Large scale crane boom question

[neoconagenda]

My ship just spent a week or so in the shipyard doing thruster repairs and I could not stop thinking about building a Technic yard crane of my own. I have seen versions of these in the past but not too many at mini fig scale. Everything about these cranes marry perfectly with the technic world, all I need to do is pick a crane and get to work.

I did want to ask if any of you have experience beam building a large scale boom and what issues / limitations I may encounter. This is still in the infant stage and may be the motivation that I need to finally get into using LDraw...

[Alasdair Ryan]

Three major problems are sag,lifting and lowering of the boom and rotating the upper-structure.

Edited August 6, 2014 by Alasdair Ryan

[cheeze]

Is it a crawler or telescopic crane you are looking to build? Each have their own pros and cons but as Alisdair has said about the three major problems these seem to be the points that hinder builders.

My crawler for example can't lift it's own boom from floor level to an upright position yet and it also can't slew with the ballast carrier I have on at the moment but can without. As for sag that's mostly the telescopic booms con where as a fixed boom is most resistant to it. I've lifted 5.5kg and close radius with mine but others have exceeded that twice over. Here's the link to my build so far http://www.eurobricks.com/forum/index.php?showtopic=92480#entry1827106

[Alasdair Ryan]

Alisdair

Nearly spelled it right.

My crawler for example can't lift it's own boom from floor level to an upright position yet and it also can't slew with the ballast carrier I have on at the moment but can without. As for sag that's mostly the telescopic booms con where as a

You would probably be better motorizing the ballast trailer in time with the final slew speed.

For 'big' cranes normally you will need to reinforce a lego turntable or make your own.

[cheeze]

Silly predictive text Mis correcting. Yeah that's my plan once I figure a way to do it. I've cheated and used a roller thrust bearing as it cuts down the friction. But it's hidden from view.

[neoconagenda]

I hate to use stock photos but the image is pretty close to what I am talking about. I failed to snap pictures prior to leaving the yard...

[cheeze]

Its a basic pedestal marine crane, should be easy enough if you plan it right, i never used LDD with mine just improved as i built, Have a look at this one i looked at while i was building for ideas http://www.texbrick.com/model_marinecrane/

[neoconagenda]

This answers a ton of questions that I had dealing with the boom and roller ring design! It also shows me that a boom can be large scale and functional.

[cheeze]

I cheated and used one of these http://s.hswstatic.com/gif/bearing-roller-thrust.gif,

[neoconagenda]

I know I am going to have to break the rules to do this at some point but anything above 99% stock Lego will make me happy. And with a few thousand pieces I figure I can keep it above 99%...

[neoconagenda]

Did not want to leave this open... So after considering the cost, the cost, and the cost of moving this idea to completion I have to say its going on the back burner for now. I am thankful for the fast support with my initial questions, it lets me know that when I get ready to attempt this again this community will be here to help!