Egg chainrings, who remembers them?
- Thread starter mattbrown
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cyfa2809":1gofnqy2 said:
In comparison with round rings, and using the 'Feels Like The Back Wheel Is Slipping on Ice' (FLTBWISI) analogy, Biopace FLTBWISI through the power stroke, and properly oriented oval Eggrings FLTBWISI through the dead spot.
What properly oriented oval Eggrings actually do is maximise the the product of the torque which your legs can apply and the mechanical advantage provided by the chainring integrated over the full pedal stroke... integrated in the calculus sense, that is.
In doing this, they also whizz you through the dead spot as quickly as possible, thus meaning that power is applied to the rear wheel for more of the pedal stroke.
Biopace, on the other hand, whizzes you through the power stroke and drags through the dead spot
so with round rings you have to be on the power all the time i.e 'fast spinning' wheras with eggrings they give a bit of respite in between the harder part of the stroke and then utilise the full stroke to put as much power to the back end. i see! i see! 
one-eyed_jim
Old School Grand Master
The idea is that the cyclist can apply most force on the downstroke and very little at the top and bottom, so the effective gear (given by the radius of the chainring) should vary to match the force the cyclist can apply - a bigger gear where the leg is strong, and a smaller gear where the leg is weak. That evens out the torque around the pedal stroke, meaning less tendency for the wheels to spin or stall.
I've pinched a diagram (from Ed Burke's "Serious Cycling" - you can find more on Google Books) showing the forces applied to the pedal - that's for one leg only. On each complete turn of the pedals you get two power strokes of course, one for each leg.
More detail here:
http://www.analyticcycling.com/PedalFor ... _Page.html
I've pinched a diagram (from Ed Burke's "Serious Cycling" - you can find more on Google Books) showing the forces applied to the pedal - that's for one leg only. On each complete turn of the pedals you get two power strokes of course, one for each leg.
More detail here:
http://www.analyticcycling.com/PedalFor ... _Page.html
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As I said earlier in this thread, Though I have been riding off-road for over 25 years, I only started using EggRings a couple of months ago. I have recently revisited some of the local trails and hills that I have been riding for years in order to see what effect the EggRings actually have. I have also, from time to time, changed back to my 22 tooth round rings and then re-ridden a section of trail in order to make an accurate comparison.
.
The EggRings I am using are 45% elliptical, 24 teeth and 15 degree crank offset, (this is used to align the dead-spots with the minor axis of the ring).
My evaluation of the rings, is at present, subjective. But it should be possible to take timings and incline measurements and so quantify some of my findings:
*you can climb a steeper incline with a 24 tooth EggRing than a 22 tooth round ring. I rode up a hill that gets steeper and steeper as you climb. The conditions were dry, and the traction very good. The bike is a Cleland, with excellent, out of the saddle climbing characteristics.
With the round ring, at the same point on each attempt, the crank would refuse to go past the dead-spot, and so the bike would stall. However, the EggRing doesn't have have much of a dead-spot and always caried on all the way to the top of the hill. The difference in the in the climbable incline between the two rings was significant, and at some point in future I will measure it.
I have noticed that when climbing in the saddle on a long accent, that would normally leave me breathless, the EggRing left me with energy and breath to spare when I reached the top. It appears to be more efficient than a round ring. However, it is possible that one reason for this is that the EggRing may climb more slowly. So I need to take timings to check this out.
As the energy input at the pedals is the same regardless of ring shape, the
only difference is how the energy is delivered to the rear wheel and any losses caused by friction, and flexing components. The EggRing should in theory, produce smaller dynamic loadings to both frame and components.
Another major difference between round and elliptical rings is that the position of highest resistance to pedaling forces is found at a different leg positions. So a large round ring produces a long power stroke as you have to work hard to push the cranks away and towards the dead-spots. However, the resistance will ease through the middle of the power stroke. An EggRing will do the opposite. The optimum shape for a ring should be that which can extract the most power from the legs. Too elliptical and the power available pushing out of the dead-spot, would be wasted. In other words it is the power output of the human leg that will determine the optimum shape of chain ring.
