GBC Square Drive Module,s

[doug72]

GBC Square Drive Module without reversers (WIP)

Following the success of my vertical tower ball lift which did not use  a reverser or reverse the drive motor,  I am making an attempt to build a Square Drive GBC module as shown in image.

IMG_8462 

“It has taken a lot of time & effort to get the ball carriage to traverse around the circuit without jamming as it is attached to the chain belt. 
Various guides & supports were required to keep the ball carriage hanging correctly orientated.

L motor drive with 20:1 reduction & module can be be run in either direction..

Now the difficult stage - how to arrange the ball loading and discharge points.

Comments and sugggestions welcome.

Edited February 17, 2022 by Doug72

[Thierry-GearsManiac]

I can imagine the difficulty of keeping the ball carriage horizontal all the time, especially when traversing the corners, when it disengages/reengages between horizontal and vertical guides.

On my side, I would have thought about another solution, but with the drawback of hiding the nice simplicity your main mechanism :

the ball carriage would slide on a horizontal rail, and this horizontal rail would be able to be lifted up and down (of course passively, by your chain-driven carriage) while kept horizontal, thanks to some left/right synchronization mechanism (several solutions : double rack-and-pinion where the left and right pinions are synchronized by an axle, adjacent parallelogram linkages, scissor mechanism, pulleys and cables, accordion door structure etc...).

Of course, these mechanisms are passive (they don't drive the carriage by themselves, otherwise it would defeat the purpose of your main mechanism). but one of them would prove to be the most compact and reliable.

[doug72]

Thanks for your reply and comments.

Managed to get the carriage to traverse around the system by adding additional guide beams etc.

The main problem is the turns when using the medium size sprocket wheels.

One other problem is some Lego rounded parts stick out a tiny bit and the carriage would catch on them and tilt. Now resolved

I am now building Version 2 using large sprocket wheels which is giving much better belt tension and the larger radius at the tuns which should make the module perform better.

IMG_8466 

Edited December 10, 2021 by Doug72

[Thierry-GearsManiac]

The chain tension indeed does match perfectly with the fixed sprockets' positions (I can't find the right way to translate) : it's often hard to adjust by trial-and-error the spacing between sprockets in order to achieve the right tension, especially when a spring-loaded tensioner is not an option like here.

I wonder if some people already wrote some formulas for this, for the various kinds of chains and the corresponding sprockets, knowing their dimensional features.

The support for the horizontal sides (especially the upper one) seems also nicer and "falling" at an exact position too.

And meanwhile I found another crazy idea for maintaining the horizontality of the carriage, which this time could even add a nice visual effect without hiding the main mechanism : it relies on two "circular translation arms" in series (I should post some sketches later because pictures always speak better than words), one end fixed at the center and the very opposite end on the carriage's pivot.

 

[doug72]

@Thierry-GearsManiacThanks, for your idea I think I understand what you mean, & will try it out.

I tend to build by trial & Error Then modify until happy with the result.

The build has become a bit too unwieldy., so starting afresh.

Have a possible solution for chain tension which can be adjusted by using thin legal Lego parts.

Keeps me busy during the current times.

Doug.

 

 

 

 

 

 

[Thierry-GearsManiac]

7 minutes ago, Doug72 said:

@Thierry-GearsManiacThanks, for your idea I think I understand what you mean, & will try it out.

OK... And also, if the two arms end up being too bulky, then they perhaps may be replaced by a single extensible one : 90° gearings at both ends and an extensible shaft between them (if one can design its sliding coupling with a sufficient stroke).

 

I'll eagerly follow your work...

[doug72]

Track tensioning:-

Have come up with a method using small shock absorbers to keep the track taut and eliminate the sag when using large sprocket wheels.

Test rig made and keeps track links taut. Support beams for the track now are now in line with side of the track.

Next step is to re-build the main structure using four large sprocket wheels and four track tensioners

This could also be used with tracked vehicles such as tanks , crawlers etc.

