A Pedestal Design for the Total Gym

Transcription

1 A Pedestal Design for the Total Gym Richard E. Elevate your paddlesport training! December 2009 Visit Richard's Website A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 1

2 A Pedestal Design for the Total Gym Contents Project Overview... 3 Bill of Materials, Tools and Suggestions... 5 Pedestal Assembly and Detail Drawings... 6 General Views of the Pedestal... 6 View of the Pedestal and the Total Gym showing Assembly Details... 7 Dimensions of the Base... 8 Dimensions of the Angled Support... 9 Dimensions of the Top Dimensions of the Upright Dimensions of the U-Bolt Some Close-Up Views of the 2 7 / 8 x 4 Pedestal and the Platform Weight Bar Static Resistance Provided by the Pedestal s Height Height & Incline Comparison of the Total Gym 1000 Series and the Total Gym on the Pedestal Graph of the Static Resistance Presented to the User as % of Platform Load and Angle Examples of Static Resistance vs Platform Load and Angle Calculating the Force and Power Required to do the Prone Push-Down Exercise Details of an Example Prone Push-Down Diagram of the Platform Forces Equations for Force and Power vs. Time for the Example Prone Push-Down Exercise Calculating the Force and Power vs. Time from the Platform s Acceleration and Velocity Power Required Per-Person in Tandem Marathon Canoe Paddling Comparison of Power: Example Prone Push-Down Exercise vs. 7 MPH Tandem Marathon Canoe Unintentional but Happy Consequences The seated, single arm lat pull down Appendix A: Photos of the Total Gym 1000 Series Showing Angles and Dimensions A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 2

3 Project Overview The Total Gym 1000 series is a terrific piece of exercise equipment for strengthening the muscles used in the canoe and kayak paddling motion. It allows a large variety of arm motions and requires engaging the torso and back while using the arms. Some people using the Total Gym for paddling-related exercises find that the exercise resistance available in the product is too small. This project provides details of a pedestal that increases the exercise resistance. The exercise resistance comes from the angle of the platform and the weight on the platform. Increasing the exercise resistance can be done either by increasing the platform s angle so that a larger percent of the user s weight is lifted or by adding weight to the platform via attachment of a bar at the bottom edge of the platform for the addition of barbell plates or by doing both. Here are drawings and photos of a pedestal I made to increase the platform s angle and with it the exercise resistance. Along with the increased height the pedestal also improves the lateral stability by increasing the width of the base by 68% (from 16 to 27 ). I have used this pedestal for about three years and I found it is stable and rigid. I m quite happy with it. The motivation for increasing the platform s angle via this pedestal is an alternative to the method used by Mr. Marc Gillespie (principal of Forge Racing). Marc has the upper end of his Total Gym attached to a steel pole in his basement. The pole is a structural support of the house, is about 4 in diameter and is commonly used in house construction in this area. My house also has such support poles but there are none in a location convenient for placing the Total Gym. The finished pedestal looks like this: Notice that this pedestal keeps the vertical orientation of the Total Gym s vertical support. For that to happen, the bottom end of the diagonal support is kept in nearly its original location relative to the floor and relative to the axis of the vertical support. In the photo above you can see the diagonal support has its lower attachment point moved down to the base of the pedestal from its original position on the Total Gym s vertical support. A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 3

