Every few weeks I get an email out of the blue from someone expressing their appreciation for something I'm working on. Lately it's been my writing over at the Bluecat Motors blog that people are responding to. That's meant a lot to me as what I've been doing with BCM is something I'm really proud of. Most of the emails I get here at Project Streetliner are along the lines of "I was thinking the same thing!" That's exciting and I love getting those messages from people.
Just recently, I got another such message from a fellow called Russ. He's had similar ideas and appreciates where this design has come to, and inquired about the possibility of a future Streetliner kit. While a kit isn't a particular aspiration of mine for this project, the conversation we had via email inspired me to do a little update here.
While the lights have been dim here at Project Streetliner for a few months, I've been doing a lot of things that support this project. Specifically, I've been working on and off as a mechanic's apprentice down at Bluecat Motors. I write for their blog, and in return, they're helping me become more than just a recreational mechanic. I also spent a year working for an actual product development firm helping to bring actual products to market. I understand now — more than I could have ever known when I kicked this off — how unprepared I was to take this one when I started. That said though, I feel like with the knowledge I have now, I can actually really get started on this project.
Direct work on Streetliner is still several months away, but I'm going to keep the concept finalization moving forward. I have no fewer than three motorcycle projects that need to be completed before any work on Streetliner starts. But the upside is that these motorcycle projects will help to prepare me for fabrication. I've also got a line on a building space. Details to come later. Stay tuned.
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.
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?
Any ideas, internet? Anybody program a radio lately?
This vehicle exists in sort of a strange place in-between being a car and a motorcycle. It will lean like a motorcycle and utilize big scooter mechanicals, but it will also be enclosed like a car. There will be no need to put my feet down at intersections, because a simple on-demand locking system on the tilting suspension will allow the vehicle to stand on its own three wheels (which will also remove the need for a side or center stand). Being enclosed will mean both comfort, aerodynamic efficiency, and actually a large amount of safety. There really is a lot of elegant convergence here. The locking tilt actually enables me to never need to put my feet down, which makes enclosing the vehicle easier with no need for holes or "bomb bay doors" to pass my feet through. What I have yet to figure out, however, is how to back up.
You simply can't not have reverse. Sure, most motorcycles / scooters don't have a reverse gear, but you still have to "walk" them backwards to get out of parking spaces and other common driving situations. Some large motorcycles such as the Honda Goldwing do have actual reverse mechanisms, as do electric bikes like the Vectrix that use their hub motor for regenerative braking. But so far, I haven't been able to locate a scooter in the 400-600cc range that includes a reverse gear. This year's Honda Silverwing info says the following:
The V-Matic means no shifting, ever—not even into Neutral or Reverse.
This would seem promising, but a phone call to my local Honda dealer confirms that this is in fact just really, really bad marketing copy. So I'm at a bit of an impasse. Reverse is a must, but I can't find it built-in to any of the powerplants I'm considering for this project. So I've got to figure this out.
Electric option #1: Hub motors in the front wheels
There are a couple of ways that I could utilize electric motors for reverse. One route would be to use hub motors in the front wheels and essentially make an electric hybrid. Piaggio has a hybrid version of the MP3 that does exactly that. Front hub motors would make regenerative braking available, and with that, reverse. The major, and in my opinion, irrevocable barrier to this option is its complexity and its expense. I'd likely have to purchase those hub motors directly from Piaggio and they wouldn't come cheap. Then there's the batteries, which add significant weight, and the added complexity of all the speed controllers and power management systems it would take to link the motors to the throttle and balance them against the IC engine. As cool as a hybrid would be, it's an awful long way to go just for reverse.
Electric option #2: Drive the rear wheel on either direct friction, a sprocket, or a clutch
There are a number of electric and IC engine kits out there for motorizing bicycles. Many of these involve a friction roller that contacts the rear tire. Although probably not the most elegant solution, something similar could work very well. A small, high-torque motor like a wheel chair motor or a even an ATV winch motor could be suspended from a subframe that could be lowered against the rear wheel to turn it backwards. I'm picturing something like a hand-brake lever with a trigger button on it to run the motor. The Lightstar Pulse used a similar system, except that they used an aluminum cone pushed against the wheel rim instead of a rubber wheel on the tire. Online owners report that it's adequate, although very slow and apparently a massive battery drain. I was already planning to run a significantly larger battery than would be standard in a scooter in order to support a handful of ancillary electronics, so perhaps that would be enough, presuming the bike's stock charging system can replenish it.
