Two and three wheel cycle design, like other machinery, is a series of design and material tradeoffs, an exercise in creative compromise.
DISCLAIMER: Despite my nearly four decades of design and production experience and a dozen mechanical patents in my name, my knowledge of cycle design is rather limited. So . . . please insert plenty of IMHOs throughout. This is additionally important because I have not ridden any other trikes and comparisons, where they exist, are between two and three wheel recumbents -- apples and oranges.
SECOND DISCLAIMER: My connection with William Mason, the Raven designer, consists of endless e-mails, one lengthy report and some phone calls in which both of us provided free-wheeling, free exchanges of advice and constructive comments.
Problem 1: Because of FWD, there is traction (forward motion) loss when climbing wet or sandy hills since inclines reduce weight on the front-drive wheel at the time a rider needs it most.
The degree of wheel slippage will depend upon not only road conditions and pitch but also how far forward or back the seat is positioned, and seat angle. Leaning forward [un-recumbently] in the seat reduces wet/sandy wheel slippage but is a difficult t position for me to sustain.
The possibility of small, electric motors being added to the rear wheels primarily for hill use, suggests that two birds [one a raven] might be stoned simultaneously. The mechanics of this, however, are not obvious to me.
The best eventual solution might be a seat mechanism with two positions that can be adjusted on-the-fly: Angled forward for slippery inclines, angled back for comfort and aerodynamics. Such angle changes will, however, affect leg stretch. When hills are not wet or sandy, traction is not a problem.
Problem 2: The steering mechanism is overly sensitive during high-speed descents so that small directional changes may cause potentially dangerous over-corrections. Other riders have confirmed this characteristic. I wish I were able to compare this tendency with that of other trikes, especially rear-steer types. After a few months, I can now descend at thirty something mph before my adrenaline starts to flow.
Problem 3: Turns. The Raven's minimum radius [no fork or pivoting boom] is large at very low speed [about two narrow road lanes]. Away from traffic, this is seldom a problem because the rider can "reverse" during turns: roll back or spin rear tires backwards by hand. At higher speeds, with lots of body lean, turns are tight.
Seat tipping takes getting used to at low speeds and for some neophytes, when they first sit down [off center] if the steering is adjusted for minimum drag.
Allen Parducci has written perceptively: " . . . having had an all too limited opportunity to ride one . . . it seemed to me a disadvantage that the degree of tilt determines the radius of the turn, independently of speed. For example, when making a tight turn at slow speed, I felt that I was sliding off to the inside. Otherwise, I was enormously impressed by the simplicity of the design."
When I [R.L.] first started to ride the Raven I tended to hook my opposite-the-turn-direction elbow against the seat side during slow turns. Now I never do, at any speed. A combination of forces? or vectors? hold the rider securely in the seat, especially on high-speed, tight turns. As I'll discuss in the next report, this is part of the remarkable sensation of riding this machine.
Problem 4: The rear wheels may brush against the rider's arms but unless the rider is extremely broad shouldered, this quickly becomes a non-event. Riders with broad shoulders will probably find their arms contacting the rear wheels too frequently. The Raven may not be an appropriate trike for them. A lengthy test is recommended.
Problem 5: Grip shifters are turned 180 degrees from the conventional position so gear-change direction is reversed. Confusing, especially if the rider switches cycle types. Bar end shifters to the rescue?
Problem 6: Road water (including any mud salt and oil) sprays rider's face, clothes and water bottle. I'v e made a full, front fender to which I attaced a computer, compas and ride cue sheet.
Problem 7: While the seat-to-pedal distance can be changed, doing so is slow and requires tools. A second set of top brackets attached to seat bottom, however, speeds up change-overs . . . helpful for demonstrations and alternate riders.
Problem 8: For those, like myself, who like bar-end mirrors, when the steering bars are elevated and lowered during turns, the mirrors are angled and rear view angle is changed.
Problem 9: The Turner seat may prove too warm in the summer. Also, the reclined seat angle may stress some rider's neck muscles or aggravate arthritis. It is easy to make a quickly-adjustable head/neck rest that also holds tools, tubes and such. Mine has eliminated all discomfort.
