The Implementation of a Retrofit Kit for a Life Cycle 9500HR

Michael J. Scott, PhD and Michael Coughlin, BS
RecTech – University of Illinois at Chicago Department of Mechanical and Industrial Engineering
Chicago, IL 60607


This paper presents a construction manual for the retrofit kit of a Life Cycle 9500HR previously constructed and presented by Scott and coauthors. The original goal of the 9500HR retrofit project was to make cardiovascular fitness equipment more accessible to individuals with disabilities; the construction manual presented here is a key step toward achieving that goal. The construction manual is easy to understand and simple to implement. It consists of two sections, a machining section that describes how to construct the components that are not purchased off-the-shelf, and an assembly section that describes how to install the machined and purchased components on the existing fitness equipment. The assembly section is accessible to anyone with a basic competency with hand tools; the machining section requires more technical expertise, but is still within the reach of many do-it-yourselfers.


Universal Design, Cardiovascular Fitness, Recumbent Exercycle, Life Cycle 9500HR


This paper presents an installation manual developed to enable the more widespread implementation of a retrofit kit developed previously for a Life Fitness recumbent exercycle [1]. The motivation for the manual to retrofit the Life Cycle 9500HR comes from the lack of universally designed cardiovascular exercise equipment in the market today. If a patron of a health care facility with a lower extremity disability wants to get an aerobic workout he or she may have choices such as arm ergometers or hand cycles that have been linked to problems such as overuse injuries for manual wheelchair users [2-8], or no choice at all. Most health care facilities delegate space for machines based on how many people can use that space. By retrofitting an existing Life Cycle 9500HR with this kit, both the patron and the health care facility win. The patron is able to get an aerobic exercise without overworking certain muscles and the health care facility saves valuable floor space.

The manual was written and designed for someone with limited machining experience. The manual has two parts. The first part describes what pieces are needed and how to machine those pieces. The second part describes the assembly of those pieces. In the machining section, templates are provided to ensure proper spacing and dimensions. Almost all of the machining can be done with a drill, vise, screwdrivers, and hacksaw; the two required tools that are not in most home workshops, a tap and a reamer, are relatively inexpensive. This makes the machining simple enough that it can be done at home with basic tools. The assembly section has several pictures to help ensure everything is in the correct place.


The decision to retrofit an existing aerobic exercise machine was driven by several factors [1]. Preliminary research determined that there was a particular lack of aerobic fitness equipment for people with lower extremity disabilities: “The disparity is even more pronounced when one considers fitness equipment: while there are problems of access for both types of equipment, more strength training equipment than cardiovascular equipment is accessible to wheelchair users.” [1] This led to a decision to retrofit an aerobic machine rather than a strength machine. There were also new laws and regulations being passed in Europe requiring health care facilities to be more accessible to people with disabilities. The most comprehensive of these was the Inclusive Fitness Initiative, or IFI [9], in Great Britain, which forced fitness companies to have accessible fitness equipment in order to be eligible for government contracts. The IFI continues to be a driver of accessible design of fitness equipment.

In designing their prototype, Scott et al. employed a universal design process similar to other design processes being used today. They conducted interviews to determine the customer's needs. Then the House of Quality method [10] was used to turn those needs into design requirements. In order to determine what physical motions do not create risk for overuse injuries, like the arm ergometer does, biomechanical research was conducted to identify motions that did not use the same muscles as wheelchair propulsion.

Once the design requirements and the desired motions were determined Scott et al. began to design the prototype. After the design was complete, the prototype was tested to confirm that the design requirements were met and the desired motions were achieved. It remained only to implement a mechanism to share this design with the public.

It was determined that the best way to achieve the goal that was outlined at the beginning of the project, making aerobic exercise equipment more accessible, was to make an assembly manual that could be read, understood, and implemented by a large number of people. In order to make the manual easy to read and understand it was important to keep the language simple, define the sections clearly, add templates to make some of the machining steps easier, and include pictures of the assembly at certain points. The two biggest sections were the assembly and machining sections.


