Concept 2 Model D old vs. new difference in rowing

Maintenance, accessories, operation. Anything to do with making your erg work.

Concept 2 Model D old vs. new difference in rowing

Postby philie » June 11th, 2018, 6:37 am

Hey there!
I do have a question to you!
I do own and use an old Model D Rower at home ( 2005 ) and am quite happy with its performance over the years. apart from pleaning, a drop of oil and a new rubber band once its holding up great.
However, the last time i was at the gym i was able to use a new black model D with the PM 5 Monitor and realised that the overall rowing performance was far superior that the one at home.
Especially how the chain was reacting made a huge difference it seemed to be "tighter", pulled back quicker and easier than with my machine.
I wanted to ask what i could to to achieve something like this at home. I figured it might be the rubber band which has to be tighter, however, i already tightened it quite a bit.
What else would go into the equation to achieve a more responsive rowing experience .
thanks a lot and have a great week!
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Re: Concept 2 Model D old vs. new

Postby jackarabit » June 11th, 2018, 11:08 am

At a glance, should be as simple as replacing mechanicals, right? You have cinched up at least one original and one replacement chain return cord and have a base in experience to decide if again replacing a dead shock cord with a supple, responsive cord will improve chain retraction.

Do you anticipate that replacing additional moving parts (chain, spocket, axle, mains, fan w/ new clutch bearing, idler sheaves and axles) will produce a mechanism with tighter tolerances than your worn mechanism?

Or do you expect to duplicate the “feel” of the new D?

If the latter is your heart’s desire, consider buying a new D and selling the beater. Looking for new car “smell” from an a la carte resto is an expensive experiment! A new D, assuming reasonable quality control in its production, should duplicate rather than approximate the performance of others from its production cycle.
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Re: Concept 2 Model D old vs. new difference in rowing

Postby philie » June 11th, 2018, 12:03 pm

thanks for the reply! as i am quite happy with the machine i do not intend to exchange it for a new one. i am a student and money is an issue. however, i guess my question was aiming at "which parts to exchange" to come closest to that "almost new" rowing experience :o
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Re: Concept 2 Model D old vs. new difference in rowing

Postby jackarabit » June 11th, 2018, 3:04 pm

Swap out chain, sprocket (remember to order sprocket removal assist tool), and chain return “rubber band.” Flush and lube one-way bearing/clutch in the flywheel. Check operation of sealed axle bearings while the drive shaft is out. Check smooth operation of chain and shock cord idler pulleys. Put in a second order if necessary. :evil: (Paying the shipping twice will crimp anyone’s budget!).
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Re: Concept 2 Model D old vs. new difference in rowing

Postby Carl Watts » June 11th, 2018, 5:08 pm

There is no difference between the two when they were both new.

If you have a mechanical aptitude you can completely strip and rebuild the rower in a couple of hours. I picked up an older Model D from a gym that was free and lying on the floor in bits and rebuilt it, its now my preferred rower as for some reason it feels better than my newer one. The flywheel keeps spinning for much longer after I stop rowing on the early one for some reason, even on the same drag factor. There may be some subtle difference between the flywheels because I have done everything possible to make them the same.

Replace the chain and the shock cord. Personally I wouldn't bother to replace the sprocket. Seat rollers are usually shot and clean the monorail. You will find it will quickly feel like a new rower.
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Re: Concept 2 Model D old vs. new difference in rowing

Postby philie » June 12th, 2018, 3:56 am

thanks guys! this is what i will do! much cheaper than a new machine!
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Re: Concept 2 Model D old vs. new difference in rowing

Postby sekitori » June 12th, 2018, 12:29 pm

Carl Watts wrote:There is no difference between the two when they were both new.

If you have a mechanical aptitude you can completely strip and rebuild the rower in a couple of hours.

Replace the chain and the shock cord. Personally I wouldn't bother to replace the sprocket. Seat rollers are usually shot and clean the monorail. You will find it will quickly feel like a new rower.


Unfortunately most (probably the vast majority) of us don''t have mechanical aptitude close to that of Carl Watts. But as long as we can find people who can do that type of work for us, that's okay.