4 You are responsible for safety while using the Total Gym and any modifications you make to it. If you increase the angle of the platform by simply putting the vertical support on top of something such as a box then the vertical support won t be vertical and the Total Gym will be unstable and unreliable. Don t use the Total Gym in an unstable or unreliable condition. Be aware that increasing the angle of the platform causes increased load in the hand grips, cables, pulleys and fasteners. You are responsible for determining that your hand grips, cables, pulleys and fasteners are capable of handling the increased load before you decide to use them. The following pages show the materials, tools and parts used for making a pedestal from 4 x 4 dimensional lumber. What the lumber yards call 4 x 4 dimensional lumber is actually 3 ½ x 3 ½ when it arrives in the hands of us users. You will see 3 ½ x 3 ½ on all the drawings. The pedestal shown in the photo is the one I have used for several years and it is made from a large pallet s stringer which is 2 7 / 8 x 4. In this paper I ve taken its design and adapted it to the more common 4 x 4 dimensional lumber size. In case you re wondering, I have not used 4 x 4 dimensional lumber and these drawings to build a pedestal. The pedestal I made is from 2 7 / 8 x 4 lumber. If you find an error, missing dimension or have a suggestion about this project please contact me. A person could get the same static resistance increase by adding weight to the platform instead of increasing the platform angle. Adding about 54% of your body weight to the platform will be statically equivalent to increasing the platform angle the amount this pedestal affords. I found the standard Total Gym is too unstable side-to-side when set to its maximum angle and the platform is moved aggressively. Before I added more weight I wanted to add side-to-side stability. The platform added stability and static resistance. Adding weight to the platform is a good idea only if the system is stable. The additional weight requires that you apply additional force to accelerate it. After developing the pedestal I added a bar and weights to the platform in the same way others have done. A detailed photo of the bar attachment is at the end of this document. You re welcome to use this design for any non-commercial purpose. If you make one, you have the responsibility for the quality and care with which you make it, the quality and care with which you attach the Total Gym to it and the suitability of the whole system for any use you put it to. In the pages after the design details there is an analysis of force and power involved in the prone pushdown exercise. There is also a simple analysis of the power required for a 7 mph tandem canoe. Together these analyses provide the explanation of why the top hand s power is critical to maximizing the canoe speed. I hope you find this information useful. Enjoy and train safely. Rich Butts, Mechanical Engineer December 2009 richeb@frontiernet.net This design is drawn in Sketch-Up v7. If you want the model files, contact me. If you have a project design that you d like drawn up or analyzed you re invited to contact me with your needs * * * * * * * A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 4

5 Bill of Materials, Tools and Suggestions Bill of Materials 4 x 4 x 10 Dimensional Lumber, Qty 1... (9 4 is needed, can be made from one 8 and one 4 ) 2 U-bolts, Qty 2... (for fastening the vertical upright s base to the pedestal) ¼ x 3 ½ Hex Head Lag Screws, Qty 7... (for fastening the pedestal together) ¼ I.D. x ¾ O.D. Flat Washers, Qty (7 for the Lag Screws and 4 for the U-Bolts) 1 ¼ x 1 ¼ Right Angle Braces, Qty 2... (for positioning the lower end of the diagonal support) 1 Wood Screws, Qty 6... (for fastening the Right Angle Braces to the pedestal) Wood Glue, Qty A/R... (as required, for fastening the pedestal together) Tools Tape Measure Carpenters Square 1 / 8 Drill Bit... (pilot holes for the ¼ x 3½ lag screws) ¼ Drill Bit... (clearance holes for the ¼ x 3½ lag screws) 1 Auger Drill Bit... (clearance holes for the 7 / 16 socket used on the lag screws and U-bolts) Saw... (Hand, Circular, Table or Band whatever suits you. I used a hand-held circular saw.) Drill... (I used a battery powered portable for the 1 / 8 and ¼ drills and a ratchet brace for the 1 drill) 7 / 16 Socket and Wrench... (tightening the lag screws and the U-bolts) Protractor... (optional) Suggestions I have not shown pilot hole locations for the lag screws to screw into. You ll most likely be using a hand drill to place all the clearance holes. I suggest using the clearance hole as the template from which to mark the hole location on the mating piece and then drill the pilot holes. I have no knowledge about what loads and stresses the Total Gym is capable of handling. I have an approximately five year old Total Gym and for three years I have used it on the Pedestal without breaking anything. Your results may be different. I have my Total Gym/Pedestal on a rug instead of on a potentially slippery hard surface. About two years ago the Total Gym designers, efi Sports Medicine, Inc., changed the handle and cable attachment design from plastic to metal. At that time Total Gym owners could get the new design at no cost if they asked for it. I don t know all the reasons for the design change. Strength and reliability could be reasons. You might want to update. Back To Table of Contents A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 5

