[TrueScotsman]

Okay, I re-did the "power-ellipses"/ABChainring comparison. Remember this drawing has no specific sizes, it just shows the type of shape and more importantly the orientations. Unfortunately, as can be seen from the sketch the drawings do not line up as well as I previously had figured;

The "power-ellipses" are the shape that would be required to even out the power output of pedalling- giving less leverage when you have most force in your legs and more leverage during the "dead-stroke".

Vrock- Cheers for the help, but even if I could design a ABChainring to even out bob there would be no point if it were a nightmare to pedal. I'll have to look at this further, but for now I have to go back to work!

 

[no skid marks]

Okay, I re-did the "power-ellipses"/ABChainring comparison. Remember this drawing has no specific sizes, it just shows the type of shape and more importantly the orientations. Unfortunately, as can be seen from the sketch the drawings do not line up as well as I previously had figured;

So isn't it pretty much the same as Shimanos first wrong bio pace? Why not just try an old one of them? At least to see if it roughly works.

 

[TrueScotsman]

I've been looking at and checking my graphs/drawings and unfortunately I don't think it is possible to have an ABChainring that works to control anti-squat AND pedals well.
The problem is that where you need a larger chainring to lower A-S happens in your "deadspot"- where you need the extra leverage of a smaller chainring, and vice-versa. Damm!
(I will, however, still keep looking at ways to achieve it.)

Unless anyone else has any bright ideas?

 

[syadasti]

I don't think it will help you I was thinking of the strange shifting/expanding front chainring design on the old Yankee bike (my father had one years ago). Wonder if you could get it to change shape and size on the fly:

Would also be nice for making a 1x9/10 setup that would yield ratios just as wide or wider than a triple. (notes 9 ratios via the front gear)

More on the Yankee:

http://ustimes.com/Bicycle/PageTwo.html

 

[fluider]

The problem is that where you need a larger chainring to lower A-S happens in your "deadspot"- where you need the extra leverage of a smaller chainring, and vice-versa. Damm!

Excuse me Sir, but I can't understand this , perhaps commas dividing partial sentences could help me.

 

[TrueScotsman]

No problem dear fellow!

At a certain point in the crank rotation you get maximum vertical pedal force (bob). To counteract this you need extra Anti-Squat- this means a smaller chainring. Unfortunately, this also happens to be close to your where your maximum pedal torque is, which would require a larger chainring.
The two desired effects are opposite each other. You could have a chainring that resisted bob but it would be hard to pedal in the "deadspots" (around 12 to 1 o'clock) and too easy to pedal in your power stroke (3 to 5 o'clock).

In other words- "I made a balls-up!"

Anyway, this is what I am thinking at the moment, I will go and have another look at it.

 

[davec113]

I've been looking at and checking my graphs/drawings and unfortunately I don't think it is possible to have an ABChainring that works to control anti-squat AND pedals well.
The problem is that where you need a larger chainring to lower A-S happens in your "deadspot"- where you need the extra leverage of a smaller chainring, and vice-versa. Damm!
(I will, however, still keep looking at ways to achieve it.)

Unless anyone else has any bright ideas?

That's what I was pointing out in my last post, but it's also true your graph was off 180 degrees... I actually didn't catch that!

Apparently you need to design a frame with a sus that will work with the ABCR.

 

[TrueScotsman]

Thanks davec113- it was all going great till you pointed out my mistake!

Also, I don't think the graph is 180* out- it's just that the vertical pedal force is on a decreasing scale- because vertical load is downwards.

Anyway, for my next bright idea- Square Wheels! for even-ing out the whoops/regular rock gardens! ;