Electric Mountain Bike
This is the second of the two electric bicycles I have made. The first was thrown together for a friend of mine on a very limited budget and used whatever we had lying around. It worked fine but looks like something you would see on ThereIFixedIt.com (there are links to pictures of this bike at the bottom of the page). For my own bike I wanted a much cleaner look. So I designed a frame from scratch to hold the components I wanted. Full suspension was important to me, since experience from the first bike showed that bumps were uncomfortable on a bike with an extra 100lbs on it. I also wanted off-road capability and more power than any sane person would want on a bike. This bike met all my expectations.
I limited the top speed to ~30MPH by design, since I didn't really want to go much faster on a bike-style frame(I have a yamaha FZ-1 for that). The low gearing and large motor leads to insane torque. I had to set the current limit in the Alltrax controller to half its max value, otherwise it was impossible to keep the front wheel on the ground. As it is, you still have to be careful taking off, it will throw you over backward if you peg the throttle from a standstill. Acceleration is limited by the friction between the rear wheel and the ground, you can lean forward to keep the front down, but the reduced load on the rear means that the drive wheel will slip, even on dry pavement.
Unfortunately, I built this bike over a couple of years, and was not really thinking about putting it up on a webpage. Therefore, there are not many pictures of the construction process. I am currently in the middle of tearing the bike down to components to get the frame powder coated. I will take pictures of all the parts I can and post them, but some things, like the main frame and rear swing arm are welded together. I also have CAD models and drawings of all the parts. I'll post them as well, but there are a lot of them and converting them to pictures will take a while.
You can see the bike in action on youtube: video1 and video2. You may notice in the second video that I'm not very good at off-road riding. The bike is capable of much more, but as it is I broke my elbow in a wreck that was edited out of the video, so I can't really show off with cool jumps or other tricks.
| Attachment | Size |
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| e-bike1.jpg | 599.16 KB |
| e-bike1_controller.jpg | 595.54 KB |
| e-bike1_motor.jpg | 688.59 KB |
| e-bike1_top.jpg | 532.32 KB |
| e-bike1_transmission.jpg | 606.85 KB |
Comments
#1 Electric Bike
Hey Jenn! I finally got a chance to look at your webpage (I'm in Florence with honest-to-god internet right now). Awesome! As ever, I'm super-impressed!
#2 Gooooood the power
Gooooood the power
#3 Fantastic Project
I'm amazed at this thing's capabilities and would love to see a full DIY write-up, it's definitely worth tinkering with and building one on my own.
Shared on my web-site www.dmanlt.com
Keep the creativity flowing.
Don
#4 Great
That's a serious piece of work - solid as a rock and overbuilt to last. The motor size would be overkill for city riding (6 HP continuous, wow), but out in the mountains no doubt it's more than welcome. Thanks for the tour of the kinds of parts that are out there now for serious efforts!
#5 "more power than any sane person would want"
I have to agree--you're crazy! Looks like tremendous fun though. I am WAY impressed that you built this, and I am astonished at the acceleration you have achieved. Wow!
#6 Nice Bike
Nice work Jennifer.
Whats the range of your bike with the batteries you have used and could you incorporate pedals into the design to extend the range of the batteries?
#7 re: Fork
Thanks. I'll look into it.
#8 re: fork
The VF2 has no external preload adjustments. It does have an external compression adjustment on the left fork leg, probably on the top. By turning that knob clockwise you will close of internal oil ports making it more difficult for the fork to cycle through it's travel. The spring won't be any harder, but it will control the fork dive better. The right adjuster is for rebound. If you still need a stiffer fork you will need to replace the springs, one in each leg with a stiffer version.
#9 re: Fork
it says 888 VF2. there is a link to the product page at Marzocci on my "frame" page under electric bike.
#10 Fork
What fork are you running? It appears to be an 888, but it should say somewhere on the legs what model. Specifically what damping platform, RC3, RCV, etc. Some of Marzocchi's forks use a mechanical spring preload system, others use air preload so you may be able to use those to stiffen it up. Otherwise you will need to replace the coil spring in the leg with a stiffer spring.
#11 Electric Bike
Looks like fun in the videos. More power than I could handle.
#12 Thanks to all the well-wishers
A lot of people have wished me well about my elbow. Just so people know, this happened in November 2009. I am perfectly fine now. It was a very minor radial-head fracture.
#13 Posted about your e-mtb
Hi Jenn,
We posted about your e-mtb. Check it out on www.bikerumor.com.
Maybe you can get your hands on some protective gear for the next time you get back on the bike! Hope your elbow heals well.
Cheers,
Kristibee
#14 @ Cost of your e-bike build?
I spent about $4k on parts and materials. about 1k on the mountain bike parts, 1k on motor/transmission, 1.2k on batteries, and the rest on metal, bolts and misc. I did look into hub motors, but I found that the mars motor gave a better power/weight ratio, and I wanted to be able to adjust the drive ratio. I'm not sure what the absolute range is with the batteries I have. I have never run them all the way down. Instead of regen braking, I found that simple coasting is a good way to use energy, and much easier to implement.
#15 Cost of your e-bike build?
Wow, you read my mind. I have been wanting to do exactly what you did but haven't had the time. I agree full suspension is the only way to go with that type of build. What was the cost of your bike: motor, batteries and components? Would love to know more about the R&D that led to your part selection. Did you look into hub motors? I was leaning in that direction. Also how long does the charge last for your current set up? I'm a big guy at 250 pounds so I need a strong motor to pull me around. Do you have regenerative breaking built into that design? Again, great job! Gives me a few good ideas and the direction to go in to build my own.
#16 pedal regeneration...
This is an AWESOME project, I'm sure I don't have to tell you that... Great work!
While I'm a road biker (I love speed) and would love this bike.
I was wondering based on your project how easy it might be to adapt to a road bike and possibly adding a pedal based regeneration system.... so when I am peddling along I charge up the battery for those nasty hill climbs? :)
Again, Great Work!
#17 I love it!
I love it soo much, I would buy it off you if you were interested in selling it!!!
#18 Marzocchi shocks
Hey, Jennifer, sweet work on the bike. Wish I had the know-how and time to do that. As for your shocks, I *think* Marzocchis use elastomers. I had one once back in Italy and as I recall you could just unscrew the top retaining knobs, separate the top from the shock tubes, and put any combination of elastomer bumpers in there you want. Sounds like you need something stiffer.
But after visiting here: www.marzocchi.com/spa/mtb/ I see they may have moved forward with some newer technologies.
Anyhoo, cool projects!
#19 @ Cool
I don't notice anything during acceleration. the rear suspension is pretty stiff. Actually I would love some expert on Marzocchi forks to tell me how to stiffen up the front. It bottoms out far too often on even small jumps.
#20 @ cool project, but i looked at
I just bought some parts at thunderstruck. the bike design is custom.
#21 Cool
Wow, it must have been tough welding that frame and keeping everything aligned. Your suspension design threw me off too.. I was thinking you would suffer terrible pedal bob until I remembered you're not pedaling. :D
When you accelerate, does it feel like it squats?
#22 cool project, but i looked at
cool project, but i looked at thinderstruck, etc.. ...
wasn't your bike + all the e-stuff really really wow expensive?
nice e bikes are available for < 4k€:
http://elmoto.com/en/galerie/
#23 Well done
Sorry to hear you got hurt. This is an interesting and very successful build. You did a great job, I would love to have one of these for my short commute to work (4 blocks, I'm lazy). Keep up the great work!