6 Pedestal Assembly and Detail Drawings General Views of the Pedestal FRONT BACK Back To Table of Contents A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 6

7 View of the Pedestal and the Total Gym showing Assembly Details Back To Table of Contents A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 7

8 Dimensions of the Base A Section A View of Clearance Holes Diameter ¼ Diameter 1 Back To Table of Contents A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 8

9 Dimensions of the Angled Support Back To Table of Contents A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 9

10 Dimensions of the Top Check your U-bolt center-to-center distance before drilling these holes. I notice the bolt distance varies about 1/8 A B These holes are for the U-Bolts. See the notes on the U-Bolt dimensions page before drilling. Diameter 1 Section A View of Clearance Holes Section B View of Clearance Holes Diameter ¼ Diameter ¼ Diameter 1 Back To Table of Contents A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 10

11 Dimensions of the Upright Back To Table of Contents A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 11

12 Dimensions of the U-Bolt Height of the bolt varies with manufacturer. Typical height is 3" or 3 ½". The drawing for the TOP gives ½ of thread for the nut if you have a 3 bolt. And the bolt will be clamping 1 of wood. If you have a 3 ½ bolt you might want to clamp 1 ½ of wood by shortening the depth of the four 1 diameter holes to 2. Oddly enough, a 2 U-Bolt is intended to be used on a 1 ½ pipe! If your U-Bolt comes with a flat plate, just remove it. It doesn t get used. A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 12

13 Some Close-Up Views of the 2 7 /8 x 4 Pedestal and the Platform Weight Bar The three attachment points of the Total Gym s vertical upright to the Pedestal - Two U-bolts at the base. One lag screw through an existing hole in the Total Gym s vertical upright. Use the hole located about 13 up from the base of the Total Gym. Attachment of the diagonal support to the pedestal Bottom view of the recessed U-bolt s fasteners A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 13

14 Bottom View of Platform Showing Attachment of Additional Bar for Barbell Plates Back View of Pedestal A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 14

15 Static Resistance Provided by the Pedestal s Height The resistance of the Total Gym, like all free weights, has two components the static resistance and the dynamic resistance. Static Resistance The static resistance is the force required to hold the platform load in any position. The static resistance is determined by the platform load and the platform angle. Dynamic Resistance The dynamic resistance is the force required to accelerate the platform load. The dynamic resistance is determined by the total moving mass and the acceleration of that mass caused by the user s applied force. The static resistance is the minimum force the user will experience; the dynamic resistance is determined by the user s effort; and the sum of them is the total resistance experienced by the user. Height & Incline Comparison of the Total Gym 1000 Series and the Total Gym on the Pedestal Total Gym 1000 Series Total Gym on Pedestal Platform s Guide Rail Length 89 Platform s Guide Rail Length 89 Guide Rail s Lowest Height 10 1/4 Rail s Incline: 6.6 Guide Rail s Lowest Height 42 Rail s Incline: 28.2 Guide Rail s Highest Height 37 7/8 Rail s Incline: 25.2 Guide Rail s Highest Height 58 1/4 Rail s Incline: 40.9 Photos in appendix A were made while gathering these dimensions. A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 15

16 % of Platform Load Presented to User as Static Resistance On Pedestal: Lowest On Pedestal: Highest Standard: Lowest Standard: Highest Graph of the Static Resistance Presented to the User as % of Platform Load and Angle 100% 90% 80% 70% Static Resistance Presented to User as % of Platform Load and Platform Angle Resistance as % of Platform Load= Sin(Angle)*100% 60% 50% 40% 30% 20% 10% Use of the pedestal increases the maximum static resistance by 54%. Raising it from the standard s maximum at 43% of platform load to the w/pedestal s maximum at 65% of the platform load. 0% Platform Angle, Degrees Examples of Static Resistance vs Platform Load and Angle User s Weight (Lbs) Additional Weight (Lbs) Total Weight (Lbs) Platform Angle ( ) Static Resistance (Lbs) =Sin(Platform Angle) x Total Weight Back To Table of Contents A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 16

17 Calculating the Force and Power Required to do the Prone Push-Down Exercise The motion of the prone push-down exercise is very similar to the top hand motion of the canoe stroke. That similarity makes it great for training. It is possible to calculate how much force and how much power are used to do this exercise. The calculated power can be thought of as the top hand s potential for propelling a canoe. Many people advocate the top hand s power to be critical in developing canoe speed. That thought leads to asking: At a given speed of a tandem canoe, what percentage of the required per-person power is equal to the top hand s power potential? In the next few pages I ll develop an answer to that question and the question of force needed to do this exercise. For starting out, here is a list of the information I know: 2) Platform Moves Up Details of an Example Prone Push-Down Angle of Platform 38.1 degrees User s Weight lbs Added Platform Weight 40.0 lbs Platform Travel (observation) 18.5 inches Platform Starting Speed (at the bottom) 0.0 in/s Platform Ending Speed (at the top) 0.0 in/s Travel Time, bottom to top (observation) 0.5 Seconds Acceleration due to Gravity in/s 2 Diagram of the Platform Forces Here is a simple diagram of the platform and the forces acting on it: 1) Push Down Prone Push-Down Exercise on a Total Gym with Pedestal and Additional Platform Weight Applied Force as Function of Time = F(t) 38.1 Total Platform Mass x Acceleration due to Gravity = Force of Gravity M Total x g =F gravity A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 17

18 Equations for Force and Power vs. Time for the Example Prone Push-Down Exercise I want to know what the applied force is as a function of time. There are only two forces that act along the platform s line of travel. Those are the applied force and a portion of the force of gravity. Notice that they act in opposite directions, so we can call the direction of the applied force positive and the direction of the portion of the gravity force that acts along the platform s line of travel negative. Let M total represent the total mass on the platform and g represent the vertical acceleration due to gravity. The portion of the force of gravity that is acting along the platform s line of travel is equal to Cosine( ) x M total x g. Since the cosine and the sine are 90 apart we can write that as sin(38.1 ) x M total x g. Sir Isaac Newton pointed out that the sum of all the forces acting on a body and along any one line of action equals the time rate of change of the body s momentum (momentum equals mass x velocity) along that line of action. That s the long way of saying the familiar and simplified F = ma. Putting all that together gets us an equation for the force that the user applies to the platform as a function of time and the acceleration that it gives to the platform as a function of time: *This is the familiar F=ma and the Greek letter sigma,, means sum of the + We can also calculate the power as a function of time by knowing that mechanical power is force multiplied by velocity. Since we want to know the force as a function of time, we must figure out the acceleration as a function of time. And since we want to know the power as a function of time, we must know the velocity as a function of time. Fortunately for us the acceleration is related to the velocity: acceleration is the time rate of change of velocity. So if we know or can estimate the velocity as a function of time, then we can know the force and power as a function of time. Instead of measuring the velocity vs. time, I will estimate it based on experience from doing the exercise. When doing this exercise it is noticeable that the platform velocity increases to a peak just before the top. Then it slows quickly to a stop at the top. The force is large and increasing at the start of the motion. Then it quickly drops to what feels like zero just before the top. Then it quickly rises again at the top of the travel. From those observations I believe the platform s velocity vs. time is close to a skewed parabola: a nice smooth velocity vs. time curve that starts at zero going slowly up to a peak then going quickly back to zero. We can use that observation and the other facts we know to calculate an estimate of the force vs. time and the power vs. time. A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 18

19 Force (Lbs) Power (H.P.) Acceleration (inches/second^2) Velocity (inches/second) Displacement (inches) Calculating the Force and Power vs. Time from the Platform s Acceleration and Velocity Acceleration Along Rail vs Time Time (Seconds) This acceleration vs. time is the derivative of the velocity vs. time equation. a(t) = t t Velocity Along Rail vs Time Time (Seconds) Based on experience from doing the prone push-down exercise this is an estimate of the velocity vs. time: a skewed parabola. v(t) = -3552t t Displacement Along Rail vs Time Time (Seconds) This displacement vs. time is the integral of the velocity vs. time equation and it fits the known fact of 18.5 travel in 0.5 seconds. Force Applied to Platform vs Time Time (Seconds) The peak force is 275 Lbs which is 2.2x the static force of 123 Lbs. The average one-arm power is 0.4 HP Power Applied to Platform vs Time Average One Arm Power Time (Seconds) Average Two Arm Power A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 19

20 Power Required Per-Person in Tandem Marathon Canoe Paddling How much power does it take to paddle a tandem marathon canoe? Suppose it takes an average, continuous force of 50 Lbs 1 to propel a canoe at 7 mph. 7 mph equals 10.3 ft/s. In linear motion, power is force x velocity so the average power is 50 Lbs x 10.3 ft/s = 515 ft-lbs/s. Converting to Horse Power, 515 ft-lbs/s 550 ft-lbs/s per H.P. = 0.9 H.P. per 2 people. So it requires about 0.5 H.P. per paddler to travel at 7 mph Lbs is very likely to be at the high end of the actual force required to overcome friction drag and wave drag in deep, calm water. Comparison of Power: Example Prone Push-Down Exercise vs. 7 MPH Tandem Marathon Canoe Analysis of the example for the prone push-down exercise gave us a result of 0.4 H.P. as the average power from one arm. Recall that the motion of the prone push-down exercise is very similar to the top hand motion of the canoe stroke. Analysis of the example for paddling a tandem marathon canoe at 7 mph gave us a result of 0.5 H. P. required per paddler. Conclusion: The top hand in the canoe stroke is capable of producing a large portion of the power required from a paddler in a tandem canoe. This simple analysis lends support to what many marathon canoe paddlers already know - effectively using the power of the top hand is a critical ingredient to maximize the canoe speed. Knowing that effective use of the top hand s power is critical to maximizing the canoe speed leads to the question - What conditions enable effective use of the top hand s power? 1. The top hand must be directly above the blade for the entire duration of the power stroke. 2. The blade must remain at a fixed distance (laterally) from the canoe s keel for the entire duration of the power stroke. 3. The blade must be fully submerged and perpendicular to the canoe s keel for the entire duration of the power stroke. In practice it means When the catch* occurs, the top hand must already be directly over the blade and it must immediately begin powering the canoe forward, continuing until the end of the power stroke. * The catch is that moment at the end of the recovery phase when the blade is quickly and fully submerged. It is the start of the power stroke. Comment: This comparison makes the implicit assumption that the power expended in one rep. of the prone push-down exercise can be repeated for each of the many, many strokes of paddling a canoe. That is not likely to be true. Perhaps 1 / 3 to 1 / 2 of the calculated power could be sustained. Also in calculating the power required to propel the canoe, the force used is likely at the high end of the actual requirement which may be between 30 to 50 Lbs. Even considering these reductions, the conclusion stays the same. A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 20

21 Unintentional and Happy Consequences The seated, single arm lat pull down The pedestal has made possible doing a seated, single arm lat pull down. It is easy to reach up and pull down on one of the handles while sitting on a low seat opposite the Total Gym s platform. To replicate the top arm s paddling motion just take your arm across your body and grab the handle then press it straight down keeping your knuckles pointed forward. Holding onto a loop of rope that is around your foot will position your bottom hand approximately at the start-of-stroke location. When the total gym was at its factory height the handles were a little too low and the base was not wide enough to be stable during this exercise. To make this motion useful for training you should have additional weight added to the platform. One way to do that is with the addition of a bar to the platform and barbell plates as shown earlier in this document. Here are a few photos that show the arrangement and motion. Notice that my right hand is pulling the handle down on my left side and outboard of my left leg. A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 21

22 Appendix A: Photos of the Total Gym 1000 Series Showing Angles and Dimensions Total Gym 1000 Series: Highest Position General View Total Gym 1000 Series: Highest Position Rail Height Total Gym 1000 Series: Lowest Position General View Total Gym 1000 Series: Lowest Position Rail Height A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 22

23 Total Gym 1000 Series: Diagonal Support Attachment Height Total Gym 1000 Series: Platform Rail Length A Pedestal Design for the Total Gym Revision C 2009 Richard Butts Page 23