EMF Pinewood Derby: A Practical Physics Project

[Stinson]

UCF, Sure am! The hood design is the school emblem. I think I came here the night I painted it, so that was the main reason for the tag I suppose.

 

[HawaiiAl]

Have you thought of using 180 degree shifting coils.Shutting off as your "car" is just above them,then rotating 180 degrees then powering up again after the car passes them.This way you'll get the most from each coil on the track.
The cars magnet used as the switch.This way you'll get a push & pull effect on the car automatically.I would definitely use DC current!AC needs to be switched to DC anyway.
I'm not a physicist so this is just a understanding.I know that coils being switched isn't as reliable as switching there direction.The iron tends to hold a magnetic direction.Good luck!I know you can do this!

 

[Stinson]

Yes I'm well into that spectrum. Taking a break from cutting sheet metal to use as a printed circuit for the shifting at the moment actually.
This is a science fair type setting, so I want random people to intuitively see when the coils are off or on and which direction they are going at any given second.

 

[Stinson]

Presentation pushed back to Monday because some of the groups aren't close to ready. I'm basically done. My original spring system for the shoe failed. It consisted of a trimmed 3x5 index card folded into a spring with a metal plate on the bottom. It seemed ideal because the index card would be study enough not to bend during forward motion, allowing me to more percicly pinpoint the contacts in relation to the permanent magnet. However, the added friction was eating up 2/3 of my forward motion. I thought about it for a few seconds and figured if that was too heavy...a gum wrapper would work. Before I found the gum I decided if a gum wrapper will work, why not alluminium foil? So I have foil hot glued to a popcicle stick and it works wonderfully. I have 2 strips running the entire length of the track and a 3rd strip I'm going to cut up into pieces for both sides. Still working out where I should cut but the system works as well as I would have hoped. I'm getting massive motion from both push and pull. I could easily travel the length of the 3' track utilizing only one or the other. Won't see both together until I'm ready to cut up pieces of track and wire everything together at once, but any acceleration boost is just icing on the cake when you don't technically even need it. I can't wait to see it happen. Right now I still just have 2 full length tracks for the same shoe and electrical tap blocking current to dial it in before I start sawing...but it clearly works. Taking the project with me to school again tomorrow, hoping to get the rest of the group on board.

My biggest issue right now has nothing to do with electricity or magnets. I need to properly align the axles of the car. It likes to drift to one side and other random issues of that nature. I compromised some of the factory pinewood derby front axel grove sticking a magnet under the nose of the car facing down in the experimenting phase. I knew I was doing the damage when I did it and planned all along to repair it later. With the electromagnetism part of the project all but wrapped with a bow, doing that sort of routine maintenance is my next real goal. I'm going to go all out and wet sand the nail axles for optimal friction reduction, repaint the car (the same way but touch-up for all the chips and burs from playing hard), etc. etc.

I couldn't be happier with my results or position of timing still 5 days from presentation day. The only thing that would make it cooler is if I did a Sonic the Hedgehog style loop-de-loop where the car has so much centrifugal force from the forward motion of the magnets that it can travel upside down. I think I will do that in my own time just for the sake of doing it, but for the graded presentation I'm just going to keep it flat.

Think I got this one in the bag fellas!

 

[the_emi_guy]

Presentation pushed back to Monday because some of the groups aren't close to ready. I'm basically done. My original spring system for the shoe failed. It consisted of a trimmed 3x5 index card folded into a spring with a metal plate on the bottom. It seemed ideal because the index card would be study enough not to bend during forward motion, allowing me to more percicly pinpoint the contacts in relation to the permanent magnet. However, the added friction was eating up 2/3 of my forward motion. I thought about it for a few seconds and figured if that was too heavy...a gum wrapper would work. Before I found the gum I decided if a gum wrapper will work, why not alluminium foil? So I have foil hot glued to a popcicle stick and it works wonderfully. I have 2 strips running the entire length of the track and a 3rd strip I'm going to cut up into pieces for both sides. Still working out where I should cut but the system works as well as I would have hoped. I'm getting massive motion from both push and pull. I could easily travel the length of the 3' track utilizing only one or the other. Won't see both together until I'm ready to cut up pieces of track and wire everything together at once, but any acceleration boost is just icing on the cake when you don't technically even need it. I can't wait to see it happen. Right now I still just have 2 full length tracks for the same shoe and electrical tap blocking current to dial it in before I start sawing...but it clearly works. Taking the project with me to school again tomorrow, hoping to get the rest of the group on board.

