Qrings

[jeebus]

Quote:
We really need some simple language around this. May I propose the following:

1) Angle Between Bottom Dead Centre and the Chain Tangent Point at the Ellipse Major Axis. Lets call this the Tangent Angle

2) Desired Angle Between Crank and Chain Tangent Point at the Ellipse Major Axis. Lets call this the Power Angle

To set up the rings, calculate the Retard Angle, which is 1) - 2). The Retard Angle tells you how far behind the cranks you should place the major axis of the ellipse.

Are you sure angle #2 shouldn't say "desired angle between bottom dead center and the crank when the ellipse major axis is at the chain tangent point"? The way angle #2 is described above I think it is the 91.6 angle from your original diagram, where it sounded like you meant for 1)-2) to be that 91.6. Also what does bottom dead center mean? Using my definition for #2 it doesn't really matter, it just needs to be a common point from which to measure the angles, but I want to be consistent.

My other remaining question regards the chain tangent point. The rotor instructions have us mark the rings at a point where
"the first tooth-through that fully engages the roller of the chain at the top of the Q-Ring (the side that pulls the chain)". I always had trouble deciding exactly where that point was, but I didn't end up selecting the tangent point where the chain and a radial line through the q-ring made a right angle.

You can tell in my photo, where I sort of followed the convention you described, putting the ellipse's major axis where it looked to me like it was engaging, but isn't quite on a tangent with the chain.

- Mark

 

[WhiteSilvio]

Question:
When using an elliptical chain ring and the tension chain line is tangential to the MAJOR axis of the ellipse, does one want the maximum amount of torque available (90deg. before BDC) (during the leg drive cycle), or the minimum (BDC)?

John R.

 

[John Tolhurst]

You want maximum, but that is not at 90 degrees, it is further round at about 135 for some reason. This is the insight that Rotor used to design the q-ring product.

 

[WhiteSilvio]

Okay.

So the angle between the ellipse MAJOR axis at the tension chain tangent point and the RH crank arm is going to be somewhere close to zero deg., to utilize the maximum "leg drive" torque available.(?)

Comment: I suppose that the developed torque maximum at 135deg. has something to do with that article you linked to showing all the different muscle groups at work; not really the kind of thing that mere mortals without the laboratory facilities can even guess at, although with some of the pressure/force applied to the pedal devices around one could attempt to confirm this type of finding.

And if the maximum leg force/torque available is 135deg before BDC, does that mean that the "torque cycle" isn't simple harmonic motion (SHM), but is in fact skewed back 45deg?

Is minimum leg force/torque developed at BDC?

 

[John Tolhurst]

You want the chain at the max radius when the leg is 3/4 through its stroke, not 1/4 through

 

[WhiteSilvio]

Alright, I misunderstood that. So the maximum force is generated at 3/4 stroke.

So it is that the RH crank leads the MAJOR axis by 90deg., approximately. This is assuming, somewhat simplistically, that the BDC position of the crank is in a plane parallel to the wheel centres and that the angle of the chainline (Major axis tangent point) is at around 45deg. clockwise to the perpendicular of the wheel centres line. Obviously both of these are actually variable, within a narrowish range.

Then if the system is set up this way the BDC and the MINOR axis tangential chainline point will not coincide. Does this matter?

Without considering the matter at great length, I could reach the conclusion that the elliptical chain ring should not be symmetrical, but have the major and minor axes inclined at approximately 45deg. to one another to take advantage of the power delivery of the human leg. (Does this translate correctly for the LH crank??) What do others think?

John R.

 

[Mark B]

WhiteSilvio wrote: What do others think?

John R.

I think you guys are making my brain hurt. Right now, I'd rather power a (round) 42 tooth chainring and a 13 tooth cog up a six percent grade than try to make sense of what you fellers are talking about. :roll: :lol: :lol:

Mark

 

[WhiteSilvio]

Quote: a (round) 42 tooth chainring

Mark,
Is that an African 42 tooth chainring or a European 42 tooth chainring? And what exactly is your favourite colour (favorite color)?