I agree with replacing the shock cord and chain. I recently sold a fourteen year old Model D which was still working quite well despite the fact that it had the original shock cord. I purchased a new Model D and the difference was amazing. The new machine was for lack of a better word, tighter. It just felt much more solid. I'm sure the major differences were the new shock cord and nickel chain.

Take Carl's advice and change the shock cord, the chain, and the top rollers. That should be all you have to do. And of course, be sure the rail is pefectly clean every time you use the rower. If everything else on the rower is in good shape, you'll end up with an excellent machine.
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Re: Concept 2 Model D old vs. new difference in rowing

Postby Allan Olesen » June 12th, 2018, 7:27 pm

I very much respect the knowledge of Carl Watts - but I have to say that I would replace the sprocket anyway. My reasons:

1. The sprocket is quite cheap, compared to the chain. So why save a few pennies and do a half repair?

2. When I recently replaced sprocket and chain on my model D1, the plastic on the old sprocket was partly missing because it had become brittle and cracked. I assume that this plastic has a silencing function, so if it is missing, you will get more chain rattle against the sprocket. (And I actually replaced these parts because I wanted to reduce noise.)

3. I have learned from bicycles that a worn sprocket and a new chain will not run that well together. The reason is that the old chain has elongated to a longer pitch between chain links, and it will consequently wander out to form a larger radius on the sprocket to make the pitch fit, which will put excessive wear on the sprocket. This may not be a real problem on a rowing ergometer, but it just feels wrong for me to ignore my bicycle knowledge when replacing a chain.
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Re: Concept 2 Model D old vs. new difference in rowing

Postby froque » June 13th, 2018, 2:27 am

Hello

Personally I have both models but prefer the old D, perhaps the handle is more worn out and is easy on my hands, also foot stretchers are more comfortable in my opinion.

It is true that the new model D feels new, specially the flywheel noise is different, but you have to pay attention to notice it.

I have both models because we have a younger rower in the family we wanted to do training sessions together.

My recommendation is that you replace chain/sprocket/shock cord and also the rubber bearing cups for the axle.

New chain will not fit properly on a worn sprocket, will be noisier and might even skip under load ( cyclist know what it means)

Keep it clean (specially flywheel) , Concept 2 are very easy to service, and you can replace all internals for next to nothing.
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Re: Concept 2 Model D old vs. new difference in rowing

Postby Remo » June 13th, 2018, 8:00 pm

Carl Watts wrote: I picked up an older Model D from a gym that was free and lying on the floor in bits and rebuilt it, its now my preferred rower as for some reason it feels better than my newer one. The flywheel keeps spinning for much longer after I stop rowing on the early one for some reason, even on the same drag factor. There may be some subtle difference between the flywheels because I have done everything possible to make them the same.


There is more frictional (as opposed to aerodynamic) drag at low speeds. Aerodynamic drag drops off exponentially as the speed slows whereas frictional drag is constant. Anything that moves while coasting is a potential culprit including hub, freewheel/sprocket or a slightly wobbly flywheel or even that one flywheel is heavier or has slightly more weight on the outside of the disk
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Re: Concept 2 Model D old vs. new difference in rowing

Postby Carl Watts » June 13th, 2018, 10:05 pm

Remo wrote:
Carl Watts wrote: I picked up an older Model D from a gym that was free and lying on the floor in bits and rebuilt it, its now my preferred rower as for some reason it feels better than my newer one. The flywheel keeps spinning for much longer after I stop rowing on the early one for some reason, even on the same drag factor. There may be some subtle difference between the flywheels because I have done everything possible to make them the same.


There is more frictional (as opposed to aerodynamic) drag at low speeds. Aerodynamic drag drops off exponentially as the speed slows whereas frictional drag is constant. Anything that moves while coasting is a potential culprit including hub, freewheel/sprocket or a slightly wobbly flywheel or even that one flywheel is heavier or has slightly more weight on the outside of the disk


The only friction is the two shaft bearings in the flywheel and the one way in the flywheel which is in the release mode.

