Instructables
Picture of Electric BMX Bicycle
 
Remove these adsRemove these ads by Signing Up

Step 1: Frame

Picture of Frame
13, 3:09 PM.jpg
13, 3:09 PM.jpg
The first thing to decide when making an e-bike is which frame to use. When choosing a frame, keep in mind that the size, material, and rim options. If you are going to weld mounts to it, look for frame that are steel and not aluminum. Also keep in mind that usually only 20in BMX rims and road bike rims have threads on both sides to mount an additional sprocket to. I chose a BMX frame because it it's steel, has rims I can mount to, is light weight, and compact so it can fit into a car.

Step 2: Electronics

Picture of Electronics
13, 3:09 PM.jpg
The next thing to consider is what electronics to use. Keep in mind price, size, speed and distance you want to travel on one charge. I was given my electronics for free so I did not have any options, but my bike has:
Motor- 500W 30A
Battery- 26Ah sealed lead acid
Speed Control- Alltrax 300A 24-48V
Throttle- Currie 0-5K ohm potentiometer thumb

Step 3: Mounting

Picture of Mounting
13, 3:09 PM.jpg
13, 3:09 PM.jpg
13, 3:09 PM.jpg
13, 3:09 PM.jpg
13, 3:09 PM.jpg
13, 3:09 PM.jpg
There is a few ways to mount electronics, you can bolt things on or weld usually. I used 1/8in thick L-bar from Ace Hardware. I measure out the batteries and welded 2 mounts that the batteries fit snugly into. I then made a similar mount for the motor with slotted holes drilled for the motor to change chain tension. Once the mounted were made, I measured and sanded the frame where they will be fitted. The final step I did was masking the frame off so I could paint over the unfinished metal components.
1-40 of 45Next »
michaelmonaghan (author) 4 months ago
http://www.instructables.com/id/Electric-Motorcycle
michaelmonaghan (author) 4 months ago
It really depends on what you want from them and your price range. The sla batteries are big and heavy, but they're also bulletproof compared to lithium which sometimes catch fire randomly (had it happen to me once) also keep in mind that a 20ah sla has less capacity than a 20ah lithium at a high discharge rate because they loose efficiently with anything over around 1amp. To make a bike feel lighter with sla batteries you should also place them as close to the front wheel as possible (that way it won't feel heavy when turning). I also made a 15hp pit bike with sla batteries and it works great as still has plenty of range.
Qrys134 months ago
I have an electric bike hub kit and I'm torn between lithium and agm sla for the batteries?

Wondering about your experience with sla? I'd rather do that than spen 500$+ on a lithium.
neklausk7 months ago

nice sandals man

michaelmonaghan (author) 1 year ago
I am currently working on an electric motorcycle that will be posted soon. Unlike the bike, it will have a purpose built machined out chromoly cradle frame for all the electronics. I'm still working out all the parts on AutoCad, but will start the fabrication here soon, so keep a look out for an electric dirt bike!
michaelmonaghan (author) 1 year ago
How do you post videos on here? I can do it this weekend. And yes, there are better electronic designs, but I got all the electronics for free from a friend.
Hallofo1 year ago
Awesome build! Have you had a chance to post a YouTube video of it in action?
keep up the great work. also if u could post wat it cost u and or linked to where u get all yr parts as well?
BTW: You write something about the motor that is AC? so, U use an inverter? or is a typo?
try using a dc to dc converter of the correct range.
jwall181581 year ago
Just curious about something. Couldn't you use the existing sprockets and take advantage of the gears and increase your speed?
That can be done but #1. you would need for the freewheel to be in the crank VS the rear wheel. These are available from Schwinn, (I have 2) but are not common. #2. To utilize the speeds that could be attained with more powerful motors & the multiple gear ratios, you would definitely need a bike with disc brakes AND suspension. Disc brake hubs can be purchased & your choice of rim size spoked up on them. #3 It would be necessary to run the motor through a primary chain to a jack-shaft to get the gearing in a range that would be usable and also to transfer the drive to the secondary chain to enable the use of the rear derailleur for the multiple ratios. Nothing all that hard or complicated, but still more to figure out than what has been done here.

Another thing to keep in mind is that most states limit the legal top speed of motorized bicycles to about 20MPH. Above that speed it may be considered (legally) a motorcycle & come under all the licensing & equipment rules that pertain to motorcycles.
Gelfling61 year ago
An alternative mount, I used to have a mini gas powered conversion engine (AKA Happy-Times, looked like a miniature motor cycle engine, 2-Cycle, and highly DANGEROUS! (manual clutch, pop-start, not to D.E.E.P. compliance standards)) that mounted to the wheel sprocket that was held through the spokes with a pair of neoprene rings and a split ring. The center of the main sprocket, fit snug against the center hub.
jtechian1 year ago
Nice work. One thing you should consider, Brakes. With the speed and weight increase, You might consider retrofitting some disc brake to this rather then the caliber ones. Also I would consider putting the batteries on a saddle rack behind the seat with the motor. Or distribute them front and back for balance. Keep at it, you are doing great.
BTW "caliper" unless you're talking about bullets or ebook software.
Yes sir officer !
It was understood what was meant.
-grin- I tried fitting my two 9AH batteries to the bottom part of the frame, just above the crank... it was a mountain bike so I used the drink bottle mountings and this kept the battery about as low as possible on the bike.

Downside was the motor was 250W which is the legal maximum here, and it barely pulled itself forward empty, let alone with a rider on board.