John R.

 

[Mark B]

WhiteSilvio wrote:

Quote: a (round) 42 tooth chainring

Mark,
Is that an African 42 tooth chainring or a European 42 tooth chainring? And what exactly is your favourite colour (favorite color)?

John R.

Actually, I believe it's Japanese, though I also have an Italian...

Turdmurkley orchid,though blue runs a close second.

Mark

 

[Traqr]

WhiteSilvio wrote: Alright, I misunderstood that. So the maximum force is generated at 3/4 stroke.

So it is that the RH crank leads the MAJOR axis by 90deg., approximately. This is assuming, somewhat simplistically, that the BDC position of the crank is in a plane parallel to the wheel centres and that the angle of the chainline (Major axis tangent point) is at around 45deg. clockwise to the perpendicular of the wheel centres line. Obviously both of these are actually variable, within a narrowish range.

Then if the system is set up this way the BDC and the MINOR axis tangential chainline point will not coincide. Does this matter?

Without considering the matter at great length, I could reach the conclusion that the elliptical chain ring should not be symmetrical, but have the major and minor axes inclined at approximately 45deg. to one another to take advantage of the power delivery of the human leg. (Does this translate correctly for the LH crank??) What do others think?

John R.

Has anyone confirmed that Qrings are truly elliptical, and haven't taken this possibility into account? Cam mechanics would allow an unlimited number of configurations, and the "perfect" shape would depend on both pedalling style and leg proportions (all variables from your hip to the part of your foot over the pedal axle). It's no wonder we're encouraged to learn to spin round rings, which brings me to a question to those of you trying Qrings; have you trained yourselves to spin a regular drivetrain smoothly (as in Pro-Racer style), and now you're seeing improvements in efficiency with "lumpy" rings, or are you mashers like me and these rings better match your natural stroke?

 

[WhiteSilvio]

Rotor Cranks USA http://www.rotorusa.com/i1-q-rings.shtml refer to ovalized and elliptical as descriptions of their Q-rings product.

I cannot personally verify this as I do not own Q-rings to measure them, but I am prepared to accept the product information put out by Rotor Cranks USA. (Possibly not a good idea. )

The main point is that they have Major and Minor axes at 90degrees to one another, and at these points the variation in the equivalent number of teeth, that would be found on a round chainring, is around 10%. In the example drawing http://www.rotorusa.com/images/qringsphase.gif the variation in equivalent teeth is 51T to 56T. There is a progressive change between the two points.

Although there would an infinite number of ways of getting between these two points, the reality is that with the limited variation in equivalent teeth numbers that is possible between the high and low points, due to practical considerations, there is only a fairly limited range for the actual shape and path of the resultant elliptical sprocket.

One problem seems to be setting up the Q-rings to take advantage of any benefit(s) they may have.

John R

 

[John Tolhurst]

If each leg is to get the same treatment, the rings must have rotational symmetry of 180 degrees. The q rings are ellipses of where the major axis is 10% (as I recall) more than the minor axis.

 

[Traqr]

WhiteSilvio wrote: Rotor Cranks USA http://www.rotorusa.com/i1-q-rings.shtml refer to ovalized and elliptical as descriptions of their Q-rings product.

I cannot personally verify this as I do not own Q-rings to measure them, but I am prepared to accept the product information put out by Rotor Cranks USA. (Possibly not a good idea. )

The main point is that they have Major and Minor axes at 90degrees to one another, and at these points the variation in the equivalent number of teeth, that would be found on a round chainring, is around 10%. In the example drawing http://www.rotorusa.com/images/qringsphase.gif the variation in equivalent teeth is 51T to 56T. There is a progressive change between the two points.

Aha! I'd missed that they stated the axes were at 90°; so they haven't adjusted for the fact that maximum stroke force comes only 45° before BDC.

