Is there anyone on this forum that does heavy rock trenching in limestone or granite.
Welcome to the Forums! Glad to have you. We've done a fair amount of trench rock laying storm drain in the limestone and sandstone we have here in Central AL. Whatcha wanting to know?
I'm located in central Kentucky and we are a utility contractor trying to trench rock instead of blasting or hammering. I'm looking for suggestions on the best tooth size and tooth pattern to use in hard limestone
What size trench are you digging? It sounds like you already own a machine? How heavy is it? Most bigger trenchers have carbide bits in a chevron pattern, cause that’s what works best for rock. Bit size depends on machine. Machines 70,000 pounds and bigger are usually 1-1/2” step shank bits, smaller machines are usually 1” bits.
We run a T13 Trencor machine. It weighs +-170,000 lbs. We run a chevron pattern on the chain. We are new to rock trenching and I'm hoping to learn from you guys with experience to shorten the learning curve. We are in really hard and solid limestone in this area and I'm trying to figure out the best brand and size of carbide tip to run in our conditions.
Sandvik, Betek, and Kennametal make decent bits, and they all have lots of options. I don’t know which would be best for you. You could check with these manufacturers and see what they recommend for your conditions. I currently use Kennametal TS19X. They’re held in by 2 snap rings, and I check the snap rings every day. Otherwise I lose bits. If I’m in granite-like rock, the carbides can break out of the end of the bit. That’s most likely cause I have a hydrostatic machine and it’s always running at full speed. You have a mechanical drive chain. If you’re in hard rock, running your chain in a low gear will greatly increase the life of your bits. Weight on the boom helps with digging rock. Some bigger trenchers are set up to add shot to the boom for weight. Pretty much everything on the front of the machine is a wear item. Chainsaw trenchers cost a fortune to run, especially in rock. You got pictures of your machine?
I attached a couple of pictures of the trench. We are cutting 3' wide x 7' deep for gravity sewer. I contacted the regional Vermeer sales representative and we are going to send a few samples of the rock to their lab to determine the UCS. From there they will give recommendations on specific size and types of teeth for this specific rock. I will let you know how it works!
Too bad you didn't have something like the Henuset Polarbear trencher. There's a fairly recent video discussing Henuset and the custom machines they built. A former employee said the Polarbear could dig 23ft/minute in perma-frost up to 10' deep. When it was built it wouldn't fit out the door so they trenched through the concrete. There was a pic. that confirmed this. They said it wasn't an accident and Art Henuset was no dummy. He had planned to trench through the floor as a means to test it before putting it to work but never told anybody. It was too heavy for some jobs and hot and noisy to run. It was originally powered by a Big Cat engine but they needed that engine for something else so replaced it with a quad turbo 16V-149 Detroit. They got the engine running briefly last year after it sat for years. It needs a torque converter and then they can hook the trencher wheel back up. Apparently it weighs about 168 tons!
That's a big lump of steel.
It is. It has stretched D9 undercarriage with special wide pads. They built it in 4 weeks in 1972. A Hopto 1900 hoe on a custom elevated pipe mount support with the tracks 35' wide to straddle the spoil pile followed it. There's pics. but unfortunately there doesn't appear to be any video of it operating which is a shame. Henuset also built 2 HD41 pipelayers that were the largest built at the time. Might still be.