Concept2 Forum

The thread about "who prefers the old concept to the new one" got me thinking about why the B feels better than the C or the D.<br /><br /><a href='http://concept2.ipbhost.com/index.php?showtopic=1353' target='_blank'>http://concept2.ipbhost.com/index.php?s ... 353</a><br /><br />For one thing the slope of the railing is much more level. This might not result in more speed but it gives a much nicer feel. Can you imagine taking a nice drive in the country and having the car hop up and down every 2 seconds? That would get old very quickly. However, that is exactly what happens on the model C and D.<br /><br />Additional to the railing being (almost) level on the B, there is a related factor of even greater importance.

Measuring the heights of the railing on the model C and B at the back, the height of the center of the axle, and the height of the railing in between, gives the line for the railing directly under the axle, and the height of the axle above this line. <br /><br />model C<br />height of railing in back: 12.125 inches<br />height of railing behind foot stops: 11.25 inches<br />line of railing under center of axle: 10.375 inches<br />height of center of axle from floor: 24.125 inches<br />height of axle above line of railing: <b>13.75 inches</b><br /><br />model B<br />height of railing in back: 10.25 inches<br />height of railing behind foot stops: 10 inches<br />line of railing under center of axle: 9.75 inches<br />height of center of axle from floor: 22.25 inches<br />height of axle above line of railing: <b>12.5 inches</b>

My center of gravity (mass) is probably somewhere around my belly button so I sat on the floor with my legs out and measured the height from the floor to my CofM and got approximately 9.5 inches. The seat is about 3 inches above the railing. This gives me a height from the railing to my center of mass of approximately 12.5 inches or less.<br /><br />height to center of mass: 9.5 inches<br />height from railing to top of seat: 3 inches<br />height from railing to center of mass: <b>12.5 inches</b><br /><br />Coincidently (or the design team for the model B was on the ball), the height of the axle above the top line of the model B railing is the <b>same</b> as the height from the railing to the rower's center of mass.<br /><br />

Can you imagine if the axle was 24 inches above the line of the railing?<br /><br />The machine would be extremely difficult to row in such a case.<br /><br />Thus this 10% difference ( 13.75 / 12.5 ) between the model B and model C/D is quite significant as to the efficiency of these machines and being able to row well on them.<br /><br />Next I took a look at pictures of other machines. This line is hard to tell from pictures but my estimations are as follows:<br /><br />RowPerfect: 11 inches<br />WaterRower: 8 inches<br /><br />In a boat the line of force is <b>below</b> the top line of the railing.<br /><br />Thus we have the following results:<br /><br />Boat: 0 inches<br />WaterRower: 8 inches<br />RowPerfect: 11 inches<br />Model B: 12.5 inches<br />Model C: 13.75 inches

How can this distance between the top line of the railing, and the center of the axle, be brought closer together?<br /><br />Note that changing the height of the feet does <b>not</b> change this distance.<br /><br />This leaves at least 2 ways this distance can be minimized.<br /><br />#1: Raise the height of the seat. Some rowers already do this by adding pads and other material to the height of the seat. This effectively brings the line of the top of the railing closer to the height of the center of the axle and more in line with the center of mass of the body -- allowing a better force application to the chain and resulting pace on the monitor.<br /><br />#2: Raise the center connection between the two halfs of the erg. I experimented with this a little bit yesterday by inserting a drill bit shaped piece of rubber in between the bottom lock of the center connection. This raised the foot stretcher portion of the railing height to 11.675 inches, and reduced the difference between the top railing height and the center of the axle from 13.75 to 13 inches, bringing the difference within 4% of the model B.<br /><br />The lock was still able to close with this setup but I wasn't comfortable with it being not quite secure at the top and didn't try to row this way. However I am satisfied that a more secure lock and higher raising could be accomplished.<br /><br />I'm interested to hear more ideas about how this can be done.