Replaced everything and its still the same.

Sure its hard to row a constant pace, stop and start a stopwatch but the difference is huge, like 1 minute of additional spin time on the older erg.

Doesn't really matter of course as the friction is just seen as drag as the flywheel slows but it was just something I tried to solve.

Obviously as the fan slows down significantly the bearings become more of a significant factor. The older model D fan on mine goes on forever, even my Model C is better than the late model D.
Most of the drag is aerodynamic as you say so there is probably a difference in the flywheels when it comes to the blades or pitch or something. They are two different part numbers from Concept 2 last time I checked.
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Re: Concept 2 Model D old vs. new difference in row

Postby jackarabit » June 14th, 2018, 11:48 am

Carl, you posted some time back about your late model D (2012 or after?) with very loose tolerances between the rubber shaft bearing bushings and the bearing hangers. Believe you estimated the potential runout at the left side bearing with the shaft under side loading during the drive as 2mm (observed by removing the black plastic dust cap and shifting the end nut with thumb and forefinger). I remember you commenting that you could see the shake in the flywheel with the right side of cage and exhaust band removed. Was the shake observed during the actual drive or with the flywheel coasting?

My 2012 D had alarmingly similar tolerances betweeen the I.D. of hangers and O.D. of bushings. I never noticed vibrations thru the handle under load but had noticed a point during (complete) deacceleration of the wheel when I felt a 3 or 4 beat vibration which I associated with the slowing wheel. I shimmed out the bushes to an easy slip fit in the hangers with a couple wraps of electrical tape and the brief node of flywheel vibration disappeared. The only other difference I could “see” was an observable light vibration of the monitor head which I had never noticed prior to shimming the mains. I also believe chain noise on the drive decreased but can’t be certain without putting a machine with slop side by side with one without.

I expect the OP has gone off to stare at schematics and order parts. For those who remain attentive to the possibilty of duping showroom performance in an old machine, there remain the questions of whether we can take for granted that new is synonymous with best and whether we understand why it’s best. Was the “loose” bearing fit and the shifting rotational axis of the driveshaft in some recent C2 machines an overall “best” operational arrangement as suggested by C2 Jon at the time of Carl’s thread? If so, those who, like Carl and myself, routinely swap out “eased” fits for precision have some thinking to do. A few moments devoted to jamming in severe service firearms, damping effects of banjo pot/tonering fit tolerances, and refusal of high end mechanical watches to run might be advisable. :lol:
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Re: Concept 2 Model D old vs. new difference in rowing

Postby Carl Watts » June 14th, 2018, 8:02 pm

With a perfectly balanced flywheel you can get away with the slop in the main shaft support bearings.

What happens on the drive is the whole flywheel pulls towards you and then moves back again with no noticeable effects to the user.

Problems happen with this settup when one of your flywheel weights come off. You would not believe how just 1.5 grams of weight makes such a difference.

With the older D with tight fit bearings the effect would be all direct vibration into the chassis. With a loose fit its both vibration and a VERY distinctive sound as the shaft thrashes around in the bearing holders as soon as you move into the recovery so you notice a problem immediately.No real damage, its just rubber bouncing about in the bearing mounts but it would cause me to cease rowing immediately as I'm kind of tuned into things mechanical that do not sound right.

The tight or loose bearing housing is not going to seriously effect the flywheel run down time. Very slight changes in the aerodynamics of the blades mounted on the flywheel wheel have a large effect.

I have not put the new flywheel on the old rower and vice versa, I really don't think it will make any difference, all the bearings were replaced and even a new shaft was tried on the new model D with no difference. I just found my curiosity getting the better of me and I guess it was a source of annoyance that the older totally thrashed ex-Gym Model D that was in bits appeared to be "Smoother" than my new version Model D from a few years ago that I purchased brand new.

Concept 2 would be able to confirm if there has been a subtle change to the nylon plastic molding of the blades.

