Modular Recumbent Tricycle: A New Generation of Human Powered Vehicles
Recumbent tricycles are now well established as a type of a cycle, and their advantages with respect to the bicycle are well known. Yet it is still a rarity to see one on the road. Of course, they will never become more popular than bicycles, but in many cases three-wheeled recumbent vehicles are more preferable, since they offer more of a leisure-type of activity.
These days there are only true enthusiasts who are riding tricycles. Most of them are strong, young men. Why the rest of the people do not want to have and drive a recumbent tricycle? Perhaps the existing models don’t suit their needs?
After some testing and analyzing we have found A FEW MAJOR DISADVANTAGES OF EXISTING MODELS:
1. STORAGE and TRANSPORTATION.
Recumbent tricycles are relatively large.
Like all personal vehicles, they are usually used for short periods, and the rest of the time they must be stored at some place. This is a serious problem even if you are living in the house with a garage or shed. In case of a residential building, to store such a vehicle is impossible.
Another problem is transportation of tricycle by a car. Only a few of the existing models can be disassembled (which often involves disconnecting the wheels), while most of the manufacturers do not address this issue at all.
Due to the recumbent position, the driver cannot damp the road shocks as he can do it on a bicycle by standing up on pedals. Roads are often far from ideal and always have some cracks and dents. However, most of the existing models of tricycles have no suspension, or if they do, it is usually very complicated and expensive to make.
A driver of a recumbent tricycle has to keep a side balance and lean his/her body against the seat while making a turn, or while the vehicle is riding on a lateral slope (all roads have it!), or any uneven road where the left or right wheehs jumping up or down. It is quite inconvenient to constantly compensate the imbalance, hold the body by hands and shift the spine left and right along the back of the seat.
Some inventors are trying to solve this problem, but all of their lean systems conducted by hands, which require good muscles of hands and continuous attention of the driver. Keeping the balance becomes a real hard work.
Most tricycles have a handlebar-based steering mechanism copied, in one way or the other, from a bicycle.
Steering a tricycle is a very different process. The driver’s weight is no longer supported by the handlebar and he does not need to keep the balance of the vehicle. In case of a tricycle, the steering deals with much greater forces feeding back from the road that tend to turn the bars. This includes rough roads, uneven braking, and any tilt of the trike. Due to a low ratio of the bike-like steering mechanism (about 1), these forces are transmitted to the handlebars without any reducing and, hence, the driver has to apply a significant effort of hands in order to keep the handlebars stable.
This low ratio also makes the steering too sensitive and requires continuous attention and efforts from the driver in order to keep the desired direction, especially on a high speed.
Besides, the range of a turning angle of the handlebar is very limited, which makes the radius of turning of the vehicle quite large.
Finally, in many cases the turning of the handlebars is pretty awkward, inconvenient and requires a lot of strength of spine muscles.
Most of the tricycles have hand-operated brakes with levers, which are also borrowed from a bicycle.
Having a bigger mass and lower centre of gravity, recumbent tricycle requires a strong and synchronous braking applied to the left and right wheels. Independent braking with two hands cannot be synchronous, and to stop two wheels with one hand would require a lot of muscle strength. Also, having hand brakes means the rider’s hands need to be on them at all times ready to brake in an emergency. Having both hands occupied all the time is not much fun!
So here we are presented with a serious challenge. The hands of a driver are taking care of a number of very important and heavy functions: holding bars to keep the body in balance, moving the bars to steer the vehicle, keeping hands always ready and squeeze hard for braking and, on top of it all, switching the gears from time to time. It would take a lot of concentration of the mind and muscle power in case you are suddenly have to perform more than one of these functions at the same time. The hands and arms are just overly busy. It’s no wander that it’s mostly strong men that are interested in this type of a vehicle. Having a sip of water or holding a phone would be too dangerous.
6. LIMITED USAGE.
Most modern tricycles are designed for a single driver with maximum a basket to carry small amount of goods. For any special purpose we see a whole special trike designed and built (tandem, passenger, cargo, electric, etc.) and the transformation of one type of tricycle into another is not provided. This significantly limits the scope of use of tricycles, when in fact, they have many advantages and can be used to perform many great functions in the fields of transport and entertainment.
So, keeping in mind all above-mentioned problems and a relatively high price of trikes, there is really no that huge of a reason to own a tricycle. That is why they are not popular.
OUR NEW MODULAR RECUMBENT TRICYCLE DOES NOT HAVE THESE DISADVANTAGES.
All problems are solved the easiest way possible:
- MRT (Modular Recumbent Tricycle) can be folded or disassembled for storage and for transportation inside a car.
- MRT has a simple and comfortable spring-suspended seat, that keeps the position of the driver in balance all the time.
- Tricycle has a car-style steering mechanism with a simple cable reducer that provides with easy and precise steering. The radius of turning of the vehicle is minimal.
