Category: Research

Two more nifty trikes

The Cree SAM

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Via Diseno-art.com:

The Cree SAM is a product of Swiss company Cree Ltd. The SAM is an environmentally friendly zero emissions vehicle powered by an electric motor. Only 80 Cree SAM’s have been produced so far, and most were bought by private consumers for public testing in Switzerland.

The electric motor of the Cree SAM is capable of propelling the 3-wheeler up to 53 mph (85 km/h). And on a full charge the SAM has a range of 30 – 45 miles (50 -70 kilometers).

The lightweight Cree SAM is built on an extruded aluminum chassis, and the two occupants, seated in tandem, are protected by the air-filled, double wall, thermoplastic body.

The SUB G1

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Also via Diseno-art.com:

The SUB G1 is a 3 wheeled sports vehicle which was first unveiled in April 2005. SUB is a small company based in Southern California run by three design professionals with impressive resumes, and between them the skills to design, model, engineer, and construct, high quality production machines like the SUB G1.

The G1 is a development of a similar concept vehicle (the 1up) created by one of the group, Niki Smart, years earlier. Smart, along with Jay Brett, an industrial designer with experience in constructing concept vehicles for films, and Nick Mynott, a digital modeller with experience in race and concept car construction, decided to develop an attractive, single seat, high performance sports vehicle, specifically designed for entertaining handling and extreme fun.

So far, three SUB G1’s have been built and handed over to their owners, 2 in the US and one in the UK, and each has covered over 1000 miles, with no problems.

One of the most noticeable features of the G1 is the outstanding build quality and level of professionalism visible in the overall design. Each part, down to the nuts and bolts, has been well thought out and made to fit with the finished product. By using computer models, the team was able to digitally create and adjust components before manufacturing, therefore reducing costs and unforeseen construction problems.

Power for the SUB G1 comes from a 1000cc Suzuki V-Twin taken from the Suzuki TL1000R sportsbike. The group had originally envisaged an inline 4 cylinder taken from the Yamaha R1, however early on in the mockup stages the group realised they would run into some packaging issues which would upset the 50/50 weight distribution, and the layout they wanted. The Suzuki V-twin fits perfectly, and is mounted to the right of the driver in its own compartment. Developing 135 horsepower and 105 Nm of torque, the engine is force-fed by the noticeable snorkel sitting above the bodywork. Transmission is handled by a 6 speed sequential gearbox connected to the rear wheel by a chain. Current prototypes have no reverse at the moment. But then again, if you’re to lazy to get out and push the diminutive G1 a couple yards it’s probably not your type of vehicle. The instrument gauges also come from Suzuki, and the cutoff sports steering wheel can be removed to ease entry and exit – while also providing a simple security device, if you take it with you.

Some thoughts on reverse

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?

The Brudelli Leanster

Thanks to the Yahoo! tilting vehicles group, I just discovered the Brudelli Leanster. The front end geometry is functionally the same as the Aprilia Magnet and the Tilting Motor Works design. One thing it does differently is that it has a tilt limit mechanism that keeps the bike from leaning over too far. As the photos show, the bike is able to lean over full tilt and not fall over. That’s what I want for Project Streetliner. It’s very nice to see that it’s possible. I’m also encouraged by the structural details of the frame and suspension components. They seem to be the kind of things that would be straightforward to fabricate. Very cool.

For more, check out their website: Brudelitech.com

Donor bike

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So at some point in this process, I’m going to have to decide on a power plant forProject Streetliner. My plan is to purchase either a used scooter, or one or more wrecked scooters to scavenge for parts. The question is, which one? The thing is, as I’ve researched this project more in-depth, I’ve realized that there’s more to be had from the right donor bike than just the rear end. Part of this project is to minimize the amount of custom engineering I’d have to do. Whatever I wind up with, I also want to stick to that bike (or at least that brand) as much as possible so that I can minimize the number of spare parts sources I have to manage. In a lot of ways, this ceases to be a scratch vehicle, and becomes an elaborately custom scooter. I like the sound of that! Components should really include:

Brakes
Obviously the rear brake disk and caliper are already part of a scooter rear end, so that’s handy. But what could and really should also be harvested from a donor scooter are the front brake components (calipers, disks, wheels, lines) and both brake master cylinders as well. Ideally, I’d like to use a bike that has either two front wheels (such as the MP3) or dual disk front brakes on the single front wheel (such as the Aprilia Sportcity, or the Suzuki Burgman). That would ensure that the brakes are already balanced and matched to the wheels and that the master cylinder is already beefy enough. Some maxi scooters also include a parking brake, which would definitely come in handy on a 3-wheeler.

Wiring, switches, controls, telemetry
Harvesting the wiring harness, gauges, and other goodies out of the bike would save a ton of work. It’d be pretty dumb not to utilize the gauges, the hand controls, and other switches and such that have already been engineered to work together on the bike. Why wire up a custom circuit for turn indicators when there’s one already built into the donor bike?

Wheels and tires
There really isn’t much interchangeability to scooter wheels and tires. There’s not the aftermarket for rims and such like there is for cars. So I’m likely to be stuck with the wheels and tires native to that scooter. One exception I know of is the Piaggio QUASAR engine line that is shared between Piaggio, Vespa, and Aprilia bikes. The 12″ wheel of the Piaggio MP3 could be plausibly swapped for the 16″ wheels of the Aprilia. The main advantage there is that swapping to the larger size effectively makes the end gear ratio higher (and therefore adds to fuel efficiency).

So when it’s all said and done, the only parts of the donor bike I wouldn’t be utilizing are the front fork, lights, the handle bars themselves, the majority of the chassis structure, and the seat. That’s it! The last lingering question for me was engine size.

I’d originally envisioned this project to utilize a 250cc scooter engine such as what’s shared between the Vespa GTs 250, Piaggio MP3 250 and Aprilia SportCity 300i. That, or a similar 250cc engine from Honda, SYM, or Kymco. A 250cc motor is kind of the sweet spot between performance, weight and fuel economy in the scooter world. The MP3 seems an ideal choice for the obvious reason that it’s already a leaning trike. The MP3 also comes in 400cc and 500cc versions should the need to up-size arrive.

Speaking of which, I’m pretty sure at this point that up-sizing is inevitable. This is mostly because of the likely weight of Project Streetliner. My design criteria is to stay below 600 lbs curb weight. Scooters in the 250-650cc engine classes tend to weigh in between 340-550 lbs. Thing is, it’s not speed I’m concerned about, it’s economy. You see, a small engine having to work really hard will usually get worse fuel economy than a slightly larger engine that isn’t having to work so hard. (For example, on a racetrack a BMW M3 gets better fuel economy than a Toyota Prius when both are driven at the Toyota’s quickest speed.) So if my vehicle does indeed weigh 600 lbs, a 400cc engine will likely get better mileage (and conveniently give more power) than a 250cc.

So that brings me to my latest bit of hands-on research. I stopped by the local Suzuki dealership to look at a Burgman 400 — a bike considered by the folks who like such machines as the premier maxi scooter on the market. It seems perfect! The Burgman is the front runner right now for a couple key reasons. It already gets the mileage I’m shooting for, weighs in at 474 lbs, has dual front brakes, and a great reputation. Looking it over, it’s now the definite front runner in my search for a donor bike. What’s more, Suzuki has sold a boat load of them so there ought to be plenty around in the secondary market. That certainly can’t be said for the MP3, I’d wager. Anyboy have any other suggestions?

Fantastic correspondence from Bob from TMW

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 2×4’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!

Tilty wheel alternate

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!