November 2nd, 2010 by peter
October 29th, 2010 by peter
The major question when building the 72 volt folding electric bike was: will the geared hub motor survive 1500 watts in the long term?
The Bafang geared hub motor contains 3 nylon gears… yes, plastic. Run within it’s limits, those gears should be fine. But this motor was being run at double the normal voltage.
To hopefully avoid these problems, a metal gear was installed in our motor.
Today, after about a year of use, I decided to open up the motor and assess the conditions inside. I can report back that everything looks beautiful inside!
October 27th, 2010 by peter
|While on vacation in Amsterdam, Vienna, Antalya (Turkey) and Istanbul, I was on the lookout for bicycles, electric and pedal only. Surprisingly, while Amsterdam was certainly pedal bicycle central, it was Antalya in southern Turkey that had the most “ebikes” in the form of electric scooters. It looked like about a third of the scooters on the road were electric, and almost all of these were this “Maxi-scooter” model. I haven’t been able to find it on line. Amsterdam also had a lot of cargo bikes and trikes, far more than the USA. Photos can be found below.||
August 7th, 2010 by peter
We are proud to release a video about the folding bicycle prototype I’ve been riding this past year. It’s been by far the best bike yet. Not only does it have ridiculous amounts of power, but the weight is finally below that magic threshold where it get too difficult to lift– roughly 45lbs. It was ridden through San Jose’s Indian summer heat and the pouring rain of winter without a single hiccup (hint: the electronics are wrapped with rubber).
We’re looking at building the next iteration, where we’d like to tame the top speed but improve hill climbing performance, a handy feature in San Francisco. Stay tuned!
Without further ado, here is the video (you can also watch it directly at Youtube here in full 1080p HD):
We had a lot of fun filming this video and spent many hours editing. Thanks to Mike Steczo also for the sound track! Also dear readers, note the homage to Jeremy Clarkson near the beginning…
May 14th, 2010 by peter
I’ve been looking at a lot of 1950s advertising for design cues for posters. In regards to technology, it seems that electric toasters and refrigerators were the craze back then– a little difficult to adapt to bicycle.
However, the design elements cross over easily enough. The fonts used were quite different from today– some fancy sans fonts and hand painted ones. There were often rounded geometric shapes such as elllipses and boomerangs. And of course, the colors. Here are a few handy links for palettes:
And finally, a handy CYMK to RGB color value converter.
Without further ado, here’s a poster created using the above resources.
April 29th, 2010 by peter
So with all the difficulties of the original RC motor driven bicycle concept (particularly the clearances to make the transmission work), we decided to take a simpler approach for the time being: use a tiny driven wheel. A small wheel needs to spin faster for a vehicle to reach the same speeds as a larger wheel, so the high RPMs of the RC motor becomes an advantage rather than a hindrance when the wheel it’s attached to is very small. Instead of building a whole new frame from the start, the fastest solution was to reuse an existing vehicle…
The stars aligned in this case. Earlier, Eric T. graciously donated a red Chinese stand up scooter and Brian T donated some scooter motors with belts and cogs. Todd D. had also donated a Razor E150 scooter earlier, but the frame was too small for an adult and it lacked pneumatic tires. What does an EV with solid rubber tires feel like at 15mph? Once my teeth stopped rattling I had the good sense to throw the scooter in the back of the garage until I could find a use for it.
Well, that time finally came: many of the parts were interchangeable and the end result was all the parts (besides electronics and a motor mount) to put together one working scooter.
I used Ben’s TIG welder to make a motor mount out of aluminum and then modified the scooter frame to accept it.
The performance was tested using a sensorless ebike controller and it was nothing to write home about. Hmm.
Now, RC motors lack the sensors ebike controllers require for reliable low speed operation. RC airplanes don’t need low speed torque, so the sensors (which can often be problematic) aren’t built into the motors. Some larger RC motors can be modified to accept the sensors, but this wasn’t the case with our motor.
We tested a hypothesis: that external mounting might be a feasible solution. It worked! We attached the sensors using blue tape on a work bench.
So Ben used his CNC mill to build an external mounting. The positioning of the sensors is critical, so the holder has the ability to be adjusted, much like an automotive distributor, for proper placement.
Now it was time for some on road testing…
Holy torque! The scooter will simply throw the rider off without gentle throttle from a stop. The original Ecrazyman controller had some issue above 75% throttle, however, full throttle is only necessary for a higher speed. Top speed: not too much.
The problem with the Ecrazyman controller has been reported elsewhere: the power suddenly cuts out above 75% throttle until the throttle is rotated to totally off. Strange.
I ordered another completely different controller to test whether it is simply the fault of the controller design.
April 29th, 2010 by peter
You might wonder what’s going on in the above photo.
Answer: the serial hybrid tandem is being upgraded! I wanted to lighten the generator apparatus and remove the chain drive.
First, to save weight, I decided to try a smaller motor. However, I found that very few motors actually fit in between a set of cranks. The original MY1018 and several brushless motors such as the Kollmorgen fit, but just about everything else doesn’t. The brushless motors require pretty hefty gear ratios. The MY1018 comes with a built in 9:1 gear reduction.
Many power tools also have built in reduction. Angle grinders have heavy duty transmissions which also contain a right angle gearbox, but they are almost all AC powered and AC motors do not make good generators.
Battery operated drills use DC motors and have transmissions. There are also right angle drills and attachments available. In fact, drills are often used in building robots for propulsion.
So if a 120lb combat robot can use a couple of drill motors in the ring, maybe a human can pedal one as a generator?