- MRT has a leg-operated back-pedaling braking mechanism. This way, braking becomes much easier, simultaneous to all three wheels, more efficient and hands-free.
- Our MRT is a multifunctional vehicle with variety of configurations. It comprised of a set of basic modules and variety of additional modules, which can be easily (and without any tools) connected together in desired configuration.
All of these ideas are new and no one ever used them before!
MRT is very easy to drive. It is convenient for storage and transportation. The driver uses his/her hands only for steering (two fingers should be enough) and switching gears. The torso and neck are relaxed. Only legs need to work hard to turn pedals and brake.
A few adjustment are available: position of the seat and rigidity of the seat suspension, positions of headrest, steering wheel, and pedals.
It can be used by a whole family.
Our prototypes of MRT are made very simply at the available facilities just to try out the basic ideas; and they are running so well!
MRT has unlimited potential for further development. With use of the newest technologies and materials there is a great opportunity for engineers and designers to create much better looking, lightweight and reliable vehicle, and also create more modifications for different groups of users (for kids, women, people with health challenges, etc.)
This tricycle does not have any complicated parts. Our prototypes are built of standard components of conventional bicycles. The design promises relatively simple and inexpensive manufacturing, easy maintenance and replacement of parts. Comprised from compact modules, the vehicle is very convenient for manufacturing, selling and shipping.
DETAILED DESCRIPTION of Modular Recumbent Tricycle
Now we have two available PROTOTYPES of the MRT. All parts of the vehicles shown in pictures are handmade with the available equipment and designed as simply as possible.
You have a great opportunity to create much better vehicle!
1. MODULAR STRUCTURE OF TRIKE.
Modular Recumbent Tricycle comprises of basic modules, cross tubes, a seat and, optionally, additional modules. All modules have standardized dimensions, connection and operation and are connected together by a set of cross tubes. Each module has fast operated clamping devices that attach the module to cross tubes. The length of the cross tubes can be variable, so the width of the vehicle can be increased in order to accommodate whatever additional modules were chosen for a particular task. The variety of additional modules is virtually unlimited. It takes just minutes and no tools to assemble a trike of desired configuration.
The basic set of modules has middle, left and right modules. Middle module comprises front and back parts, coupled with a folding device. Due to the folding device, front and back parts can be fixed straight for driving, folded for storage or separated for transportation. Left and right modules comprised of a frame and a wheel with brakes.
For storage of the vehicle, all additional modules and the seat should be disconnected. The middle, left and right modules can be shifted close to each other; the middle module can be folded. Also possible to store the trike vertically – just raise the front end and the trike will stand on two back wheels and rear support.
For transportation inside a car, the seat and all modules should be disconnected from the cross tubes. The middle module can be folded or disassembled into two parts.
The power transmission is similar to bikes. Rotation from the pedals transmits by the chain to the rear sprockets with derailleur and then through differential (or “quasi” differential) and intermediate shaft(s) – to the wheel(s).
Benefits of Modularity:
1. Expanding the area of usage. Depending on the current task a vehicle of desired configuration can be assembled within just a few minutes and without any toos. The examples are: transportation of people (additional drivers or passengers), transportation of goods (through a basket, box, bags, or a platform), use of an engine (gas or electric), attachment of a sail for long distance rides, coupling of two or more trikes and trailers.
2. Modularity, unlike transformers, involves the removal of structural elements that are not needed at the moment. This allows keeping the weight at minimum, which is very important for a human powered vehicle.
3. Ability to adapt to the special driving conditions: high speed – make the vehicle wider, rough road – change the springs, strong wind – use a sail, rain – put rain hood, sun – use the canopy.
4. Ease of upgrade. Modular structure allows user to upgrade the vehicle by adding new modules, as well as by replacing any broken modules, while keeping the core parts.
5. Ease of repair or replacement by modules.
6. Disassembling into compact modules for storage and transportation in the car.
7. By-modules production (even at different factories, agreeing only on a few basic dimensions/standards), compact transport from producer to consumer, by-modules sale.
We have built two different prototypes of the MRT. The first, earlier version has a smaller distance between the cross-tubes - less than the diameter of the wheels (side view). In the second version, the cross tubes are outside of the wheel and allow for fast connection of additional modules from outside of the vehicle. The newer version also has unfolding multifunctional seat and other improvements.
Each module has fast operated clamping devices for fixing modules to the cross tubes. Each clamping device comprised a channel, welded to the module, and two clamps for fixing the ends of the channel to a cross tube. This design is simple, lightweight, and provides a very strong connection. We made two kinds of clamps: one is fast but not adjustable, the other is a little heavier, slower to fix, but adjustable.
The vehicle can have two or more serially linked sections, similar to a train, with two or more drivers. From the same modules you can also assemble a trailer of variable configuration.
