Luffing crane - a perfect fit to 42078

[pleegwat]

Decided to try this build based on the uploaded LDD, and going pretty well so far. I still need to do the switching section, engine section, and outer body. I did note a couple of things which I'll probably adjust:

• The 12/24 or 16/20 meshing problem you mention is present in the driveline for the superstructure rotation, and causes noticeable friction. I replaced it with a single 12/20 mesh in my build for now, which runs much better.
• Unless I made building mistakes, in a number of places multiple pulleys with cross holes which rotate at different speeds or even in different directions are on the same axle. I'm worried this will cause friction problems, though I haven't tested this properly yet since I need to go out and buy some wire. I'm also not sure if this would be fixable within the C model limitation, as I'm not really tracking that.

All in all a very impressive design, and my thanks for the freely available LDD.

[johanmyst]

Sorry people,

My project to create a usable instructions is not ended, but very delayed.

To do with blueprint: Container and trailer.

The instructions created from blueprint to PDF are not perfect. Sometimes the pins/part not exactly on place. And sometimes it is difficult to make good instructions.

[Leonard Goldstein]

So many people working on my crane - I hope you all enjoy it 

 

On 11/8/2018 at 7:24 PM, pleegwat said:

The 12/24 or 16/20 meshing problem you mention is present in the driveline for the superstructure rotation, and causes noticeable friction. I replaced it with a single 12/20 mesh in my build for now, which runs much better.

Of course you are right. Could you send a pic of your solution? I would publish an updated version of the LDD if this is ok for you.

On 11/8/2018 at 7:24 PM, pleegwat said:

Unless I made building mistakes, in a number of places multiple pulleys with cross holes which rotate at different speeds or even in different directions are on the same axle. I'm worried this will cause friction problems, though I haven't tested this properly yet since I need to go out and buy some wire. I'm also not sure if this would be fixable within the C model limitation, as I'm not really tracking that.

Correct - all the pulleys with cross holes need to be mounted on separate axles. If not they would produce too much friction and the rotation of the claw will not work properly. It is possible to build this within the C model limitation (I just had the 42055 on the desk while developing the crane).

 

21 hours ago, johanmyst said:

Sorry people,

My project to create a usable instructions is not ended, but very delayed.

To do with blueprint: Container and trailer.

The instructions created from blueprint to PDF are not perfect. Sometimes the pins/part not exactly on place. And sometimes it is difficult to make good instructions.

Maybe you could publish the instruction of the crane without container and trailer? It must have been a lot of work (thanks again!) and I am sure it would be a great help for anyone who will build this crane. Maybe you can include my instructions of the rigging (or link to it).

 

By the way: it could be very interesting thing to skip the C model limitation and make this crane RC. The steering section and the power section of the engine house could be skipped and 6 motors could be mounted directly to the working section. I never tested this and maybe some (or all) functions need a gear reduction.

 

Bye

Leonard Goldstein

[pleegwat]

Basically, I just replaced the 12/24 and 16/20 gearing (2:5 ratio) with a direct 12/20 gearing (3:5 ratio). This works fine in both manual and automatic operation.

I also did a number of adjustments to the wire runs. Top of boom:

Rear of boom, note the extra small wheel to get the winch wire to run (mostly) free:

For propulsion, I eliminated the two large wheels and replaced them by small ones in the legs, but I'm still doubtful whether this works:

Overview shot. I tried to work the stickered parts in as nicely as I could, and think I did pretty well.

 

Some functions work better than others:

• Boom elevation, in either direction, causes parts of the gearbox to work themselves loose.
• The winch sometimes runs into a hump and needs to be nudged along; that's probably due to how I tied the rope.
• Rotation worked pretty well until the two-and-a-half loops worked themselves into a knot; a solution with multiple pulley wheels (like on the other end) may work more reliably. The knot causes problems in some places, mostly all the way at the top where it won't go over the pulley.
• Propulsion just doesn't.
• Rotation and open/close work fine.

I'll let my thoughts run on a better gearbox solution. Probably non-C-model by adding two extra clutch gears. Or possibly I'll just give up, shove in 6 motors and 2 sbricks, and call it a day.

[Leonard Goldstein]

19 hours ago, pleegwat said:

...

