Category: Research

How to make a fiberglass mold

Here is an eight part series on the basics of molding and casting in fiberglass. I’ve done a lot of this before, but it’s very good to have a refresher. Casting key FG parts for Project Streetliner is going to be a major part of construction. I’m thinking that perhaps I need to go ahead and shell my bicycle prototype velomobile-style when the time comes. Although, that’s kind of awesome — if I take my time and do that prototype correctly, I’ll actually have two vehicles when this is all done. One for the highway, and another for the bike path. That has me thinking about electric assist…

So why is tilting so important?

Some may wonder why I’m insisting on a tilting 3-wheel design for Project Streetliner. Watch about :30 of this video and it’s pretty obvious. The trouble with non-tilting trike is well explained by Wikipedia:

The disadvantage of a rear drive, non-tilting three wheel configuration is instability – the car will tip over in a turn before it will slide, unless the centre of mass is much closer to the ground or the wheelbase is much wider than a similar four wheel vehicle.

So unless the wheels tilt, you’ve got to essentially crawl around corners. I’m not planning to race this vehicle, but I do want to be able to take evasive action in traffic. So tilting it is! A vehicle like the Morgan was low enough and wide enough that it doesn’t really have this issue. But if I want to really benefit from a smaller frontal aerodynamic cross section, I’m going to need to keep things narrow. The advantages of a Piaggio MP3-style front end keep piling higher and higher.

Gizmag’s comprehensive review of narrow-track vehicles

Gizmag is one of my favorite new tech news sources precisely because of their affinity for new vehicles. This video is a fan-tast-ic overview of all the single and narrow track vehicles in the pipeline right now. They’ve put those innovations into very sharp perspective as well — laying out the reality of traffic congestion we’re going to face in the next decade and beyond. With the number of cars on the roads worldwide set to double in that time period (greatly outpacing the growth of road infrastructure), one of the best solutions may indeed be smaller vehicles optimized for efficient commuting. Narrower, nimbler vehicles means not only drastically less fuel consumption, but less congestion.

What this means for Project Streetliner is that I’m re-evaluating width. The seed of this idea was essentially for a recumbent version of the Piaggio MP3 with a streamliner shell on it. In the video, the presenter talks about how the Nissan Land Glider concept began explicitly with a half-width vehicle. In my mind, a vehicle like Concept #2 would be about 2/3 the width of a standard car. If I adopt a more narrow track and shroud the vehicle more like a Velomobile, that could make for a very interesting vehicle.

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?