[MOC] 5 axle mobile crane - finished 02/2019

[Ivan_M]

..make son, plant a tree, build a lego mobile crane...

Here is my new project - 5 axle mobile crane using 62,2mm wheels. I have not build any of the famous cranes like 42009, its ultimate version, Groove, etc., the only crane I have ever build is the fabulous 5-axle crane by @Erik Leppen so I delve into very unfamiliar waters. The reference machine is Liebherr LTM 1250-5.1.  So far I have decided to implement these features:

- 4 axles steered (servo), single steering mode, various angles, ackerman

- 1 axle driven by L/XL motor, fake V6 engine

- pneumatic outridges, extended by string (M-motor) - this is the feature I want most, I would like them to lift the whole crane from ground, pneumatics operated by autovalve (M motor)

-  4 section boom using system panels, each ~60-70 studs long, extended by string (M or L motor)

- custom LA to lift the boom to correct angle - string operated (M or L motor)

- slewing via motor

- winch via motor

- proportions matching with real machine

So far I have lad the bottom layer of carrier and tested the autovalve and outridges extension mechanism. I really like how the outridges work, it is technic beam with plate on bottom and tile from side. It fits perfectly into small panels (2 bricks high) - one newer type with support from one side and old type without support from other side. There is enough space for string and shouldn't bend. The only question is where do I put the pneumatic tubbing and if I will retract cylinders by 2nd set of tubbing or use rubber bands. Some kind of winch for the tubbing would be nice, but there is no space.

Since the outridges are totally blocking any holes for axles from front to back I had to guide steering axles under it (yellow) and drive axle over it (red). It means that the racks are mounted upside down but it works very well.

WIP - 5 axle crane - overal view

WIP - 5 axle crane - outridges

WIP - 5 axle crane - autovalve

WIP - 5 axle crane - bottom view

What I'm struggling now is where to put battery for undercarrige. I also have to add drive motor and rear outridges, then make it sturdy, it is now without any bracing.

Edited February 11, 2019 by Ivan_M
headline

[M_longer]

Judging by spacing between point where wheel turn and steering link connects to the rack, it goes sideways when chassis turns, right? And you are using axle connectors, which will disconnect very quickly with greater load applied.

[Ivan_M]

13 minutes ago, M_longer said:

Judging by spacing between point where wheel turn and steering link connects to the rack, it goes sideways when chassis turns, right? And you are using axle connectors, which will disconnect very quickly with greater load applied.

Hmm, I didn't noticed but I have rolled it only few times on table and seemed fine to me. It is true that the steering angle is the same for axle 1&5 and 2&4 while it should differ slightly, but I didn't want to reduce it by gears as it makes offset. And regarding the steering arms - yes they are not locked, I guess I can try to make them different. I have used the same setup on my previous motorized truck and it was running fine, but this will be heavier model so it is worth checking.

[suffocation]

Great start to an ambitious project. I'm especially interested in the four-section boom, since I've been toying with one for a few days but haven't come up with anything that works even half-decently

[M_longer]

5 hours ago, Ivan_M said:

Hmm, I didn't noticed but I have rolled it only few times on table and seemed fine to me. It is true that the steering angle is the same for axle 1&5 and 2&4 while it should differ slightly, but I didn't want to reduce it by gears as it makes offset. And regarding the steering arms - yes they are not locked, I guess I can try to make them different. I have used the same setup on my previous motorized truck and it was running fine, but this will be heavier model so it is worth checking.

Could you post picture of chassis without wheels?

[Ivan_M]

21 minutes ago, suffocation said:

Great start to an ambitious project. I'm especially interested in the four-section boom, since I've been toying with one for a few days but haven't come up with anything that works even half-decently

Thank you, it will be made out of system bricks (panels and brackets), only the 4th section will be from technic bricks and first section will be from technic panels. Whole boom will be 6 studs wide and 7 studs high.

7 minutes ago, M_longer said:

Could you post picture of chassis without wheels?

Here you go:

20180921_200823

[Saberwing40k]

I'd put the battery box at the very rear of the chassis, where a lot of cranes have a toolbox. Or, you could put a AAA box to one side of the engine. Or, the box could go under the front cab.

