In my last post, I cited the problems associated with the Raven - the long, wide tandem-seating electrified trike. Among the problems were weight, convoluted & unreliable chain routing, overly complicated steering, kingpin flex issues from side loads and traction problems on inclines with no passenger.

The design I had in mind to address these issues is indeed simpler. It uses a straight crossmember up front, more upright seating and simple chain routing, and it would certainly be much lighter. However, one issue that it did not address was usability. With a width of nearly 4 feet (1.22 meters), the sheer size of that trike and the resulting fairing/overall vehicle would have relegated it to the streets only. I would not have felt responsible bringing such a vehicle onto bike paths, and I did not want to create something that I could only use on roads shared with cars.

I came across a short article by "The Left-Handed Cyclist" on their blog that highlighted a couple of the challenges facing vehicles such as the one I'm designing. That article can be read here. In it, they go through a few examples of vehicles past that were based on electrified tricycles, with fairings, that were designed to bridge the gap between bicycles and cars. One such issue is trying to use a low-speed (at or below 30 mph (48 kph) crusing speed on a roadway shared with cars. This speed (with a large enough vehicle, such as an ELF or PEBL velomobile, or the one I was designing) can lead to traffic backups as motorists are forced to pass in a passing lane. While this may not seem like an issue on paper, I know from experience that driving a vehicle slowly enough for motorists around you to need to pass constantly is a stressful experience for the one operating the slow-moving vehicle. People are often angry and passing aggressively, and therefore dangerously, when they feel their movement is being impeded. This is a very unpleasant experience, and not one I want to have whenever I am running errands around town, so I've decided that it is critically important for this vehicle to easily fit on bike paths (and bike lanes) responsibly.

So, what does this mean for the trike?

It means that things need to get smaller. Much smaller. So, my focus lately has been on packaging. How can I create something that's easy and appropriate to use alone, but can still carry plenty of cargo or a passenger if the need arises? I basically want to create a bakfiets (box bike) - but it needs to be able to have a fairing mount to it so that the operator - not just the cargo/passenger(s) - can be protected from the elements.

The more I've thought about this problem, the more I begin to look to delta tricycles. Delta tricycles offer a few unique advantages. One of those is having a large open space for cargo between the rear wheels. This is a fantastic place to put a lot of weight, because the more weight you have, the better your stability gets. To illustrate this point, see the figure below. All things being the same - wheelbase, track width and cargo area - you can see that the area within the tire contact patch triangle is far greater with the delta design. With a tadpole trike, cargo areas are beside, in front of and above the rear wheel. This is a very awkward way to carry cargo, as most weight placed around the rear wheel (other than that placed in front of it) serves to fight the inherent stability of tadpole layouts.

Complex Design
Arguably, one of the most frustrating things to deal with for any end-user of a product is over-complicated, unintuitive design. Standard bicycles are one of the simplest machines humanity has created, yet I would argue that the utility of bicycles cannot be overstated. Anybody with a little mechanical aptitude (and perhaps some Youtubing) can fix just about anything on a normal bicycle.

As soon as one starts to introduce steering linkages, suspension, differentials and jackshafts into a bicycle design, the vehicle starts to become more of, well... a vehicle. I want to make sure that this trike is not only easy to build, but easy and inexpensive to maintain, work on and live with.

To that end, I believe I've found the simplest, most streamlined way to create a cargo trike in a small package that's simple in design and does not require any crazy transmission or steering linkages, is intended for use on bicycle paths, can fit through a normal doorway, sits low to the ground for stability and has a wheelbase that's nearly 2-feet shorter than your typical box bike, while being able to carry the same cargo. As you can probably guess, it's a delta design, but the drivetrain is simpler than you may expect.

I'm very excited to share progress pictures once this build is underway!

Since I last posted, I have gotten the seatbacks mounted, chains routed and brakes hooked up, and I have taken the Raven for a few test rides on pavement and dirt roads.

The test rides have taught me four things.

1. The weight of this build is starting to become problematic. I have not yet weighed it, but I have calculated the frame weight alone (without seats, wheels/tires, motor, battery, brakes, chains, etc.) to be nearly 50 lbs (22 kg). Getting myself to stop takes longer than I find safe, and that's without e-bike components, a passenger, a body, and cargo.
2. The chain routing is both overcomplicated and ineffective in providing stiff & reliable power transfer to the rear wheel. Pedaling feels rubbery due to idlers getting slightly deflected under load, this effect is multiplied by the number of power-side idlers in use (currently 4). On top of this, the chain can still sometimes hop off track on rough dirt roads, so additional chain tubing is necessary.
3. The front steering knuckles lack the required rigidity for the lateral forces placed on a 26 x 3.0" wheel, and because of this, the disc brakes rub in turns - unless they are adjusted such that their pad clearance is too great to provide a good feel at the brake lever.
4. The turning circle is not great because the wheelbase is over 8 feet (2.44 m). 
5. The distance to the rear wheel is problematic when there is only one rider. On steep dirt roads, I simply do not get enough traction to keep my momentum up and I stall out.