Ahead view:

IMG_8469

 

Underside view:

IMG_8470

 

Front View:

IMG_8471

 

Rear View:

IMG_8472

Edited December 13, 2021 by Doug72

[Zerobricks]

Nice mechanism, though I think having springs on one side only would be enough.

[doug72]

12 minutes ago, Zerobricks said:

Nice mechanism, though I think having springs on one side only would be enough.

You are correct but might put out the alignment for the side guide beams.

I will try it with track tensioners at the top only to tension the vertical sections of track.

 

 

Edited December 13, 2021 by Doug72

[Thierry-GearsManiac]

As promised, here is a quick mock-up of the "double circular translation arm" for keeping the carriage horizontal without guides :

The 5x7 frame represents the fixed center and the quarter ellipses represent the carriage.

The achievable distance range (from 13 to 21 studs in your model) required gears bigger than Z40 (if we minimize the number of idlers), hence the turntables (here Z56, but one could use Z60 turntables with Z36 gears instead).

It's quite challenging to make this mechanism as slim as possible (in depth and in width) while minimizing the backlash at the same time (less idlers and/or good bracing).

Other implementation variations may follow at a later time (likely after Christmas, due to a lack of time). Just tell me if you will still be interested in seeing them in your topic.

 

[doug72]

@Thierry-GearsManiac 

Thanks for explaining that mechanism but it will make the module too front heavy and would need bracing to prevent that.

Please keep posting your ideas on this thread. I have 4 pce. Lego Monoarm with 24T gears  (32311) that might possible work.

Progress Update:-
Meanwhile I have now sorted the layout for the guide beams and the carriage now traverses without snagging at the 90 deg. turns

The track tensioners for the two top sprocket wheels are working well to keep the track from sagging on both upper, lower & vertical runs.

Now working installing the guide beams which are similar to the earlier version, with a subtle guide for the carriage to engage the vertical guide beam.

Next step is to install the guide rails to support the carriage at the lower level.

I will post new images tomorrow of the revised layout.

Edited December 15, 2021 by Doug72

[doug72]

Update:-

Guide track modified and two support legs added to the front to keep i the main structure upright.

Guide beams to baseplate for the lower horizontal section to keep carriage horizontal as it traverses.

Next step is the difficult bit, to arrange the ball loading and unloading stations.

Ball carriage can carry 9 per trip so probably does not meet GBC flow rate of 1 ball per second.

IMG_8477 

IMG_8478 

Video:-

 

 

Edited December 16, 2021 by Doug72

[Thierry-GearsManiac]

I now see the key elements for a good guidance of the carriage :

• the contact between the underside of the carriage and the ground "rail" (the series of tiles) for the horizontal travel at the bottom
• the two lateral guides for the vertical travels; with funnel-shaped entrances/exits for the self-aligning of the carriage

For the top horizontal travel, no need to maintain a tight horizontality of the carriage, because its low center of gravity may be sufficient.

On 12/15/2021 at 7:47 PM, Doug72 said:

it will make the module too front heavy and would need bracing to prevent that.

Understood.

On 12/15/2021 at 7:47 PM, Doug72 said:

I have 4 pce. Lego Monoarm with 24T gears  (32311) that might possible work.

The problem is that the geared sections of these parts won't find any such particular use in my mechanical arm : all Z40 gears rotate freely with respect to all the arm's segments.

On 12/15/2021 at 7:47 PM, Doug72 said:

Please keep posting your ideas on this thread. 

I will indeed happily show a few more mock-ups (or paper-drawn sketches at least).

[doug72]

@Thierry-GearsManiac  "For the top horizontal travel, no need to maintain a tight horizontality of the carriage, because its low center of gravity may be sufficient."

I tried installing a guide beam for top horizontal run but carriage kept catching and tipping over so removed.

Now trying to figure out the ball loading and unloading 

Doug

[Thierry-GearsManiac]

For the loading and the unloading areas, the setup from the original module seems to do the job. The only remaining concern may be if its lowest height will allow the height of input bin to comply to the GBC standard. Do you see any further difficulty ?

