Friday, February 29, 2008
EMERGENCY NOTICE ...
SAT 03/01/2008
DEPART: 8AM
RETURN: SAT AFTERNOON/EVENING.
===============================
IF YOU HAVE SIGNED-UP TO GO (OR IF YOU DIDN'T SIGN UP, BUT YOU NOW WANT TO GO) ON THE JACKSONVILLE FIELD TRIP (BUDWEISER PLANT), PLEASE CONTACT DOUG JONES AT ONCE. I MUST GET THE NAMES SUBMITTED BY YESTERDAY AT 4:30 PM.... BUT NOBODY RESPONDED TO MY EMAIL.
EMAIL ME AT
jonesd@tcc.fl.edu
OR CALL ME AT 850-201-8120.
WE'LL LEAVE AT 8AM (REVISED TIME) FROM THE FACULTY PARKING LOT BEHIND (TO THE IMMEDIATE NORTH OF) THE SCIENCE & MATH BUILDING.
WE'LL TRAVEL IN THE TCC FORD 350 13-PERSON VAN.
AND WE'LL RETURN THE SAME DAY (SAT).
PLEASE, PLEASE, PLEASE CONTACT ME ASAP
Tuesday, February 26, 2008
Friday (2/29) meeting and tour
The meeting will be in SM260 as usual. We will leave for the tour about 3:30.
Sunday, February 24, 2008
Compressing a Quarter
A standard quarter is electromagnetically compressed to the size of a dime in, literally, the blink of an eye, a flash of light, and a loud crack.
The forces on the coin are produced by an estimated 100 kA current in a 10-turn copper solenoid winding. The induced current (about 1 MA) in the outer edge of the copper core of the quarter interacts with an estimated 58 T magnetic field produced by the solenoid, compressing the quarter radially. The peak field last for about a millionth of a second because the coil is vaporized by that current.
The energy needed (about 4600 J) is delivered by a 178 uF capacitor charged to 7200 V. The capacitor, which contains about 1.28 coulombs of charge, takes several minutes to reach its final voltage. A display next to the demonstration included a page on the principles of operation of a quarter shrinker from "Stoneridge Engineering", the Teslamania web site of Bert Hickman that gave additional details for a system similar to the one we saw. My independent calculations at the bottom of this article roughly confirm what is on that page and the display at the magnet lab.
Side comment. You would get 4600 J of energy if you dropped 47 kg (about 100 pounds) a distance of 10 m (about 33 feet). Now imagine all of that energy concentrated int the small area of a quarter. Splat.
Tools of the trade:
An assembled coil is in the background. The coil itself (left foreground) is about 10 turns of 14 gauge wire (wire that would normally carry no more than 15 A in commercial use, and will melt if used with 166 A). The quarter is sandwiched between two cylinders of G10 fiberglass (right background) to center it within the coil. (Wood had been used in the past, but the G10 survives and can be reused from year to year.) Tape holds it all in place.
Centering the quarter and ensuring it is perpendicular to the magnetic field is crucial to making sure the forces compress the coin rather than twist it. Oh, yes, and the vial contains fragments of copper coils used in past experiments. The lighter colored pieces are probably stainless steel chipped off of the box that is used to contain the explosion of the coil.
This last photo shows the interior of the box used to contain the explosion of the magnet coil. You can see the copper from the used coils embedded in it. I also notice that the stainless steel panels on those three sides appear to have been added after the fact to the inside of Lexan panels that appear to have been the original design plan.
The Physics Details:
I collected a lot more details this year than I managed to get last year, correcting some of the information I used for back-of-the-envelope example in PHY2049 this year and last. [I had remembered the 1 MA current, but not that it was the induced current in the coin or the number of turns, and did not have enough info to estimate the R or L of the circuit being used here.] I now know he used 14 AWG 200C copper magnet wire with 10 turns in the coil. That info, and my estimate that the coil has an inner diameter of 2.4 cm (to fit around a quarter) and a length of between 1.7 cm (absolute minimum for the wire diameter) and 2 cm, are essential to a qualitative understanding of what is going on.
The length of the coil plus 10 cm for each lead is about 1 m, so we can estimate its resistance at about 0.008 ohm. All other conductors are large bus bars and will contribute little to the resistance of the circuit.
The coil that produces the magnetic field is too short to be correctly modeled as a solenoid. If we do that anyway, however, we require about 92 kA to produce 58 T, while 65 kA (see below) produces 41 T. These numbers assume 10 turns and a 2 cm length. Only 78 kA is needed to make 58 T (or 48 T from 65 kA) if the solenoid is 1.7 cm long. We always want the coil as tightly wound as possible!