The machining section describes how to take stock parts and machine them into all the plates, flanges, hubs, sprocket, shafts, etc. that comprise the assembly. Staying true to the goal of making the manual easy to implement, all of the work in this section can be done with simple tools. Scale templates are included so that the user can be sure he/she is making the correct cuts, or drilling at the correct spots. An excerpt of the machining section is included in figure 1, and describes the machining steps necessary to make the mount plates of the core mechanism. To ensure that the holes are drilled at the correct locations and the cuts are the right distance apart the mount plate template, figure 2, is included. The entire machining section can be found at the University of Illinois at Chicago RecTech website (

1.1 Mount Plate
The mount plate is used for mounting the core mechanism to the bike. The following procedure describes how to drill and tap the necessary holes. The following section also describes how to press fit the sleeve bearings into the shaft holes.

  1. Drill the mount plate holes.
    1. Make sure the template is to scale. Some printers may not print this image to scale. Confirm that from line X to line Y on the template is 8 1/2
    2. Tape two 81" by 41" by 1/8" aluminum plates tape them together, and tape the template (see Figure 2) to them.
    3. The first holes that need to be drill are the 5/8" sleeve bearing holes. Use a 39/64" drill hit for this. (These holes are designed so they can have bearings can be press fit. into them.)
    4. Next drill the two number ten through holes at the holes next to A and B on the template
    5. Drill and tap the six number 10 holes at the intersections next to all to D and T points. These holes are for attaching the mount plates to the cover plates.
    6. De-burr the holes.
  2. Press the sleeve bearing into the mount plates.
    1. The holes should have a diameter of 39/64"
    2. Measure the actual outer diameter of the sleeve bearings, and find the smallest diameter.
    3. Set the reamer to 5/1000" smaller then the smallest sleeve beating.
    4. Ream out all four holes with the reamer set to 5/1000" smaller then the smallest sleeve beating.
    5. Press the bearings into the mount plate holes.
    6. Measure the two shafts.
    7. set the reamer to the larger shaft size.
    8. Ream out all four sleeve bearing. (The the sleeve bearings shrink when they are press fit into the mount plates).

Figure 1: Sample Machining Directions


    This is the mount plate template that is tapped to the stock aluminum after it is cut to the correct dimensions. There are marks on the template where the holes need to be drilled.Figure 2: Mount Plate Template (Click for larger view)

    The assembly section gives a detailed description of the steps necessary to take the previously machined parts and construct the retrofit kit for the recumbent bike. In order to make the assembly easier, pictures are provided after some of the more difficult steps. The assembly section only requires a few box-head wrenches and screwdrivers. It may be possible in the future to provide the user with all the machined parts to perform the assembly section. This would allow a wider range of people to implement the retrofit kit. Figure 3 is an excerpt from the assembly section of the manual, and describes how to assembly the small shaft of the core mechanism. The small shaft assembly is the small sprocket, mount hub, wood pulley, drive pulley flange plate, and the drive pulley cover plate. Figure 4 is a photo of the assembly after the drive pulley flange was attached. The entire assembly section can also be found at the University of Illinois at Chicago RecTech website (


    2.1 Small Shaft

    The first thing to assemble is the small shaft. The small shaft goes through the upper holes of of the mount plate. The small shaft get the drive pulley and the large sprocket set onto it.

    1. Mounting Hub
      The mounting hub is the small steel hub that goes on the inside of the drive pulley and connects the wood hub. the drive pulley flange plate, and drive pulley cover plate to the small shaft using two set screws.
      1. Slide the mounting hub onto the small shaft.
      2. Fix mounting hub to shaft using set screws. (At a distance according to the diagram) Make sure the set screws are against the flats that you ground on the shaft..
      3. Put a drop of blue lock tight on the set screws.
    2. Drive Pulley Cover Plate
      The drive pulley cover plate is the circular plate with one bolt circle that is used to connect the cover plate to flange plate and wood pulley.
      1. Slide the cover plate onto small sprocket.
      2. Slide small sprocket and cover plate assembly on to the small shaft. (The hub of the sprocket should face the mounting hub)
      3. Set the small sprocket with set screws according to the diagram. (In order to get the proper spacing put a 0.047" spacer between the mounting hub and the small sprocket.)
      4. Figure 16 is a photo of the assembly up to this point.

