The catch and the resistance right after

[iain]

2g is 2x9.81m/s², or 20m/s², which requires a force of twice our weight. A force equal to our mass produces an acceleration called g, almost 10m/s², as in free fall.

So you are assuming that our legs only produce the force that they would require to hold us up if we were standing (ie our weight). I would have hoped to do a bit better than that. For those less comfortable with equations, the "2" in the 2G is from the V² = 2AS. So not twice our force, once.

In any case, at 1m/s a slack of 10cm, while easily seen, takes only 0.1 seconds, so in terms of perception is non-existent.

S = 1/2(U + V)/t.

U = 0 (stationery at start), so 0.11 = 0.5 x 1.5 x t
So t = 0.11 x 2 / 1.5 = 0.15". So I agree a small time even on your figures.

[2ball]

I'm more of a "me pull chain real hard, wheel make noise" kind of guy.
But I like you guys mathing it!

[iain]

2g is 2x9.81m/s², or 20m/s², which requires a force of twice our weight. A force equal to our mass produces an acceleration called g, almost 10m/s², as in free fall.

So you are assuming that our legs only produce the force that they would require to hold us up if we were standing (ie our weight). I would have hoped to do a bit better than that. For those less comfortable with equations, the "2" in the 2G is from the V² = 2AS. So not twice our force, once.

In any case, at 1m/s a slack of 10cm, while easily seen, takes only 0.1 seconds, so in terms of perception is non-existent.

S = 1/2(U + V) x t.

U = 0 (stationery at start), so 0.11 = 0.5 x 1.5 x t
So t = 0.11 x 2 / 1.5 = 0.15". So I agree a small time even on your figures.

Corrected.

[Tsnor]

common causes of "slack" at catch

1. hands too low. If "chain sprocket" to "handle/hands" to "shoulders" is not a straight line then when you start the drive the flywheel doesn't move until your handle/hands get pulled in a straight line. (if not clear from description try putting your hands VERY low or HIGH to see this effect.)

2. "shooting the slide". "Shooting the slide" is when your legs drive and your butt and seat move but the handle doesn't. Easier to see this in a video then describe. Flywheel doesn't move until handle moves long after seat moved when you shoot the slide. https://www.youtube.com/watch?v=QLEezSLwE1g

3. No lat/core tension at catch. If your body "stretches" when your legs drive you are not pre-loading arms and back correctly. See "shooting slide" above, but with lack of lat/core tension nothing moves (instead of seat moving and handle not moving). Fix with strong back position, shoulders down, lats preloaded by rotating wrists slightly like you are trying to bend the handle.

4. edit. Or the erg has a failing one-way bearing. If its not a solid fail (when you pull the chain the flywheel doesn't move at all) then the amount of chain you can pull before the flywheel engages will vary intermittently, some strokes catch immediately, some strokes you can pull lots of chain before catching. Common problem. See Carl's post above.

[jamesg]

force that they would require to hold us up

That or twice that force, but only when impacting the slower chain at the catch. Static forces equal to weight are easy even with one leg if straight, it's not the muscle that carries the load. High dynamic forces generated by muscle maybe at high speed are possible only for weight lifters, once.

A complete stroke pulled at say weight = force 75kg, 735N, of length 1.2 is worth 880 Nm.

Pulling 25 a minute is 880 * 25 / 60 = 367W. Racing with that stroke at 38 would be over 500W, not bad at all if we can reach 2000m.