult to control & synchronise the two steering M motors to achieve the various steering modes.

Now disassembled apart from the four caster steering units which will be used again for my next MOC.
A new topic will be started once I decide on what to build.

Currently developing a steering system for the four caster units that will use only only M motor and via a changeover gear box will be able to perform the various steering modes (1, 2 3 ) except for rotating on the spot.

Steering options.

Mode 1: Two casters units only steered with other pair fixed i.e. normal steering

Mode 2:  All four caster units rotate the same way to provide driving straight / crab / sideways.

Mode 3:  Pairs of caster units steer in opposite directions to give radial steering.

Mode 4:  will not to be fitted
.
This would require each caster unit to turn towards a theoretical centre rotation point and would require a very complex gear selector box to achieve this or use four EV3 medium servo motors & use Mindstorms programmed to control them - probably lack of lack of space to do this unless the MOC is very large.!!

[doug72]

A mechanical solution built to control the caster units BUT takes up too much space and over complicated.
Also has a BIG drawback with the lost motion in the red clutch gears  amounting to 90 degs. when rotation is reversed. 
This means the pairs of steering units will not always stay in sync.

So back to the drawing board.

I have made a mock up test rig using two M motors and two PF switches to control the steering modes.

Output from a PF receiver goes to both PF switches which in turn control each motor, allowing selection of  CW - stop - ACW.

By this means the desired steering modes can be achieved.

With 4 motors plus 4 PF switches rotation on the spot should be possible.

NOTE: Closing down this thread and will be starting a new topic soon for my next MOC which will be a freelance MOC of an RTMDC ????