Egg chainrings, who remembers them?

[GrahamJohnWallace]

DoctorRad said:
It looks the other way around to me. Set on 'No skidding' as it is, and looking at how much the inner ring teeth are overlapping the five 110 BCD bolts, I'd say that the ring was orientated with its long axis almost parallel to the crank arm. This is the opposite of EggRing orientation:

That's an interesting point DoctorRad.

As you point out, the photo of the chainset shows the inner ring in Biopace mode. The "maxi force" or maximum leverage position.

The question is what do the instructions say?
If they say "align the arrow to the crank", as DoctorRad is presuming, they do not make sence.

If they say "align the arrow at 90 degrees to the crank." The terms
"no skidding" and "maxi force" do match the relative leverages (mechanical advantages) being applied to the rear wheel during the power stroke.

 

[GrahamJohnWallace]

"If you're not confused you don't understand the question".

For the mechanically uninitiated I thought It would be a good idea to explain
some of the basic science involved.

Power= work done + time taken(measured in watts)
This is produced by the legs and enters the bicycle via the pedals (input). The legs are more efficient, powerful or faster at producing certain kinds of movements than others. (try cycling with a very low saddle)

Force (torque is rotational force)
Is a component of power. The other component is time as a given amount of power can be applied over different lengths of time.

Efficiency = the ratio of power input to power output
Power, cannot be created and destroyed but it can change form into noise, heat, light etc. The more power lost by a mechanism, the less efficient it is. Efficiency can be seen either power into speed or power into distance. So an efficient bike would either go faster, or for longer on a given amount of power.

LEVERAGE
Power cannot be created or destroyed but it can be changed. A large slow moving force can be converted into a smaller faster moving force. This is what bicycle gearing systems do.
Leverage is made up from:
Mechanical Advantage
The ratio of the input force of a mechanism to its output force.
and
Velocity Ratio
Is the s the ratio of the input speed of a mechanism to its output speed.

Mechanical Advantage and Velocity Ratio are relative. Increases in force are made at the expense of speed and vice versa.

So the question is: given the nature of the power output of the human leg, and the fact that cranks have inefficient dead-spots, can non-round chainrings improve the efficiency of the output to the rear wheel in a given riding situation?

The situation is crucial. What is efficient for a 1 in 3 hill climb may be inefficient on the flat.

There are ways to find answers:
1/ Mathematically, from analysing biomechanical data (input) and modeling the ways that mechanisms process the forces to create an output. (the problem here is calculating the systems losses)
2/ Exhaustive and expensive real world testing and measuring.

These methods are most effective if used together.

Does anyone know of existing research?

 

[DoctorRad]

That's an interesting point DoctorRad.

As you point out, the photo of the chainset shows the inner ring in Biopace mode. The "maxi force" or maximum leverage position.

The question is what do the instructions say?
If they say "align the arrow to the crank", as DoctorRad is presuming, they do not make sence.

If they say "align the arrow at 90 degrees to the crank." The terms
"no skidding" and "maxi force" do match the relative leverages (mechanical advantages) being applied to the rear wheel during the power stroke.

The instructions say "arrow's [sic] top in line with the pedal". You can read this pretty clearly on the full resolution photo.

 

[GrahamJohnWallace]

My interpretation of the terms "anti-skid" and "maxi-force", are as follows:

"anti-skid" (reduced leverage, less mechanical advantage over the wheel during the power-stroke"). As the input pedal cannot skid the term must refer to the output wheel not the input of the pedal.

"maxi force" (applying the maximum force or mechanical advantage to the rear wheel during the power stroke). They could have correctly used the term "maxi speed" instead.

Either the terms they are using are poorly worded and unscientific. Or they have simply made a mistake and got them back to front.

The only other way I can make any sense of their phrases is by considering the reaction forces felt by a cyclists legs. These will be equal and opposite (Newton's third law of motion) to the output force at the rear wheel. However in science reaction forces are the result of a forces being constrained and are not real forces in themselves.

 

[kaiser]

What a smashing thread I've been intrigued by these for a while. At the moment I'm using a biopace ring on a single speed though I have moved the orientation 1 bolt hole to partially recreate what has been spoken of. I picked this up from a time trialler so I'm pretty sure theres a lot of reaserch in that field too.


You could also have a look at rotor q rings, there sites pretty good and they also have a stab at a crank idea.

 

[kaiser]

FWIW I've noticed a lumpy performance at high revs, for instance when travelling on tarmac but in trail conditions and especially climbing there is a noticable difference.

 

[GrahamJohnWallace]

kaiser said:

You could also have a look at rotor q rings, there sites pretty good and they also have a stab at a crank idea.

Rotor Q Rings are the same orientation as EggRings and have patented fitting holes that allow the crank offset to be adjusted.

They only offer one size of ovality but don't appear to specify what this is.

Moving crank solutions designed to overcome the deadspot have been around for some time. My worry is that in the past these mechanisms have been complex and mechanically inefficient.

 

[GeoffApps]

I've got some of these in my recently acquired box of bits. I think i will give them a try- i'm a pusher rather than a spinner so they may be a benefit

Hey, Lewis, have you given them a try yet? Any conclusions?

On the matter of EggRing durability; the larger ring (behind the bash ring) is now over twenty years old, it was first fitted to the Clelandale (see Cleland website: www.Cleland-Cycles.co.uk) in 1989.

 

[DoctorRad]

I just got some Sakae Ovaltech rings from a chap here to have a play with. They're obviously not exactly elliptical, but they're about the equivalent of 8% ovality by Chris Bell's measure. That's not really very oval at all. The default orientation is wrong too I think, but you can get them pretty close by rotating them one hole anti-clockwise.

Will definitely put them on something, probably my mooted grocery / pub bike with a 13-34 cassette or something equally silly. That frame is meant to be my Xtracycle donor frame when I have the funds, I think they'd be cool for luggage duties.

I read the other day that Shimano have bought or licensed the Q-Ring patent and were planning to introduce them on the Dura-Ace groupset. Anyone know any more?

 

[GrahamJohnWallace]

So the question is: given the nature of the power output of the human leg, and the fact that cranks have inefficient dead-spots, can non-round chainrings improve the efficiency of the output to the rear wheel in a given riding situation?

I have now been using 45% elliptical EggRings for four months. The effect they have when cycling in easygoing flat conditions is minimal. However the greater the resistance to pedaling, be it from an incline, headwind or softground, the more marked the improvement in efficiency over round rings.

Quite simply, with round rings you get more acceleration through the power-stroke, but more time to lose the benefit of this during the dead-spot.

With EggRings, you get less acceleration during the longer power stroke but less time to lose any gain throughout the much shorter dead-spot.

Don,t expect that the EggRings will make you go faster though, you will just expend less energy covering the terrain.
Because of this:
*you may well be able to ride for longer between rest breaks.
*you will find is that you will get to the top of hills, that would normally
leave you exhausted, and still have energy to spare.
*previously exhausting steep inclines and deep mud sections, can now become ridable.

This efficiency gain is most noticeable at lower pedaling cadences.