Lifting boom for an excavator

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>>1081659
The lifting capacities for the excavator (Åkerman H12B) can be seen in the table.

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>>1081659
>>1081660
I plotted the lifting capacities of the machine. In the image the blue line is from the table, up to 9m and the thinner is extrapolated from that data. The red line is the calculated max weight that will (might?) tip the machine.
Now I'd like to have the boom to withstand the tipping weight to that it wont break, and I will feel it when it gets light on the back when the max reach will be close. Rather that than having the boom breaking.
So I'd like to know if someone has mad calculation skills to figure out the tube size(s) and the material thickness.
As stated earlier 200*400mm is in my mind at the moment with thickness around 8mm but is this overkill or ridiculously flimsy?
Also input of supports in the end of the machine would be nicer than nice. So that I can reinforce it to be as strong as possible with minimum weight. I'm considering adding a fin to the top side of the first boom to strengthen it but I don't know if it has any real significance.
As the load will inevitably swing a bit it needs to be strong enough sideways also to that it wont bend, but the main force will be predictable...

Any input or ideas?

>>1081659
It doesn't matter how well you build the extension, it'll never be able to lift your mom

>>1081665
haHA! 4chan, for the whole family to enjoy!

Seems like there are no structural engineers hanging around...

>>1081659
>It needs still to be safe.

It's not gonna be safe

divide the weight you wanna lift (including beam) by 27, that should give you an approximate cross section in mm^2 you need for your beam.

I'd use thinner steel and weld myself a space frame around the tube, but I don't know how talented you are.

>>1082431
I will have a friend who is a welder, and dawn good one, to do the welds. This is nothing that I can do, or actually let me correct that, something I'd trust myself doing.

So just to clarify, if I'd like to lift 2000kg I'd just divide by 27 which is approximately 74. And this number is what now? Cross section was mentioned but I can't place this 74mm^2 so that it would become a thickness/size. Could you elaborate?

Any tips on a space frame that would be efficient, in material, labour as well as weight? Maybe start with heavier material and have the last extension as some kind of truss-like structure.

>>1082470

Just pay an engineer a few bucks before you kill yourself you idiot

>>1082474
Because dying sucks ...

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Ballpark figures say your safety factor is less than two assuming S235 steel and your beam end is displaced 36 mm vertically. That's assuming the beam is a single continuous piece of steel, no sliding joints no nothing. I wouldn't say this looks safe.

>>1081659

Have you considered making it out of a shipping container. 40 ft boom on your megga ex.

>>1083032
Yes, this is known. It isn't safe. The idea is to lift heavier loads with a shorter boom, and use the long boom to lift lighter loads. The pic in
>>1081663
is a bit false as the excavators boom is some serious shit. I don't know how heavy it is but it is heavy and the boom will be significantly lighter and therefore the extrapolated curve isn't probably linear. But how non-linear it is going to be I can't tell as this is going to be a surprisingly interesting problem if one wants to do this as light and easy as possible. I might go for overbuilding but haven't decided yet.
Anyway, I'd love to have a long boom for light stuff as I'm going to need it, I know it. But if the curve is true then I get 0kg lift @ approx 13m, which means a 4metre boom but that has to be bullshit as the bucket lifts easily a 1m^3 of stone plus the (400kg) bucket! So the boom weight is calculated in there somehow but this is getting over my head, I'm a geneticist for crying out loud!

>>1083262
That would be so cool except for the factor that >>1081663
gives a slightly disappointing lifting capacity with the 12m boom :(. A 40 weighs 4 ton.
Otherwise I'd so go for it!

I suggest asking on welding forums because people there are fucking ninjas at building, modding and repairing excavator parts. You will get insights you won't get here.

>>1083527
Yeah, this might be true. Or excavator forums.

>>1083920
>Or excavator forums

Heavy equipment forums exist. Welding forums are full of people who repair what breaks, fab custom booms and parts, and are the perfect bridge between an engineer (some are) and a good DIY welder.

You had better be a good welder to fab your own boom.

Seriously, get on Weldingweb or the Miller forums or migwelding.uk if Eurofag. I didn't suggest them by accident.

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>>1084001
I think I'll ask around the excavator forums. My machine is an Åkerman and there is one that has an active community around those. They are called Volvos these days.
And then check out the welding forums.
At the moment I'm curious about the math around this. I was out at sea yesterday and my boss boat has a hydraulic lifter. It lifts 370kg at around 2,5m and the boom extension is seriously flimsy. I'm probably going for the same kind of lifting capacity at the outermost point of the extension so I can take some measurements from there. One problem seems to be that these kind of booms aren't square, they have a housey look like pic related that does indeed reinforce them.

>>1084213
It got flipd!

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Now I was shopping for a 24V wind shield wiper motor and mentioned my project to the guys that were running the heavy equipment repair shop I visited. They said they have an extending boom of a crane lying around. One of the hydraulic rams is borken because some sucker drove it under a too low bridge. It is too long anyway for my use with four extensions so the first could be ditched, or even better, I could remount the other hydraulics so that I'd have a three part hydraulic extension and the option to use a manual last one. 500€ asking price, and the haggling starts from there.