One related idea I had in this vein would be to use a sprocket on the wheel that the motor could engage with its own toothed gear. Perhaps a starter motor/solenoid system would work. Apparently the Honda Goldwing uses a reversible starter motor for its reversing functions, albeit at the flywheel. The one thing I wonder about would be the wear and tear of that kind of engagement. As for the sprocket, I was thinking that I could just have teeth put on the rear brake rotor. It'd mean a bit of precision bracketry, but may indeed be the ideal arrangement.
The third variation would be to use a belt or chain drive between a motor and a sprocket/pulley on the rear wheel and be able to engage a clutch on that mechanism. Depending on how it was set up, it could even double as a low-speed charging system to recoup some of the energy used in backing out of a parking space.
Manual option #1: The Fred Flintstone method
Most velomobile trikes have a pair of holes in the bottom of them to allow the rider to back up under foot power. This could work for the Streetliner, presuming I have enough leverage to scoot the weight from a seated position. Having a pair of permanent holes in the underside of the vehicle does not appeal to me at all. Nor does having some sort of door/hatch system. This thing is complicated enough. Although, I have to admit, there is an elegance to just hoofing it.
Manual option #2: Some sort of crank to the rear wheel
Perhaps some of the electric methods described above could be similarly executed with a hand or foot crank in the cockpit. I'm not looking for fast reverse, just enough to get in and out of parking spaces and perhaps back up far enough to then pull forward around an obstacle like a stalled vehicle. There's something deliciously old-school about that, but it's probably not the best solution.
Any ideas? I haven't come to a solution I like yet. What haven't I thought of?
In the past few days I've had a terrific email exchange with Bob from Tilting Motor Works. His company has developed a fascinating kit to convert essentially any standard motorcycle into a leaning tadpole trike. But more importantly, he's done over 10,000 miles of real world road testing on his tilting suspension design. I asked him if directly linking the shocks to each other had any adverse effect on handling. Specifically, I wondered if hitting bumps while leaning or in other tricky positions would give the vehicle any proclivity to change course suddenly or alter its tilt. This was his response:
Yes, the force can be transfered directly to the other wheel but my experience shows me that it is no issue even while cornering or going over railroad tracks. Actually all suspensions ultimately transfer the force to the other wheels, just not as directly. I tested my suspension by laying 2x4's all around my cul-de-sac and running over them at different speeds and angles. The bike performed great.
This is such great news! A front suspension setup similar to what Bob's developed seems the perfect match for Project Streetliner, but I didn't know how capable that kind of dampening really was. I also asked Bob about comfort and he was happy to report that his front end is far more comfortable than stock and that his VMax prototype is always his first choice in a stable of fun vehicles. He's graciously offered his time and expertise and I'll be giving him a call very soon. Thanks, Bob!
This submitted to Tumblr by lamidesign:
I wonder if there could be a more mechanically simple solution than tilting the wheels. The wheel tilt is all about moving the CG - the contact patch is the same, and the tires really don't care if they vertical or tilting.
Can the entire sprung chassis pivot, or rock - I'm thinking like the inverse of a hammock between front and rear supports. If the body of the car leans into the turn then the wheels do not really have to.
That's a good thought. I had to think about this for a moment and based on my research, here's what I've concluded.
You are correct about contact patch — the tires won't care one way or the other and shifting the CG is indeed what adds to the dynamic stability of the vehicle. But there's one key reason why the front wheels need to tilt with the body: conservation of angular momentum. Utilizing the physics already induced by the spinning wheels to lean them over (and the body with them) is already the simplest in terms of mechanism (even if it's a little harder to wrap your head around). I can let the tilt mechanism free float and lean the vehicle just with the steering inputs — like I would on a motorcycle (via counter-steering). If I keep those wheels straight up and fixed but want to lean the body, I'd have to use a powered mechanism to force the body to lean into the turn. Were it just a hammock, like you've described, the natural inclination of the body would actually be to move the CG to the outside of the turn (because of inertia) which would quickly flip the trike.
