Existential crisis of criteria?
Things have been quiet here at Project Streetliner for a while. Progress is paused on my small-scale prototype while I wrench on a pair of old motorcycles. Meanwhile I've had a lot of ideas rolling around in my head. Thing is though, these haven't been ideas of progress, but rather ideas on how this project might drastically change.
Right now, the vehicle is designed as a tilting, petrol-powered, highway capable commuter vehicle. Thing is though, my commute now is mostly city streets. Do I really need to do 70 mph? If I'm just zipping around surface streets, is the leaning really needed? Is there actually an opportunity to do a full EV or an EV + generator hybrid vehicle? That has me wondering if I shouldn't re-spec this project for something closer to my actual use scenarios. Should I shift to more of a velomobile-style bike path runner?
For example, one idea I keep thinking about is basically taking apart a golf cart f0r its motor and controller, welding up a custom solo frame, then maybe adding Honda's smallest generator for onboard charging. If it'd just be a bike path / lane vehicle, then there's no real need for a full cage. I'd still be wrapping the whole thing in some sort of aerodynamic body. That'd be pretty sweet.
The other idea I keep tossing around is a non-tilting version of the Streetliner — something perhaps a tad lower and a bit wider up front. This concept would still be scooter or motorcycle based and highway capable, but having a flat trike setup means a slightly simpler chassis and suspension setup. I'm really ambivalent about this one, simply because it isn't that much of a complexity save. It would mean a control change that could be nice — that is, I could use conventional car controls rather than a handlebar and motorcycle controls.
Speaking of motorcycle drivetrain, that's been on my mind as well. I understand those mechanicals a LOT better than I used to. An older, air-cooled japanese motorcycle engine is simple, reliable, powerful, and even reasonably efficient. Parts are still abundant, and whole, running motorcycles are available for less than $1000. Changing sprocket sizes for different gear ratios is really easy if I go the motorcycle route. That coupled with the aerodynamic gains from the body shape should make my 60 mpg goals pretty easy to reach. The disadvantage there could be weight. But if my efficiency goals can be met, then does an extra 100 lbs really matter?
The last conceptual quandary I'm trying to figure out is broader purpose. That has a couple of connotations. Do I optimize the vehicle as an in-town commuter with highway capability for getting around town on the bypasses? Do I optimize for surface streets only — so a top speed of 55 mph or less? Or do I optimize the Streetliner as a long-distance touring vehicle? A coast-to-coast road trip at 60+ mpg would be pretty cheap to do. But it's not just me these days. For a long-distance tourer, I'd want to be able to have my wife with me and we'd need at least a little luggage space, even if we're traveling light. That's a pretty big change to design criteria. I'm open to it, but like any of these questions, it's a significant shift from the current concept. Decisions, decisions.
Any thoughts?
Small scale prototype progress
I've had these videos for a few months but have had a bitch of a time getting them off of my iPhone in their entirety. Finally DropBox came to my rescue and so here they are. The quality isn't great, but you can see some of my progress toward turning an old R/C helicopter into the first small-scale prototype for the Streetliner. Since shooting these, I've actually reworked the rear swing arm in brass and have abandoned the profile-style chassis. Even still, this is a good look into where I started on the SSP. Enjoy!
Sidetracked, but not inactive
I got an email yesterday morning asking essentially "where the hell have you been?" and it's a very valid question. Things have been quiet here at Project Streetliner for the past six weeks or so — not for lack of activity, but for other priorities. The Mrs and I bought a pair of three-decades-old Honda motorcycles for a laughably small sum of money about a month ago. We wanted to be able to wander the tri-state area the way we can wander the Twin Cities on our scooters, and now we can. Or at least, we'll be able too after I do a little more wrenching. So work on the Streetliner R/C prototype has paused until I get these machines sorted out, but that should only be a few weeks. The flip side of this, however, is that these being my first interaction with the mechanicals of proper motorcycles, I now have a much better understanding of this sort of machine. This can only help me make better decisions on the Streetliner. As I've gotten more familiar with the simplicity of these machines (especially these early '80s Honda bikes we've got), I'm considering a lot more motorcycle components in my end vehicle. I've even toyed with the idea of changing from scooter to motorcycle drivetrain. The cost savings alone are pretty compelling. But that's a bit rash at this point. We'll see.
Sorry for the long silence, progress is indeed being made. In the mean time, please enjoy some snapshots of my R/C prototype in-progress. I've since re-made the rear swing arm almost entirely out of brass and abandoned the profile body, but these first efforts were very enlightening.
Any R/C experts out there?
