Introduction: Lightweight Electric Motorcycle With Bamboo Frame

Picture of Lightweight Electric Motorcycle With Bamboo Frame
For our high school senior project, we have created a bamboo electric motorcycle. This project has been extremely fun, challenging, and time consuming; this is not something you can do over a few weekends. The end goal for us was to create a working motorcycle with a bamboo frame and an electric motor, as well as to create an Instructable.

 The main stages for this project are:
  1. Setting your goals for distance and speed and creating a budget.
  2. Researching and ordering drive train parts.
  3. Testing the drive train
  4. Creating a model in SketchUp
  5. Obtaining and heat treating your bamboo.
  6. Hacking apart your donor bike
  7. Tacking the frame together
  8. Epoxy-ing  the joints
  9. Creating mounts and attaching the drive train.
  10. Wiring.
  11. Final parts and safety checks.
 
Materials:
            Bamboo (more than you think you need)
            Hemp twine (or some other sort of absorbent twine)
            Epoxy and hardener
            A donor bike frame w/ fork
            Hot glue sticks
            Pipe clamps
            Zip ties
            Lugs or some other connectors (for wiring)
            Electrical tape/heat shrink
            Plywood (inch thick and ½ inch thick)
            Rubbing alcohol
            Solder
Tools:
            Hot glue gun
            Drill (a drill press is nice in addition to a drill, but you don’t need one)
            Hack saw
            Wood saw (a band saw speeds things up a bit, as does a circular saw)
            Jig saw
            Screw driver (Phillips and flathead)
            Computer w/ SketchUp
            Rubber gloves
            Ruler
           Sharpie
           Clamps
           Soldering iron
Parts:
           Electric motor
           Batteries and charger
          Controller
          Throttle
          Bicycle breaks (front and rear)
          Bike wheels and tires (front and rear)
          Handlebars and stem
         Two switches (one for controller killswitch, one battery circuit breaker         Rear sprocket (match pitch with motor sprocket)
         Chain (match pitch with motor sprocket)

Step 1: Setting Your Goals for Distance and Speed and Creating a Budget

Picture of Setting Your Goals for Distance and Speed and Creating a Budget

Setting goals for distance and speed will help dictate your parts and budget. As an electric motorcycle, it won’t be particularly speedy unless you get a very large motor. Realistically, the top speed for this project should be somewhere between 20 and 40 mph, depending on gearing and motor choice. The upside of this is that depending on where you are living if it goes under a certain speed you do not need to get it certified to ride it on the streets.

For our project, we set the goals of a 25 mile cruising range and a 25 mph top speed. Because of some gearing complications we actually ended up with a top speed of around 35 mph.

Our budget ended up being around $1100, including one blown controller and a few tools we didn’t have already. Your budget will most likely be your limiting factor. It will determine the size and power density of your batteries (your most expensive part) and how powerful your motor is. It is important that you leave an extra couple hundred dollars in your budget for unexpected costs, because who wants motorcycle that almost runs?

Step 2: Researching and Ordering Drive Train Parts

Picture of Researching and Ordering Drive Train Parts
 Based on your goals and budget, you should research and order your drive train. Our drivetrain components are mostly parts manufactured for electric scooters. We decided to go with a 48 volt system as it was the best compromise between power and weight. It is very important that all aspects of your drive train are rated to at least 48 volts (or whatever voltage you decide on), because otherwise something might explode.
 
Our drivetrain consisted of:
            A 48v 1200w motor
            A 48v YK42 controller
            Two 24v 20ah LiFePO4 (Lithium Iron Phosphate) batteries in series
            A hall-effect electric scooter throttle
 
 
Doing some quick research I was able to find all these parts on eBay for fairly reasonable prices.
 
Important notes:
            If you do end up getting a LiFePO4 battery (and we recommend that you do), make sure you             get a balancing (sometimes called “intelligent”) charger.
            It’s very helpful to get a motor that already has a sprocket attached. The standard for electric             scooters fits #25 chain, which is ¼” pitch and is ¼” wide. 

Step 3: Testing the Drivetrain

Picture of Testing the Drivetrain

Once your drivetrain arrives, it is important to make sure that all of your parts will work together. Charge your batteries, and then lay your drivetrain out on a table. Use alligator clamps to wire everything up. Make sure that the throttle controls the speed of the motor properly, and note which way the motor spins. Scooter motors are generally meant to be mounted on the left side of the bike, and you’re going to mount the motor pointing to the right like a bicycle chain, so you’ll probably have to switch polarity on the motor. During the wiring stages is when you will worry about what fits, for now we just want to make sure we have all the parts, that they are compatible, and that they work. 

