This document summarizes the materials and components used to construct the nine lab sessions. Practical solutions are included to problems we encountered when building and using the lab equipment. Other information includes vendors, their websites and drawings for key subassemblies.
Lab 1: 1st Order Spring Damper Translational, Video Data Capture
- Airpot Precision Air Dashpot. We use an adjustable glass dashpot that is covered with rubber to protect the user if it breaks. Model numbers we use are (2K)S95-A200 or (2K)S160-A200-F275 (603/382-4179). Look at the website of Airpot.
- Angle plates. One of the angle plates is a mount for the dashpot, the other a mount and clamp for the spring cantilever. The 3X3X.375 inch angle plates were ordered from Pierce Aluminum. The drawings for these angle plates are: plate 1 and plate 2 (.tif files, use right mouse button and 'save as...').
- Bolts and ruler. The bolts should be mounted to serve as stops for the cantilever to prevent damage of the airpot. At first we used plastic rulers as a scale for the deflection of the cantilever, but the plastic rulers appeared to be less visible with the webcam than the pieces of paper.
- Cantilever spring use flat sheets of spring steel, hole for attachment of damper is hard to machine.
- Optical baseplate. OptoSigma, black anodized aluminum, from stock: - 18x24 inches, 1/4-20 on 1 inch centers: product number 145-1160 - 457x610 mm, M6 on 25 mm centers: product number 145-1165 Prices can be found at the OptoSigma website. Go to >'Optical Bases'>'Baseplates'.
- Stand Edmund Scientific, clamps for webcam mounting: VWR supply room.
- Webcam: Look at the Winnov website for information about these cameras.
Lab 2: 1st Order Spring Damper Translational, Video Data Capture
- Air bearings. New way, Each bearing consists of two parts: (1) S301901 - 3/4" I.D. air bushing (2) S8019P01 - pillow block housing for the air bushings Prices for the New Way bearings can be found at: http://www.newwaybearings.com/pages2000/pricing/pricingframe.html. If you are looking for other air bearing types, note that the alignment is a major concern. An advantage of this type of air bearings is that the o-rings allow for some flexibility. Be careful not to damage the o-rings when assambling. Use alcohol as a lubricant when assambling the air bearings. A collar on the shaft is used to disable lifting the shaft to much to avoid honey coming into the bearings. However, it is possible to thoroughly clean the honey out of the bearings with alcohol while they are attached to an air supply. The part of the shaft that goes into the air bearing should be precision ground and unscratched for optimal results. Do not move the shaft inside the bearings when the bearings are not hooked up to air supply to prevent unnecessary scratching of the bearings and shaft.
- Air supply. Quick connectors and tubing from Beswick
- Angular sheet. This is a small version of the polar plot we stick to the screen printed on a transparent sheet. A larger version of this .gif file can be found here. This image can of course be printed with the same dimensions, but with higher resolution.
Small polar plot .gif file
- Collar Whittet Higgins aluminum split-collar clamps: partnumber SC-12A (split collar-size, aluminum). We use 3/4" inner diameter to match the shaft and air bearings. Look at their website at http://www.whittet-higgins.com go to 'Collars'>'SC-A', order from Kaman Industrial Tech: http://www.kamandirect.com (781/935-7590).
- Flywheel
- Frame
- Honey. We have chosen honey as the viscous fluid to attain time constants on the order of 1 second with relatively loose geometric constraints. Furthermore, honey is environmentally safe and can be cleaned up with water. However, honey cristallizes after being exposed to open air for a few days. It is therefore recommended to change the honey when it becomes too thick. Be sure that the honey does not get into the air bearings. For instance use a collar on the shaft to make sure the shaft can not be lifted too far up. If the shaft is not concentric with the look-through tube that holds the honey, the honey will not be distributed evenly across its circumference. This nonideal behavior is hard to model.
- Optical breadboard See Lab 1.
- Shaft, ball bearing and hardened flat Thompson shaft, precision ground 3/4 inch stainless steel; 1/2 inch ball bearing and hardened flat McMaster-Carr
- Stand See Lab 1
- Syringe 20 ml with luer-lok, connection to tubing: luer-lok to tubing Cobert Assoc.
- Webcam See Lab 1
Lab 3: 2nd Order Spring Mass Damper Translational, Impulse Response: Measuring Poles
- Adjustable spring clamp
- Air bearings from New Way, see Lab 2. They do not mount directly to optical breadboard, so we made special adaptor plates from Pelrin. Drawing: sw-lab3adaptor.tif (.tif files, use right mouse button and 'save as...'). Another simpler option to attach the bearings to the baseplate would be to use toeclamps.
- Angle plate 3X3X3 inch ground steel (flat surfaces) from Suburban Tool, inc.
- Collars See Lab 2.
- Optical breadboard
- LVDT (Linear Variable Differential Transducer) Schaevitz HR-1000 ($450 each) was the best choice, because of the large clearance through the hole in the body of the sensor. LVDT's with smaller clearance caused problems with alignment. This sensor has a hole all the way through. It is unguided, i.e. does not use bearing surfaces, to avoid friction.
- Separate signal conditioner ($167) is needed for this LVDT.
- Shaft Thompson shafting, necessary threading can be specified, precision ground stainless steel, diameter 3/4 inch to match the air bearings.
- Spring
- Stand
- Voice coil LA24-33 BEI-Kimco seems to be the only manufacturer for this type of part. Prices are much lower when ordering in large quantities ($315 each when ordering 30).
Lab 4: 2nd Order Spring Mass Damper Translational, Driven Step Response: Tuning Poles
- As in Lab 3:
- Adjustable spring clamp
- Air bearings
- Angle plate
- Optical breadboard
- LVDT (Linear Variable Differential Transducer)
- Shaft and collars
- Spring
- Stand
- Voice coil
NEW:
- Amplifier The power amplifier is an Apex PA21 power op-amp in their EK21 evaluation kit.
- Power Supply Tektronix PS280 Power Supply, Tektronix.
- Signal generator Tektronix CFG253 3 MHz Function Generator, Tektronix.
Lab 5: 1st Order RC Circuits
- Electronic kits Electronic School Supplies, kits with electronic components (about $20 each)
Lab 6: 2nd Order LRC Circuits
Lab 7: Op-Amp Circuit Dynamics
Lab 8: Complex Zeros and Modes of Mechanical Systems
Lab 9: Introduction to Control Systems