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Significant chain sag and no handle return
Posted: January 3rd, 2021, 11:08 pm
by Rees1234
I was given a non-working 2nd hand Concept2 Model A Ergometer and the original owner was kind enough to order a new shock chord.
However, the reassembly of the skewer return mechanism was left to me and my son. Unfortunately we did not observe the
disassembly but we did thoroughly read the instruction booklet. Having never seen, let alone used a rowing machine, we find ourselves unable to get it working. The video I posted of my son rowing conveys the problem we are having. Thank you and Happy New Year!
Rees
https://www.youtube.com/watch?v=y108R1ZO_xU
Re: Significant chain sag and no handle return
Posted: January 4th, 2021, 5:52 am
by Citroen
Re: Significant chain sag and no handle return
Posted: January 4th, 2021, 9:20 am
by Rees1234
Thank you Citroen. We have read the Model A docs many times, but we will persevere.
Re: Significant chain sag and no handle return
Posted: January 4th, 2021, 9:34 am
by Citroen
Send an email to
info@concep2.com as they can still offer support for ancient rowers.
Re: Significant chain sag and no handle return
Posted: January 4th, 2021, 11:43 am
by Ombrax
Or give C2 a call. The person who answers the phone may not be 100% up to speed on A's, but I'm sure they can hook you up with someone who is.
Re: Significant chain sag and no handle return
Posted: January 4th, 2021, 12:06 pm
by dsamant
What is the serial number of the Model A you acquired? If it is the later version or if the previous owner has replaced it with an new one, the skewer return mechanism will be similar to the Model B. Since it is a brand new shock cord, the only two reasons could be incorrect installation (not enough tension on shock cord) or the pulley mechanisms are defective and need to be replaced. Was the tension better than when you replaced the cord? That can be a indication of which of the two reasons are causing the current problem.
I have the URL pasted below. If you need assitance from Concept2 ask for Will Spalding.
https://www.concept2.com/files/pdf/us/i ... sembly.pdf
Re: Significant chain sag and no handle return
Posted: January 4th, 2021, 2:31 pm
by Ombrax
I just took a look at the video.
Something has been installed incorrectly - the flywheel should continue to spin in the same direction throughout the entire process. Unless something is fooling my brain, it appears that when the force is applied to the handle (btw, your son should have his hands on top of the handle, not under it) the flywheel spins in one direction, then slows down, comes to a stop, then spins in the other as the chain is retracted. That is 100% incorrect, and says that something is way wrong in the way things are hooked up.
Take a close look at the drawings, and compare them to what you have. Based on what the video shows, I'm certain that you'll find critical differences.
Good Luck
Edit: Also, check the freewheel clutch - is it not allowing the wheel to spin freely?
Re: Significant chain sag and no handle return
Posted: January 4th, 2021, 3:21 pm
by c2jonw
From the vid I don't think there's anything wrong with the return mechanism. It looks like the freewheel mechanism is locked up, preventing the flywheel from spinning freely while the sprockets rotate in the opposite direction during the recovery. I'd remove the flywheel and get some solvent into the freewheel to see if that will loosen it up. You might also bring the flywheel to a bike shop to have them free it up. It is a standard (1980"s) rear bicycle wheel with a 5 or 6 speed gear cluster. Good luck with it!!
Re: Significant chain sag and no handle return
Posted: January 4th, 2021, 4:45 pm
by Tsnor
Ombrax wrote: ↑January 4th, 2021, 2:31 pm
I just took a look at the video.
Something has been installed incorrectly - the flywheel should continue to spin in the same direction throughout the entire process. Unless something is fooling my brain, it appears that when the force is applied to the handle (btw, your son should have his hands on top of the handle, not under it) the flywheel spins in one direction, then slows down, comes to a stop, then spins in the other as the chain is retracted. That is 100% incorrect, and says that something is way wrong in the way things are hooked up.
Take a close look at the drawings, and compare them to what you have. Based on what the video shows, I'm certain that you'll find critical differences.
Good Luck
Edit: Also, check the freewheel clutch - is it not allowing the wheel to spin freely?
https://io9.gizmodo.com/why-do-wheels-s ... 1593807400
"This phenomenon is known as the "wagon-wheel" effect. If, like most people, you're accustomed to seeing the wagon-wheel effect in movies or TV, its explanation is fairly straightforward: Cameras record footage not continuously, but by capturing a series of images in quick succession, at a specified "frame rate." With many movie cameras, that rate is 24 frames per second. When the frequency of a wheel's spin matches the frame rate of the camera recording it (say, 24 revolutions per second), each of the wheel's spokes completes a full revolution every 1/24 seconds, such that it ends up in the same position every time the camera captures a frame. The result is footage in which the wheel in question appears motionless... "
Re: Significant chain sag and no handle return
Posted: January 4th, 2021, 5:11 pm
by Ombrax
Tsnor wrote: ↑January 4th, 2021, 4:45 pm
"This phenomenon is known as the "wagon-wheel" effect.
It did occur to me that my perception of the flywheel spin direction may be due to the strobe effect of the frame rate, but I'll leave it to the OP to confirm or deny that it does indeed come to a full stop then reverse directions. I'm betting on the former.
Re: Significant chain sag and no handle return
Posted: January 4th, 2021, 6:34 pm
by Rees1234
Thank you all for your posts. I really appreciate your interest.
It is my belief that I have the SR Mech installed correctly: skewer bar orientation, skewer axles off-centre, shock cord pulley with the side with no writing against the skewer bar. I've studied the assembly diagram religiously!
The old shock cord was replaced to solve the problem I'm still having. It measures 10 feet.
The S.C.A.M. does not appear to make the problem better or worse
The serial number is 7034 Concept ll
I have sent an email to info@concept2
I think the flywheel clutch is another avenue to consider.
My son's form in the video was meant to convey exasperation but I appreciate your guidance
Rees
Re: Significant chain sag and no handle return
Posted: January 4th, 2021, 6:44 pm
by c2jonw
Can you rotate the flywheel by hand clockwise (from the sprocket side) with the sprockets and chain remaining stationary? If not then you have a frozen clutch/freewheel mechanism.
Re: Significant chain sag and no handle return
Posted: January 4th, 2021, 9:11 pm
by Rees1234
No I cannot. So it should rotate independent of the sprocket and chain?
I've reviewed the Model A parts list but don't find any reference to the flywheel.
What part should I order...a freewheel mech?
Thank you for your response.
Rees
Re: Significant chain sag and no handle return
Posted: January 4th, 2021, 9:48 pm
by Ombrax
The second post in this thread says that it's a standard 5-speed bicycle freewheel:
viewtopic.php?t=7836
More info on how to remove one:
https://www.parktool.com/blog/repair-he ... stallation
Re: Significant chain sag and no handle return
Posted: January 4th, 2021, 10:05 pm
by dsamant
Out of curiosity, what causes the clutch/freewheel mechanism to lock up in the first place? Is it age? storage in extreme conditions? anything else?