Hydraulic rock splitter

[blakester]

So I have a bank or rock I need to split off. I'm not in a hurry to do it and have been looking into ways to do it myself. I have a newer 70lb 1m length rock drill to put some holes in the rock, and I'm wondering about fracturing. There is the Dexpan expanding grout option, but I figure with my requirements I'll need to spend about 1000$ to get the volume I need. It's granite so it's tough rock, and the top foot or so has already been peeled off by a big machine. I have a small 7000lb mini excavator with thumb plumbed, running about 3000 ish psi, and an older 8 inch stroke and 5 inch bore hydraulic cylinder. I was tossing the idea around of fabricating a rock splitter but I'm not sure how to calculate the amount of fracture force I can achieve. 2 inch rod in the cylinder. Is this even worth attempting, it seems to buy just the normal purpose built splitter I'd be looking at 5k or more, so not worth it over the Dexpan. Anyone have any thoughts on this? Cheers,

 

[iointerrupt]

So I'm basically in the same boat, got acres of granite boulders to split up. Lately I've been using Dexpan, and I'd recommend giving it a try before anything else. For $100 you can see how it works and see what you think of it. I was resistant to it at first, given the cost, but it's so stupidly easy I'm starting to think it's easily worth it for the casual rock splitter.

But, back to the topic. In my research, the only hydraulic rocker splitters out there are the German-made DARDA's, and lots of various Chinese clones of the DARDA. I have no idea if the Chinese ones are even available outside of China. The DARDA seems to start at $10k and up. The Chinese ones are maybe $2k.

As for the splitting force, DARDA units run off of 7100 PSI power packs. Digging around, I've found numbers that say the cylinders on them are in the 3.25 to 4.25" range (depending on model). Looking at the pictures, this looks about right too.

So, breaking out the hydraulic calculator, a 4" cylinder @ 7100 PSI, generates 90,000lbs of push. At 3000psi, the equivalent is a 6" cylinder. Alternatively, you could buy a separate 10,000psi power pack and drop back down to a 3.25" cylinder.

Now then, that's just the raw push force. The actual splitting force comes from the wedges, which magnifies that greatly. The DARDA models talk about splitting forces in the 1-2 million pound range. So the design of the wedges and counter-wedges is probably critical. Both to generate that much force, and then to withstand it without bending.

Best I can tell, the wedges are really tricky to design and make. You have a hard limit of them needing to fit in a 1.5-2" hole. So you can't just add more material to make them stronger. Which means material selection becomes really really important, probably need something crazy strong: 1144, 4140, maybe E52100?

Anyhow, as you can probably guess, I started designing & building a hydraulic rock splitter a few months ago. I got a couple parts of it done, but have been stalled out on the wedge design. If you still think you want to give it a try, I can upload all my research files I dug up from around the internet.

But for now though, I'm happily paying the Dexpan price.

 

[Egon]

Consider feathers & wedges?

Be brave; powder?

 

[TemporaryKubotaOwnerMark]

Get a quote to have it done for you, before you go trying to home-engineer a $25,000 rig.

$1000 of grout is looking pretty cheap.

 

[Code54]

Could you just rent a hammer to attach to your mini - chip it away.
No Hr meter on a hammer so if it is like around here you rent on Friday evening it does not go back until Monday morning - thats a lot of hammer time.....
Good luck

 

[Winmac]

Currently helping a buddy break up some granite boulders at his place, first started out with Eco bust( complete fail), then 1-1/4 inch holes and home made wedges with cole chisels and now we are doing 7/8 holes with proper fethers and wedges.

Rather than spending a grand on Eco bust I'd spend it on proper fethers and wedges.

 

[KyleH]

What about using NX Burst or similar product? It only requires a short training course here, no blasting license.

Nxburst™ Cartridges - Coogar Sales and Services

 

[blakester]

Yeah feathers and wedges are an option, but I have lots to do so I'm not sure about.time, and it's a rough face, like taking a step shape off the side of a hill. Iointterupt I'd love to see what you dug up for designs along the way. I'm sure there has got to be a serious piece of engineering in those hydraulic splitters I'm missing for them to cost 5k for a used one minus the power pack. It could be for longevity, but I'm not sure. Seems expensive for what appears on the surface to be a simple design. In any case I'll keep dreaming about the design while I try out the grout.

 

[iointerrupt]

Attached is a zip file of all the detailed drawings I could find. Also some pictures of the chinese clone splitter where they changed the retaining system for the counter wedges (appears greatly simplified).

I also have copies of the manual for the Darda splitter, not sure if they are too big too upload though. Not terribly much interesting in them from a design point of view though.

 

[PILOON]

My neighbor once split 2 sized boulders under his house using the plug and feather method.
He even drilled the holes by hand with a star drill and 3" sledge, could hear him 'tap-tap' for ever.
What patience! but he did it.

I once split dozens of yard sized boulders under my house using a pneumatic rock drill and a tapered 'plug'.*
We'd drill a standard blasting hole, change for a hammer and tapered bit and usually 3 holes would split anything.
These were granite, about as hard as you get. Once split we'd sled them out with smaller pieces loaded in a wheelbarrow and made a retaining wall with the pieces.

*the rig was a 250 CFM compressor with 2 hoses so one would drill while the other would split. Dynamite was not an option nor a backhoe as access was a problem being on a mountainside.