Time for a new project with students. Creative ideas?

[MikeFairbanks]

I haven't been on this site for a long time (probably a year...not sure), but some of you might remember that I built an electric tricycle with my fourth grade science students several years ago. It's a Worksman Trike with a front hub motor, 36-volt SLA. We had a great time building and riding it. The trike is partially dismantled, but only needs new batteries and some TLC to get it right back to where it was. That's one project I'm going to do.

I taught elementary school for twenty-one years, and now am on a new journey as a middle school technology teacher. I've been trying to get a job like this for years and it's finally happened. I'm thrilled. I'll be teaching 6-8th grade, and have the freedom to teach anything I want. Each class will last about 50 minutes and I'll develop slightly different programs for each grade level.

I have a budget that's pretty generous, so I am thinking of having my older students construct an electric bike, trike, etc. They'll have to assemble everything and learn the concepts along the way.

So, I'm brainstorming. Want to help? I'm going to budget no more than $2k for it. I want to do something different than before.

Thanks for any fun suggestions that will engage students and help them be part of creating something fun and educational.

 

[Chalo]

Maybe a pusher trailer with pull/push motor and braking actuation? That would give you the opportunity to get into not only the basics of electric traction, but also control systems and feedback loops.

 

[spinningmagnets]

Do you want to break new ground, or assemble something that already has a wide appeal?

 

[MadRhino]

You could build a solar, or aeolian (cheaper) charging station for the trike.
You could build a lawnmower to pull behind the trike.
You could build a Lithium battery for the trike, using recycled cells.
You could build a fairing for the trike, and measure the efficiency improvement...
I mean, you have the trike already, and so many things can be done from it.

 

[brumbrum]

I do not know what age group you refer to so these ideas maybe pitched wrong.

You could set a brief for a problem to be solved with a limited number of items given to the students. It could be based around speed and distance.

Something more creative could be to make a soapbox racer and implement an electrical motor into it.... Such as a trike with one rear wheel drive.

Or to make something useless or over engineered like a 'William Heath Robinson' mechanical/electrical invention. for instance, use of an electrical motor to catch a mouse, or kick a football or wash a window.

Are these to be group activities of individual projects? What size classes and what age? How many lessons to complete the project?

 

[MikeFairbanks]

Thanks for the replies. Perhaps you guys can help me refine as I think I have an idea.

The age group will most likely be seventh grade (about 12-13 years old). I don't think I'm going to have my sixth grade kids do it, but eighth grade might. I'm not sure. I have a lot of other technology and projects. They can't all build e-bikes.

Here's what I have in mind:

1. I'm thinking of buying two steel single-speed bikes (most likely BMX bikes). Both bikes will be identical and will have hand brakes. They will also be completely unassembled.

2. I'll order two identical e-bike kits.

3. I have two seventh grade classes, but not all the kids will work on this project (we are doing other technology like digital set design, code, 3D design, etc.).

4. One period will have a team of five boys and girls, and the next period will also have a team of five boys and girls. Each team will build the e-bike together, and will complete a few written assignments along the way (they need to know the theory behind the bikes: electricity, physics, etc.).

5. There will be parameters (the bike has to function properly and safely over a course that involves straight-aways, cone sections, etc. All tests will be conducted on grass (we have several flat fields) for safety, and the students will wear helmets and pads (geeky, but necessary).

Other students in the class will film the activities, edit the videos, etc. as part of their projects.

Finally, all of it will have to be disassembled and put back into the storage containers. I'm assuming some parts will be more consumable than others (kids might lose a bolt, break a part, etc. I'll have to budget for the spare parts).

The project will repeat every nine weeks for a total of four builds per year (times two classes).

So, what do you think?

Which parts will break frequently?

What would be the ideal bikes?

Should I go cheap (SLA) or Lithium? (note: if we go lithium it has to be a manufactured plug and play setup. That's one area I don't want the kids to experiment with).

Any thoughts are appreciated. Thanks

 

[Chalo]

Since runtime likely won't be an insurmountable issue, and because having to carry along your energy source is the central problem of EVs, I think SLA batteries are a good idea. Lithium takes the teeth out of weight distribution, depth of discharge, and other constraints on EV design. Grappling with those issues may be more educational, and give your youngsters a better appreciation of the benefits of both good design and better batteries.

