Raven issues - Redesign (Project on hold)

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.

Much of this weight and complication in the steering, chain and cable routing is due to my desire for the seats to be low to the ground. The low center of gravity does make the trike feel planted, even with a narrow-ish track (38"), but the complication it has caused is too much of a compromise for a real-world, everyday application.

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