We also get an inductance L = 2 uH for a 2 cm coil. An on-line calculator (of unknown reliability) says those dimensions would give 1.8 uH, while 1.7 cm gives 2.0 uH. I will use L = 2 uH as a conservative value. Notice that a shorter length makes the inductance bigger, which is a bad thing.
The RC time constant of 1.4 us (micro seconds), with an initial current of 900 kA, tells us what would happen if there was no coil (inductance) in the circuit. Unfortunately, the coil does not like a rapidly rising current. It would take 250 us (0.25 ms) for the current to reach 570 kA if we had just the coil with an ideal 7200 V battery. However, this is actually an un-driven LCR circuit, with all three elements playing a role. The circuit has an inductive time constant of 500 us and a natural frequency of about 53,000 rad/s. The solution to this problem says a peak current of 65 kA will be reached after 19 us. A smaller inductance makes the current bigger, by the way. The estimated inductance is a critical quantity. Reducing the inductance to 1.8 uH will increase the current to 78 kA. Notice that this is just what we need to produce 58 T in a 1.7 cm coil.
Faraday's Law says the large dB/dt produces a large EMF around the edge of the coin, which acts like a single turn in a 10:1 transformer. This leads to a rough estimate of an induced current of 650 kA (perhaps 780 or 920 kA) around the edge of the coin.
Even with "only" I = 65 kA and B = 41 T, the compressive force due to the 650 kA current induced in the outer edge of the coin would be something like 2 MN. If we really have I = 78 kA and B = 58 T, the force increases to 3.4 MN.
This force only acts for a micro second or so at the peak of the sine function that describes the current (before the coil is torn apart by the equal and opposite repulsive force of the field on the coil). The total impulse is not very large, although the total energy is significant even if a lot of it is wasted.
Tesla at the Magnet Lab
The large Tesla coil shown here was producing about 250 kV at 200 kHz. The presence of an aluminum rod nearby alters the spark pattern because the current being carried off by the sparks is drawn to the grounded conductor rather than something like the overhead lights up by the ceiling.
The sparks look purple because of the emission lines from nitrogen gas. (The spark results when air molecules, mostly nitrogen, get ripped apart by the high voltage. The current is carried by a plasma.) A bare hand works almost as well as an aluminum rod, since your body is a conductor.
At high frequencies (such as 200,000 Hz), the current flows over the surface of the body. The only risk is from a burn at the point of contact. Based on the reaction of one other demonstrator, you can definitely feel it. This photo was really spectacular. The yellow spots you see are where it is burning his hand.
Important Note:
Frequency is the difference between life and death. A low frequency (such as 50 or 60 Hz) Alternating Current would be fatal at those voltages. That would go through your body and, partly because it is so well matched to the frequency our nervous system operates at, would stop the heart. In contrast, we easily get 200 kV from a van de Graaff generator in lecture demos, but the resulting small Direct Current only produces a painful shock.
Musical Reindeer
The sparks emanating from a small stuffed reindeer sitting on a smaller Tesla coil produced music. (Click the photo for a much bigger version.)
What was happening was that the air gets heated by the glowing discharge you see in the photo. If the intensity of the sparks varies at 5000 times per second (too fast to see or photograph), you get a sound wave of 5000 Hz produced in the air instead of the crackling sound of the sparks. They modulating the amplitude of the voltage delivered to the coil (and putting wires in the stuffed animal to produce many sharp points for spark production) with a music source, and you hear music.
The music went away, or was altered, if a rod was used to draw off the current in a single spark rather than the discharge you see here. Very nice.
Tuesday, February 19, 2008
Lecture Schedule for Mag Lab Open House
The open house runs from 10 AM to 3 PM on Saturday, February 23. These are the only events that have a specific schedule. Everything else is self-guided with small presentations taking place every 15 to 30 minutes at various locations along the tour.
Schedule for Wednesday Town Hall Meeting
"The Brogan" is located on Kleman Plaza downtown, behind City Hall and just NW of the Capitol. Parking is availble (for a fee) in the Kleman Plaza parking ramp as well as (for free) at meters along some nearby side streets.
Monday, February 18, 2008
Ion Sancho to lead voter education forum at TCC
[[ Although this is NOT Engineering information per se, the topic is of great interest to all citizens of a representative democracy; therefore, I post it. DJ. ]]
As part of its Black History Month celebration, Tallahassee Community College will host a voter education forum from noon to 1 p.m. on Tuesday, February 19 in the College’s Student Union Ballroom.
