Concept2 Forum

I have a RowErg that I've bought fairly recently and I can't get the monitor arm to not wobble while rowing. I have my phone set up on the phone holder, and with every pull it wobbles like crazy. I've had Concept2 rowers for most of the last decade, and I've never had this before as the monitor arms were always much stiffer than the current one which twists with very little effort.

Do I have a defective arm? Alternatively is there a way to stop this so that my phone doesn't twist left and right while rowing?

Perhaps if you tighten the bolt-nut a skosh.

https://www.concept2.com/files/pdf/us/i ... stment.pdf
It doesn't have any torque values, but does suggest using an 11mm spanner on either end of the bolt.

Something not right there, its an assembly problem or something because there is no way that plastic arm has any flex in it due to the "H" shape construction. The bolt at the base of the arm needs to bite into the Nylock nut so you cannot just finger tighten it. Something basic is wrong with your setup, shouldn't be hard to figure out what.

Maybe someone has replaced the monitor without buying the right mounting kit? Which model Erg and PM is it??

Carl Watts wrote: ↑

March 24th, 2022, 9:27 pm

Something not right there, its an assembly problem or something because there is no way that plastic arm has any flex in it due to the "H" shape construction. The bolt at the base of the arm needs to bite into the Nylock nut so you cannot just finger tighten it. Something basic is wrong with your setup, shouldn't be hard to figure out what.

The H cross section helps with up/down and left/right movement but has almost no resistance (at least in the one that I have) to any twisting motion. I can twist the monitor clockwise and anticlockwise with hardly any force at all, and if I do twist it and release it acts a little like a torsion spring for a bit.

I have had two other Concept2 ergs before this (all, including this one bought new), and none of the others had this problem.

MPx wrote: ↑

March 25th, 2022, 5:13 am

Maybe someone has replaced the monitor without buying the right mounting kit? Which model Erg and PM is it??

It's a RowErg bought new less than a year ago with a PM5 monitor. So unless it was swapped out in the factory, this is the original one. I've tried tightening the bolts, but they are really tight, and connection is not where the wobble comes from anyway. It comes from the arm itself twisting really easily. Maybe a slightly off balance blade is producing resonance with the arm, which easily twists. Either way, it's damn annoying.

Time to contact C2....whatever the cause is, they'll make it right.

If you loose a balance weight off the flywheel it creates a nasty vibration problem.

My monitor remains motionless so it sounds like you have a bit of a major problem there.

Yes the plastic arm does flex, just tried mine but doubt thats your problem you have a nasty resonance caused by the flywheel no longer being in balance.

If its out of balance you get a pretty bad sound to go with that. There is a gap between the rubber cups and the bearings in the flywheel on certain models of the rower so if there is an imbalance problem the flywheel tries to jump all over the place during your recovery.

Carl Watts wrote: ↑

March 25th, 2022, 2:20 pm

If you loose a balance weight off the flywheel it creates a nasty vibration problem.

My monitor remains motionless so it sounds like you have a bit of a major problem there.

Yes the plastic arm does flex, just tried mine but doubt thats your problem you have a nasty resonance caused by the flywheel no longer being in balance.

If its out of balance you get a pretty bad sound to go with that. There is a gap between the rubber cups and the bearings in the flywheel on certain models of the rower so if there is an imbalance problem the flywheel tries to jump all over the place during your recovery.

Is there any objective way to find out if the flywheel is off balance? There is definitely a more pronounced wobble on the PM5 during the drive, but I don't hear any unusual noises, so I'm not sure about it.

Carl Watts wrote: ↑

March 25th, 2022, 2:20 pm

If you loose a balance weight off the flywheel it creates a nasty vibration problem.

I have "some" experience with unbalanced flywheels (NordicTrack, not Concept2!), and that kind of problem is hard to miss. In that case, the whole cage is shaking and you probably feel vibrations in the chassis as well.

The best idea would be to row and get someone else to take a video on their phone and post it on YouTube.

I'm sure a combination of watching you row and your technique, the movement of the monitor and any sound with give a clear picture.

The out of balance flywheel slows up on the recovery not the drive. On the drive the chain pulls the flywheel towards you and restricts its movement in the rubber bearing cup holders. During the recovery its free to move all over the place.

The flywheel weights are only 1gram or 1.5grams each but the effect of loosing one is dramatic. I have posted here years ago that new owners should remove the plastic cover and mark round the weights with a permanent marker pen.

I got rid of most of my weights by drilling and tapping holes at the weight points and fitting button head cap screws with or without a thin washer under them for 1 gram or 1.5gram replacements.

Concept 2 should change the way it balances the flywheel or at least use a better design stainless steel clip.

This may be obvious to all, but I'll throw in my $0.02:

It should be relatively easy to figure out if the problem is due to 1) freeplay at any of the joints from the PM down to the "stiff" part of the frame where the arm is attached, 2) excess flexibility of the arm that supports the PM, or 3) Unbalance of the flywheel that excites the PM support system, either at a resonance of the system, or just forced excitation at an off-resonance frequency.

For (1) look for the location that goes "clunk - clunk" as you apply loads to the PM.

For (2) see what's flexing as you apply loads to the PM - if it's the arm, then that's strange, because in general the C2 PM support arms are pretty stiff.

For (3) you should be able to tell if the motion is worse at a specific RPM, then decreases at higher RPMs. If that happens, then the issue is likely due to resonance. If the PM motion and worse and worse as RPM increases, and never seems to improve, then it may be a simple unbalance. But in that case you should really notice the whole "front" end of the rower vibrating, not just the PM. Or it may be resonance at an RPM that's higher than what you can achieve yourself. Either way, it's probably due to a poorly balanced flywheel.

I would guess that the problem is due to freeplay (1).

Let us know what you find.

I would also check the front leg still has 4 bolts holding it to the frame and they are all tight.

John, did you ever figure out what was going on?