[Erik Leppen]

Now this is interesting.  I'm normally not a fan of solutions incorporating many motors, but yes, it will surely be a challenging 3D puzzle to find out where to put things. At the least, it makes me think: gee, I should redo my latest crane (which I never finished) 

One thing that's interesting is how you made it 2 studs narrower than what I would expect given these wheels. It's probably a more realistic proportion, but gives you a lot less room to do things. I really like your steering solution with the ball-joint parts, which is kind of similar to how I tried it, and includes the same Ackermann geometry as a bonus. And yes, identical angles on axles 2 and 4 is only logical; the difference would be very small in reality anyway. And yes, the front outriggers being in the way for the steering and drive axles is very well-known, at least, to me 

Are the wheels touching the outriggers when steering? They come quite close, but the turning point is inside the wheel so you might be good. If they aren't touching, then you have found a really nice compact solution! The way the pneumatic cylinders are mounted is currently quite weak, but I hope you find something for that. The string-based solution seems pretty ingenious. Why did you go for string?

As for the battery. Only option I can think of right now is, what if you would place the V6 engine off-center, and put the battery next to it? Would that fit?

Anyway, great start and I will be following this 

[Ivan_M]

29 minutes ago, Erik Leppen said:

Now this is interesting.  I'm normally not a fan of solutions incorporating many motors, but yes, it will surely be a challenging 3D puzzle to find out where to put things. At the least, it makes me think: gee, I should redo my latest crane (which I never finished) 

One thing that's interesting is how you made it 2 studs narrower than what I would expect given these wheels. It's probably a more realistic proportion, but gives you a lot less room to do things. I really like your steering solution with the ball-joint parts, which is kind of similar to how I tried it, and includes the same Ackermann geometry as a bonus. And yes, identical angles on axles 2 and 4 is only logical; the difference would be very small in reality anyway. And yes, the front outriggers being in the way for the steering and drive axles is very well-known, at least, to me 

Are the wheels touching the outriggers when steering? They come quite close, but the turning point is inside the wheel so you might be good. If they aren't touching, then you have found a really nice compact solution! The way the pneumatic cylinders are mounted is currently quite weak, but I hope you find something for that. The string-based solution seems pretty ingenious. Why did you go for string?

As for the battery. Only option I can think of right now is, what if you would place the V6 engine off-center, and put the battery next to it? Would that fit?

Anyway, great start and I will be following this 

Thank you. Overal width will be 17 studs, I don't think it is different from cranes using 62mm wheels, is it? Anyway it is given by scale (1:22, overal width 3000mm =>17 studs). Wheels do not touch anything, it is indeed tight fit and pivot point inside the wheel is the key. The outridges are enclosed in something like tunnel made out of panels, I think a picture is better than words:

The technic brick slides between two panels, it is tight fit and it cannot move to other direction. There is however no space for any rack because it is enclosed from top so the only way to push it to and fro is using string. I have made it that way to keep the width 2 studs.

I think I will place battery behind 5th axle, just before outridges. Maybe it will be necessary to use AAA box

Edited September 21, 2018 by Ivan_M

[M_longer]

2 hours ago, Ivan_M said:

Here you go:

Aha, It seems  that you will have to rebuld it, because most of those links are made on 2L axles, and they will be pulled out under weight of the model and force from the servo. You have two options, personally I'd go for a standard solution with 13L racks and different length of each steering arm, used in 42009:

Second option is staying with 7L rack and trying to achive ackerman steering, but that will be alittle bit more complicated.
Those steering rack can't work at angle, they must slide perpendicularly to the frame.

[Ivan_M]

12 minutes ago, M_longer said:

...

Yes, I know it is a week spot, I would kill for 4L perpendicular connector, 9L and 11L rack.. I will rather sacrifice RC drive tho than switch to steering without ackerman and pivot point inside the wheel, I value those two features very much.

[JonathanM]

11 hours ago, Ivan_M said:

I would kill for 4L perpendicular connector

Not quite what you need, but a possibility I guess.

https://www.bricklink.com/v2/catalog/catalogitem.page?P=98989

[Ivan_M]

On 9/22/2018 at 10:11 AM, JonathanM said:

Not quite what you need, but a possibility I guess.

https://www.bricklink.com/v2/catalog/catalogitem.page?P=98989

That double end makes it useless unfortunatelly

So I think I have position of all function-wise parts in place, I had to use small BB tho:

20180923_131935

That red axle from 16T gear will go to rear to extend rear outridges. After that I have disassembled almost the whole thing and started with better bracing. There is a nice spot at rear for 2 IR receivers, That way I will only need two PF extension cables. I think the overal height is 1 stud higher than what would be possible but it is still fine I think.