My biggest issue right now has nothing to do with electricity or magnets. I need to properly align the axles of the car. It likes to drift to one side and other random issues of that nature. I compromised some of the factory pinewood derby front axel grove sticking a magnet under the nose of the car facing down in the experimenting phase. I knew I was doing the damage when I did it and planned all along to repair it later. With the electromagnetism part of the project all but wrapped with a bow, doing that sort of routine maintenance is my next real goal. I'm going to go all out and wet sand the nail axles for optimal friction reduction, repaint the car (the same way but touch-up for all the chips and burs from playing hard), etc. etc.

I couldn't be happier with my results or position of timing still 5 days from presentation day. The only thing that would make it cooler is if I did a Sonic the Hedgehog style loop-de-loop where the car has so much centrifugal force from the forward motion of the magnets that it can travel upside down. I think I will do that in my own time just for the sake of doing it, but for the graded presentation I'm just going to keep it flat.

Think I got this one in the bag fellas!

You may be able to reduce friction and increase electrical conductivity of the "shoe" if you can cut the aluminium foil into thin strips for making contact with the track. This is akin to how brushes work in a motor, more guaranteed contact area with less normal force.

 

[Stinson]

My main worry at the moment in that regard is too little friction. There isn't anything but a twist holding it to the shoe. I was thinking about hot gluing a small nut to the foil high enough so the nut doesn't drag on the track but low enough so it forces the foil down from its base. They are already pretty thin. I hot glued both ends of a strip in a circle onto the top of the popscicle stick, pinched what was left together, and bent it to contact.

They are only ~1/2 inch wide and the distance between the shoe strips is wider to prevent one of them from touching both sides and shorting the battery. The trouble with testing is that if the car wonders off course more than the thickness of the strip - I lose current. Just can't have my cake and eat it too.

 

[Stinson]

Tried to make the system fail on purpose without shorting just to test the limits and one of the magnets started smoking (expected). I'm curious about long term damage to the magnet from this though. Do you think it will be good as new when it cools off again or will it be a little retarded? I need to do this more scientifically with the multi-meter. I don't have any instruments able to detect magnetic field other than other magnets though. So if it's slightly weaker I might not know it.

 

[Windadct]

Sounds like a good job, and you learned a lot.

My Brother is an Associate Prof at UCF, that is why I asked

 

[Stinson]

Oh that's awesome. I really like the school. Nice campus, all of my professors (I just started and cherry picked from rate my professor so take that with a grain of salt) have been great. There is an engineering lab I discovered yesterday where you go to take problems like the one I'm working on. They have a nicely stocked complementary tool room where you just go and hash stuff out. Sat across from a girl who was building a small remote controlled boat for a race next week.

 

[Windadct]

They have adopted a good, Hands on practical approach. I was very dissapointed by our state uni using the exact same curriculum that I had 30 years ago. You still need the academics, but practical learning is the best thing to have changed in education since then.

 

[Stinson]

My current conversation with my group memebers who so far have contributed 0%. They're pulling the plug on me. Guess I'm just building this project for fun now, which is cool. I had fun.Hey I talked to bindell after class and he doesn't want us to over complicate the project I told him back that wanted to make it impressive but he sad we need to worry about making work that something simple would do great he suggested using 2 coils to push it and one to stop it and that would be enough he wants us to build something simpe that can explain the concept of electromagnetis and easy to recreate. he also said that he would be harsher on our grade if we made something complicated to recreate in a classroom especially if it ends up not working .. he even said that what w were doing was difficult to pull off.. he said we need to explain the concept, how our device explains the concept and how we can make it better and for that part we should talk about adding more coils and what it does to it but as far as the project it should be a simple model

Me:
build it

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Sebastian
We should still use what use have but if you can take out some of the coils and only use 2 to push it and one down the track to stop it and that's all we need. This would be easier than finishing connecting all 5 or even making a new one..
no it wouldn't
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Sebastian
Yeah but if we build it we can only present one project and you have to stand behind that project