 

[MikeFairbanks]

Since runtime likely won't be an insurmountable issue, and because having to carry along your energy source is the central problem of EVs, I think SLA batteries are a good idea. Lithium takes the teeth out of weight distribution, depth of discharge, and other constraints on EV design. Grappling with those issues may be more educational, and give your youngsters a better appreciation of the benefits of both good design and better batteries.

And it's more economical.

The bikes will not be used for long distances or heavy loads, hills, etc. They will be used on the school campus (which is flat). I don't want a lot of speed, obviously, but I do want torque. I want them relatively quick off the line. We will use thumb throttles and it would be nice if they had a little bit of punch to them. I suppose 20-inch wheels will help in that regard.

Also, I'm looking for a reliable U.S. vendor. I'm probably going to go with ebikekit.com, but one thing I found challenging (unless I surfed the site incorrectly) is that I'm not sure if they still sell a rear-mounted direct drive. It seemed that they only sell DD front mount. I might be wrong about that.

 

[MadRhino]

DD motors are still front or rear

Well, building a battery out of recycled round cells is not a dangerous task, and very educational. They would have to measure the capacity of each cell, parse those that can be saved and matched, assembling parallel and serial groups... They would learn all the aspects of battery technology and management. This is a project by itself, and a different group could work on it while the other are building bikes.

SLA has no future, the kids do and they should learn thechnology that will grow with them.

 

[dogman dan]

Out of stock on the rear DD, till early october.

One thing you might look at,, have them just do science with whatever you end up building. Add a CA, and have them graph charts of efficiency at various weights, speeds, with panniers and without, towing a trailer, etc. Do solar charging too, like a solar trailer. Then you can also examine it's effect.

They will have fun with the e bike, but what they really need to learn at that age is how to analyze a problem, collect data, graph the data, etc. Rather than memorize the math, expose them to how to set up a one variable experiment.

Something nobody taught me, till college. They just wanted you to memorize boyles law and shit, rather than learn what science is in high school.

 

[MikeFairbanks]

You guys have awesome suggestions. Dogman, I sent an email to Jason to chat about kits.

Mad Rhino: You have a valid point about SLA, so maybe I'll do one SLA kit and two lithiums, or two SLA and one lithium. (S)LA is still very relevant as it's used in every single gasoline-fueled car, lawnmowers, etc. as starting devices and is sold everywhere. But they need to know what's current and the future as well.

I won't be able to devote all nine weeks to the projects, however, so I'm not sure how in-depth I'll get on electrical theory (in terms of battery performance, etc.). For now I want to have the kits available. Some of the kids have no experience with anything technical other than phones and tablets. My class uses a lot of computers, tablets, etc., but only as tools. There's another teacher in a dedicated computer lab who teaches the kids how to use computers, office suite, typing, and a little bit of code.

My class is more about hands-on tech, including the design process, multi-view drawings, isometric drawings, 123D Design software, the history of technology (all that is in the first two to three weeks), and then they move on to simple robotic kits, advanced robotic kits, digital imaging and set design, video editing, and 3D printing (plus much more). I might get a Carvey as well for our lab for cutting wood, metal, foam and plastics (it's kind of a reverse 3D printer. You put in the rectangular block of material and the machine cuts to your programmed specifications. We already have a bunch of 3D printers, so a carving machine (mini-CNC) is good because it can do a variety of materials, not just plastic.

 

[Mundo]

You could turn a hub motor into a wind mill, then charge batteries.

 

[spinningmagnets]

Since it's for a 20-inch wheel BMX, I'd stick with 36V. I'd spec high-current cells, so you could use a very small battery, since it would never be ridden long distances and would be charged up whenever its parked.

With high-current cells, you can charge at a faster rate, like maybe 5A

 

[MikeFairbanks]

I've been chatting with Jason Kraft at EbikeKit.com, and it looks like we're getting it put together. I'll order 2-3 kits:

20-inch rear DD, 36 volt SLA.

On a separate note, we're also getting a mini-CNC machine (the X-Carve) for carving 3D shapes out of solid materials (foam, plastic, wood, soft metal). It'll be great to be able to manufacture parts for various projects (battery holders, clips, etc.).