On the video of your first version, I saw the carriage tipping when travelling through the top side because of the guide under its underside : for guiding the carriage there, its top side should have been horizontal and flat, and with a rail above it.

 

And now, as I managed to build most of the mock-ups of the translation mechanisms I thought about, I'll introduce them to you

(reminder : the key idea is that the gear ratios must be +1:1 for output/elbow and elbow/input)

1. The double arms :

above is my first build (spur gears), and below is another one, bevel-gears-based (just notice the Z28 at the elbow, whose both sides are used).

2. The rhomboid chain :

Inspired by this video, at 13:10 : https://youtu.be/PM4_9JnTq-E?t=790

In fact, this idea is a variation of a double arm with +1:1 chain drives on each segment. The chain perimeter will stay constant for any folding state of the rhombus linkage because the input, output and idler sprockets are of the same size.

The linkage can also be parallelogram-shaped (less aesthetic because of the symmetry loss) or even "kite"-shaped (symmetrical)

(note that the use of torque-limiting gears for the idlers is purely aesthetic : this special function is not used)

3. The single extensible arm (exploded) :

At both ends, you have 90° transmissions which, when combined, achieve a +1:1 ratio.

Between them, an extensible axle with a big enough ratio (in general, slightly higher than 2:1 because the overall ratio between folded and unfolded state --including the non-extensible ends-- is around 2:1). Two solutions presented :

• above : a double sliding coupler (several implementations exist ; mine uses several 3-stud half-thickness liftarms on the center element and https://www.bricklink.com/v2/catalog/catalogitem.page?P=98585 (looks like the hub of a Z36 gear) on the ends)
• below : the mix of a Sarrus and scissor linkage.  Similar to this : https://www.youtube.com/watch?v=DasxDJJF2hk . Uses both kinds of 120° connectors

I didn't build the latest mock-ups at the right dimensions (i.e. the ones which would fit the real square tread) : they were built quickly, only to show their way of working.

 

 

Edited December 17, 2021 by Thierry-GearsManiac

[doug72]

9 hours ago, Thierry-GearsManiac said:

For the loading and the unloading areas, the setup from the original module seems to do the job. The only remaining concern may be if its lowest height will allow the height of input bin to comply to the GBC standard. Do you see any further difficulty ?

On the video of your first version, I saw the carriage tipping when travelling through the top side because of the guide under its underside : for guiding the carriage there, its top side should have been horizontal and flat, and with a rail above it.

 

Thanks for your ideas, I will study them and see if I have enough gears.

Meanwhile I have come up with a way to keep the carriage horizontal on the top rail for most of the travel, just a slight tilt as it enters & leaves the support rail.

IMG_8480 by Doug Ridgway, on Flickr

Re GBC compliant loading / discharge.

I have several designs of the GBC Inbox all with 10L entry height andI need to figure if front or side position to load balls is best.

Carriage at the moment can hold 9 balls but could be widened to carry 15 balls. I have an inbox that releases 15 balls per loading cycle.

Edited December 18, 2021 by Doug72

[Thierry-GearsManiac]

5 hours ago, Doug72 said:

Meanwhile I have come up with a way to keep the carriage horizontal on the top rail for most of the travel, just a slight tilt as it enters & leaves the support rail.

Understood (and I haven't thought about this very simple solution which fits the existing design).

The front/back slight tilt may be caused by the 0.2L excess height of the guide, which is 2.2L high (1L for the white beam below, 1.2L for the brick height of the guide). Replacing the white beam by two plate layers will remove this excess height and may solve this little issue.

[doug72]

2 hours ago, Thierry-GearsManiac said:

Understood (and I haven't thought about this very simple solution which fits the existing design).

The front/back slight tilt may be caused by the 0.2L excess height of the guide, which is 2.2L high (1L for the white beam below, 1.2L for the brick height of the guide). Replacing the white beam by two plate layers will remove this excess height and may solve this little issue.

Your solution works fine, tilt is now very small,  now, tested with carriage holding 16 balls.

Edited December 18, 2021 by Doug72

[doug72]

Progress update: Ball discharge unit :-

It took  a long time to get the correct arrangements for the carriage fingers arms to align with the static fingers arms.

