[MOC REVIEW] Grove GMK6400 Mobile Crane

[Blakbird]

Does this have a support vehicle to carry the extra bits like the counterweights? (I know I'm opening up a huge can of worms here)

Yes. The counterweight is not carried by the crane when moving to another site over a roadway.

[efferman]

indeed blakbird.

the counterweight is finished, including a second winch for an optional flyjib. here is the lxf

[DanFraser]

Yes. The counterweight is not carried by the crane when moving to another site over a roadway.

So that needs building as well then!

[DoGoods]

the counterweight is finished, including a second winch for an optional flyjib.

How is the second winch controlled? Are we going to need an sbrick to control the extra function?

[efferman]

it has his own receiver, theoretical the chassis receivers are not in work during crane working.

i have made a first version of instruction, excluding counterweight, can you please take a look on it?

http://bricksafe.com/files/efferman/How%20to%20make%20a%20Grove%20GMK%206400%20Uppercarriage%20wide.pdf

warning, it has 160mb

[gerger]

It is amazing that the project has been on going! So do I for the carrier. After finishing MarkII, I built set 42030 and I feel ashamed that my MOC performance is way under standard lego functions. This caused me to further look into details of each function. I rebuilt the model a few times with different setting and I discovered a critical design issue about single long driving shaft with different turning radius axles.

When steering, different axles run at different radius and stress will build up along the driving shaft. After prolonged steering, stress will stack up to a point that it causes the carrier to slow down, gears slipping in differentials and axles twisting + gears damge. It’s lucky that MarkII wobbly steering racks setup has absorbed most of the above issues but it doesn’t help improving the functions. The only solution is to have individual driving motor for each axle. That mean I have to give up MarkII suspension to allow more spaces for motors at different axles. It is a painful decision but worthy to try out.

To free up spaces, I use simple solid axles with 3 XL motors for front, middle and rear axles. The overall carrier length is increased by 2 studs. Stress issue is completely gone; driving speed is much faster as XL motors are directly attached to axles without the need of gearing down; steering is smooth and responsive with the help of 2 servo motors. A manual switch between the steering servos is added such that normal steering and crab steering can be selected manually by sync or reverse the servo’s direction; The extra space also allow more gearing down for outriggers to self lifting the whole carrier + superstructure (without extending the outriggers horizontally) ; and enough spaces for double turntable to stabilize the superstructure.

When all the above functions added together, I feel like I am playing with a QC tested lego set now. I am still tidying up the cable routing and reattaching the body works and I will create a video update shortly to demonstrate the improvement.

[kisper]

What a beauty in the making :)

[afol1969]

Hi gerger,

So you completely modified the carrier? And what about the wobbly steering? Is it worth to review/modify the instructions? If so, let me know, I've still the crane assembled, I'm planning to modify the superstructure with the Firgelli actuator. So I can do both, and make a complete instruction update - if someone can help to convert the LFX file into LDRAW.

Greetings

Alex

[legolijntje]

This topic is amazing. It's wonderful how everyone works on different parts of the model to make the whole model better and better.

However, I can imagine that it's quite annoying for people who make instructions if the model changes everytime

Maybe, the first post should include a list of all the different "modules" that have been created so far?

[gerger]

I take away independent suspension and use solid axle. Steering is similar setup as in 42009. i.e. no more wobbly steering. 1st & 6th axles steering rack are 3stud apart from drive axle; 2nd and 5th axles are 4 stud apart, 4th axle is 5 stud apart. 3rd axle is solid axle without steer. I keep the same wheel hub as in 42000 because the wheels are more securely mounted. Let me have some screen capture from the lxf file tonight. I can do a LXF to LDraw conversion again if this modification is worth for the community to update.

[Jeroen Ottens]

I take away independent suspension and use solid axle. Steering is similar setup as in 42009. i.e. no more wobbly steering. 1st & 6th axles steering rack are 3stud apart from drive axle; 2nd and 5th axles are 4 stud apart, 4th axle is 5 stud apart. 3rd axle is solid axle without steer. I keep the same wheel hub as in 42000 because the wheels are more securely mounted. Let me have some screen capture from the lxf file tonight. I can do a LXF to LDraw conversion again if this modification is worth for the community to update.

How does the crab steering mode work? Does it use the same ratios as with normal steering?

