Cargo Bike First Take

One of the benefits of the Bellcycles design is that the rear pivot allows the rear section of the cycle to be easily swapped out and as long as the height of the pivot remains the same, the cycle rides pretty much the same. 

 

So if you are mostly a bicycle commuter but occasionally you need to haul some heavy boxes you could just swap out the rear section of your bike with two bolts and bolt on a cargo back. In this case, I just used a 2x6 piece of wood with an old bmx fork and two small wheels. 

 

The worlds longest bicycle is 117ft says the Guinness Book of Records. Thats not really that long. I could build a light 120 foot beam ( wood? Foam/Fiberglass? Carbon Fiber Tube?) and bolt it on the end.

V1.15 Rear Pivot

Where should the rear pivot on the cycle be? From v0.5B when I stuck a office chair caster wheel on the cycle the pivot was very close to the rear wheel. But in later version to simplify the design I moved the pivot towards the front.

 

The results? Its more maneuverable. You can perform tight tight turns. Its more fun!! But its also a little more challenging at low speeds. I think for the first version to release, I will go with the pivot towards the front but possibly with the possibility of the back pivot. 

V1.10 Waterjet

Version v1.0 showed me that the idea of the flat cut parts bolted together with tubes worked. But the process of cutting and drilling everything was not scalable. Enter the waterjet cutter. I went to BigBlueSaw.com and uploaded the parts. I also made a few changes to make the cycle simpler with fewer parts. I also added back in a connection to bring the handlebars under the seat as in earlier versions.

The waterjet parts were not perfect but much easier to work with then raw material. In further versions widening the diameter of the holes by a small amount gave enough clearance to make assembly simple. The parts do require holes drilled and tapped in some of the parts sides for the pinch bolts, but in a few hours a complete cycle is ready. 

V1.0 How would you manufacture this thing?

Early 2017, I am riding the bellcycle around the neighborhood and occasionally from Harlem to the Flatiron. Most New Yorkers just ignore me. But for those bicyclists or people who look closely they yell some variant of "Where can I get that" or "What the f*&X is that." 

My thoughts on manufacturing were

  1. I could have visited a boutique local bicycle frame shop and had them TIG weld a custom frame or even perhaps build the entire cycle from my rough plans.  This is expensive at probably a few hundred dollars per cycle. 
  2. I could try going overseas and working with existing bicycle manufacturers to make a more production ready prototype. This has other issues which I will address in another post.
  3. Growing up in NYC I always wanted to build my own bike from scratch, frame and all. I had finally done that. But it wasn't easy. You can buy a kit and assemble a radio, computer etc from scratch, why not a bicycle? What would a cycle kit look like? Sure, you can buy a frame online and assemble, but what if you want to go further and assemble everything?

I downloaded Fusion360 from Autodesk and jumped in. Many modern motorcycles have an interesting construction of their front fork/ triple tree in which the forks are bolted between usually two aluminum members with the forks held via pinch bolts. As in below. 

So I designed a version of the bellcycle in which the parts are made up of tubes( aluminum, steel, carbon fiber, whatever) are held together by a series of plates with pinch bolts. 

 

V1.0

V1.0

Without building it, the benefits seemed to be

  1. Mostly flat stock
  2. Can be easily assembled with just a allen wrench
  3. Should be cheaper at smaller volumes if there is no need for welding factories etc
  4. Modular allowing for different handlebars, positions, angles, tandems, cargo cycles etc. 

I ordered the metal from onlinemetals.com. Used my hacksaw to cut out the shapes and a drill press with a variety of bits to drill out the required holes. Drilling a 30mm hole through a chunk of aluminum is not easy!! When building the design it became obvious the improvements in the design that were needed to reduce holes, angles, etc. 

 

 

 

It works. It is fun to ride. 

 

V0.99 Gearing - 2017

Over the course of the past few prototypes I tried a lot of versions of the gearing. 

For instance in this mess above you can see a front derailleur mounted so as to switch between the three gears on the pedal chainring. All the solutions were heavy and messy. 

I decided to worry about the gearing later and focus on a less expensive, lighter and simpler solution. I realized that with jockey wheels, commonly used on rear derailleur's, I could route a simple loop of chain around all the required sprockets. 

 

V0.75 Tandem Time- 2016

What would a tandem cycle with this design look like? I decided to return to the brazing torch and try it out. In the process I wanted to check some assumptions.

  • Is the rear pivot/second degree of freedom really that important?
  • What if the cycle is heavier with weight on the back?

 

 

First I tested with no pivot between the two wheels and no spring. It was as before, rideable but just. Not fun.

Then I cut the bars and added a pivot in. Rideable and fun. 

 

Screen Shot 2017-09-19 at 6.27.45 PM.png

I did find a picture of what looks like a similarish design for a tandem penny farthing. However, as far as I can see there is no rear pivot. So riding this was probably a little challenging. 

V0.75B handlebar experiments, improvements, etc - 2016

What if the handlebars were higher?

What if the handlebars were in front?

What if the handlebars were in back and in front at the same time?

IMG_3213.JPG

There were other iterations. Most were bad. The longer the handlebars the more flexibility in the steering which makes steering the bike like pulling on strings. However, the handlebars in front was actually nice, so lets keep that going forward. 

Another change was that with the seat brazed onto the front of the cycle the weight was too far forward and the steering felt inaccurate. So I moved the seat inline with the handlebars on a bearing and fixed the rotation to the frame.

 

The result of all these improvements? Getting somewhere. The cycle is fun to ride. 

 

V0.5B Something is taking shape - 2015-2016

After the brazing of the frame the cycle was definitely interesting. But I felt that I had basically created the penny farthing https://en.wikipedia.org/wiki/Penny-farthing . And furthermore I could see why it is a relic of history, it is hard to ride. Specifically the steering + pedaling is just not as easy as a "regular" bicycle. Its not easier and its definitely not fun. 

So I bought a caster wheel that you would find on an office chair and swapped that for the back wheel.

 

So simple. Well at first it didnt work because with 2 degrees of freedom, the rear end would just pivot to one side and stay there throwing you off the bike. But by adding a spring between the front wheel and the main frame of the bike the spring can absorb the pedal stroke.

The idea of the second degree of freedom in the rear wheel and the spring is that the dynamics of the cycle need some way of absorbing the lateral force of the pedal stroke without requiring the steering to constantly be fighting the pedals. As an example, the user pushes on the right pedal. Some component of the force is in the plane of the wheel and turns the crank propelling the vehicle forward. The other component is perpendicular to the plane of the front wheel and tries to turn the front wheel counter clockwise. With the caster wheel in the back coupled with the spring, when you push the pedals the rear section of the cycle will deflect towards the left on a right pedal stroke. 

Well the office chair was a solid piece of plastic and made a racket. But by swapping it out for a pneumatic wheel the results were fun. There was work todo. At faster speeds there was instability. The frame had too much flex which could fight stability. But it was no longer a pain to ride, it was fun. 

TODO: Improve on this idea