With Floridians now looking ahead to November’s general election, the College will offer students, faculty and staff the opportunity to learn about the importance of voting as well as voter’s rights.
Ion Sancho, Leon County Supervisor of Elections, will serve as the forum’s keynote speaker. Sancho is a highly sought-after speaker in the area of voter’s rights and voting protocol. On Tuesday, he’ll educate attendees on the importance of voting and how it relates to what is sure to be an historic 2008 presidential election.
Tom Dinh, TCC’s Student Government Association President, and representatives from TCC’s College Democrats and College Republicans are also slated for Tuesday’s agenda. A brief question and answer session is also scheduled, time permitting.
TCC will offer additional opportunities during the remainder of the month of February to celebrate the accomplishments of African-Americans who have made significant contributions worldwide.
For more information on Black History Month events at TCC, contact Cherry Alexander at (850) 201-8396 or email alexandc@tcc.fl.edu.
ISS and Shuttle overflight
Time: from 7:22 to 7:26 pm, moving from WNW to SSE across the SW sky.
Highest point in sky: 32 deg above the horizon to the SW at 7:24 pm.
You can use the Heavens Above web site (link takes you to a page suitable for Tallahassee) to get this sort of info about anything that is in space.
Saturday, February 16, 2008
VISIT THE ENGINEERING CLUB FORUM
http://www.tccengineeringclub.com/forum/index.php
You will want to visit the forum often, as that is
where many interesting Engineering Club topics
will be reported, including Aaron's report on the
last meeting (02/15/08) and the status of all the
club's on-going activities.
DJ.
Friday, February 15, 2008
Electric Car Program Monday
The meeting is Monday 18 February at 7:15 pm (snacks at 7:00 pm) at the United Church in Tallahassee. The church is at 1834 Mahan Drive, which is in the woods to the north of Mahan (US-90) just west of Blair Stone Drive.
Program info:
The speaker, Mark Hunt, will talk about his experience converting standard cars to electric cars or hybrids, the advantages and disadvantages of these vehicles, their economics, and the present state of commercial hybrid vehicles. He works at King Cobra, a shop on Orange Avenue, building and modifying race cars as well as electric cars. He learned his skills working on orange grove equipment on his father's farm in Indian River county.
I suspect he works with Al Simpler (who has some all-electric sports cars) and so I expect Al (of Simpler Solar Systems at 3118 W Tharpe Street) will be there also. FYI, Al Simpler has offered free assistance to Aaron's solar conversion project.
Driving tips:
If you are coming from the east (or turning from Blair Stone), their two driveways are right after Sasanqua Drive, only about 500' past Blair Stone. The first is the exit, the second is the entrance, so it is hard to miss if you are ready to turn right as soon as you pass Blair Stone.
It is very easy to miss if you are coming from the west (from TCC or FSU down Tennessee St, which becomes Mahan). You must slow down and look for the last median cut before Blair Stone. You turn left about 200' after you go past Pointe Ct (on the right). Their sign is small and eco friendly so it is easy to miss if you are going 50 mph. If you miss the turnoff heading west, you have to go quite a distance before you can make a legal U turn to come back.
Monday, February 11, 2008
Letter from Susan Ray @ MagLab
Just wanted to make sure the TCC Engineering Club is aware that the Mag Lab Open House is coming up – Feb. 23 from 10 a.m. to 3 p.m. I think this would be of great interest to the students. You can find out more here: http://www.magnet.fsu.edu/education/community/openhouse.html
In addition to the self-guided tour and demonstrations, there also will be talks this year, two by engineers.
I’d appreciate it greatly if you could forward this to Aaron so he can mention it at the upcoming club meeting. If any of the students is interested in volunteering, they can contact me directly.
Thanks!
Susan Ray
Associate Director, Public Affairs
National High Magnetic Field Laboratory
1800 E. Paul Dirac Drive
Tallahassee, FL 32310
(850) 644-9651
sray@magnet.fsu.edu
www.magnet.fsu.edu
P Please consider the environment before printing this e-mail
Friday, February 8, 2008
Upcoming events
Saturday, 9 February: Darwin Day
at Florida State (College of Medicine)
Among other things, Sir Harry Kroto, Nobel Laureate and FSU Professor of Chemistry will be speaking from 10 to 11 AM. He co-discovered fullerenes, more commonly known as Buckyballs. One variation of this, carbon nanotubes, are rapidly finding applications in engineering. One day they will be used in concrete. There will also be a hands-on bucky-ball building activity for children registered for it. Details are on the web.
Friday, 15 February: Club meeting
Wednesday, 20 February: ASME Town Hall meeting
This will be held in the evening in the TCC part of The Brogan Museum downtown. We plan to participate. Details at the club meeting on 2/15. See other entries in this blog.