If they say there has been no changes made at all then I need a new Hamster in my new model D because he is slacking off :lol:
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Re: Concept 2 Model D old vs. new difference in rowing

Postby Remo » June 14th, 2018, 9:31 pm

Carl Watts wrote:
Remo wrote:
Carl Watts wrote: I picked up an older Model D from a gym that was free and lying on the floor in bits and rebuilt it, its now my preferred rower as for some reason it feels better than my newer one. The flywheel keeps spinning for much longer after I stop rowing on the early one for some reason, even on the same drag factor. There may be some subtle difference between the flywheels because I have done everything possible to make them the same.


There is more frictional (as opposed to aerodynamic) drag at low speeds. Aerodynamic drag drops off exponentially as the speed slows whereas frictional drag is constant. Anything that moves while coasting is a potential culprit including hub, freewheel/sprocket or a slightly wobbly flywheel or even that one flywheel is heavier or has slightly more weight on the outside of the disk


The only friction is the two shaft bearings in the flywheel and the one way in the flywheel which is in the release mode.

Replaced everything and its still the same.

Sure its hard to row a constant pace, stop and start a stopwatch but the difference is huge, like 1 minute of additional spin time on the older erg.

Doesn't really matter of course as the friction is just seen as drag as the flywheel slows but it was just something I tried to solve.

Obviously as the fan slows down significantly the bearings become more of a significant factor. The older model D fan on mine goes on forever, even my Model C is better than the late model D.
Most of the drag is aerodynamic as you say so there is probably a difference in the flywheels when it comes to the blades or pitch or something. They are two different part numbers from Concept 2 last time I checked.


Most likely culprit, as you identify, is the flywheel. The one that spins longer should be the one with the larger "moment of inertia". To have a larger moment of inertia, the flywheel is either more massive, or it has more of its mass is distributed towards outside of the disk, or both.

https://en.wikipedia.org/wiki/Moment_of_inertia

To rule out a different alternative causation, try touching your hand to the outlet screen as the flywheel slows down. You will feel some vibrations, particular when the flywheel gets close to stopping. If you have significantly more vibration on the new Model D than the others, it would indicate that something is out of alignment or the flywheel is not properly balanced.
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Re: Concept 2 Model D old vs. new difference in rowing

Postby Dancer Don » June 15th, 2018, 5:12 am

I don't believe differences in moment of inertia are causing differences in spin time.

I think what matters for flywheel spin time is static balance. Dynamic balance may matter a little.

I had a Model C that had a flywheel that would spin a very long time before stopping. It has some rust issues so I bought a Model D, also with a long spin time and was getting ready to sell the Model C. My friend also had a Model C to sell, and asked me to sell it for her if I was successful in selling my Model C on craigslist.

I noticed my friends Model C had a flywheel that would spin for a noticeably shorter time. So I took the fan cover off and watched the flywheel as it spun down. I noticed that it would spin for a while, then stop, then reverse a little bit before stopping completely. This is the behavior of a flywheel that is out of static balance. The sprocket catching on the chain was causing the stop. I figured at some point I could remove the chain, in which case the flywheel should oscillate pendulum-like around a heavy point until it comes to a stop with the heavy side pointing down. Given time I was planning to play around with weighting the other side to see if I could get it back into static balance, and see if I could do this without messing up the dynamic balance too much.

My model C did not have a serial number, but I'm guessing it was older, and it's flywheel had only one weight on it, plus a rusty hub. My friend's model C was built in 1997, and it had more than 10 weights on it, and it had a hub that was painted to keep it from rusting. The painted hub made be think the 1997 C was more recent.

If I had to guess, I would say the flywheel with just one weight on it was static balanced only. It pulled very smooth, but since these flywheels spin at less than 1000 rpm, dynamic balance should not have as large an effect as static balance. Since the 1997 model C had many weights, I'm guessing it was static & dynamic balanced. Though I'm also guessing it was out of balance now, perhaps a weight had fallen off some time. The 1997 Model C did not vibrate or anything, but the older model C felt smoother, and had a flywheel that spun longer.

I did not get around to experimenting to balance the 1997 model C because my Model C sold on the same day, and I felt bad for another prospective buyer who just missed buying my C, so I offered the 1997 C to him, and that one sold the next day.
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