GBC Module - Drag & Tilt (Fixed Video)

[LegoGBC]

My new GBC Module(s). These are actually two modules working together,both using the same motor.

The tricky part was to sync everything up - making the motor switch the cart direction just when it reaches it's extreme.

Everything stays in sync without any drift (tested for ~2 hours,stays in perfect sync)

The motor always spins in the same direction.

Here's the video

Thanks for watching!

(It's very hard to name GBC modules )

[Chilly]

Cool. And so nice to see a post that isn't construction vehicles or that other thing that's taking over.

I'm going to have to try some of these, but it's too nice to be indoors in the summer. Have to wait for cold weather and a roaring log fire. Not to self - buy some balls/beads before winter.....

[Yiharua]

What I most like about it is the changing direction mechanism. It works perfectly well.

Congrats ;).

[aeh5040]

Genius! I love it. Reminds me a lot of some of the creations of the legendary akiyuky, especially these:

[LegoGBC]

Genius! I love it. Reminds me a lot of some of the creations of the legendary akiyuky, especially these:

Thank you!

[doug72]

I have reverse engineered the video and finally managed to get the reversing mechanism to work smoothly but now struggling to get the hoist drum to synchronise the trolly up & down the ramp.

After every cycle the trolly shifts position gradually going one way until rope on the drum winds on the other way and the other way on the ramp.

So far have not found a gear combination or drum diameter to keep the carriage in step repeatedly.

Are there any instructions for this or does anyone know the gearing from the motor output to the rope drum - required to operate the trolly hoist so the travel back and forth is always the same and stays in sync.

In the video unable to see the gear drive.

Don't need the swinging arm to transfer the balls - they will just drop onto a chute to return the balls back to the Bucket Wheel Lift I have already built.

Edited May 15, 2016 by Doug72

[DrJB]

In principle there should be two options to 'synchronize' motions of two mechanisms driven by gears.

1. Make sure the gear ratio is fixed and there is no 'drift'.

2. Have one mechanism 'trigger' the other.

Option 1 is rather simple. For option 2, it should be feasible to trigger the arm (up motion) when the cart for example is at 75% of its travel down the slope.

I think in this case, where synchronization needs not be very precise, the second option is viable. Of course, the devil is in the details as they say, and I can't think (for now) of a mechanism that does that.

[Captainowie]

I think that the original mechanism doesn't sync up exactly either - you can see the white clutch gear that allows the whole mechanism to continue operating when the tilt arm is at the bottom position.

[doug72]

Thanks DrJB & Captainowie:

I am only using the first part of the mechanism i.e. the trolly up & down the ramp.

The second part with the swinging arm will NOT be included - balls will travel on by gravity.

I have tried many permutations including using a rack rail system with the gear on the trolley operated by a 32L axle & sliding 8T red gear to raise & lower the trolley with trips each end to reverse the rope drum, but did,nt work very well !

Rack system didn't work so reverted to a rope system.

I will try to devise a gear system & drum diameter that allows easy changes to be made.

The ramp will have an approx. 45 deg slope.

Also found motor HAS to rotate in one direction only otherwise the arms moving the change over rod jam.

To ensure motor only runs one way - stops prevent the battery box and PF switch from being push to the incorrect position.

I'll post a photo of progress later.

Edited May 16, 2016 by Doug72

[Captainowie]

Hi Doug.

My apologies, it seems I latched onto the word "synchronise" in your post, and didn't actually read what you were asking.

If you're finding that the trolley doesn't quite get back to where it started after one cycle, then your problem is likely that your direction-changing gearbox is spending slightly more time in one direction than in the other. If that's the case, then I don't think there's any combination of drum diameter and gear ratios that will compensate for that.

I'd suggest having a closer look at the positions of the cams that switch the changeover catch back and forth to see if there's any unevenness there.

Hope that helps

Owen.

[doug72]

Hi Doug.

My apologies, it seems I latched onto the word "synchronise" in your post, and didn't actually read what you were asking.

If you're finding that the trolley doesn't quite get back to where it started after one cycle, then your problem is likely that your direction-changing gearbox is spending slightly more time in one direction than in the other. If that's the case, then I don't think there's any combination of drum diameter and gear ratios that will compensate for that.

I'd suggest having a closer look at the positions of the cams that switch the changeover catch back and forth to see if there's any unevenness there.

Hope that helps

Owen.

The cam postion is very tight even after improving the one as shown in the video

I thought I had found the fault in that I was taking the output to the rope drum from the crown gear wheel diven alternately by the change over c/o 16T & idler 16T gears so took the output from one of the idler gears driving the red axle instead.

No improvemenst problem still there - I think its due to the inherrent lost motion in the change over clutch gears causing the output to advance slightly every cycle.

The actual movement of the change over rod is very smooth and positive - problem lies in the c/o gear box lost motion

Can't figure put how it seems to stay in sync in the video !