So, I have redesigned the main frame. The design is much, much simpler. It uses two main tubes, a straight crossmember, simple underseat (or overseat) steering design with two tie rods instead of three, utilizes aluminum seatback support tubes, single upright seat supports and now all power is routed to the rear wheel through the mid drive, which reduces the number of chains required, eliminates the need for a special tandem shift cable and should also allow chain routing to only require one power-side idler as opposed to 4. Also, the wheelbase has been reduced by over 2 FEET (609mm), which will greatly improve the turning radius.

The compromise here is that the seats are about 6" higher off the ground than the previous design. To counteract this higher center of gravity, I will likely increase the track width by as little as 5" and possibly as much as 10", for an overall width around 48". The seats are also 10° steeper, putting them at 55° rather than 45°. This puts the occupants in a position more similar to driving than before. I am also going to have the bottom bracket a bit lower to the ground so that visibility and chain line are optimized when it comes time to build the shell.

​If it's not already clear to my readers, all of these changes basically mean starting over. The seats and tie rods will be re-used, but the rest will be cut apart and the usable pieces will be saved to be used as scrap parts for the next build and future projects. This is, unfortunately, one of the realities of prototyping experimental vehicles. This is not the end, but unfortunately it is enough of a setback that the project needs to be put on hold. Partially because of financial reasons, but also because by September 1st, my Fiancé and I will have moved to Boston for her postdoc position she was offered at MIT. Should we find suitable arrangements including a garage for me to work from, this build will resume part-time with the new, simpler redesign around then. Until then, I need to begin working again, packing up my tools and parts, and preparing to move our lives a 29-hour drive away.

If you know of any bicycle shops in Cambridge looking for an experienced mechanic to wrench in and/or manage a service department, I would greatly appreciate the introduction! Until then, I will post any updates here that I think you all will find entertaining, and I'll get back to work on this project as soon as I can.

- Chase

Last Thursday, I finally got the frame rolling! In the process, I tweaked my plans just a bit in order to simplify the build process and to help ensure others could follow along easily and reliably. So far, the build has gone very smoothly and I've eliminated steps I've had to do in previous builds that I found to be overcomplicated or required too much "guesstimation." 

Working from my rough draft of my plans, I've started cutting tubes and laying out the build! I have everything cut for the main frame. Next time in the shop, I'll tack up both sides of the frame, link them together and possibly start on the kingpins! 

I'm very pleased to say that the plans made the build thus far a total breeze! I recorded a lot of video today as well. Some of it will be used for my YouTube channel, and some of it may go towards making more detailed videos for Patreon. 

Stay tuned as I believe this will come together quickly! Would you have any interest in building a machine like this from plans? How about a single-seat version of it? Let me know in the comments!

When I first ordered parts for this build, I ordered a 1200-watt rear wheel hub motor kit for simplicity. I chose direct-drive over geared because I wanted to be able to one day add regenerative braking, as well as a reverse function.

Since I received my kit, I've been reading up on the forum Endless-Sphere. The conclusion I've come to is that my direct drive motor may get bogged down with the weight of two people plus the chassis.

Some people would get around this problem by swapping the direct drive motor out for a geared one, but that would mean sacrificing the ability to have regenerative braking and reverse function in the future, so I opted to make my 1200-watt direct-drive hub motor into a mid drive, connected to the rear wheel at a fixed gear ratio of about 0.57:1 (16t at the motor to 28t at the wheel). To achieve this I'm using cogs on both the motor and the wheel that bolt onto the disc brake mounts. This means that in the future I can still have regenerative braking, and also drive the rear wheel in reverse! On top of that, the other benefit of a direct-drive motor is superior reliability as there is only one moving part!

In future full-suspension models (eventually), this same setup will allow for superior rear suspension performance by massively reducing the amount of unsprung weight!

So, today I de-laced the hub motor and then built up the fat tire rear rim onto a standard disc brake hub. Now I can get into the meat of this project - the build of the main frame! I have some modification to do to my welding table tomorrow to allow me to clamp down anywhere on the table, but once that's done I will be getting started on all the cuts and tacking together the two main portions of the frame. I promise I will post lots of photos! Until then, enjoy this taste of the future "hub motor as mid drive" setup!