Problem 10: My Raven, # two or three? has an awkward mixture of metric and non-metric hardware. This was a pragmatic compromise but the designer intends to correct the problem soon.
SUMMARY. Ten problems? Most are minor. I was aware of all the important ones during twenty days [less some snow-days] of testing. And despite the problems, even #s 1 & 2, I decided to buy the Raven. The designers receptiveness to criticism, his apparent integrity and his commitment to resolve many of the problems helped me make up my mind.
Just as important: I was simply having too much fun and enjoying the wonderful sensations too much to part with such a sophisticated and elegant toy.
Cycles, like other human creations, are an elaborate collection of trade-offs. No one machine can be good at everything or make everyone happy. Finding the Best Fit, it would seem, is not just a matter of size but also of the rider's needs, objectives and dreams. Part Two attempts to do justice to the Raven's strengths.
The biggest challenge: attempting to explain how the Raven turns.
STEERING MECHANICS: The Raven has two lever-like side tubes or bars. They support the Sachs Twist shifters and brake handles. They also can be used to steer the trike. The bars, in turn, are connected, via axle stubs, to the rear axle. Tie rods with universal joints link the axle to the frame.
Despite my confusing description, the geometry looks simple and behaves well. The rider pivots, let's say, the right bar up and/or the left one down, or leans hard left which activates the same bar action. Simultaneously, the entire rear axle shaft and wheels rotate clockwise on a vertical axis in relation to the frame while the rest of the cycle: frame, front wheel, seat and rider tilt, or lean left.
MORE PARTS: There is an axle pivot component and also a stem incorporated into this ingenious steering mechanism without which Raven's designer, William Mason, might not have been granted a Pat. Pend.
TURNING KINETICS: Turning is a totally natural and joyous sensation. Centrifugal force [or vectors?] hold the rider in the dramatically angled-back and tilted-sideways seat. [The matter of s-l-o-w turns was explored in Part One.] On fast, tight turns Raven riders intuitively lean their head and upper body even more into the turn than the tilting seat dictates. This holds the inside wheel in contact with the road and provides astonishingly secure, fast, tight turns. The faster I whip around, the more I hang out and the greater the sense of speed.
I do not know which other trikes provide this superb combination of on-the-level turning speed with stability. The Raven has, however, a very low seat [9 or 10 inches off the road], is wider than most trikes and shorter than all others whose specs I have seen.
LEARNING CURVE: Trike, and for that matter, bike neophytes need only a short period of adjustment before they experience comfort, confidence and exhilaration in all but reckless rides. Most of the skills needed for two-wheel recumbent technique are unnecessary, such as balancing and starting/stopping without wavering or falling and starting on inclines. The third wheel means no minimum speed needed when climbing hills; good news for overworked knees.
COASTING: Coasting down a hill is a blast. The Raven left a Vision R 42 and an R 45 way behind in separate coast tests. Low friction tires and Phil Woods hubs may help but the aerodynamics probably account for most of the advantage.
GOOD LOOKS: The Raven has a simple, clean, elegant appearance. Many bikers and engineers are fascinated with its unusual geometry, beautifully machined parts and finely-articulated design. The elimination of the fork, conventional handle bars as well as the front wheel drive help; as does the Raven's short chain and single chain ring; so does William Mason's respect for elegant design.
The Raven probably reflects long winter nights at a drawing board, numerous prototypes and years of testing, tweaking, testing . . .
SIZE: Despite the 36 inch broad rear end, the Raven is compact: low and unusually short. So short it fits in my Saab 900 with all three wheels and seat attached (car rear seats/backrest down.) For tighter spaces: the trike's rear wheels come off in two minutes, axle end sections dismantle, if necessary, in about seven, I'd guess.
HANDY REAR WHEELS: With rear wheels so close at hand [possible disadvantage discussed in Part One] the rider can back up using "wheel-chair" reverse-tire spin. This technique can also help to climb those wet and sandy hills for short distances. Longer for the stronger folks. Since all three tubes [and normally tires too] are identical, carrying spares is easy.