Any recumbent tricycle needs a spring suspension (due to a passive sitting position of the driver). One way to make it is a full and independent suspension for all wheels. Unfortunately, this a very complicate and expensive way. We have found and alternative way, which is very simple and inexpensive to make – we suspended only the seat. The seat is free to move not only up and down, but it also now has a freedom to lean from side-to-side and always come back to a vertical position just by the force of gravity.
Modular recumbent cycle has an original “two-point” spring-suspended and leaning seat. Long rear springs allow damping straight up vertical shocks together with side-load forces that affect the upper part of the driver’s body and his/her head when one of the side wheels runs onto an obstacle and the cycle leans sharply. The seat suspended in such a way that the line of the suspension is higher than the center of mass of the sitting driver. Therefore, the seat with the driver always stays about the vertical position even when the vehicle rides on a lateral slope; or leans left or right while turning.
This kind of suspension allows having a real-working head-rest, which is very important, because recumbent position of the driver makes difficult keep head vertically.
The strength of the rear springs and their connections can be variable depending on driver’s weight and desired level of tilting of the seat. Position of the seat adjusts by the length of a telescopic rod. Additional advantage: this rod takes all of the push-pedal force, so the frame tube is unloaded from this kind of bending force.
The front point of the seat has a hook and a spring suspension with adjustment.
Besides the comfort, such suspension allows to keep the tires at a high pressure for easier ride.
The seat is removable. It can be supplied with a seat belt.
3. STEERING MECHANISM.
Understanding that the bike-style steering bar does not work for recumbent tricycles (especially in case of our suspended seat), we chose a car-style steering mechanism. The only task was to make a good high-ratio reducer. Instead of the traditional gear box (which is heavy and expensive) we’ve made a cable reducer, improving its design step-by-step.
MRT has a car-style steering mechanism comprising a steering wheel, and a simple, compact and lightweight cable reducer.
Primary shaft of the cable reducer rotates inside the threaded bushings. The front end of the shaft threaded in order to guide the winding of the cable and, at the same time, to move the shaft lengthwise keeping the tension of the cable stable. The middle of the cable is fixed inside the hole of the shaft; two ends of the cable are attached to the front of a secondary pulley by a screw. The cable tension bolt is located on the bottom side of the pulley. Two idle rollers direct the movement of the cable.
The high ratio (about 8) reducer allows for easy and precise steering of the vehicle at any speed and in any road conditions (in fact, two fingers of one hand are enough to keep the desired direction!).
The amplitude of turning of the front wheel (from+90 to -90 degrees) makes the vehicle very manoeuvrable.
Position of the steering wheel has two adjustments: closer or farer from the driver, and higher or lower. The universal joint at the front allows for the steering wheel to be lifted up for driver’s in and out.
4. BRAKING MECHANISM.
After observing other models of tricycles we decided to transfer the braking function from hands to legs. Since the start of using of multi-speed gearing in bicycles, many have tried to invent a leg-operated braking mechanism. This turned out to be a challenge, because of the after-brake-releasing and reverse-driving mechanism. We experimented with an ordinary freewheel and got good results. The brake is releasing itself! We decided to leave the reverse-driving, since our steering mechanism can turn 180 degrees.
MRT has original simple leg-operated back-pedaling braking mechanism with ordinary calliper or disk brakes to two or all three wheels. The main part of the braking mechanism is a modified freewheel, fixed to the left lever of the crankshaft. Back turn of pedals engages the ratchet mechanism of the freewheel, reels on the pulling chain and pulls the brake cables. Due to significant sum of gaps inside the transmission and long and loose chain spans, releasing the brakes happens by itself, because the angle of the initial pedal’s turn is enough to release the brakes before the chains stretch up wheels start to run.
This braking system does not allow the vehicle to reverse. This feature can be useful for applying a parking brake - just enough to move the vehicle a little back.
The releasing device is used in case the brakes are squeezed tightly.
Leg-operated braking, in case of a tricycle, is much easier and much more efficient. It does not only increase the safety of driving, but also relieves driver’s hands from hard work, thus making the riding of the tricycle a lot more comfortable.
Modular Recumbent Tricycle chain transmission is similar to any other tricycle transmission.
The chain transmission of Modular Recumbent Tricycle is borrowed from a bike, but we added a couple special features.
Rotation from the crank set and chain is transmitted to the wheel(s) via the intermediate shaft(s). In shown prototype we used the simplest option – a piece of square tube (few pieces of different lengths for different configuration). It can be replaces by a fancier version – a telescopic tube and with plastic or rubber elements for better friction.
“Quasy” differential gear is made of two freewheels, each fixed to the shafts of both wheels.
The crank set base can be set in 2 fixed positions on the frame tube to adjust to driver’s leg length (finer adjustment is done by moving the seat). Relevant length of the chain can be gained by adding or removing short pieces with connecting links, or by additional looping of the chain.