Me:
I understand the concepts because I've invested the man hours you guys build it
You have all the parts you ever gave me
except the batteries, which I can give you tomorrow if you'll be on campus
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Sebastian
Fine but we can't present 2 projects or else we'll be in trouble
you do you
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Sebastian
Why wouldn't it work with 2 pushing it?
https://scontent-mia1-1.xx.fbcdn.net/hprofile-xat1/v/t1.0-1/p32x32/11255094_10208135860618383_8521194217907296350_n.jpg?oh=3cf09b4985b213f6a7ad6274812503cb&oe=577340C5
Landon
What if we all meet this week and toy with what we have?***This is week 3, NOW they want to meet, I've been sharing my ideas and progress with them and it usually never rated more than a "seen" with a check mark next to it. wtf...***

Me:
Yall have leached off my long enough, build it
you don't appreciate all the dang I went though to create a masterpiece, that's fine, I'll help you with your report, but you build it
https://scontent-mia1-1.xx.fbcdn.net/hprofile-xaf1/v/t1.0-1/c47.47.584.584/s32x32/600015_3431901215887_975018957_n.jpg?oh=cea544b46e303e32931eaa3d5f1d5cf9&oe=578F67A4
Sebastian
He said it just need to move and stop enough to explain the concept he even said he wants something simple nothing hard

Me:
simple and nothing hard - that's my whole point.
you got this. good luck
you already know I can do it
You need to go though the learning process yourself
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Sebastian
We do appreciate it that's why we want to work with what you have and give bindell what he wanta
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Landon
No one is leaching. We all understand how it works. We're just afraid that too much might end up hurting our grade. Let's use what we have just simplify it to meet the rubric.

Me:
YOU make it

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Landon
Let's make it. As a group! We have all the parts

Me:
I'm not bringing my parts
we can do it with our group parts I guess
Like Kasey said, you never asked me to go find all that stuff so you shouldn't be expected to remburse me in any way. That's fine, but this is your project now. You take lead. You get the parts. You make it happen.
When you explained that the motor demonstrated in class didn't work by changing current back and forth I didn't even know how to respond. You have no clue how this stuff works, and you need to learn it.

 

[Stinson]

This was the motor demonstration referenced. They don't understand the concept that the wire has enamel and it is scraped off with 180 degree separation. I explained it to them and showed the my own coils with scraped off enamel all the way around. We agreed to disagree. I need to study for my Diff Equs test anyway.

 

[Stinson]

Can you just connect 2 of the coils and then a 3rd to stop it? What we need for the project you already built but instead of connecting all 4 and then 1 to stop it you can just finish it by connecting 2 .. it's the same as what you were trying to do just less connections

Me:
No. You build this. Yourself.
I'll build mine for fun an further understanding for whatever report we make.
Pretend everything I have doesn't exist
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Sebastian
It's fine I'm not asking you to destroy it.. I'm only saying for the presentation stop at 2 and after that you can do w.e. you want it's your creation

Me:
I'll show up and watch but this is all you
You guys have literally done nothing.
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Sebastian
We all want to get a good grade and the way to do it is to give bindell what he wanfa
Wants *

Me:
If you didn't jerk and moan so much I wouldn't even complain about it, I was having a blast. But I've already done way more than my fair share. I leave our fate in your hands.
Landon wants to build something that would be cute coming from a 7th grader. Kasey wants to glue the work we do to a some colored cardboard...whatever, just do it.
Sebastian at least took an interest, so I appreciate that, but if you guys want to take over and show some initiative just do it already.
I've been waiting for a drawing or a prototype or ... ANYTHING from any of you for WEEKS.
Most of my designs and ideas rated a "Seen" and a checkmark but nothing more. You showed no interest. So I pressed on.
If you want to make a simple project, that's fine...make a simple project
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Sebastian
We want what's best for the group.. I don't get why you're getting all defensive when what I told you is what bindell told me . I'm not making this dang up. . I'm not saying you're wrong and that it won't work all I'm saying is bindell wants something smaller easier and faster to recreate
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Sebastian
It's already there in your hands

Me:
Then MAKE IT
Make something
make ANYTHING
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Sebastian
All it needs it's some tweaking
Are you going to finish yours?