Saturday, 23 February: Mag Lab Open House
This is a big deal, running from 10 AM to 3 PM. They will once again be using extremely high field (about 40 T) disposable (totally destroyed when used) pulsed magnets to compress a quarter. This is a must see.
Click here for details from the mag lab.
Other old standby demos (air powered potato cannon, diamagnetic properties of liquid oxygen) and tours will be done once again. You can talk one-on-one with members of the engineering faculty (mechanical, electrical, and civil) who work there building magnets and other devices.
They are also advertising a new feature, a musical tesla coil. I assume that they saw one of these videos from YouTube and said "we can do that!".
My brother told me about this "Lightning on the Lawn" show. Another one shows a guy in a mesh suit carrying a row of light bulbs around between the coils. Notice how the bulbs light up when struck by the electrical energy?
The mesh suit provides a "Faraday cage" effect that protects the wearer from AC high frequency "lightning" strikes.
Saturday, February 2, 2008
CNC Machines (Computer Numerically Controlled Machines)
Friday, February 1, 2008
MESSAGE FROM AARON:
Just wanted to send out a few items to everyone and let you know what's going on with the club:
Cart To Solar Project
We were sucessful in receiving our grant from the College Innovation Fund for $2500. Thank you everyone that showed up in helping write the grant proposal. It was a great success. Now it's time to work.
The P3 KillAWatt has come in, and I have been running some preliminary tests with the device as well as arranging a data collection method that we can coordinate with the Plant Operations department that will work good for all of us. The majority of carts do not have working hour meters so I am looking into either purchasing new ones or designing one using a LM555 timer. Anyone interested in a small electronics project, let me know...
As far as the solar panels go, I was going to have them ordered monday, but the person that is in control of the grant money won't be in until next week. On monday, I will be going in to make the initial order of solar panels. However, we do have a decision to make. Since PowerFilm is giving us a 40% discount on the panels, we have the option to possibly have 4 or 5 carts running around with panels. Is that something we are interested in?
We have also been authorized to have all the work on this project to be accredited through TCC's Volunteer Office. I will be giving everyone that participates in this project a TallyScript form where you can log the hours that you work on the project. If you can get at least 20 hours of volunteer service this semester, the volunteer office will have that documented on your transcript. This looks VERY GOOD and may help you in the future if volunteer services might be needed. With the cart project as well as other things we'll be doing, there is more than enough opportunity for all of us to get some volunteer service on our official college transcript.
CNC Training at TCC
With great thanks to Beth Mann Pace, the TCC EWD will begin offering CNC training. Check out the news release on TCC's web site:
http://www.tcc.fl.edu/about_tcc/news_events/news_archives/2008/january_2008/tcc_division_of_ewd_offers_cnc_machine_training
CNC's are amazing machines and are an integral part to the manufacturing industry. I used to program vector images of diesel engine mounting brackets that were converted for use on a CNC. Anyone interested needs to contact Ms. Pace as soon as possible.
Trail Work Volunteers
This weekend there is an epic trail works project going on at the Cadillac Trail on Lake Lafayette. I will be going out there to work on this major redesign project that is being coordinated by Trail Dynamics and the City of Tallahassee Parks Department. THis is something that we can take part in, and get volunteer hours that can go on our transcripts. I will be out there on Saturday afternoon as soon as I get out of the lab, and again on Sunday. Anyone interested, please call me at 850.251.9955 for more information.
Beer Anyone?
Just trying to get your attention. Quinn Straub, the Chair of the FAMU/FSU ASME Club has extended the opportunity for us to join them in a trip on March 1 to tour the Budweiser Plant in Jacksonville. There is also planning for a possible nuclear power plant in the works. Keep it in mind. We'll talk about it more at the next meeting.
New Web Site!!!
Thank you Michael. The Site looks great! When you get a chance, check oiut the new design of the club's web site: http://www.tccengineeringclub.com
This new site will definitely help us communicate a lot better. Michael has done a great job on creating an integrated forum and is now working on getting the blog up and going. This is great. While you're visiting the site, make sure to register for the forum and post your energy questions for the Town Hall Meeting. 19 days until the meeting and we need a lot more questions.
I am sure that there are some other exciting things that I am missing. There are a few other items that are in the works right now and I will inform all of you as to the details as soon as they come available. Please email me with any suggestions/ concerns that you may have about the club. bauld9a5@mymail.tcc.fl.edu
Thank you for you time and support,
Aaron Bauldree
TCC Engineering Club Chair
850.251.9955