[HELP] Strong Crane Boom Concept

[efferman]

some of you have maybe seen my video with the

of the xl actuator and how the boom is bending under the load. here are two pictures

do you have any ideas to prevent this.

Edited September 26, 2014 by efferman

[Milan]

Brick built boom will bent much less.Additional reinforcement can be made by rotating the boom by 90 degrees. That way, bending is virtually impossible.

But it requires lots of parts.

[Balrog]

On the first section you should make longitudal reinforcements. E.g. Connect the curved panels on the upper end with beams. Should help a bit.

[efferman]

Milan, something like this?

Balrog, i have beams in longitudal direction on the upper side. unfortunately the gearrack for boom extension makes it hard to connect both sides together.

[Balrog]

I don't see the longitudal reinforcement. Can you post a picture from above?

[efferman]

unfortunately not, because i folow your idea in extreme

this feels solid, but the extension of the extrakting section will be the next problem

[Cumulonimbus]

Is your boom really bending? In your pictures, it looks like the main issue is the play between the two boom sections.

This might be solved similarly to the 42009 outrigger mechanism.

Edited September 26, 2014 by Cumulonimbus

[efferman]

on the second picture in first post you can see a gap between the two curved panels and the bent crossaxle. so the boom is really bent

[Cumulonimbus]

on the second picture in first post you can see a gap between the two curved panels and the bent crossaxle. so the boom is really bent

Oh, your right. I focussed too much on the first picture.

[Balrog]

How many studs does the second stage remain in the first stage?

[efferman]

twelve studs

[Balrog]

So the whole second stage stays in that last segment. Still, I can only think of reinforcing the upper side of the boom along its length. At least at the front two panel segments.

[Blakbird]

There are a dozen cranes working outside of my building right now, and I've spent a lot of time watching them. Real crane booms bend under load too, sometimes quite a lot, so I'd say your boom is behaving in a scale fashion.

[aol000xw]

There are a dozen cranes working outside of my building right now, and I've spent a lot of time watching them. Real crane booms bend under load too, sometimes quite a lot, so I'd say your boom is behaving in a scale fashion.

That is Interesting and after researching a bit ... I conclude than my cranes are quite faithful and behave like real ones

Seriously, this was unexpected, it flexes like a fishing pole....

[efferman]

If you take a closer look at the second picture you will see that it bends to the side. There is something wrong with this crane.

Blackbird, yes bending over the full length is ok, bu not only at one connection.

[aol000xw]

Yeah and the load looks unbalanced, it simply was the most extreme example of a yet in one piece mobile crane I found.

I I did not know that most cranes at full extension even with no load have some noticeable deflection to them even at mild angles.

[Blakbird]

That second picture looks like optical aberration from a fisheye lens. I don't think the boom is really bent. In the first picture the boom main section crippled! That's not good.

In any case, beam deflection under load is a guarantee. If you look at any of the data sheets from real cranes, you will see a footnote explaining that the lengths and positions shown in the table are not quite right because they ignore deflection.

Efferman is right that the deflection should come from strain and not from poor fit between boom sections.

[jantjeuh]

Boom bending is pretty common, though to the side is clearly a problem.

[Erik Leppen]

The boom bends because the bottom is compressed and the top is stretched. So if you awnt to minimize the bending, try to minimize the amount that the bottom will compress, and the amount that the top will stretch. If the bottom and top are further apart, the same amount of stretch/compression will result in less bending.

So, strengthen the bottom and the top, and keep them at the right distance by vertical bracing of any kind. It doesn't have much use to strengthen the center, as long as the center is there as a spacer for the bottom and the top.

By the way - that's also why real crane booms are half-oval shaped - with a round bottom and a flat top. A rounded surface has a better resistance against compression then a straight surface, so that's why it'sround at the bottom, and for tension it doesn't matter, so as much material as possible is put at the top, hence the flat top.

Edit: also, a lot of the bending comes from the weight. If you can make your boom lighter, it will bend less already. Maybe you could start designing the last (innermost) section and try to make it really lightweight. Then, design the pre-last section, make sure the last section fits tight in it and keep the combination as light as possible. Using that, work your way to the main section.

Edited September 26, 2014 by Erik Leppen

[dr_spock]

Is a lattice boom stronger than a telescopic boom?

I am building a long spaceship for SHIPtember using technic panels and I get some bending when I tried to swoosh it. Probably better in space where there is less gravity.

[Erik Leppen]

Is a lattice boom stronger than a telescopic boom?

Probably not - but it can be much lighter :)

[JDC]

How about these wings as a solution?

[Blakbird]

Is a lattice boom stronger than a telescopic boom?

They are different, but neither is inherently stronger.

A telescopic boom is a lever. The hydraulic actuator is the fulcrum, and the counterweight balances the load. This results in a beam in bending, and the bending moment is highest nearest the fulcrum (which is why the boom is the thickest there).

A lattice boom is pinned so it is not a lever and it is not in bending. A lattice boom is only in pure compression. The moments are carried by the boom support cables. This makes it possible to operate a lattice boom at a lower angle without worrying about it bending.

Of course, both of the above descriptions refer to a crane under load. Any boom has to at least support its own distributed weight, so a LEGO lattice boom will sag in the middle like a pinned-pinned beam. Make it as light as possible.

How about these wings as a solution?

That's a "Mega Wing Lift". I'm hoping we can add that to the Grove crane some day! Helps support lateral loading at extreme lengths.

[Bricktrain]

The easiest solution would probably be to limit the extension by 2-3 studs to allow T1 to remain further into the main boom.

I had a struggle to get my boom and actuator strong enough but it has become quite a bit larger so not as much of a problem now. http://www.brickshelf.com/gallery/bricktrain/construction/2011/ATC/p8150109.jpg

Another help is to put the gear rack and drive to the underside of the boom rather than on the top.

[DanFraser]

some of you have maybe seen my video with the

of the xl actuator and how the boom is bending under the load. here are two pictures

do you have any ideas to prevent this.

You need beams with the holes placed vertically on the top. Start off with one (or two for symmetry) across the top from the grey frame piece to the yellow pieces on top of the black double pin with hole connector between the curved frames. This will need to be reinforced further back, maybe all the way down.