Me:
if you wrap a wire around a nail it will be that much more than any of you have done put together.
Yes I'm going to finish mine, for fun, I'll probably over the summer. I need to study for other classes anyway.
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Sebastian
Dude what you're doing right now putting up this front and not willing to cooperate is worse and it's hurting the group more than check marks and us not responding

Me:
****ING MAKE SOMETHING With your hands!
You like to watch me with your arms crossed placing bets betting on whether I'll fail
Try it yourself

--------------------and that's the end of this project for now. RIP
I'll pick this back up again (soon) when I don't have looing exams. Honestly I'll probably finish it tomorrow (my diff eques exam is in the morning).

 

[Stinson]

Like...If they would just let me do the project I was happy to do it without complaints. They don't want to touch a tool though. Psych majors and the like. It's true that I'm an EE major on paper but this is physics 2...it's the first class I've ever taken that deals with electricity, so we're all on pretty even ground.
I'm going to stop sharing these after this. I just want to show you why I'm suddenly stopping. I'll pick it back up and finish real soon though.

It doesn't have to be 100% or 0%. We're a groups, and that's one of the aspects of the rubric. Let's all chip in 25% and get this project done.

Me:
So far I've done 100% and the three of you combined have done 0 %. Chip in 25% each and we're square.
No no no that's not true.
Sebastian helped me saw the groove on the top of the car for the magnet.
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Landon
No one asked you to put in that much work. You said yourself you are doing this for fun.

Me:
Yeah...I enjoy it...and I would have kept on enjoying it until it was AMAZING if you weren't back seat drivers. Take the wheel.

 

[Windadct]

Ah. Bummer, but you have had your first lesson in 2 valuable aspects of engineering, 1 Developing a clear specification, 2 Project Managment is not easy...more projects fail due to these two areas, than the engineering.

 

[Stinson]

Sorry for posting drama yesterday in a passion filled rage. I regret doing it and It won't happen again. I don't know what will happen with that but as of now no change. I'm not letting them break down everything I've accomplished in a sudden realization of their laziness to put together a kindergarten project though. Hopefully they are building something. Let's get back to work.

I have working coils which is sweet but I need to automate them. Here is how I plan to wire my shoe so each coil works in both directions:

I am going to start physically cutting and sawing now, look good?

 

[Stinson]

It works. Automated. The car moves from coil to coil with the flip of a switch. It is incredibly slow though. I'm trying to think of ways to optimize the system. Three biggest areas: quality of connections, friction, more and larger electromagnets.
The connections are sloppy because I have been constantly taking them apart and rearranging. A little solder should go a long way compared to alligator clips or even loose wires mashed together. Friction comes into play from both the car itself and the shoe. I've used 5 different shoe designs so far, each with their pluses and minuses. My last design consisted of aluminum foil weighted down by some long screws I got from one of the motors I took apart for education. They are maybe 1 1/2 feet long and only threaded at the base. The rest of the shaft is basically an iron rod, which was hack sawed into pieces and hot glued to the foil. It was my greatest success with friction reduction but connection quality was poor. Right now I'm simply using some standard wire bent in a U-shape and forced down onto each track. Connection is better but friction is much worse. Overall a + to net force though. My next thought is to suspend some aluminum welding plate across the tracks by string. Maybe tomorrow. With a shoe my movement is ~3-4 inches. Without a shoe hard wired I get over a foot. I'm also going to move the magnet closer to the track. It's currently in a slot cut into the roof so If i go too far I will have literally cut the car in half. In that case I'll just make a whole new car and put the magnet on the bottom to begin with.

The main take away is - it works. It really freaking works. I just need to make it better, take it all apart, paint it, and put it back together again focusing on proper wiring as opposed to a sloppy birds nest that is "just good enough" for quick checks. Cheers!

 

[the_emi_guy]

Great work,

Wanted to remind you again of the idea of using "brushes" for the shoe.
Many years ago in my youth I build a motor from junk parts, hand wound electromagnets etc. (seeing your project kind of reminds me of that).
To make the contact between the spinning part and the stationary part I used a piece of 1" wide copper tape. Didn't work very well, motor barely moved. I could tell from the sparking that it was only making contact in one microscopic spot on that wide tape. If I tried to squeeze it to force more contact I was up against friction.