WhiteSilvio wrote: Although there would an infinite number of ways of getting between these two points, the reality is that with the limited variation in equivalent teeth numbers that is possible between the high and low points, due to practical considerations, there is only a fairly limited range for the actual shape and path of the resultant elliptical sprocket.

Not so! Even assuming that 10% is the maximum useful variation in ratio, we still have a range of angles between the two axes, and a wide range of possible shapes that the rings could take (Is ellipsoidal best? Why not a constant-rate change in radius? Or an accelerating curve?)

WhiteSilvio wrote: One problem seems to be setting up the Q-rings to take advantage of any benefit(s) they may have.

John R

Especially since such fundamental changes to the way your machine interacts with your body will require time to relearn your cadence; how many people will allow the couple of weeks between changes and log the performance difference of each configuration to determine which is biomechanically most efficient? Any Cruzbike rider will be familiar with retraining muscles to adapt to a different machine ;-).This sounds like a Master's research paper in the making... And at the end of it all, how much performance are we anticipating? 2% seems optimistic to me, so I wonder if all this time & effort would be better spent on designing a functional tailbox that would give us more aerodynamic improvement than this product promises...

 

[WhiteSilvio]

Quote: And at the end of it all, how much performance are we anticipating? 2% seems optimistic to me, so I wonder if all this time & effort would be better spent on designing a functional tailbox that would give us more aerodynamic improvement than this product promises...

Having delved into this Qring thing, I have to say that I agree that there are probably more productive areas for getting extra performance out of a Silvio, and probably most bikes. Speaking personally, IMHO, and all that sort of thing, I don't really see the advantage in the Qrings, but having read some of the other bike forums out there, there are certainly plenty of people who "wouldn't be without them".

So who am I to say they're wrong? If people perceive some difference all well and good.

The full blown Rotor cranks could offer some benefit in reducing the effect of the dead spots.

I have some ideas for making use of the most useful part of the power stroke, by going from a rotary system drivetrain to some sort of oscillating system. I'm sure someone will have made one somewhere. This has the potential to deliver 3 or 4 "power pulses" per equivalent revolution and greatly reduce the "dead spots".

Unfortunately I don't have the resources available to build such a drivetrain to find out if this is practical or not.

In the meantime I've been having some thoughts as to tailboxes.

John R.

 

[Mark B]

WhiteSilvio wrote:

Quote: And at the end of it all, how much performance are we anticipating? 2% seems optimistic to me, so I wonder if all this time & effort would be better spent on designing a functional tailbox that would give us more aerodynamic improvement than this product promises...

Having delved into this Qring thing, I have to say that I agree that there are probably more productive areas for getting extra performance out of a Silvio, and probably most bikes. Speaking personally, IMHO, and all that sort of thing, I don't really see the advantage in the Qrings, but having read some of the other bike forums out there, there are certainly plenty of people who "wouldn't be without them".

So who am I to say they're wrong? If people perceive some difference all well and good.

The full blown Rotor cranks could offer some benefit in reducing the effect of the dead spots.

I have some ideas for making use of the most useful part of the power stroke, by going from a rotary system drivetrain to some sort of oscillating system. I'm sure someone will have made one somewhere. This has the potential to deliver 3 or 4 "power pulses" per equivalent revolution and greatly reduce the "dead spots".

Unfortunately I don't have the resources available to build such a drivetrain to find out if this is practical or not.

In the meantime I've been having some thoughts as to tailboxes.

John R.

I think the answer lies in nano technology.

Mark

 

[Peder Torgersen]

Mark B wrote:

WhiteSilvio wrote:

Quote: And at the end of it all, how much performance are we anticipating? 2% seems optimistic to me, so I wonder if all this time & effort would be better spent on designing a functional tailbox that would give us more aerodynamic improvement than this product promises...

I think the answer lies in nano technology.

Mark

Mark does have a point the professor in this story was able to ride at a top speed of 85.5 miles on a Rans Stratus! Just think what speed he would be capable on a Silvio with a tailbox and a front fairing?

Peder