As promised, here is a description of the tap density apparatus. Below is a Sketchup of the final rendition of the apparatus. It uses two optical posts and post holders from Thorlabs as the piston and guide respectively. The two posts are fixed together by a baseplate spacer. The baseplate is screwed into the post holders using the post holder’s thumb screws. I removed the inner tightening screw of the thumbscrew to allow for better ventilation of air when the column is tapped. The graduated column is held onto the post holder with a few hose clamps. The hose clamps are then connected to each other using PCB spacers.
Below is a complete bill of materials.
- TR4—Ø1/2″ x 4″ Optical Posts (x2)
- PH2—2″ Optical Post Holder
- PH4—4″ Optical Post Holder
- MB4—4″ x 6″ Breadboard
- Worm drive hose clamps.
- Graduated cylinder.
Personally, I wouldn’t use Fisher brand glassware as I’m typically rough with glass and Fisher products have a difficult time standing up to my abuse. Below are pictures of the setup.
The above picture shows the actual setup. The system is clamped down to the table using a C-clamp to enhance stability. Behind the cylinder in the background is a plastic square holding up a white sheet of paper. This is used to create a shadow of the cylinder as seen below. The shadow is generated by using the light source from a surplus-ed carousel slide projector which, I found out just now that you can still purchase on Amazon. Neat!
This shadow is imaged by a camera directly behind the screen.
The camera being used is a Logitech C910 camera. We are using GTK+ UVC Viewer—also known as guvcview—as the software to capture images. Unfortunately there have been problems in obtaining images and we have yet to determine a unified collection mechanism. But, guvcview is open source and is filling the bill for the moment.
I have been sorely wanting an optical table to conduct these experiments on. Especially since there is no means for us to keep things in one place other than to tape things down and there is no way for us to adjust things easily when we need to. This is just one of those things. If anyone out there wants to donate an optical table to me, please feel free to contact me through WordPress.
Taps are done with a spacer that is 0.5″ in height. The cylinder is placed on the spacer and then the spacer is removed, and…the harsh mistress known as gravity does her magic.
We have two separate scripts that analyze the data. One that Damian wrote in Python, and one that I wrote in Octave. I may incorporate the two so that we have a gui that can be used cross platform for future endeavors in the Smyth Lab. I’ll have to talk to Damian about that.