Phase 3 – Machine Design (Group 11)

The Running Machine

The Running Machine is a cutting edge exercise machine that allows one to closely simulate the running motion while minimizing many of the stresses caused from running. The Running Machine will be ideal for the competitive runner who wishes to supplement a high volume of training yet affordable enough for the recreational jogger to own. The initial target market will likely be commercial gymnasiums and collegiate athletic training rooms.

Performance/Cost Basis of Design:

  • Results from benchmarking in phase 1 and research of inexpensive materials will yield a low cost yet highly attractive and marketable machine.
  • Minor changes have been made to initial design to reach these goals.
  • Links will be aluminum T joints for aesthetic purposes and are consistent with popular elliptical trainers in the market.

Research/Benchmarking:

  • The following web links were referenced for materials selection:
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  • Dimensions of bars were chosen based on a comparison of the length of an actual running stride (from group 6’s bench mark and from standard track and field literature (Jack Daniels, Pete Pfitzinger, USATF.com, Letsrun.com)) to the paths defined in Dr. Keefe’s “path” book.
  • Bars were thick enough to handle the torques and forces applied to them yet thin enough to keep the mass low, thus requiring less torque to operate the machine. See attached calculations for beam analysis of longest link.
  • The flywheel shouldn’t be more than 30 pounds based on research of elliptical trainers and exercise bike. The width and thickness were calculated to satisfy the volume conditions based upon the density of the material chosen (aluminum).
  • T-joint design of the links are based on a similar design found on the endurance elliptical trainer 4.0i (
  • Bearings were chosen based on anticipated load and volume of training. ABCE standards are based on 1 million revolutions, however anticipated volume over 5 years will be 2 million revolutions. A factor of safety was chosen to account for this difference.

Materials Used:

  • Links - Aluminum T-6 6061 with corrosion resistant coating (CLAD).
  • 6061 is easy to find and to machine
  • May be painted or rubber coated in addition for an aesthetic finish
  • Flywheel - Aluminum T-6 6061 with corrosion resistant coating.
  • Is corrosion resistant and has good cost to weight ratio
  • Plastic shield encases drive train and crossing links for safety.
  • Advantage Bearing Technologies radial bearing #1623 (see attached table).
  • Bearings fastened with interference fit, plastic caps to encase housing.
  • Tolerances for bearings and housing are 1/1000, links and wheel are 5/1000.
  • Corrosion resistant coating will be used for both the flywheel and the individual links. Paint or rubber may be used for links.

Potential for manufacturing:

  • Materials to be used for the individual parts and the specific bearings have been listed.
  • As seen in engineering drawings, all parts can be manufactured. Appropriate dimensions are given in the drawings for each part.
  • Machine will be easy to assemble.
  • Parts will be machined and welded from tube stock.

Near Term Path Forward Plan:

To reduce risk when moving toward realization the follow steps will be taken:

  • Research alternative materials (plastic, composites) to improve cost goals. We potentially want to use steel tube caps if aluminum proves to be too brittle.
  • Model machine using computer programs to conduct theoretical tests .
  • Modify design to adapt to any problems seen through computer testing.
  • Build full scale prototype.
  • Test prototype considering weights and forces to be applied to each link.
  • If failure occurs, will locate the area of failure and analyze .
  • Create new plan to correct problem (lower force spikes).
  • Once complete design is working effectively begin to market product publicly.

Individual Contributions:

  • Tom Pepe - Link and assembly drawing in AutoCAD
  • Curtis Pierce - Link drawing in AutoCAD, research
  • Barry Pollock - Research of bearings, editing report, concept drawing
  • Matt Porter - Link design, link drawing in AutoCAD
  • James Powell - Link drawing in AutoCAD, report draft, research