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500A boom
- Thread starter TVA
- Start date
crane operator
Senior Member
There won't be any mechanical lock or such. The way some of the two cylinder boom sections work is that you simply provide hydraulic pressure to the tele system, and the section with the least resistance or largest piston will move first. With no load on, they will typically just go together.
Grove has some rigs with a roller that falls into a notch to activate the upper cylinder , but I don't think that national will have that. You would see it externally.
You just don't have it unbolted right. It shouldn't take that kind of pull to disassemble it. I'm not sure what you're trying to pull apart in your pictures, and what you have loose.
They will have holding valves in the cylinders, so even with the lines off, the extend side of the cylinder will be hydraulic locked (if the seals are still good). You have to pull the holding valve to remove the rod from the barrel.
The boom will just slide apart if you are going about it the right way. You still have something holding you up. Don't weld to the boom structure.
Grove has some rigs with a roller that falls into a notch to activate the upper cylinder , but I don't think that national will have that. You would see it externally.
You just don't have it unbolted right. It shouldn't take that kind of pull to disassemble it. I'm not sure what you're trying to pull apart in your pictures, and what you have loose.
They will have holding valves in the cylinders, so even with the lines off, the extend side of the cylinder will be hydraulic locked (if the seals are still good). You have to pull the holding valve to remove the rod from the barrel.
The boom will just slide apart if you are going about it the right way. You still have something holding you up. Don't weld to the boom structure.
crane operator
Senior Member
It shouldn't come apart any harder than the other sections came out of the base section.
The top cylinder is the one that moves the front section inside of the middle one.
As you can see it is loose and out of its mounting pockets - so it is not holding anything!
The bottom cylinder is the one that moves middle section inside the rear one - as far as I see I need to remove top cylinder and lift the bottom cylinder out of its retaining pockets.
But I can’t move front section inside the middle one at all, to get to top cylinders rod eye pin.
As you can see it is loose and out of its mounting pockets - so it is not holding anything!
The bottom cylinder is the one that moves middle section inside the rear one - as far as I see I need to remove top cylinder and lift the bottom cylinder out of its retaining pockets.
But I can’t move front section inside the middle one at all, to get to top cylinders rod eye pin.
I didn’t unbolt the slider pads because I don’t think I have to.
The only thing I removed is steel strip that bolts on inside of outer section at the very front of it. It is between the top of inner section and the “ceiling” of the outer section.
I think it is safety lock, in case cylinder comes loose or apart, so the boom will not come apart.
The only thing I removed is steel strip that bolts on inside of outer section at the very front of it. It is between the top of inner section and the “ceiling” of the outer section.
I think it is safety lock, in case cylinder comes loose or apart, so the boom will not come apart.
Well. There might be a mechanical lock!
There’s only one hole in that middle section, looks like it wasn’t cut at the factory. It is about 1”x3”
I looked in there yesterday when front section was almost all the way at the front end of the middle section, but wasn’t coming out.
And under all that oily crap I saw something like D ring, right at the back and on the bottom of the front section.
I will be back there Friday, I think I will clean everything really good and try to take a peak in there to figure it out!!!
There’s only one hole in that middle section, looks like it wasn’t cut at the factory. It is about 1”x3”
I looked in there yesterday when front section was almost all the way at the front end of the middle section, but wasn’t coming out.
And under all that oily crap I saw something like D ring, right at the back and on the bottom of the front section.
I will be back there Friday, I think I will clean everything really good and try to take a peak in there to figure it out!!!
There is two mechanical locks. It is mechanically sequential by design.The problem was that boom was so packet with dirt and goo that those locks didn’t pop out to be visible.
One lock does not let front section to be extended inside the middle section until middle section will come to the end of rear or base section.
The other lock keeps the middle section from retracting inside the rear/base section until front section is fully retracted inside middle section.
I think it is done to insure highest load rating possible when front section doesn’t need to be extended.
I don’t know how to select videos from
my phone to post here. I shot the videos how those locks work.
Last edited:
crane operator
Senior Member
Thanks for posting up the pictures, glad you got it apart, and I'm sorry for steering you wrong that there wouldn't be mechanical locks. I've never done one of the smaller ones. Somebody has to be the guinea pig.
Don’t worry about it - no one knows everything!!!
Just share it so the next guy can find it.
Both cylinders are leaking from the rod seals, and jump hoses coming apart.
Glad I showed up on time today!
Customers workers was about rip that boom apart!!!
They found bigger and stronger chains!!!
Now need to get flapper wheel and smooth out all the damages done by chains and vibrating plate, so the sharp edges will not eat away plastic slider pads!
Customers workers was about rip that boom apart!!!
They found bigger and stronger chains!!!
Now need to get flapper wheel and smooth out all the damages done by chains and vibrating plate, so the sharp edges will not eat away plastic slider pads!
crane operator
Senior Member
So they just drop in and out when you have the boom in the right place?
Yes, there’s two pushers that bolts to the side of the base section that push on those locks, when the middle section gets to the outmost extended position.
I thought those were just a some kind of a side to side sliders.
But when the locs popped out of that caked up grease - it became all apparent what those were.
I’ll post the pictures of them next time I’ll be there.