Suspension concerns

I have a couple of concerns about this suspension geometry.

I understand it, and see how everything connects and moves, but my concern is about the rebound and dampening. The wheels are obviously able to move up and down as well as tilt on the a-arms, but with the shocks hooked to each other it would seem like the suspension travel of one side is dependent on the other side being planted. This is disconcerting. The last thing you need on a leaning vehicle is wonky suspension. Sure this arrangement tilts just fine, but what happens when you’re deep in a lean and run over a pothole? Does the vehicle shoot one direction or another? It’s enough of an issue in traditional 2-wheel vehicles. So this is something I’ve got to get figured out during the prototyping process.

My prototype roadmap is as follows: Final concept » small-scale component prototyping » small-scale radio controlled, fully-functional prototype built mostly from R/C car components » large-scale prototype built from bicycle components and driven either by pedal power, electrics, or moped engine » full-scale chassis prototype with full drivetrain » polished full-scale vehicle made from chassis prototype and finalized.

Last night I swung by R/C Car Kings, a descriptively named shop in Burnsville, MN just up the road from my apartment. They’ve got every R/C car component known to man or beast in there. Fantastic stuff. I’m only just starting to understand the ins and outs of automotive suspension and as I’ve said before, I really want to engineer as few components for this vehicle as possible. Thankfully John, their resident suspension engineer, was on hand to walk me through my options. He expressed the same concerns I have about the pivoting, linked suspension on the design I’ve been referencing. He walked me through the different types of car suspensions and suggested either a king-pin set up (similar to what the Piaggio MP3 uses) or even a trailing springer suspension. Both are a tad tricky as they require me to essentially hang the entire front suspension (in terms of dampening and rebound travel) on the steering knuckles along with the brake calipers and wheels. It’s not impossible, it’s just complex. Anybody have any insights?

Shape Study #2

This is my Concept #2 Streetliner. As I sculpted Concept #1 in clay and later in birch, I realized that making a body style like that tilt and lean into turns was going to be pretty difficult without perhaps having the mechanics under the body shell lean independently of it. As much as I love those european curves, that’s a level of complexity I can do without. So for Concept #2 I knew I wanted to try a nearly open wheel design. Inspired by a modernist 1930s era kid car on display at the Minneapolis Institute of Art, the initial sketches have taken shape. I’ve loving it! The single headlight up front gives it a feel one part airplane, one part streamliner locomotive. This is the front-runner aesthetic so far.

Streetliner Shape Study #1

This is my Concept #1 Streetliner. With so many converging inspirations, I’ve had to basically pick one and just go with it to see where it goes. This concept starts primarily with the classic Bonneville Speed Week streamliner racers that have set speedy fire to the salt flats for decades now. Specifically, while re-watching the movie The World’s Fastest Indian (Burt Munro being no small inspiration for this project himself) and seeing so many of those sleek, ’60s go-fast machines. I must also admit a bit of british roadster influence as well. I’m highly skeptical that I could make this body style tilt without some major wedge under-cutting of the shape under the car. As such, I probably won’t develop it much further. But it was definitely fun to get my hands dirty in modeling clay!

I am unoriginal. Score!

The more I do research for Project Streetliner, the more I’m confronted with other designers and engineers who have thought a lot of the same thoughts I have. I think that’s fantastic! It reminds me of how much the Wright brothers relied on Otto Lilienthal’s early work, and how they saw what brilliant folks like Alexander Graham Bell were doing completely wrong in their approach. Granted, I’m not really trying to do anything new here. What makes this a unique undertaking in today’s world, at least I think, is that I want to build it myself. I’m not waiting for “the market” to provide it for me. How often have we wanted something to be available, but nobody makes it? What’s truly stopping us from making it ourselves besides our own apathy? Maybe I’m completely daft for thinking I can accomplish this, but I don’t think so. If two bicycle mechanics in Dayton Ohio can fly using nothing but wood, canvas and balls then I can build my goofy little commuter vehicle. I won’t even need to build a wind tunnel.