The same gyroscopic force that holds a two-wheeler up is also the force that allows you to lean that vehicle via counter-steering. If I were to use a delta trike (two wheels in the back) instead of a tadpole trike, then I could use the angular momentum of the steerable front wheel to enter and exit the lean like you would on a motorcycle — all while leaving the rear wheels fixed (there are a number of bicycles that work this way). Unfortunately though, on a vehicle the size and weight of Project Streetliner, I'm afraid that the single wheel might not actually provide enough leaning force unless it were a pretty massive wheel. Furthermore, the complexity of driving two rear wheels instead of just one becomes just way more trouble than it's worth.
In 1983, Mother Earth News built a three wheeled leaning vehicle called the 3VG. It used hydraulics to lean the body of the vehicle into the turns. They seem to have incorrectly assumed that a 3-wheeler could not tilt on counter-steering alone:
Although we tried a number of different mechanisms in our efforts to find a system to induce camber in the car (because it has more than two wheels, it can't lean naturally like a motorcycle), only a handful proved successful. The "inclination" is at present controlled through a combination of mechanical, hydraulic, and electronic components ... all of which are available as "off the shelf" equipment, and some of which are so basic that they're commonly used in many toys and pocket calculators.
Both the Piaggio MP3 and the Tilting Motor Works prototypes prove that natural leaning in a tadpole trike works just like it does for a conventional 2-wheeler. They later describe the supposed problem of the force it would take to lean a vehicle of the size of their prototype:
It'd be ideal, for example, if the lean system were a stone-simple mechanical affair with a minimum of moving parts, but research showed us that such a design has some real drawbacks . . . one of which is that it takes almost superhuman force to initially lift the vehicle from the full-bank position. That's why we use hydraulics.
As I read that again, it sounds like they were again operating under the assumption that tilting the front wheels and using counter-steering simply wouldn't work. They don't really say if they ever actually tried. It sounds like they were trying to lean the body independent of the wheels, which would certainly require amazing force to overcome the weight and inertia of the vehicle body — especially one as large as what they built. Given what I've seen from both the MP3 and the TMW bike, I think that the size and weight of the vehicle could indeed have a significant impact on its ability to utilize counter-steering. I can only conjecture that the Mother Earth News boys either never tried, or that the significantly larger size and weight of their vehicle was more than the angular momentum of the wheels could easily overcome.
My design spec is to keep the vehicle weight under 600 lbs. The Piaggio MP3 500 weighs in at 530 lbs, so if I'm able to land anywhere in that weight range, then I should be just fine. That does bring home the point, however, why this vehicle isn't going to be something that anyone could just get in and drive. If you're not already a competent scooter or motorcycle rider, the coordination necessary to pilot a vehicle such as this would be completely lost on you, as you're essentially turning the "wheel" right in order to go left. That's hardly intuitive, even though we've all done it on bicycles since we were kids. That's also why it won't have a steering wheel at all. Ha!
Thanks so much for your submission!
I got an email a few days ago from Bob over at Tilting Motor Works. His tilting trike system is designed to be bolted onto the front of virtually any motorcycle. It appears to be using the same basic geometry as the German Tripendo recumbent bicycles and the Aprilia Magnet concept trike. His 10,000 miles of road testing seem to be a pretty sound endorsement for this kind of geometry. Good stuff. $10k is definitely beyond my budget for Project Streetliner, but I appreciate Bob reaching out and hope to still have him involved somehow.
I've been active on both of these boards since before I bought my first scooter, and now I've reached out to them to get involved with Project Streetliner. So far, there's been a ton of great collaboration. Check out the threads below.
@DuncanWilson sent me another great tilting trike video! This one has a close up of the lean locking mechanism, which is exactly along the lines of what I'd envisioned forProject Streetliner. I'm thinking a foot pedal that locks the lean on demand and a hand-lever (much like a parking brake) to keep it locked when desired. Looks like that's a pretty universal approach.