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The rock and ice mechanics lab at Lamont-Doherty is led by PIs Heather Savage, Christine McCarthy and Ben Holtzman. We are in the process of growing our lab and building our experimental program. Along with a team of postdocs, undergrads, grads, and longtime staff engineer Ted, we are rehabilitating and revamping some of the old equipment and building new rigs for exciting new experiments on both rock and ice. You can follow along with our progress here.

Thursday, 24 September 2015

A dry run

Before we start getting crazy with ice and cold, we want to have a dry run of the apparatus. Can we actually control it the way we want? We loaded everything up in the cryostat, but left it at room temperature with the front panel off and, instead of ice, we placed a piece of PVC plastic as our central slider.

We used some makeshift plastic pistons so as not to potentially harm our expensive ceramic ones.
We manually dialed in our horizontal piston until we got a decent normal load (the panels that say 0.167 and 0.160 are in MPa and are the right and left load cells, respectively).
Then we slowly drove the plastic down through the rock. Plastic is pretty slippery, so we didn't get to very high shear stresses, which made me very happy for a first run. It all worked in a nice controlled manner, with data sent to a computer for later analysis.  No major glitches, so next step: ICE!!




Saturday, 19 September 2015

A little nip and tuck

Now that the rig has been placed in its permanent position and the unistrut table has been bolted down to the concrete pier, it's time to address the elephant in the room. Let's talk about that rat's nest of wires.
Yeah I'm talking about you.
First thing we did was to systematically tackle each wire and cut it to the length it needed to be.
Then all the gray component wires (those going to the LVDTs and Load Cells) were tucked into this plastic housing and attached to the back edge of the lower plate. (That the channel housing is the same thickness as the plate was rather satisfying).
Then the wires coming out were wrapped in fancy black plastic. We are talking next level organization here.
Isn't this the tidiest thing you've ever seen?
No need to stop there. The chiller hoses needed to also make a clean profile. 
They carry a methanol/water mixture from the programmable chiller in the next room to the cryostat.
Looking good!





Saturday, 12 September 2015

Final adjustments

So we started doing some calibrations in the apparatus and realized we would like it just a bit stiffer. We decided to put another steel plate, this time to reinforce the bottom plate. But we couldn't just slide it in. The horizontal hydraulic piston and the cryostat dimensions were all designed around the current space between top and bottom. Instead we had to lower the bottom piston the same amount as the new the steel's thickness and then slide in the plate. This required us to lift up the whole rig from the top. A mobile hydraulic crane did the trick. 
While we were at it, we reconstructed the unistrut table that the rig sits on. We not only shortened it to account for the rig adjustment, we also repositioned the legs so that they were symmetric. Much prettier. 

Here Mike tightens down the steel plate with an allen. He also built the housing for a lower LVDT (the rounded square on posts beneath the rig) that will measure the position of the sample as it slides.
A spring loaded LVDT will come up through a hole in the plates and cryostat. A ceramic extender piece sits right on top of the spring loaded core and will actually be in contact with the ice.  
At the risk of repeating myself…we're almost there.