Then I took out some scissors and cut the copper tape in from the ends forming about 20 really thin "fingers". Now the motor spun like crazy. I could see sparks coming off of all of the fingers, and very little friction was created.

Cheers

 

[Stinson]

Oooooooh brilliant. When you said "brushes" earlier I thought you meant brushes in general. Like starter motors have "brushes". You mean like a hair brush. ::mind blown::
My current setup has regular 18 gauge wire in a U shape.
My next prototype will be a metal plate suspended lightly lower than the contacts with fishing string.
I have never even heard of copper tape but that is a wonderfully helpful story. Thank you.
(I said no more drama but since it's anti-drama I thought I'd update I've smoothed things over with the group and we're all friends again)
I'm having them each make a shoe design and we're meeting tomorrow to run this thing though its paces.

 

[Stinson]

*no pictures because I took the whole system completely apart, sawed off the excess wood, and painted it (still wet at the moment).
I'm going to put it all back together in a more permanent configuration with more permanent and efficient soldered connections as opposed to just mashing wires together. After that I'll run it and get it on video and post it here.

 

[Windadct]

Glad to hear things smoothed out with the team.

By the way I like the "switching" scheme you used, good use of logic.

I was suspicious of the "shoes" and not having too much friction. (Pinewood derby cars are all about friction (1) and Weight distribution (2) ... )

One way to reduce the issues with the brushes / shoes is to use relays, use them to energize relays, and the relays to energize the load ( coils) - however in a loose assembly and little time - the inconsistent connections of the shoes / brushes may make the relays chatter, and possibly make the issue worse. But since the load (current) feeding the relays is less than the coils - you should be able to reduce the friction, etc.

A good project since there are a good number of subtle issues to learn...

Oh -- at the end - post a video...

 

[Stinson]

Presentation day was yesterday. It worked and we scored a 2! Professor graded it himself saying he thought it was excellent and insinuated it may have been a 3 except the lack of teamwork. Easily put 100 hours into this thing over the last 10 days, so after the presentation I just skipped my next class (test debrief) and went to bed. Slept solid an uninterrupted for 20 hours until my alarm warned of this morning's classes. All in all it was a success and another judge invited us to a second presentation Friday which will be a high school field trip.

The group to our left looked neat on paper but the guy who had the physical representation didn't wake up to bring it in. Ow. He texted them half an hour after judging started to say he just woke up and the judges kept saying they would circle back around but he never made it. The group on the other side had electromagnets in the upper portion a clear acrylic cylinder with a piston head of permanent magnets in the tub below it. It was supposed to move up and down similar to a car engine and turn a crank shaft attached to a fan but didn't work unfortunately. I didn't get a chance to walk the room and check the others out, which I was really looking forward to.

Got some other stuff which needs attention at the moment but I'll hook it all back up and film it later this afternoon. Thanks for all your help!

 

[sophiecentaur]

Excellent, excellent, excellent! Congratulations; you deserve a massive round of applause for your stickability.
We will hear from you again, I am sure.
Don't forget to document what you have done, with plenty of pictures and writing in a file. It will impress someone when you apply for an academic course or a job. A transcript of this thread could also be good for you to record; it will show how you are capable of getting what you want out of people!

 

[Stinson]

Just letting you know I haven't forgotten this thread. Physically broke the car a week or so ago during trasnport. Tried to hot glue it back together but wasn't really successful. All the structurally unwise prototype sawing compounded together and it snapped in half where the magnet would go. Making a new car (and going all out to make it look great, as it will probably be simi-permenatly displayed in my house somewhere) which is why I haven't posted a video. Exams are looming, the follow-up project for this class is underway, and I'm just generally busy. I haven't forgotten about the video though and I will make it as soon as I finish this car. I'm using bondo to widen the classic pinewood derby block so the wheels will be covered like a real life car - and going for a corvette look. I go out to the garage and do some sculpting in-between studies as a fun active break and hope to produce a somewhat well done Youtube video, which I will share here when complete. Thanks again for all your help and support.