Step 4: Creating a Model

Picture of Creating a Model

First make a sketch, and remember triangles are your friends. Once you have an idea of what the bike should look like, assemble a model. Either make a scale model out of wooden dowels or make one on the computer. Model all your parts accurately and to scale. You will do this to make sure there is spare room for your parts, that there will be a clear chain line, and that your parts will be able to be mounted properly.  

Step 5: Obtaining and Heat Treating Your Bamboo

Picture of Obtaining and Heat Treating Your Bamboo
 You should be able to obtain bamboo at a local lumber supply store or online. You’ll need both 2 and 1 inch thick pieces of bamboo for different parts of your frame. The higher-stress areas should be thicker bamboo.  
 
Before heat treating, it is important to break all of the inner membranes of the bamboo with a piece of rebar. If you do not do this the bamboo will crack, and might explode. Also, existing cracks will increase in size during this process.
 
There are two ways of heat treating bamboo. The first method is to put the bamboo in the oven. This is the easiest, the fastest, the safest, and the cheapest way, but not all your pieces of bamboo will fit unless you have access to a really large oven, or decide to make an oven. If you use an oven, set the temperature to 350 degrees Fahrenheit and put the bamboo in for as long as it takes for it to become slightly browned. It is hard to tell how long this will take, but it took about 40 minutes for us. It helps to rotate the pieces every 10 minutes or so.
 
The second choice is to use either a blow torch or an electric heat gun. We suggest an electric heat gun, because the heat will not burn the bamboo as easily as the blow torch. If you do this the finish on the bamboo will look nicer, but it will not be as thorough, and the heat treating process takes a lot longer.

Step 6: Hacking Apart Your Donor Bike

Picture of Hacking Apart Your Donor Bike
 In this step you will cut apart the donor bike frame to remove the front fork/headpiece assembly and the rear triangle. Keep the handle bars unless you plan on making your own.
 
 For cutting we suggest a Sawzall with blades meant for cutting metal. This makes it extremely easy. It is also important to secure the bike to something. We clamped the bike to a large metal table. C-clamps work great for this purpose, but there will be a lot of tension so be careful when placing and removing the clamps.
 
See illustration for cutting directions

Step 7: Tacking the Frame Together

Picture of Tacking the Frame Together

 This step is fairly simple, but extremely important. The purpose of this is to make sure everything fits together, help determine the angles, give you a chance to change things, and make it much easier to epoxy. You will not be able to change the angle of anything once you epoxy it so tacking everything together with hot glue is an important step. 

Step 8: Epoxy the Joints

Picture of Epoxy the Joints
This is a major stage, and takes a long time. We used West Systems epoxy, and it worked rather well for us. The epoxy must be pretty thin, you want to avoid really viscous stuff.
 
Setup: You should be in a well ventilated area, or outside. You do not want to be breathing in fumes from the epoxy. If you have gas masks go ahead and use them, but particle filters won’t do anything. Lay out lots of newspaper, this is a messy process. Rubbing alcohol is a must, and you’ll need a lot of it. You use this to clean the bamboo before you epoxy it as well as to clean up any errant drips of epoxy. Disposable rubber gloves that are designed to handle chemicals are also important. Don’t wear clothes that you care about, and it’s not a bad idea to wear an apron of some sort.  Having your arms protected with clothing or plastic bags is ideal. Pre-cut your string into 3 or 4 foot sections. The last thing is to have two disposable dishes or containers, one for mixing the epoxy in and one for rubbing alcohol.
 
Process: It is best to have two people working during this process. One person mixes epoxy and hardener in one bowl and then dips in string. This person then pinches the string and pulls the string through their fingers to get off excess epoxy (like papier-mâché). Once the string is free of excess epoxy, the “dipper” hands off the string to the “wrapper”. The wrapper then wraps the string around the joint, trying to keep it taut and trying to keep the joint symmetrical. Expect to do one to two joints at a time, depending on where they are. The epoxy starts to harden after about ½ hour to an hour, but takes about 12 hours to become secure.
 
Clean up: Paper towels with rubbing alcohol. This will get epoxy off skin and objects, but you’re not going to get it off your clothes. Try not to move the frame or get rubbing alcohol on the setting joints.   

When mounting the rear triangle, try to be as sure as possible to make the rear axle perpendicular to the rest of the bike.

Step 9: Creating the Mounts and Mounting the Drive Train

Picture of Creating the Mounts and Mounting the Drive Train
 However your mounting system is designed, remember that you cannot drill into the bamboo. We found that the most effective and secure way of attaching things to bamboo is with pipe clamps. Make sure that your motor mount is very solid, as it will be taking a lot of torque. 

