Friday, January 29, 2010
Wednesday, January 27, 2010
The rear rider will be powering the rear wheels by way of the main bike bottom bracket drive system. The rear wheels will be attached on a through axle mounted in the two sets of drop outs in back.
The front rider will power the front wheel with a direct drive, much like a children s tricycle. Drawings and 3d model to follow.
Our Community Bikes on Main has been able to hook us up with components and goodies that will make this whole process easy peasey
Sunday, January 24, 2010
Thursday, January 21, 2010
M. Steel Cycles
Tandem Bicycle to Tandem Trike Convertible
A Newton tandem tricycle conversion, but that's not all....
This was a job undertaken for one of our customers who wanted a little more stability. As the tandem already had S&S couplings it seemed logical to utilize them to fasten the tricycle conversion on. This was certainly one of the more 'interesting' jobs we have tackled.
The tricycle front end is held on with S&S couplings. This allows the normal front end to be replaced should the customer require it.
3 nuts, 3 cable connectors and off it comes.
The Adventurer Tandem, model ATP 2600, is a tandem tricycle designed for use by adults with mobility, balance, or neurological disabilities. This tandem cycle features a tubular steel frame, a wide rear stance for added stability, seven speeds, and two seats. The driver steers and controls the cycle from the rear, and the person with a disability sits in the front. The front seat and the front handlebar height are adjustable, and the front handlebar can be moved out of the way for dismounting. The front seat is available with a seat belt in low- and high-back models. The cycle also features a crank and sprocket that can be adjusted to accommodate different hip and foot positions. Other features include locking hand brakes and quick release bolts for disassembly and transport. This cycle accommodates riders with 22-inch inseams. DIMENSIONS: The cycle has a 40-inch rear stance
Most tandems are set up so that the stoker's and pilot's cranks and pedals are syncronized. When the pilot's left crank is at the top of its rotation, the stoker's left crank is also straight up. This condition is called having the cranks "in phase."
Some tandemists prefer a different setup, in which the cranks are "out of phase." The most common alternate setup is for the pilot's cranks to be horizontal while the stoker's cranks are vertical. This is called "90 degrees out of phase" because the cranks are at a 90 degree angle to one another. If the captain's cranks are 90 degrees forward of the stoker's cranks, we say the captain's cranks are leading by 90 derees.
In phase Out of phase Both riders move together, for more of a "team" feel.
Slow-speed handling is better.
Less risk of striking a pedal on the road while turning, because both inside cranks can be in the up position at the same time.
Power is applied to the wheels in pulses. When both cranks are vertical, little power can be applied, which can cause the tandem to stall in a steep climb.
Standing to pedal is easier when both riders move together.
Riders move differently from one another, as each is in a different part of the power stroke.
The pilot must remember where his stoker's pedals are in a turn.
Power is applied in a smooth flow, because while one set of cranks is at dead center, the other is in the heart of its power stroke.
This can help in steep climbs, and also reduces stress to some drive-train parts, since both riders are never applying full power at the same time.
"There are essentially three entities riding a tandem:
The captain, the stoker, and the spirit.
It is the spirit who likes in-phase cranks."
Cranks and Cadence
Any tandem team needs to come to terms with the cadence issue. With practice and patience, most couples can work this out on a standard tandem. Some teams, particularly those who are not well-matched in leg length or pedaling style may need to go to a technical fix.
The simplest way to accommodate disparate cadence preferences is to install different length cranks for the stoker and for the pilot.
In general, for any given rider, the shorter the cranks are, the easier it becomes to spin a rapid cadence. If the rider who prefers a faster cadence gets longer cranks, this will develop a preference for a slightly slower cadence. If the rider who prefers a slower cadence gets shorter cranks, it will become easier to pedal at a faster rate. The most common crank length is 170 mm. This is what comes stock on most tandems. If you find that you have serious cadence incompatibility, start by installing 175 mm cranks for the rider who wants a faster cadence. If this helps, but not enough, get 165 mm cranks for the rider who has trouble pedaling fast.
Note, changing the crank length doesn't directly change the cadence, and both riders will still be pedaling at the same cadence, but the longer cranks will encourage the "spinner" to slow down a bit, and the shorter cranks will make it easier for the "slogger" to keep up.
Independent Gearing/Coasting.But what about giving each rider the option of shifting to a different gear than that used by the other? What about giving one or both riders the option of coasting while the other continues to pedal?
Both of these options are possible, and available, but not on standard tandems. With tandems of conventional geometry, the cranks must move at the same speed, because if not, the time will come when one the pilot's left crank is pointing backward, while the stoker's left crank is facing forward, and their feet will collide!
To make independent gearing/independent coasting work, you either need a tandem with a longer than usual spacing between the riders, or a recumbent.
Independent gearing/independent coasting does add to the complexity and weight of a tandem, but for some riders it is worth the cost.
Wednesday, January 20, 2010
Tuesday, January 19, 2010
Further information: Spring rate
The spring rate (or suspension rate) is a component in setting the vehicle's ride height or its location in the suspension stroke. Vehicles which carry heavy loads will often have heavier springs to compensate for the additional weight that would otherwise collapse a vehicle to the bottom of its travel (stroke). Heavier springs are also used in performance applications where the loading conditions experienced are more extreme.