Going to try a c/o system that the trolley activates at each end of its travel by using a 32L axle with trips down the side of the ramp.

Its try, try & try again until I succeed.

Here's a couple of photos - the red axle is the output to the rope drum.

IMG_3560 by Doug Ridgway, on Flickr

IMG_3559 by Doug Ridgway, on Flickr

Doug

Edited May 16, 2016 by Doug72

[doug72]

FINALLY got the ball transfer trolley to repeatedly traverse back and forth between load and unload points.

Tried an attempt using levers and a trip bar to operate the change over mechanism but not reliable and often stalled when c/o stuck in the neutral position.

Could’t get the trip levers to flip the red sleeve to alternate engage positions due force required to overcome the ridges on the drive sleeve.

Modified a spare sleeve by filing off the small ridges which allowed trips to push the c/o red sleeve fully to engage gears but then tended to slip out again as trolley moved the other way.

2nd attempt abandoned !

Then I recalled my horizontal tower crane MOC which used friction pulleys and braided rubber cord to traverse the hoist trolley.

Successful attempt:

Using the proven c/o mechanism I made up a test rig as shown in the photos.

The reversing output from the c/o drives a friction pulley used to drive the cord connected to the trolley carriage.

After several gear combinations and pulley diameters arrived at a gearing that gave constant travel back & forth.

The c/o unit continues to turn the drive pulley a bit more after the trolley hits the end stops (2lx4L lift arms).

The two white 24T clutch gears are used back to back to form a pulley as they proved to be ideal diameter for the cord drive.

The drive cord has to be adjusted to give just enough tension to move the trolley but be able to slip on the drive pulley when trolley reaches the end stops.

Found Lego wedge pulleys tend grab the rubber cord and don’t allow it to slip.

There is a dwell at each end of travel, to give time to auto load balls and then unload them.

Next step is to postion the transfer track to about 30 degs and connect it to output from my Bucket Wheel ball lift.

IMG_3561 by Doug Ridgway, on Flickr

IMG_3563 by Doug Ridgway, on Flickr

When all connected up to BW Ball Lift will post a video.

[doug72]

DMRC - Video

Marble Run Contraption complete - after a lot of tweaking now runs fairly smoothly.

Bucket Wheel lifts balls up onto the transfer conveyor which then drop down to the loading area for the dog cart.

The dog cart pulled up & down the incline and is driven by M motor via a change over mechanism.

The c/o mech. is based on the one by Lego GBC with some slight modifications to the c/o rod and cams.

At top of incline balls drop on the ball guides and roll back to the start.

Currently glass marbles used ( which had to be checked for diameter ) to ensure no jams.

Hoping to source some plastic beads to replace them.

One thing had to ensure was that the switches on the battery boxes can only be on at one position and block the other way,

Had a spectacular desintergration of the bucket wheel when it rotated the wrong way !!!!

[m.e.d.i.a.]

[/m.e.d.i.a.]

[doug72]

Substitute Lego Balls

Recently ordered & received 14mm diam. white acrylic beads from www.etsy.com (craft material website) to replace the glass marbles I was using on my marble run contraption.

The ones I got came from a firm in Greece.

Tried them but found that with their weight much lower than glass marbles that they behaved much differently often falling off or jamming.

I had to modify the loading and unloading mechanisms for the various sections of the marble run.

Bucket Wheel: loading gate and collection hopper re-configured. Trip lever adjusted to give correct timing as new balls roll and drop slower than glass marbles.

Incline lift: Previous loading gate only allow one ball at a time to enter the lift trolley, changed to 2 per trip but balls tended to back up on the conveyor section.

Finally made a loading gate that allows up to 4 balls per trip to load.

Ball run slopes also had to be made steeper as the hole though the center of the bead sometimes caused them to stick until struck by next ball that came along.

Next challenge to build a scissors lift section.

[doug72]

Update:

Found that over time the change over mechanism built of studded Technic parts tended to get out of sync. due to cams shifting and also to fall apart if any jams occurred.

I set out to build a more robust mechanism and would cycle repeatedly without any drift or jamming using studless technic using 5L x 7L frames for a sturder construction.

The change over uses the new type change over with Red clutch gears and white sleeve and is moved backwards and forwards using a worm driven crank arm.

The C/O shown uses a 24T gear with two 8T gears in order to keep crank arm axle at correct position.

If a 40T gear is substituted then the dwell time at each end of trolley travel increases.

The drive pulley diameter has to be selected to give correct travel required with a slight over run allowing the elastic drive cord to slip when the trolley end stops are hit.

Ball loading can be adjusted to transport between 1 to 4 balls at a time.

Side View:

IMG_3676 by Doug Ridgway, on Flickr

Overhead view:

IMG_3677 by Doug Ridgway, on Flickr

Edited June 22, 2016 by Doug72