Concept2 Forum

Posted: **December 30th, 2008, 9:42 pm**

Hi, I am curious to know what the advantages are of adding a speedring to a model B.

It obviously blocks part of the airflow to the fan and makes rowing lighter, are there any other advantages?

My model B is completely standard, so far I've only replaced the rollers and the shock cord.

Simon

Posted: **December 30th, 2008, 10:30 pm**

John Rupp wrote:You're welcome, and you can make one easily enough.

For more accuracy poke holes through a stick at 0, 7 and 9 inches,
put a nail through 0 and a pen refill through 7 and 9, then cut 2 semi circles.

Attach them with plastic ties and that's it.

You can use black roofing paper, or cardboard, or just tape a towel to the side and then you don't need to cut anything.
However, I liked the black roofing paper the best.

Posted: **December 31st, 2008, 6:05 am**

I remember seeing pictures of the infamous John Rupp model B when it went up for sale, and it had the roofing paper on top of the cage as well.

Is that also done to improve the range of resistance?

Posted: **December 31st, 2008, 1:29 pm**

Thanks for remembering.

Yes, the cover on top was to modulate the range of resistance, assist in
reducing the sound, and to help keep the air flow from going directly towards me.

Posted: **January 1st, 2009, 6:03 am**

Thanks, ill contact concept 2 in my neck of the woods to check if the speed ring is available.
On the B parts order form from the US concept 2 site it's listed so hopefully I can get get it here [holland] as well.

Thanks again and all the best for 2009.

Posted: **January 1st, 2009, 1:46 pm**

You're welcome, and you can make one easily enough.

For more accuracy poke holes through a stick at 0, 7 and 9 inches,
put a nail through 0 and a pen refill through 7 and 9, then cut 2 semi circles.

Attach them with plastic ties and that's it.

You can use black roofing paper, or cardboard, or just tape a towel to the side and then you don't need to cut anything.
However, I liked the black roofing paper the best.

Posted: **February 24th, 2009, 11:36 pm**

Nice to see so much traffic in the forums about Model B.

I started looking at the whole 'drag factor' thing again recently because of a comment on our cyber-team newsletter.

My model B with PM3
..damper full open, drag factor 224
..damper full closed, drag factor 177.
This seems to be comparable to what others have reported for B models.

I made a speedring (14.5 to 18.5 inch diameters) from corrugated plastic board, and measured
..damper full open, drag factor 210
..damper full closed, drag factor 112.

Wife looked over from her Schwinn 205 recumbent bicycle and asked what I was doing. She said, "I never did like your machine because it was too hard to pull."

I threw an old towel over the whole flywheel cage and measured the drag factor: 51.

Wife tried it and said, "You'll have to share this one with me, now."

Fine with me.

Posted: **February 25th, 2009, 9:07 am**

I'm having a hard time understanding the topic. Can someone please post a picture?

Posted: **February 25th, 2009, 1:32 pm**

(found at another thread)
http://www.flickr.com/photos/26916409@N00/3240043522/

The 'speedring' is only appropriate for the Model B, where the flywheel cage is made of wire, resembling a floor fan cage, rather than perforated sheeting. The wire cage admits much more air than the cage of perforated material found on later models.

Restricting air flow to fan >> less air for fan to act on >> less momentum and energy transferred from fan to air >> less felt resistance in power stroke and less flywheel speed drop during recovery stroke. Therefore a softer and smoother feeling row.

C2 seems to have wanted to lighten up the stroke, so they went to the perforated screen cage after the Model B. To lighten up the Model B stroke, more shrouding of the fan is needed than just the damper will provide.

Posted: **February 25th, 2009, 1:33 pm**

djh wrote:I'm having a hard time understanding the topic. Can someone please post a picture?

The cage of the model B is made of heavy wire, so that it is mostly open space and allows a much greater flow of air than the cages of the later models, which are mostly enclosed. The discussion is about various ways to block off that air flow to make the resistance comparable to the later models. One other point is that the model Bs came the first electronic performance monitor (just PM, with no number) and did not have the capacity to show the drag factor. It is common practice to refit a model B with a later PM that does have this capacity.

Sorry — could not find a picture of a model B without a more thorough search than I wanted to bother with.

Bob S.

edit added: Whoops, it looks like I was a bit slow getting this one in. The previous post covered it quite well.

Posted: **February 25th, 2009, 1:35 pm**

shu246 wrote: C2 seems to have wanted to lighten up the stroke, so they went to the perforated screen cage after the Model B. To lighten up the Model B stroke, more shrouding of the fan is needed than just the damper will provide.

It also made it far, far safer, especially if there were young children around.

Bob S.

Posted: **February 25th, 2009, 1:47 pm**

Bob S. wrote:
It also made it far, far safer, especially if there were young children around.

Yeah, that too. I got the fan going at a good speed and stuck a pencil into the impeller blades. The grandkids were suitably impressed and kept their distance after that.

Concept2 Forum

Advantages of having a speed ring on a model B

Advantages of having a speed ring on a model B