Its now a project for another day.
Were the batteries wired in series or parallel? As it sounds maybe you feed 12 volt to the 24 volt input.
Nope - I had 25.5V at the leads from the batteries to the controller. And the controller says "minimum voltage 20.5V"

So I wired a 24V DC power adaoter straight to the battery input leads and it was still useless, generating about 4-5 KG of pull at the wheel rim, measured with a spring balance and the wheel in the air.

I think 250W is just too little, or my motor or controller is naffed.
You said 24 volt adapter? Why did you put this in line, as the motor controller would be fine without it. Also did you use heavy enough wire from your battery to controller? This sounds from what you said about no power from the motor, it is not getting enough amperage from them batteries. Have you tried also a different set of batteries to test? Perhaps as a static test use 2 car batteries to temporarily test it. You should not need any kind of voltage limiter (adapter) for this, and even if you did have a limiter, it would have to pass 50 amp to work proper. I have a couple E-scooters with 250 watt motors and they pull my 200 pounds around fine :) Hope you get yours working.
kmpres1 year ago
Great job for a first attempt! I'm sure you'll find many ways of improving the design as you ride the bike and further the research. Others have noted the problem with the brakes and position of the batteries. I would add that the sharp corners of your angle-irons should be ground down as you don't want to ram a knee or other body part into them in a minor (or major) road mishap. Also, there is a way to really streamline the design with no batteries on the center bar, a much smaller speed controller, and almost invisible motor. For a motor and speed controller combo you could use a variety of devices normally used for model airplanes. They are very rugged, very strong for their size, can withstand 180 amps or more in bursts, and the speed controllers are only about 2"x4"x1" in size. The motors are only slightly larger than that. Total weight is maybe five pounds. Brushless motors give the best power to weight ratio and weigh far less than the big one you have behind the seat. Use a "servo tester" for the throttle (designs for building your own are online and very simple to make). If you use lithium batteries you can save lots of weight, get just as much range and power, and are so small they'll fit in a pouch under the seat instead of in the way of your knees up front. The only disadvantage is the cost. FYI: Some online e-bikes now have the motor built into the hub, either front or rear, and some people have installed motors in both wheels. Again, great job, and I hope you improve your design!
Can haz video?
I want to see it go!
michaelmonaghan (author) 1 year ago
There are 23Ah batteries (compared to my 26Ah that are almost half as wide. I'll be using these in my 15hp electric pit bike I'm making right now.
15hp motor? You mean 1.5 right? If your right @ 15hp, what motor is it? That's close to 10,000 watts and your batteries aren't gett'in it. ;)
pecefrogg1 year ago
Wicked cool instructable. Nice work dude, and thank you for sharing. Like someone else mentioned, I was crying for a video of this in action at the end. If you get the chance to post one, you'd make some of us nerds happy. Thanks again. Way cool.
criggie1 year ago
Can you add some video? Specifically, taking off from stopped without peddling, on a flat surface.
michaelmonaghan (author) 1 year ago
The batteries are not it the way of your knees at all, but because they are so wide you toes will hit while pedaling if your feet aren't in the right place. Lithium would be the way to go, but cost about 4x as much per amp hour.
michaelmonaghan (author) 1 year ago
The brakes are a bit weak, but they are sufficient enough to lock up if you squeeze hard enough (even the front). I do like the idea of disc brakes way more, but would have to weld caliper brackets and spoke a new hub.
michaelmonaghan (author) 1 year ago
The reason I mounted the batteries near the front is for balance. Just like on a motorcoss bike where 70-75% of the weight is on the front. It help it turn in faster and keeps the front wheel planted a bit more.
TSJWang1 year ago
I want to make this so badly.
Everyone in China has these. Q_Q
nothoro1 year ago
This is cool, Im diggin it :)
danny3xd1 year ago
Well done Micheal! Really cool.

Jtechian makes a great point. You really want good brakes, front and rear.

There is a product called a "ragjoint" that is used to attach a sprocket to the left side of a bicycle wheel. Or some specialty adapters so you can use any style of wheel or bike. https://www.google.com/search?newwindow=1&sclient=psy-ab&q=motorbicycle+ragjoint&oq=motorbicycle+ragjoint&gs_l=serp.3...2185.4713.1.6707.8.8.0.0.0.0.170.970.0j8.8.0....0...1c.1.27.serp..8.0.0.xKmu4N3n668&pbx=1&biw=1024&bih=432&dpr=1&cad=cbv&sei=kXlIUondPKXhygGJ7YDoDQ

Again, uber cool and thanks for posting
Would it be possible to use li-ion batteries rather than lead acid, so that you're knees would have space?
Checkout laserhacker's miniboost pack. The caps and lithium polymer are expensive and the specific caps he uses may not be available but it's an option.
patetic bike
bremus1 year ago
I'm glad you added that line about not needing a 300A controller. I'm pretty sure a you don't even need 100A. Something like 30-50A should do.
Nice! But aren't the batteries right where you knees need to be? O.o
michaelmonaghan (author) 1 year ago
And what's not easily removed?
astral_mage was responding to/expanding on your comment about zip-ties.

{A tip on answering questions/comments; there's a 'Reply' button at the top-right of each one. If you use that, the person gets notified of your response, and can respond back in the same way, if necessary.

Make sure, however, that any response to this is done via the Reply button on my comment, NOT the one at the top-right of your own...

So, astral_mage could have told you about their comment on zip-ties, rather than potentially being left thinking you were ignoring them. And a similar thing could be said for the other replies you've made.

Also, if you look throught the published Instructable, you will see that peoples' comments are repeated where they originally posted them - which is how I know astral_mage was commenting on.}
michaelmonaghan (author) 1 year ago
Yes, I'll look up the part # of what I put on it. And thank, I didn't see that mistake before!
1-40 of 45Next »