So now I need to brace it properly and then test all functions before I move to superstucture.

[Ivan_M]

Here is test drive with 2kg load, it is quite fun to drive with such a tight turning radius. The steering arms are perfectly fine, no disconnects at all. I don't suppose superstucture will be over 2-2,5 kg.

 

[pagicence]

What's happening with the rear steering there? It seems to me that when you get out of the corner and try to go straight the rear wheels get stuck a little bit in the turn position. They don't return to center as good as the front wheels do.

[Ivan_M]

2 minutes ago, pagicence said:

What's happening with the rear steering there? It seems to me that when you get out of the corner and try to go straight the rear wheels get stuck a little bit in the turn position. They don't return to center as good as the front wheels do.

true, there are two pairs of 16T gears on the way back and this is caused by slack they have. I don't think I can improve it

[pagicence]

In the video I saw that you put servo motor on one end. Have you thought about somehow incorporating it in the middle? Maybe that will help a little.

[Ivan_M]

Just now, pagicence said:

In the video I saw that you put servo motor on one end. Have you thought about somehow incorporating it in the middle? Maybe that will help a little.

not really, there will be always differential in way that you have to pass somehow. U-joints would be better at that but I don't have space for them. 20T + 12T bewels might have less slack, I can try them.

[Erik Leppen]

The stering problem is probably not caused by slack in the gears - the play in the gears is actually very little - but by the twisting of the long axles all the way back and by the friction inherent to steering. So I expect putting the steering motor in the middle will definitely help.

I don't find it that much of a problem, but I think it it bothers you then you could try it and see whether it makes any difference.

[Ivan_M]

10 hours ago, Erik Leppen said:

The stering problem is probably not caused by slack in the gears - the play in the gears is actually very little - but by the twisting of the long axles all the way back and by the friction inherent to steering. So I expect putting the steering motor in the middle will definitely help.

I don't find it that much of a problem, but I think it it bothers you then you could try it and see whether it makes any difference.

I guess axle twist is there as well, but not as much as play between two pairs of 16T gears. It is easy to try it, when I lift it and steer by hand it is clearly seen. 12T+20T bewels are much better with slack so I will swap them.

[Ivan_M]

I have some progress - the chasis was stripped down to brace it properly. In between the process I have realized that the outridges extension through string would be nightmare to synchronize so I was looking for another solution. After few tries I have found very nice solution using 2x3 old stype panels without support and gear rack from Arocs. Extension is then by 8T gear and works very smoothly yet it can support the weight without problem. The rack housing from arocks is useless in my case as it would be too long (19 studs).

I also started with some bodywork:

I have not started with superstructure yet but I have final design of boom and lifting cylinder. I'm waiting for parts tho, I hope they will arrive soon to show you more progress.

[1gor]

Looks interesting 

[AFOLegofan66]

This looks great...looking forward to the finished product!!

[Erik Leppen]

Some really nice progress! The best thing is how you managed to fit everything in. The new outriggers look very nice, I'm actually surprised it fits this way.

Also, the outrigger comes really close to the front wheel. Nothing hits each other when steering?

The bodywork is also nice, good useage of the dark-gray small panels from the Mack. Great so far, looking forward to more :)

[Ivan_M]

3 hours ago, Erik Leppen said:

Some really nice progress! The best thing is how you managed to fit everything in. The new outriggers look very nice, I'm actually surprised it fits this way.

Also, the outrigger comes really close to the front wheel. Nothing hits each other when steering?

The bodywork is also nice, good useage of the dark-gray small panels from the Mack. Great so far, looking forward to more :)

Thank you! Outridges are indeed very close to wheels but they do not touch them, I consider that as a major flaw so I take good care about that. The rack from arocs also fit into 2 brick high panel, but it is perhaps too tight and doesn't move smooth enough to use 4 of them hooked on single motor. I'm really happy how the bracing went out. It is impossible to take pictures of it, you have to feel it, it is very robus. I'm sometimes lazy to disassamble some complex builds, but this time I really took care to make every part as best as I can.