15 balls per trip are unloaded into a GBC compliant in box which modified with a tilting section to release 15 ball when the trip bar is activated.

Inbox can also be positioned sideways as shown or inline.

Static finger arms.

IMG_8481 

Ball carriage about to pass through the static fingers and drop balls which roll down to exit the module.

IMG_8482 

Short Video: showing balls rolling down to the next "in box".

Next stage
Build the input ball loading unit. I hope to be able to keep the ball input height at 10L.

 

Edited December 27, 2021 by Doug72

[doug72]

Build Completed and tested OK - Photos & Video added.

Ball loading in Box now installed and after a lot of alterations was functioning as required.

In box is GBC compliant at Entry 10L height. Entry Width 8L and length 16L.

Four fixed bars with ball retainers at the end of the free arm.

The transfer carriage has three arms.

Various means to prevent balls escaping had to be fitted.

Transfer of 60 balls is too long at 68 seconds.

To meet GBC 1 ball per second the speed needs to be increased,

At present drive is using an L motor with a 20:1 reduction.

Possible solutiuon:  to meet 1 ball /sec.

1/. use L motor with a 16T gear with worm drive to give 16:1 ratio.

2/. Widen the input box & discharge box.

3/ Have two carriages ?

Photos.

 

General View:-

IMG_8487

 

Loading input box.

IMG_8488

 

Discharge box

IMG_8489

Carrier arms passing through the fixed arms.

IMG_8490 

 

IMG_8491

 

Video: Filmed using hand held camera in right hand & loading balls using left hand hence a bit shaky !!

 

Edited January 1, 2022 by Doug72

[doug72]

Build 100% complete after further Improvements:-

Tried with two ball cradles but still unable to meet the 1 ball per second.

So four  Ball cradles are now installed, equally space out on the chain belt and can carry up to 6 balls each.

In Box side fences raised to stop balls over topping.

With the L motor at full speed and 20:1 drive ratio, the transfer of 60 balls is 45 seconds.

Thus the Motor can now be regulated to give 1 ball per second

Module Tested and is very smooth running.

Still hunting for lost balls !!!

IMG_8494 

Edited January 2, 2022 by Doug72

[doug72]

GBC Square Update:- intermitent problem with balls dropping.

Occasionally a ball would drop from a loaded ball carrying cradle and land on the one that had preceded it.

As the ball cradle tried to rise up at the loading point the rogue ball  then jammed the system, causeing the worm drive gear to skip on the 20T gear.

If too many balls are in the input box the ball cradle lifts tries too carry  too many balls which drop off on the horizontal run or at the unloading point where some balls fall backwards and drop onto the cradle below.

Two solutions:-

1/. Install a system to only load 6 balls per cradle but synchronisation would be very difficult. - rejected.

2/. Add a slope below the top rail to catch any balls that fall direct to roll down to the output chute.

Modify the ball carrying cradle to restrict the number of balls to six and prevent any of them rolling off backwards.

Solution 2 tested and module now running OK.

IMG_8495 

Edited January 16, 2022 by Doug72

[arieben]

I won't lie, I was doubting this module in its beginning stages. It has turned out to be a great success and a beautiful smooth mechanism. Great work.

[doug72]

15 hours ago, arieben said:

I won't lie, I was doubting this module in its beginning stages. It has turned out to be a great success and a beautiful smooth mechanism. Great work.

Thanks for your comments,

On all my GBC builds now, I try to eliminate the need for a reversing the drive.

I aways review a build and tinker with it until satisfied. It can take a long time to get reliable running without jams & losing balls.

 

Edited January 17, 2022 by Doug72

[Thierry-GearsManiac]

In order to eliminate (or at least to mitigate) the falling balls problem, would it be a solution to replace the cradles' outer fingers by walls = kinds of "armrests", like in the original design ?

On my side, I think I should take up the challenge of building a one-high-speed-cradle variant (without reverser of course, and with the goal to test my horizontality mechanism in real conditions), but I expect a lot of falling balls anyway !