FRAME: The Raven has an uncommonly rigid frame. It consists, in part, of two side-by-side, large diameter tubes. Also, its short chain [less than some uprights] reduces all apparent frame flex.
ACCELERATION: Because of this low-to-no frame flex, the Raven's light-for-a-trike, 34 pounds combined with the Turner [relatively rigid] seat, the Raven accelerates admirably. A Paris Island Marine who rode my Raven thought its accelleration was slightly slow until he tried it with the brake off.
FWD PROS: FWD means reduced weight, friction, noise, chain cleaning and lubrication time. Idlers are absolutely obsolete and anyone who needs greasy chain marks on their legs to proclaim their activities will have to design a rubber chain stamp.
BODY STEER OPTION: This trike's geometry makes it so steady it can be ridden hands off on the straight-away and with practice, steered with body weight alone for long stretches [Obviously this means that brakes are not at hand. Its easy to zip ornery zippers and hold a camera at high speeds.
BRAKES: The double set of front rim brakes provide remarkable stopping power. The big question is whether long, steep, mountain descents will overheat the rims and tires.
SHIFTING: The quiet, quick-shift, Sachs 3X7 system is marvelous, especially for at-rest internal gear changes and in-motion, no-let-up-on-chain-pressure, cog shifts. The 44 tooth chainring can be replaced with a toothier one for Florida or a less toothy one for Vermont. More complex gearing options abound.
THE SEAT: A very comfortable seat provides fine [customize-able] lumbar support. The seat angle and distance adjustments, though slow, are extremely welcome. [See Part One for options.] The Raven is delightfully easy to mount. The only difficulty with dismounting is my desire to stay seated forever.
ROAD CAMBER: The effect of road camber is generally considered a drawback for trikes. I have not found it to be a problem with the Raven, probably due to this trike's geometry. Both camber and negative banking can generally be neutralized with very slight body lean. This kinetic involvement with one's sport and transport, is certainly one of the rewards of the Raven ride.
WIG WAG?: Some trike design configurations tend to exhibit wig-wag, a lateral movement caused by uneven pedaling action. With the Raven it is evident, but only minimally, and only, for me, at high cadences.
COST: Considering the quality of the Raven design, its components and the negative economy of scale [trikes are manufactured in small batches] I feel the Raven is reasonably priced.
TEST!: Words have been inadequate. The beautiful sensation of riding the Raven can not be described. It comes from a combination of factors that need to be felt. Whether this trike or any trike is the best cycle for you, taking into account your intended uses, only serious testing will reveal.
ASSEMBLY?: The Raven arrives beautifully packed in one box and is easy to assemble. William Mason, the designer. points out: ". . . there is no real need to adjust the wheel alignment for tracking (toe-in etc.) and this makes it real easy to set-up out of the box." Included is an excellent manual for assembly and maintainance, a flag and two side-view mirrors.
TOURING?: Is the Raven a good touring machine? So far, I have not used it on multi-day, camping-out tours. If I did, I would give considerable thought to where cargo goes. Remember this is a FWD machine that would loose crucial uphill traction if weight were added to the tail end. [Update: I have since added a large in-line skater's bag to the rear seat which holds enough stuff for normal touring but not camping]. The Raven provides a first-class seat for long days of sitting and spinning.
OFF-ROADING?: The Raven is not an ideal off-road vehicle and not just because you can't stand on the pedals to suspend your body and perform maneuvers. One of the obvious disadvantages of FWD with most weight over the rear wheels is poor traction on mud, sand and other soft surfaces. Knobby, fatter tires would help, a little. I have ridden on rough terrain with minimal difficulty but only when it was fairly dry and not too steep.
SNOW AND ICE: This trike is made in flat Wisconsin which could explain the FWD but also may explain why it handles so well on snow and ice.
Studded tires can be added for serious ice sports and wider, knobby tires for deep snow. Fantasies of safe, three-wheel winter cycling were my winter cabin-fever cure and part of my decision to test the Raven. I charged out astride the Raven during several snow storms and except for climbing, was awed by the trike's performance in snow, ice, slush and other such adverse road conditions. [Update: I have studded front and rear tires and raced around on a frozen pond with no cars to contend with and no fear of tipping. It alone is worth the price tag.]
