Slides Under The Indoor Rower

[old] Byron Drachman · Post by **[old] Byron Drachman** » December 18th, 2004, 5:09 pm

P.S. Let me take a crack at Paul's exam questions: 1) When the weight of the ergometer exceeds the weight of the rower 2) Yes, it would be impossible because the quantity m in equation 13.4 becomes infinite. Paul, did I pass the pop quiz? Byron

[old] Byron Drachman · Post by **[old] Byron Drachman** » December 18th, 2004, 5:37 pm

Ooops. Did you ever finish an exam and then while walking home realized you got the wrong answer? Paul, can I change my answer to 2? As the ergometer becomes heavier, the rower would move back and forth more and the ergometer less. If the ergometer becomes infinitely heavy then you just have a classical ergometer which doesn't move. Byron

[old] PaulS · Post by **[old] PaulS** » December 18th, 2004, 6:24 pm

That's the problem with Anu's page, it's filled with wonderful equations but still misses something, otherwise the effect would be easily measured experimentally, which it has not been. "When practice is so much at variance with theory it is certain that the later has failed to take all the factors into account." (A Textbook of Oarsmanship. Bourne, 1925) Byron, Good recovery!

[old] Byron Drachman · Post by **[old] Byron Drachman** » December 18th, 2004, 7:31 pm

Hi Paul, I see what you mean about that page. I just noticed section 12, where presumably the topic of slides is covered. It makes absolutely no sense to me, but I'm not an expert. It starts off assuming the accelerations of the rower and boat (or moving ergometer) are constant. If that were true, the rower would fly off the back of the moving ergometer at the end of the stroke, or am I missing something? I agree that I'd rather listen to people who have tried it and hear their opinions until I can find a physics discussion that I can follow and makes sense to me. Byron

[old] John Rupp · Post by **[old] John Rupp** » December 18th, 2004, 8:42 pm

If you add all the Paul Smith's from PS Sport end to end, they will still reach the wrong conclusion.

[old] PaulS · Post by **[old] PaulS** » December 19th, 2004, 10:27 am

</div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td class='genmed'>QUOTE (John Rupp @ Dec 18 2004, 04:42 PM)</td></tr><tr><td class='quote'> If you add all the Paul Smith's on the forum end to end, they will still reach the wrong conclusion.  </td></tr></table> Good one John! I'm ROTFLMAO. You are so funny I just can't believe it, how did you ever get so clever? You've elevated this habit of yours, of being "exactly wrong", to near an art form. Must have been part of the correspondence coursework to become a Life Coach. What was it that brought you out of your little cave this time? EHFUYA, DYHTHYH, TSSTWYD?

[old] bubba · Post by **[old] bubba** » December 19th, 2004, 5:20 pm

</div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td class='genmed'>QUOTE (PaulS @ Dec 19 2004, 09:27 AM)</td></tr><tr><td class='quote'> Must have been part of the correspondence coursework to become a Life Coach.  </td></tr></table> Huh? There is a correspondence course (or any type of real coursework) for becomeing a Life Coach? I didn't know there was such I thing. I thought it was just a title that losers used to sound important when they really know nothing?!?!?! (I hope I am not offending anyone and that no one here calls themself a Life Coach...if so, I retract my comment)

[old] PaulS · Post by **[old] PaulS** » December 20th, 2004, 10:53 am

Hubba Bubba! Now that's some truly funny stuff! Please do not attack "Lables", there is plenty of content to go around. I forget that newbies drop in from time to time, so to be perfectly clear - I was being sarchastic with my little friend the Life Coach. Cheers!

[old] tomhz · Post by **[old] tomhz** » December 20th, 2004, 3:23 pm

</div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td class='genmed'>QUOTE (jamesg @ Dec 17 2004, 03:55 PM)</td></tr><tr><td class='quote'>However there is less work to do on the slides because the CG of the erger/machine becomes stationary. On the fixed erg we have to accelerate our mass twice every stroke. How to get that "less work" or saving to the handle and so spend it on the flywheel is another problem. Unlikely to be automatic, in any case. We have to pull harder, longer (this is probably the major factor, due to the quicker and so shorter catch on slides) or at higher rating. The result will depend on the erger and specifically if he has the technique and training to do it. If he doesn't pull harder longer or faster, the counter won't see anything different. Any experiment can only show whether or not the erger knows how and/or has trained to do this. We don't need to test Newton, and the basic dynamics/ engineering/ physics is perfectly clear. </td></tr></table> Jamesg says it right. And Byron is right too: The calculations in <a href='http://www-atm.physics.ox.ac.uk/rowing/ ... meter.html' target='_blank'>http://www-atm.physics.ox.ac.uk/rowing/ ... /a> are OK. Mathematics and physics don't lie. The theoretical saving is small but significant. The question is: can this saving be put to use to obtain higher speed. There seem to be two camps with different answers to that question: A: yes it can, but it requires skilled technique and a lot of practise. B: no it can't. People with good and skilled technique cannot benefit by using slides. On the contrary: people with certain technique faults will be punished less for that when on slides. It is a mistake to think that these people have found a way to "convert" the saved energy to a higher pace. I think that is what the discussion is all about. Tom

