Leg extension / Leg Curl / Reverse Hyper  / Seal Row Bench

I can’t justify having a reverse hyper, leg extension machine and leg curl machine.  Also seal rows are a pain to set up.  But one machine to do all of this?  That starts to make more sense.  Let’s have a look.  

We have 4 uprights which support the bench.  The bench is narrower at the seal-row end (because you don’t want the sides rubbing on your arms) and fatter at the rotation end (for the larger-assed trainee).  The carriage rotates on swivel couplings, which are not really meant for this type of use but they are cheap and easily replaced. The carriage is counter-weighted so that there is no net torque about the rotation point until plates are loaded.  Size 3 handrails (with a hole in each end for a retaining pin) are used for the bar that you push against for leg curls, leg extensions and reverse hypers.  Padding is achieved by paint rollers, pipe insulation or pussy pads. Leg extensions use either of the top positions of the vertical leg, reverse hypers use the lower positions of the vertical leg, and leg curls use the positions on the horizontal leg.

Now, if you want a perfectly constant/optimal torque through the whole range of motion, a cable and cam system with a selectorized weight stack is great.  There is no way to achieve this through a plate-loaded rotating method.  The worst example of this is the shitty leg extension attachment that goes on the end of your shitty bench.  If the weight is at the bottom, there is no resistance at the beginning of the movement (save for the inertia) and maximum resistance at 90 degrees.  A step up from this is having the weight at 45degrees, so that it provides some resistance at the beginning, peaks in the middle and has some resistance at the end of a 90 degree movement. The ‘bent-pendulum’ reverse hyper is a good example of this.  Another step up is the higher-end plate loaded leg extension where the start position can be selected by putting a peg through one of many holes.  This is too complicated for me.  My solution is to have two loading positions, one at the bottom and one at the same level as the pivot.  If you want more resistance at the beginning of the motion, add weight to the higher loading point.  If you want more resistance at the end of the motion, add weight to the lower loading point.  The longer the arms, the less weight you need to add to the loading points, but the more weight you’ll have to add to counterbalance the weight of the carriage itself.  You could forget about counterbalancing the carriage but then you will have a minimum load that you have to be able to do to use the machine.

For lack of a better name, I’ve decided to call it the URSA, which stands for Universal Rotation Station Andsealrowbench.

Video showing it in action to come.

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