BEING SEEN: Am I worried about drivers not seeing me. In city traffic, yes, probably. On the open road and in town, no. Drivers think I'm crippled or crazy and they'd be right if I succeeded in convincing them otherwise. My United-Nations-like flag display is anything but subtle and I won't leave home without it.
SEEING: Stable trikes are low. This means some compromise in rider vision. I sometimes sit up as I approach an area that needs to be checked. I tend to be anxious about _parked_ cars and trucks that might pull out as I pass, since the drivers are more difficult for me to see than they would be from a higher cycle.
MORE SAFETY MATTERS: I believe that I am a safer cyclist now than when I rode with one less wheel. I am more inclined to come to a full stop, where appropriate, since I don't have to disengage a foot from a cleat or worry about starting up a recumbent on an incline. I'm not anxious about instability [two-wheel recumbent variety] when I shift my body.
More important, though less frequent, the Raven [and I assume, other trikes] laugh at side winds that challenge two-wheel riders and occasionally blow them off the road. Fifty-mile-an-hour gusts have had no effect on the Raven's lateral course.
GEAR riders who waited out a minor gale in Florida, showed a new-found respect for low-down, three-wheel geometry as I returned after fifty miles, smiling. Even serious head winds are more manageable than on higher cycles.
STABILITY: When I lock the brakes at high speed there is no wheel lift or peculiar behavior. Fast turns on post-winter sandy roads are amazingly un-traumatic. They may result in a little drift towad the outside of the turn.
Mason does urge neophyte trikers to hold back on descent speeds until the rider has developed appropriate skills. Even coasting, at which the Raven excels and accelerates, can feel like free-fall.
STEERING DESCRIPTION: Allen Parducci, whose philosophy of cycling is in tune with mine, at least when I'm not feeling competitive urges, chided me: "Bravo again, an excellent summary of the Raven's virtues. [But] I think you did a little end-run around the difficult-to-explain principles of lean steering. "
Allen's description was better. But no simple matter, this.
William Mason, the designer, once said that the Raven does not have true lean steering so I e-mailed him for clarification. The following is part of his answer:
"Lean Steering, to my knowledge, is what would happen if you remove the two tie rods and fix the handle bars on the Raven so they could not rotate in their bushings. Then, the way to steer would be to use your arm and shoulder strength and rigidity and to roll your body thus providing the steering action for the frame. This kind of steering on a trike like the Raven is alright at low speeds, but at high speed as you note, small changes make for more dramatic effects and ones upper body is not stiff enough to handle the trike. One solution is to lay-down the rear pivot so that a projection of its centerline is contacting the road ahead of the front wheel's point of contact. Turning radius will be very large with this geometry. The Raven's minimum turning radius is around 95-100 inches.
The Raven's steering is a combination of mechanical links and a balance of geometry which enables one to control this very short wheelbased trike at high speeds. It is a single degree-of-freedom system in that it has only a single lean angle at every handlebar position. That is probably a disadvantage since lateral cornering force is a function of your velocity^^2 (squared) divided by the radius of the turn. Note, the velocity >squared term quickly dominates. In short, for every speed and every radius of turn there is an optimum >balance point of lean as experienced on two-wheel cycles. An ideal trike would have both lean and >steering as a loosly coupled system (in my opinion)."
THE DESCENT DISSENT: This is the behavioral idiosyncrasy I raised in Part One. A while back, Mason suggested two techniques for improving control on speedy descents. To paraphrase: Don't use a death grip on the steering bars; and lean a little in the direction you intend to turn.
When I tried the second part I discovered I needed less umph at high speeds to make little corrections and at thirty-something mph downhill [which seems like forty-plus] it now feels safer.
Fast turns at break-neck downhill acceleration? Not on your life!
The box my Raven was shipped in is wider than that of most recumbent boxes, but is shorter and lower than the box my two-wheel recumbent came in. The trike fits back in the box between those great chunks of rigid foam it comes with and accompanies me on the plane. What to do with the box on arrival can be the real problem.