I'm trying to answer a radio transmitter programming question. I'm familiar with R/C systems from flying R/C aircraft when I was a kid, but we never really flew anything that was complicated enough to need a programmable transmitter. For the Streetliner R/C prototype I'm working on right now, I have sort of a unique control challenge I'm not sure how to solve.
I plan to include a tilt lock system on the R/C prototype (RCP) similar in function to the tilt lock mechanism I have planned for the full size vehicle. That is, an on-demand way to lock the front suspension tilt and keep the body from being able to lean. This for low-speed maneuvering, stop lights, and parking. The R/C mechanics of this are simple enough — just dedicate a servo to push in a pin or some other mechanical stop. The problem is, because this is a free-tilting vehicle that will turn via counter-steering, once I lock the tilt, my left/right control will actually be reversed (since you turn left to lean right on a motorcycle or similar single-track vehicle like this). By locking the tilt, I've returned to conventional steering.
So what I'm trying to figure out is if that's something I can program. Can I set up my radio transmitter such that when I flip a switch, the tilt lock servo actuates whatever it actuates AND the steering input reverses? In a way, I suppose it's similar to the pitch control reversal on the "inverted mode" switch for an R/C helicopter (which I've just realized that I have one of those just laying around! Insert maniacal laugh! Bwahahaha). Trouble is, that's on the pitch axis, not the roll axis and that inversion does not also push a servo to do anything. It also reverses the blade pitch, which isn't quite what I'm after either. Or would that work?
Frak.
Any ideas, internet? Anybody program a radio lately?
Small-scale prototype coming along
Here's how things are coming along so far. I'd originally imagined that I'd create the whole chassis setup out of soldered brass tubing in an effort to simulate as much of the full-scale structure as possible. I'll probably still do that, but for this prototype I realized that I still need to evaluate a lot of the big-picture stuff. I need to verify that counter-steer leaning actually works. I need to see what effect rake angle has on the handling and stability. I also need to build these trickier components — like the steering knuckles — so that I better understand them. It isn't that the full-size pieces will be exactly the same, but by building them at all, I'll understand them better.
In the past, I've also written about the concept of a treadmill prototype. The idea was to go dead simple and just knock something up to demonstrate the front suspension. That would then have some sort of cable-driven steering input and the idea was to tether that model to a treadmill and see how it behaved. Now that I've got it knocked up to an extent, I've realized that I won't be able to do that to the level of precision I'd need to in order to have something useful. So I'm going to do it as a radio controlled prototype so that I'll have adjustability and precision inputs. I'll be able to actually drive the thing around. My construction style for now is mostly 1/4" ply, brass tubing, #6-32 hardware, and then miscellaneous pieces of brass hardware. The body will be in profile and should allow me to mount all the servos, batteries, and other gear needed to turn this into a real test platform.
The most fun I've been having with this is not even in the actual build, but in the days on end spent thinking through how to execute some of the precision mechanical pieces needed to do this. What I've arrived at is a combination of brass tubing, brass hardware and then soldering everything together with as much precision as I can. Brass is soft enough that I can sand it to precision, and the soldering lets me build surprisingly complex joints that are tough enough to stay together without being sloppy like wood or plastic. In time, I probably will do a true miniature Streetliner made out of brass tubing and even with a scale body in place. But first things first — have to prove that it works first.
Small-scale prototype in the works
Hey folks. Just a quick update that things have not in fact gone cold in The Lab of Doom. I've started a small-scale proof of concept prototype and will have a more comprehensive update on that shortly. Stay tuned.
Design Concept Beta in Foam
I spent some time today knocking up a quick shape study in floral foam to get a sense for the new shape in 3D. Really like it so far. Want to do a larger version over top of my prototype chassis when the time comes.
Design Concept Beta
Based on the entry/exit concept discussed in my previous post, here's a 3/4 front rendering of what that new, evolved shape might look like. Any thoughts?
Entry and exit: its ramifications on exterior design
There's been a lot of activity on the Streetliner drawing board this week. If you've been following along, you're familiar with the shape above. This '30s era race car inspired shape is what I've been showing people when they ask about what I've got in mind for this project. I love it, but I knew all along that this shape would inevitably change and evolve.
Likewise, one major aspect of the Streetliner's design had yet to be worked out in concept: entry/exit. How the hell do I get in and out of the thing? It's not that entry and exit is terribly complex, but in figuring out a good way to get in and out, it meant big adjustments to the exterior design of the car. So like any design undertaking, this needed criteria.