    Figure 3: Sample Assembly Directions

    The construction manual described in this paper is an important step in making aerobic fitness equipment more accessible. This manual can be a useful tool for fitness companies who wish to design equipment that fulfills IFI [9] standards. The details of the design process undertaken by Scott et al. are described in Srinirayanprasaadh Srinivasaraghavan's master's thesis [11]. Mr. Srinivasaraghavan’s research also led to the design of the fairlead mechanism. The drawings of the fairlead are also available at the UIC RecTech website.

    This paper reviews the motivation for retrofitting a Life Fitness Life Cycle 9500HR. It gives background on the design process undertaken by Scott et al. in the original work: for instance, people with lower extremity disabilities have a difficult time getting a cardiovascular workout for several reasons, one being a shortage of appropriate aerobic exercise equipment. Even though there is a shortage of both aerobic and anaerobic exercise machines the number of accessible anaerobic machines is much greater. For these reasons Scott et al. choose to retrofit an aerobic exercise machine.

    The design process undertaken by Scott et al. involved a detailed study to determine the best, least harmful, motions that a person with a lower extremity disability could perform to get a cardiovascular workout. That study is also in Srinirayanprasaadh Srinivasaraghavan's Master's thesis [11].

    The manual was created while constructing the second prototype of the design, and is accessible to the public at the UIC RecTech website provided above. While creating the second prototype, every step was explained and studied to make sure the directions were as descriptive as they needed to be. It was extremely important to make the manual easy to read and understand, because the more people that are able to implement the design the closer we are to our goal.


    1. Scott MJ, Srinivasaraghavan S, Vomvoridis G, Hirsh M, Weston P (2006). Modification Kits for Retrofitting Exercise Equipment. Proceedings of the RecTech State of the Science Conference.
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    3. Lathrop D (1996). The challenge of keeping fit after rehab are taken on by those who need it. Rehabi Man. 9(2): 58-59.
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    5. Veeger HE, Rozandaal LA (2002). Load on the shoulder in low intensity wheelchair propulsion. Clinical Biomechanics. 17: 211-18.
    6. Fullerton HD et al. (2003). Shoulder pain: a comparison of wheelchair athletes and non-athletic wheelchair users. Medicine and science in sports and exercise. 35(12): 1958-61.
    7. Rudins A et al. (1997). Kinematics of the elbow during wheelchair propulsion: a comparison of two wheelchairs and two stroking techniques. Arch Phys Med Rehab. 78(11): 1204-10.
    8. Olenik LM, Laskin JJ (1995). Efficacy of rowing, backward wheeling and isolated scapular retractor exercise as remedial strength activities for wheelchair users. Paraplegia. 33: 148-52.
    9. Inclusive Fitness Initiative,
    10. Hauser J, Clausing D (1988). The House of Quality. Harvard Business Review, 66(3):63-73.
    11. Srinivasaraghavan S (2007). Development of a Retrofit Kit for a Cardiovascular Fitness Equipment. MS Thesis, UIC.
    12. Vomvoridis G (2006). Ergonomic aspects of retrofitting an indoor recumbent cycle to accommodate wheelchair users. MS Thesis, UIC.
    13. Srinivasaraghavan S, Vomvoridis G, Hirsh M, Weston P and Scott MJ (2006). Development of mdification kits for cardiovascular fitness equipment. RESNA 2006, platform session honor student scientific paper.


    This project was partially supported by awards H133E020715 and H133E070029 from the U.S. Department of Education, National Institute on Disability and Rehabilitation Research. Any opinions expressed in the paper are the responsibility of the authors and do not necessarily reflect the views of the sponsoring agency.

    Author Contact Information:

    Michael J. Scott, PhD, UIC MIE (MC 251), 842 W. Taylor St., Chicago IL 60607, Office Phone (312) 996-4354 EMAIL: