The flywheels are 14 cm (5.5 in) in diameter and 4 cm (1.6 in) thick, stainless steel. As mentioned  previously, their inertial properties and the gear ratios were specifically chosen for the 227-kgf (500-lbf)  load setting on ARED. The flywheels can see a maximum speed of 800 rpm. Therefore, when the  exerciser reaches the bottom of the stroke, and stops the flywheels from spinning, the flywheels could  deliver a maximum of 91 kgf (200 Ibf) extra at the lift bar. This would occur at the 272-kgf (600-lbf) load  setting, 76.2-cm (30-in) stroke, and a 2 second period. It is highly unlikely that anyone will exercise at this  load, speed, and stroke. However, these parameters were the maximum range of the project’s  requirements.  In order to protect the exerciser and the ARED hardware from overloading, the flywheels are directly in  line with a friction disk slip-clutch. This slip-clutch is set to slip at 3.39 Nom (30 inolbf) of torque which is  less than 10% more torque than the maximum load described in the previous paragraph. The slip-clutch  eliminates concerns of excessive loading being imparted on the device.  Both Percentile (162 Ibm) Person Petforming a Squat of 30 in Stroke with a 2 Second Period  600 IY tMallrtt might bat162 lbm AStOMUt  Ptrtorming a 138 Ibf squat in 1.G  I  162 Ibm Astonaut Performing a squat, in 0-0. on  AREDvilhat600IMLordSctting  500 IM total free might bad: 162 Ibm ARonau  Perfoming a 338 bl squat in 14 -20 LY) Ovrr  Desirrd Ine  I  9  c  Desired Inertia  A 300 Ibf total lree weight load: 162 Ibm ARonau  Perhrning a 138 IM squat in 1.0  162 Ibm Aslonau Performing J quat. in 0-Gon  AREDvirhat300IMLoadS.tling  0 200 Ibf totallrrrmightload:162IbmAaonnn  Pwforming a 38 IM squat in l.0  I  5% (4 LY] Undrr  Desired Inertia  Desired Inertia 162 Ibm Astonaut Perlonning a squat. in C-G. on  ARED vilh at 200 IM Load Setting  162 IM tMal free weight bat 162 Ibm AStOMut  Perlorrnhg a 0 bl squat in 1-0  162 Ibm Astonaut Perlorming a squat, in 0.6 on  ARED with a 162 kl Load Setting -- \I 162 Ibm AstOMut Peffom*1g a squat. in 0-G. on  2x13 LM) Undrr  Desired Inertia ARED vilh u 500 IY Lord Stttiiy  4~) IY tor4 tree might bat 162 ~bm ~sroMut  162 Ibm A~OMW Performing a squat, in 0-G on . -  e Performing a 238 Ibl swat in 1.0  3% [14 Lbf] Under 1 AREDwlhat4WIMLoadSeniiy - Desied Inertia  I I  0 100 2w 300 400 500  Foot Reaction Load (Lbf) 600 700 800 900  mConstant ARED Load Component in C-G  OARED Body Inertia Component in 0-G  .Free Weights I-G Inertia Component .Constant Body Weight Component in 1-G oConstant Free Weight Component in 1-G  .Flywheel Inertia Component in 0-G H Body Weight 1-G Inertia Component  oload Short or Over Goal  Figure 13. Chart comparing the load contributions during 1-G free weight squat exercise and  squat exercise on ARED in a 0-G environment. This chart is for a 50th percentile astronaut performing  a 76.2-cm (30-in) squat with a 2 second period at 45.4-kgf (100-lbf) increments. It shows that the inertial  variation between ARED exercise and 1 -G exercise is relatively small.  Design Details - Arm Base Slider  Each cylinder shaft is attached to the arm base slider through a rod-end with a spherical bearing. The  slider is attached to a ball screw, in the arm base, with a slider housing (Figure 14Figure 16Figure 17).  The ball screw is used to adjust the exercise load of ARED. This is done by changing the moment arm  between the pivot point of the arm base and where the cylinders attach. A scale and position indicator is  provided on the arm base cover to aid in this load adjustment. The attachment to the ball screw uses a  housing/slider design that follows curved tracks (Figure 17) on the sides of the arm base with cam rollers.  326