[old] John Rupp · Post by **[old] John Rupp** » December 20th, 2004, 4:51 pm

Tom, Good summary. However I think good technique, i.e. form, rhythm, timing, relaxation, endurance etc, are needed even more on the slides than the erg. Thus really to go faster on the slides, one needs to have BETTER technique, than those who would find no difference. For example, one who had an inflexible rigid stroke would very likely have the same inflexible rigid stroke on the slides, and thus find no difference. However, by adapting ones form, rhythm and timing to the slides, then it is possible to make the most of the advantages and faster times that are possible on the slides.

[old] jamesg · Post by **[old] jamesg** » December 20th, 2004, 5:13 pm

Did a few quick sums on the work done in accelerating our mass at catch and recovery, on a fixed erg. As to rating and ratio, there are big differences. For 80 kg erger: At rating 20, pull/recovery time ratio 1:2, the power needed is 6W At 30, 1:2, 20W At 40, 1:1, 34W. I assumed constant body speed to make sums easier. I used a CG travel distance of 60cm, which is what I measured for me. Dudhia uses 100cm, so either he has long legs or just guessed. This doesn't alter the principles, just the values. On a moving erg, the powers needed are roughly 1/6 of the above values, due to the mass ratio erg/erger. If the mass of the erg on slides were zero, the power needed to move it would also be zero. So for 1/2 hour at 20, at say 180W, I could save 6-1= 5W: 5*30 = 150 W minutes, roughly the work done in 10-15 strokes, in a total of 600 strokes. In 120 sec at 40 I'd save < 60Wmin, 6 strokes-worth at most. The percentages of Watts saved seem to be around 3% at low ratings, or 1% in pace. This = Paul Flack's 1 second difference - evidently he's cracked the nut of how to get the power saved, into the flywheel. Simple, just pull harder, longer or faster, using the chemicals, oxygen etc that you saved elsewhere... There's a larger difference at high ratings. 40 for a good erger means maybe 350-400W, so the difference fixed/moving erg, 30W is around 7-8%. So if we want to do a test on fixed / moving ergs, then to see the effects clearly, it should be done: By someone who can pull equally well on both (otherwise we're testing the erger, not the machines). At as high a rating as possible, without losing length. Flat out, so that we know we are producing all the power we have. Otherwise I think we'd probably not see any effect, either because it's just too small, or we don't know how to make it show. When I tried it like that (sets of 100m pulls, no holds barred, in sequence on and off my home-made slides), I saw large differences in "favour" of the slides. It was as if the slides removed an obstacle.

[old] tomhz · Post by **[old] tomhz** » December 20th, 2004, 5:18 pm

</div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td class='genmed'>QUOTE (John Rupp @ Dec 20 2004, 08:51 PM)</td></tr><tr><td class='quote'> Thus really to go faster on the slides, one needs to have BETTER technique, than those who would find no difference. For example, one who had an inflexible rigid stroke would very likely have the same inflexible rigid stroke on the slides, and thus find no difference. However, by adapting ones form, rhythm and timing to the slides, then it is possible to make the most of the advantages and faster times that are possible on the slides.  </td></tr></table> John, that puts you in camp A. I incline to vote A too, but I have no single experience with slides. FWIW, I do have on-water experience and as people say slides resemble on-water rowing more than a stationary erg, I would think slides need better technique to perform well. Tom

[old] tomhz · Post by **[old] tomhz** » December 20th, 2004, 5:27 pm

</div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td class='genmed'>QUOTE (jamesg @ Dec 20 2004, 09:13 PM)</td></tr><tr><td class='quote'>When I tried it like that (sets of 100m pulls, no holds barred, in sequence on and off my home-made slides), I saw large differences in "favour" of the slides. It was as if the slides removed an obstacle. </td></tr></table> James, If we assume you really proved that you can go faster on slides, you only proved it for 100m sessions. It cannot be extrapolated to longer distances automatically. Compare it with stating that higher gears on bicycles allow you to go faster. The only proper (possible) conclusion is that higher gears allow you to sprint faster. Tom

[old] PaulS · Post by **[old] PaulS** » December 20th, 2004, 5:49 pm

Hey C2Jon, can you get the Hagerman study back up on the web to help with this discussion?

[old] John Rupp · Post by **[old] John Rupp** » December 20th, 2004, 6:20 pm

</div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td class='genmed'>QUOTE (jamesg @ Dec 20 2004, 01:13 PM)</td></tr><tr><td class='quote'> When I tried it like that (sets of 100m pulls, no holds barred, in sequence on and off my home-made slides), I saw large differences in "favour" of the slides. It was as if the slides removed an obstacle.  </td></tr></table> James, Any suggestions on how to make the home-made slides? Are they still working?

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