Bike Rodeo bicycle blender

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Revision as of 08:06, 18 May 2011 by Jthiller (talk | Contributions) (Changed wording tense.)
Engr305 Appropriate Technology page in progress
This page is a project in progress by students in Engr305 Appropriate Technology. Please do not make edits unless you are a member of the team working on this page, but feel free to make comments on the discussion page. Check back for the finished version on May 15, 2011.


A Bicycle Rodeo, or Bike Rodeo, is a bicycle safety event for children, generally ages 6-14. Events can include lectures, workshops, inspections, demonstrations, and generally a practice course. Several rodeos are held each year by Humboldt County, California health organizations.

Opportunity Definition

As an attraction for these events, workshop coordinator Brian Olson, of Rio Dell Community Resource Center for the St. Joseph Health System, has teamed up with Robert Camacho and Eric Recchia of Humboldt State University’s Engineering 305 class on Appropriate Technology to create a bicycle blender. A bicycle blender uses human pedal power to operate a blender. The blender will be used by kids attending the event to demonstrate the uses of pedal power and allow them to make their own smoothies.

Literature Review


In physics, a calorie is the amount of heat required to raise one kilogram of water by one degree centigrade. In nutrition, a Calorie is 1000x the physics calorie, also known as a kilocalorie, however it is still referred to as a “calorie”. When people eat food that contains Calories, they store these calories for later use, such as pedaling a bicycle or stationary bike blender. It is when they pedal a bike that they convert the stored calories into heat and work. [1] A person pedaling a bicycle can accelerate to a speed and maintain it comfortably for a long period of time. This is referred to as “pacing.” Beyond this point, a riders’ velocity may reach high speeds, however the amount of energy required to keep up rapidly increased to a point where all energy from the rider is used up. This is because the amount of energy needed to keep the RPM’s (rotations per minute) of the crankshaft up has exceeded the amount of energy the rider can actually produce and expend. These points vary according to each rider’s skill and athletic condition. [2]

The bike itself works off of two gears or sprockets. One gear is under the rider’s feet and is called the crank sprocket. This is where the pedals connect by way of the pedal arms. The other sprocket is attached to either the rear wheel (mobile bike) or the front wheel (stationary, exercise bike) and is referred to as either the rear sprocket or rear sprocket. In general, the gear under the crank sprocket has more teeth (grooves for the chain to fit in) then the other sprocket. A gear ratio can be determined by dividing the amount of teeth the crank sprocket has by the number of teeth the rear or front sprocket has. For example, if the crank sprocket has 48 teeth and the front sprocket has 13 teeth, the gear ratio is 48/13 or 3.69. This means that for every rotation of the large gear, the small gear rotates 3.69 times. [3]

Design Considerations

Maximum Power Output

According to ergometer tests conducted by Grosse-Lordemann and Muller, max power output for a 34 year old male who is not an athlete is about 110 watts at 80 rpm and 160 watts at 40 or 50 rpms sustained for 10 minutes. [4] A test conducted by students at Dartmouth College found that for an untrained average adult male, an output of 37 watts can be sustained for an indefinite period of time at 65 rpm, and an output of 71 watts can be sustained for 60 to 120 seconds at 90 rpm.[4][5] Another study found that peak average output of subjects was 142 watts for periods of more than 60 minutes. [4][6] In a study done on professional cyclists [4][7], and on estimates made from UCI record holders[8], professional athletes can generate more than 400 watts for periods of at least an hour or more. In a related experiment, Renzo Sarti, an Italian sprinter, was able to produce 1,644 watts for 5 seconds. [9] Variations in power output are likely due to the ability of the test subject and testing conditions, such as the equipment, quality of bike fit, and riding posture.

Preferred Cadence

Cadence on a bicycle refers to the number of rotations per minute of the crank. Cadence is related to power output because power output is a function of force applied to the pedals and cadence, this relationship being: Power (watts) = Pedaling speed (m/sec) * Thrust force (newtons). Cadence can’t be directly related to power output, as different crank arm lengths will yield different pedaling speeds for a given rpm. According to a study done on trained bicycle racers by Coast, Cox, and Welch, optimal efficient pedal rate over a 20 to 30 minute period is between 60 and 80 rpm. At 80 rpm, perceived exertion and lactate levels were lowest. [9] [10]

Saddle or Seat

The seat can be adjusted by loosening a clamp bolt with a crescent wrench. There is also another bolt for adjusting the tilt of the seat. These two points may become weak with more riders of varying sizes and should be inspected and replaced when necessary. It is suggested that at least 2 ½ inches of the seat post are should remain in the seat tube at all times. For taller riders, it is possible that this recommendation will not be followed and possible breakage of the seat or seat post could result. This recommendation should always be followed to prevent this. [11]

Types of Bike Blenders

Different types of bike blender designs are available for purchase and/or duplicating with fabricated parts.