I picked up the Black and Decker drill off Craigslist for $10.
Now, to get rid of the chain, I took the belt drive off a go kart. The sprocket was too tall, so I chopped it up and then epoxied it back together again. I had to cut an adapter plate to attach the sprocket to a bicycle crank. The plate was brazed onto the crank.
Next up… time to mount it to the bike!
March 23rd, 2010 by peter
I remember watching Forbidden Planet in college. That was a decent movie, a bit silly now (especially the music) but it’s still well rated on imdb. Many of its other 50′s sci-fi B-movie brethren never fared so well. While the movies were bad… there were also the posters.
All the absurdity of these hastily made, far fetched movies summarized in one extremely loud poster– monsters, screaming women, military men, and ludicrous speech bubbles. I guess it was hard to make a scary poster back then because usually some text in the poster had to explain just how scary the movie was.
Well, here’s our own scary thought: electric transportation.
December 21st, 2009 by peter
While initial work on converting a bicycle to use a high speed motor went well, little details came back to haunt the prototype.
- Although a great amount of attention had been given to making sure the go kart sprocket that was bolted to the Sturmey Archer hub didn’t cause chain interference problems and the newly built up wheel fit in between standard drop outs, one detail was overlooked: adding a sprocket on the drive side caused the rear wheel to be offset to the left just enough that the axle did not protrude sufficiently from the drive side drop out to thread a nut. Gary on Endless Sphere forums who did a similar build earlier in 2009 used a steel framed bicycle. Our bike uses a lighter aluminum frame. Aluminum is less dense than steel and so the drop outs are about three times thicker. Oops.
- The magnets in the RC motor are very strong and picked up metal shavings from the shop. These shavings got into the gap between the outer rotating magnets and inner stator. To avoid damage to the motor, the motor was disassembled and cleaned using duct tape and fine tweezers. It is advisable that if the motor will be stored in the same room as metal working equipment such as grinders and mills that all openings be taped off or the motor be stored in a sealed box or bag. Wash your hands before handling it. These magnets are STRONG!
- The sensorless Shenzen Sucteam controller was damaged yet again when applying full throttle from a stop. This is the third failure so far. The usual failure mode is that a MOSFET (an electronic switch) on one of the three phases fails and gets stuck on or off. This manifests itself as a stuttering when the motor turns. The 3 phases are arranged around the hub so that each phase covers 120 degrees of the hub. The controller should turn the phases on and off to make the wheel rotate, but instead a phase is stuck on or off and either the motor shakes back and forth or has no power in part of its rotation. The Shenzen Sucteam sensored controllers have been rock solid so far, but RC motor’s don’t come with sensor. There are only two solutions: a) find a more reliable controller or b) attach sensors to the motor.
September 24th, 2009 by peter
Most electric bicycles are built on an existing frame or a slightly modified one (usually to provide mounting points for the battery and motor). This is the approach we took with the compact tandem.
The problems with using existing bicycle frames for electric bicycles:
- No convenient mounting for the motor or batteries
- Motor and electronics exposed to the elements
- The medium quality frames are not as overbuilt as the cheap ones and aren’t up to the stresses of high performance ebikes, relegating most home builders to using very poorly built department store bikes
The lack of convenient mounting for both motor and batteries comes down to the frame being essentially two dimensional. This problem is especially acute for the motor. When a motor is attached to a round pipe, the torque of pulling a chain tends to rotate it around the pipe, loosening the chain and causing all sorts of problems. This can be overcome by mounting the motor in a location where there is a 3rd attachment point available. Three points are needed for stability– imagine a stool for example. Bicycles have two such locations, the triangle made by the chain and seat stays and seat tube or in the main triangle between the riders legs. The rear end mounting exposes the motor to the abuse and the chain and seat stays are usually not parallel to the wheel, but rather at an angle, making mounting somewhat obnoxious. The in between the leg mounting is kind of scary because it’s quite easy to stick your leg in a spinning motor’s chain. The batteries also have nowhere good to go except behind the seat, which is why so many Chinese ebikes have the rear end stretched out. Not really the ideal position because their also tend to mount the motor on the rear, leading to a very unbalanced machine.Let’s look at the other end of the two wheel spectrum: motorcycles. Motorcycles have frames that are roughly like two bicycle frames with cross pieces holding them together. This provides a convenient place to mount the gas tank and motor, which are both much heavier than on an electric bicycle (and more powerful). The frames are also much stronger thanks to this design. But, especially when built of big thick steel tubing, they’re heavy. Since they have humongous gas motors, it doesn’t matter very much. Most motorcycles weigh over 300 lbs. Forget picking it up. At that weight, you just want something that can be heaved upright after it falls over. I don’t want a bike that weighs that much, do you?
Since most electric bikes are already too heavy to casually lift (about the same weight as a bag of cement-50+lbs), throwing a bit more metal onto the frame shouldn’t really make any difference.
Also, most bicycles are of the upright diamond frame type, where the pedals are located in the middle of the frame. The width of the frame is limited by the bottom bracket width and the spacing between the pedals (there’s actually evidence that widening the distance between the pedals is good for your knees– search Google for Q-factor). On a recumbent, however, there is much more flexibility since the pedals are located at the front of the bicycle and we have room to play with on the rest of the frame.
So how about a motorcycle style frame but with the tubing sized for bicycles? It’ll add a bit of weight, but hopefully make up for this deficiency with the benefits of secure storage and better weight distribution. And who knows, maybe if it’s built out of aluminum and the rest of the parts are half decent, it’ll actually weigh less than many cheapo ebikes. Let’s rock and roll!