Mounting the drivetrain:
 
Here’s the rear sprocket we bought: http://electricscooterparts.com/sprockets.html Item # SPR-2590
 
What’s nice about this sprocket is that it threads directly on to the rear wheel of a bicycle. This is awesome. Just unscrew whatever cassette is on the wheel, and screw that baby right on.
 
Attach the rear wheel w/ sprocket and the motor, making sure that the chain line is clear. You may have to fabricate a chain tensioner to keep your chain off your rear fork.
 
Next, attach the power source and controller. We suggest fabricating a battery box and then attaching that to the frame, instead of directly attaching the battery. You can then just screw the controller to the top of the battery box.
 
The throttle you bought should slide nicely onto your handlebars, you should attach this too at this point. 

Step 10: Wiring

Picture of Wiring
Once all the pieces are attached, begin wiring them together. Be extra careful to keep one battery lead taped over until the very end. There’s not much we can say here, just keep an eye on the circuit diagrams and you’ll probably have to flip the polarity of the motor. Wire a switch in between the final battery lead and controller, along with the kill switch coming from the controller. We learned the hard way that the controller’s kill switch only cuts throttle input, and doesn’t actually break the circuit.
 
We assume you have prior experience wiring things, if you don’t, find someone who does to help you out.  

Step 11: Final Parts and Safety Checks

Picture of Final Parts and Safety Checks

At this point, you should be in possession of a running, albeit somewhat uncomfortable, electric motorcycle. It is at this point that we recommend adding foot pegs and a seat of some sort.

Our seat was made by folding rags into the general shape we wanted, and then wrapping the rags with with duct tape. Still uncomfortable, but slightly less so. 

As far as safety goes, we recommend a motorcycle helmet (a bike helmet at the very least) and that you probably should avoid riding this in the rain. 

Comments

electric eric (author)2010-12-23

My longest trip on this bike was a 42km. The bike weighs a total 38kg due to the weight of the hub motor and the batteries. The 3 batteries by themselves weigh 12kg.

randomray (author)electric eric2013-01-13

Wow , close to 85 lbs . But mostly batteries and motor . Sigh ... energy storage is still the problem with electrics . Think I'll still give it a go . Thanks for posting .

___ (author)2012-08-08

Are those climbing shoes that you both have clipped on to your jeans?

sevakkishan (author)2012-03-26

nice

electric eric (author)2010-12-23

/You may be interested to see our electric bamboo bicycle. we call it the electric eric 350. the motor is 36v 350W brushless motor. The main triangle is made of natural bamboo and the chain stays and seat stays are made of laminated bamboo. The " lugs" are made of epoxy and abaca fiber.

tazerl494 (author)2010-10-01

what cad program do you use? also check this battereys out: http://www.hobbycity.com/hobbyking/store/uh_viewItem.asp?idProduct=14476 2.45 amps at 30c this can crank out 73.5 amps XD

niuthon (author)2010-06-02

nice
but for so expensive and efficient batteries, you have chosen crap motor.
in my bike range was doubled (or tripled)(on the same batteries) when i changed brushed motor like yours for brushless hub motor (both were 250 W)
almost no noise, no overheating.
So i suggest for everyone - choose brushless motors if you can

Bay School (author)niuthon2010-06-03

 Where did you get your motor? How big is it? We would have gone with brushless, but there were budget constraints... 

niuthon (author)Bay School2010-06-03

i get mine from someone on our version of ebay for about 150$ with cotroller, but they are nearly unobtainable in my country, new one can cost as much as 500$.
My brushed motor with chain drivetrain achieved only 5 miles range , it  was 250 watt motor for electric scooters.
Brushless hub motor ,also 250 watt, was much bigger and heavier , but had no drivetrain (it was hub motor just as an average one one you can see on youtube these days). And there are no batteries other than lead-acid available, so i ended with  15 kg (~30 lbs) of batteries for  22 km (~15 miles) range.
One year ago it was something of a novelty in my backwater country, so my proffesors constantly asked me how my bike works.
Anyway, it seems for me that brushless hub motors are most efficient for bicycles.


greatpanda (author)2010-03-30

Here's some data I've been waiting on for years: how far can it go on a single charge?  How is the motor mount holding up to the torque?  I never could find reliable data when I was planning on doing this back in high school, so it kinda got back-burnered since I didn't know if it'd go at least a mile or two.  


It seems that the batteries might be more easily stacked vertically if the cross piece weren't there, might be an argument for a metal frame.  Maybe I'll try it with the rest of the gearing left intact (so the bike ride doesn't have to turn into a walk once you run out of juice), I'll let you know how it turns out.  Who knows, maybe even a small dyno in series for the downhills?