<!--QuoteBegin-John Rupp+Mar 26 2005, 11:31 AM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(John Rupp @ Mar 26 2005, 11:31 AM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin--><br />In a boat the line of force is <b>below</b> the top line of the railing.<br /> <br /> </td></tr></table><br /><br />How do you get this measurement, surely not from and actual boat!<br /><br />Aside from this strange claim, the "Height of the work" (As it is called in rowing) is certainly a consideration in setting up a boat (or Erg) for effective work to be done.<br /><br />Adjustment, if required, is often done with seat pads to lift smaller rowers up. On the Erg the effect is trivial, but in a boat where one must extract the blades from the water, the height of work is rather important to the tasks at hand. <br />

Another way of looking at this is <b>the point of intersection</b> between (1) <b>a forward line from mid handle to the axle of force</b> and (2) <b>a line forward from the top of the railing to that point</b>.<br /><br />On a boat #1 is the length of the oar from mid grip to the mid point of the oar in the water. Considering a 10 foot oar in a scull this is approximately 8.5 feet from mid grip to mid paddle.<br /><br /><img src='http://i2-images.tv2.dk/s/82/231082-7f9 ... 860eb.jpeg' border='0' alt='user posted image' /><br /><br />Thus, considering the slide is closer to the water than the grip, pb]the point of intersection[/b] with the oar would be at approximately 1/3 the height of the grip from the water, as measured at the finish from mid handle directly over the front of the seat this gives us a distance of <b>6 feet</b>.

Here we have a picture of the waterrower.<br /><br /><img src='http://www.bodytrends.com/miscimages/wat1.gif' border='0' alt='user posted image' /><br /><br />Knowing the length of 83 inches makes it easy to calculate the measurements (1), (2) and the resulting intersection.<br /><br />(1) = 69.26 inches<br />(2) = height at axle of force is 78.6% of handle height<br />intersection = 69.26 / 21.4 = 323.2 inches = <b>27 feet</b><br /><br />

<!--QuoteBegin-John Rupp+Mar 27 2005, 05:14 PM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(John Rupp @ Mar 27 2005, 05:14 PM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin--><br />(1) = 69.26 inches<br />(2) = height at axle of force is 78.6% of handle height<br />intersection = 69.26 / 21.4 = 323.2 inches = <b>27 feet</b> <br /> </td></tr></table><br /><br />Ah, the world is right again, with the usual <b>BOLD</b> statement. <br />

<!--QuoteBegin-John Rupp+Mar 27 2005, 04:49 PM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(John Rupp @ Mar 27 2005, 04:49 PM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin-->On a boat #1 is the length of the oar from mid grip to the mid point of the oar in the water.  Considering a 10 foot oar in a scull this is approximately 8.5 feet from mid grip to mid paddle.<br /><br /><img src='http://i2-images.tv2.dk/s/82/231082-7f9 ... 860eb.jpeg' border='0' alt='user posted image' /> <br /> </td></tr></table><br /><br />Is there a sculling oar in this picture? While sculling Oars are approximately 10 feet in length, a sweep oar is about 1m longer. I did notice that you chose a picture with your oft cited object of affection as the subject, interesting.

There aren't any or as good pictures of RowPerfects or, surprisingly, C2's, so making the calculations from pictures is turning out to not be very accurate.<br /><br />Also I think my first method was the most exact so I'm going to stay with that.

Going back to these figures, I want to make sure the distance in front of the foot stops is the same as for the model B and C measurements and will adjust them accordingly.<br /><br />Boat: 0 inches<br />WaterRower: 8 inches<br />RowPerfect: 11 inches<br />Model B: 12.5 inches<br />Model C: 13.75 inches<br /><br />

God bless you John......that's a lot of reseacrh for an erg forum.<br /><br />Keep up the good work. <br /><br />RichardT

I've come up with a "model J" design, that is much more like rowing in a boat.<br /><br />For those interested, you can see the image here:<br /><br /><a href='http://i2.photobucket.com/albums/y41/jo ... modelJ.jpg' target='_blank'>http://i2.photobucket.com/albums/y41/jo ... jpg</a><br /><br />Here is a shortened version, with the length of the model J and distance to the fan cage the same as for models C and D.<br /><br /><a href='http://i2.photobucket.com/albums/y41/jo ... odelJb.jpg' target='_blank'>http://i2.photobucket.com/albums/y41/jo ... jpg</a><br /><br /><img src='http://i2.photobucket.com/albums/y41/jo ... odelJc.jpg' border='0' alt='user posted image' />

How is that "more like a rowing boat"?<br /><br />Having the flywheel axel so far below your shoulders would make it very difficult to pull the handle through on a path parallel to the seat rail. What we do in a boat. (more or less)<br /><br />Pretty sure John is ignoring this, too bad, since it would only help him solidify his idea.