doug72

I,ll see what I can come up with tomorrow, Doug

This should meet your requirement and allow rubber tread to be added on edge of rings. If only a single width of rings required just reduce distance between the two 5 x 7 frames. PS this is just what I need for a projected GBC idea.

Can you give more info what will be attached to the gear ring ? Good idea, tried it and a gear ring runs very smoothly. See image of a couple of solutions - the left one with 5 x 7 frame supports and guides OK and has clearance for 2L axles connecting the segments without snagging. The right would need 1L pins to connect segments to prevent snagging. Idea using all eight 1L roller guides. Using wedge wheels

Is this any use - its an idea I was working on recently for a GBC module.

Check out the video on page 2, it runs very smoothly using gears for support & drive, with wedge wheels to keep the gear ring in place. Slow rotation is because It is worm gear driven but should be able to be speeded up.

Take a look at how I supported a gear ring vertically from inside using gears and wedge wheels. It might work for what you require.

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.

Instead of using a white 3L axle joiner use a 2L axle joiner and Replace the 4L axle with stop with a 5L axle with stop, and add a bush to fill the gap. That way you would be able to use a thin rod to push out the 5L axle with stop. Simple ! Possibly the red 3L axle joiner was not available when set designed.

Yes,

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: 


New part required: 4L axle with stud end, then you would be able to grip with needle nose pliers to pull it out.

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.

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:


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.

These works as well to gently prise the 4L axle with stop out far enough to grip and remove. they have a very sharp fine point.

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.

Wacky Races series is now being aired on Boomerang TV channel in the UK.

In the UK Heath Robinson was a well know eccentric who built all maanner of weird devices and now has a museum about his contraptions. See https://en.wikipedia.org/wiki/W._Heath_Robinson In the 1950, a working narrow gauge railway was built in London for the Festival of Britain- see video,

I have a book that contains thousands of mechnical movements dating back many years.

My idea for contest would be either: A. Something without wheels or tracks but still capable of travel. B. Replicate a mechanical movement. C. Ball transfer device aka GBC but between defined locations within a constrained 3D frame.

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.

https://www.shapeways.com/product/WK3HCKVSK/wormgear-case-3x3x3 Available in white & other colours but not in grey.

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 !

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

Congratulations to all the winners and all who took part. Improved my placing from 11th for TC8 to 4th this time - happy with that.