For propulsion, I eliminated the two large wheels and replaced them by small ones in the legs, but I'm still doubtful whether this works:

Some functions work better than others:

• Boom elevation, in either direction, causes parts of the gearbox to work themselves loose.
• The winch sometimes runs into a hump and needs to be nudged along; that's probably due to how I tied the rope.
• Rotation worked pretty well until the two-and-a-half loops worked themselves into a knot; a solution with multiple pulley wheels (like on the other end) may work more reliably. The knot causes problems in some places, mostly all the way at the top where it won't go over the pulley.
• Propulsion just doesn't.
• Rotation and open/close work fine.

I'll let my thoughts run on a better gearbox solution. Probably non-C-model by adding two extra clutch gears. Or possibly I'll just give up, shove in 6 motors and 2 sbricks, and call it a day.

Hi @pleegwat,

many thanks for your input! I know there is room for improvement in the gearbox. The price you have to pay for the limitations of a C model ...

 

Anyway I try to give some hints to make it work:

To make the boom elevation work better I strongly recommend to use some counter weight. As you can see in the picture below I uses six old batteries (3 in each pair of shovels).

 

When explaining the rigging in the earlier post I forgot the rigging for the propulsion - sorry. Here it is:

First remove the winch for the propulsion.

 

Now take a rope (about 3 meters long) and knot the center of it to the middle pulley.

 

Take one of the two ropes and wind 0,5m of it between the 2nd and the 3rd pulley (the 3rd is hidden in the picture below to show the rope!).

Now you can mount the winch again and roll the two ropes down to the wheel/rails. The trick is you have two winches in one. With rotating the axle one of it winds, the other unwinds at the same time.

Do the same for the other side of the bridge. At the end of the rails the ropes have to be fixed and you can adjust tension if needed.

 

I really like your idea to eliminate the pulleys in the middle between the legs. To avoid any friction I would recommend to roll the ropes like this:

The ropes can be rolled directly from the winch to the wheels. I think this is the most effective way and much smoother than my native solution.

 

 

 

Finally the knot of the loop:

I know this is a problem especially at the driving pulley with 2,5 winds. There is a solution to make this work better - but it breaks with the C model conventions. I used this for the 42042 (which I modified with a similar loop to open/close the claw). Use a rubber tire instead of the pulley. The much better friction coefficient makes it possible to reduce the 2,5 windings to 0,5 windings. Of course you will need some guides to prevent the rope from falling of the tire.

 

Regards

Leonard Goldstein

 

 

[Leonard Goldstein]

Hi @pleegwat,

I integrated some of your suggestions into to LDD: https://bricksafe.com/files/Leonard_Goldstein/luffing_crane/Luffing-Crane_42055-C-Model_by_Leonard_Goldstein.lxf

 

The gearing for the rotation of the super structure is changed. As there is a change of direction I also moved the bevel gear at the front from top to bottom to compensate this.

 

The pulleys between the legs are no longer needed and I changed the structure like this:

 

Concerning the other changes I am not sure if they can be done within the C model limitation - so lets say they are optional 

 

Regards

Leonard Goldstein

 

[Skeltertje]

Hi, As I really like the design and HUGE size of this crane I wanted to build it. The LDD was great to use and a good help during the build.
As I experienced the same issues with the gears skippings and slow movement I decided to rebuild the gearbox, but still remain within the original design and keep it a true C-model

The results:

The gears stay in place due to direct motor mount and reinforced structure holding the gears. Also moved some of the gearing down to the crane house, removing the forces away from the gearbox driveline.

The release handle for the containers is changed to manual, as it's light and only requires 90 degrees movement of the lever..

The propulsion handle works only one direction, but as the direction switch on the battery box can be used now to change motor direction the crane is driving both ways.

The other gears, made reinforcements to keep them in place and moved the angled axles out.

 

And the changes in the cranehouse:

 

Also changed the locking of the gearbox top the cranehouse by removing the 4m axles and replacing them with 3m beams with 3L connector pins

                           

The top of the boom I used Pleegwats' modification adding the other wheels:

 

Here's the link to the modified LDD file https://bricksafe.com/files/Skeltertje/Luffing-Crane_42055-C Model_v2.lxf

I checked the 4205 A model part list which I pulled from an other LDD file and all the parts used for the crande are also in the original set,
I guess this means the crane remains a true C model..

Again, I really liked your design Leonard and after the modifications done now it also is fun playing with it!

[Leonard Goldstein]

Hi @Skeltertje,

wow, that looks great. It seems you spent a lot of time to improve the crane 

I really would like to test it myself - but on Monday I am "free of LEGO": 

 

 

Have fun with the crane (I did !!).

 

Leonard Goldstein