Springs that are too hard or too soft cause the suspension to become ineffective because they fail to properly isolate the vehicle from the road. Vehicles that commonly experience suspension loads heavier than normal have heavy or hard springs with a spring rate close to the upper limit for that vehicle's weight.
Travel is the measure of distance from the bottom of the suspension stroke (such as when the vehicle is on a jack and the wheel hangs freely), to the top of the suspension stroke (such as when the vehicles wheel can no longer travel in an upward direction toward the vehicle). Bottoming or lifting a wheel can cause serious control problems or directly cause damage. "Bottoming" can be either the suspension, tires, fenders, etc. running out of space to move or the body or other components of the car hitting the road. The control problems caused by lifting a wheel are less severe if the wheel lifts when the spring reaches its unloaded shape than they are if travel is limited by contact of suspension members.
Damping is the control of motion or oscillation, as seen with the use of hydraulic gates and valves in a vehicles shock absorber. This may also vary, intentionally or unintentionally. Like spring rate, the optimal damping for comfort may be less than for control.
Damping controls the travel speed and resistance of the vehicles suspension. An undamped car will oscillate up and down. With proper damping levels, the car will settle back to a normal state in a minimal amount of time. Most damping in modern vehicles can be controlled by increasing or decreasing the resistance to fluid flow in the shock absorber.
See dependent and independent below.
Camber changes due to wheel travel, body roll and suspension system deflection or compliance. In general, a tire wears and brakes best at -1 to -2 degrees of camber from vertical. Depending on the tire and the road surface, it may hold the road best at a slightly different angle. Small changes in camber, front and rear, can be used to tune handling. Some race cars are tuned with -2~-7 degree camber depending on the type of handling desired and the tire construction. Oftentimes, too much camber will result in the decrease of braking performance due to a reduced contact patch size through excessive camber variation in the suspension geometry. The amount of camber change in bump is determined by the instantaneous front view swing arm (FVSA) length of the suspension geometry, or in other words, the tendency of the tire to camber inward when compressed in bump.
I've e-mailed the builder of these trikes. He thinks we need to have 4 wheels. He said
"if you want to make a tandem where you sit one behind the other you may be able to use them. a side by side trike would require a completely different approach. if you are on trails you would be better off with 4 wheels to distribute the load over the softer trail. you are not on a hard surface. you could add bigger brakes like a go cart brake on the rear axle. remember you will have the weight of 2 people and the weight of the quad to stop."
I've got the plans, so we can adapt parts.
Saturday, January 16, 2010
This calculator finds the "optimal high speed trail" for a specific design. Note that in many cases this may be more trail than is practical for general use. A trail value greater than 5 inches will generate excessive fork flop. The trail calculator should be used as a design aid to give you a good idea of how changes in your bikes geometry effect the need for additional trail. This equation is still being developed. Calculator updated 9/11/06 to provide more realistic trail values. Personally I feel that the numbers generated with the "Jet Fighter" K5 value are the best for me. YMMV.
Thursday, January 14, 2010
Compact-ish – to fit in box, but can expand upon assembly
Easy Assembly – some mechanical joining on competition day
Lightweight Materials – aluminum, cro-molly : ) etc.
Stability - wide wheel base, 3 to 4 wheels, good suspension, low center of gravity, thick tires with heavy tread
High Torque – large tires with heavy tread, recumbent seating with long pedal throw, standing & stepping on long lever throw
Wheelchair Option – to accommodate for friends with spinal cord injuries, and because using your hands & arms is fun!!!
A hand-drawn sketch will be coming soon! For now, the idea is a FWD Recumbent Trike with RWD Stepper. Here’s the design break-down:
FRONT WHEEL (CHAIN) DRIVE, DELTA RECUMBENT TRIKE
- 3 wheels
- wide wheel base created by 2 non-turning rear wheels
- low center of gravity, recumbent = low to ground
- thick tires with heavy tread
- good suspension (option for complete-frame-suspension … See Resources!!!)
- high torque - bent knee to stretched leg pedaling, long pedal throw
- large tires with heavy tread
- 2 rear non-turning wheelchair wheels
- A larger front wheel for better turning and utilization of torque from recumbent power
(think “Big Wheels” like when you were a kid…)
- Front Driver controls steering and all-wheel-braking system
- Free-wheel pedaling
Front Wheel Drive Trikes
Full-frame suspension FWD Trike *PLANS* - SEE “Tadpole Plans.pdf”
REAR WHEELS (CHAIN) DRIVE, STEPPER
- Only pedals & standing bar added to recumbent design
- Only pedals & standing bar, NO SEAT OR ADDITIONAL FRAME! : )
- Near wide wheel base at back
- Low Center of Gravity… person can duck down when necessary
- Large step-panels for feet
- Rigid standing bar to hang onto
- bent knee to stretched leg stepping
- can use full body weight into each step
- Free-wheel pedaling
- Wheel base large enough for stability, but compact enough for efficient wheelchair use
The “Randy Ross 3G Stepper” (2:13-2:20) looks like bike pedals are round roller bars (moving backward?), and foot boards made of pressed-ply Canadian Maple with metal track/roller bar-guide underneath
Ross Concept- ion Interview
Stepper Construction Manual
Also an idea,
EliptiGo Glide Bike