The steering design is done. I know I've said this before but I have to make a decision and this is the result. It's not as "ultimate" as I'd hoped but it should work quite well.
At top left is a side view showing how the frame will be modified. Below that is the new rake angle of the forks and the new locations for the coilover shocks, which provides more room for the radiator. At bottom left is a side view of the steering assembly, showing how it works with the modified frame. Below this text is an overhead view of the steering assembly, showing the relationship of the front triple-clamps and handlebar clamps with the pivot assembly. The previous pivot assembly stuck out too far from the frame, but this smaller version is tucked closer to the engine, plus will be hidden behind the bodywork covering the coilover shocks.
It's impossible (at least for me) to optimize every aspect of the steering as it relates to the front suspension, so in some ways this design is a compromise. However, it should work pretty well to turn the forks without any binding or bump steer. I could keep trying different combinations and layouts, but it's time to start building and see how it works in real life.
A major change is using a Honda Sabre VF700S (shown at right) instead of the existing Interceptor in order to use a driveshaft instead of a chain and sprockets. The Sabre has the same V4 engine, but the motorcycle itself has a round tube frame which is not nearly as strong as the Interceptor's square tube frame. Because of this, the Sabre's engine and drivetrain will be adapted to work with my already-modified frame. Sure, it'll take some time but the long-term benefits will be worth the extra effort.
Spring has arrived in the Rocky Mountains and summer is on it's way, which means a return to the construction phase of ProjectVF. Of course, during the long, frigid winter I had ample time to try various suspension, steering and frame combinations. I already designed a new suspension but needed a better way to steer. One thing leads to another and soon I was modifying the frame to work with a new steering layout, as shown below. With any luck these will be the final changes.
At left is an exploded diagram of the Sabre's swingarm and driveshaft assembly, scanned from the Honda shop manual. The swingarm pivots are aligned with the center of the driveshaft which prevents any geometry changes during suspension movement. A chain, by contrast, will become tighter or looser when the swingarm moves up or down. A second benefit is the swingarm being totally enclosed, thus sealed from any dirt or debris, plus it doesn't need to be frequently lubricated like a chain. The final benefit is that it'll take up less space in my design than a chain would.
As I said above, there's going to be some redesigning and adaptation, but this represents a big step forward and will result in a better, more-practical vehicle. The next few months will see big progress, such as the new front suspension, and my goal is another rolling chassis by late for full-scale tests. Keep your fingers crossed and come back often to see how it's going.