This means that a 40% to 45% eliptical EggRing could speed not only speed through the dead-spot, but also the beginning and end of the powerstroke. Thus not utilise all of the legs available strength. This explains the common practice of making large rings less eliptical,
However, when it comes to extreme hill climbing, you need to get past the dead-spot, or there won't be a next power stroke to worry about.
.
The EggRings I am using are 45% elliptical, 24 teeth and 15 degree crank offset, (this is used to align the dead-spots with the minor axis of the ring).
My evaluation of the rings, is at present, subjective. But it should be possible to take timings and incline measurements and so quantify some of my findings:
*you can climb a steeper incline with a 24 tooth EggRing than a 22 tooth round ring. I rode up a hill that gets steeper and steeper as you climb. The conditions were dry, and the traction very good. The bike is a Cleland, with excellent, out of the saddle climbing characteristics.
With the round ring, at the same point on each attempt, the crank would refuse to go past the dead-spot, and so the bike would stall. However, the EggRing doesn't have have much of a dead-spot and always caried on all the way to the top of the hill. The difference in the in the climbable incline between the two rings was significant, and at some point in future I will measure it.
I have noticed that when climbing in the saddle on a long accent, that would normally leave me breathless, the EggRing left me with energy and breath to spare when I reached the top. It appears to be more efficient than a round ring. However, it is possible that one reason for this is that the EggRing may climb more slowly. So I need to take timings to check this out.
As the energy input at the pedals is the same regardless of ring shape, the
only difference is how the energy is delivered to the rear wheel and any losses caused by friction, and flexing components. The EggRing should in theory, produce smaller dynamic loadings to both frame and components.
Another major difference between round and elliptical rings is that the position of highest resistance to pedaling forces is found at a different leg positions. So a large round ring produces a long power stroke as you have to work hard to push the cranks away and towards the dead-spots. However, the resistance will ease through the middle of the power stroke. An EggRing will do the opposite. The optimum shape for a ring should be that which can extract the most power from the legs. Too elliptical and the power available pushing out of the dead-spot, would be wasted. In other words it is the power output of the human leg that will determine the optimum shape of chain ring.
This means that a 40% to 45% eliptical EggRing could speed not only speed through the dead-spot, but also the beginning and end of the powerstroke. Thus not utilise all of the legs available strength. This explains the common practice of making large rings less eliptical,
However, when it comes to extreme hill climbing, you need to get past the dead-spot, or there won't be a next power stroke to worry about.
one-eyed_jim
Old School Grand Master
I wrote:
Here's a picture I just found on my hard drive of the early model, showing the oval ring and several sets of mounting holes with instructions in English and French:
http://www.flickr.com/photos/24213822@N05/3976370843/
The extremes are labelled "no skidding" and "maxi force".
On reflection, I think I was confusing two different models of the 637: the earlier one with an oval granny ring and several sets of mounting holes to allow the orientation of the oval to be varied, and a later model with a plain, round inner ring and a single set of holes.
Here's a picture I just found on my hard drive of the early model, showing the oval ring and several sets of mounting holes with instructions in English and French:
http://www.flickr.com/photos/24213822@N05/3976370843/
The extremes are labelled "no skidding" and "maxi force".
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one-eyed_jim wrote:
The "no skidding" is the EggRing orientation, with less force and more speed delivered to the rear wheel on the powerstroke.
The "maxi force" the Biopace orientation, with more force and less speed sent to the rear wheel during the powerstroke. Of course a smaller round ring would produce even more force.
The granny-ring only looks to be about 10-15% ovality. A major question with eliptical rings is how eliptical? What ratio is best to achieve a chosen advantage, be it speed, efficiency or traction control.
The "no skidding" is the EggRing orientation, with less force and more speed delivered to the rear wheel on the powerstroke.
The "maxi force" the Biopace orientation, with more force and less speed sent to the rear wheel during the powerstroke. Of course a smaller round ring would produce even more force.
The granny-ring only looks to be about 10-15% ovality. A major question with eliptical rings is how eliptical? What ratio is best to achieve a chosen advantage, be it speed, efficiency or traction control.
GrahamJohnWallace":27tpd9dv 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:
I could be wrong, just saying what I see.