Bay School (author)greatpanda2010-04-01

 The distance on a single charge is at least ten miles, maybe double that, depending on how the engine holds up. Overheating turned out to be the biggest issue with the bike. The motor mount we have is actually incredibly solid so far, but we'd recommend using bolts instead of screws to hold it in. 

That crosspiece is absolutely necessary, as far as structural integrative goes. It would be a different project if the frame was metal; the bamboo frame was super light and a metal frame would require a much more beefy engine. 

I strongly recommend against trying to work multiple gears into a project like this, because electric engines completely tear apart any conventional gearbox. 

Good luck on your project, and don't forget about engine cooling!

greatpanda (author)Bay School2010-04-01

 How much does it (the frame) weigh?  My understanding was that bamboo is actually comparable to aluminum for weight.  

Don't worry, I wouldn't dream of having the motor drive a gearbox, I'd just leave the existing gears intact and drive the wheel from the "wrong" side.  Perhaps an air scoop for the motor to help cool it, since it won't generate any heat while still.

Bay School (author)greatpanda2010-06-03

We didn't weigh it, but the bare frame was super light... Definitely comparable to aluminium. 

TSC (author)2010-04-29

Sweet!!!!!!!!!! cool!!!!!!!!!!!!!! 5STARS

mycroftxxx (author)2010-03-23

 I realize that learning and mastering the technique of bamboo bike-making is more valuable than an individual frame, and that the motorcycle frame is vastly different from the bicycle frame you salvaged parts from - but it always pains me to see one of the steps for these instructibles be "tear down a functional bike frame".  

I know nothing about bike construction, but is it possible to acquire the necessary parts for the connectors from non-bicycle sources?  (This is a genuine question, an answer of "No" or "Not safely" is fine, I really don't know.)

Bay School (author)mycroftxxx2010-03-24

 Yes, it is technically possible to acquire individual parts, but it's vastly more difficult to construct  something usable out of them.
We were originally going to make the rear triangle out of bamboo, for example, just using metal dropouts, but then we wouldn't have been able to mount rear brakes (ya can't drill into bamboo). 
As far as a waste of a bike frame goes, we encourage people to use a bike that's destined for the junk heap anyway. It's not the most ecological thing ever, but it's a lot safer unless you're already experienced in working with bikes. 

mycroftxxx (author)Bay School2010-03-29

 That's about what I expected.  I was guessing it would take several major bamboo-bike factory opening up for the attending bike parts industry to start supplying the necessary metal bits.  Ah well.  

Is there anything you would do differently on electro-bamboo-bike 2.0?

Bay School (author)mycroftxxx2010-04-01
 Ha, I sort of had to write a paper on your question, but the gist of it was this:
  • Suspension on the front fork (wouldn't be hard at all, we just need the right fork)
  • Waterproof (We'd probably use plexi and lots of hot glue)
  • Real bike seat
  • Gauges (speedo, engine temp, charge level)
  • Some way to cool the engine 
tazerl494 (author)2010-03-26

nice bike!
just tow questione,
one, what is wornge whit just puting this system on a normal bicycle! no offence intended!
and how did you make the foot pegs!
thanks so much!

Bay School (author)tazerl4942010-04-01

 1. This system wouldn't fit on a normal bike... Aside from the pedals being in the way, this bike is actually a bit longer than your basic road bike. Also, structural stability would be an issue. 

2. The foot pegs consist of one piece of bamboo zip-tied to the bottom of the frame. It's not, um, optimal. 

discontinuuity (author)2010-03-15

Why the mis-matched wheels?

We initially had a knobby tire on the rear, but it interfered with the chain line. We then got the skinniest tire we could find, just in case. 

nolte919 (author)2010-03-17

In step 2 you say "Two 24v 20ah LiFePO4 (Lithium Iron Phosphate) batteries in parallel"  I think you meant in series, not parallel.

Bay School (author)nolte9192010-03-18

 You're right, thank you. Fix'd.

Mr.Sticky (author)2010-03-15

Nice 'ible.   Two questions though...why did you decide to use a bamboo frame?  And where did yoyu get the 48v motor?

Bay School (author)Mr.Sticky2010-03-15

 We chose bamboo because it's light, sustainable, and doesn't require welding. Also, it's kinda cool.

We got that 48v motor from ebay. I checked again recently and couldn't find that exact motor again, but I did find a number of suitable replacements.

Mr.Sticky (author)Mr.Sticky2010-03-15

*you*

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