Type 1 - Stationary Mechanical

This design is where the fly wheel of an exercise bike turns a skateboard wheel attached to a drive shaft. This drive shaft directly attaches to the fitting of the pitcher component of a blender. The blender is stabilized with counter like table top mounted in front of the bike. An advantage of this bike is that there are no electrical components involved! This design is purely mechanical which can also be a draw back because of the rarity of parts. Some parts for this design had to be specially designed and fabricated at a machine shop, which can be costly. Also, this parts used for this bike are not weather proof and are subject to rust. The whole design is also somewhat heavy, requiring at least two people to move. [12]

Type 2 - Stationary Electric

This design also modifies an exercise bike by connecting the flywheel to an electric generator with a fan belt. The generator operates at very low RPM’s allowing the rider to power it with ease. An advantage with this generator is that any appliance working off of DC current can be operated not just a blender. A disadvantage is that the generator adds extra weight to the bike. Also, the wiring of the generator must be maintained to insure that the bike operates safely. This design is also not weatherproof. [13]

Type 3 - Mobile

This design involves a stand that attaches to an ordinary bike in a way that elevates the rear wheel off the ground. Once the stand is in place and the rear wheel is elevated, a rider can power the blender by pedaling. An advantage to this design is that the stand and blender are separate from the bike, allowing any bike to be a possible bike blender. The disadvantage is the possible loss in efficiency by not having a stand and blender custom fit for a particular bike. [14]


The following table displays the projected costs for the Bicycle Blender project. Funding has been generously donated by the Rio Dell Parent Teacher Organization. The exercise bicycle has been donated by a friend of the build team. Other parts will be salvaged when possible from the Humboldt State University Bicycle Learning Center. Remaining assembly hardware and supplies will be purchased locally. The projected total project cost is $65.00.

Quantity Material Source Cost ($) Total ($)
1 Stationary Exercise Bicycle Donated 0.00 0.00
1 Blender Arcata Recycling Center - The Reusables Depot Thrift Store 3.00 3.00
1 Bicycle Hub Donated from Revolution 0.00 0.00
1 Blender Support Board Salvaged 0.00 0.00
1 Blender Coupling Angels of Hope Thrift Store 0.55 0.55
1 Misc Assembly Hardware (e.g.: screws, etc) ACE Hardware 1.47 1.47
Total Cost $5.02

Proposed Timeline

March 21st- Complete CCAT bike and test ride/make smoothies. yum! Make adjustments to bike/address new issues.

March 22nd- Create a parts list according to previous bike design, current bike needs. This design may also include any necessary modifications to the previous design.

March 24th- Salvage parts from bicycle learning center.

March 29th-Purchase remaining hardware and supplies from local business.

April 6th- Contact client to notify progress on the bike/any potential concerns that have come up.

April 9th-Assemble bike blender for bike rodeo.

April 16th- Test ride/make smoothies yum! Make adjustments to bike/address new issues.

April 18th- Contact client to arrange transportation of complete bike blender.

Image Gallery

Here are some of the components of the blender along with the (almost) finished product.


Here is a video demonstrating basic safety, maintenance, and repair procedures, and how to operate the Bike Rodeo Bicycle Blender


  1. Krausz, John, Vera van der Reis Krausz, and Paul Harris. The Bicycling book: transportation, recreation, sport. New York: Dial Press, 1982.
  2. "Bicycle efficiency and power -- or, why bikes have gears." User Home Pages. (accessed February 15, 2011).
  3. bicycling fitness program: a complete guide to equipment and exercise. New York: McGraw-Hill, 1985.
  4. 4.0 4.1 4.2 4.3 Whitt, Frank Rowland, and David Gordon Wilson. Bicycling Science. 2nd ed. Cambridge, Mass.: MIT Press, 1982. 42-52.
  5. Report on the Energy-Storage Bicycle, Thayer School of Engineering, Dartmouth College, Hanover, N.H., 1962.
  6. D. R. Wilkie, Man as an aero-engine, Journal of the Royal Aeronautical Society 64 (1960): 477-481.
  7. T. Nonweiler, The work production of man: Studies on racing cyclists, Procedings of the Physiological Society, 11 January 1958. 8-9.
  8. Perry, David. "Bike Cult Book: Online Resource: World Hour Records." N.p., 28 July 2005. Web. 15 Feb. 2011. <>
  9. 9.0 9.1 Abbott, Allan V., and David Gordon Wilson. Human-Powered Vehicles. Champaign, IL : Human Kinetics Publishers, 1995. 34-37.
  10. Coast, J.R., Cox, R.H., and Welch, H.G. (1986). Optimal pedaling rate in prolonged bouts of cycle ergometry. Medicine and Science of Sports and Exercise, 18(2), 225-230.
  11. Call, Frances, and Merle E. Dowd. The practical book of bicycling. New, rev. ed. New York: Dutton, 1981.
  12. "The Pedal Powered Mechanical Blender." Pedal Powered Innovations by Bart Orlando. (accessed February 15, 2011).
  13. "The Pedal Powered Electric Blender." Pedal Powered Innovations by Bart Orlando. (accessed February 15, 2011).
  14. "Bike Blenders - Features | Rock the Bike." Rock the Bike. (accessed February 15, 2011).
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