That would result in a poor crab steering performance I suspect. Or do you use the same steering ratio for each wheel when crab steering? If so, how do you switch the ratios when going from crab to normal and vice-versa.

[afol1969]

However, I can imagine that it's quite annoying for people who make instructions if the model changes everytime

Indeed! So it's better I wait some time that all weak points of the crane are solved. Once you give me green light for an update, I'll disassemble the complete model to review the instructions.

Greetings

Alex

[Mestari]

It would be even better to have two versions of the undercarriage- one with suspension as it is now and one with solid axles. Then have it published on rebrickable as two different models.

A link to this thread in description would be great:)

Can't wait to have it happened and have all the parts to build this beauty:)

Thanks to all who made it possible!

[JDC]

So at this point in the project, the instructions should be gerger's revised carrier, efferman's revised superstructure with new counterweight and flyjib winch, and his large LA from Shapeways for raising the boom. That would make quite a sophisticated crane.

[camaudio]

It looks like gerger is also designing a removable stacked dual turntable?

[Saberwing40k]

I think something good to try with this crane is to have the outriggers automated, so they move out and lower automatically, controlled by one motor.

[gerger]

Here you are the video to show the actual performance of basic drive & steer, and outrigger self lifting of the solid-axle version or so-called GMK6400-MKIII.

I add crab steering as a bonus because on paper the carrier shouldn't work without 3rd and 4th synchronizing with the other axles. But in real test, it passed the friction limit and is driving ok.

A manual switch hook under 3rd and 4th axle to control different mode of steering.

Normal steering with optimized angles.

Crab steering.

There are also minor improvements like dashboard, lower seating, better roof bodywork mount, etc because more spaces are available after moving XL motors to the back.

The carrier+superstructure are simply too heavy and bend all outriggers when fully horizontal extended. They works well when retained. (see video above)

Adding counter weight is a way to balance the superstructure directly but it also add loads to carrier as well as to outriggers. Therefore I made an option to include double turntable setting in the carrier such that it is possible to extend the support to the turntable without adding too much weight. It works the best if both can apply together but I worried if the outriggers can self lifting as it is. I haven't work into details modifying the superstructure and I am sure someone will and it does already happening in the forum.

Finally LXF here.

[efferman]

thanks for the lxf

[Eigenbroetler]

wow, i like both versions, i really liked the one with suspension, but this one seems more payable... well i think im going to stay with the fully suspensioned.

[JDC]

efferman, does that represent your Shapeway's LA?

[efferman]

Yes, it does.

[afol1969]

wow, i like both versions, i really liked the one with suspension, but this one seems more payable... well i think im going to stay with the fully suspensioned.

After viewed the videos, I more prefer the version without suspensions - the driving/steering seems to be much better, and the gear ratio of the outriggers is more accurate. To see the real difference, I'll like to build this carrier version. But I'm not common with LDD and prefer an LDRAW version. The LFX file export was - as always - totally crap. If somebody can make a more or less accurate LDRAW file, I'll do again the part angles reviewing as I made it with the first version.

@efferman: The superstructure without the counterweights on back sides looks much better in combination with the carrier. It's still massive, but it gives a very good impression in the whole construction.

Greetings

Alex

[Jan Smed]

I must admit that I would like to build them both but I have to pick one and as the one with suspensions is already built then that will be the one being exhibited at LEGO World in Copenhagen 2015.

It will be at our LUG Byggepladen's setup and as I wrote earlier it is to show how the communities like Eurobricks join up to make awesome things.

We will try to explain the timeline in this work but if anyone have a good idea then please forward a comment on it. Feel free to use admin@lwfanzone.dk

Only effeman's new uppercarriage is still to be done and hopefully my SBricks will arrive soon.

Efferman; Thanks for the Building instruction for the uppercarriage and boom. To make a complete part list it would be nice to have the lxf file for it like for the new counterweight. Is that possible?

Edited December 18, 2014 by Jan Smed

[efferman]

i think at end of the weekend it is done

[Taiphun]

I'd like to build this, well, start buying parts for it, but I don't know where to start... I've got a Mac but I'm not familiar with what to do with an MPD file. I'm going to start going through the build instructions to compile some parts..

Other thing is, we're in the process of making a big order of parts, where can I find a quick and dirty tutorial on how to best compare what I've got (I've got the current Technic crane and some beams in my collection) but I'm sure I'm missing a bunch of other stuff..

Thanks in advance,