how to lower drag factor

[jkalmes]

Hi All, I have a Model B with a new PM2 monitor.. I have posted before with the drag readings I get, 180 with damper closed, 215 with damper half open and 240 with damper 100% open. I can not get a lower drag than 180! Everything appears to be clean and operating correctly, I have used a Model D rower and have rowed at 140 drag and it's quite noticeable, so I can feel the difference. What else can I do?

[johnlvs2run]

Hi All, I have a Model B with a new PM2 monitor.. I have posted before with the drag readings I get, 180 with damper closed, 215 with damper half open and 240 with damper 100% open. I can not get a lower drag than 180! Everything appears to be clean and operating correctly, I have used a Model D rower and have rowed at 140 drag and it's quite noticeable, so I can feel the difference. What else can I do?

A 180 drag factor on a modelB is the same resistance as a 146 drag factor on a modelD due to the different number of teeth on the cogwheels.

15x15x15 = 3375
14x14x14 = 2744
3375 / 2744 = 1.23
180 / 1.23 = 146

You can easily make a speed ring from black roofing paper or similar material, and attach this with plastic ties to the fan side of the erg.
This will quite effectively reduce the resistance.

[jkalmes]

thank you John. I wasn't sure if the reading was accurate because it is high, and after reading quite a few posts, it seems like I should be at a lower drag. I will cover the fan side of erg and post the difference. Thanks again

[Bob S.]

thank you John. I wasn't sure if the reading was accurate because it is high, and after reading quite a few posts, it seems like I should be at a lower drag. I will cover the fan side of erg and post the difference. Thanks again

I am not sure what you mean by the fan side of the erg. If you mean the side of the fan, i.e. where the damper is mounted, a cover will be effective only if it extends beyond the diameter of the damper. In other words, it would have to cover the open part of the cage. It is even more effective if you use a cover around the periphery of the cage. When I had a model B with a PM3, I could get the DF down below 50 by enclosing the entire erg fan cage with a conveniently shaped cardboard box. (It happened to be a box that a large rectangular floor fan came in.) I didn't use it this way for workouts. I was just fooling around to so how effective it would be. I had the B with the old PM(1) for a long time, so I was used to working out at high drag factors. I wasn't even aware of the concept of drag factors until I installed the PM3 on the model B. After I replaced it with a Model D, I got used to working out at much lower drag factors, usually between 115 and 125.

The major reason that the Bs have such large drag factors is that they have the open wire cages. The cages of the later models are much more effective in blocking the air flow even with the damper wide open. With those models, the upper limit of the drag factor is just a bit over 200. To go higher, it would be necessary to remove part of the cage, like the perforated metal band around the perimeter.

Bob S.

[jkalmes]

Thanks Bob, I had read a post a while back about covering the cage, couldn't find it again so I asked about it again. Yes I was going to cover the damper side of the cage and around the perimeter. I went online and looked at a C Breeze, not sure if it's for a model b though, I am sure I can construct a cover for the cage. Thanks again, Jeff

[johnlvs2run]

The fan side of the erg, is the side of the erg that the fan is on.
On the modelB, this side of the erg is mostly open and has a free flow of air.
Using a speed ring on this side should result in a major reduction in resistance.

A cover extending beyond the diameter of the cage would have almost NO effect on resistance.
Covering the perimeter would make a slight reduction of resistance in addition to having the speed ring.
You could also cover the perimeter only partitially, so as to direct the air flow where you wish.

My usual drag factor range on the modelB was 65 to 170, with speed ring on the side, narrow perimeter cover,
and space in between them. This was with a model C/D 14 tooth cogwheel.
I easily took the drag factor below 45 but the resistance was too light.
My first marathon (2:58) was with a drag factor of 77 and model C cogwheel.
You can basically get the resistance as low as you wish.

Recently I've posted about getting a max drag factor of 360 by removing the perimeter mesh from a D.
You can do a search and find my other posts through the years about covering the modelB and some photos.

[c2jonw]

Virtually any interference of the air flow, whether on the inlet (fan side) or outlet (perimeter) will result in lower drag factors on all C2 Rowers. Cardboard, duct tape, roofing paper, shrink wrap will all work. Generally just make sure that whatever you use is secured well so it doesn't become a missle in the middle of your workout!
The Model B speed ring that covers the remainder of the inlet side that the damper does not cover was designed to be a simple add-on that brought the drag factor down into an acceptable range primarily for sweep rowing coaches. Admittedly we "overpowered" the Model B and made adjustments in the C to bring the DF into a lower range. C2JonW

[Bob S.]

Generally just make sure that whatever you use is secured well so it doesn't become a missle in the middle of your workout!
C2JonW

That is a possibility as well, but the main problem is that, if part of the covering comes loose, the drag factor would be changed in the middle of the workout.

Bob S.

[jkalmes]

just an update on the DF readings, I covered the top of the erg with cardboard and duct tape, left both sides alone. Now the drag readings are:

90 with damper closed

130 with damper 1/2 open

160 with damper 100% open

what a big difference!! The lowest I'd ever rowed with was 180 and to row today with all the different options was fun. Now it's time to work on the form and get my times down.

[johnlvs2run]

Be sure to account for cogs when calculating the drag.

The drag factor doesn't change with different cogwheels but the resistance does.

Thus your 90 DF is actually either 73 or 112 compared to an erg with a 14 tooth cogwheel.

[jkalmes]

John, I'm not sure if I understand completely, where should I be as far as drag factor using the 15 cog. I was planning on rowing with a reading of about 130 and then move it around to get a different feel every once in a while.

Does rowing at different DFs change the distance of your row, or just difficulty of the row?

[johnlvs2run]

Does rowing at different DFs change the distance of your row, or just difficulty of the row?

The drag factor just changes the feel of your row.
You should be able to do about the same paces either way.

Drag factors are the same regardless if you're using the 13 or 15 tooth cogwheel,
but the resistances are entirely different, based on the cube of the number of cogs.

15x15x15 = 3375
14x14x14 = 2744
3375 / 2744 = 1.23

The 15 tooth cog has the lightest resistance and the # can be adjusted to modelC 14 tooth resistance.
90 / 1.23 = 73 drag factor resistance with 14 tooth cogwheel

A 130 modelC resistance is calculated as follows.
130 x 1.23 = 160 with 15 tooth cogwheel

[c2jonw]

I should have posted this link earlier: http://www.concept2.com/us/support/manu ... arison.pdf
Be sure to read the notes at the bottom.......C2JonW

[Cyclist2]

C2JonW; I have a home-made speed ring on my model B that reduces the drag factor to 122 when the damper is fully closed. Where can I find the speed ring that you mention in your comparison? I don't see it on the C2 shopping site. Thanks!

[c2jonw]

Sorry to say we stopped offering those many years ago. Your home made ring probably works just as well as the part we offered as long as it's reasonably stiff and is firmly attached. C2JonW