- The integrity of the safety cage needs to be maintained as much as possible
- Getting in and out has to be simple. No folding myself up snaking through impossible openings
- I must be able to exit the vehicle even if the primary door system fails
So starting with the current exterior design, a handful of things have been adjusted since I first penned Design Concept Alpha. The overall length increased, the front wheels got larger, the wheel pants got longer and no longer turn with the front wheels. I really like this shape overall. The snout shape of the front end is very pleasing, the rear has a lovely duck tail quality, and I especially like this design because the vehicle looks even better with its canopy on. All of that shape, however, is mated to an underlying safety cage and chassis:
With arches as the vertical pieces, the safety cage design is pretty straightforward. Heavy duty curved bulkheads are connected by heavy duty rails, then everything is cross-braced in a truss of smaller diameter steel. The angled front and rear main plates actually create rudimentary "crumple zones" where impact damage would send the motor assembly and or front suspension components under the vehicle in the event of an impact. This design is structurally sound, but it has one major flaw: how the hell do you get in and out of the thing? The height of the cockpit opening lip is right at 36" in this design. I'm pretty tall, but that's still quite a height to throw a leg over while getting in and out. I also realized that I'd only given myself a 24" deep opening front to back. I'm not a whole lot narrower than that myself (it's winter weight, I swear!). So the practical concerns of getting in and out of a high, narrow opening are pretty significant. But even beyond entry acrobatics, with such a narrow opening, I wouldn't be able to see my hands or any cockpit gauges. That top opening needs to grow and dammit, I need a door. The tricky bit is how do I add a door without compromising the safety cage?
One thing at a time. I added an approximation of the front suspension "box" and see where and how that should tie into the frame. I lowered the bottom rails to tie in to the front and also simplify the rear subframe where the mono-shock would attach. I also moved the main roll hoop back just slightly where previously it was implied that it would overlap my shoulders. Upon further reflection, I realized that this being a single seater, I only need one door. Even though my diagrams here show the opening on the left side, I think I'm going to opt for the right side having the door. Since the majority of motorcycle accidents involve people violating your right of way from the left, it makes sense to me to leave the left side solid. That written, the underpinnings of the door as I've envisioned it are as substantial as the major parts of the cage. That way when it's closed and latched, the door becomes part of the safety cage. I like to think of it like the harness that comes down and locks in when you get on a roller coaster. Solid. Also, thinking about an impact scenario, that's a force into the cage, so if the door is structurally captive against being pushed through the opening, it ought to be as good as solid. With the door opening on one side of the vehicle, the canopy (when attached) could hinge along the opposite edge — making for a very easy time getting in and out.
With that adjustment made to the frame, the body shape needed adjustment, as you can see below. The opening needs to be increased to meet my design criteria for being able to exit the vehicle in a pinch through the top without using the door. The bottom profile of the body shape also needed to be adjusted to account for the front suspension box.
Now with the shape updated, I like it even more. The larger top opening not only gives the whole vehicle a better proportion. It looks smaller and more trim overall. Before now, with the length being about that of my MINI (which I know, isn't exactly big), the Streetliner has looked strangely large. Now it looks much more like the race car cabin scooter it was always meant to be. I also reshaped and shortened the wheel pant to account for the door opening.
I really felt like the new shape came into its own with the canopy in place. Not only was it less bubble-shaped, but it completes the curve created by the tail. I can also imagine much better visibility and comfort within the cockpit. That led me to consider some alternate front end shapes. One of which was the sloped, Ferrari GT-style nose. It would borrow its hood scoop aesthetics from a different era than I'd previously been thinking, but I really like it. Forward visibility would be better and overall aerodynamics might be a tad stronger with this sloping approach.
All that remained at this point was to add some visual interest to these basic shapes. This included sculpting the rear and adding a sort of LeMons-style front lip to the wheel pants. I really don't want to overlook subtle details throughout the shape. Sure, a perfectly smooth Velomobile kind of shape is terrifically aerodynamic, but without at least some minimal sculpting, I think the shape would look like it were stuck in the '70s and just generally unfinished. These details will surely evolve as the project progresses, but I'm loving it so far.
As I look back on the progression, it's amazing how much influence a little thing like a door can have, but all for the better! This shape still has a lot of classic Italian sensibility, a lot of race car mojo, and plenty of salt flats shape credibility. As much as I love the '30s sensibility of Concept Alpha, I like this even better. But more than that, I'm glad to have another big piece of the conceptual design puzzle in place.
Cal Poly students create streamlined trike capable of 2,752 mpg
The Black Widow, as it's called, is the winner of the Shell Eco-marathon. Looks the business doesn't it? What's thoroughly amazing is that they did it without any electrical propulsion at all. Just a 3 hp Honda 4-stroke engine no doubt geared to the ceiling. Good stuff. More details here.
